R245fa传热性能实验

蒸发器和冷凝器的传热性能是影响制冷机组和双工质发电机组做功效率的关键因素,为了提高中低温余热在热泵机组和地热双工质发电系统中的利用效率,本文选用R245fa循环工质,对满液式蒸发器和冷凝器进行实验研究,分别讨论热水温度进口温度对蒸发器和冷凝器的传热系数、蒸发压力和冷凝压力的影响。研究结果表明,在工质流量和冷却水流量保持不变的条件下,蒸发器传热系数随着热水进口温度和温差的增大而减小,冷凝器的传热系数随着热水进口温度的增加先增大后减小,蒸发器传热系数可以达到2500 W/(m2?℃);蒸发器压力和汽轮机前后的压差随着热水出口温度的增加而增加,热水流量对蒸发压力和冷凝压力的变化浮动较小。     

R245fa传热性能实验研究

蒸发器和冷凝器的传热性能是影响制冷机组和双工质发电机组做功效率的关键因素,为了提高中低温余热在热泵机组和地热双工质发电系统中的利用效率,本文选用R245fa循环工质,对满液式蒸发器和冷凝器进行实验研究,分别讨论热水温度进口温度对蒸发器和冷凝器的传热系数、蒸发压力和冷凝压力的影响。研究结果表明,在工质流量和冷却水流量保持不变的条件下,蒸发器传热系数随着热水进口温度和温差的增大而减小,冷凝器的传热系数随着热水进口温度的增加先增大后减小,蒸发器传热系数可以达到2500 W/(m2·℃);蒸发器压力和汽轮机前后的压差随着热水出口温度的增加而增加,热水流量对蒸发压力和冷凝压力的变化浮动较小。     

R417A热泵热水器性能及螺旋套管冷凝器换热研究

本文以R417A为工质,在冷凝器不同进水温度、不同进水体积流量时,测试了空气源热泵热水器的运行性能及螺旋套管冷凝器的换热特性,为制冷空调及热泵系统的工质替代提供参考。实验工况为:冷凝器入口水温20～55℃,冷凝器进水体积流量为0.6～1.0 m~3/h,环境温度分别为15、29℃。结果表明:冷凝器进水体积流量一定时,随入口水温的升高,冷凝器总换热量、总传热系数减小,压缩机排气压力、输入功率增大,热泵热水器制热量、制热性能系数COP下降。冷凝器入口水温一定时,随进水体积流量的增加,冷凝器总换热量、总传热系数增大,压缩机排气压力、输入功率减小,热泵热水器制热量、COP增大。实验工况范围内,与环境温度为15℃相比,环境温度为29℃时的冷凝器总换热量、总传热系数、排气压力、吸气压力、输入功率、制热量、COP均较高。     

翅片管式换热器空气侧热阻和压降的测量误差分析及控制

空调系统设计研发过程中,换热器的性能评估是一项重要的工作。本文通过工程应用实例,介绍如何通过空调系统EER/COP和制冷/制热能力的可接受偏差确定翅片管式换热器空气侧热阻和压降的测量误差,并对空气侧热阻和压降的测量误差控制进行研究。该方法对空调系统的研发具有一定的指导意义。     

R1233zd(E)与冷冻机油的溶解特性研究

R1233zd(E)因良好的环保性能和循环特性而受到广泛关注。为解决R1233zd(E)与冷冻机油的匹配问题,本文研究了R1233zd(E)与常用冷冻机油的互溶性、溶解度。在温度范围-40~40 ℃内,测试了R1233zd(E)与矿物油SUNISO 3GS,多元醇脂类（POE）润滑油RL32H、RL68H,聚乙烯醚类（PVE）润滑油FVC68D的临界互溶温度。结果表明：R1233zd(E)与矿物油在标准工况下能够互溶,但在-20 ℃下开始出现絮状物和分层现象。R1233zd(E)与POE油、PVE油互溶性良好,临界互溶温度低于-40 ℃。考虑到R1233zd(E)常应用于高温工况,建议选用闪点、黏度等级较高的POE68号润滑油。基于等体积饱和法,在温度范围40~120 ℃内测试了R1233zd(E)在POE68中的溶解度,溶解度随着压力的升高而增大,随着温度的升高而减小。     

