Thermal modeling and experimental research of a gas engine-driven heat pump in variable condition

Abstract

In order to analyze the influence of various factors on the system performance of the gas engine-driven heat pump system with waste heat recovery, theoretical model of a gas engine-driven heat pump is conducted in this paper. The thermal modeling of the gas engine-driven heat pump including both the heat pump and the gas engine system was performed and the system performances under different operating parameters were simulated. The results show that the engine speed and the outdoor air temperature affected the system performance significantly. With the engine speed increasing from 1400rpm to 2000rpm, the heating capacity increased by 26.9% while system primary energy ratio (PER) decreased by 17.6% for the air temperature of 10°C. When the outdoor air temperature reduced from 10 to 2°C, the heat capacity reduced by 14.6% but the system PER decreased by 11.8% with the engine speed of 1800rpm. The water inlet temperature act insignificantly on heating capacity, while it had some influence on the system PER. With the water inlet temperature increasing from 38 to 44°C, the system PER decreased by 5.7% and 4.4% for the outdoor air temperature of 10 and 2°C, respectively. The experimental test is also carried out to validate the simulation models. The comparison of modeling results and the experimental measured values for various amounts of the heating capacity, PER, waste heat recovery and the percentage of heat recovery showed 4.8%, 4.6%, 6.7% and 5.6% average difference percentage, which indicated an accepted agreement. From the perspective of energy savings, the gas engine-driven heat pump should be operated with engine speed as low as possible in the case of meeting the heating requirements.