**5. Conclusion**

Disaster management is challenged by the difficulty we have as people and organizations to think about future, uncertain events. The complexity and chaos of disasters further complicate the tasks of planning, preparing, and responding. The more complex the event, the more an organization must adapt and collaborate with other organizations. This frameworks of resource management in disasters will guide organizations in their disaster preparedness activities. We have touched on some applications of these principles to hospitals and resource-poor environments. From an accurate understanding of what constitutes a disaster, education and training will more likely be effective — directed to the right people, developing the right skills in the right places.

**15**

**Author details**

Jared Bly1,2\*, Louis Hugo Francescutti1

1 University of Alberta, Edmonton, Canada

2 Royal Roads University, Victoria, Canada

provided the original work is properly cited.

\*Address all correspondence to<EMAIL_ADDRESS>
3 Northern Alberta Institute of Technology, Edmonton, Canada

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

and Danielle Weiss3

*Disaster Management: A State-of-the-Art Review DOI: http://dx.doi.org/10.5772/intechopen.94489*

*Disaster Management: A State-of-the-Art Review DOI: http://dx.doi.org/10.5772/intechopen.94489*

*Natural Hazards - Impacts, Adjustments and Resilience*

• *Who is the exercise intended to benefit?*

• *Is training for emergency or disaster?*

• *Is the possibility of psychological effects addressed?*

• *Is collaboration being trained in disaster exercises?*

• *Is there an adequate and effective debriefing?*

• *Is the exercise overly complex?*

• *Are there clear objectives?*

*Questions to ask to make disaster training effective.*

exercise increases with reflection individually and collectively [21, 44, 51]. The utility of an effective and adequate debrief cannot be underemphasized (**Table 1**).

*He was just shaking his head. "Forget this dream and it might as well be three days till the next one. Be the same dream all over again unless you keep this one in*

Disaster management is challenged by the difficulty we have as people and organizations to think about future, uncertain events. The complexity and chaos of disasters further complicate the tasks of planning, preparing, and responding. The more complex the event, the more an organization must adapt and collaborate with other organizations. This frameworks of resource management in disasters will guide organizations in their disaster preparedness activities. We have touched on some applications of these principles to hospitals and resource-poor environments. From an accurate understanding of what constitutes a disaster, education and training will more likely be effective — directed to the right people, developing the right

*see another one like that for a hundred years."*

*mind."*

**Table 1.**

**5. Conclusion**

skills in the right places.

*Seems like a dream. A dream I'd like to forget. I said as much to Raj, adding "won't*

**14**


[62] Aguilar G, Svaasand LO, Nelson JS. Effects of hypobaric pressure on human skin: Feasibility study for port wine stain laser therapy (part I). Lasers in Surgery and Medicine.

[63] Childers MA, Franco W, Nelson JS, Aguilar G. Laser surgery of port wine stains using local vacuum pressure: Changes in skin morphology and optical properties (part I).

[64] Zhou Z-F, Wang R, Chen B, Yang T, Wang G-X. Heat transfer characteristics during pulsed spray cooling with R404A at different spray distances and back pressures.

[65] Wang XS, Chen B, Zhou ZF. Atomization and surface heat transfer characteristics of cryogen spray cooling with expansion-chambered nozzles. International Journal of Heat

Mechanical Engineering Congress & Exposition Proceedings. 2014. pp. 673-681

skin. Journal of Biomedical Optics. 2006;**11**:041116

Lasers in Surgery and Medicine. 2007;**39**:108-117

Applied Thermal Engineering. 2016;**102**:813-821

and Mass Transfer. 2018;**121**:15-27

on in vitro model human skin. Lasers in Medical Science. 2005;**20**:80-86

2004;**34**:146-154

2014;**73**:1489-1500

Conference. 2014

2018;**69**:595-601

2005;**36**:124-129

Medicine. 2005;**36**:130-135

[54] Tuqan AT, Kelly KM, Aguilar G, Ramirez-San-Juan JC, Sun CH, Cassarino D, Derienzo D, Barr RJ, Nelson JS. Evaluation of single versus multiple cryogen spray cooling spurts on in vitro model human skin. Lasers in Medical Science. 2005;**20**:80-86

[39] Tunnell JW, Torres JH, Anvari B. Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling. Annals of Biomedical Engineering. 2002;**30**:19-33

[40] Jia W, Aguilar G, Wang GX, Nelson JS. Heat-transfer dynamics during cryogen spray cooling of substrate at different initial temperatures. Physics in Medicine and Biology.

[41] Aguilar G, Vu H, Nelson JS. Influence of angle between the nozzle and skin surface on the heat flux and overall heat extraction during cryogen spray cooling. Physics in

[42] Franco W, Liu J, Romero-Mendez R, Jia W, Nelson JS, Aguilar G. Extent of lateral epidermal protection afforded by a cryogen spray against laser irradiation. Lasers in Surgery

[43] Franco W, Liu J, Wang GX, Nelson JS, Aguilar G. Radial and temporal variations in surface heat transfer during cryogen spray cooling. Physics in Medicine and Biology.

[44] Wang R, Zhou Z, Chen B, Bai F, Wang G. Surface heat transfer characteristics of R404A pulsed spray cooling with an expansion-chambered nozzle for laser dermatology.

[45] Zhou Z, Chen B, Wang Y, Guo L, Wang G. An experimental study on pulsed spray cooling with refrigerant R-404a in laser surgery. Applied Thermal Engineering. 2012;**39**:29-36

[46] Tian J-m, Chen B, Zhou Z-f. Methodology of surface heat flux estimation for 2D multilayer mediums. International Journal of Heat and Mass Transfer. 2017:675-687

[47] Aguilar G, Wang GX, Nelson JS. Dynamic behavior of cryogen spray cooling: Effects of spurt duration and spray distance. Lasers in Surgery and Medicine. 2003;**32**:152-159

[48] Majaron B, Kimel S, Verkruysse W, Aguilar G, Pope K, Svaasand LO, Lavernia EJ, Nelson JS. Cryogen spray cooling in laser dermatology: Effects of ambient humidity and frost

[49] Ramirez-San-Juan JC, Choi B, Franco W, Nelson JS, Aguilar G. Effect of ambient humidity on light transmittance through skin phantoms during cryogen spray cooling. Physics

[50] Vu H, Aguilar G, Stuart Nelson J. Passive mass deposition control of cryogen sprays through the use of wire meshes. Lasers in Surgery and Medicine. 2004;**34**:329-334 [51] Majaron B, Svaasand LO, Aguilar G, Nelson JS. Intermittent cryogen spray cooling for optimal heat extraction during dermatologic laser treatment. Physics in Medicine and

[52] Basinger B, Aguilar G, Nelson JS. Effect of skin indentation on heat transfer during cryo-

[53] Tian JM, Chen B, Li D, Zhou ZF. Transient spray cooling: Similarity of dynamic heat flux for different cryogens, nozzles and substrates. International Journal of Heat and Mass

gen spray cooling. Lasers in Surgery and Medicine. 2004;**34**:155-163

2004;**49**:5295-5308

120 Advanced Cooling Technologies and Applications

2005;**50**:387-397

Medicine and Biology. 2004;**49**:N147-N153

International Journal of Refrigeration. 2015;**60**:206-216

formation. Lasers in Surgery and Medicine. 2001;**28**:469-476

in Medicine and Biology. 2006;**51**:113-120

Biology. 2002;**47**:3275-3288

Transfer. 2017;**108**:561-571

and Medicine. 2007;**39**:414-421

**Chapter 8**

**Provisional chapter**

**Water as a Refrigerant in Centrifugal Compressor**

**Water as a Refrigerant in Centrifugal Compressor**

DOI: 10.5772/intechopen.79614

As a consequence of the F-gas regulation R404A is no longer a viable option for commercial refrigeration applications. Therefore, this paper focuses on natural refrigerants. There are a few alternatives like carbon dioxide, which has an efficiency loss with increasing environment temperatures. A promising option is the combination of a carbon dioxide process with a chiller using water as refrigerant. Two types of interconnection seem to make energy sense. On the one hand, the interconnection as a cascade, whereby the complete heat of condensation is given off to the water chiller, on the other hand the

**Keywords:** refrigeration, water, carbon dioxide cascade, subcooling, vapor compression,

The F-gas regulation, which came into force on January 1, 2015, envisages an EU-wide phase-

erence value based on the annual average of the quantities of hydrofluorocarbons, a producer or importer reported to have placed in the market between 2009 and 2012. From January 1, 2020, the next step will be a ban of placing refrigeration appliances for commercial use with HFCs with GWP > 2500 [1]. As a result, the refrigerant blend R404A may no longer be used in

and finally, the annual COP values are compared with the standard systems.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

equivalent of hydrofluorocarbons (HFCs) by 79% by 2030 compared to a ref-

after the gas cooler. Both types of interconnection result in

process. These are examined more closely,

**Cooling Systems for Industrial Applications**

**Cooling Systems for Industrial Applications**

Florian Hanslik and Juergen Suess

Florian Hanslik and Juergen Suess

http://dx.doi.org/10.5772/intechopen.79614

subcooling of transcritical CO2

chiller, energy efficiency

new systems from this point in time.

