Experimental study on heat transfer performance of new gravity heat pipe in geothermal utilization

Abstract

In this paper, a set of heat pipe performance testing device is built for a new gravity heat pipe with internal tubes, fins and charged with CO2 liquid and nano-fluids mixtures. The influence of the length to diameter ratio of the heat pipe, the different cold and heat source temperature and the flow rate of the cold and heat loop on the heat transfer performance of the heat pipe is discussed, respectively.The results show that, for the heat pipe itself, the heat pipe has a good heat transfer performance when it has a smaller ratio of length to diameter. The increase of the heat source temperature is the main factor affecting the equivalent heat transfer coefficient of the heat pipe. With the ratio of water flow increase,whether the heat or the cold flux,it has the same effect on the heat transfer rate of heat pipe. The increase of the flow rate strengthens the performance of heat pipe. It is worth noting that, change of the cold source temperature should be referred to the heat source temperature, it will be a better effect with small heat flux density. When the heat source temperature is higher, the lower the cold source temperature, the greater the heat loss and the poor heat transfer performance of the heat pipe.