**Author details**

#### Joern Schmitt

An interesting, newly developed approach of device coatings seems to be able to control local bacterial growth and thus is supposed to be able to prevent system infections [28, 29]. The study by Matl et al. describes the use of gentamycin and teicoplanin in a lipidbased drug delivery-system which was able to deliver high local concentrations over 96h and inhibit completely the growth of S. aureaus in vivo [28]. Wong et al. published data on a dual layer device coating, consisting of gentamycin to control local colonization/ infection and diclofenac to control local inflammation due to tissue injury on top of a mi‐ crobicidal base film [29]. In vitro they could show excellent results in terms of S. aureus control (figure 1). No data on extended in vivo use of any coating is yet available but

**Figure 1.** Media-borne assay with *S. aureus* with increasing time of incubation in bacterial solution; top row shows bare substrates completely colonized by bacteria (light beige colored dots); bottom row shows (DMLPEI/PAA)10 films with degradable top films completely eroded with no sign of colonization by bacteria (black colored substrate). From

Concerning the severe consequences arising from an infected implanted pacemaker or defibrillator and the data available there should be no discussion on the use of preven‐ tive perioperative antibiotics. Randomized data were reported only on the use of a single shot cephfazolin although some other antibiotic agents are supposed to be equally effi‐ cient as almost every perioperative device infection is caused by staphylococci or strepto‐ cocci. In some hospitals with a high rate of methicillin resistant staphylococci vancomycin may be the most proper choice. There is an interesting new approach with

the idea and techniques are promising.

116 Cardiac Defibrillation

Wong et al., Journal of the American Chemical Society 2010.

**3. Conclusion / recommendation**

coated devices that needs further evaluation.

University of Giessen and Marburg, Medical Clinic I, Department of Cardiology, Giessen, Germany and Kerckhoff Heart and Thorax Center, Department of Cardiology, Bad Nau‐ heim,, Germany


**5. Instructional methods and implementation of patient safety education**

Patient safety as a subject is new, generic, multidisciplinary and highly contextual course. It should be based on experiences, and learners should have the opportunity to reflect on their practices.

• Integrated with the existing curriculum.

Although patient safety is a new subject, it has many facets in the existing curriculum and links with basic and clinical sciences. Almost all healthcare curricula have restricted space and time for adding new courses. It is a good approach to review the existing curriculum to identify where to integrate patient safety topics. Thus, it could be vertically integrated into the existing curriculum. Topics of patient safety are generic and could be applied to any specialty. In the existing curriculum, we can find generic areas that are suitable to include patient safety principles e.g. communication skills, ethics, professionalism…etc.

Patient safety is related to all healthcare professionals' clinical practice so it should not be studied in isolation. Topics of patient safety curriculum were designed to be easily integrated into the existing medical teaching, for example, anatomy, pediatric, physiology, etc. Incorporation of all topics is essential for the development of safe heath care providers [13]. Spiral approach is recommended while implementing patient safety curriculum. The curriculum should be spread over the undergraduate level program [17].

• Multi-professional/ Multidisciplinary.

The WHO Multi-professional Patient Safety Curriculum Guide (2011) was established responding to the need for providing harmless care. Being a safe healthcare provider requires different competencies that cover specific knowledge, skills, and attitude. Heath care workers should collaborate together to provide safe service, to guarantee that patient safety learning is delivered in an incorporated way which should be single coordinated, system based, in a team dependent approach, and includes different specialties. Patient safety curriculum includes basic, behavioral and clinical sciences. It is a multi-professional subject needs the repeated application to the workplace settings. It has been reported that medical students are positive about learning with other students who participated in clerkships of different specialties

• Experiential/ Provides opportunities for application and reflection

The course may include interactive lectures, e.g. problems with inappropriate supervision by a physician, to highlight the relation between theory and practice. Then the students had to reflect on incidents concerning patient safety based on their own personal experience and to complete an incident report card for each of these incidents. The course may also include presentations arranged by the students, which are followed by a 10-minute discussion for each presentation. Assessment of the students includes content, structure and presentation techniques [10].

Most courses in patient safety were introduced by lecturing and discussion which have short terms positive changes but the transfer of knowledge to the practice is low [9]. Learning patient safety could be enhanced by reflection, feedback, portfolio, and critical incident analysis, case discussions with senior clinicians, simulation environments and workshops. So, patient safety courses based on personal experiences and reflections enable students to transfer knowledge into practice and have a high impact on future career [10]. Some studies reveal that students emphasized active learning and experiential activities to reinforce safety principles [18].

• Contextual.

To ensure patient safety, the future physician must be prepared to know potential sources of errors and to recognize their own susceptibilities to error. An elective course in the open disclosure of the health care providers, which is communicating with the patients the errors and how it happened, can be introduced. This training of disclosure may decrease the harm

The course of patient safety necessities to be more focused. Writing objectives that are specific to the learners, measurable and relevant to their needs, help to focus the content course and essential for planning the appropriate instructional methods of conducting the

Patient safety as a subject is new, generic, multidisciplinary and highly contextual course. It should be based on experiences, and learners should have the opportunity to reflect on their

Although patient safety is a new subject, it has many facets in the existing curriculum and links with basic and clinical sciences. Almost all healthcare curricula have restricted space and time for adding new courses. It is a good approach to review the existing curriculum to identify where to integrate patient safety topics. Thus, it could be vertically integrated into the existing curriculum. Topics of patient safety are generic and could be applied to any specialty. In the existing curriculum, we can find generic areas that are suitable to include patient safety

Patient safety is related to all healthcare professionals' clinical practice so it should not be studied in isolation. Topics of patient safety curriculum were designed to be easily integrated into the existing medical teaching, for example, anatomy, pediatric, physiology, etc. Incorporation of all topics is essential for the development of safe heath care providers [13]. Spiral approach is recommended while implementing patient safety curriculum. The cur-

The WHO Multi-professional Patient Safety Curriculum Guide (2011) was established responding to the need for providing harmless care. Being a safe healthcare provider requires different competencies that cover specific knowledge, skills, and attitude. Heath care workers should collaborate together to provide safe service, to guarantee that patient safety learning is delivered in an incorporated way which should be single coordinated, system based, in a team dependent approach, and includes different specialties. Patient safety curriculum includes basic, behavioral and clinical sciences. It is a multi-professional subject needs the repeated application to the workplace settings. It has been reported that

**5. Instructional methods and implementation of patient safety**

principles e.g. communication skills, ethics, professionalism…etc.

riculum should be spread over the undergraduate level program [17].

of the future patients [16].

96 Vignettes in Patient Safety - Volume 3

• Integrated with the existing curriculum.

• Multi-professional/ Multidisciplinary.

course.

**education**

practices.

Patient safety is highly contextual, so, students should have adequate professional practices to learn patient safety, in this regard patient safety is best taught once students involved in the health services. However, some behavioral sciences-based subjects could be learned early such as; what is patient safety, what are human factors, and understanding systems modules. Students need to continuously reflect on their practices and apply the learned knowledge and performance to be a safer provider of health care. Using critical cards incidents to help students reflecting on their personal experiences seems to be useful in improving the transfer of knowledge [10].

#### **5.1. Who should teach patient safety?**

Advocates of patient safety are usually from administrative nonacademic staff. To integrate patient safety throughout the curriculum we need a large number of academic teachers who often are not familiar with concepts and principles of patient safety. Some of them may practice patient safety principles without being aware of such knowledge. Academic clinicians, administrators, nurses, engineers, behavioral scientists are all involved in teaching patient safety. They should have capacity building through training workshops and seminars. Some schools trained healthcare administrators to deliver patient safety curriculum for undergraduates' students [9].

#### **5.2. Limitations**

From the point of view of the tutors who were involved in the implementation of the patient safety curriculum, some recommendations emerged. For example, training of the tutors, and the participation of large number staff in implementation, which will reduce the load on one or two tutors, are essential. The local support for implementation is also required for allocating more time and resources. They also recommended full integration of the curriculum in the undergraduate years [19]. Cost issues are limited to the time of the teachers and the students when the materials are available and the curriculum topics are provided as in the WHO guide [20].

Identification of users of these evaluations is an important step in the evaluation plan. Participants in patient safety courses have sake to provide their own views and participate in the assessment process concerning their own performance and the designed curriculum. These evaluations can provide feedback and be a source of motivation for continuous improvement for learners, faculty, and curriculum developers. An Example for this was the evaluation study of the WHO patient safety curriculum guide, its main aim was assessing the effectiveness of using the guide in teaching patient safety for postgraduate and graduate medical students. Concerning the feedback from this evaluation, it was utilized to guide through future versions of the Curriculum Guide and enhance the understanding of the suc-

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The evaluation results should be publicized as this would be interesting to educators from other institutions that are willing to introduce patient safety principles in their curricula.

After identifying users, we should identify uses of the evaluation, which are generic and specific ones. The generic uses refer to whether the evaluation is used to appraise the performance of individuals, the performance of the entire program, or both. The assessment of learners is closely related to whether they have achieved the cognitive, affective, or psychomotor or competency objectives of a curriculum or not. Meanwhile, it refers to whether an evaluation is used for formative purposes, for summative ones or for both purposes as discussed before. One more thing that should be considered is the specific needs of different users (stakeholders) and the specific ways in which they will put the evaluation to use [21]. Specific uses for evaluation results might include the following: feedback on individual learners' performance to assign grades or detect mastery in certain skills. Feedback on and improvement of program performance is also included in specific uses as the evaluation results could be used to identify parts of the curriculum that are effective and parts that are in need of improvement. Evaluation results may also provide suggestions about how parts of the curriculum could be

Identifying resources that will be used, followed by choosing measurement methods, and

Data collection methods that were used to evaluate the patient safety curriculum guide ranged from simple methods as getting students' perception about the course after receiving a patient safety teaching, and complex methods such as having faculty to review the conducted whole curriculum. These complex methods involve a varieties of tools such as surveys, interviews, and focus group with students, faculty or administration, observation and other methods. Reported data collection tools by previous studies either were face to face or telephone interviews with key stakeholders: teaching staff, and executives at the involved medical schools. Students' surveys regarding patient safety topics were collected before and after teaching patient safety curricula. The two methods were used to get different data. The pre-teaching ones to get information about students' perceptions and attitude towards patient safety and to test their knowledge of patient safety facts and actions. Meanwhile, the post teaching collected data measures two domains the effectiveness of the topics and the effectiveness of

cessful methods of introducing patient safety to curricula [21].

constructing instruments were also included in evaluation plan.

