cooling water runs through the condenser because of the corrosive nature.
cooling water runs through the condenser because of the corrosive nature.
why does cooling water run through the condenser?
the corrosive nature
cooling towers originated in the 19th century through the development of condensers for use with the steam engine. condensers use relatively cool water, via various means, to condense the steam coming out of the cylinders or turbines. this reduces the back pressure, which in turn reduces the steam consumption, and thus the fuel consumption, while at the same time increasing power and recycling boiler-water. however the condensers require an ample supply of cooling water, without which they are impractical. the consumption of cooling water by inland processing and power plants is estimated to reduce power availability for the majority of thermal power plants by 2040–2069. while water usage is not an issue with marine engines, it forms a significant limitation for many land-based systems.
cooling tower
the complete channel configuration consists of a condenser channel with inlet and outlet and an evaporator channel with inlet and outlet. these two channels are separated by the hydrophobic, micro porous membrane. for cooling, the condenser channel is flooded with fresh water and the evaporator e.g. with salty feed water. the coolant enters the condenser channel at a temperature of 20 °c. after passing through the membrane, the vapour condenses in the cooling water, releasing its latent heat and leading to a temperature increase in the coolant. sensible heat conduction also heats the cooling water through the surface of the membrane. due to the mass transport through the membrane the mass flow in the evaporator decreases whilst the condenser channel increases by the same amount. the mass flow of pre-heated coolant leaves the condenser channel at a temperature of about 72 °c and enters a heat exchanger, thus pre-heating the feed water. this feed water is then delivered to a further heat source and finally enters the evaporator channel of the md module at a temperature of 80 °c. the evaporation process extracts latent heat from the feed flow, which cools down the feed increasingly in flow direction. additional heat reduction occurs due to sensible heat passing through the membrane. the cooled feed water leaves the evaporator channel at approximately 28 °c. total temperature differences between condenser inlet and evaporator outlet and condenser inlet and evaporator outlet are about equal. in a pgmd module, the permeate channel is separated from the condenser channel by a condensation surface. this enables the direct use of a salt water feed as coolant, since it does not come into contact with the permeate. considering this, the cooling-or feed water entering the condenser channel at a temperature t1 can now also be used to cool the permeate. condensation of vapour takes place inside the liquid permeate. pre-heated feed water that was used to cool the condenser can be conducted directly to a heat source for final heating, after leaving the condenser at a temperature t2. after it has reached temperature t3 it is guided into the evaporator. permeate is extracted at temperature t5 and the cooled brine is discharged at temperature t4.
membrane distillation