变频双级压缩空气源热泵系统中间喷射状态对性能的影响研究

Study on Impact of Intermediate Injection Conditions on Performance of Two-stage Compression Air Source Heat Pumps with Frequency Conversion

双级压缩空气源热泵是应用在低温室外环境下供暖的一种高效节能的热源,在我国寒冷地区逐渐获得推广使用,其可靠性和高效性主要依赖于中间压力等相关参数。采用带有中间换热器的双级压缩空气源系统作为研究对象,首先建立并验证了相关数学模型,然后分别研究了中间压力、中间换热器换热面积及其过热度与系统性能之间的关联规律。模拟结果显示中间过热度在一定范围内对系统COP几乎没有影响,在达到一定数值之后COP才明显下降;随着中间换热器面积的增加,系统COP先随之增长而后趋于平稳;最优COP对应的中间压力处于一个区间,在冷凝温度一定时蒸发温度越低中间压力对COP影响越显著;对于相同的蒸发压力,较高的冷凝温度相比于较低的冷凝温度条件下最优COP对应的中间压力范围要宽一些。在引进压缩机变频对其效率的修正之后,发现压缩机的变频调节对关联于系统最优COP的中间压力平缓区产生一定影响,且使COP的模拟值更接近于实测数据。

An air source heat pump （ASHP） with two-stage compression was a kind of high-efficiency heat source which was used in building heating systems in the cold climate, and its reliability and efficiency mainly depended on its intermediate pressure. In this paper, a two-stage compression ASHP system with an intermediate heat exchanger was adopted as a research object to establish and verify the relevant mathematical models. Relevanees among the intermediate pressure, the area of the intermediate heat exchanger, the superheat of exchanger and COP were discussed separately in this paper. Simulation results showed that the superheat of exchanger had no effect on COP within a certain scope then decreased until reaching a certain value. With the increasing of intermediate heat exchanger area, the COP first grew then leveled off. Intermediate pressure corresponding to the optimum COP was in an identical interval, and the intermediate pressure affects COP more significantly with evaporation temperature lower provided that the condensation temperature was certain. In addition, for the same evaporation pressure, the intermediate pressure range corresponding to the optimal COP was wider at higher condensation temperatures. Finally, the optimum COP corresponding the intermediate pressure range was influenced by introducing the value of the compressor frequency correction while the simulation value of COP could be closer to the measured data.