**1. Introduction**

down of the CO2

optimized operating parameters for the CO2

**Abstract**

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

#### **Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications**

DOI: 10.5772/intechopen.79614

Florian Hanslik and Juergen Suess Florian Hanslik and Juergen Suess

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.79614

#### **Abstract**

As a consequence of the F-gas regulation R404A is no longer a viable option for commercial refrigeration applications. Therefore, this paper focuses on natural refrigerants. There are a few alternatives like carbon dioxide, which has an efficiency loss with increasing environment temperatures. A promising option is the combination of a carbon dioxide process with a chiller using water as refrigerant. Two types of interconnection seem to make energy sense. On the one hand, the interconnection as a cascade, whereby the complete heat of condensation is given off to the water chiller, on the other hand the subcooling of transcritical CO2 after the gas cooler. Both types of interconnection result in optimized operating parameters for the CO2 process. These are examined more closely, and finally, the annual COP values are compared with the standard systems.

**Keywords:** refrigeration, water, carbon dioxide cascade, subcooling, vapor compression, chiller, energy efficiency

#### **1. Introduction**

The F-gas regulation, which came into force on January 1, 2015, envisages an EU-wide phasedown of the CO2 equivalent of hydrofluorocarbons (HFCs) by 79% by 2030 compared to a reference value based on the annual average of the quantities of hydrofluorocarbons, a producer or importer reported to have placed in the market between 2009 and 2012. From January 1, 2020, the next step will be a ban of placing refrigeration appliances for commercial use with HFCs with GWP > 2500 [1]. As a result, the refrigerant blend R404A may no longer be used in new systems from this point in time.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A current alternative is HFC or HFO replacement, but in most cases, they are only seen as a temporary solution. A long-term alternative is natural refrigerant. Water stands out as a natural refrigerant because it has no GWP or ODP and is neither flammable nor toxic. When used in a refrigeration system, it occurs in the liquid and gaseous states. The thermodynamic process takes place in a rough vacuum due to the vapor pressure curve of water but then corresponds to the cycle of conventional refrigeration systems.

In addition to the necessary operation in a rough vacuum, **Figures 2** and **3** show the low volumetric cooling capacity and the high required pressure ratio of water as a refrigerant

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

125

Both properties require an optimal compressor concept as well as optimum flow control of the water vapor, as this is the only way to minimize the possible losses and to use the advantages

The curves of the respective refrigerants in **Figures 1**–**3** were calculated using REFPROP [4].

Up to now, quite a few centrifugal chillers were built with R718 as working fluid. In **Table 1** the most relevant projects are listed. The cooling capacity of the majority of the machines is typically above 500 kW, and all machines use centrifugal compressors with the exception of the chiller described by reference [5]. Here, a positive displacement compressor of the Roots blower type is applied. The centrifugal compressors are either of the axial type with up to seven stages or use radial impeller designs with typically two stages. In most machines intercooling between the stages is realized, as water vapor has a rather high discharge temperature due to its large polytropic index of approximately 1.33 in the operational range of the com-

While R718 as refrigerant is state of the art in absorption chillers with lithium bromide as absorbent, none of the mechanical water vapor compression machines shown in **Table 1** have reached a commercially viable status so far, and their market penetration is still pending. According to Ophir [6], only IDE Technologies which is an Israelian water desalination company has successfully built and commissioned a significant number of installations in the

field, which still cannot be regarded as industrialized mass-produced machines [3].

compared to conventional refrigerants.

of water as a refrigerant efficiently.

pressor [3].

**2.2. Compressor cooling systems for the refrigerant water**

**Figure 2.** Volumetric cooling capacities of selected refrigerants.

In this chapter, the properties of water as a refrigerant are considered in more detail, an overview of previously implemented systems is given, and the mode of operation and special features of such a system are explained. Using examples, the promising field of applications gets defined, and the efficiency of the systems is shown.

#### **2. Water as refrigerant**

#### **2.1. The thermodynamic properties of water**

Water (R718) as a refrigerant is one of the oldest fluids being used for refrigeration applications down to about the freezing point. When water is coupled with protective solutions to prevent freezing (i.e., propylene or ethylene glycol), it can also be used well below water's normal freezing point in applications such as ice slurries. Water is easily available and has excellent thermodynamics and chemical properties. It was found by reference [2] that for evaporator temperatures above 20°C R718 gives the highest COP of all refrigerants assuming exactly the same cycle parameters [3].

**Figure 1** shows the vapor pressure curves of various refrigerants. In the case of R718, it is noticeable that the pressures in the temperature range for a typical cooling application in server rooms are between 10 and 100 mbar.

**Figure 1.** Vapor pressure curves of selected refrigerants.

In addition to the necessary operation in a rough vacuum, **Figures 2** and **3** show the low volumetric cooling capacity and the high required pressure ratio of water as a refrigerant compared to conventional refrigerants.

Both properties require an optimal compressor concept as well as optimum flow control of the water vapor, as this is the only way to minimize the possible losses and to use the advantages of water as a refrigerant efficiently.

The curves of the respective refrigerants in **Figures 1**–**3** were calculated using REFPROP [4].

#### **2.2. Compressor cooling systems for the refrigerant water**

A current alternative is HFC or HFO replacement, but in most cases, they are only seen as a temporary solution. A long-term alternative is natural refrigerant. Water stands out as a natural refrigerant because it has no GWP or ODP and is neither flammable nor toxic. When used in a refrigeration system, it occurs in the liquid and gaseous states. The thermodynamic process takes place in a rough vacuum due to the vapor pressure curve of water but then

In this chapter, the properties of water as a refrigerant are considered in more detail, an overview of previously implemented systems is given, and the mode of operation and special features of such a system are explained. Using examples, the promising field of applications

Water (R718) as a refrigerant is one of the oldest fluids being used for refrigeration applications down to about the freezing point. When water is coupled with protective solutions to prevent freezing (i.e., propylene or ethylene glycol), it can also be used well below water's normal freezing point in applications such as ice slurries. Water is easily available and has excellent thermodynamics and chemical properties. It was found by reference [2] that for evaporator temperatures above 20°C R718 gives the highest COP of all refrigerants assuming

**Figure 1** shows the vapor pressure curves of various refrigerants. In the case of R718, it is noticeable that the pressures in the temperature range for a typical cooling application in

corresponds to the cycle of conventional refrigeration systems.

gets defined, and the efficiency of the systems is shown.

**2.1. The thermodynamic properties of water**

exactly the same cycle parameters [3].

server rooms are between 10 and 100 mbar.

**Figure 1.** Vapor pressure curves of selected refrigerants.

**2. Water as refrigerant**

124 Advanced Cooling Technologies and Applications

Up to now, quite a few centrifugal chillers were built with R718 as working fluid. In **Table 1** the most relevant projects are listed. The cooling capacity of the majority of the machines is typically above 500 kW, and all machines use centrifugal compressors with the exception of the chiller described by reference [5]. Here, a positive displacement compressor of the Roots blower type is applied. The centrifugal compressors are either of the axial type with up to seven stages or use radial impeller designs with typically two stages. In most machines intercooling between the stages is realized, as water vapor has a rather high discharge temperature due to its large polytropic index of approximately 1.33 in the operational range of the compressor [3].

While R718 as refrigerant is state of the art in absorption chillers with lithium bromide as absorbent, none of the mechanical water vapor compression machines shown in **Table 1** have reached a commercially viable status so far, and their market penetration is still pending. According to Ophir [6], only IDE Technologies which is an Israelian water desalination company has successfully built and commissioned a significant number of installations in the field, which still cannot be regarded as industrialized mass-produced machines [3].

**Figure 2.** Volumetric cooling capacities of selected refrigerants.

**3. Centrifugal compressor cooling system**

refrigerant water is explained below.

**Figure 4.** Schematic drawing of the cooling module.

The functional and working process of a compact compression refrigeration system with the

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

127

The chiller fulfills two tasks: on the one hand, the cooling of the chilled water to the desired cold water outlet temperature and, on the other hand, the removal of the heat extracted from the water from a heat source. Of importance are the two identical refrigeration modules, one of which is shown in **Figure 4**. Each refrigeration module comprises the complete thermodynamic cycle. The evaporator and the condenser are nested to achieve a compact design. The chilled water enters the evaporator via the middle connection of the refrigeration module at a flow rate of approx. 2 liters per second. Here, there is a pressure that corresponds to the saturated pressure of the desired water outlet temperature of the evaporator. It is evaporated so much water until the superheated water has cooled to saturation temperature. The chilled cold water is directed downward out of the module. The maximum resulting vapor mass corresponds to about 1% of the circulated mass flow of water. The vapor enters the centrifugal compressor and is compressed to a higher pressure and temperature. The maximum achievable pressure ratio is currently in the range of 3.5 due to the rotational speed limitation of the compressors. The compression starts at approx. 40,000 revolutions per minute with a pressure ratio of 1 and can be continuously increased from there up to the maximum pressure ratio. The compressed, superheated steam flows into the condenser where it meets the cooling water. The cooling water is also fed to the cooling module from below. Due to the special design of the condenser, it is achieved that the water vapor can deliver its complete energy

**Figure 3.** Required compression ratios of selected refrigerants.

**Table 1.** Centrifugal chiller projects using R718 as refrigerant [3].

### **3. Centrifugal compressor cooling system**

The functional and working process of a compact compression refrigeration system with the refrigerant water is explained below.

