REFRIGERATION
Shell and Tube WaterCooled Condensers T
here are a number of different types of condensers that can be used to reject the heat from a refrigeration system, and these can reject the heat to the ambient air, water or any other type of fluid that is availablee at a low enough temperature. For the current discussion, let’s focus on shell at to and tube condensers that reject their heat on. water, or another form of aqueous solution. Water-cooled condensers are typically designed and connected into the system in a counterflow arrangement. This means that the fluid flows in one direction and the refrigerant travels in the opposite direction.
Inside a shell and tube condenser, the refrigerant flows in the shell from top to bottom. This makes sense because liquid is denser than vapour and will drop to the bottom of the shell where it can then be further cooled by the incoming water.
With this method, the coldest water supply is used to provide refrigerant subcooling. This would not be possible if the condenser was piped for a parallel flow. Also, it makes less sense to use the coldest water to cool the incoming discharge gas. Air-cooled condensers are also designed using a counterflow arrangement.
The tubes carry the fluid that is used as the cooling medium. Since the refrigerant flows within the shell, the shell side is relatively warm. Therefore, condensation is not likely to take place. This provides the added
WORKING WITH WATER, AND OTHER FLUIDS Appropriate aqueous solutions include mixtures of propylene glycol, ethylene glycol or calcium chloride with water. And there are many other types of glycols that may be used for applications where the condenser water temperature can drop below the freezing point of water. Of course, if it is known that the temperature of the condensing medium will not fall below 33°F, then 100 per cent water can be used to carry the heat away from the system. In addition to being less expensive than a glycol or other chemical-based fluid, water also provides better heat-transfer characteristics than aqueous solutions.
Phil Boudreau
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M e c h a n i c a l
Phil is the Ontario sales manager for Bitzer Canada Inc. and provides training and technical support for Bitzer’s clientele. He can be contacted at pboudreau@bitzer.ca.
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