风机提前启动对风冷热泵冷热水机组除霜的影响

研究了风机提前启动对逆循环除霜时间的影响.在一台名义制热量为55kW的风冷热泵冷热水机组上,采用风机提前启动和正常启动对该机组的除霜影响进行了对比实验.结果表明:当排水阶段结束时,风机提前启动除霜实验的排气压力为1234.6kPa,比风机正常启动除霜实验的排气压力低772.3kPa;在恢复阶段,由于制冷剂的流量较大而板式换热器的内容积较小,使2个除霜实验的排气压力在短时间内剧烈上升,上升幅度分别为574kPa和488.7kPa;在恢复阶段,风机提前启动除霜实验的排气压力峰值为1808.6kPa,比风机正常启动除霜实验的峰值2495.6kPa降低687kPa,有效避免了因风机正常启动除霜实验的排气压力接近高压保护值(2550kPa)而导致停机的可能.

Effect of Air Cooled Coil Fan Pre-Start on the Refrigeration System Dynamics During the Reverse-Cycle Defrost of an Air-Source Heat Pump Chiller

The influence of the air cooled coil fan pre-start on the refrigeration dynamics of an air-source heat pump chiller during the reverse-cycle defrost was investigated. The experiments for the fan pre-start test and fan norma-start test were conducted on a 50 kW unitary air-to-water heat pump and discussed. The discharge pressure for the fan pre-start test was 1 234.6 kPa at the end of the draining period, 772.3 kPa lower than that for the fan normal-start test. And the discharge pressure had the sudden increase of 488.7kPa for fan normal-start test and 574kPa for fan pre-start test during the defrost termination and recovery period due to the small inner volume of the plate heat exchanger and larger refrigerant flow rate. The peak of discharge pressure for the fan pre-start test was 1 808.6 kPa at the defrost termination and recovery time, which was 687 kPa lower than that of 2 495.6 kPa for the fan normal-start test. So by using pre-start the unit can avoid turning off when the peak of the discharge pressure for the fan normal-start test approaches the discharge protection value (2 550 kPa).