The chiller fulfills two tasks: on the one hand, the cooling of the chilled water to the desired cold water outlet temperature and, on the other hand, the removal of the heat extracted from the water from a heat source. Of importance are the two identical refrigeration modules, one of which is shown in **Figure 4**. Each refrigeration module comprises the complete thermodynamic cycle. The evaporator and the condenser are nested to achieve a compact design. The chilled water enters the evaporator via the middle connection of the refrigeration module at a flow rate of approx. 2 liters per second. Here, there is a pressure that corresponds to the saturated pressure of the desired water outlet temperature of the evaporator. It is evaporated so much water until the superheated water has cooled to saturation temperature. The chilled cold water is directed downward out of the module. The maximum resulting vapor mass corresponds to about 1% of the circulated mass flow of water. The vapor enters the centrifugal compressor and is compressed to a higher pressure and temperature. The maximum achievable pressure ratio is currently in the range of 3.5 due to the rotational speed limitation of the compressors. The compression starts at approx. 40,000 revolutions per minute with a pressure ratio of 1 and can be continuously increased from there up to the maximum pressure ratio. The compressed, superheated steam flows into the condenser where it meets the cooling water. The cooling water is also fed to the cooling module from below. Due to the special design of the condenser, it is achieved that the water vapor can deliver its complete energy

**Figure 4.** Schematic drawing of the cooling module.

**Year Location Project group Application Cooling capacity Literature source**

 Denmark IDE/Sabroe Sea water heat pump 1.3 MW [6] Denmark IDE/Sabroe/TI Plastic molding cooling 2 MW [6] RSA IDE/Integral Gold mine cooling 6 × 3 MW [6] Germany ILK/GHS Essen Chilled water 1 MW [7] Germany ILK/VW Chilled water 1 MW [8] Germany ILK/Daimler Chilled water 1 MW [7] Japan IDE/Sanken Vacuum ice 350 kW [6] Japan IDE/Nissan Vacuum ice 1.5 MW [6] RSA IDE Gold mine cooling 3 × 3 MW [6] Switzerland IDE Artificial snow 1.4 MW [6] Austria IDE Artificial snow 1.4 MW [6] USA MSU Chilled water — [9] Denmark Rotrex/Topsøe Heat pump 350 kW [10] Japan Kawasaki HI Chilled water 350 kW [11] Germany ILK/Cofely Ref. Chilled water 800 kW [12] Japan Sasakura Chilled water 17.5 kW [5] Denmark TI/JCI Chilled water 800 kW [13] Germany ILK Vacuum ice 50 kW [12] Germany efficient energy Chilled water 35 kW [14]

**Table 1.** Centrifugal chiller projects using R718 as refrigerant [3].

**Figure 3.** Required compression ratios of selected refrigerants.

126 Advanced Cooling Technologies and Applications

to the circulating cooling water and gets completely condensed. The heated cooling water is discharged down from the module. To close the thermodynamic cycle, the evaporated amount of water from the condenser is returned via the self-regulating expansion device in the evaporator.

Depending on the heat sink temperature, this process can be followed by the second cooling module as a cascade.

## **4. Combination with water-loop cooled self-contained units**

This subsection investigates the combination of a CO2 process of a self-contained unit with water-loop cooling and a compression refrigeration unit with the refrigerant water in a cascade arrangement.

#### **4.1. Basics**

#### *4.1.1. R744 cycle*

The basic structure of a single-stage R744 refrigeration cycle is shown in **Figure 5**. Depending on the heat sink temperature, a distinction is made between a subcritical system and a transcritical system. The mode of operation determines the selection of components to a considerable extent.

#### *4.1.2. R718 cycle*

The properties of R718 shown in Chapter 2.1 set the following requirements for the use of water as a refrigerant. The low vapor pressures require operation in vacuum, and the large pressure ratio requires a two-stage compression in cascade.

System (a) is a two-stage design with two identical refrigeration modules, with the first-stage condenser connected to the second-stage evaporator by a water interface. The required water circulation is generated by a circulating pump. Both condenser and evaporator are designed as open systems and, hence, the adapted, dashed symbol in the flow diagram. The heat transfer on the heat source as well as the heat sink side of the refrigeration system is done by braze plate heat exchangers. Again, a separate circulation pump is used for each circuit. Thus, a total

**Figure 6.** (a) Schematic of a R718 refrigeration system with external heat exchangers (without i.c.). (b) Schematic of a

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

129

System (b) differs from system (a) in the following points. The intermediate circle is not realized in this structure by a water interface but by a vapor interface with intermediate cooling (i.c.). Furthermore, the heat exchangers are integrated in the evaporator and condenser.

**Table 2** lists the three system combinations under consideration. System 1 is a coupled sys-

as a braze plate heat exchanger and represents the interface to the water-loop. The condensing heat is transported by means of the water-loop to the dry cooler, and this dissipates

compression refrigeration system, a water-loop and

system is designed

of three pumps are required to operate the system in its present design stage.

*4.1.3. Possible designs and combination of cascaded refrigeration processes*

R718 refrigeration system with integrated heat exchangers (with i.c.).

a dry cooler outside the building. The condenser/gas cooler of the CO2

tem of a self-contained unit with a CO2

Therefore, the three required internal circulation pumps in the system are obsolete.

An overview of the machines implemented and the technical challenges of using water as a refrigerant in a centrifugal compressor cooling system have been described by reference [3].

**Figure 6** shows a one-step process for both systems (a) and (b). This is for simplification of the illustration only. In the later calculation, however, the real two-stage operation is considered.

**Figure 5.** Schematic of R744 refrigeration system.

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications http://dx.doi.org/10.5772/intechopen.79614 129

to the circulating cooling water and gets completely condensed. The heated cooling water is discharged down from the module. To close the thermodynamic cycle, the evaporated amount of water from the condenser is returned via the self-regulating expansion device in

Depending on the heat sink temperature, this process can be followed by the second cooling

water-loop cooling and a compression refrigeration unit with the refrigerant water in a cas-

The basic structure of a single-stage R744 refrigeration cycle is shown in **Figure 5**. Depending on the heat sink temperature, a distinction is made between a subcritical system and a transcritical system. The mode of operation determines the selection of components to a consider-

The properties of R718 shown in Chapter 2.1 set the following requirements for the use of water as a refrigerant. The low vapor pressures require operation in vacuum, and the large

An overview of the machines implemented and the technical challenges of using water as a refrigerant in a centrifugal compressor cooling system have been described by reference [3]. **Figure 6** shows a one-step process for both systems (a) and (b). This is for simplification of the illustration only. In the later calculation, however, the real two-stage operation is considered.

process of a self-contained unit with

**4. Combination with water-loop cooled self-contained units**

This subsection investigates the combination of a CO2

pressure ratio requires a two-stage compression in cascade.

**Figure 5.** Schematic of R744 refrigeration system.

the evaporator.

module as a cascade.

128 Advanced Cooling Technologies and Applications

cade arrangement.

**4.1. Basics**

able extent.

*4.1.2. R718 cycle*

*4.1.1. R744 cycle*

**Figure 6.** (a) Schematic of a R718 refrigeration system with external heat exchangers (without i.c.). (b) Schematic of a R718 refrigeration system with integrated heat exchangers (with i.c.).

System (a) is a two-stage design with two identical refrigeration modules, with the first-stage condenser connected to the second-stage evaporator by a water interface. The required water circulation is generated by a circulating pump. Both condenser and evaporator are designed as open systems and, hence, the adapted, dashed symbol in the flow diagram. The heat transfer on the heat source as well as the heat sink side of the refrigeration system is done by braze plate heat exchangers. Again, a separate circulation pump is used for each circuit. Thus, a total of three pumps are required to operate the system in its present design stage.

System (b) differs from system (a) in the following points. The intermediate circle is not realized in this structure by a water interface but by a vapor interface with intermediate cooling (i.c.). Furthermore, the heat exchangers are integrated in the evaporator and condenser. Therefore, the three required internal circulation pumps in the system are obsolete.

#### *4.1.3. Possible designs and combination of cascaded refrigeration processes*

**Table 2** lists the three system combinations under consideration. System 1 is a coupled system of a self-contained unit with a CO2 compression refrigeration system, a water-loop and a dry cooler outside the building. The condenser/gas cooler of the CO2 system is designed as a braze plate heat exchanger and represents the interface to the water-loop. The condensing heat is transported by means of the water-loop to the dry cooler, and this dissipates

The electrical power consumption of the R744 compressor was determined for all three systems by means of the manufacturer's design software [15] for the respective operating points. For all systems a constant power consumption of 400 W was assumed for each water-loop circulation pump. System 2 also took into account the electrical power consumption of the three internal circulation pumps with a constant power consumption of 500 W and the electrical power consumption of the two R718 centrifugal compressors. With System 3, the three pumps are eliminated, and thus only the two centrifugal compressors have been considered. The electrical power consumption of the fans on the dry cooler or condenser/gas cooler has not been taken into account for the qualitative comparison of calculations in any system.

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

*PR*744 + *PWL*

As described in Section 2.4, System 1 is designed according to the maximum ambient temperature. Systems 2 and 3 are calculated with two condensing temperatures, 15 and 26°C. The required piston displacements of the carbon dioxide compressors for the indicated cooling capacity of 22 kW at −5 and −15°C evaporation temperature can be taken from **Table 4** for all

The required piston displacements are lower by a factor of two for Systems 2 and 3 than for

**Figures 7** and **8** show the COP characteristics of the three systems above the ambient temperature. System 1 is used as the reference for the comparison of the systems, as described in Section 2.4. From both figures, it gets obvious that the switching point for the optimum

process

process

**2/3**

**Tc = 26°C Tc = 15°C**

three systems. The compressors were designed with frequency-controlled motors.

(1)

131

(2)

(3)

The exact calculations of the individual systems can be found in Formulas 1–3.

