Study Of Auxiliary Heat Dissipation Based On TRNSYS Soil Source Heat Pump Cooling Tower Connected In Series And Parallel

With the goal of"Emission Peak and Carbon Neutrality",soil-source heat pump has been applied more widely as an air conditioning technology with energy saving potential.In order to overcome the limitations of the soil-source heat pump system and to improve the performance degradation of the system after many years of operation,the trend is towards a combined cooling tower and soil-source heat pump system.It can solve the problem of unbalanced heat extraction to the soil caused by the perennial operation of the soil-source heat pump,but also has more obvious advantages in terms of energy efficiency,environmental benefits and economic benefits.Therefore,this paper takes a seven-story office building in Hefei,a Hot Summer and Cold Winter Zone,as an example,and uses modular dynamic system simulation software TRNSYS to build the building model of the office building,and proposes several different cooling tower control strategies under the condition of series and parallel connection and simulation analysis.Firstly,the mathematical model of each module of the composite system was established and elaborated using TRNSYS.The detailed data of the actual project was used for load calculation and characteristic analysis,and it was concluded that the soil heat absorption and discharge ratio is 1:0.48.Therefore,cooling towers need to be set up to assist in heat dissipation and ensure soil heat balance.According to the load characteristics of the building,a soil-source heat pump cooling tower composite system is established and two types of connection are used:series and parallel,with corresponding parameters and equipment selection for each type of connection.Three auxiliary cooling methods are proposed for the series connection of this composite system:fixed load ratio control,time control and maximum temperature control.Secondly,four auxiliary cooling control methods are proposed for parallel connection:fixed load ratio control,time control,temperature difference control and maximum temperature control.Finally,the COP,energy consumption,heat dissipation ratio,buried pipe outlet temperature and soil temperature are used as objective functions to compare and analyse the advantages and disadvantages of the above auxiliary cooling control methods under two connection methods,and to select the best control method under two connection methods.The results show that when the cooling tower is connected in series with the soil source heat pump system,the cooling method using fixed load ratio to control the cooling tower start and stop is better among the three cooling methods,with an annual average COP of 5.96 at a fixed load ratio of 0.65 and a ten-year soil temperature increase of only 0.3°C,but with higher energy consumption.When the cooling tower is connected in parallel with the soil source heat pump system,the auxiliary heat dissipation ratio of the cooling tower is most reasonable at a temperature difference of5°C,1.55:1.After ten years of operation,the soil temperature rises only 0.35°C,the energy consumption is 2.18×10~6 k Wh,and the COP is 6.55,indicating that this method can extend the life of the system and maintain high heat pump efficiency.