Pilot Study On Vapor Compression Heat Pump With Direct-Contact Heat Exchanger

Direct-contact heat transfer is a kind of heat transfer method of high efficiency. Compared to the traditional indirect heat transfer, it has low thermal resistance and no scaling and corrosion. If the direct contact heat transfer technology is to be used in heat pump system, heat exchange efficiency of condenser and evaporator will be increased greatly and heat transfer temperature difference will be decreased. So the COP of heat pump is increased. In this work, the vapor compression heat pump system with direct-contact heat exchanger was studied on a pilot system.First of all, in order to make clear the influence of heat transfer temperature difference on the COP of heat pump, the theoretical COP was calculated by thermodynamics method. The calculation results show that the COP increases rapidly as the difference between the condensing temperature and evaporating temperature decreases. That is, the smaller temperature difference, the larger promotion to the COP by the decrease of temperature difference.Then, the heat pump experimental system with direct-contact heat exchanger was established. R600a and water were used as refrigerant and coolant. Stable operation was achieved after commissioning.At last, the influencing factors of the volume heat transfer coefficient and the COP were studied by experiment. The results show that the volume heat transfer coefficient has approximately a negative exponential relationship with logarithmic mean temperature difference and a positive linear relationship with gas flow rate. The COP increases with the increase of the volume heat transfer coefficient and gas flow rate.