*COP*1 = \_\_\_\_\_\_\_\_ *Q*0

*COP*2 = \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ *Q*0 *PR*744 + *PWL* + *PPumps* + *PR*718

*COP*3 = \_\_\_\_\_\_\_\_\_\_\_\_ *Q*0 *PR*744 + *PWL* + *PR*718

**4.3. Results and comparison of the systems**

energetic mode of operation depends on two factors:

**TC = 40.5°C**

T0 = −5°C 9.6 m3 h−1 6.5 m3 h−1 4.8 m3 h−1 T0 = −15°C 12 m3 h−1 9.6 m3 h−1 6.5 m3 h−1

**Table 4.** The required piston displacements of the carbon dioxide compressors depending on the system.

• The evaporation temperature of the CO2

• The condensation temperature of the CO2

**Systems 1**

System 1.

**Table 2.** The different systems.

the waste heat to be ambient. In this system, the CO2 process is subcritical or transcritical depending on the ambient temperature. As a result, all components must be designed for transcritical operation and the compressor for maximum load. These are then oversized for most of the year.

Systems 2 and 3 each consist of a self-contained unit with a CO2 compression refrigeration system, a water-loop and an additional centrifugal compressor cooling system with water as refrigerant. This ensures that the CO2 process can always be subcritical, as the water-loop always generates a constant water temperature for condensing CO2 which is below the critical temperature of CO2 . The differences between Systems 2 and 3 are in the type of the R718 system used. System 2 is shown in **Figure 6(a)** and System 3 in **Figure 6(b)**.

The reference for the comparison is System 1.

#### **4.2. Methods**

For the qualitative assessment, the three systems were calculated with the following assumptions (**Table 3**). The physical properties for the cycle process calculation of the R718 process were generated using REFPROP [4].

**Table 3.** Operating conditions.

The electrical power consumption of the R744 compressor was determined for all three systems by means of the manufacturer's design software [15] for the respective operating points. For all systems a constant power consumption of 400 W was assumed for each water-loop circulation pump. System 2 also took into account the electrical power consumption of the three internal circulation pumps with a constant power consumption of 500 W and the electrical power consumption of the two R718 centrifugal compressors. With System 3, the three pumps are eliminated, and thus only the two centrifugal compressors have been considered.

The electrical power consumption of the fans on the dry cooler or condenser/gas cooler has not been taken into account for the qualitative comparison of calculations in any system.

The exact calculations of the individual systems can be found in Formulas 1–3.

$$\text{COP}\_1 = \frac{Q\_0}{P\_{\text{new}} + P\_{\text{NL}}} \tag{1}$$

$$COP\_1 = \frac{Q\_0}{P\_{\text{new}} + P\_{\text{NL}}} \tag{1}$$

$$COP\_2 = \frac{Q\_0}{P\_{\text{new}} + P\_{\text{NL}} + P\_{\text{Pump}} + P\_{\text{RTS}}} \tag{2}$$

$$\text{COP}\_3 = \frac{Q\_0}{P\_{\text{new}} + P\_{\text{out}} + P\_{\text{orrs}}} \tag{3}$$

#### **4.3. Results and comparison of the systems**

the waste heat to be ambient. In this system, the CO2

as refrigerant. This ensures that the CO2

System 1 CO2 + water loop

130 Advanced Cooling Technologies and Applications

The reference for the comparison is System 1.

were generated using REFPROP [4].

Systems 2 and 3 each consist of a self-contained unit with a CO2

always generates a constant water temperature for condensing CO2

Superheating 10 K Cooling capacity (all systems) 22 kW Evaporation temperature T0 −5/−15 °C TGC/C–Tamb 4 K

Chilled water temperature 13.5/24.5 °C Compressor efficiency 0.6 — Electrical efficiency 0.8 — Tc.w.–Tamb 4 K

Maximum ambient temperature 35 °C TGC/C–TWL 1.5 K

system used. System 2 is shown in **Figure 6(a)** and System 3 in **Figure 6(b)**.

System 2 CO2 + water loop + R718 chiller without i.c. + external heat exchangers System 3 CO2 + water loop + R718 chiller with i.c. + integrated heat exchangers

most of the year.

**Table 2.** The different systems.

cal temperature of CO2

**4.2. Methods**

**R744**

**R718**

**Combination**

**Table 3.** Operating conditions.

depending on the ambient temperature. As a result, all components must be designed for transcritical operation and the compressor for maximum load. These are then oversized for

system, a water-loop and an additional centrifugal compressor cooling system with water

For the qualitative assessment, the three systems were calculated with the following assumptions (**Table 3**). The physical properties for the cycle process calculation of the R718 process

process is subcritical or transcritical

process can always be subcritical, as the water-loop

. The differences between Systems 2 and 3 are in the type of the R718

compression refrigeration

which is below the criti-

As described in Section 2.4, System 1 is designed according to the maximum ambient temperature. Systems 2 and 3 are calculated with two condensing temperatures, 15 and 26°C. The required piston displacements of the carbon dioxide compressors for the indicated cooling capacity of 22 kW at −5 and −15°C evaporation temperature can be taken from **Table 4** for all three systems. The compressors were designed with frequency-controlled motors.

The required piston displacements are lower by a factor of two for Systems 2 and 3 than for System 1.

**Figures 7** and **8** show the COP characteristics of the three systems above the ambient temperature. System 1 is used as the reference for the comparison of the systems, as described in Section 2.4. From both figures, it gets obvious that the switching point for the optimum energetic mode of operation depends on two factors:

**Table 4.** The required piston displacements of the carbon dioxide compressors depending on the system.

**5. Mechanical subcooling of transcritical carbon dioxide**

of the gas cooler. The aim is to further cool the transcritical CO2

energy required for the evaporation of the water is taken from the CO2

of the compressor starts as low as at a value of "1."

**Figure 9.** Schematic of the combined subcooling cycle.

**Figure 9** shows the schematic structure of the investigated system. It is a single-stage CO2 cycle, the "refrigeration cycle," and a subcooling circuit "mechanical subcooling" downstream

means of an additional compression refrigeration system. The refrigerant in this subcooling circuit is R718. The interface between the two circuits is a finned tube heat exchanger, which is

The resulting water vapor is compressed by means of a centrifugal compressor and fed into the condenser. There, the water vapor rejects its energy to another finned tube heat exchanger to an additional cooling circuit and condenses completely. The circuit is then closed by a selfregulating, pressure loss-free expansion device. The expansion device used in combination with the continuously variable centrifugal compressor allows a continuous adjustment of the delivered volume flow, and the ratio between the condensing pressure and suction pressure

The additional cooling circuit in the considered system consists of the heat exchanger, a circulation pump, and a dry cooler. As a working medium, a glycol/water brine is usually used. This extra circuit is needed because there are no commercially available air condensers for

inside and is surrounded by circulating water in a vacuum atmosphere. The

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

leaving the gas cooler by

http://dx.doi.org/10.5772/intechopen.79614

133

gas, thereby cooling it.

**5.1. The investigated system**

traversed by CO2

**Figure 7.** Comparison of the COP values at T0 = −5°C.

**Figure 8.** Comparison of the COP values at T0 = −15°C.

For both factors the statement applies, the lower, the better.

Thus, the switching point for T0 = −5°C and TC = 15°C at Tamb = 22.7°C and for T0 = −15°C and TC = 15°C at Tamb = 21°C compared with System 1. In both cases, System 3 has a significantly better energetic performance than System 2. This can be explained by the fact that in System 3 the circulating pumps of the R718 process can be dispensed with, and the losses in the water cycle between the two refrigeration modules are eliminated by using the intermediate cooling.

### **5. Mechanical subcooling of transcritical carbon dioxide**

#### **5.1. The investigated system**

**Figure 9** shows the schematic structure of the investigated system. It is a single-stage CO2 cycle, the "refrigeration cycle," and a subcooling circuit "mechanical subcooling" downstream of the gas cooler. The aim is to further cool the transcritical CO2 leaving the gas cooler by means of an additional compression refrigeration system. The refrigerant in this subcooling circuit is R718. The interface between the two circuits is a finned tube heat exchanger, which is traversed by CO2 inside and is surrounded by circulating water in a vacuum atmosphere. The energy required for the evaporation of the water is taken from the CO2 gas, thereby cooling it. The resulting water vapor is compressed by means of a centrifugal compressor and fed into the condenser. There, the water vapor rejects its energy to another finned tube heat exchanger to an additional cooling circuit and condenses completely. The circuit is then closed by a selfregulating, pressure loss-free expansion device. The expansion device used in combination with the continuously variable centrifugal compressor allows a continuous adjustment of the delivered volume flow, and the ratio between the condensing pressure and suction pressure of the compressor starts as low as at a value of "1."

The additional cooling circuit in the considered system consists of the heat exchanger, a circulation pump, and a dry cooler. As a working medium, a glycol/water brine is usually used. This extra circuit is needed because there are no commercially available air condensers for

**Figure 9.** Schematic of the combined subcooling cycle.

For both factors the statement applies, the lower, the better.

**Figure 8.** Comparison of the COP values at T0 = −15°C.

**Figure 7.** Comparison of the COP values at T0 = −5°C.

132 Advanced Cooling Technologies and Applications

cooling.

