R1234ze/HCs非共沸混合工质热泵系统循环性能分析

在热泵热水器名义工况下,本文建立了热泵系统循环热力学模型,利用EES程序对混合工质R1234ze/HCs及对应的纯工质热泵系统循环性能进行了对比分析。结果表明:R1234ze/R600在质量分数(20/80)和R1234ze/R600a在质量分数(40/60)存在最优配比,对应的最大制热COP_h分别为3. 41和3. 32,而R1234ze/R290则呈现单调下降趋势。R1234ze/R600(20/80)系统的制热COP_h比R1234ze/R600a(40/60)、R1234ze、R290、R600、R600a系统分别高2. 7%、17%、0. 09%、16. 3%和17. 8%,排气温度为76. 9℃,冷凝压力为0. 711 MPa,压比为6. 32,有望成为新型替代工质。     

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。     

Drop-in replacement in a R134 ejector refrigeration cycle by HFO refrigerants

The present work reports a numerical analysis of a single-phase supersonic ejector working with R134a as well as hydrofluoroolefin (HFO) refrigerants R1234yf and R1234ze(E). Comparisons were made regarding the ejector performances under varying operating conditions and refrigerant mixture proportions. The calculations have been then extended to an existing ejector heat driven refrigeration cycle (EHDRC). R1234yf appears to be a good candidate for drop-in replacement of R134a in a real EHDRC, while using R1234ze(E) would induce some modifications due to its thermodynamic properties. Maintaining the same pressure ratio for the ejector would lead on one hand to better entrainment ratio using R1234ze(E) and on the other hand to reduced coefficient of performance (COP) and cooling power by 4.2% and 26.6% in average, respectively. Using R1234yf under the same conditions induces a decrease of 5.2% for the entrainment ratio, 9.6% for the COP and 19.8% for the cooling power in average.     

Theoretical energy performance evaluation of different single stage vapour compression refrigeration configurations using R1234yf and R1234ze(E) as working fluids

R1234yf and R1234ze(E) have been proposed as alternatives for R134a in order to work with low GWP refrigerants, but this replacement results generally in a decrease of the performance. For this reason, it is interesting to explore ways to improve the system performance using these refrigerants. In this paper, a comparative study in terms of energy performance of different single stage vapour compression configurations using R1234yf and R1234ze(E) as working fluids has been carried out. The most efficient configuration is the one which uses an expander or an ejector as expansion device. On the other hand, using an internal heat exchanger in a cycle which replaces the expansion valve by an expander or an ejector could produce a detrimental effect on the COP. However, for all the configurations the introduction of an internal heat exchanger produces a significant increment on the cooling capacity.     

制冷剂R32特性及其用于空气源热泵热水器的理论循环分析

介绍R32,R22和R407C以及R410A四种制冷剂的流动特性和热力学特性,并对采用这4种制冷剂的空气源热泵热水器进行理论循环分析。从计算结果可以看出,与采用其他3种制冷剂的系统对比,采用R32制冷剂的系统具有较低的压缩比,较高的理论COP以及容积制热量;在当前阶段,R32是用于空气源热泵热水器的一种较好的制冷剂。     

R1234yf and R1234ze(E) as low-GWP refrigerants for residential heat pump water heaters

Owing to the growing concerns about the relatively high global warming potential (GWP) of current refrigerants, a serious effort is in progress to find lower-GWP substitutes. The hydrofluoroolefin (HFO)-based refrigerants R1234yf and R1234ze(E) are being considered for use in multiple heating, ventilation, air conditioning, and refrigeration applications because of their very low GWP. A study was conducted to model a residential heat pump water heater using these HFOs. A system model was calibrated using experimental data and the calibrated model was used to evaluate the potential of HFOs to replace R134a. A series of parametric analyses were used to investigate the impacts of condenser wrap pattern, condenser tube size, evaporator size, and heat loss factor from the storage tank. It has been shown that both R1234yf and R1234ze(E) can be substituted for R134a with comparable performance and no substantial modifications to the original system. This study presents a detailed feasibility analysis for successful replacement of high-GWP refrigerants with low-GWP refrigerants with acceptable performance.     

Thermodynamic assessment of high-temperature heat pumps using Low-GWP HFO refrigerants for heat recovery

Reducing energy consumption by utilizing heat recovery systems has become increasingly important in industry. This paper presents an exploratory assessment of heat pump type heat recovery systems using environmentally friendly refrigerants. The coefficient of performance (COP) of 4 cycle configurations used to raise the temperature of heat media to 160 °C with a waste heat at 80 °C is calculated and compared for refrigerants R717, R365mfc, R1234ze(E), and R1234ze(Z). A multiple-stage “extraction” cycle drastically reduces the throttling loss and exergy loss in the condensers, resulting in the highest COP for R1234ze(Z). A cascade cycle using R1234ze(Z) and R365mfc has a relatively high COP and provides practical benefits. Even under adverse conditions, the primary energy efficiency is greater than 1.3 when the transmission end efficiency of the electric power generation is 0.37. The assessment demonstrated that high-temperature heat pumps are a promising approach for reducing primary energy consumption for industrial applications.     