*6.2.2. Step 2: collecting and analyzing data*

improved [21].

#### **6. Evaluation and student assessment methods**

Evaluating the course content and the process of implementation is an opportunity for further improvement and reforming. Evaluation includes evaluation of the program as well as students' assessment.

#### **6.1. Evaluation approaches**

Evaluation of any program is variable and has a direct relationship to the intended learning outcomes (ILOs) of the course. It takes various forms, may be either formative or summative, or even both as conducted in WHO patient safety curriculum guide. In the latter, each school selects the patient safety topics in the Curriculum Guide and has the flexibility to do that with plans on how to incorporate these topics in their existing curricula. Then, formative evaluation is conducted where assess the medical schools' different experiences in using the WHO curriculum guide. The aim of this evaluation was to provide feedback to WHO stakeholders and concerned bodies regarding capacity building, implementation, with suggestions for improvement. This also will help other schools who want to use this guide in the future. On the other hand, in summative evaluation, the scope was to the evaluation of the effectiveness of the curriculum guide to develop patient safety curriculum. Retrospective data emerged form conducted interview while prospective data excluded from pre-and-post surveys of students receiving the courses [4].

Overall, the main aim of the conducted evaluative studies of the Patient Safety Curriculum Guide is to assess its effectiveness for teaching patient safety to both undergraduate and graduate medical students [3]. The results of these evaluative studies will guide others when planning for their curriculum guides and promotes in depth background of successful methods used in introducing patient safety to curricula [10].

#### **6.2. Evaluation steps**

Evaluation of the designed course is a necessity. Evaluation involves three main steps, developing an evaluation plan; collecting and analyzing information; disseminating the findings to appropriate stakeholders action [3].

#### *6.2.1. Step 1: the evaluation plan*

In the evaluation plan, it is the framework for the process. So, you should first identify what's to be evaluated, who are your stakeholders, the purpose of the evaluation which is closely related to the evaluation questions.

Identification of users of these evaluations is an important step in the evaluation plan. Participants in patient safety courses have sake to provide their own views and participate in the assessment process concerning their own performance and the designed curriculum. These evaluations can provide feedback and be a source of motivation for continuous improvement for learners, faculty, and curriculum developers. An Example for this was the evaluation study of the WHO patient safety curriculum guide, its main aim was assessing the effectiveness of using the guide in teaching patient safety for postgraduate and graduate medical students. Concerning the feedback from this evaluation, it was utilized to guide through future versions of the Curriculum Guide and enhance the understanding of the successful methods of introducing patient safety to curricula [21].

The evaluation results should be publicized as this would be interesting to educators from other institutions that are willing to introduce patient safety principles in their curricula.

After identifying users, we should identify uses of the evaluation, which are generic and specific ones. The generic uses refer to whether the evaluation is used to appraise the performance of individuals, the performance of the entire program, or both. The assessment of learners is closely related to whether they have achieved the cognitive, affective, or psychomotor or competency objectives of a curriculum or not. Meanwhile, it refers to whether an evaluation is used for formative purposes, for summative ones or for both purposes as discussed before. One more thing that should be considered is the specific needs of different users (stakeholders) and the specific ways in which they will put the evaluation to use [21]. Specific uses for evaluation results might include the following: feedback on individual learners' performance to assign grades or detect mastery in certain skills. Feedback on and improvement of program performance is also included in specific uses as the evaluation results could be used to identify parts of the curriculum that are effective and parts that are in need of improvement. Evaluation results may also provide suggestions about how parts of the curriculum could be improved [21].

Identifying resources that will be used, followed by choosing measurement methods, and constructing instruments were also included in evaluation plan.

#### *6.2.2. Step 2: collecting and analyzing data*

tutors, are essential. The local support for implementation is also required for allocating more time and resources. They also recommended full integration of the curriculum in the undergraduate years [19]. Cost issues are limited to the time of the teachers and the students when the materials are available and the curriculum topics are provided as in the WHO guide [20].

Evaluating the course content and the process of implementation is an opportunity for further improvement and reforming. Evaluation includes evaluation of the program as well as

Evaluation of any program is variable and has a direct relationship to the intended learning outcomes (ILOs) of the course. It takes various forms, may be either formative or summative, or even both as conducted in WHO patient safety curriculum guide. In the latter, each school selects the patient safety topics in the Curriculum Guide and has the flexibility to do that with plans on how to incorporate these topics in their existing curricula. Then, formative evaluation is conducted where assess the medical schools' different experiences in using the WHO curriculum guide. The aim of this evaluation was to provide feedback to WHO stakeholders and concerned bodies regarding capacity building, implementation, with suggestions for improvement. This also will help other schools who want to use this guide in the future. On the other hand, in summative evaluation, the scope was to the evaluation of the effectiveness of the curriculum guide to develop patient safety curriculum. Retrospective data emerged form conducted interview while prospective data excluded from pre-and-post surveys of

Overall, the main aim of the conducted evaluative studies of the Patient Safety Curriculum Guide is to assess its effectiveness for teaching patient safety to both undergraduate and graduate medical students [3]. The results of these evaluative studies will guide others when planning for their curriculum guides and promotes in depth background of successful meth-

Evaluation of the designed course is a necessity. Evaluation involves three main steps, developing an evaluation plan; collecting and analyzing information; disseminating the findings to

In the evaluation plan, it is the framework for the process. So, you should first identify what's to be evaluated, who are your stakeholders, the purpose of the evaluation which is closely

**6. Evaluation and student assessment methods**

students' assessment.

98 Vignettes in Patient Safety - Volume 3

**6.1. Evaluation approaches**

students receiving the courses [4].

appropriate stakeholders action [3].

related to the evaluation questions.

*6.2.1. Step 1: the evaluation plan*

**6.2. Evaluation steps**

ods used in introducing patient safety to curricula [10].

Data collection methods that were used to evaluate the patient safety curriculum guide ranged from simple methods as getting students' perception about the course after receiving a patient safety teaching, and complex methods such as having faculty to review the conducted whole curriculum. These complex methods involve a varieties of tools such as surveys, interviews, and focus group with students, faculty or administration, observation and other methods. Reported data collection tools by previous studies either were face to face or telephone interviews with key stakeholders: teaching staff, and executives at the involved medical schools. Students' surveys regarding patient safety topics were collected before and after teaching patient safety curricula. The two methods were used to get different data. The pre-teaching ones to get information about students' perceptions and attitude towards patient safety and to test their knowledge of patient safety facts and actions. Meanwhile, the post teaching collected data measures two domains the effectiveness of the topics and the effectiveness of teaching; through measuring the change of students' perception, knowledge and attitude towards patient safety taught topics after completing the course [4].

In either case, there are three interconnected elements to consider in terms of data analysis [23]:

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• Data reduction; which means simplifying and in other words transforming the raw infor-

• Conclusion drawing; which is closely related to constructing meaning from the data, with

So, by this time, we have developed our evaluation plan, collected our data and analyzed their

This is a crucial step that should not be overlooked. In some cases the conclusions and recommendations of evaluations are not acted upon, and as a consequence this will lead that the reached valuable information is not feed-backed in a meaningful way to all relevant stakeholders. In some instances, the results of evaluation are concerned with the quality of patient safety teaching, so these results (e.g. from student questionnaires, peer observed teaching sessions) must be relayed to and discussed not only with administration, but also with the teachers. The key here in education is to provide an effective constructive feedback. Brinko provided an excellent review of best practice on the process of giving feedback for students or colleagues. It is important that any feedback is received in a way that encourages growth or improvement of learners. Meanwhile, If the evaluation focuses on the effectiveness of the patient safety curriculum, any conclusions and recommendations for improvement must be communicated to all who had a share in implementing the curriculum (e.g. at faculty, teacher

The dissemination step may be in the form of reports or concerned bodies meetings and its format must be meaningful and relevant. Effective communication of evaluation outcomes, findings and recommendations is a key catalyst for improvements in patient safety teaching

One of the reported evaluation models was evaluation of patient safety initiative using the CIPP which stands for (Context, Input, Process, and Product) model. The framework emphasizes multiple stakeholders' interests (e.g. patients, providers, researchers). In this context, many methods fundamental to formative evaluations were used, including use of logic models to frame the evaluation, use of interview and focus group techniques to collect data, triangulation of results from multiple stakeholders, and feedback about the findings to help

In CIPP framework, evaluation emphasizes on documenting what happens in a program including the contextual factors that influenced what occurred. The evaluation shifts its focus according to changes occurring in the program over time, and its intention is to influence

results. Here comes the stage of disseminating these results to the relevant bodies.

• Data display; which refers to organizing information collected in a meaningful way;

mation into a more workable or usable form;

*6.2.3. Step 3: disseminating findings and taking action*

respect to the evaluation question(s).

and student levels).

and curriculum design [24].

**6.3. Used evaluation models**

to strengthen the program.

Concerning the timing of data collection, it is better to start as early as possible. It is better to start form the first week of teaching and end within three weeks up to two months after completion of the course. This depends on the availability of faculty staff and executives to complete the interviews and focus groups [4].

The survey questions were grouped in four domains as reported in many studies: patient safety knowledge; Healthcare system safety; Personal influence over safety; Personal attitude about safety. The WHO staff has developed questions of patient safety knowledge those were reviewed by the developers of the patient safety curriculum guide [3].

The contents of the interview and students' surveys were developed to collect data for answering four research questions defined for evaluation. These questions proposed for WHO curriculum evaluation guide as follow:

One of the reported data collection tools is reflection. Self-reflection has an important role in evaluation and represented a chief activity for a medical or clinical educator. For a reflection to be effective, it may include: experience of teaching or feedback received from others; description of how you felt as a learner and whether you were surprised by those feelings; re-evaluating your experience. Self-reflection will enhance the development of new perspectives in terms of improving the teaching or learning of patient safety approaches and procedures [4].

It is worth mentioning that some studies used a mixed method triangulation design to evaluate their patient safety course. A Course Evaluation Questionnaire (CEQ) completed by participants to assess the overall perceptions and effects of the course and data from incident report cards were used as quantitative measures. Focus groups with participants of the course were used as qualitative tools to get in depth information of the course effect.

During the focus groups, students were asked questions related to their experience with the course, what they believed they had learnt from it, whether they had experienced situations in which patient safety was compromised, if they felt more capable to act safely in their daily practice, and how this feeling was influenced by their environment [10, 22].