Thus, the switching point for T0 = −5°C and TC = 15°C at Tamb = 22.7°C and for T0 = −15°C and TC = 15°C at Tamb = 21°C compared with System 1. In both cases, System 3 has a significantly better energetic performance than System 2. This can be explained by the fact that in System 3 the circulating pumps of the R718 process can be dispensed with, and the losses in the water cycle between the two refrigeration modules are eliminated by using the intermediate R718. The problem is the given density ratio of >10,000, at a temperature of 50°C increasingly with decreasing water or steam temperature. Both systems, gas coolers and dry coolers, transfer their waste heat to the same heat sink, the environment.

#### **5.2. Method**

For the evaluation of the system with and without mechanical subcooling, the assumptions given in **Table 5** were used as the basis for the calculations. The physical properties of the refrigerants used for the respective cycles were generated with REFPROP [4].

For the calculation of the individual COP values, the electrical power consumption of the circulation pump in the external cooling water circuit of the R718 chiller as well as the fans of the gas cooler and the dry cooler were neglected. Only the specific capacities were considered. Eq. (4) shows the general calculation of COP, which is also used for the determination of pure transcritical operation. *q0* corresponds to the specific cooling capacity and *wc* to the required specific compressor work of the refrigeration cycle.

$$COP = \frac{q\_0}{w\_c} \tag{4}$$

*wc*,*R*744 = *h*2,*s* − *h* \_\_\_\_\_\_1

Superheating 10 K Cooling capacity 150 kW Evaporating temperature −5/−15 °C

env 5 K Isentropic compressor efficiency [16] 0.95–0.1\*π —

1\* 5 K compressor efficiency 0.7 —

env 4 K maximum compressor volume flow 1.2 m3 s−1

*wc*,*R*718 = *h*2∗

Eq. (12).

**Table 5.** Operating conditions.

**Figure 10.** Schematic with state points.

**R744**

t 3⁻t

t 3\*⁻t

**R718** t 4⁻t

*ηi*,*R*744

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

,*s* − *h*1∗ \_\_\_\_\_\_\_ *ηi*,*R*718

Based on Eq. (4), the COP of the entire system is calculated in subcooling mode according to

(10)

135

(11)

Eq. (5) shows the calculation of the specific cooling capacity and Eq. (6) the specific subcooling capacity of the CO2 cycle. Eq. (7) shows the specific cooling capacity of the R718 circuit. *h0* and *h5* correspond to the specific enthalpy at the outlet of the evaporator or after the throttle, *h3* and *h4* to the specific enthalpy at the outlet of the gas cooler or after subcooling in the CO2 cycle, and *h1\** and *h4\** to the specific enthalpy in the evaporator or after relaxing in the R718 circle.

$$q\_{0,2744} = h\_0 - h\_5 \tag{5}$$

$$q\_{sub} = \ \mathrm{h\_3} - \mathrm{h\_4} \tag{6}$$

$$q\_{0,0\tau \text{18}} = \ h\_{\text{1}} - h\_{\text{4}} \tag{7}$$

The energy balance of the subcooler is shown in Eq. (8), and Eq. (9) shows the relation of the occurring mass flows.

$$
\dot{m}\_{\text{k744}} \ast q\_{\text{sub}} = \dot{m}\_{\text{k718}} \ast q\_{0, \text{k718}} \tag{8}
$$

$$
\dot{m}\_{\text{kTIS}} = \frac{\dot{m}\_{\text{BUS}} \* q\_{\text{sub}}}{q\_{0,\text{BTts}}} \tag{9}
$$

The specific compressor work of the two single-stage systems is shown in Eq. (10) for the R744 cycle and in Eq. (11) for the R718 process. *h1* and *h1\** represent the specific enthalpy at the compressor inlet, *h2* and *h2\** the isentropic specific enthalpy at the compressor outlet. *ηi,R744* and *ηi,R718* are the isentropic efficiencies of the respective compressors.

**Table 5.** Operating conditions.

R718. The problem is the given density ratio of >10,000, at a temperature of 50°C increasingly with decreasing water or steam temperature. Both systems, gas coolers and dry coolers, trans-

For the evaluation of the system with and without mechanical subcooling, the assumptions given in **Table 5** were used as the basis for the calculations. The physical properties of the

For the calculation of the individual COP values, the electrical power consumption of the circulation pump in the external cooling water circuit of the R718 chiller as well as the fans of the gas cooler and the dry cooler were neglected. Only the specific capacities were considered. Eq. (4) shows the general calculation of COP, which is also used for the determination of pure

corresponds to the specific cooling capacity and *wc*

\_\_\_0 *wc*

cycle. Eq. (7) shows the specific cooling capacity of the R718 circuit. *h0*

Eq. (5) shows the calculation of the specific cooling capacity and Eq. (6) the specific subcooling

correspond to the specific enthalpy at the outlet of the evaporator or after the throttle, *h3*

and *h1\** and *h4\** to the specific enthalpy in the evaporator or after relaxing in the R718 circle.

*q*0,*R*744 = *h*0 − *h*5 (5)

*qsub* = *h*3 − *h*4 (6)

*q*0,*R*718 = *h*1∗ − *h*4∗ (7)

The energy balance of the subcooler is shown in Eq. (8), and Eq. (9) shows the relation of the

*R*718 ∗ *q*0,*R*718 (8)

and *h1\** represent the specific enthalpy at the

*R*744 ∗ *qsub* = *m*̇

*R*718 = *m*̇

The specific compressor work of the two single-stage systems is shown in Eq. (10) for the

*R*744 ∗ *q* \_\_\_\_\_\_\_\_\_*sub q*0,*R*718

and *h2\** the isentropic specific enthalpy at the compressor outlet. *ηi,R744* and

to the specific enthalpy at the outlet of the gas cooler or after subcooling in the CO2

to the required

(4)

and

and

(9)

cycle,

refrigerants used for the respective cycles were generated with REFPROP [4].

fer their waste heat to the same heat sink, the environment.

specific compressor work of the refrigeration cycle.

*COP* = *q*

**5.2. Method**

transcritical operation. *q0*

134 Advanced Cooling Technologies and Applications

capacity of the CO2

occurring mass flows.

compressor inlet, *h2*

*m*̇

*m*̇

R744 cycle and in Eq. (11) for the R718 process. *h1*

*ηi,R718* are the isentropic efficiencies of the respective compressors.

*h5*

*h4*

$$
\pi \upsilon\_{c, RT44} = \frac{h\_{t,s} - h\_t}{\eta\_{i,RT44}} \tag{10}
$$

$$
\pi \upsilon\_{c,RT18} = \frac{h\_{z\_{1,s}} - h\_{i\_{\parallel}}}{\eta\_{i,RT18}} \tag{11}
$$

Based on Eq. (4), the COP of the entire system is calculated in subcooling mode according to Eq. (12).

**Figure 10.** Schematic with state points.

been determined by means of a self-developed simulation. From each of the two diagrams, two

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

the optimal pressures for operation with a subcooling of −2.5, −5, and −7.5 K are shown. Diagram

can be seen that the optimum pressure drops as expected with increasing subcooling value. For (c)

slightly higher when cooled by 5 K. This is followed by an increase in efficiency with subsequent increase in pressure, followed by a rise to a turning point. From this, the efficiency of the system continues to fall with further increases in process pressure. These inflection points are referred to in the diagrams as *optimized optimal pressure* and are preferable to the maximum efficiency points, since the efficiency values are only slightly lower and there are advantages for selecting the compressor for the subcooling stage. This can be explained by the p-h diagram shown in **Figure 12**.

*0* = −5°C and *t3* = 35°C. The solid line with the triangle symbols at the respective state points represents the pure transcritical cycle without mechanical subcooling at optimum high pressure. The dotted line with the circle symbols represents the transcritical cycle with a subcooling of 7.5 K at optimum high pressure (74 bars), and the dashed line with the rhombuses represents the transcritical cycle with subcooling at the optimized optimum pressure. The points *3* and *4* for the compared subcooling cycles are each on the same isotherms and represent at *3* the temperature at the gas cooler outlet and at *4* the temperature after the subcooling. Provided that the same cooling capacity is required for both systems, both systems need

optimal and optimized optimal pressure, it clearly shows that the required subcooling performance at optimum pressure is more than a factor of two higher than that of the optimally

optimized pressure. This would also result in a larger sizing of the R718 chiller.

*env* = 45°C are considered in more detail, and

http://dx.doi.org/10.5772/intechopen.79614

*env* = 30°C and a subcooling of 7.5 K at 74 bar and at (d) are only

. If one compares the enthalpy difference *qsub* with

cycle with and without mechanical subcooling (t0 = −5°C, t3 = 35°C).

*0* = −15°C. In both diagrams, it

137

cycle for the operating point

*env* = 30°C and *t*

*0* = −5°C, and diagram (d) shows the values *t*

curves at the ambient temperatures *t*

and (d), the optimum pressures at *t*

approximately the same mass flow of CO2

**Figure 12.** p-h diagram of the transcritical CO2

The three illustrated cycles each show the transcritical CO2

(c) shows the values for *t*

*t*

**Figure 11.** Optimal high pressure for the transcritical CO2 cycle with (a) t0 = −5°C and (b) t0 = −15°C; optimal and optimized pressure with subcooling for (c) t0 = −5°C and (d) t0 = −15°C.

$$\begin{aligned} \text{Cos:} \quad & \dot{\mathbf{w}} = \mathbf{C}^\* \mathbf{w} \\\\ \text{CO:} \quad & \dot{\mathbf{w}} = \mathbf{C}^\* \mathbf{w} \\\\ \text{CO:} \quad & \dot{\mathbf{w}} = \mathbf{C}^\* \mathbf{w} \\\\ \text{CO:} \quad & \dot{\mathbf{w}} = \mathbf{C}^\* \mathbf{w} \end{aligned} \tag{12}$$

$$\text{CO:} \quad \dot{\mathbf{w}} = \frac{\dot{\mathbf{w}}\_{\text{EC44}} \* q\_{0, \text{EC44}}}{\dot{\mathbf{w}}\_{\text{EC44}} \* w\_{c, \text{EC44}} + \dot{m}\_{\text{EC38}} \* w\_{c, \text{EC38}}} = \frac{q\_{0, \text{EC44}}}{w\_{c, \text{EC44}} + \frac{q\_{\alpha \delta}}{q\_{0, \text{EC38}}} \* w\_{c, \text{EC38}}} \tag{12}$$

The individual states of the respective circuits are shown in **Figure 10**.

