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对自然复叠制冷系统制冷剂选择、循环流程设计以及热力计算进行了研究,建立了R23/R134a自然复叠制冷系统实验装置.自然复叠非共沸制冷剂的沸点间距按大致等分的原则选择,一般沸点间距40~80℃.研究指出完成自然复叠制冷循环热力计算需要已知以下4个重要参数:冷凝温度、蒸发温度,以及冷凝压力、蒸发压力、浓度3个参数中的2个参数.制冷循环流程设计时,增加分凝器,可以提高低温回路制冷剂浓度;在低温回路节流阀加延时开关,可以缩短自然复叠制冷装置启动时间.R23/R134自然复叠制冷系统实验装置,最低蒸发温度达到-55~C左右,合适的R23/R134a充注浓度约在29.4%~41%之间.研究结果对自然复叠制冷系统的产品设计过程有参考价值. 相似文献
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中高温热泵系统中在工业领域有广泛的应用,但其排气温度偏高。本文从降低压缩机排气温度角度,设计一种双级压缩新型热泵系统。系统由高低级压缩机、分凝器、两个节流机构等组成。以循环性能较好的两种工质R134a和R152a为系统循环工质,理论分析结果表明:在中高温工况下,新系统工质R152a循环性能系数COP优于R134a,在相同工况下工质R152a循环性能COP比R134a高7%8%;高温级压缩机排气温度均随中间压比的升高而降低;排气温度与传统单级压缩系统相比有38%;高温级压缩机排气温度均随中间压比的升高而降低;排气温度与传统单级压缩系统相比有312℃的降幅。 相似文献
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对使用R134a/R23混合制冷剂的三种常用自然复叠制冷系统进行了设计,比较分析了这三种系统的蒸发温度、COP、压缩机排气温度等运行参数特性,并研究了在制冷剂配比改变、蒸发温度改变时三种系统的变化特性.对这三种系统特性的掌握将有利于自然复叠系统的选型设计. 相似文献
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为了研究压缩机频率对复叠式热泵系统的影响,结合复叠式循环技术与压缩机变频技术,搭建变高温压缩机频率复叠热泵实验台。研究分析了压缩机排气温度、压缩机功率、系统制热量及系统COP(以下COP均指系统COP)随高温压缩机频率的变化,试验结果表明:当蒸发温度-30 ℃,冷凝温度46 ℃工况下,随高温压缩机频率增加,高温压缩机排气温度上升,上升速度逐渐加快,最高排气温度99.7 ℃,小于120 ℃,低温压缩机排气温度下降,下降速度逐渐缓慢;高温压缩机功率逐渐增大,低温压缩机功率逐渐减小,系统功率呈增加趋势;系统制热量呈线性增加趋势,COP随高温压缩机频率增加呈先增加后减小趋势,最大COP为2.7。 相似文献
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Venkataramana Murthy V. Padmanabhan Senthil Kumar Palanisamy 《Journal of Mechanical Science and Technology》2013,27(3):917-926
This work presents an experimental comparison of exergy efficiency (EE), irreversibility at the process 1–2 (evaporator exit to compressor inlet), 2–3 (compressor inlet to condenser inlet), 3–4 (condenser inlet to expansion valve inlet), 4–5 (expansion valve inlet to evaporator inlet) and 5–1 (evaporator), and coefficient of performance (COP) of R22, and its substitutes R134a, R290 and R407C in vapor compression refrigeration system (VCRS) of an air conditioner. In addition, the effects of air temperature in the freezer with reference to environment states on irreversibility and EE have been investigated. At ?18°C air temperature in the freezer, 33°C reference environment state and 42% relative humidity refrigerants R22 and its substitutes R134a, R290 and R407C VCRSs the total irreversibilities are 665.7, 753.5, 582.1 and 677 W, and EEs are 22.9, 14.2, 26.5 and 20.6%, respectively. The refrigerant R290 is the best performer among candidate refrigerants but it suffers from flammability. Thus, R407C can considerably be used to replace R22. 相似文献
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In this study, therma l performance of two hydrocarbon refrigerants of R290 and R1270 was measured in an attempt to substitute
R22. They wer tested in a heat pump bench tester of 1 ton capacity with a hermetic rotary compressor. Water and water/glycol
mixture were employed as the secondary heat transfer fluids in the test bench. All tests were conducted under the same external
conditions simulating three different air-conditioning and heat pumping conditions. Test results show that the coefficient
of performance of these hydrocarbon refrigerants is up to 11.5% higher than that of R22 under all conditions. Refrigeration
capacity of R290 is up to 8.2% lower than that of R22 under normal air-conditioning and heat pumping conditions. Under extremely
cold temperature conditions, however, the capacity of R290 is 5% higher than that of R22. On the other hand, the capacity