R290直接接触冷凝制冷循环性能分析对比

本文分析了R290直接接触冷凝(DCC)制冷循环的性能,并与R290常规单级压缩制冷循环的热力性能进行对比,得出:在最佳主循环冷凝温度下,R290直接接触冷凝制冷循环可获得最大性能系数和最低冷凝器热负荷。主循环过冷液体的过冷度增大,最优性能系数降低、最低冷凝器热负荷增加、蒸发器的制冷剂质量流量减少,同时,获得最优性能系数和最低冷凝器热负荷的最佳主循环冷凝温度升高。当蒸发温度为-15～-6℃,R290直接接触冷凝制冷循环相比R290单级压缩制冷循环的性能系数提高了7.5%～14.9%,冷间供冷设备蒸发器的制冷剂质量流量减少了26.5%～36.7%,冷凝器热负荷减少了1.5%～3.7%。结果表明R290直接接触冷凝制冷循环具有很好的发展前景。     

铜翅片换热器开发应用的分析Ⅱ--铜翅片换热器对空调器性能影响分析

在Part Ⅰ中对铜翅片效率、铜换热单元传热系数以及整个铜换热器换热特性分析的基础上，理论分析了空调换热器采用铜翅片后，换热器单体性能以及空调系统性能的变化。结果显示：采用铜片铜管换热器后(不论是蒸发器，还是冷凝器)，制冷系统的制冷系数较之铝翅片换热器均有提高。蒸发器换热性能的变化比冷凝器换热性能的变化对系统性能的影响要大。当同时采用铜片蒸发器和铜片冷凝器时，传热强化系数按照通常所能达到的1．1计算时，COP随着工况变化而变化的范围可以达到3．0％-10．0％；如果单独设计换热器使换热强化系数达到1．3时，则COP的提高可达4．0％～25．0％。以上对铜翅片换热器开发应用的分析，为空调换热器的高性能化、小型化提供一条可行的发展方向。     

R32与POE或PVE润滑油混合物的物性计算模型与分析

准确计算制冷剂-润滑油混合物的热力性能是分析和评价润滑油对压缩机性能影响的基础。根据厂家提供的实验数据,利用显式拟合关联式法和经验公式修正,本文分别给出了R32/POE和R32/PVE混合物工质对的物性计算模型,同时用相同的方法给出了R410A/POE的混合物溶解度与黏度计算模型来进行对比,模型对物性参数的预测值与厂家提供的实验数据的偏差均在5%以内,为压缩机优化设计及性能分析提供了准确、可靠的热力学模型。此外,在GX工况下对比分析了混合物溶解度随温度、压力的变化及混合物黏度随溶解度、温度、压力的变化,并对混合物的物性做了比较分析,对于制冷剂R32,PVE润滑油较POE润滑油更适用于;而对于润滑油POE,R32与POE的混合性较R410A与POE的混合性好。     

车用热泵用小管径管片式换热器性能研究

目前车用空调冷凝器均为平行流冷凝器,作为热泵蒸发器时易结霜,且化霜时排水不畅。而圆管翅片换热器换热性能较差,难以满足结构布置要求。开发了Ф5管径的小管径换热器,与平行流换热器进行了性能对比测试。结果表明:采用小管径管片式换热器时,制冷模式下COP提高了17.4%~23.7%,热泵模式下COP提高12.6%~35.8%,且在热泵模式下可降低压缩机排气温度15~28℃。小管径管片式换热器在电动汽车热泵系统应用前景广阔。     

