间接制冷换热器除霜方案研究

Defrost of Heat Exchangers Using Secondary Refrigerant

目的对以载冷剂为冷媒,用于极端低温气候环境实验室的换热器的除霜问题进行研究,获得可行的除霜设计方案。方法从抑霜和融霜两个方面出发,设计包含变片距结霜换热器的内融霜和外融霜两种除霜方案,并搭建实验台对除霜方案进行实验研究。结果变片距结霜换热器迎风面结霜严重,背风面轻度结霜,内融霜可在3.5 min完成,而外融霜需要2倍的时间。内融霜结束后继续加热换热器,并配合新风置换可在20 min内除去化霜后的附着水。结论变片距结霜换热器能够有效对来流空气进行预除湿,抑制主换热器结霜,内融霜效果最好且目前以蒸汽为热源、内融霜为主、新风吹扫为辅的除霜系统已应用于大型气候环境实验室。

Objective To solve the frost problem of heat exchangers used in extreme low temperature climatic test chamber with liquid secondary refrigerant as coolant to obtain feasible design scheme for defrost.Methods Based on the aspects of restrain-frost and defrost,two defrost systems including variable fin spacing frost-heat exchanger were designed and studied by experiment.Results The windward side of the variable fin spacing frost-heat exchanger frosted heavily while the leeward frosted lightly.Defrost time consumed by inner-defrost system was 3.5min while out-defrost system needs 7min.In combination with replacement of refresh air,water retained on the surface of frost-heat exchanger could be removed in 20min by flowing heat after inner-frost.Conclusion The variable fin spacing frost-heat exchanger can pre-dehumidify the air and protect the main heat exchanger.The inner-defrost system with good inner defrosting effect supported by fresh air purging and with steam as the heat source is successfully applied in large climatic environmental test laboratory.