WaterFurnace International of Fort Wayne, Indiana wishes to control an electronic expansion valve (EEV) for use in a geothermal heating and cooling system. Electronic expansion valves provide higher system efficiency, can be used on different tonnage systems and can be controlled more precisely than other types of expansion valves. WaterFurnace desires an electronic control board to be designed to interface with temperature and or pressure sensors located in the geothermal system and use the output of the sensors to aid in the control of the EEV. The valve must control the temperature of the refrigerant to 10°F +/- 2°F of superheat at the inlet of the compressor.In order to begin the design process, models of the system were constructed to better understand its functionality. A system was tested at WaterFurnace. The test results were then used as baseline for modeling and the development of the control. With a model of the system, a simulation was set up to test this method and compare its results to those from the testing using the same input data. The simulation of the control method supported the initial testing results and the design selection process began.
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