Chilled Water In HVAC-00-1276
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by: Eng.Mohamed Fawzy
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Word Count: 320
The common 3 essential parts of the chilled water systems is :
-The Cooling Coil.
-The evaporator.
-The chilled water pump.
1-The cooling coil:
In the air side loop, a cooling coil is used to cool and dehumidify the conditioned air.as mentioned,the cold fluid transferring through the tubes of the coil may be either water or liquid refrigerant.
Heat energy transfers from a warmer substance to colder substance .Therefore,in order for heat to be transferred from the air,the fluid flowing through the tubes of the cooling coil shall be colder than the air passing over the cooling coil.
An example of chilled water at (42 F) flows through the coil, absorbing heat from the air.the cold water leaves the coil at a warmer temperature (57 F) .
It has also mentioned that the water transferring through the cooling coil must be colder than the air passing through it.
2-The evaporator:
The Evaporator is an heat exchanger which transfers the heat energy from the warm chilled water which come from the cooling coil.Shell and tube evaporator is the common used in the chilled water applications.
An example of a shell and tube evaporator which used to cool chilled water come from the coil at (57 F ) back to the desired supply water temperature (42 F).
3- The Chilled water pump.
The chilled water pump is a device which used to develops the pressure which important to overcome the resistance to the flow of the cold water in the piping system.
chilled water pumps can be classified into two groups according to the way they develop this pressure.
The first is called "positive displacement pumps" which contain reciprocating,gear,vane and rotary pumps.they are used only in specialized cases in H.V.A.C. work and will not explained in this article.
The second is called "Centrifugal pumps" which is generally used in chilled water systems.It is very reliable,rugged and efficient.
The centrifugal pump increases the pressure of the water by first increasing its velocity,and then converting the velocity energy to pressure energy.
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