Experimental Research On Heat Transfer Performance Of Heat Pipe In Geothermal Utilization

With the development of society,the energy problem has become more and more serious,and the voice of energy conservation is also growing.Heat pipe is an efficient heat transfer component,which can achieve the purpose of heat transfer without external force.In recent years,it has been applied in various situations of comprehensive utilization of thermal power and waste heat recovery.In order to use geothermal energy continually and effectively,In this paper,the performance of a new type of finned heat pipe filled with carbon dioxide and magnetic fluid mixture has been tested,and an experimental platform has been set up.The effects of different heating and condensing conditions,such as heat source temperature,cold source temperature,volume flow rate of hot fluid,volume flow rate of cold fluid and the length-diameter ratio of different sizes heat pipes on heat transfer performance were studied by means of experimental research.In the experiment,the relative heat balance of system is verified by conservation of the heat generated by the heating device and the heat absorbed by the cooling device.In this paper,the equivalent thermal conductivity of heat pipe is taken as the evaluation index of heat transfer performance of heat pipe.By changing the conditions of different influencing factors in the experiment,the heat transfer characteristics of heat pipe,such as axial temperature distribution,variation of axial temperature difference,heat flux density of heat pipe,running thermal resistance and equivalent thermal conductivity,are obtained,and then summarize the change rules of heat transfer performance of heat pipe.The experimental results show that the axial temperature of heat pipe shows good uniformity as a whole,but there is a temperature slip at the bottom and top of evaporation section and the bottom of the condensation section of heat pipe.The increase of cold and heat source temperature increases the axial temperature of heat pipe.The influence of the volume flow rate of hot fluid on the axial temperature of heat pipe should take into account the synergistic effect of heat source temperature.The volume flow rate of cold fluid is negatively correlated with the axial temperature of heat pipe.The axial temperature difference of heat pipe is positively correlated with the change of heat source temperature and negatively correlated with the change of cold source temperature.With the increase of volume flow rate of cold and hot fluids,the axial temperature difference of heat pipe increases.The thermal resistance of different heat pipes ranged from 0.0017 K/W to 0.0071K/W,and the equivalent thermal conductivity ranged from 22.12 kW/(m·K)to 150.92kW/(m·K).The thermal power of heat pipe rises with the increase of heat sourcetemperature and the decrease of cold source temperature.Under the lower heat flux density,with the decrease of cold source temperature,the axial temperature difference of heat pipe increases,the thermal resistance increases,and the equivalent thermal conductivity of heat pipe decreases.With the raise of heat flux density,the thermal resistance increases and the equivalent thermal conductivity of heat pipe decreases.The volume flow of cold and hot fluids is positively correlated with the heat transfer performance of heat pipe.Analysis the influence rules of different sizes of heat pipe are obtained: when the length of heat pipe increases,the axial temperature difference of heat pipe increases,and the heat transfer performance increases;with the decreases of diameter of heat pipe,the axial temperature difference increases,and the heat transfer performance of heat pipe increases,that is,the larger ratio of length to diameter of heat pipe,the heat transfer performance is better.