140-180°F WATER

STEAM EXHAUSTED

IN COMBUSTION GAS = LOSS OF

ENERGY

HIGH EFFICIENCY HYBRID WATER HEATER

For many years loyal Sioux customers asked Sioux to develop a direct-fired water heater designed specifically for use in the concrete industry, that would have the traditional Sioux high-quality, and other features needed for concrete production. In 2009 Sioux built its first direct-fired water heater which included a properly engineered combustion chamber and other features to obtain maximum efficiency. However, after extensive testing, it became obvious that the traditional direct fired design did not provide acceptable efficiency at higher water temperatures needed in the concrete industry. This is because at higher temperature, the heated water evaporates and passes out the stack with the combustion gasses, resulting in a huge loss of energy and unacceptable efficiency. So Sioux did not introduce this traditional direct-fired heater in 2009.

At WOC 2012, Sioux introduced a revolutionary design that resulted in numerous benefits for concrete producers, utilizing a direct-fired section, plus two other sections. In this design, the media section ensures high overall efficiency by capturing remaining exhaust heat but the temperature of the water is low, so essentially none of the water turns to steam. The second section captures combustion gas heat in the bottom of the heater, and the third section (the coil section) allows water to be heated to the final temperature in the heating coil where none can evaporate, achieving a high temperature (up to 208 °F) without evaporation.

Sioux Hybrid vs. Direct-Fired Water Heaters: Efficiency Comparison

Sioux’s Hybrid Water Heater captures nearly all of the heat of combustion. High water temperature is reached in the coil rather than in the media section, eliminating significant losses due to steam escaping from the media section.

In a typical direct-fired water heater, significant energy is lost when the water droplets turn to steam and exit the system with the exhaust gasses. Above is a photo of a ready-mix facility where a traditional direct-fired water heater is operating, showing the escaping steam.

HIGH EFFICIENCY HYBRID WATER HEATER

BrandEfficiency at Various Discharge Water Temperatures

120°F 135°F 140°F 150°F 160°F 180°F 200°FSioux Hybrid 98.7% 98.7% 98.7% 98.7% 97.3% 95.5% 94.9%Brand A 89.4% 76.2%Brand B 77.1% 70.3% 66.3%Brand C 57.1%

SIOUX CORPORATIONemail@sioux.com • www.sioux.comOne Sioux Plaza • Beresford, South Dakota 57004-1500 USATel: (605) 763-3333 • Fax: (605) 763-3334

Sioux’s engineers field tested the Sioux Hybrid and competitive water heaters at several ready-mix plants, monitoring energy input and output using gas and water meters, thermocouples, and a data acquisition system, to calculate actual (not estimated) efficiency achieved in actual field conditions. These results agree with the initial testing done at Sioux in 2009, and confirm that a traditional direct-fired heater does not provide nearly the efficiency claimed, when heating water to the temperatures needed for concrete production.

Water that is heated in the heater that escapes in the form of steam with combustion gasses is not useful in the production of concrete, and is a total loss of the system, resulting in lower actual efficiency vs. expected efficiency.

Another significant loss is caused by not providing a properly engineered combustion chamber, which is essential to ensure maximum combustion temperature prior to entering the heat exchange sections. Otherwise a significant portion of the energy content of the fuel is lost.

Field Testing

For some designs using a rule of thumb, such as measuring stack temperature, can give a rough idea of efficiency. For a direct-fired heater where significant energy is lost due to steam escaping with combustion gasses stack temperature gives a significantly distorted efficiency value.

Efficiency is determined from the following equation:

Efficiency = useful energy out / total energy consumed.