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1.
Characteristics of R22 and its new alternative refrigerant R290 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 ℃, the mass flow rate for R22 is increased by 16%, while the increasing rate for R290 is 13%. 相似文献
2.
In order to select the appropriate working fluids and optimize parameters for medium-temperature geothermally-powered organic Rankine cycle(ORC), R245 fa is mixed with R601 a at geothermal water temperature of 110 ℃. Based on thermodynamics, the characteristics of mixture and its influence on the performance of ORC under different evaporating temperatures and composition proportions are analyzed. Results show that the zeotropic mixture R245fa/R601a(0.4/0.6) has the highest performance. When the evaporating temperature reaches 67 ℃, the outlet temperature of geothermal water is 61 ℃, the net power output is the highest and the thermal efficiency is about 9%. 相似文献
3.
为了评价低温电地板辐射供暖系统的热力性能,设计并构建了一个由恒温小室和不同结构地板组成的实验装置.发热电缆均匀分布在地板层内,额定发热功率为30W/m.由3种不同复合地板结构和8种不同的导线间距组合成24种实验方案,分别进行测试,其中导线间距分别为30,40,50,60,80,100,130,150mm.分析了影响电地板辐射供暖系统热力性能的主要因素及其影响规律.实验结果表明,该系统具有良好的稳定性和可靠性,地板供暖辐射换热量约占总换热量的50%以上.当地板结构相同且感温探头所处位置不变时,存在一个使地板上表面散热量最大的最佳导线间距,实验工况下的最佳导线间距为50mm. 相似文献
4.
根据工程热力学、传热学、热工测试技术等关于换热器性能的基本测试原理和方法,结合现行的国家标准与规范要求,研发了水源热泵用换热器综合实验台.该实验台利用控制与测量技术,采用被测换热器与辅助换热器水侧部分的冷热负荷,通过水-水板式热交换器相互抵消方法,以及换热器两侧热平衡工作原理,即换热器水侧吸收或放出的热量与制冷剂侧放出或吸收的热量基本相等,可以实现在不同工况下对不同结构形式的R22蒸发器及冷凝器的换热性能和流体阻力性能进行全面的测试.为换热器的选型、优化设计和新产品开发提供依据和验证手段. 相似文献
5.
研究了现代空调和制冷系统中非共沸制冷剂发生的组分迁移问题. 研究发现, 组分迁移现象的4种引发机理都与混合工质的分馏有关. 本文模拟了工质在换热器中的分馏滞流. 将换热器分解成若干微元, 选用恰当的空泡数学模型, 计算各组分在换热器中的滞留量. 系统的循环浓度根据换热器中制冷剂的分馏滞留程度来计算. 通过模拟研究, 证明了模型的可靠性. 该研究结果可以应用于提高非共沸制冷剂在制冷设备应用中的可靠性和效率. 相似文献
6.
R12对大气臭氧层有强烈的腐蚀作用.而R134a是一种新型的环保制冷剂,为减少环境污染,可用R134a代换R12.根据对R134a和R12特性的对比分析,改进了空调压缩机、冷凝器、蒸发器、膨胀阀和其他附属部件的具体结构及参数设置,汽车空调制冷系统可得到优化. 相似文献
7.
Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained. 相似文献
8.
9.
Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat… 相似文献
10.
综述了国际上对超临界CO2流体管内对流换热的研究，介绍了影响超临界CO2流体换热的主要因素有热流密度、浮升力、润滑油等，提供了多种超临界CO2流体在冷却工况下的换热关联式，并对研究中存在的问题和以后有待研究的方向提出了建议。 相似文献
11.
根据能带论和电磁学理论讨论了影响电容器电容的因素,认为电容器电容与电容器负极板内价电子最高占据态,即电容器极板的脱出功有关,在同一温度条件下,脱出功大的金属材料做成的电容器电容大。给出了温度对电容器电容的影响及电容器热击穿的原理,给出了阴极放电的正确物理图像。分析了电容器电容与正对面积成正比、与板间距离成反比的物理意义,认为极板面积表明容纳电荷的数量,板间距离反映了电势作用的规律。分析了电容器充电过程的能量转换过程,结果表明,正极板上的静电能在数值上等于正极板内价电子之间相互作用斥力势能的减少量;负极板上的静电能在数值上等于负极板内价电子之间相互作用斥力势能的增加量;正负极板上静电能的总和为零;为电容器充电的电源内部非静电力做功将非静电场能量转化两极板之间的静电场能量,由此证明了长期以来电磁学理论无法证明的电磁场能量是由谁携带的问题。提出了研究电容器极板材料的初步思路,认为半金属、半导体材料或者绝缘体掺杂材料有可能成为大电容的电容器极板材料,这对于人类目前正在研究接收雷电能量具有重要的理论意义和实际意义。 相似文献
12.