Data analysis: data collection may be using any of the previously mentioned tools, may also involve others. They may be just quantitative, qualitative or a combination of both as the case in mixed methods approach.

In either case, there are three interconnected elements to consider in terms of data analysis [23]:

So, by this time, we have developed our evaluation plan, collected our data and analyzed their results. Here comes the stage of disseminating these results to the relevant bodies.

#### *6.2.3. Step 3: disseminating findings and taking action*

teaching; through measuring the change of students' perception, knowledge and attitude

Concerning the timing of data collection, it is better to start as early as possible. It is better to start form the first week of teaching and end within three weeks up to two months after completion of the course. This depends on the availability of faculty staff and executives to

The survey questions were grouped in four domains as reported in many studies: patient safety knowledge; Healthcare system safety; Personal influence over safety; Personal attitude about safety. The WHO staff has developed questions of patient safety knowledge those were

The contents of the interview and students' surveys were developed to collect data for answering four research questions defined for evaluation. These questions proposed for WHO cur-

**1.** Does the curriculum guide contains the necessary as well as sufficient information and topics to allow its effective use in undergraduate training of healthcare professionals? **2.** What is the impact upon students' learning of the inclusion of patient safety teaching in

**3.** In what ways can this curriculum guide be used to support the widespread implementa-

**4.** How could the curriculum guide be modified in the future to best support teaching of

One of the reported data collection tools is reflection. Self-reflection has an important role in evaluation and represented a chief activity for a medical or clinical educator. For a reflection to be effective, it may include: experience of teaching or feedback received from others; description of how you felt as a learner and whether you were surprised by those feelings; re-evaluating your experience. Self-reflection will enhance the development of new perspectives in terms of

It is worth mentioning that some studies used a mixed method triangulation design to evaluate their patient safety course. A Course Evaluation Questionnaire (CEQ) completed by participants to assess the overall perceptions and effects of the course and data from incident report cards were used as quantitative measures. Focus groups with participants of the course

During the focus groups, students were asked questions related to their experience with the course, what they believed they had learnt from it, whether they had experienced situations in which patient safety was compromised, if they felt more capable to act safely in their daily

Data analysis: data collection may be using any of the previously mentioned tools, may also involve others. They may be just quantitative, qualitative or a combination of both as the case

improving the teaching or learning of patient safety approaches and procedures [4].

were used as qualitative tools to get in depth information of the course effect.

practice, and how this feeling was influenced by their environment [10, 22].

towards patient safety taught topics after completing the course [4].

reviewed by the developers of the patient safety curriculum guide [3].

complete the interviews and focus groups [4].

tion of explicit patient safety education globally?

patient safety to students in different environments? [3]

riculum evaluation guide as follow:

the curriculum?

100 Vignettes in Patient Safety - Volume 3

in mixed methods approach.

This is a crucial step that should not be overlooked. In some cases the conclusions and recommendations of evaluations are not acted upon, and as a consequence this will lead that the reached valuable information is not feed-backed in a meaningful way to all relevant stakeholders. In some instances, the results of evaluation are concerned with the quality of patient safety teaching, so these results (e.g. from student questionnaires, peer observed teaching sessions) must be relayed to and discussed not only with administration, but also with the teachers. The key here in education is to provide an effective constructive feedback. Brinko provided an excellent review of best practice on the process of giving feedback for students or colleagues. It is important that any feedback is received in a way that encourages growth or improvement of learners. Meanwhile, If the evaluation focuses on the effectiveness of the patient safety curriculum, any conclusions and recommendations for improvement must be communicated to all who had a share in implementing the curriculum (e.g. at faculty, teacher and student levels).

The dissemination step may be in the form of reports or concerned bodies meetings and its format must be meaningful and relevant. Effective communication of evaluation outcomes, findings and recommendations is a key catalyst for improvements in patient safety teaching and curriculum design [24].

#### **6.3. Used evaluation models**

One of the reported evaluation models was evaluation of patient safety initiative using the CIPP which stands for (Context, Input, Process, and Product) model. The framework emphasizes multiple stakeholders' interests (e.g. patients, providers, researchers). In this context, many methods fundamental to formative evaluations were used, including use of logic models to frame the evaluation, use of interview and focus group techniques to collect data, triangulation of results from multiple stakeholders, and feedback about the findings to help to strengthen the program.

In CIPP framework, evaluation emphasizes on documenting what happens in a program including the contextual factors that influenced what occurred. The evaluation shifts its focus according to changes occurring in the program over time, and its intention is to influence

**Figure 1.** Diagram of the steps of the curriculum guide evaluation.

these changes. In this model, evaluation takes several steps, in the first evaluation year, the context and input aspects of the CIPP model are the main focus as well as early experiences in implementing the initiative. The context and input portions of the evaluation were used to examine the strategic aspects of the initiative, which are the circumstances leading to the development of the patient safety initiative (context) and, the strategies followed to carry out the initiative (input). Thereafter, in later evaluation years, the focus is directed towards the process evaluation addressing the operational aspects of carrying out the activities involved, taking into consideration how these activities contributed or may be contributing to the main goal of improving patient safety curricula. Meanwhile, there is a regular update on the information on context and input to assess how changes in the strategic aspects of the initiative had effect. Finally, the last step is the product evaluation, this is performed by measuring the effects of the patient safety initiative on various stakeholder groups [25].

The topics are selected according to the recourses available and it is better integrated into the whole undergraduate curriculum. The objectives are well-defined, competency-based and directly related to the selected content. The instruction should be practice-based and studentcentered. Following this systematic approach maximize the role of the evaluation of students and curriculum in judging the merits of the implemented curriculum. These steps are illus-

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In brief, patient safety is now of international interest and healthcare providers need to learn its principles. Meanwhile, educational strategies involve learning by doing and reflections are essential to bridge the gap between theory and practice. Therefore, patient safety curriculum should be integrated with all levels and years of education. It should be also multidisciplinary and multi-professional. Students should be involved in the health services and have the opportunity to apply the learnt knowledge and performance and reflect on their practices. The outcomes and impact of the implemented curriculum should be continuously evaluated to ensure that skills of the health professionals regarding keeping a safe environment, for both them and the patients, are acquired and such skills are recognized as other clinical and professional skills. All this will increase the effectiveness of health care system and decrease

trated in the conceptual framework (**Figure 2**).

**Figure 2.** The conceptual framework for patient safety curriculum development.

**8. Conclusion**

The steps of the evaluation process for WHO curriculum guide are summarized in the below diagram. Three steps of evaluation are represented: first, evaluation plan which is followed by the second step which is collecting and analyzing data, then the third step of disseminating findings and taking actions (**Figure 1**).


# **Protected Areas in Forest Conservation Challenges and Opportunities**

Printed Edition of the Special Issue Published in *Forests* Panayiotis Dimitrakopoulos and Nikoleta Jones Edited by

www.mdpi.com/journal/forests


**Acknowledgements**

This work was supported by Southeast Missouri State University and the Missouri Rice Research and Merchandising Council. The authors also wish to thank the assistance of the LSU Agcenter H. Rouse Caffey Rice Research Station for research related to two line hybrids.


*Article* **Relative Kinematic Orbit Determination for GRACE-FO Satellite by Jointing GPS and LRI**

**Zhouming Yang 1, Xin Liu 1,\*, Jinyun Guo 1, Hengyang Guo 1, Guowei Li 2, Qiaoli Kong 1 and Xiaotao Chang 3**

**Abstract:** As the first in-orbit formation satellites equipped with a Laser Ranging Interferometer (LRI) instrument, Gravity Recovery and Climate Experiment Follow-on (GRACE-FO) satellites are designed to evaluate the effective ability of the new LRI ranging system applied to satellite-to-satellite tracking. To evaluate the application of LRI in GRACE-FO, a relative kinematic orbit determination scheme for formation satellites integrating Kalman filters and GPS/LRI is proposed. The observation equation is constructed by combining LRI and spaceborne GPS data, and the intersatellite baselines of GRACE-FO formation satellites are calculated with Kalman filters. The combination of GPS and LRI techniques can limit the influence of GPS observation errors and improve the stability of orbit determination of the GRACE-FO satellites formation. The linearization of the GPS/LRI observation model and the process of the GPS/LRI relative kinematic orbit determination are provided. Relative kinematic orbit determination is verified by actual GPS/LRI data of GRACE-FO-A and GRACE-FO-B satellites. The quality of relative kinematic orbit determination is evaluated by reference orbit check and K-Band Ranging (KBR) check. The result of the reference orbit check indicates that the accuracy of GRACE-FO relative kinematic orbit determination along X, Y, and Z (components of the baseline vector) directions is better than 2.9 cm. Compared with the relative kinematic orbit determination by GPS only, GPS/LRI improves the accuracy of the relative kinematic orbit determination by approximately 1cm along with X, Y and Z directions, and by about 1.8 cm in 3D directions. The overall accuracy of relative kinematic orbit determination is improved by 25.9%. The result of the KBR check indicates that the accuracy of the intersatellite baseline determination is about +/−10.7 mm.

**Keywords:** GRACE-FO; formation satellites; spaceborne GPS; Laser Ranging Interferometer; relative kinematic orbit determination


2. Terminology of the louvered fin

secondary flow patterns introduced by sudden velocity changes. On the other hand, interrupted surfaces achieve heat transfer enhancement by the continuous growth and destruction of laminar boundary layers on the interrupted portion of the geometry. One of the mostly used example of the interrupted surface is the louvered fin. The louvered fins were firstly investigated by Kays and London [2] in 1950s, and the popularities of the louvered fins

Figure 1. Fin geometries for plate fin heat exchangers: (a) plain triangular fin; (b) plain rectangular fin; (c) wavy fin; (d)

Today, the use of louvered fins has become popular in the fields of automotive, heating, cooling, air conditioning, power plants and food industry. Typical structure of the louvered fin is shown in Figure 2. The efforts of maximize the heat transfer and minimize the pressure drop in heat exchanger design are rapidly increasing due

have been maintained.

offset strip fin; (e) multi-louver fin; (f) perforated fin [1].

62 Heat Exchangers– Advanced Features and Applications

Figure 2. Typical structure of a louver fin geometry [4].

The terminology of a louvered fins was firstly created by Kays and London [2] as shown in Figure 3. Each louvered fin configurations is designated by two figures. The first indicates the length of the louvered fin in the flow direction and the second indicates the fin pitch per inch transverse to the flow. Therefore, the meaning of "1/2–6.06" is that each louver has length of 1/2 inch in the flow direction and 6.06 fins in per inch.

