含氨共沸混合物制冷性能模拟

The Calculation of the Refrigeration Performance Based on Azeotropic Mixtures Containing Ammonia

氨是性能优良的天然制冷剂,其臭氧消耗潜能值和全球变暖潜能值均为零,但存在毒性和可燃性的潜在危害,除此之外,氨还存在溶油性差的问题。在氨中添加烷烃、氢氟烃等形成混合物,尤其是共沸混合物,有望解决氨的这些问题,形成容积制冷量更高的环保制冷剂,并减少氨的充注量。基于此,本文基于共沸压力极值特征,建立三元共沸预测模型,并预测到3种含氨三元共沸物,对这些制冷剂以及部分商用制冷剂进行制冷性能模拟,发现含氨混合物在容积制冷量、制冷效率以及排气温度方面均具有明显优势。

Ammonia is a natural refrigerant with excellent thermodynamic properties,zero ozone depleting potential（ODP） and very low global warming potential（GWP）.However,the poisonousness and flammability of ammonia limited its civil application.Besides,ammonia is immiscible with mineral lubricants,which may lead to a weakened heat transfer coefficient due to the film of oil presented in the evaporator.One of the most promising ways to extend ammonia＇s application in refrigeration systems is searching for new refrigerant mixtures based on ammonia.The improved properties of working agent were offered in the way to mix pure ammonia with other refrigerants having low values of GWP and zero ODP.In this paper,an evaluation of mixed refrigerants based on ammonia in the vapour compression refrigeration system was performed,synthetically considering the coefficient of performance（COP）,volumetric refrigeration capacity（VRC） and discharge temperature.Both binary and ternary azeotropic mixtures were investigated,along with some commercial zeotropic refrigerants as references.The mixed thermodynamic properties were calculated by Peng-Robinson equation of state with the regressed interaction parameters.The COP of the mixtures was generally lower than that of the individual refrigerants,except for some azeotropic systems comprising of ammonia and hydrofluorocarbons.The discharge temperatures of all the azeotropic refrigerants were attractile,especially for ammonia＇s mixtures.The present results suggest the superiorities of the azeotropic refrigerants,especially for binary and ternary systems including ammonia.