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。     

Flow boiling of non-azeotropic mixture R32/R1234ze(E) in horizontal microfin tubes

Flow boiling of a potential refrigerant R32/R1234ze(E) in a horizontal microfin tube of 5.21 mm inner diameter is experimentally investigated. The heat transfer coefficient (HTC) and pressure drop are measured at a saturation temperature of 10 °C, heat fluxes of 10 and 15 kW m^?2, and mass velocities from 150 to 400 kg m^?2 s^?1. The HTC of R1234ze(E) is lower than that of R32. Degradation in the HTC of the R32/R1234ze(E) mixture is significant; the HTC is even lower than that of R1234ze(E). The HTC is minimized at the composition 0.2/0.8 by mass, where the temperature glide and the mass fraction distribution are maximized. A predicting correlation based on Momoki et al. (1995) associated with the correction methods of Thome (1981) to consider the mass transfer resistance and Stephan (1992) to consider the additionally required sensible heat is proposed and validated with the experimental results.     

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.     

Experimental investigation on heating performance of gas-injected scroll compressor using R32, R1234yf and their 20wt%/80wt% mixture under low ambient temperature

In this paper, an integrated gas-injected scroll compressor heat pump system using R1234yf, R32 and its binary mixtures as working fluid was developed and their heating performances under low ambient temperature were quantitatively evaluated. A composite test system consisting of second-refrigerant calorimeter and water-cooled condenser was used to test the system working performance. The condensing temperature, evaporating temperature, compressor power input and other variables were analyzed to evaluate the system heating capability and energy efficiency. Test results showed that the R1234yf system can run at an evaporating temperature of −25 °C. R1234yf/R32 mixture can run at an evaporating temperature of −20 °C and it has the highest heating COP value among other refrigerants; R1234yf/R32 gas injection system provided very significant performance improvements for heating performance, compared with no gas injection, the heating capacity and heating COP can improve 16%~20% and 13%~16%, respectively.     

Comparative experimental study of low GWP alternative for R134a in a walk-in cold room

The environmental problems induced by the ongoing increase in the global worming potential (GWP) pose a significant interest among researchers. It was found that, the currently used refrigerants are with high GWP (National Refrigerants Inc., 2004), so that it becomes necessary to search for alternatives to these refrigerants that can properly operate on the same systems but with low GWP. Therefore a walk-in cold room working with vapor compression cycle is constructed and tested in this paper. The performance of R134a refrigerant with high GWP is compared to another low GWP refrigerant R1234ze in a trail to provide a solution of the problem of high GWP of refrigerants currently used in cold rooms. The results obtained in this study have shown that, the cooling capacity of R1234ze was lower than that of R134a by 2% to 13%. The lowest evaporating temperature that could be reached for R1234ze is −13 °C while the lowest temperature of R134a is −30 °C. Regarding the power consumption, R1234ze has lower power consumption than R134a by about 9% to 15% therefore it can be concluded that R 1234ze can be recommended to be used at high and medium evaporating temperature after carrying out the suitable modifications on the refrigeration cycle.     

R32在家用空调器中的应用研究

对比R32与R410A的基本物性和热力循环性能,并在同一台家用定频热泵空调器上进行性能测试。相对于R410A,在给定工况下,R32的理论循环制冷量最大可提高15％,能效比最大提高6％,容积制冷量和容积制热量增加7％～8．9％。性能测试结果表明,R32系统的制冷剂充注量比R410A系统的减少24％,额定制冷能力和能效比比R410A系统分别提高8％和3．3％,额定制热能力和性能系数也高于R410A系统。理论热力循环分析及性能测试结果均表明,R32制冷性能相对R410A有较大幅度的提高,制热性能比R410A略高或相当,但R32系统的排气温度较高,比R410A系统高出11．5～25．7℃,恶劣工况下排气温度甚至能达到114．9℃。     

Performance investigations of an R404A air-source heat pump with an internal heat exchanger for residential heating in northern China

Air-source heat pumps (ASHP) have been widely used for residential heating due to its energy-saving and high efficiency characteristics. However, the performance of an ASHP reduces as the ambient temperature decreases. In order to investigate the effect of ambient temperature on ASHP performance, an ASHP with an internal heat exchanger (IHX) using R404A as refrigerant was developed and studied at low ambient temperatures. The theoretical simulation was first performed to evaluate the performance of the ASHP with IHX and compared with three different cycles. The simulation results were validated by data available from literature and experimental data in this study. The results showed that the R404A ASHP system with IHX had a good potential for residential heating. Further investigation was performed to compare the performance of the R404A ASHP with and without IHX. The comparison results showed that the performance of the ASHP with IHX was far better than that of the ASHP without IHX. As the ambient temperature decreased from 0 °C and −26 °C, the improvement of the heating capacity of the R404A ASHP with IHX increased from 5.91% to 15.92% while the COP improvement increased from 10% to 20%. This indicated that the IHX technology became more and more effective as the ambient temperature dropped lower and lower.     

