乙醇对换热器结霜特性影响的试验研究

Experimental study on effect of ethanol on frosting characteristics of heat exchanger

分析凝缩性物质的抑霜机制,搭建乙醇喷射换热性能可视化试验系统,观测乙醇喷射比(乙醇与空气中水蒸气质量比)和换热器管壁温度对换热器结霜特性的影响,分析传热系数、管外侧压损、霜层厚度等随乙醇喷射比的变化,得到不同条件下乙醇对结霜过程的影响规律。结果表明,当载冷剂进口温度为77 K,乙醇喷射比为0.6时,换热器传热系数是未喷射乙醇时的2倍,在30 s时霜层厚度仅为未喷射乙醇时的1/10;当载冷剂进口温度为240 K,乙醇喷射比分别为0.1和0.2时,换热器传热系数与未喷射乙醇相比分别提升30%和60%;当载冷剂进口温度为77 K,乙醇喷射比分别为0.4和0.6时,换热器传热系数与未喷射乙醇相比分别提升10%和20%。

The anti-frosting mechanism of condensing substances is analyzed,for which a visible experimental system is set up to observe the effects of ethanol injection ratio(mass ratio of ethanol to water vapor in the air)and tube wall temperature of heat exchanger on the frosting characteristics of heat exchangers,and analyze the changes of heat transfer coefficient,pressure loss outside the tube and frost layer thickness with ethanol injection ratio.Thus,the effect law of ethanol on the frosting process under different conditions are obtained.The results show that when the secondary refrigerant inlet temperature is 77 K and the ethanol injection ratio is 0.6,the heat transfer coefficient of the heat exchanger is twice that of the case without ethanol injection,and the thickness of the frost layer is only 1/10 of that of the case without ethanol injection at 30 s;when the inlet temperature of the secondary refrigerant is 240 K and the ethanol injection ratios are 0.1 and 0.2 respectively,the heat transfer coefficients of the heat exchanger are increased by 30%and 60%respectively compared with the case without ethanol injection;when the inlet temperature of the secondary refrigerant is 77 K and the ethanol injection ratios are 0.4 and 0.6 respectively,the heat transfer coefficients of the heat exchanger are increased by 10%and 20%respectively compared with the case without ethanol injection.