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View Subscription Details: Letter ( 12/19/2011 ) - HTML Format

To steam or not to steam

 

A few years ago, I went to a production facility to evaluate the performance of their refrigeration plant. During the first meeting with the company representatives, I mentioned that their refrigeration plant operates inefficiently. The chief engineer was very surprised by my statement because at this point they had not provided me with any information about their refrigeration plant. How did I find that the refrigeration plant had inefficient operation?

This meeting happened during the fall, the outside temperature was around 40°F. When I came to the meeting, I saw that the steam was going up from the evaporative condensers of the refrigeration plant. Visible steam can be produced when cooling water temperature of the evaporative condensers is significantly higher than the outside temperature. Relatively high water temperature means that the refrigeration plant is operating at an unnecessary high condensing pressure. I was right, the mentioned refrigeration plant was operating at condensing pressure of 130 - 140 psig to provide adequate hot gas defrosting. I suggested to the chief engineer to properly adjust the hot gas defrosting and to lower the operating condensing pressure to the range of 80 - 90 psig. Since this adjustment, the mentioned facility has saved a lot of energy by operating the refrigeration plant at optimum condensing pressure. I have driven by this facility many times and it was nice to see that it does not steam any more.

Actually, everybody can check the steaming of their evaporative condensers. When outside temperature is between 35°F and 50°F, have a look at your evaporative condensers. If you can see the steam, it means that your refrigeration plant operates at condensing pressure higher than optimum. Most likely this pressure can be lowered and a lot of energy can be saved.  

 

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