R22、R404A与R407F制冷剂压缩机性能对比

分析R22、R404A与R407F制冷剂的物理性质,并采用涡旋压缩机进行试验测试。结果表明:在高温应用上,R22、R404A和R407F制冷能力数值相近,R407F制冷系数比R22、R404A稍低;而在低温应用上,R407F制冷能力、制冷系数比R22、R404A都低。     

R404A和R407A冷冻涡旋式压缩机性能比较

对制冷剂R404A与R407A的热物理特性进行比较,探讨R407A应用于冷冻涡旋式压缩机的可行性,并对这2种制冷剂涡旋式压缩机进行测试,根据容积效率、等熵效率、排气温度、压缩机电流等参数的比较分析,为R407A涡旋式压缩机的开发提供参考依据。     

R1234ze(E)在R134a离心式制冷压缩机中的直接替代研究

随着全球对环保要求的日益提高,以R1234yf、R1234ze(E)、R1233zd(E)等为代表的ODP为0且GWP较低的制冷剂得到广泛关注并应用。针对R134a离心式冷水机组,采用CFD数值方法,对采用R1234ze(E)直接替代的离心制冷压缩机进行了模拟,对机组性能进行了比较分析。结果表明：在同一转速下,当冷凝温度较小时,R1234ze(E)机组的制冷量和COP都小于R134a机组的,当冷凝温度较大时,R1234ze(E)机组的制冷量和COP都大于R134a机组的。当R134a机组与R1234ze(E)机组的蒸发温度、冷凝温度和制冷量都相同时,R1234ze(E)机组的COP比R134a机组的COP平均降低了约5.14%。     

HFOs制冷剂在制冷空调领域的替代研究综述

在气候变化和一系列政策法规的推动下,新型替代制冷剂的研发工作成为行业热点,其中HFOs及其混合制冷剂在当前广受关注。本文根据现阶段HFOs制冷剂的研究现状,针对HFOs纯制冷剂的热物性,基于理想单级蒸气压缩循环考虑其在空调、热泵两种工况下的替代潜能,对HFOs制冷剂与所替代制冷剂进行理论对比分析,模拟结果初步表明:R1234yf,R1234ze(E),R1233zd(E),R1123,R1243zf,R1141,R1132(E)和R1225ye(Z)可作为制冷空调系统候选替代制冷剂;R1234ze(Z),R1233zd(E)和R1336mzz(Z)可作为热泵候选替代制冷剂。在HFOs混合制冷剂的分析中,针对R134a,R404A,R407C和R410A这几种制冷剂,依据不同的工况对可能的替代制冷剂进行理论循环计算,理论分析结果初步表明:R450A和R513A具有替代R134a制冷剂的潜力;R448A,R449A,R452A,R454A,R454C和R455A具有替代R404A制冷剂的潜力;R444B,R449A和R454C具有替代R407C制冷剂的潜力;R452B和R454B具有替代R410A制冷剂的潜力。最后根据上述分析总结出不同应用场合下HFOs制冷剂的初步替代方案,为HFOs制冷剂作为潜在的替代物提供有价值的参考。     

低温装置用R502替代工质的性能分析

本文对替代低温装置制冷剂R502的混合工质(如R404a、R507、R407a、R407b、R407c)进行了热力计算和循环分析,结果表明R407a、R407b、R407c可作为R502的替代工质,且比R404a和R507具有明显的节能效果。     

R22,R407C和R410A热泵专用涡旋式压缩机研究

分析多种热泵制冷剂物理性质,并对热泵用涡旋式压缩机运行特性进行分析。采用新设计的热泵专用涡旋式压缩机进行R22,R407C与R410A性能测试,结果表明:R410A和R407C制冷剂均可以替代R22制冷剂在热泵系统中使用;R410A与R22在制热能力、排气温度及运行范围方面相近;R407C的制热能力高于R22和R410A,运行范围相对较宽。     

