Research on frost-resistant characteristics of air-water source finned evaporator based on air dew point temperature

Abstract

To enhance the heating performance and building load matching capability of finned evaporator heat pumps in winter, this study proposes a frost-suppression method using an air–water source finned evaporator integrated with a hot-water coil. A computational model for this combined heat transfer unit was established. Based on the air dew point temperature, an Artificial Neural Network prediction model with a coefficient of determination R2 of 0.9998 was developed, using inlet air temperature, humidity ratio, air velocity, and hot-water temperature as input variables and refrigerant heat gain as the output. This model was employed to simulate the maximum heat supply capacity and conduct load matching analysis under frost-free evaporator operation. Results indicate that a lower air humidity ratio corresponds to greater frost-free heating potential. For instance, at 5℃ air temperature, the maximum heat supplies for humidity ratios of 0.5 g/kg and 3.5 g/kg are 2.88 W and 0.38 W, respectively. Increasing the evaporator hot-water temperature significantly boosts the heat supply under frost-free operation: at −10℃ air temperature and 0.5 g/kg humidity ratio, the maximum heating capacities with 20℃ hot water and without hot water are 12.86 W and 5.54 W, respectively. Under typical winter conditions, raising the hot-water temperature effectively enhances exerts a more substantial influence on the matching rate between heat supply and building demand than varying the air velocity: in Xiangtan, increasing the temperature from 10℃ to 20℃ improves the matching rate of 11.87% (with 20℃ hot water meeting demand for 12.85% of the heating period), while in Xi’an, the corresponding improvement is 31.66% (with 20℃ hot water satisfying 50.87% of the demand). This research provides an effective methodology for frost suppression and load matching regulation in air-source heat pumps.