启停过程对空气源热泵-冷柜一体机性能影响的实验研究

空气源热泵-冷柜一体机中热泵的启停过程不仅会影响系统供热性能,还会影响冷柜性能.本文实验研究了在单独运行及联合运行工况下考虑空气源热泵的启停过程的空气源热泵-冷柜一体机的性能,分析了空气源热泵的启停次数对热泵系统和冷柜系统性能的影响.实验结果表明:相比热泵单独运行工况,空气源热泵-冷柜一体机中热泵制热量的衰减开始时间延...     

Isothermal vapor liquid equilibrium measurements for difluoromethane (R32) + fluoroethane (R161) + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) ternary mixtures

Difluoromethane (R32) + fluoroethane (R161) + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) ternary system could be a promising alternative refrigerant mixture. The vapor liquid equilibrium (VLE) data for this system are important for the evaluation of its performance. In this work, the VLE of R32 + R161 + R1234ze(E) were measured for the first time by a quasi-static analytical apparatus over the temperature range of 283.15 to 323.15 K. The ternary system of R32 + R161 + R1234ze(E) is a zeotropic system within the studied temperature range. The Peng–Robinson–Stryjek–Vera (PRSV) equation of state combined with the Wong–Sandler (WS) mixing rule and the non-random two-liquid (NRTL) activity coefficient model was used to predict the ternary VLE data by using the parameters of binary mixtures (R32 + R161, R32 + R1234ze(E) and R161 + R1234ze(E)). The calculated values show excellent agreement with the experimental results. The average absolute deviation (AAD) of pressure is 0.16%. The average absolute deviations of vapor phase mole fractions for R32 and R161 are 0.0021 and 0.0028, respectively.     

Analysis based on EU Regulation No 517/2014 of new HFC/HFO mixtures as alternatives of high GWP refrigerants in refrigeration and HVAC systems

The EU Regulation No 517/2014 is going to phase-out most of the refrigerants commonly used in refrigeration and air conditioning systems (R134a, R404A and R410A) because of their extended use and their high GWP values. There are very different options to replace them; however, no refrigerant has yet imposed. In this paper we review and analyze the different mixtures proposed by the AHRI as alternative refrigerants to those employed currently. These mixtures are composed by HFC refrigerants: R32, R125, R152a and R134a; and HFO refrigerants: R1234yf and R1234ze(E). It is concluded, from the theoretical analysis, that most of the new HFO/HFC mixtures perform under the HFC analyzed (although some experimental studies show the contrary) and, in most cases, do not meet the GWP restrictions approved by the European normative. Furthermore, some of the mixtures proposed would have problems due to their flammability.     

混合制冷剂R1234yf/R32 PVTx性质的实验研究

为了获得混合制冷剂R1234yf/R32的热物性数据,本文以Burnett法为基础搭建了高精度PVTx实验台,在温度为253~313 K时,测定了质量分数为15%/85%和25%/75%混合制冷剂R1234yf/R32的PVT性质,拟合了两种不同配比的混合工质的气态维里方程,为进一步研究该工质的基础热物性提供了详实的数据。     

Exergy analysis of R1234yf and R1234ze as R134a replacements in a two evaporator vapour compression refrigeration system

Exergy analysis is a useful way for determining the real thermodynamic losses and optimising environmental and economic performance in the systems such as vapour compression refrigeration systems. The present study deals with the exergy analysis on a two evaporator vapour compression refrigeration system using R1234yf, R1234ze and R134a as refrigerants. In the calculation of losses occurring in different system components, besides the exergy efficiency of the refrigeration cycle, a computer code was developed by using Engineering Equation Solver (EES-V9.172-3D) software package program. The effects of the evaporator and condenser temperatures on the exergy destruction and exergy efficiency of the system were investigated. R1234yf and R1234ze, which are good alternatives to R134a concerning their environmentally friendly properties and this is the most significant finding emerging from this study.     

An experimental investigation of refrigerant mixture R32/R290 as drop-in replacement for HFC410A in household air conditioners

In the present paper, the refrigerant mixture R32/R290 (68%/32% by weight) is investigated as the drop-in replacement for R410A in household air conditioners. The GWP of it is only 22% of that of R410A. Theoretical and experimental investigations are conducted on the performance of the air conditioners working with both R32/R290 and R410A. Experimental results show that the refrigerant charge amount of R32/R290 is reduced by 30.0%–35.0%; the cooling and heating capacities are increased by 14.0%–23.7%. For further reducing charge amount and flammability, the micro-channel heat exchanger (condenser) is employed to replace the finned tube one. Compared with the R32/R290 system using finned tube heat exchanger, the R32/R290 charge amount and the power consumption are reduced by 34.1% and 0.4%, respectively; the cooling capacity and the COP are increased by 6.4% and 6.8%, respectively.