Study On Heat Transfer Of Associated Equipment Of Seawater Source Heat Pump System

Seawater source heat pumps are used for building heating and cooling, which is helpful to solve energy shortage problems. Efficiency of seawater source heat pump systems is different in direct and indirect application modes. Heat transfer performance of associated equipment of seawater source heat pump is studied in this thesis.Titanium heat exchangers were added between seawater and evaporator in indirect seawater source heat pumps to avoid corrosion. Because of the high price of titanium heat exchangers, antiseptic steel heat exchanger was designed and heat transfer performance was studied in order to decrease system investment. Experiment table was set up and the impact of inner and outer fluid velocity on heat transfer performance of heat exchangers was analyzed, convective heat transfer correlations of inner and outer tube were obtained. Mathematical model of heat transfer in heat exchanger was established based on the experiment results, outlet temperature of glycol solution and heat output with the change of seawater temperature were calculated.COP of heat pump are directly affected by supply water temperature, especially when the seawater temperature is low. Thermal performance of new type radiant floor was tested based on the standard radiator experiment table, the results indicated that the supply water temperature of 30℃could satisfied the comfort requirements, which is 15℃lower than that of normal floor heating. The decreasing of supply temperature lowered the condensing temperature, thus improving COP of heat pump system. When the evaporating temperature is -5℃and supply temperature dropped from 45℃to 30℃, COP of the heat pump system would increase from 3.52 to 4.76.In order to improve the evaporating temperature and system efficiency, experimental study and theoretical analysis on thermal performance of antiseptic evaporator of direct seawater source heat pump systems were done. According to the contrastive study of heat transfer in antiseptic and normal evaporator, it can be concluded that the thermal conductivity of the antiseptic dope is 3.23 W/(m? K).When seawater velocity is less than 1.5m/s, surface roughness enhanced heat transfer, heat transfer coefficient of the antiseptic evaporator is more than that of the non spray-painted evaporator; When sea water velocity is bigger than 1.64m/s, turbulent flows occurred, heat transfer coefficient of the antiseptic evaporator is less than that of the non spray-painted evaporator. Spray-painting antiseptic dope could solved seawater corrosion and have little influence on thermal performance of evaporator.Energy consumption model of direct and indirect seawater source heat pump system was set up, COP and energy consumption of direct and indirect system was simulated. Combined with one practical project, economical efficiency of the two modes of seawater source heat pump systems was compared, the results show that COP of direct system is 4.31 with the seawater temperature of 5.1℃, which is 1.02 higher than that of indirect system, 6,496 kWh and 5,132 RMB would be saved during a heating period.