#### **5.3. Results**

#### *5.3.1. Optimum operating conditions*

**Figure 11** shows the optimal high pressures of the transcritical CO2 system, (a) for *t 0* = −5°C and (b) for *t 0* = −15°C, for different ambient temperatures. The respective dashed lines represent the interpolated connections between the individual maximum points. The individual marked values have been determined by means of a self-developed simulation. From each of the two diagrams, two curves at the ambient temperatures *t env* = 30°C and *t env* = 45°C are considered in more detail, and the optimal pressures for operation with a subcooling of −2.5, −5, and −7.5 K are shown. Diagram (c) shows the values for *t 0* = −5°C, and diagram (d) shows the values *t 0* = −15°C. In both diagrams, it can be seen that the optimum pressure drops as expected with increasing subcooling value. For (c) and (d), the optimum pressures at *t env* = 30°C and a subcooling of 7.5 K at 74 bar and at (d) are only slightly higher when cooled by 5 K. This is followed by an increase in efficiency with subsequent increase in pressure, followed by a rise to a turning point. From this, the efficiency of the system continues to fall with further increases in process pressure. These inflection points are referred to in the diagrams as *optimized optimal pressure* and are preferable to the maximum efficiency points, since the efficiency values are only slightly lower and there are advantages for selecting the compressor for the subcooling stage. This can be explained by the p-h diagram shown in **Figure 12**.

The three illustrated cycles each show the transcritical CO2 cycle for the operating point *t 0* = −5°C and *t3* = 35°C. The solid line with the triangle symbols at the respective state points represents the pure transcritical cycle without mechanical subcooling at optimum high pressure. The dotted line with the circle symbols represents the transcritical cycle with a subcooling of 7.5 K at optimum high pressure (74 bars), and the dashed line with the rhombuses represents the transcritical cycle with subcooling at the optimized optimum pressure. The points *3* and *4* for the compared subcooling cycles are each on the same isotherms and represent at *3* the temperature at the gas cooler outlet and at *4* the temperature after the subcooling. Provided that the same cooling capacity is required for both systems, both systems need approximately the same mass flow of CO2 . If one compares the enthalpy difference *qsub* with optimal and optimized optimal pressure, it clearly shows that the required subcooling performance at optimum pressure is more than a factor of two higher than that of the optimally optimized pressure. This would also result in a larger sizing of the R718 chiller.

*COP*∗ = *m*̇

136 Advanced Cooling Technologies and Applications

**Figure 11.** Optimal high pressure for the transcritical CO2

optimized pressure with subcooling for (c) t0 = −5°C and (d) t0 = −15°C.

*5.3.1. Optimum operating conditions*

**5.3. Results**

(b) for *t*

*R*744 ∗ *q*0,*R*744 \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ *m*̇

*R*718 ∗ *wc*,*R*718

*0* = −15°C, for different ambient temperatures. The respective dashed lines represent the interpolated connections between the individual maximum points. The individual marked values have

= *q* \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 0,*R*744 *wc*,*R*744 + *q*\_\_\_\_\_ *sub*

*q*0,*R*718

∗ *wc*,*R*718

cycle with (a) t0 = −5°C and (b) t0 = −15°C; optimal and

system, (a) for *t*

(12)

*0* = −5°C and

*R*744 ∗ *wc*,*R*744 + *m*̇

The individual states of the respective circuits are shown in **Figure 10**.

**Figure 11** shows the optimal high pressures of the transcritical CO2

**Figure 12.** p-h diagram of the transcritical CO2 cycle with and without mechanical subcooling (t0 = −5°C, t3 = 35°C).

#### *5.3.2. Efficiency increase*

Based on the optimum or optimized optimum operating pressures, **Figure 13** shows the COP curves for pure transcritical operation and for transcritical operation with mechanical subcooling as a function of the environment temperature. Diagram (a) refers to *t 0* = −5°C and diagram (b) to *t 0* = −15°C. Furthermore, with the respective secondary axis, the efficiency increase between the purely transcritical operation and the operation with a subcooling of 7.5 K is shown. When comparing the two curves, it is noticeable that there is a dependency on the evaporation temperature and the ambient temperature. With decreasing evaporation temperature, as well as with increasing ambient temperature, the percentage increase in efficiency increases. Furthermore, it can be seen that the increase from an ambient temperature of *t env* = 35°C is significantly lower and seems to approach asymptotically to a maximum limit.

#### *5.3.3. Required subcooling capacity*

In the following, the required subcooling capacities (SUB) are shown in **Figure 14** with the solid lines, and the maximum possible cooling capacity (Q\_0) of the R718 circuit for the three indicated subcooling temperatures is shown by the dashed lines. Diagram (a) refers to *t 0* = −5°C and diagram (b) to *t 0* = −15°C. The optimized optimum pressure was used as the basis for the calculation.

increasing possible cooling capacity with higher environment temperatures. This is related to

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

139

In order to be able to subcool at least 7.5 K over the whole range of the environmental temperatures, there are two options for optimization. The first one could use a R718 compressor with a larger maximum flow rate, and, the second one could increase the process pressure at the outlet of the R744 compressor in order to reduce the required subcooling performance. Both options require further investigation to determine which of the two is more efficient. Furthermore, the combination of the two systems can still be examined to see what absolute subcooling over the entire environment temperature range for the two evaporation temperatures can be achieved.

The analysis of the systems has shown that a self-contained unit with water-loop combined with a centrifugal compressor cooling system with water as refrigerant of System 3 at a condensing temperature of TC = 15°C and an evaporation temperature of T0 = −15°C of the CO2 process above an ambient temperature of Tamb = 21°C proves to make sense from an energetic point of view. In addition to the energetic consideration, the positive effect of the subcritical design in contrast to System 1 has been noticed. It allows a much simpler design of the CO2

tem and the up to a factor 2 lower required piston displacements of the R744 compressors used.

a refrigeration system with the refrigerant R718 has shown that efficiency increases of more than 35% compared to purely transcritical operation can occur. The main influencing factors regarding the efficiency are on the one hand the evaporation and ambient temperatures and, on the other hand, the process pressure on the pressure side of the compressor. It has been

process with subsequent mechanical subcooling with

sys-

the increase in the density of water vapor as the evaporation temperature increases.

**Figure 14.** Required subcooling capacity and possible cooling capacity: (a) t0 = −5°C and (b) t0 = −15°C.

**6. Conclusion**

The simulation of a transcritical CO2

It is easy to see that for both evaporating temperatures, with a small exception at *t0* = −15°C, with the single-stage R718 system, with the maximum volumetric flow given in **Table 5**, a subcooling of −5 K over the entire temperature range of the environment can be realized. Over a wide range, a subcooling value of >7.5 K is possible with the above setting. Again, for a subcooling of 7.5 K, as in **Figure 13**, a turning point in the curve at *t env* = 35°C can be seen. In addition, significantly larger subcooling temperatures are possible. Another point is the

**Figure 13.** COP of the transcritical CO2 cycle with and without subcooling: (a) t0 = −5°C and (b) t0 = −15°C.

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications http://dx.doi.org/10.5772/intechopen.79614 139

**Figure 14.** Required subcooling capacity and possible cooling capacity: (a) t0 = −5°C and (b) t0 = −15°C.

increasing possible cooling capacity with higher environment temperatures. This is related to the increase in the density of water vapor as the evaporation temperature increases.

In order to be able to subcool at least 7.5 K over the whole range of the environmental temperatures, there are two options for optimization. The first one could use a R718 compressor with a larger maximum flow rate, and, the second one could increase the process pressure at the outlet of the R744 compressor in order to reduce the required subcooling performance. Both options require further investigation to determine which of the two is more efficient. Furthermore, the combination of the two systems can still be examined to see what absolute subcooling over the entire environment temperature range for the two evaporation temperatures can be achieved.

#### **6. Conclusion**

*5.3.2. Efficiency increase*

138 Advanced Cooling Technologies and Applications

diagram (b) to *t*

*5.3.3. Required subcooling capacity*

*0* = −5°C and diagram (b) to *t*

**Figure 13.** COP of the transcritical CO2

for the calculation.

of *t*

*t*

Based on the optimum or optimized optimum operating pressures, **Figure 13** shows the COP curves for pure transcritical operation and for transcritical operation with mechanical sub-

increase between the purely transcritical operation and the operation with a subcooling of 7.5 K is shown. When comparing the two curves, it is noticeable that there is a dependency on the evaporation temperature and the ambient temperature. With decreasing evaporation temperature, as well as with increasing ambient temperature, the percentage increase in efficiency increases. Furthermore, it can be seen that the increase from an ambient temperature

*env* = 35°C is significantly lower and seems to approach asymptotically to a maximum limit.

