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View Subscription Details: Letter ( 10/14/2010 ) - HTML Format

Cool weather

 

When is the best time of the year to save energy? Periods of cool weather is the best time to improve the efficiency of refrigeration plants.

Why?

To run a refrigeration plant efficiently, it should be operated at optimum set points. The best set points of the condensing pressure, suction pressure, hot gas defrosting, etc. should be determined and implemented. However, different ambient conditions require different effort to implement these set points.

Example.

During summer operation ambient air has wet bulb temperature of 75°F. Optimum condensing pressure at these conditions is 150 psig. However, condensers of our plant are undersized and condensing pressure is 178 psig. To achieve optimum condensing pressure and to save energy, condenser capacity should be doubled. This action requires significant investment and many companies will not invest in additional condenser capacity.

During period of cool weather, optimum condensing pressure was determined as 80 psig. However, there are several barriers to run a refrigeration plant at such low condensing pressure. These barriers are hot gas defrosting, liquid injection oil cooling, oil carry-over, etc., but every barrier has a solution. During fall, winter and spring many refrigeration plants run at minimum condensing pressure of 110 - 120 psig, because operation of these plants are not optimized. Typically, optimization of the refrigeration plant operation will require a small investment that is 10 - 20 times less than investment in additional condensers.

Mother Nature gives us cool weather and the opportunity to achieve significant energy savings without significant capital investments. I suggest to every company to use this opportunity.

 

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