余华明 《顺德职业技术学院学报》2008,6(2):15-17
针对使用R134a／R23混合制冷剂的自然复叠制冷系统．编制了基于NISTREFPROP的仿真程序。利用仿真和实验对系统各种优化措施的效果进行了分析和验证。两者都表明：分凝措施有利于降低系统蒸发温度、提高COP;而回热可以略微降低系统蒸发温度,但使系统COP降低、压缩机排气温度升高。 相似文献
13.
A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±8% of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes. 相似文献
14.
Experimental performance of TJR02 as an alternative refrigerant to R22 in a small-scale cold storage
A refrigerant mixture TJR02 was developed and the comparison experiment was performed on a singlestage vapor compression refrigeration system originally designed for R22.Experimental results show that TJR02 can be directly used in the system without modifying the original system or changing lubricant.By replacing R22 with TJR02,cooling rate gets faster and at least 20% of energy is saved.The actual detection in the standard test-bed verifies the experimental results and indicates that the adoption of TJR02 leads to greater efficiency and wider application.And the lower the refrigeratory temperature is,the more obvious the energy saving effects will be. 相似文献
15.
用制冷剂Ｒ２２替代制冷剂Ｒ１２减少对大气臭氧层的破坏。文章在理论和实验中对两种制冷剂在制冷量,压缩功,制冷系数等方面加以分析,并在如何改进其制冷性能,提高效益方面作了探讨。 相似文献
16.
In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a (0.15/0.45/0.40 in mass fraction), as a promising
mixed refrigerant to R404A, is presented. The ozone depletion potential (ODP) of the new refrigerant is zero and its basic
thermodynamic properties are similar to those of R404A, but its global warming potential (GWP) is much smaller than those
of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition I (the average evaporation
temperature: −23 °C, the average condensing temperature: 43 °C, the superheat temperature: 28 °C, the subcooling temperature:
5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher,
respectively, than those of R404A. The coefficient of performance (COP) of the new mixture is 5.19% higher than that of R404A
and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II (the
average evaporation temperature: −40 °C, the average condensing temperature: 35 °C, the superheating temperature: 30 °C, the
subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are
2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A
and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared
in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions (condensing temperatures:
35–45 °C, evaporation temperatures: −40–−20 °C). Experimental results show that the new mixture can obtain a higher COP, by
6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new
mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system. 相似文献
17.
制冷系数是考核制冷机制冷循环的一个重要技术指标,本文对用制冷剂Ｒ２２替代Ｒ１２后的制冷系数作了实验测试和分析探讨。 相似文献
18.
刘丽刚 《顺德职业技术学院学报》2007,5(4):26-28
为探索R290作为制冷剂在家用空调中应用的可行性,在相同型号的空调器中进行了R290与R22的性能对比实验。结果表明:家用空调器不仅可以用R290替代R22,而且还有环保和节能的效果,能效比可提高10.26%～19.53%。 相似文献
19.
水合物法分离含氢气体混合物的实验研究 总被引：1，自引：0，他引：1
许维秀 《荆门职业技术学院学报》2006,21(6):1-4
利用高压水合物分离装置,在不同的温度、压力及液体流量下,分别测定了H2、CH4二元混合物与水合物促进剂进行水合反应时分离效果随时间的变化.结果表明,温度越低,体系压力越高,液体流量越大,H2浓度增加越快,但较高的压力对分离效果影响较小,过大的液体流量会加大液体夹带量.适宜的条件为:温度5~10℃,压力4.5~5.0 MPa,合适的液体流量应根据实际情况确定. 相似文献
20.
Zhan Shiping 《大连大学学报》1991,(4)
本文采用直接迭代法与拉格朗日乘子法对管壳式序贯换热系统进行了模拟与优化,运用本文编制的计算程序,可以使得在传热总面积一定的条件下工艺物流的出口温度最高,并可得到各台换热器的传热面积。 相似文献