不同制冷剂对气悬浮压缩机电机冷却及系统性能的影响

电机冷却是保障气悬浮离心制冷压缩机可靠运行的关键。本文建立了气悬浮离心制冷压缩机的数学模型，分析了不同制冷剂(R134a、R1234yf、R1234ze(E))对电机冷却过程和制冷系统性能的影响。研究结果表明：采用R1234ze(E)时电机内部温度最高，电机永磁体最高温度比采用R134a和R1234yf时高60～90℃;采用3种制冷剂时电机的绕组平均温度均随冷却入口温度的升高而降低；采用R134a和R1234yf时永磁体最高温度均随冷却入口温度的升高而降低，采用R1234ze(E)的永磁体最高温度随冷却入口温度的升高先增后降，在冷却入口温度约为25℃时最高。冷却入口温度每上升4.5℃,电机冷却回路的出口干度下降约3%～5%。带电机冷却支路的系统与传统系统相比，电机温度可以控制在更安全的运行范围之内，但采用R134a、R1234yf、R1234ze(E)的系统COP分别降低1.23%～1.82%、1.23%～1.65%、1.14%～1.17%。     

R1234yf热泵技术综述与潜力分析

为了满足逐步严苛的环保法规要求,R1234yf成为车用热泵制冷剂R134a的热门替代制冷剂之一。本文对R1234yf热泵技术的研究进行了综述与分析,其GWP<1,各方面性质均符合车用热泵系统的工作需求。在传热效果上,R1234yf的沸腾传热性能略优于R134a,且冷凝过程压降比R134a低5%～10%,优于R134a系统。在诸多R1234yf和R134a系统的仿真和实验研究中,R1234yf热泵性能略低于R134a,但可以通过优化零部件、强化补气、改善工况等方式使其与R134a十分接近甚至超越。R1234yf低压饱和压力比R134a高约15%,可以适配更高的压缩机转速,低温下制热性能比R134a更好,且较低的压缩机排气温度使系统工作更为稳定,强化补气的效果也优于R134a。因此,R1234yf在车用热泵中具有较好的工作性能和发展前景,可以作为R134a的替代制冷剂。     

R1234ze(E)在水平圆管内流动沸腾换热过程中摩擦压降特性实验研究

新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对比。实验研究的流动沸腾换热的饱和温度为10℃,热流密度为5.0 k W/m~2和10.0 k W/m~2,质流密度范围为300~500 kg/(m~2·s),并分析质流密度、热流密度对R1234ze(E)和R134a饱和流动沸腾过程中摩擦压降的影响。结果表明,在相同工况下R1234ze(E)的流动沸腾过程的摩擦压降略大于R134a,如质流密度为500 kg/(m~2·s)时,R1234ze(E)的平均摩擦压降值比R134a大8.4%左右。最后,将实验结果同四种摩擦压降经验关联式进行比较分析。     

美国：R450A制冷剂或将取代R134a

近日,美国环境署（EPA）宣布将把R450A制冷剂列入新的替代制冷剂中。据悉,R450A制冷剂是由霍尼韦尔公司开发的,该制冷剂是一种不可燃烧的混合物,组分配比是42%的R134a和58%的R1234ze,ODP值为零,GWP值大约为601。     

风冷螺杆热泵机组制冷剂替换试验研究

对R22、R407c、R134a三种制冷剂的基本物性及热力性能进行了分析比较，并在风冷螺杆热泵机组基础上进行了替换试验研究。结果表明：R407c为最佳替换R22的制冷剂；R134a替换后能效比较高，但制冷（热）量衰减过多，同时R134a的运行压力过低不太适合热泵工况。     

HFC-161及其应用

介绍ODs替代品HFC-161的性质及应用实例，通过分析与实验说明这些混合制冷剂能够分别替代R410A，R407C，R404A和HFC-134a，均具有环保性能优异、能效比高、用量少、与原系统兼容等特点。     

Performance degradation of a vapor compression refrigeration system under fouled conditions

Performance degradation due to fouling in a vapor compression cycle is investigated for various applications. Considering the first set of refrigerants i.e. R134a, R410A and R407C, from a first law standpoint, the COP indicates that R134a always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R134a performs the best in all cases. Considering the second set of refrigerants i.e. R717, R404A and R290, from a first law standpoint, the COP indicates that R717 always performs better unless only the evaporator is being fouled. In contrast to this, from a second-law standpoint, the second-law efficiency indicates that R717 performs the best in all cases. Volumetric efficiency of R410A and R717 remained the highest under the respective conditions studied. Furthermore, performance degradation of the evaporator often has a larger effect on compressor power requirement while that of the condenser has an overall larger effect on the COP. A new performance degradation law is presented in light of the data generated, which can reduce the amount of experimentation and help predict relevant quantities of the refrigeration system.     