特种车用高温空调研究

针对高温和宽温带范围等特殊工作环境空气调节的需要,研发了HLD-45B高温空调。该空调使用R22/R142b混合制冷剂,采用常规空调制冷循环系统,冷凝器传热面积和风量的设计较常规空调增大15%~20%。进行了焓差法性能实验和宽温区运行实验。实验结果表明:在较宽的环境温度变化范围内HLD-45B具有良好的运行性能:1)标准空调工况至75℃高温工况,蒸发器回风温度与送风温度的差值变化平缓,制冷量最大衰减小于15%,在宽温区空调系统运行稳定、可靠;2)75℃高温工况的排气压力和排气温度分别为2.84MPa和121℃,在理想的安全范围。中高温混合制冷剂的合理使用可改善制冷系统的高温运行性能和可靠性,拓宽其运行温度范围。     

Experiment and simulation on the performance of an autocascade refrigeration system using carbon dioxide as a refrigerant

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility of keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.

Résumé

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility in keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.     

R32及其常用两种润滑油POE和PVE物性计算模型

准确计算制冷剂和润滑油的物性是压缩机优化设计的基础。本文根据已知数据,通过显式拟合法,给出了在常见范围内制冷剂R32饱和液体、饱和气体、过热气体及POE和PVE润滑油的热物性计算模型,并比较分析了这些物质的物性的特点。模型对物性参数的计算值与已知数据的偏差均在5%以内,为R32与POE或PVE混合物物性计算奠定了基础。本文提出的计算模型简单、可靠,可使模拟计算时间更短、精度更高。     

Numerical research on R32/R1234ze(E) air source heat pump under variable mass concentration

R32/R1234ze(E) mixtures are potentially low-GWP alternative refrigerants for air conditioning and heat pumps while the rare pure refrigerants can totally meet the requirements of new international protocols on environmental conservation, thermodynamic performance, and safety. The system performance under different concentrations is important for selection of working concentration for the new R32/R1234ze(E) refrigeration or heat pump. In this paper, the thermodynamic model of an ASHP with R32/R1234ze(E) mixtures is built and used to investigate the influence of the refrigerant composition on the performance of the system. The results show that when the mass fraction of R1234ze(E) changes from 0% to 100%, the heating capacity of the ASHP decreases by 67.2%, while the COP continuously increases by 70.3%, which means the changing tendency of system COP is quite different from previous research under fixed evaporating and condensing temperature. Adjusting the refrigerant concentration will be a good system modulation method for ASHPs with R32/R1234ze(E) to meet both the heating capacity and energy efficiency requirements. Furthermore, temperature matching degree is an important factor that affects the energy efficiency of ASHPs with non-azeotropes, which can guide the circuitry optimization of evaporator and condenser in ASHPs with non-azeotropes.     

Effects of synthetic oil in a compression refrigeration system using R410A. Part II: quality of heat transfer and pressure losses within the heat exchangers

The consequences of the oil rejected by the compressor of a vapour-compression refrigeration system on the operation of the evaporator and condenser are analysed. The modelled prototype uses the mixture of HFC R410A and a synthetic polyolester (POE) oil. The rise of the amount of lubricant circulating in the system leads to a progressive change in the behaviour of the mixture of refrigerant and oil that, for the higher oil mass fraction, evolves like a zeotropic mixture. One also observes that the presence of lubricant is generally associated with a fall of the performances of the heat exchangers, except however in the evaporator where an optimum is observed when the quantity of oil is equal to 0.1% of the total mass of the mixture. Some conclusions are drawn about the choice of correlations for the calculation of the refrigerant side heat transfer coefficient in a plate evaporator.     

Exergetic analysis of a vapour compression refrigeration system with R134a, R143a, R152a, R404A, R407C, R410A, R502 and R507A

This communication deals with the exergetic analysis of a vapour compression refrigeration system with selected refrigerants. The various parameters computed are COP and exergetic efficiency in the system. Effects of degree of condenser temperature, evaporator temperature and sub-cooling of condenser outlet, supper-heating of evaporator out let and effectiveness of vapour liquid heat exchanger are also computed and discussed. In this study, it was found that R134a has the better performance in all respect, whereas R407C refrigerant has poor performance.     