of R1270 is similar to that of R22 under all conditions. Compressor discharge temperatures of these hydrocarbons are reduced
by 14–31°C as compared to R22. The amount of charge is reduced up to 58% as compared to R22. Overall, these hydrocarbons provide
good performance with reasonable energy savings without any environmental problems and thus can be used as long-term alternatives
for residential air-conditioning and heat pumping applications. 相似文献
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依据GB/T7725—2004规定的试验工况,分别对应用R32和R290的空调系统进行性能测试。在理论分析的基础上,依据试验数据,对比分析两种替代制冷剂的优缺点及其系统的改进方法。结果表明:R32单位容积制冷量高出R290约87%左右,相同制冷量下R290系统应使用更大排量的压缩机。R32具有较高的排气温度,并且R32系统相比R290系统,压比高出约7%,系统整体的能效比低约3.7%。R290系统换热器的压降要小于R32,有助于提高系统性能。但其可燃性远远大于R32,在安全设计方面有着更高的花费,系统初期改造投入比较高。 相似文献
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基于新形势下气象信息网络平台发展的需要,从2009年9月下旬到10月初,我市完成了Domino从R5到R8的升级工作。本文就升级过程中出现的几个常见问题及处理进行浅析,为各地市局DominoR5到R8的升级过程提供参考与借鉴。 相似文献
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Analysis on the ink transfer mechanism in R2R application 总被引:2,自引:0,他引:2
Ink transfer process from the printing roll to the web was investigated using a Computational Fluid Dynamics (CFD) technique
for the roll-to-roll (R2R) printing application. A parametric study was conducted to identify the effects of fluid parameters
such as viscosity, surface tension and contact angle. To make the present analysis more relevant to the real printing system,
a three-dimensional computational configuration for the commercial software was set up using the information obtained from
the typical R2R system. Simplified one-dimensional semi-analytic model based on Reynolds equation was compared with the CFD
results to assess the validity of the results. Pressure distribution states that 1-D analysis is reasonably good in capturing
the flow physics. The 3-D simulation with VOF (Volume of Fluid) shows that viscosity is the most important parameter. Moreover,
the larger surface tension resulted in smaller amount of ink transfer. 相似文献
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关于R407C用于替代R22的研究 总被引:4,自引:2,他引:4
在利用环保制冷剂R407C替代HCFC制冷剂R22的过程中有许多值得关注的技术问题,本文分析比较了R407C和R22的特性,特别研究了R407C的非共沸特性和相关应用技术。 相似文献
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为了解决多输入多输出和产品质量不易在线测量的化学机械研磨(chemical mechanical polishing,CMP)过程R2R(run-to-run)控制的难题,提出了一种基于贝叶斯最小二乘支持向量机(Bayes least squares support vector machine,BLS-SVM)预测模型和克隆选择免疫多目标滚动优化算法的CMP过程多变量R2R预测控制器BSVMPR2R.由LS-SVM和贝叶斯证据框架(Bayes evidence framework,BEF)方法分别构建材料去除率(material removal rate,MRR)和晶圆内非均匀度(within-wafer nonuniformity,WIWNU)的BLS-SVM预测模型,解决了线性预测模型的失配问题;通过预测误差对后续批次过程扰动和漂移进行在线估计实现反馈校正,提高了预测模型精度;将多变量控制问题转化为基于2个预测模型的多目标优化问题,由克隆选择免疫多目标滚动优化算法求解最优控制律提高了控制精度.仿真结果表明,BSVMPR2R控制器的性能优于双指数加权移动平均(double exponential weighted moving average,dEWMA)多变量控制器,抑制了CMP过程扰动和漂移的影响,显著降低了MRR和WIWNU的均方根误差. 相似文献
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N. G. R. Iyengar 《International Journal of Mechanical Sciences》1966,8(12):771-777
The Ramberg-Osgood relation which adequately describes the stress-strain curve of a strain-hardening material is extended to formulate the constitutive laws for creep. The constitutive laws which describe primary creep adequately are extended to secondary creep. The results are verified for the case of R.R. 59 at 200°C, Nimonic 80A and Nimonic 90 alloys at 750°C. 相似文献