Optimal design and operation of district heating system coupled with open loop heat exchanger and heat pump

Abstract

At present, the application of the traditional heating mode of extracting geothermal water is limited due to the difficulty of reinjection into sandstone formation, and the deep geothermal single well system of only taking heat without water has become a research hotspot. Even though deep borehole heat exchangers has been applied in some practical projects in recent years, it has not been widely used because of its low heat extraction rate and the decrease of heat extraction rate caused by heat accumulation during the system operation. In contrast, the open loop geothermal single well system has convective heat transfer and mass exchange with the formation, the heat extraction rate is much higher than that of the close loop system. The optimal design of the ground heat pump system coupled with the open loop geothermal single well system is the key to obtain the high heat extraction rate of single well.
In this paper, a ground heat pump system coupled with an open-loop single well system is designed and the mathematical model is established. The optimal design of coupling different regions, open loop heat exchanger system, ground heat pump system and terminal users is carried out. The optimal matching parameters of plate heat exchanger and room radiator are obtained and optimal operation mode based on the above design is proposed.