Research On Performance Of Surface Water Solidification Heat Source Heat Pump System

In today’s society,energy shortage and environmental problems are still the two stumbling blocks to human development and progress.With the "double carbon" policy,people urgently need to find new renewable clean energy to replace the ore energy.Building energy consumption accounts for a large proportion of the total energy consumption in the world,and HVAC energy consumption is at the forefront of building energy consumption,so it is also of great significance to study the use of a new heat source for building heating.Heat pump as a kind of clean heating method,its research and application is more and more extensive,for surface water source heat pump,in winter in the north of the surface water temperature below 5℃,it is difficult to extract heat from the water,which has a certain limit on its application.Considering that there is also a certain amount of surface water in some areas of the north,if the latent heat in the water can be extracted to heat buildings,it will be a qualitative leap of surface water source heat pump.Comparing the research status at home and abroad,it can be found that in the study of the freezing heat pump,indirect freezing heat exchanger is used for the extraction of freezing heat,and the refrigerant flows outside the tube,and the tube freezes.After analyzing the advantages and disadvantages of the system,this paper decides to use the direct system,the evaporator directly extracts the solidification latent heat from the water,and the innovation of the icing way: refrigerant flow inside the tube,outside the tube icing.This paper first introduces the operation process of the heat pump system and the calculation of various performance parameters,and then analyzes the operation conditions of surface water solidification heat pump in different seasons by taking Lanzhou as an example.After that,curve fitting is done on the mechanism of the icing process and the numerical simulation results of icing,and the curve fitting function of the icing law is obtained.Secondly,theoretical analysis and simulation modeling are carried out for the four large parts of the surface water solidification heat source heat pump,and the simulation process of the system is planned and designed.Finally,by changing some operating conditions and structural conditions,the subsystem and system of the heat pump are numerically simulated,and some simulation results are obtained.Through the simulation of surface water solidification heat source heat pump system,the following conclusions are obtained:1)With the running of time,the heat production of surface water solidification heat source heat pump gradually increases and eventually becomes stable,while the COP of the system gradually decreases and eventually does not change.The two have an inverse relationship in the running process.2)In the operating conditions,the evaporation temperature of the condensate evaporator is-3℃～-5℃,the inlet temperature is 1℃～3℃,the inlet water flow rate is 0.1m/s～0.5m/s,and the outlet water temperature of the condenser is 45 ℃ ～55 ℃.The lower the evaporation temperature is,the higher the inlet water temperature is,the higher the inlet water flow rate is,and the lower the control of the outlet water temperature of the condenser is.The more beneficial it is to increase the heating capacity of the system.However,in the above working conditions,except the COP of the system which decreases the water temperature of the condenser outlet,the COP of the system which is conducive to the extraction of latent heat all decreases.3)In the range of tube diameter 8-12 mm and tube spacing 60-90 mm,the larger tube diameter and tube spacing of the condensate evaporator are,the more beneficial it is to increase the heating capacity of the system,but not conducive to improve the COP of the system.4)Among the three conventional refrigerants(R134a,R22 and R410A)studied,R134 a has the strongest compatibility with surface water solidification heat source heat pump system,and the highest heat production and system COP.Under the working conditions studied,the average COP of R134 a system during operation is 3.41,and the average heat production is273 k W.5)The optimal deicing time of surface water solidification heat source heat pump system should be selected as the moment when COP decreases to the lowest,and the deicing time is about 18 min in all the working conditions studied.Since the heat yield of the system during operation is negatively correlated with COP,the optimal operating conditions should be selected respectively according to the heat yield required by the heat source when studying the optimal operating conditions.