Exergy Analysis Of Ground Source Heat Pump Systems Based On TRNSYS

Ground source heat pump(GSHP)technology is becoming more and more widely applied for its extordinary efficiency,energy conservation and environmental friendliness.At the same time exergy analysis which considers not only quantity of enegy but also quality is arising much discussion around the world.This paper applies exergy analysis to GSHP systems,assessing the performance of GSHP systems with indexes as exergy efficiency,exergy loss,exergy loss ratio,etc.This paper studies the parameters that influence the exergy performance of GSHP systems as well.A public building with a ground coupled heat pump system in Wuhan is modeled using TRNSYS.The hourly ambient air temperature is considered as the reference temperature.The simulation results show that the exergy efficiency of the GSHP system is 9.0%in cooling season and 6.1%in heating season.Exergy loss of the system in cooling and heating season is 5.58x10~8kJ and 3.95x10~8kJ.Based on the TRNSYS model,this paper proposes 5 optimized designs for the GSHP system that differs in the control strategies such as the time schedule,circulating water flow rate and constant/variable-frequency heat pumps.According to the simulation,exergy efficiency of the 5 cases range from 8.3%to 10.4%in cooling season and 5.0%to 6.9%in heating season.The exergy loss of the systems range from 69%to 107%that of the original GSHP system in cooling season,and from 49%to 89%in heating season.Ignoring the influence of transition seasons,the annual exergy efficiency of the original system and the5 cases are 7.7%,8.1%,8.6%,7.1%,7.4%and 9.2%,and the annual exergy loss are9.52x10~8kJ,9.48x10~8kJ,8.95x10~8kJ,7.15x10~8kJ,6.97x10~8kJ and 5.77x10~8kJ,respectively.Besides all above,this paper also explores the effect of different reference state on exergy analysis and the exergy performance of GSHP systems.