Research On The Heat Flux Variation In The Ground Source Heat Pump System Application Area

Heat and mass transfer in the soil and on the ground surface are stuied in the microclimate where ground heat exchanger are buried.Heat flux on the ground surface are emphasized.A model to research the heat flux in the microclimate combined with groud source heat pump system and vegetationon the ground surface is put forward.Through experiment and simulation,heat flux caused by underground heat exchanger and vegetation transpiration are compared.Firstly,energy equations of air,vegetation and soil were established,laying for a foundation of the theoretical analysis of system running characteristic in different seasons.Secondly,calculation method to all the main heat fluxes were analyzed elaborately.Heat fluxes caused by ground heat exchanger and vegetation transpiration were focused on.Then,the two stressed heat fluxes were analyzed elaborately both in experiment and in simulation.Conclusions were drawed in the following.Temperature increase underground in summer averagely is 1~oC,temperature decrease averagely in winter is 0.6 ~oC.Heat released to the soil in summer is 1582 GJ,extracted from the soil is 1022 GJ,so totally heat released to the soil is 560 GJ yearly,the ratio of thermal imbalance is 35.4%.In the area where underground heat exchanger is buried,heat flux from the soil to the ambient environment,in summer,ranged from-89.1W/m~2 to 92.7 W/m~2.In transition season,variation range is-41.9W/m~2~37.9 W/m~2,In winter,ranged from-99.5 W/m~2 to 92.5 W/m~2.Portable photosynthesis equipment was used to test transpiration rate of typical vegetation on measurement day.For vegetation heat flux,photinia was 88.3 W/m~2,for berberis was 90.3 W/m~2,for Chinese little leaf box was 73.0 W/m~2,for camphora was 153.2 W/m~2,for weeping willow was 195.3 W/m~2.Simulation software is used to analysis the heat flux caused by ground heat exchanger and P-M equation was used to investigate the vegetation transpiration heat flux.Due to vegetation transpiration heat flux can offset part of the heat flux caused by underground heat exchanger in cooling season,it is suggested to plant more vegetation on the ground surface where underground heat exchanger is buried.