Design and application of a plate-tube evaporative cooling frost-free air-source heat pump

Based on the design of the conventional plate-tube evaporative cooling chilled water units, this study borrows the antifreeze principle of spraying antifreeze solution used in heat source tower heat pump systems and applies it to the plate-tube evaporative cooling chilled hot water units. Furthermore, design improvements are made to the plate-tube evaporative heat exchanger and the overall system to make it suitable for heating conditions in winter, ultimately resulting in the development of a plate-tube evaporative cooling frost-free air-source heat pump unit. During summer, the unit utilizes the plate-tube evaporative heat exchanger as a condenser, effectively lowering the condensing temperature and enhancing the system’s coefficient of performance compared to conventional air-source heat pumps. In winter, the use of spraying antifreeze solution ensures that the equipment operates without defrosting cycles, and the system provides stable heating, greatly improving the thermal comfort of the indoor side. Experimental investigations are conducted to evaluate the unit’s performance under various solution regeneration methods. The results show that the unit has the best performance when using the subcooled heat regeneration mode for solution regeneration, and the coefficient of performance only decreases by 2.5% to 5.1% without heat attenuation. The unit is suitable for hot summer and cold winter zone, as well as part of cold zone with lower latitudes.