Another terminology used for louvered fins with a flat tube is illustrated in Figure 4. It is shown from the cross-sectional view that the gap between two louvered fins is called fin pitch (Fp). The length of the flow from the leading edge up to the end of the fin is called flow depth (Fd). The vertical length of the fin and the louver are called fin height and louver height and designated by Fh and Lh, respectively. The horizontal length of the gap between each louver is called louver pitch (Lp), and each louver has an angle of Lα.

Figure 3. Terminology of the louvered fin [2].

Figure 4. Terminology of the louvered fin [6].

#### 3. Flow phenomenon in louvered fin arrays

The structure of the flow passes through the louvered fins can be identified with flow visualization technique using dye injection and hydrogen bubble. Numerical analysis is also a method to identify the flow phenomenon of louvered fins. Several experimental and numerical studies indicate that the geometric design and the free velocity of the flow effect the direction of the flow through the louvers. As shown in Figure 5, the flow enters from the leading edge of the first louver and then directed by the louvers or the fins. If the greatest proportion of the flow is passing between the louvers, it is called "louver directed flow". Similarly, if the greatest proportion of the flow is passing through the gap between the fins, it is called "fin or duct directed flow" [7].

Figure 5. Possible flow direction of flow through the louvered fins.

Figure 6. Definition of the flow efficiency.

3. Flow phenomenon in louvered fin arrays

Figure 4. Terminology of the louvered fin [6].

Figure 3. Terminology of the louvered fin [2].

64 Heat Exchangers– Advanced Features and Applications

directed flow" [7].

The structure of the flow passes through the louvered fins can be identified with flow visualization technique using dye injection and hydrogen bubble. Numerical analysis is also a method to identify the flow phenomenon of louvered fins. Several experimental and numerical studies indicate that the geometric design and the free velocity of the flow effect the direction of the flow through the louvers. As shown in Figure 5, the flow enters from the leading edge of the first louver and then directed by the louvers or the fins. If the greatest proportion of the flow is passing between the louvers, it is called "louver directed flow". Similarly, if the greatest proportion of the flow is passing through the gap between the fins, it is called "fin or duct This definition has revealed another concept called flow efficiency (η) [3]. Figure 6 provides a visual definition of the flow efficiency, and it is calculated by Eq. (1)

$$\eta = \frac{N}{D} = \frac{\text{Actual transverse distance}}{\text{Ideal transverse distance}}\tag{1}$$

According to the Eq. (1), if the flow efficiency is equal to 1, the flow is parallel to the louvers. If it is equal to zero, the flow is axial through the louvered fin array which is 100% duct flow [3]. Figure 7 shows the structure of the flow between the louvers. The photographs of the flow through the louvered fin for a louver angle of 26° at a Reynolds number of 500 are obtained using dye injection and hydrogen bubbles techniques. It can be seen that the significant proportion of the flow is directed by the louvers under these circumstances. It is observed that the boundary layers exist on both the upper and lower surfaces of the louver. Flow separation is observed on the back side of the inlet louvers and boundary layer exists on both the upper and lower surfaces of the louvers [3].

Additionally, a large adverse pressure gradient exists on the downstream side of the louvered fin, and the flow separates at the leading edge and forms a large recirculation bubble. Figure 8a clearly shows this recirculation zone which is called "first recirculation zone" for a louver angle of 25° at a Reynolds number of 510 using naphthalene sublimation technique by DeJong and Jacobi [8]. This large recirculation zone circulates in a clockwise direction, resulting in a region of very high shear near the trailing edge of the louver where flow that passes downstream between fins interacts with the separation bubble. The high shear results in the formation of a small "secondary recirculation zone" with counter-clockwise rotation in the wake just downstream of the end of the louver. Except at very low Reynolds numbers, a

Figure 7. Visualization of the flow in the louvered fin array [3].

Figure 8. Flow structure around louvered fins: (a) Re = 510, (b) Re = 820 [8].

"third recirculation zone" forms on the upstream side of each louver. This third recirculation zone is caused when the flow passes through the gap between the first recirculation zone and the next louver downstream. This gap is narrow near the leading edge and much larger near the trailing edge. Flow in this gap must decelerate as it passes between the louvers. At all but the lowest Reynolds numbers where the first separation zone is small, the adverse pressure gradient in the inter-louver gap is large enough to cause separation from the upstream face of the next louver. The result is the third recirculation zone with counter-clockwise circulation [8].

Figure 8b shows flow through the same geometry at a higher Reynolds number (820) where the flow has become unsteady. The third recirculation zone has grown to become as large as the first zone, and the small second zone is no longer clearly evident. Two counter-rotating cells are present between the louvers. Fluid is periodically entrained in the recirculation zones and then ejected in the form of vortices which are carried downstream [8].

Today, the visualization techniques are developing parallel with the rapidly increasing technology. Besides the numerical analysis, infrared technology is a method to identify the flow characteristics of any flow. An open-circuit wind tunnel equipped with an infrared thermovision is illustrated in Figure 9. Infrared temperature measurement is achieved using an infrared camera. The electromagnetic energy radiated in the infrared spectral band by an object is transformed into an electronic signal by each of the thermo-vision sensors and is obtained simultaneously across the whole field of view, which depend on the optical focal length and the viewing distance [9].

In Figure 10, comparison of the experimental results obtained by the infrared measurements and the results of numerical analysis for the same louvered fin geometry is illustrated. The

Figure 9. Wind tunnel test equipped with an infrared thermo-vision [9].

"third recirculation zone" forms on the upstream side of each louver. This third recirculation zone is caused when the flow passes through the gap between the first recirculation zone and the next louver downstream. This gap is narrow near the leading edge and much larger near the trailing edge. Flow in this gap must decelerate as it passes between the louvers. At all but the lowest Reynolds numbers where the first separation zone is small, the adverse pressure gradient in the inter-louver gap is large enough to cause separation from the upstream face of the next louver. The result is the third recirculation zone with counter-clockwise circulation [8]. Figure 8b shows flow through the same geometry at a higher Reynolds number (820) where the flow has become unsteady. The third recirculation zone has grown to become as large as the first zone, and the small second zone is no longer clearly evident. Two counter-rotating

Figure 7. Visualization of the flow in the louvered fin array [3].

66 Heat Exchangers– Advanced Features and Applications

Figure 8. Flow structure around louvered fins: (a) Re = 510, (b) Re = 820 [8].

Figure 10. Comparison of the temperature distribution of an infrared thermographs and numerical simulation results for a louvered fin array [9].

louvered fin has a louver angle of 20° and the flow velocity is 1.0 m/s. It is observed that both methods give similar temperature distributions across the entire louvered fin.

#### 4. Data reduction in a louvered fin heat exchanger

In this section, the calculation method of the performance of a louvered fin heat exchanger is summarized. The equations will be written by considering the following assumptions.

I. Cold flow is the external flow of the louvered fin heat exchanger.

II. Hot flow is the internal flow of the louvered fin heat exchanger.

III. Thermophysical properties of both fluid are constant.

IV. The louvered fins are attached to a mini-channel flat tube.

V. Cold flow is uniform at the inlet of the louvered fin for the numerical analysis.

VI. The temperature of the tube wall is constant for the analytical solutions.

The main problem is the determination of external side heat transfer coefficient for the louvered fin surfaces by experimentally. Effectiveness-NTU method is generally used to determine the external side heat transfer coefficient by following the Kim and Bullard [10] method.

The average heat transfer rate can be expressed as

$$
\dot{Q} = (\dot{Q}\_c + \dot{Q}\_h)/2 \tag{2}
$$

where Q\_ cand Q\_ h are the heat transfer rates of cold and hot fluid, respectively. The heat transfer rates of each fluid can be calculated with Eqs. (3) and (4)

$$
\dot{Q}\_c = \dot{m}\_c c\_{p,c} (T\_{c,o} - T\_{c,i}) \tag{3}
$$

$$
\dot{Q}\_h = \dot{m}\_h \varepsilon\_{p,h} (T\_{h,i} - T\_{h,o}) \tag{4}
$$

The effectiveness of the heat exchanger for one row configuration can be calculated using the following equation for both fluid unmixed

$$\varepsilon = 1 - \exp\left[\frac{NTU^{0.22}}{\mathbb{C}\_r} \{ \exp\left( -\mathbb{C}\_r NTU^{0.78} \right) - 1 \} \right] \tag{5}$$

where

$$
\varepsilon = \dot{\mathbb{Q}} / \dot{\mathbb{Q}}\_{\text{max}} \tag{6}
$$

$$\mathbf{C}\_{\mathbf{r}} = \frac{(\dot{m}c\_p)\_{\text{min}}}{(\dot{m}c\_p)\_{\text{max}}} \tag{7}$$

We can obtain overall heat transfer coefficient (UA) for the heat exchanger as

Comprehensive Study of Heat Exchangers with Louvered Fins http://dx.doi.org/10.5772/66472 69

$$
\Delta LA = (\dot{m}c\_p)\_{\text{min}} NTLI \tag{8}
$$

where

louvered fin has a louver angle of 20° and the flow velocity is 1.0 m/s. It is observed that both

In this section, the calculation method of the performance of a louvered fin heat exchanger is

The main problem is the determination of external side heat transfer coefficient for the louvered fin surfaces by experimentally. Effectiveness-NTU method is generally used to determine the external side heat transfer coefficient by following the Kim and Bullard [10] method.

cand Q\_ h are the heat transfer rates of cold and hot fluid, respectively. The heat transfer

f exp ð−CrNTU0:78Þ−1g

" #

The effectiveness of the heat exchanger for one row configuration can be calculated using the

Cr ¼ ðmc\_ pÞmin ðmc\_ pÞmax

c þ Q\_ hÞ=2 (2)

c ¼ m\_ ccp, cðTc, o−Tc,iÞ (3)

h ¼ m\_ hcp,hðTh,i−Th, oÞ (4)

ε ¼ Q\_ =Q\_ max (6)

(5)

(7)

summarized. The equations will be written by considering the following assumptions.

V. Cold flow is uniform at the inlet of the louvered fin for the numerical analysis.

Q\_ ¼ ðQ\_

Q\_

Q\_

NTU0:22 Cr

We can obtain overall heat transfer coefficient (UA) for the heat exchanger as

VI. The temperature of the tube wall is constant for the analytical solutions.

methods give similar temperature distributions across the entire louvered fin.

