【作者】 黄东； 袁秀玲； 陈蕴光；

【Author】 Huang Dong, Yuan Xiuling,Chen Yunguang (School of Energy and Power Engineering, Xi’an Jiaotong University 710049,China)

【机构】 西安交通大学能源与动力工程学院；

【摘要】 把热气旁通除霜与逆循环除霜的性能进行了比较。在名义制热冷量为55kw的风冷热泵冷热水机组上进行了实验研究,结果表明:(1)热气旁通除霜的除霜时间为272s,比逆循环除霜时间长178s,其中融霜时间长160s,较长的融霜时间主要因为较低的吸气压力导致较小的制冷剂流量以及由分液器的压降与吸热造成的热量损失造成的;(2)热气旁通除霜的融霜阶段,排气过热度和排气温度不断降低,因此客观上存在对霜层厚度的限制,防止排气过热度太小而使压缩机不能正常工作,而逆循环除霜的排气温度非常稳定;(3)热气旁通除霜对融霜后被冷凝的制冷剂液体在压缩机的抽吸作用下汽化,压缩机不存在液击的危险,但吸气过热度一直维持在0℃左右,而逆循环除霜融霜后的制冷剂液体在水冷换热器中吸热后蒸发至过热状态,吸气过热度一直大于15℃。更多还原

【Abstract】 The comparison of dynamic characteristics between the hot - gas bypass defrosting method and reverse - cycle defrosting method was made experimentally on a 55 kW unitary air - to - water heat pump. The experimental results showed notable differences in three aspects. First, the defrosting time for the hot- gas bypass defrosting method was 272 seconds, 178 seconds longer than that for the reverse - cycle defrosting method. The melting time for the hot - gas bypass defrosting method was 160 seconds longer because the refrigerant flow rate was smaller owing to the lower suction pressure and the heat loss was larger caused by the distributor and distributor capillary. Secondly, there was a limit to the mass of frost for the hot - gas bypass defrosting method in order to limit the melting time because both the discharge temperature and the discharge superheat decreased remarkably during the melting time of the defrost periods. The limit of melting time for the hot - gas bypass defrosting method prevented the discharge superheat from decreasing to a level where the compressor didn’t function normally. But, the there was not a limit to the mass of frost for the reverse - cycle defrosting method because the discharge temperature was stable all the defrosting period. Finally, though no heat for the hot - gas bypass defrosting method was added to the liquid refrigerant condensed by the melting of frost, the level of the liquid refrigerant in the suction - line accumulator gradually dropped all the defrosting period because the compressor pulled the suction pressure down enough to flash the liquid refrigerant in it into saturated gas. The compressor was not in clanger of flooding, but the compressor suction superheat was always 0℃ all the melting time for the hot -gas bypass defrosting method. However, the compressor suction superheat for the reverse - cycle defrosting method was always above 15℃ throughout the same period because the liquid refrigerant absorbed heat in the water - side heat exchanger and was vaporized into superheated gas.更多还原