In the following, the required subcooling capacities (SUB) are shown in **Figure 14** with the solid lines, and the maximum possible cooling capacity (Q\_0) of the R718 circuit for the three indicated subcooling temperatures is shown by the dashed lines. Diagram (a) refers to

It is easy to see that for both evaporating temperatures, with a small exception at *t0* = −15°C, with the single-stage R718 system, with the maximum volumetric flow given in **Table 5**, a subcooling of −5 K over the entire temperature range of the environment can be realized. Over a wide range, a subcooling value of >7.5 K is possible with the above setting. Again, for

In addition, significantly larger subcooling temperatures are possible. Another point is the

cycle with and without subcooling: (a) t0 = −5°C and (b) t0 = −15°C.

a subcooling of 7.5 K, as in **Figure 13**, a turning point in the curve at *t*

*0* = −15°C. Furthermore, with the respective secondary axis, the efficiency

*0* = −15°C. The optimized optimum pressure was used as the basis

*0* = −5°C and

*env* = 35°C can be seen.

cooling as a function of the environment temperature. Diagram (a) refers to *t*

The analysis of the systems has shown that a self-contained unit with water-loop combined with a centrifugal compressor cooling system with water as refrigerant of System 3 at a condensing temperature of TC = 15°C and an evaporation temperature of T0 = −15°C of the CO2 process above an ambient temperature of Tamb = 21°C proves to make sense from an energetic point of view. In addition to the energetic consideration, the positive effect of the subcritical design in contrast to System 1 has been noticed. It allows a much simpler design of the CO2 system and the up to a factor 2 lower required piston displacements of the R744 compressors used.

The simulation of a transcritical CO2 process with subsequent mechanical subcooling with a refrigeration system with the refrigerant R718 has shown that efficiency increases of more than 35% compared to purely transcritical operation can occur. The main influencing factors regarding the efficiency are on the one hand the evaporation and ambient temperatures and, on the other hand, the process pressure on the pressure side of the compressor. It has been noticed that in the course of the COP curve above the environmental temperature, there are, in addition to the optimal process pressure, also points which have a positive effect on the entire system with a slight loss of efficiency. For both investigated evaporation temperatures in the CO2 cycle, a subcooling of 5 K is possible with the considered system with a small exception over the entire ambient temperature range. Over much of the environmental temperatures, significantly greater temperature differences are possible. In order to allow a subcooling of 7.5 K over the entire temperature range, further investigations have to be made, which on the one hand consider a larger compressor and on the other hand a further optimized process pressure.

R718 related to the R718 cycle R744 related to the R744 cycle

Florian Hanslik\* and Juergen Suess

Efficient Energy GmbH, Feldkirchen, Germany

**Author details**

**References**

er.1084

WL related to the water-loop circulating pump

\*Address all correspondence to<EMAIL_ADDRESS>
(EC) No 842/2006: (OJ L 150 of 20.5.2014, pp. 195-230); 2014

Transport Properties Database (REFPROP); 2013

2011;**34**:1286-1295. DOI: 10.1016/j.ijrefrig.2011.03.002

344-009, PSO Program 2012, Dansk Energi

yodogawa-ku, Osaka 555-0011, Japan

[1] European Commission. Regulation (EU) No 517/2014 of the European Parliament and of the Council of 16 April 2014 on fluorinated greenhouse gases and repealing Regulation

Water as a Refrigerant in Centrifugal Compressor Cooling Systems for Industrial Applications

http://dx.doi.org/10.5772/intechopen.79614

141

[2] Kilicarslan A, Müller N. A comparative study of water as a refrigerant with some current refrigerants. International Journal of Energy Research. 2005;**29**:947-959. DOI: 10.1002/

[3] Suess J. A centrifugal compressor cooling system using water as working fluid. In: 12th IIR-Gustav Lorentzen Natural Working Fluids Conference (GL 2016); 21-24 August;

[4] Lemmon EW, Huber ML, McLinden MO. NIST Reference Fluid Thermodynamic and

[5] Sasakura T. Report 2014 Sasakura Engineering Co., Ltd. 7-32 Takejima 4-chome, Nishi-

[6] Ophir A. Mechanical heat pumps using water as refrigerant for ice production and air conditioning. In: IDEA 99th Annual Converence & Trade Show, Orlando, Florida; 2008

[8] Albring P, Honke M. Ice-making and ice storage, with water as refrigerant. In: 23rd IIR International Congress of Refrigeration; 21-26 August; Prague, Czech Republic; 2011 [9] Li Q, Piechna J, Müller N. Thermodynamic potential of using a counter rotating novel axial impeller to compress water vapor as refrigerant. International Journal of Refrigeration.

[10] Borup J, Jensen J. Udvikling af Rotrex turbokompressor til vanddamp compression, Nr.

[7] Albring P. Kältetechnik mit Wasser als Kältemittel, Netzwerk Kältetechnik; 2009

Edinburgh, United Kingdom; 2016. pp. 1178-1184. DOI: 10.18462/iir.gl.2016.1204

#### **Nomenclature**

#### **Author details**

noticed that in the course of the COP curve above the environmental temperature, there are, in addition to the optimal process pressure, also points which have a positive effect on the entire system with a slight loss of efficiency. For both investigated evaporation temperatures in the

 cycle, a subcooling of 5 K is possible with the considered system with a small exception over the entire ambient temperature range. Over much of the environmental temperatures, significantly greater temperature differences are possible. In order to allow a subcooling of 7.5 K over the entire temperature range, further investigations have to be made, which on the one hand consider a larger compressor and on the other hand a further optimized process pressure.

cycle

CO2

*t*

*Greek symbols*

*Subscript*

1\*

**Nomenclature**

*COP* coefficient of performance (kW kW−1)

*COP\** overall coefficient of performance (−)

*GWP* global warming potential (−)

*ODP* ozone depletion potential (−)

*P* electrical power consumption (kW)

*qsub* specific subcooling capacity (kJ kg−1)

*wc* specific compression work (kJ kg−1)

*0* evaporating temperature (°C)

*η* compressor efficiency (−)

0…5 condition point of the CO2

Pumps related to circulating pumps

…4\* condition point of the R718 cycle

*π* pressure ratio (−)

env environment

*q0* specific cooling capacity (kJ kg−1)

*h* specific enthalpy (kJ kg−1)

*m*̇ mass flow (kg s−1)

140 Advanced Cooling Technologies and Applications

*Q0* cooling capacity (kW)

Florian Hanslik\* and Juergen Suess

\*Address all correspondence to<EMAIL_ADDRESS>
Efficient Energy GmbH, Feldkirchen, Germany

### **References**

[11] Murayama S. Report 2014 Kawasaki Heavy Industries, Ltd. Tokyo Office, 14-5 Kaigan

[12] Honke M, Safarik M, Herzog R. R718 turbo chillers and vacuum ice generation–Two applications of a new generation of high speed, high capacity R718 centrifugal compressors. In: 24th IIR International Congress of Refrigeration; 16-22 August; Yokohama,

[13] Madsbøll H. Competitive Chiller Concept with Water as Refrigerant, Danske Køledage;

[14] Süß J. Eine kompakte Kälteanlage mit Wasser als Kältemittel. In: Deutsche Kälte- und

[15] Bitzer. BITZER Software, Version <IP_ADDRESS>9. 2017. https://www.bitzer.de/de/de/soft-

refrigeration cycles using dedicated mechanical subcooling. International Journal of

transcritical

[16] Llopis R, Cabello R, Sánchez D, Torrella E. Energy improvements of CO2

Refrigeration. 2015;**55**:129-141. DOI: 10.1016/j.ijrefrig.2015.03.016

1-chrome, Minato-ku, Tokyo 105-8315, Japan

Klimatagung; 19-21 November 2014; Düsseldorf; 2014

ware/ [Accessed: November 2, 2017]

Japan; 2015

142 Advanced Cooling Technologies and Applications

2013

## *Edited by S. M. Sohel Murshed*

Since conventional cooling techniques are increasing falling short of meeting the evergrowing cooling demands of high heat generating devices, thermal systems, and processes, advanced and innovative cooling technologies are of immense importance to deal with such high thermal management. Hence, this book covers a number of key topics related to advanced cooling approaches, their performance, and applications, including:

	- Compressor cooling systems for industry

The book is aimed at a wide variety of people from graduate students and researchers to manufacturers who are involved or interested in the areas of thermal management systems, cooling technologies, and their applications.

Published in London, UK © 2019 IntechOpen © mahod84 / iStock

Advanced Cooling Technologies and Applications

Advanced Cooling

Technologies and Applications


3.3.3. Organ Weights.

All OW of EAA-100%-fed animals were significantly smaller than StD-fed animals (Table 2).

#### 3.3.4. Blood and Urinary Parameters

EAA-100%-fed mice had lower NLR, lower Hpg and higher serum albumin levels in comparison to StD-fed mice. Noticeably, urinary albumin losses were also the lowest in EAA-100%-fed animals (Table 3).

#### *3.4. Parameter Evaluation after 22 Months*

After 22 months, we were able to measure only BW and BL of the few surviving animals, i.e., four animals fed with StD and nine animals fed with the EAA-100% diet (Table 2). The four StD-fed mice died a few days after these last measurements. The EAA-100% fed mice, albeit showing lower BW, appeared vital, with thick and shiny furs (Figure 1). The last mouse died at the age of 25 months and belonged to the EAA-100% group.