4. Data reduction in a louvered fin heat exchanger

68 Heat Exchangers– Advanced Features and Applications

III. Thermophysical properties of both fluid are constant.

The average heat transfer rate can be expressed as

following equation for both fluid unmixed

rates of each fluid can be calculated with Eqs. (3) and (4)

ε ¼ 1−exp

where Q\_

where

IV. The louvered fins are attached to a mini-channel flat tube.

I. Cold flow is the external flow of the louvered fin heat exchanger. II. Hot flow is the internal flow of the louvered fin heat exchanger.

$$
\Delta UA = \dot{\mathbb{Q}} / \Delta T\_m \tag{9}
$$

ΔTm is the logarithmic mean temperature difference and that is

$$
\Delta T\_m = \frac{(T\_{h,i} - T\_{c,o}) - (T\_{h,o} - T\_{c,i})}{\ln \left( (T\_{h,i} - T\_{c,o}) / (T\_{h,o} - T\_{c,i}) \right)} \tag{10}
$$

The external (cold) side heat transfer coefficient (hc) can be obtained from the following equation by experimentally

$$\frac{1}{\eta\_c A\_c h\_t} = \frac{1}{\text{LIA}} - \frac{\delta\_t}{k\_t A\_t} - \frac{1}{A\_i h\_i} \tag{11}$$

hi is the internal side heat transfer coefficient, and it can be obtained using empirical relations for duct flow. The surface effectiveness (ηc) for a dry surface is

$$\eta\_c = 1 - \frac{A\_f}{A\_c} (1 - \eta\_f) \tag{12}$$

where ηf is the efficiency of the fin as given in Eq. (13)

$$\eta\_f = \frac{\tanh(ml)}{ml} \tag{13}$$

and

$$m = \sqrt{\frac{h\_c P\_f}{k\_f A\_{f,c}}}\tag{14}$$

Equation (14) can be expressed more explicitly using the following equation

$$m = \sqrt{\frac{2h\_c}{k\_f \delta} \left(1 + \frac{\delta}{F\_d}\right)}\tag{15}$$

For the calculation of external side heat transfer coefficient (hc) by analytically, the flow regime is very important to set up the analytical model. Therefore, Reynolds number is the mandatory parameter for the analytical solution. The flow can be assumed to be laminar at ReLp <1300 for the louvered fin arrays [3]. The characteristics length of louvered fin array is the louver pitch, so that the Reynolds number is calculated based on the louver pitch

$$Re\_{L\_p} = \frac{\mu\_{\max} L\_p}{\nu} \tag{16}$$

umax is the maximum velocity of the external fluid due to the narrowing section of the louvered fin arrays relatively to the inlet of the louvered fin. Therefore, the free velocity of the external fluid (u) at the inlet of the louvered fin is transformed to maximum velocity using the following equation

$$
\mu\_{\text{max}} = \mathfrak{u} F\_p / (F\_p - t) \tag{17}
$$

where Fp and t are the fin pitch and the material thickness, respectively.

If the tube wall temperature is assumed constant for the numerical analysis, the heat transfer can be calculated by the heat gain of the external (cold) fluid as given in Eq. (3). Thus, the heat transfer coefficient of the external side (hc) can be obtained from Eq. (18) by numerically

$$h\_{\mathfrak{c}} = \dot{\mathbb{Q}}\_{\mathfrak{c}} / (A \Delta T\_m) \tag{18}$$

In Eq. (18), A is the total external side heat transfer area and ΔTm is the logarithmic mean temperature difference under constant wall temperature condition given by Eq. (19) [11]

$$
\Delta T\_m = \frac{(T\_w - T\_{c,o}) - (T\_w - T\_{c,i})}{\ln \left( (T\_w - T\_{c,o}) / (T\_w - T\_{c,i}) \right)} \tag{19}
$$

#### 5. Performance evaluation criteria of the louvered fin heat exchangers

In the heat exchanger literature, some dimensionless parameters are used as a performance criteria. The commonly used thermal performance criteria are Stanton number and Colburn jfactor given as

$$St = \frac{h\_c}{\rho u c\_p} \tag{20}$$

$$j = StPr^{2/3} \tag{21}$$

respectively. After the calculation of hc by experimentally or analytically, Stanton number and Colburn j-factor can be obtained to indicate thermal performance of the louvered fin heat exchanger in a dimensionless form as given with Eqs. (20) and (21). Another performance criteria is the friction factor which is the dimensionless form of the pressure drop for the external side of a louvered fin heat exchanger expressed as

$$f = \left(\frac{A\_c}{A}\right) \left(\frac{2\Delta P}{\rho u^2}\right) \tag{22}$$

An alternative equation for the friction factor can be used by considering the entrance, exit and acceleration effects

$$f = \left(\frac{A\_c}{A}\right) \left(\frac{\rho\_m}{\rho\_1}\right) \left(\frac{2\rho\_1 \Delta P}{G\_c^2} - (k\_c + 1 - \sigma^2) \text{-} 2\left(\frac{\rho\_1}{\rho\_2} - 1\right) + (1 - \sigma^2 - k\_c) \frac{\rho\_1}{\rho\_2}\right) \tag{23}$$

where Ac is the minimum free flow area for the external side, and kc and ke are the coefficients of pressure loss at the inlet and the outlet of the heat exchanger. kc and ke can be evaluated according to Kays and London [2]. The overall performance of the louvered fin heat exchangers can be evaluated with another perspective. The ratio of the j-factor to the f, the ratio of the j-factor to the f 1/3 and JF are the overall performance criteria of the louvered fin heat exchangers used in the literature. j/f is known as "area goodness factor"[12, 13] and j/f 1/3 is known as "volume goodness factor"[6, 14, 15]. JF number which is related with the volume goodness factor can be obtained by Eq. (24) [16, 17]. These parameters are dimensionless numbers of the larger—the better characteristics. It is expected that these parameters can effectively evaluate the thermal and dynamic performance of a heat exchanger since it includes both the j- and the f-factor

fluid (u) at the inlet of the louvered fin is transformed to maximum velocity using the follow-

If the tube wall temperature is assumed constant for the numerical analysis, the heat transfer can be calculated by the heat gain of the external (cold) fluid as given in Eq. (3). Thus, the heat transfer coefficient of the external side (hc) can be obtained from Eq. (18) by numerically

In Eq. (18), A is the total external side heat transfer area and ΔTm is the logarithmic mean temperature difference under constant wall temperature condition given by Eq. (19) [11]

ΔTm ¼ ðTw−Tc, oÞ−ðTw−Tc,iÞ

5. Performance evaluation criteria of the louvered fin heat exchangers

In the heat exchanger literature, some dimensionless parameters are used as a performance criteria. The commonly used thermal performance criteria are Stanton number and Colburn j-

> St ¼ hc ρucp

respectively. After the calculation of hc by experimentally or analytically, Stanton number and Colburn j-factor can be obtained to indicate thermal performance of the louvered fin heat exchanger in a dimensionless form as given with Eqs. (20) and (21). Another performance criteria is the friction factor which is the dimensionless form of the pressure drop for the

An alternative equation for the friction factor can be used by considering the entrance, exit and

where Ac is the minimum free flow area for the external side, and kc and ke are the coefficients of pressure loss at the inlet and the outlet of the heat exchanger. kc and ke can be evaluated according to Kays and London [2]. The overall performance of the louvered fin heat

−ðkc þ 1−σ2

ρu2 � �

> Þ−2 ρ1 ρ2 −1 � �

!

f ¼ Ac A � � 2ΔP

external side of a louvered fin heat exchanger expressed as

ρ1

� � 2ρ1ΔP

G2 c ðTw−Tc, oÞ=ðTw−Tc,iÞ

hc ¼ Q\_

ln �

where Fp and t are the fin pitch and the material thickness, respectively.

umax ¼ uFp=ðFp−tÞ (17)

c=ðAΔTmÞ (18)

j ¼ StPr2=3 (21)

þ ð1−σ2

−keÞ ρ1 ρ2

� (19)

(20)

(22)

(23)

ing equation

70 Heat Exchangers– Advanced Features and Applications

factor given as

acceleration effects

f ¼ Ac A � � ρm

$$JF = \frac{\text{j}/\text{j}\_R}{\text{(}f/f\_R)^{1/3}}\tag{24}$$

where jR and fR are the reference values of Colburn j-factor and friction factor, respectively.

In light of these explanations, thermal and hydraulic characteristics of the heat exchangers with louvered fins are presented using numerical and experimental studies in the literature.

In 1990s, 2D numerical models were preferred rather than 3D models due to the run time and limited computing power. Nevertheless, 3D models are necessary because of the high compatibility with the experimental results. The velocity and the temperature field of a louvered fin heat exchanger for two different Reynolds numbers are presented in Figure 11 as a result of 2D numerical model.

It is observed that significant proportion of the air flows through the channels between the fins rather than between the louvers, as indicated by the presence of high velocity streaks in the channels at a Reynolds number of 100 (Figure 11a, b). The temperature of the air reach the fin temperature before it leaves the fin, therefore, the heat transfer performance of the second half of the fin is poor. In fact, second half of the fin only causes a pressure loss without any heat transfer at low Reynolds numbers. At a higher Reynolds number of 1600 (Figure 11c, d), the boundary layer of the louvers are much thinner, and therefore, the air is directed through the louver passages. A temperature difference is maintained between the air and the fin surface and so every part of the louvered fin contributes to the heat transfer. However, the 2D models is enough for the characteristics of the flow over the louvered fins, it is not possible to say same thing for the thermal performance. The comparison of 2D, 3D and the measured thermal and hydraulic performance of a louvered fin heat exchanger are presented in Figure 12.

It can be seen that the 2D model yields reasonably accurate predictions of friction factor, but poor predictions of Stanton number. An obvious way to identify the reasons of the error in the heat transfer is to consider the practical features which are missing from the 2-D model. Two important features which are missing are the tube surfaces and the resistance. The tube surfaces would add to the heat transfer area but would not add significantly to the overall heat transfer rate, because of the thick boundary layer growth on the tubes. The fin resistance would lower the temperature across the fin, and thus the heat transfer from the fin. Another reason of the over prediction of the thermal performance of the louvered fin is that the efficiency of the louvered fin cannot be calculated exactly. Generally, the experimental hc value is obtained using plate fin surface of the fin efficiency even for the louver fin efficiency due to the absence of the base area of the fin in 2D models. In the literature, 2-D models only consider

Figure 11. Computed velocity and temperature field for the 2-D model; Fp = 2.54 mm, Lp = 1.4 mm, Lα = 25.5°. (a) Velocity, ReLp = 100, (b) Temperature, ReLp = 100, (c) Velocity, ReLp = 1600, (d) Temperature, ReLp = 1600 [18].

