Instrumentation for Performance Measurements of Heat Pumps With Commercial Desuperheaters

The current project is an extension of the original “ETME 475-Mechanical Systems Design” course project with a new National Instruments data acquisition board, a newly developed LabVIEW data acquisition program, and with a more realistic heat transfer loop. The study covers performance of our heat pump operating in A/C mode as well as in heating mode with a commercial desuperheater (a cross-flow heat exchanger). For this project, the experimental set up consisted of a desuperheater spliced into Trane XL1000, 2-ton, 10-SEER heat pump and a heat transfer loop with a 72-liter hot water storage tank. The instrumentation consisted of seven copper-constantan thermocouples and a LabVIEW-based computer data acquisition system. The thermocouples were used to measure refrigerant, water, indoor air and ambient air temperatures. The LabVIEW based computer data acquisition system was used to record temperatures. Indoor airflow rate was previously measured using Alnor LoFlo balometer. Results indicate that, depending on the water temperature in the desuperheater, heat pump Coefficient of Performance (COP) dropped 6–18% in A/C mode and 8–38% in heating mode. Again depending on the average water temperature in the desuperheater, the desuperheater efficiencies ranged from 12% to 27% for cooling and 11% to 39% for heating. Although even modifying an existing LabVIEW program was a challenge, the student who worked on it and the author has gained very valuable experience and enjoyed the work.