毛细管长度对热泵热水器系统动态性能的影响

Effects of the Capillary Length on the Dynamic Performance of an Air Source Heat Pump Water Heater

对使用4种不同长度毛细管的空气源热泵热水器系统的动态性能进行了试验研究,分析了毛细管长度对压缩机排气温度、系统耗功率、蒸发压力、冷凝压力、制热量及系统性能系数(COP)等的影响。试验结果表明,在加热初始阶段,采用短毛细管的热泵热水器系统性能优于使用长毛细管的系统性能,而在加热后期则恰好相反。为了提高加热周期内热泵系统的平均性能系数,在加热过程中分别切换使用长度为150mm、250mm和350mm的3种毛细管,其动态性能试验表明,可大大提高热泵热水器系统的性能,其平均COP约为4.6。在整个加热阶段,压缩机的排气温度未超过90℃,保证了压缩机在一个安全稳定的条件下运行。

The dynamic performance of an air source heat pump water heater （ASHPWH） with different length of capillary tube was investigated experimentally. The effects of the capillary tube length on the discharge temperature of the compressor, input power, condensing and evaporating pressures, heating capacity and coefficient of performance （COP） were analyzed. The experimental results indicate that in the initial heating stage, the COP of the system with shorter capillary tube is larger than that with the longer one, in the late stage, the performance of the ASHPWH system with longer capillary tube is better. The heating capacity curves present a similar trend with the COP. In order to improve the average COP of the heat pump system on the heating period, the capillary tubes about 150 mm, 250 mm, and 350 mm long was changed orderly during heating process, and the dynamic performance of the ASHPWH system was measured. It is found that the average performance of the ASHPWH system is improved significantly by changing the length of the capillary tube, and the average COP is about 4.6. The refrigerant temperature from the compressor is less than 90 ℃ in the all experiments.