Pressure-enthalpy charts for mixtures of oil and refrigerant R 12

Pressure-enthalpy charts are presented for refrigerant R 12-oil mixtures, for a range of oil concentrations. The effect that the existence of this mixture has on evaporator performance and COP of a refrigeration/heat pump system is discussed and some results are compared with the pure refrigerant cycle normally considered.     

某地铁列车空调制冷系统的仿真与优化

我国的地铁建设正处于高速发展期,但目前典型地铁列车空调制冷系统的能效比只有2.2～2.3,远低于同类工况下住宅空调制冷系统的能效水平。针对此问题,先建立了某地铁空调制冷系统模型,仿真与系统测试结果吻合良好。然后通过详细的仿真分析,改进蒸发器和冷凝器的制冷剂流路设计、采用小排量高能效比压缩机等方法,使得系统在冷量和成本基本不变的情况下能效比提升了21.7%。最后,研究了制冷剂R410A替代R407C的系统性能变化,系统能效比可进一步提升11.3%,达到3以上。该研究方法及结果对于设计高效节能的地铁列车空调制冷系统具有参考价值。     

Hybrid vapor compression refrigeration system with an integrated ejector cooling cycle

A refrigeration system was developed which combines a basic vapor compression refrigeration cycle with an ejector cooling cycle. The ejector cooling cycle is driven by the waste heat from the condenser in the vapor compression refrigeration cycle. The additional cooling capacity from the ejector cycle is directly input into the evaporator of the vapor compression refrigeration cycle. The governing equations are derived based on energy and mass conservation in each component including the compressor, ejector, generator, booster and heat exchangers. The system performance is first analyzed for the on-design conditions. The results show that the COP is improved by 9.1% for R22 system. The system is then compared with a basic refrigeration system for variations of five important variables. The system analysis shows that this refrigeration system can effectively improve the COP by the ejector cycle with the refrigerant which has high compressor discharge temperature.     

Performance evaluation of a heat pump cycle using NARMs by a simulation with equations of heat transfer and pressure drop

Simulation analyses for a vapour compression heat pump cycle using nonazeotropic refrigerant mixtures (NARMs) of R22 and R114 are conducted under the condition that the heat pump thermal output and the flow rate and inlet temperatures of the heat sink and source water are given. The heat transfer coefficients of the condensation and evaporation are calculated with empirical correlations proposed by the authors. The validity of the evaluation method and the correlations is demonstrated by comparison with experimental data. The relations between the coefficient of performance (COP) and composition are shown under two conditions: (1) the constant heat transfer length of the condenser and evaporator; and (2) the constant temperature of refrigerant at the heat exchanger inlet. The COP of the NARMs is higher than that of pure refrigerant when the heat transfer lengths of the condenser and evaporator are sufficiently long.     

A study of working fluids for heat driven ejector refrigeration using lumped parameter models

This paper studies the influence of working fluids over the performance of heat driven ejector refrigeration systems performance by using a lumped parameter model. The model used has been selected after a comparison of different models with a set of experimental data available in the literature. The effect of generator, evaporator and condenser temperature over the entrainment ratio and the COP has been investigated for different working fluids in the typical operating conditions of low grade energy sources. The results show a growth in performance (the entrainment ratio and the COP) with a rise in the generator and evaporator temperature and a decrease in the condenser temperature. The working fluids have a great impact on the ejector performance and each refrigerant has its own range of operating conditions. R134a is found to be suitable for low generator temperature (70–100 °C), whereas the hydrocarbons R600 is suitable for medium generator temperatures (100–130 °C) and R601 for high generator temperatures (130–180 °C).