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Cool It-July 2016




 Master-Bilt® Refrigeration News & Product Information



Reclaim Wasted Heat!

It’s the middle of summer and one subject you probably don’t want to think about is heat. But what if you're wasting an energy efficient, virtually-free source of heat? Heat you could use for hot water, heating workspaces and other applications. If you have a rack refrigeration system or are planning to incorporate one into your foodservice or retail operation, you can save on your energy bill by putting its discharged heat to work. The process is called heat reclaim.

If you’ve ever been next to an outdoor condensing unit while it’s in the run cycle, you’ve probably felt the heat it gives off. Usually this heat is rejected by the system and dissipates into the outdoor air. However, there are ways to more efficiently use this source of heat.

As warm discharge gas exits the compressor, it may be passed through a plate heat exchanger, a device that’s used to transfer heat between fluids without allowing them to mix, and used for several different applications.

july16-heat-exchanger

A plate heat exchanger commonly used in a rack refrigeration system is composed of metal plates that transfer heat between two fluids.

For example, pre-heating hot water is a very common approach, particularly for larger foodservice operations. Municipal water temperatures typically fall into the 50° to 70°F range. Water temperatures around 170°F are usually considered as best for washing dishes, clothing, bathing, etc. With the lack of heat reclaim, typical water heaters take the entire burden of raising the water temperature as much as 120°F. Large facilities consuming hundreds of gallons per day face substantial energy costs based on this utility alone. Pre-heating hot water with what is otherwise wasted energy can decrease demand on hot water heaters as much as 50 percent. A simple heat reclaim valve incorporated into the condensing unit diverts this warm refrigerant gas into a secondary heat exchanger which pre-heats water to temperatures ranging from  100°F to 110°F at no cost. The water heater now must heat water from 110°F to 170°F or about half of what it would be required to do otherwise.

We should also mention that a plate heat exchanger is not always utilized in pre-heating water. In some cases, a hot water tank is used to pre-heat water since the tank has a type of built-in heat exchanger.

Other examples of heat reclaim include simple air-over-heat exchangers for heating workspaces or warming glycol which is useful for heating floors or sidewalks. The opportunities are plentiful and the applications go far beyond what is described here.

It should be noted that heat reclaim is only available during the run cycle of the compressor and there is little or no heat available when compressors are in the idled or off state. Heat reclaim systems do incur some upfront costs and you should evaluate these on the front end to determine if the system is justified or not. For large refrigeration systems such as parallel racks, the payback is typically justified as these systems consistently have compressors in the “running” state.

For more information on how to incorporate heat reclaim into your refrigeration system, contact us at 800-647-1284 or at sales@master-bilt.com

 

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