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Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity. Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further. a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40℃ to 50℃ C. the mass flow rate for R22 is increased by 16%. while the increasing rate for R290 is 13%. 相似文献
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Acapillarytubeiscommonlyusedastheexpan sionandflow rate controllingdeviceinsmallrefrige ratingandair conditioningsystems.Recently,itsap plicationhasbeenextendedtolargerunitssuchasunitaryairconditionersofsizeupto35.2kWcapaci ty[1].Itssimplicity,havingnoactiveparts,lowcostandlowstartingtorqueofcompressorsarethemain reasonsforitswideuse.Despiteitssimpleconfigura tion,theflowinsideacapillarytubeisverycomplexanditsbehaviorsignificantlyinfluencestheperform anceofthewholesystem.Inthepastdecades,many… 相似文献
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在新的教育改革形势下,对初中数学教学工作有了新的要求,初中数学教学是落实素质教育的重要课程,改革课堂教学模式、更新教学理念势在必行.新的理念下,课堂教学要求建立新型的师生关系,体现教师的主导性和学生的主体性.本文将重点阐述反思教学法在初中生数学教学中的运用.一、反思教学法在初中数学教学中的作用不容忽视反思教学法是一种探索中的教学模式,是一种新型的教学理念.反思教学法就是要针对初中学生的年龄特点,重视学生 相似文献
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