准二级压缩多联机严寒地区供暖性能研究
Heating performance analysis of quasi-two-stage compression variable refrigerant flow system in severe cold zone
摘要：
为了推动多联机在严寒地区的应用,在哈尔滨搭建了一个准二级压缩多联机实验台,采用根据室外温度分段控制压缩机吸气状态的控制策略,进行了91天的测试。结果表明:采用提出的控制策略,实验机组在整个测试期间均可以稳定运行,最高排气温度为90.6 ℃,季节性能系数为2.40,且室内温度能够满足供暖需要;导致机组在严寒地区制热量不足的主要因素是误除霜,而不是室外低温,误除霜引起的最大逐时制热量不足率为24.31%,而室外低温环境只有7.74%;在室外温度为-22.5～7.5 ℃时实验机组的供暖效果较好,室外温度低于-22.5 ℃时存在制热量不足;因严寒地区的机组选型较大且受压缩机最低频率限制,故在室外温度高于7.5 ℃时,机组存在频繁启停现象。
Abstract：
To promote the application of variable refrigerant flow system (VRF) in the severe cold zone, a quasi-two-stage compression VRF test rig is built in Harbin, a segmented control strategy for the suction refrigerant state of the compressor based on outdoor temperature is adopted, and a 91-day test is conducted. The results show that by adopting the proposed control strategy, the experimental unit can operate stably during the whole test period, the highest discharge temperature is 90.6 ℃, the seasonal coefficient of performance reaches 2.40, and the indoor temperature can meet the heating demand. The main reason leading to the heating capacity shortage of the unit in the severe cold zone is mal-defrost, but not ultra-low outdoor temperature. The maximum hourly heating capacity shortage rate caused by the mal-defrost is 24.31%, while it is 7.74% caused by the ultra-low outdoor temperature. The heating effect of the experimental unit is better at the outdoor temperature of -22.5 to 7.5 ℃, and there is insufficient heating when the outdoor temperature is below -22.5 ℃. Due to the large selection of the unit in the severe cold zone and the limit of the lowest frequency of the compressor, the unit is frequently started and stopped when the outdoor temperature is higher than 7.5 ℃.
Keywords:variable refrigerant flow system; quasi-two-stage compression; heating performance; low-temperature heating; severe cold zone; vapor injection; mal-defrost