Figure 12. Comparison of the computed 2-D model and measured friction factor and Stanton number: Fp = 2.05 mm, Lp = 1.4 mm, Lα = 25.5°, Tp = 11 mm and δ = 0.05 mm [18].

the cross section of the louvers and the numerical hc value is used directly without any fin efficiency formula. However, the slopes of the 2D numerical results are comparable and agree with the experimental results, heat transfer coefficient (hc) is overpredicted with the assumption of constant fin temperature and neglecting the tube surface effect [6, 18, 19]. It is these factors which led to the development of the 3D models.

In 2000s, 3D models have come to the forefront with the increasing computing power. Researchers have begun to compare 2D and 3D results with their own experimental results to validate the compatibility of the numerical models. In Figures 13 and 14, the variation of Colburn j-factor and the friction factor with respect to the Reynolds number for a louvered fin heat exchanger is presented. The results are also compared with correlations in the literature. It is observed that the CFD results for the 2D models are overpredicted by 80% compared to the experimental results [19]. This is consistent with the study of Atkinson et al. [18]. The slopes of the experimental results are comparable and agree well with the correlated data. Colburn jfactor and the friction factor decrease with the increasing of Reynolds number.

Figures 12–14 demonstrate the compatibility of the numerical results with experimental results and the effect of Reynolds number on the thermal and hydraulic performance of the louvered fin heat exchanger. In addition to the effect of Reynolds number, the researchers spent great efforts to determine the optimum geometric parameters of the louvered fin. The numerical studies have a great importance in this field, because the testing of the every geometric variation is very difficult in terms of both time and cost. The prior geometric parameter is the louver angle which has the significant influence on the flow regime over the louvered fins. The variation of the thermal performance of a louvered fin heat exchanger for different louver pitch

Figure 13. Comparison of computed and measured j-factor [19].

Figure 11. Computed velocity and temperature field for the 2-D model; Fp = 2.54 mm, Lp = 1.4 mm, Lα = 25.5°. (a) Velocity,

Figure 12. Comparison of the computed 2-D model and measured friction factor and Stanton number: Fp = 2.05 mm, Lp =

1.4 mm, Lα = 25.5°, Tp = 11 mm and δ = 0.05 mm [18].

72 Heat Exchangers– Advanced Features and Applications

ReLp = 100, (b) Temperature, ReLp = 100, (c) Velocity, ReLp = 1600, (d) Temperature, ReLp = 1600 [18].

Figure 14. Comparison of computed and measured f-factor [19].

with respect to the louver angle is demonstrated in Figure 15. It is observed that the thermal performance is increasing up to the louver angle of 28.5° and then decreasing for all the louver pitches. The louver angle of 28.5° has the maximum thermal performance within the considered cases of the numerical study. Average heat transfer coefficient is about 200 W/m2 K at the minimum louver pitch of 0.81 mm. It decreases about to 185 W/m2 K at the maximum louver pitch of 1.4 mm [20].

In the study of Atkinson et al. [18], the louvered fin has uniform louver angle. It can be possible to create a louvered fin having non-uniform louver angles as shown in Figure 16. Figure 17 shows the effect of non-uniform louver angle on the thermal and hydraulic performance of a louvered fin heat exchanger.

Figure 15. The effect of louver angle on the thermal performance of a louvered fin heat exchanger for different louver pitches [23].

Comprehensive Study of Heat Exchangers with Louvered Fins http://dx.doi.org/10.5772/66472 75

Figure 16. Five different cases of successively increased or decreased louver angle (+2o , +4o , −2o , −4o , and uniform angle 20o ) [24].

Figure 17. Effect of the non-uniform louver angle on the (a) Colburn j-factor and (b) friction factor [24].

with respect to the louver angle is demonstrated in Figure 15. It is observed that the thermal performance is increasing up to the louver angle of 28.5° and then decreasing for all the louver pitches. The louver angle of 28.5° has the maximum thermal performance within the consid-

In the study of Atkinson et al. [18], the louvered fin has uniform louver angle. It can be possible to create a louvered fin having non-uniform louver angles as shown in Figure 16. Figure 17 shows the effect of non-uniform louver angle on the thermal and hydraulic performance of a

Figure 15. The effect of louver angle on the thermal performance of a louvered fin heat exchanger for different louver

K at the

K at the maximum louver

ered cases of the numerical study. Average heat transfer coefficient is about 200 W/m2

minimum louver pitch of 0.81 mm. It decreases about to 185 W/m2

Figure 14. Comparison of computed and measured f-factor [19].

74 Heat Exchangers– Advanced Features and Applications

pitch of 1.4 mm [20].

pitches [23].

louvered fin heat exchanger.

In Figure 17, Colburn j-factor and the friction factor were normalized with Case E as shown in Figure 16. It is seen that the non-uniform louver angle patterns applied in the heat exchangers could effectively enhance the heat transfer performance. Case B has 18% heat transfer enhancement with respect to the Case E about at Re = 440. On the other hand, it has a negative effect of %19 on the friction factor.

In most cases, the geometric effects on the performance of a louvered fin heat exchanger are not monotonic. The combined relationship between the louver angle, louver pitch, fin pitch, tube pitch, etc., corrupts the linearity between the geometric parameters and the performance of the heat exchanger. An example is given with Figure 18. The variation of the heat transfer coefficient with respect to the frontal air velocity for different tube pitches is illustrated. It is observed that the heat transfer coefficient does not vary with the tube pitch linearly (Figure 18a). In Figure 18b, the effect of the fin pitch on the heat transfer coefficient is shown. It is seen that the heat transfer coefficient is increasing with decreasing of the fin pitch at a frontal velocity greater than 5.5 m/s. This statement is not valid for the frontal velocity smaller than 5.5 m/s.

Figure 18. Variation of the heat transfer coefficient with respect to the frontal velocity for different (a) tube pitches (Fp = 1.5 mm, Lp = 1.2 mm, Lα = 26o ) and (b) fin pitches (Tp = 9.6 mm, Lp = 1.2 mm, Lα = 26o ) [25].

Figure 19. Schematic of a wind tunnel test [10].

Researchers make great efforts to identify the real performances of the louvered fin heat exchangers by experimentally. Investigation of the performance of the louvered fins is commonly performed with the wind tunnel tests. In the open literature, several wind tunnel test can be found in different designs. A typical wind tunnel is shown in Figure 19.

As shown in Figure 19, internal fluid of the heat exchanger is water and it is regulated by a constant temperature bath. External fluid of the heat exchanger is air, and it is sucked by a fan and wind tunnel is placed in a constant temperature and humidity chamber to regulate the air flow. Dry and wet bulb temperatures of the air are measured with thermocouples at the inlet and the exit of the heat exchanger. One of the most comprehensive performance data of the louvered fin heat exchangers is presented by this wind tunnel test in the early of 2000s. The effects of the geometric dimensions of the louvered fins and the Reynolds number on the Colburn j-factor and friction factor is identified. Similarly to the previous studies, j-factor and f-factor are decreasing with the increasing of Reynolds number due to its definition as shown in Figure 20.

Comprehensive Study of Heat Exchangers with Louvered Fins http://dx.doi.org/10.5772/66472 77

Figure 20. Variations of j-factor and f-factor with respect to the louver angle and Reynolds number for (a) Fd = 16 mm and (b) Fd = 20 mm [10].

The effect of louver angle is more specifically at a flow depth of 20 mm for a constant fin pitch of 1.40 mm. Friction factor increases with the increasing of louver angle, however, the effect of the louver angle is diminishing for the louver angles larger than 21°. The effect of the louver angle on the j-factor varies with the flow depth. The increasing in the j-factor with the louver angle at a flow depth of 20 mm is more obvious than that of the flow depth of 16 mm. j-factor is increasing especially with the louver angle of greater than 23° due to the louver directed flow for such a small fin pitch of 1.40 mm.

The heat transfer and the pressure drop behaviour of the louvered fin heat exchangers for greater flow depths and Reynolds numbers is available in the open literature. The variations of the j-factor and f-factor with respect to the frontal air velocity for different geometric dimensions are given in Figure 21. As shown in Figure 21, the considered flow depth and Reynolds number range are 36.0–65.0 mm and 200–2500, respectively.

Researchers make great efforts to identify the real performances of the louvered fin heat exchangers by experimentally. Investigation of the performance of the louvered fins is commonly performed with the wind tunnel tests. In the open literature, several wind tunnel test

Figure 18. Variation of the heat transfer coefficient with respect to the frontal velocity for different (a) tube pitches (Fp =

) [25].

) and (b) fin pitches (Tp = 9.6 mm, Lp = 1.2 mm, Lα = 26o

As shown in Figure 19, internal fluid of the heat exchanger is water and it is regulated by a constant temperature bath. External fluid of the heat exchanger is air, and it is sucked by a fan and wind tunnel is placed in a constant temperature and humidity chamber to regulate the air flow. Dry and wet bulb temperatures of the air are measured with thermocouples at the inlet and the exit of the heat exchanger. One of the most comprehensive performance data of the louvered fin heat exchangers is presented by this wind tunnel test in the early of 2000s. The effects of the geometric dimensions of the louvered fins and the Reynolds number on the Colburn j-factor and friction factor is identified. Similarly to the previous studies, j-factor and f-factor are decreasing with the increasing of Reynolds number due to its definition as shown

can be found in different designs. A typical wind tunnel is shown in Figure 19.

in Figure 20.

1.5 mm, Lp = 1.2 mm, Lα = 26o

76 Heat Exchangers– Advanced Features and Applications

Figure 19. Schematic of a wind tunnel test [10].

In Figure 21a, c, the effect of fin pitch at a constant flow depth and fin height on the thermal and hydraulic performance is shown. It is observed that the fin pitch has a significant effect on the thermal and hydraulic performance and j-factor and f-factor are decreasing with the increasing of fin pitch. For Fp = 2.0 mm and Fd = 65 mm, Colburn j-factor is maximum for all Reynolds numbers and it decreases about 0.0105–0.0072 as shown in Figure 21a. The cause of this situation is that the hydraulic resistance against the flow increases when the fin pitch decreases at the flow passage. Therefore, the flow tends to more to being louver directed. As a result of this phenomenon, the air flow can be mixed well by the louvers, so the heat transfer and the pressure drop increase. As shown in Figure 21b, j-factor and f-factor increase when the fin height increases. The possible reason is that the proportion of the air flow directed by the louvers increases with the fin height. Figure 21d shows the effect of the flow depth on the jfactor and f-factor. It is obvious that the flow depth has more significant effect on the j-factor and f-factor. The study of Kim and Bullard [10] indicates the same results. In addition to the jfactor and f-factor, the variation of volume goodness factor denoted by j/f 1/3 versus Reynolds number is illustrated in Figure 22 as a performance criteria of the louvered fin heat exchangers.

