共查询到20条相似文献,搜索用时 478 毫秒
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本文对R134a、R290、R600a及R600等四种制冷剂用于双回路耦合制冷系统的性能进行模拟计算。其中R600的当量性能系数最高、单位质量制冷量最大而容积制冷量最小;R600a排气温度最低;R290循环压比最小。对由R290、R600及R600a组成的不同混合制冷剂进行模拟计算,当小端温差一定时,混合制冷剂当量性能系数高于纯质;当有效换热温差一定时,混合制冷剂R290/R600a当量性能系数与纯质R600相当,循环压比稍高于R290,最高排气温度低于所选纯质制冷剂. 相似文献
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大气臭氧层的破坏和温室效应的加剧,是当前世界面临的主要环境问题。文中通过对R600a制冷剂物理化学特性的介绍以及与R12制冷剂的对比,得出在冰箱领域,R600a是一种可以永久替代CFCs的环保型制冷剂,分析了R600a替代R12的制冷系统设计的一些要点,最后基于提高工作效率以及保障操作安全的考虑,阐述了R600a冰箱的维修工艺。 相似文献
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随着京都议定书和蒙特利尔议定书的执行,寻找HCFCs制冷剂的替代制冷剂成了当务之急。环保制冷剂HFO-1234yf的ODP为0,GWP为4,已经在欧洲国家应用于汽车空调中替代R134a。文中对HFO-1234yf替代R22进行理论循环分析对比。通过理论分析,结果发现:标准工况下HFO-1234yf单位制冷量比R22低37.6%,单位容积制冷量低47.6%,同时排气温度比R22低23.78℃,在高温环境中有利于压缩机的运行,适用于高温工况。高温工况下HFO-1234yf单位制冷量比R22低31.9%,排气温度低21.71℃,使用HFO-1234yf替代R22需要增加制冷剂充注量,并加大压缩机工作容积。同时对润滑油分析表明,HFO-1234yf可以使用PAG、POE及PVE润滑油,与矿物油的互溶性还需要进一步研究。 相似文献
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采用状态方程和多项式函数拟合两种方法,利用现有的物性计算,提出一些常用制冷剂的热力性质计算公式。利用FORTRAN和VB6.0建立了包含R12、R22、R134a的热物性计算软件。程序开发中采用层次模块的思想和开放式结构,便于增加新的制冷剂,具有良好的可扩充性。 相似文献
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基于制冷剂物性计算软件NIST REFPROP 7.0及R125/R600a气液相平衡实验数据,使用MBWR状态方程结合Lemmon-Jacobsen混合物模型,对R125/R600a(50/50 mass%)混合替代工质的热力学性质进行了计算,并制作给出了其压焓图(p-h)、温熵图(T-s)和比定压热容图(c<,p>-T)及饱和性质表.最后理论计算分析了其空调制冷工况的性能,结果表明该混合工质具有与R22相当的压缩比和COP值,比R22较低的排气温度和较高的单位质量制冷量. 相似文献
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B. I. Reznikov N. I. Alekseev S. V. Bobashev B. G. Zhukov S. A. Ponyaev R. O. Kurakin S. I. Rozov 《Technical Physics》2011,56(8):1106-1111
The equilibrium composition and the effective adiabatic exponent of a low-temperature carbon plasma containing eight components
(C, C2, C3, C4, C5, C+, C2+, and e) are calculated. The temperature and pressure ranges are found in which polyatomic clusters form in a gas flow. It is shown
that the effective adiabatic exponent of the carbon plasma is a nonmonotonic function of temperature. In the parameter range
where the plasma consists largely of polyatomic clusters, the adiabatic exponent is close to unity. It is noted that anomalously
low values of the effective adiabatic exponent indicate a considerable concentration of polyatomic molecules in the plasma
jet. Such values can be observed in experiments with a low-temperature carbon plasma flowing about bodies. 相似文献
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We conduct an experimental study of the dependence of single bubble sonoluminescence intensity on the concentration of various alcohols. The light intensity is reduced by one-half at a molar fraction of ethanol of approximately 2.5x10(-5); butanol achieves the same reduction at a concentration 10 times smaller. We account for the results by a theoretical model in which the alcohols are assumed to be mechanically forced into the bubble at collapse, modifying the adiabatic exponent of the gas. The increasing hydrophobicities of the alcohols lead to decreasing effective adiabatic exponents, and thus to less heating and therefore less light. Support for this model is obtained by replotting the experimental light intensity values vs the calculated exponents, yielding a collapse of all data onto a universal curve. 相似文献
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流体界面不稳定性数值模拟中不同介质界面的处理方法 总被引:2,自引:0,他引:2
在界面不稳定性数值模拟中,以往的方法^〔1,4-8〕局限于密度不同的单种介质或绝热指数相同的两种介质问题,在计算绝热指数不同介质间的扰动时,界面上强制加入接触间断边界条件,从而避免了界面上数的非物理振荡,用三维程序TVD/AC对两种不同介质,在单波扰动下Rayleigh-Taylor不稳定性的发展进行了计算,得到了扰动随时间发展的图像。 相似文献
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利用能够体现电子壳层结构效应的三项式状态方程,结合Hugoniot关系式,对Al和Ag的冲击压强和冲击温度进行计算,将结果与实验数据和其他代码计算的结果进行比对。然后对Be、Al、Fe、Ag、Au和Pb金属材料沿Hugoniot曲线上的压强、温度、平均电离度、Fermi简并因子和有效绝热指数进行系统地研究,并给出细致的物理分析。最后总结这些特征物理量随质量密度压缩比变化的一般趋势。 相似文献
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A. N. Kucherov 《Technical Physics》2012,57(11):1479-1486
Changes in the formulation of the problem for a vortex source and a vortex sink upon taking into account the change in the heat capacity and the adiabatic exponent for a diatomic gas (for the example of air) in response to an increase in the temperature from 300 K to a few thousands of Kelvin are discussed. A thermal choking is studied for a vortex sink, and critical values of the energy parameter are calculated. It is shown that the minimal radius of the vortex sink decreases upon a heat release. Similarity parameters including the dimensionless circulation (or mass flow), the energy parameter, and the position and thickness of the heat-release region are varied. Errors of the gas model that assumes constant heat capacities and a constant adiabatic exponent are estimated. 相似文献
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针对爆炸粉末烧结过程中颗粒间的摩擦效应提出了一种无夹角斜碰撞模型,分析了烧结过程中颗粒间摩擦力随温度的变化规律,借助于LS-DYNA有限元程序研究了冲击压力、颗粒大小、材料强度等因素对孔隙闭合时间的影响,给出了颗粒界面温升的表达式。研究结果表明,由摩擦引起的颗粒界面的温升与材料特性、颗粒度、冲击角度、冲击压力等因素有关,随材料的蓄热能力、传热能力和材料强度的增加而减小,并随着材料疏松程度、颗粒直径、冲击压力的增加而增加;在粉末颗粒直径和冲击压力不是太小的情况下,颗粒表面温度将达到材料的熔点。 相似文献
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The composition and the effective adiabatic exponent of the plasma of the breakdown channel for the elements making up rocks and minerals are calculated under conditions of technological electroexplosion. It is shown that the effective adiabatic exponent can be increased by introducing into the breakdown channel metals of the first group via electric explosion of a conductor.High-Voltage Institute, Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 106–109, July, 1994. 相似文献
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By a pulsed ultrasonic method we determine the adiabatic elastic moduli of nitrates of alkali metals. We calculate the characteristics of the strength of the interatomic coupling, the Debye temperature, and the lattice energy of the compounds being investigated. 相似文献