**3. Conclusion**

The radiation induced degradation of neutral phenol solution was studied in the past using end-product techniques [101-105]. There are other few works on mechanistic studies on phenol and other aromatic molecules that were carried out by combining end products and transient detections and it was suggested that the transformations were initiated by hydroxyl radical

Pulse radiolysis of 2,6-dichloroaniline in dilute aqueous solution was investigated. It is known that mono- and dichloroanilines are considered to be highly hazardous pollutants in waste‐ water. These compounds are important chemical intermediates of dye and plant protection agent production. In this investigation, the hydroxyl radical formed in water radiolysis was reacted with 2,6-dichloroanliline forming hydroxy-cyclohexadienyl derivative. The irradiation was carried out at room temperature by a 60Co γ-source, built into a panorama irradiator, with 1.5 kGy h-1 dose rate. The hydroxy-cyclohexadienyl radical in the absence of dissolved O2 partly transformed to anilino radical when oxygen was present in the reaction mixture the radical transformed to peroxy radical. According to chemical oxygen demand measurements, the reaction of one OH*⋅* radical induced the incorporation of 0.6 O2 into the products [109].

The irradiation-induced decolorization and degradation of aqueous solutions of azo dyes and some intermediates (anilines, phenols, triazines) were successful with electron beam irradia‐ tion. The experimental methods were the pulse radiolysis and end-product analysis with HPLC-MS. Demonstrating the practical applicability of this method, a continuous irradiation device has been built. The feed was the dye containing water of red color; the effluent was the colorless liquid during contact time of less than 0.1 second with the high energy electron beam

The other topic is the investigation of the degradation of pharmaceuticals that can be detected in natural waters as emergent pollutants. The radiation-induced degradation of ketoprofen in dilute aqueous solution has been tested. The intermediates and final products of ketoprofen

radiolysis. UV-Vis spectrophotometry and HPLC separation served for identifying the product

The successful degradation of organic molecules being in small concentration in waters, with high-energy irradiation generating radicals already at room temperature prompted us to combine this method with WO. Recently, this hybrid method was used and compared with the classical WO method. Noticeable conversion was observed in phenol oxidation by irradiation already at room temperature in the presence of high concentration of dissolved

In one of the recent studies, WAO of highly concentrated emulsified wastewater was con‐ ducted. These kinds of wastewater usually contain all kinds of organic matters such as surfactants, additives, and mineral oils. They are typical, highly concentrated hardly biode‐ gradable organic wastewaters. This oxidation took place in a 2 L high-pressure autoclave in batch mode. The initial COD concentration of the wastewater was 48000 mg/L. After 2 h of oxidation at 220°C with supply of oxygen 1.25 times more than its theoretical value, the COD was reduced by 86.4%. The temperature seemed to be a key influential factor, especially

solution by pulse radiolysis and gamma

(4 MeV) generated by a linear electron accelerator [110].

degradation were determined in 0.4 mmol/dm3

compounds [111].

168 Wastewater Treatment Engineering

oxygen [112].

attachment to the ring and reaction of O2 with the radicals produced [106-108].

The WO of PWWs became an important disposal technology, which in combination with activated sludge treatment fulfils the strict environmental requirements as well. It works at high temperature and high pressure and often has corrosive reaction mixture; therefore, its intensification is a permanent need. The most promising solutions are the catalytic wet oxidation and the combination of WO with AOP techniques, both of generate the most reactive OH∙ radicals.


*Review* **COVID-19-Associated Lung Fibrosis: Two Pathways and Two Phenotypes, Lung Transplantation, and Antifibrotics**

**René Hage 1,2,\* and Macé M. Schuurmans 1,2**

**Abstract:** COVID-19 can be associated with lung fibrosis. Although lung fibrosis after COVID-19 is a relatively rare finding, the mere fact that globally a very large number of patients have had COVID-19 leads to a significant burden of disease. However, patients with COVID-19-associated lung fibrosis have different clinical and radiological features. The aim of this review is to define the different phenotypes of COVID-19-associated lung fibrosis, based on the medical literature. We found that two phenotypes have emerged. One phenotype is COVID-19-related acute respiratory distress syndrome (CARDS); the other phenotype is post-COVID-19 pulmonary fibrosis (PCPF). Both phenotypes have different risk factors, clinical, and radiological features, and differ in their pathophysiological mechanisms and prognoses. A long-term follow-up of patients with pulmonary complications after COVID-19 is warranted, even in patients with only discrete fibrosis. Further studies are needed to determine the optimal treatment because currently the literature is scarce, and evidence is only based on small case series or case reports.

**Keywords:** lung transplantation; SARS-CoV-2; fibrosis; phenotype hypothesis


Meet the editor

Miana Gabriela Pop was born in Cluj-Napoca, Romania, on September 3, 1988. In 2013, she graduated from the Faculty of Medicine of the "Iuliu Hatieganu" University of Medicine and Pharmacy, Cluj-Napoca, Romania. Miana-Gabriela Pop is a general surgery resident and university assistant in the Department of Anatomy and Embryology of the University of Medicine and Pharmacy "Iuliu Hatieganu," Cluj-Napoca, Romania.

Passionate about surgery, she completed her residency training through valuable professional fellowship programs in the field of hepato-bilio-pancreatic surgery and minimally invasive procedures in France (Centre Hepato-Biliare Paul Brousse, Paris, IRCAD Laparoscopic Training Center, Strasbourg) and the Netherlands (the Netherlands Cancer Institute—NKI, Amsterdam). This scientific activity has resulted in the publication of seven anatomy and surgery chapters and 11 scientific papers.

Contents

**Section 1**

Biomarkers

**Section 2**

**Section 3**

*by Miana Gabriela Pop*

*by Miana Gabriela Pop*

A Clinical Surgical Approach

*Fabiana Lima Marques, Robson Dettman Jarske and Octavio Meneghelli Galvão Gonçalves*

Stem Cell Markers in Colon Cancer

**Preface III**

Introduction **1**

**Chapter 1 3**

Molecular Surgical Pathology **7**

**Chapter 2 9**

Clinical Surgery **21**

**Chapter 3 23**

**Chapter 4 43**

**Chapter 5 57**

Preoperative Assessment of Functioning Benign Adrenocortical Tumors:

*by Bruno Costa do Prado, Alana Rocha Puppim, Jose Tadeu Carvalho Martins,*

Laparoscopic Live Donor Nephrectomy: Techniques and Results *by Maroun Moukarzel, Charbel Chalouhy, Nabil Harake and Freda Richa*

Prenatal Diagnosis and Management of Sacrococcygeal Teratomas

*by Anca Budusan, Horatiu Gocan and Roxana Popa-Stanila*

Introductory Chapter: General Surgery in the Era of Modern Molecular


Contents

#### **Preface XI**

Preface

cultural pluralism.

Bilingualism and multilingualism as the object and subject of scientific inquiry is an enigmatic and intriguing phenomenon. Bilingualism is indeed phenomenal (in the etymological sense of the word), in that even though so much research is done and so much knowledge is generated on bilingualism and multilingualism, there is still so much that is unknown and so much to be

Who would have thought, several decades ago, that bilingualism as the ability to use two or more languages confers on the bilingual individual cognitive advantages over the monolingual individ‐ ual that makes bilingualism not only palatable but desirable and, indeed, indispensable? Today, the avalanche of empirical evidence of research findings to this effect, presented in this book, makes an assertion that bilinguals have enormous competitive advantages over monolinguals in

In the Europe of yesteryears, the paradigm of "one nation one language" (the monolingual habi‐ tus) was so dominant and fashionable as a nation-building ideology that multilingualism was considered a curse, a demon that had to be exorcised. This led to the voluntary and involuntary endangerment, attrition, or death of minority languages. Today, the abundance of research find‐ ings of advantages for multilingualism or societal bilingualism has led to a rethinking of the issue. This, coupled with considerations and acknowledgement of the value of language, any language and every language as an invaluable treasure of the manifestation of the human mind and human knowledge whose loss or death impoverishes humanity immeasurably, has led today to the de‐ construction of the paradigm of monolingual habitus by the European Union's language policies

The nine chapters of this book provide elucidations of the issue of benefits of bilingualism and multilingualism and further provide original research findings on developments in the areas of psychological dimensions of bilingualism and bilingualism in information retrieval systems. Thus, there is still so much to be learned and to be known about the phenomenon of bilingualism and multilingualism to make another book, this book, relevant, worthwhile, and necessary. It is preceded by an introduction containing topics that mirror the issues discussed in the book.

The section presents the benefits of bilingualism to the individual and the advantages of multilin‐ gualism to society and the nation followed by two case studies of multilingualism: aspects of bi‐ lingualism and multilingualism in Europe and the evaluation of achievements of bilingual policy in Columbia, South America. The section establishes the benefits of bilingualism and multilin‐ gualism, and the case studies that follow examine how, considering the phenomenon of bilingual‐ ism as a desirable "good," nations (in Europe and Latin America) accommodate what appears ostensibly as the adverse side effects of an otherwise useful and much-needed medication for the arduous but rewarding task of nation building within an ideological paradigm of linguistic and

in favor of linguistic diversity and the preservation of rights for minority languages.

**Section II: Advantages and Case Studies of Bilingualism and Multilingualism**

known that the much we know about bilingualism may not be much after all.

the educational system, an incontrovertible fact.

Chapter 8 **Cross-Lingual and Cross-Chronological Information Access to Multilingual Historical Documents 143** Biligsaikhan Batjargal

#### Chapter 9 **Innovative Multilingual CAPTCHA Based on Handwritten Characteristics 163** Maha Hamad Aldosari