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Thermal efficiency

Most buyers understand that heaters with high thermal efficiency use less fuel than those with lower efficiency. So competitors usually claim their heaters have high thermal efficiency. But what is high? Competitor heaters rarely come close to the numbers we claim: 85% (90% with our Stackpack heat exchanger).

We have found that our heaters have significantly higher efficiency than other heaters. Even a 2% advantage provides worthwhile money savings.

Our Excel spreadsheet Heat Analysis (click to download) makes it easy to compare the fuel savings from heaters with various thermal efficiencies. You type in numbers applicable to your plant and the price you are paying for fuel and the program calculates what savings you can expect.

Actual thermal efficiencies are easy to determine and compare. Remember, the heat in the heater exhaust gas vented into the atmosphere is wasted energy. It can be used to find actual thermal efficiencies.

First measure the temperature of the exhaust gas, also known as stack temperature. Be sure to insert the stem of the thermometer into a port hole near the base of the stack to get the true temperature of the exhaust gas. Then find the thermal efficiency that matches that temperature using our chart (click on the chart for a larger image) that converts stack temperature to thermal efficiency.

We recently made exhaust gas measurements on a new Heatec hot oil heater in our test pit. The heater had a Stackpack heat exchanger and was undergoing its final checkout routine before delivery to the customer. We recorded the temperature below and above its Stackpack.

The temperature below the Stackpack is key to the thermal efficiency of the heater alone. The temperature above the Stackpack is key to the thermal efficiency of the heater plus the extra efficiency gained from the Stackpack.

Now let’s use those measurements to determine its thermal efficiencies. The temperature reading below the Stackpack heat exchanger was 500 degrees F. The chart shows a thermal efficiency of 88% for that temperature. The temperature above the exchanger was 381 degrees. The chart shows a thermal efficiency of 91 percent for that temperature.

So the thermal efficiency of this heater is actually better than our claims. We doubt that competitive heaters can match those numbers. But you may wish to check them for yourself.