R404A和R407C在水平强化管外的凝结换热实验研究

实验研究了近共沸制冷工质R404A与非共沸制冷工质R407C在水平强化换热管管外的凝结换热性能。采用"Wilson图解法"对实验数据进行处理。结果表明:对于R404A和R407C,强化管外的凝结换热系数随着壁面过冷度的增加而增大,呈现出与纯工质冷凝时不同的变化趋势,这主要是近共沸或非共沸工质凝结过程中,某些组分的凝结会遇到其它组分的凝结气膜热阻所造成的;随着过冷度增加,易挥发组分开始凝结,气膜变薄,冷凝传热系数增大。R407C在强化换热管管外的凝结换热系数比R404A要小70%左右,这是由于R407C的温度滑移较R404A要大,管外形成的凝结扩散气膜造成的影响更大。R407C在高热流密度工况下的换热效果提升明显,故应尽量工作在高热流密度区域。     

Experimental study of an R1234ze(E)/R134a mixture (R450A) as R134a replacement

This work presents an experimental analysis of a non-flammable R1234ze(E)/R134a mixture (R450A) as R134a drop-in replacement. While R134a has a high GWP value (1430), the R450A GWP is only 547. The experimental tests are carried out in a vapour compression plant equipped with a variable-speed compressor. The replacement suitability has been studied combining different operating conditions: evaporation temperature, condensation temperature and the use of an internal heat exchanger (IHX). The drop-in cooling capacity of R450A compared with R134a is 6% lower as average. R450A COP is even higher to those resulting with R134a (approximately 1%). The discharge temperature of R450A is lower than that of R134a, 2K as average. The IHX has a similar positive influence on the energy performance of both fluids. In conclusion, R450A can be considered as a good candidate to replace R134a.     

新型制冷剂R1234ze(E)及其混合工质研究进展

低GWP值制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)作为R134a较为理想的替代品而被关注,但其单一成分的热力学性能和传输特性并不理想,在R1234ze(E)中混入R32成分可以有效改善其热力学性能。本文概述了低GWP值工质R1234ze(E)及其与R32混合物的热物性特征、传输特性及系统运行性能方面的研究现状,并与目前常用的制冷工质进行比较分析,指出R1234ze(E)与R32混合工质有望成为新型低GWP值替代工质。     

Condensation heat transfer and two-phase frictional pressure drop in a single minichannel with R1234ze(E) and other refrigerants

R1234ze(E), trans-1, 3, 3, 3-tetrafluoropropene, is a fluorinated propene isomer which may be a substitute of R134a for refrigeration applications. R1234ze(E) has a much lower GWP_100-years than that of R134a. In this paper, the local heat transfer coefficient during condensation of R1234ze(E) is investigated in a single minichannel, horizontally arranged, with hydraulic diameter equal to 0.96 mm. Since the saturation temperature drop directly affects the heat transfer rate, the pressure drop during adiabatic two phase flow of R1234ze(E) is also measured. Predictive models are assessed both for condensation heat transfer and pressure drop. A comparative analysis is carried out among several fluids (R1234ze(E), R32, R134a and R1234yf) starting from experimental data collected at the same conditions and using the Performance Evaluation Criteria (PEC) named Penalty Factor (PF) and Total Temperature Penalization (TTP) to rank the tested refrigerants in forced convective condensation.     

Refrigeration system performance using liquid-suction heat exchangersPerformance d''un système frigorifique utilisant des échangeurs liquide-vapeur à l''aspiration

Heat transfer devices are provided in many refrigeration systems to exchange energy between the cool gaseous refrigerant leaving the evaporator and warm liquid refrigerant exiting the condenser. These liquid-suction or suction-line heat exchangers can, in some cases, yield improved system performance while in other cases they degrade system performance. Although previous researchers have investigated performance of liquid-suction heat exchangers, this study can be distinguished from the previous studies in three ways. First, this paper identifies a new dimensionless group to correlate performance impacts attributable to liquid-suction heat exchangers. Second, the paper extends previous analyses to include new refrigerants. Third, the analysis includes the impact of pressure drops through the liquid-suction heat exchanger on system performance. It is shown that reliance on simplified analysis techniques can lead to inaccurate conclusions regarding the impact of liquid-suction heat exchangers on refrigeration system performance. From detailed analyses, it can be concluded that liquid-suction heat exchangers that have a minimal pressure loss on the low pressure side are useful for systems using R507A, R134a, R12, R404A, R290, R407C, R600, and R410A. The liquid-suction heat exchanger is detrimental to system performance in systems using R22, R32, and R717.