Chilled Water System



Posted: Tuesday, April 28, 2009

by Mohamed Fawzy
consulting

In this article we will explain an important component of the H.V.A.C. systems which called "Chilled Water system".

The most 3 important 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 supply air.as mentioned,the cold fluid flowing through the tubes of the coil may be either water or liquid refrigerant.

Heat energy flows from a higher-temperature substance to lower-temperature substance .Therefore,in order for heat to be transferred from the air,the fluid flowing through the tubes of the cooling coil must be colder than the air passing over the tubes and fins.

Let me give you an example of chilled water at (42 F) flows through the coil, absorbing heat from the air.the water leaves the coil at a warmer temperature (57 F) .

It has also mentioned that the water flowing 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 from the return chilled water from the cooling coil.Shell and tube evaporator is the most used in the chilled water applications.

An example of a shell and tube evaporator which used to cool chilled water returns 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 provides the pressure necessary to overcome the resistance to the flow of the chilled water in the piping system.

Pumps can be classified into two groups according to the way they develop this pressure.

The first group is called "positive displacement pumps" which include reciprocating,gear,vane and rotary pumps.they are used only in specialized cases in H.V.A.C. work and will not discussed in this article.

The second group 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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Mohamed Fawzy is a mechanical engineer who has a good experience in air conditioning,fire protection and plumbing systems design.

He is currently working as a design engineer for allied consultant company since 2005 till now.He enjoys helping others succeed and he teaches his strategies in the design via his lessons

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