Electrical Testing
process heat system Photo credit: Nostal6ie/iStock/Thinkstock

Improve System Efficiency by Addressing Waste Heat

Actively search out sources of waste heat and pursue techniques to recover the wasted heat.

What kind of gas mileage would you expect if you were driving your car with one foot on the gas and the other on the brake? The results from this approach would be pretty poor.

Many facilities have a similar dynamic going on with “waste heat.” Continuing on with the car example, if you look under the hood (and understand what you’re looking at), you’ll see some waste heat recovery techniques in play.

What kinds of techniques might your facility use? Before you can really answer that question, you need to identify the waste heat sources and quantify the amount of waste heat from each source.

Once you have that information, look at processes or equipment that requires additional heat. Many waste heat recovery techniques involve providing at least some of that heat by redirecting waste heat.

Consider a plant that had a small annealing furnace. This furnace used outside air, which had to be preheated in the winter just to get up to the inside air temperature. Meanwhile, several hot process situated nearby were ducting their waste heat air to the outside (and pulling already heated ambient air out as well). Some reducting (along with pressure controls and approval by the boiler inspector prior to actual implementation) changed much of the waste heat into process-used heat.

Another plant had a row of small cooling towers outside the building. A closed piping system ran through the towers. The water cooled a manufacturing process and was simply circulated through the pipes. Hot water ran to the cooling towers, and cooled water ran back to the equipment that needed cooling. This system is very much like the cooling system in a car, except the car has a radiator instead of a row of cooling towers.

The plant had recently hired a new plant engineer, and he noticed almost none of the pipes in the ceiling were color coded or even labeled. So he hired an industrial services firm to identify the pipes. In the process of identifying these, they were amazed to discover that the uninsulated cooling tower return pipe was run between two hot water pipes for about thirty feet. And the pipes were touching each other, causing a loss of energy in the heated water while degrading the cooling system.

Don’t wait to incidentally find instances of gas and brake. Actively look for them. Where are you running hot air, water, etc., and where are you running cooling air or water supply? Where are you generating heat for use, and where are you exhausting heat instead of using it?

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