Figure 21. Variations of j-factor and f-factor with respect to the frontal air velocity [15].

It is seen that the geometry which has the smallest flow depth (36.0 mm), smallest fin pitch (2.00 mm) and the biggest fin height (10.0 mm) has the maximum value of j/f 1/3 = 0.032. The

Figure 22. The variation of j/f1/3 [15].

Figure 23. The variation of j/f1/3 at low Reynolds number [6].

It is seen that the geometry which has the smallest flow depth (36.0 mm), smallest fin pitch

1/3 = 0.032. The

(2.00 mm) and the biggest fin height (10.0 mm) has the maximum value of j/f

Figure 21. Variations of j-factor and f-factor with respect to the frontal air velocity [15].

78 Heat Exchangers– Advanced Features and Applications

Figure 22. The variation of j/f1/3 [15].

effect of the Reynolds number to the j/f 1/3 ratio decreases with a flow depth of 65.0 mm. The most important result is the non-monotonic behaviour of the j/f 1/3 ratio with the geometric dimensions. The variation of the j/f 1/3 ratio has a complicated behaviour with respect to the fin pitch and the fin height. In particular, the low Reynolds number region which has the significant changes of j/f 1/3 ratio for the smaller flow depths can be illuminated with another study by Erbay et al. [6] as shown in Figure 23.

The j/f 1/3 ratios of the study of Erbay et al. [6] are obtained for a constant flow depth of 20 mm by numerically. It seen that the j/f 1/3 ratio for all the geometries has a similar trend with respect to the Reynolds number; however, there is not linear relationship for the geometric parameters. As a result, such a performance criteria which considers both the thermal and hydraulic performance is necessary to design a heat exchanger.

Some of the researches working on the performance evaluation of the louvered fin heat exchangers have developed correlations for Stanton number, Colburn j-factor and friction factor. The basic form of these correlations is

$$a = \mathbb{C}\_1 \mathrm{Re}^{\mathbb{C}\_2} \tag{25}$$

where a represents the performance criteria, and C1 and C2 are dependent on the dimensions of the louvered fin heat exchangers. Some of the correlations for the performance criteria of the louvered fin heat exchangers are listed by considering the studies in the open literature.

• Achaichia and Cowell [7], 150 < ReLp < 3000

$$St = 1.54 Re\_{L\_p}^{-0.57} \left(\frac{F\_p}{L\_p}\right)^{-0.19} \left(\frac{T\_p}{L\_p}\right)^{-0.11} \left(\frac{L\_h}{L\_p}\right)^{0.15} \tag{26}$$

$$f = \text{533.42Re}\_{L\_p}^{0.318(\log \text{Re}\_p - 2.25)} F\_p^{0.22} L\_p^{0.25} T\_p^{0.26} L\_h^{0.33} \,. \tag{27}$$

• Kim and Bullard [10], 100 < ReLp < 600

$$j = R e\_{L\_p}^{-0.487} \left(\frac{L\_\alpha}{90}\right)^{0.257} \left(\frac{F\_p}{L\_p}\right)^{-0.13} \left(\frac{F\_h}{L\_p}\right)^{-0.29} \left(\frac{F\_d}{L\_p}\right)^{-0.235} \left(\frac{L\_h}{L\_p}\right)^{0.68} \left(\frac{T\_p}{L\_p}\right)^{-0.279} \left(\frac{\delta}{L\_p}\right)^{-0.05} \tag{28}$$

$$f = Re\_{L\_p}^{-0.781} \left(\frac{L\_a}{90}\right)^{0.444} \left(\frac{F\_p}{L\_p}\right)^{-1.682} \left(\frac{F\_h}{L\_p}\right)^{-1.22} \left(\frac{F\_d}{L\_p}\right)^{0.818} \left(\frac{L\_h}{L\_p}\right)^{1.97}.\tag{29}$$

• Dong et al. [15], 200 < ReLp < 2500

$$j = 0.26712 Re\_{L\_p}^{-0.1944} \left(\frac{L\_a}{90}\right)^{0.257} \left(\frac{F\_p}{L\_p}\right)^{-0.5177} \left(\frac{F\_h}{L\_p}\right)^{-1.9045} \left(\frac{F\_d}{L\_p}\right)^{-0.2147} \left(\frac{L\_h}{L\_p}\right)^{1.7159} \left(\frac{\delta}{L\_p}\right)^{-0.05} \tag{30}$$

$$f = 0.54486 Re\_{L\_{\eta}}^{-0.3068} \left(\frac{L\_{\alpha}}{90}\right)^{0.444} \left(\frac{F\_{p}}{L\_{\eta}}\right)^{-0.9925} \left(\frac{F\_{h}}{L\_{\eta}}\right)^{-0.5458} \left(\frac{F\_{d}}{L\_{\eta}}\right)^{-0.0688} \left(\frac{L\_{h}}{L\_{\eta}}\right)^{-0.2003} \tag{31}$$

• Ryu and Lee [26], 100 < ReLp <3000

$$j = \text{Re}\_{L\_p}^{(-0.484 - 1.887/\ln \text{Re}\_{L\_p})} \left(\frac{F\_d}{L\_p}\right)^{0.157} \left(2.24 - 0.588 \ln \left(\frac{F\_p}{L\_p \sin L\_d}\right)\right) \tag{32}$$

$$f = Re\_{L\_p}^{-0.433} \left(\frac{F\_d}{L\_p}\right)^{0.185} \left(1.10 + 4.31 \left(\frac{L\_a}{90}\right)^2 + 0.836 \frac{\ln(F\_p/L\_p)}{\left(F\_p/L\_p\right)^2}\right). \tag{33}$$

In addition to above correlations, a large data bank as shown in Table 1 was used by Chang and Wang [20], Chang et al. [22], and Park and Jacobi [27] to develop a more sensible correlations for j-factor and f-factor. These correlations which are the more comprehensive for the louvered fin heat exchangers are listed below.

• Chang and Wang [20], 100 < ReLp < 3000

$$j = R \bar{e}\_{L\_p}^{-0.49} \left(\frac{L\_a}{90}\right)^{0.27} \left(\frac{F\_p}{L\_\rho}\right)^{-0.14} \left(\frac{F\_h}{L\_\rho}\right)^{-0.29} \left(\frac{T\_d}{L\_\rho}\right)^{-0.23} \left(\frac{L\_h}{L\_\rho}\right)^{0.68} \left(\frac{T\_p}{L\_\rho}\right)^{-0.28} \left(\frac{\delta}{L\_\rho}\right)^{-0.05}.\tag{34}$$

• Chang et al. [22], 100 < ReLp < 3000

• Achaichia and Cowell [7], 150 < ReLp < 3000

80 Heat Exchangers– Advanced Features and Applications

• Kim and Bullard [10], 100 < ReLp < 600

Lα 90

f ¼ Re−0:781 Lp

• Dong et al. [15], 200 < ReLp < 2500

Lp

f ¼ 0:54486Re−0:3068

• Ryu and Lee [26], 100 < ReLp <3000

f ¼ Re−0:433 Lp

louvered fin heat exchangers are listed below.

• Chang and Wang [20], 100 < ReLp < 3000

Lα 90

• Chang et al. [22], 100 < ReLp < 3000

� �0:27 Fp

Lp

� �−0:14 Fh

Lp

� �−0:29 Td

Lp

� �−0:23 Lh

Lp

� �0:68 Tp

Lp

� �−0:28 δ

Lp � �−0:05

j ¼ Re−0:49 Lp

� �0:257 Fp

Lα 90

Lp

� �0:257 Fp

j ¼ Reð−0:484−1:887=lnReLp Þ Lp

> Fd Lp � �0:185

Lp

Lα 90

� �−0:13 Fh

� �0:444 Fp

Lp

� �0:444 Fp

Lα 90 Lp

Lp

� �−0:5177 Fh

Lp

Fd Lp � �0:157

� �−0:29 Fd

� �−1:682 Fh

Lp

� �−0:9925 Fh

1:10 þ 4:31 Lα

In addition to above correlations, a large data bank as shown in Table 1 was used by Chang and Wang [20], Chang et al. [22], and Park and Jacobi [27] to develop a more sensible correlations for j-factor and f-factor.

Table 1. Geometrical dimensions of the louvered fin heat exchangers in the database [20, 27].

$$f = f\_1 f\_2 f\_3 \tag{35}$$

for ReLp <150

$$f\_1 = 14.39 \text{Re}\_{L\_p}^{\left(-0.805 \frac{F\_p}{L\_p}\right)} \left(\log\_\varepsilon \left(1.0 + \left(\frac{F\_p}{L\_p}\right)\right)\right)^{3.04} \tag{36}$$

$$f\_2 = \left(\log\_{\epsilon}\left(\left(\frac{\delta}{F\_p}\right)^{0.48} + 0.9\right)\right)^{-1.435} \left(\frac{D\_h}{L\_p}\right) (\log\_{\epsilon}(0.5 \text{Re}\_{L\_p}))^{-3.01} \tag{37}$$

#### Comprehensive Study of Heat Exchangers with Louvered Fins http://dx.doi.org/10.5772/66472 85

$$f\_3 = \left(\frac{F\_p}{L\_h}\right)^{-0.308} \left(\frac{F\_d}{L\_h}\right)^{-0.308} \left(e^{-0.1167 \frac{\tau\_p}{D\_{\rm tr}}}\right) L\_\alpha^{0.35} \tag{38}$$

for 150 < ReLp <5000

$$f\_1 = 4.97 Re\_{L\_p}^{0.6049 - 1.064/L\_x^{0.2}} \left( \log\_\varepsilon \left( \left( \frac{\delta}{F\_p} \right)^{0.5} + 0.9 \right) \right)^{-0.527} \tag{39}$$

$$f\_2 = \left(\left(\frac{D\_h}{L\_p}\right) \log\_e(0.3 \text{Re}\_{L\_p})\right)^{-2.966} \left(\frac{F\_p}{L\_h}\right)^{-0.7931 \frac{V\_p}{T\_h}}\tag{40}$$

$$f\_3 = \left(\frac{T\_p}{D\_m}\right)^{-0.0446} \log\_e \left(1.2 + \left(\frac{L\_p}{F\_p}\right)^{1.4}\right)^{-3.553} L\_a^{-0.477}.\tag{41}$$

