View Full Version : Heat Balance number
10-31-2009, 11:57 PM
What do you guys plug in for heat of compression when doing a heat balance on a chiller with an open drive motor?
11-01-2009, 03:25 PM
Unless I'm understanding the question wrong (and I've NEVER been guilty of that!), the heat of compression can be figured off of a p-h diagram as btu's per pound. It won't change from open drive to hermetic. Overall heat rejection required will be different for the condenser/cooling tower because you have to get rid of the motor heat thru the condenser on a hermetic, but saturated temps aren't affected.
If I am understanding the question, I still don't have a fixed calculation that I could pass along, but you can convert total KWH to btu's at full load and add that to the full load tonnage and get very close to total heat rejection. Without knowing the KW/ton, a nice round figure of .55 or .60 on a normal late vintage machine should bring it into the ballpark. Then take that much heat away from the hermetic calculation, and that's what the condenser and cooling tower on an open drive machine have to reject.
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