• Park and Jacobi [27], 27 < ReLp < 4132

$$\begin{array}{l} j\_{cor} = 0.872 j\_{Re} j\_{low} j\_{lower} L\_{\alpha}^{0.219} N\_{LB}^{-0.0881} \left( \frac{r\_h}{L\_p} \right)^{0.149} \left( \frac{F\_d}{F\_p} \right)^{-0.259} \left( \frac{L\_h}{F\_h} \right)^{0.54} \\\ \times \left( \frac{F\_h}{F\_p} \right)^{-0.902} \left( 1 - \frac{\delta}{L\_p} \right)^{2.62} \left( \frac{L\_p}{F\_p} \right)^{0.301} \end{array} \tag{42}$$

where

$$j\_{Re} = \text{Re}\_{L\_p}^{[-0.458 - 0.00874 \cosh(F\_p/L\_p - 1)]} \tag{43}$$

$$j\_{low} = 1 - \sin\left(\frac{L\_p}{F\_p} L\_a \right) \left[ \cos h \left( 0.049 Re\_{L\_p} - 0.142 \frac{F\_d}{N\_{LB}} \right) \right]^{-1} \tag{44}$$

$$j\_{lower} = 1 - (-0.0065 \tan L\_{it}) \left(\frac{F\_d}{N\_{LB} F\_p}\right) \cos \left[2\pi \left(\frac{F\_p}{L\_p \tan L\_{\alpha}} - 1.8\right)\right] \tag{45}$$

$$f\_{av} = 3.69 f\_{Re} N\_{LB}^{-0.256} \left(\frac{F\_p}{L\_p}\right)^{0.904} \sin\left(L\_a + 0.2\right) \left(1 - \frac{F\_h}{T\_p}\right)^{0.733} \times \left(\frac{L\_h}{F\_h}\right)^{0.648} \left(\frac{\delta}{L\_p}\right)^{-0.647} \left(\frac{F\_h}{F\_p}\right)^{0.799} \tag{46}$$

where

f ¼ f 1f 2f 3 (35)

ðlogeð0:5ReLp ÞÞ−3:01 (37)

(36)

Fp Lp

� � � � � � 3:04

Dh Lp � �

for ReLp <150

f 1 ¼ 14:39Re −0:805Fp

δ Fp � �0:48

f 2 ¼ loge

by R. L. Webb considered by Chang and Wang [20].

Source Lp(mm) Fp(mm) Fh(mm) Lh(mm) Lα(

84 Heat Exchangers– Advanced Features and Applications

o

KB(10)b [10] 1.70 1.40 8.15 6.40 27.0 24.0 – 10.15 0.10 2 KB(11)b [10] 1.70 1.40 8.15 6.40 29.0 24.0 – 10.15 0.10 2 KB(12)b [10] 1.70 1.10 8.15 6.40 23.0 20.0 – 10.15 0.10 2 KB(13)b [10] 1.70 1.10 8.15 6.40 23.0 24.0 – 10.15 0.10 2 KB(14)b [10] 1.70 1.20 8.15 6.40 23.0 20.0 – 10.15 0.10 2 KB(15)b [10] 1.70 1.20 8.15 6.40 23.0 24.0 – 10.15 0.10 2 KYL(1)b [14] 2.90 2.82 16.50 12.50 20.0 44.0 – 21.20 0.15 2 KYL(2)b [14] 2.90 2.42 16.50 12.50 20.0 44.0 – 21.20 0.15 2 KYL(3)b [14] 2.90 2.03 16.50 12.50 20.0 44.0 – 21.20 0.15 2 KYL(4)b [14] 2.90 2.82 16.50 12.50 25.0 44.0 – 21.20 0.15 2 KYL(5)b [14] 2.90 2.42 16.50 12.50 25.0 44.0 – 21.20 0.15 2 KYL(6)b [14] 2.90 2.03 16.50 12.50 25.0 44.0 – 21.20 0.15 2 KYL(7)b [14] 2.90 2.82 16.50 12.50 30.0 44.0 – 21.20 0.15 2 KYL(8)b [14] 2.90 2.42 16.50 12.50 30.0 44.0 – 21.20 0.15 2 KYL(9)b [14] 2.90 2.03 16.50 12.50 30.0 44.0 – 21.20 0.15 2 KYL(10)b [14] 2.90 2.82 16.50 12.50 35.0 44.0 – 21.20 0.15 2 KYL(11)b [14] 2.90 2.42 16.50 12.50 35.0 44.0 – 21.20 0.15 2 KYL(12)b [14] 2.90 2.03 16.50 12.50 35.0 44.0 – 21.20 0.15 2

) Fd(mm) Td(mm) Tp(mm) Δ(mm) NLB

Fh � �

þ 0:9

! ! −1:435

Table 1. Geometrical dimensions of the louvered fin heat exchangers in the database [20, 27].

Lp loge 1:0 þ

a Correlated data considered by Chang and Wang [20].b Correlated data considered by Park and Jacobi [27].c Park and Jacobi [27] used half of these pitches because of two fin stocks and a splitter plate between the tubes.d Park and Jacobi [27] and Chang and Wang [20] assumed that the tube diameter is 1.50 mm due to the lack of information.e Chang and Wang [20] assumed that the tube diameter is 5.00 mm due to the lack of information.f Correlated data which was unpublished

$$f\_{R\varepsilon} = \left(\text{Re}\_r \frac{F\_p}{L\_p}\right)^{-0.845} + 0.0013 \text{Re}\_{L\_p}^{[1.26(\delta/F\_p)]} \tag{47}$$

However, the correlations of Stanton number, Colburn j-factor and friction factor are defined for a large range of Reynolds number and geometric descriptions for heat exchangers with multi-louvered fins, it is necessary that the performance of every new type of heat exchanger is analysed individually due to the complexity of the combined effects of geometrical and operational parameters [33].


**3. Probiotics**

Bacterial concentrations in HBM range between 102 and 104 ufc/mL. This means that an infant ingesting over 800 ml of milk a day would receive 105 to 107 ufc [14]. Therefore, HBM is a primary source of commensal and probiotic bacteria to the infant and plays a key role in the initial colonization of the gut. Some bacteria isolated from HBM have proven to have immunomodulatory and anti-infective effects. Therefore, the protective effects of HBM may be conferred by these bacteria. Supplementation of infant formulae with probiotic bacteria isolated from HBM could help improve gut microbial balance in formula-fed infants, thereby mimicking the beneficial effects of HBM.

Evidence has been published that probiotics modulate mucosal and systemic immune function, improve intestinal barrier function, and exert metabolic effects on the host [4]. Some of the lactobacillus strains isolated from HBM [15] have been reported to compete with enteropathogenic bacteria for nutrients and epithelium

**5**

newborns [28].

months [19].

*Probiotics and Prebiotics in Infant Formulae DOI: http://dx.doi.org/10.5772/intechopen.88609*

supplementation periods.

and no adverse effects were detected [24].

*3.1.2 Prevention and treatment of infant disorders*

*3.1.1 Safety*

adhesion and improve gut barrier functions. The ability of lactobacillus and bifidobacteria strains to stabilize the integrity of gut barrier has been demonstrated [16]. These types of bacteria potentially reduce antigen systemic load and influence immune function via enterocytes, antigen-presenting cells (monocytes and den-

European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) Committee on Nutrition [19] published a systematic review of studies assessing the safety and health effects of probiotic-supplemented infant formulae. No conclusive data were obtained from ESPGHAN's analysis of infant and follow-on formulae due to considerable variability in the type and dose of probiotics used and

Formulae supplemented with probiotics do not raise safety concerns with regard to growth and adverse effects [19]. There are sufficient data supporting the safety of probiotics for infants older than 6 months. However, data on the use of probiotic supplementation in infants younger than 4 months are more limited. Studies in breastfed infants younger than 6 months who received a formula supplemented with either *Lactobacillus fermentum* CECT5716 or *Lactobacillus rhamnosus* GG revealed that formulae were well tolerated and had no adverse effects on growth either during the study period or at 3–5 years of age [20–23]. A recent study revealed that growth and food tolerance improved in premature infants >30 weeks of gestational age fed with a formula supplemented with *Saccharomyces boulardii,*

Conflicting results have been obtained regarding the effects of probiotics on the composition of fecal microbiota. A decrease in bifidobacteria and enterobacteria concentrations has been reported with respect to controls [25, 26]. Also, no differences have been observed in lactobacillus and bacteroides. By contrast, Maldonado et al. [27] reported an increase in fecal bifidobacteria and lactobacilli concentrations in infants fed with a formula supplemented with *Lactobacillus fermentum* CECT 5716. Also, no differences were found in other bacteria strains. Evidence has been provided that a formula containing *Bifidobacterium lactis* can influence the composition, stability, and function of gut microbiota in low-weight

The literature reports that probiotic supplementation of formula beyond early infancy can produce a decrease in the use of antibiotics and incidence of diarrhea, colic, and/or irritability. Yet, the variety of methods, type and dose of probiotics, and duration of interventions hinders that conclusive data can be obtained on clear clinical effects of probiotic-supplemented formulae in infants younger than 4

In general, there is no consistent evidence supporting that supplementation of follow-on formula with probiotics has protective effects against infectious diarrhea [19]. Yet, a reduction has been reported in the duration and number of episodes of diarrhea associated with the use of probiotic-supplemented formulae [27, 29–31]. A systematic review conducted by Mugambi et al. [32] of controlled, randomized trials did not reveal that supplementation had any effects on infectious

dritic cells), regulatory T cells, and effector T and B cells [17, 18].

**3.1 Infant formula supplemented with probiotics**

#### *Probiotics and Prebiotics in Infant Formulae DOI: http://dx.doi.org/10.5772/intechopen.88609*

adhesion and improve gut barrier functions. The ability of lactobacillus and bifidobacteria strains to stabilize the integrity of gut barrier has been demonstrated [16]. These types of bacteria potentially reduce antigen systemic load and influence immune function via enterocytes, antigen-presenting cells (monocytes and dendritic cells), regulatory T cells, and effector T and B cells [17, 18].