用于高温热泵蒸汽系统的几种工质的循环性能

建立了高温热泵蒸汽系统的热力学模型。在蒸发温度为60℃,冷凝温度为120~140℃的工况下,进行经过初步筛选的4种高温热泵纯工质(R123,R141b,R245ca,R245fa)和传统高温热泵工质(R114)的循环性能对比研究。结果表明:R245fa的综合循环性能良好,单位容积制热量最高,其性能系数(COP)比R114平均高13.65%,压缩比与R114最接近;在符合干压缩要求的前提下,排气温度较低,而且环境友好,可作为高温热泵蒸汽系统的工质。     

不同工况下非共沸混合工质有机朗肯循环系统性能研究

采用MATLAB软件模拟非共沸混合工质在不同冷热源条件下对有机朗肯循环(ORC)系统性能的影响。选取R245fa/R1234ze和R245fa/R600a作为混合工质,热源温度取120和200℃,分别在冷凝露点温度为40℃和冷却水温升为5,10,15℃的工况条件下,利用热力学第一定律和火积理论对系统性能进行分析。结果表明：热源温度为200℃时,R245fa, R1234ze和R600a系统净输出功率分别为89.83,61.87和77.74 kW,使用R245fa系统性能优于其混合工质;热源温度为120℃、固定冷凝露点温度时,混合工质R245fa/R600a(90%∶10%)净输出功率比R245fa和R600a分别提高了27.6%和27%,R245fa/R1234ze(60%∶40%)净输出功率比R245fa和R600a分别提高了26%和20.5%;火积耗散和单位面积做功量与净输出功率变化相反,提高冷却水温升时,增大了系统火积耗散,且流向环境中的火积耗散在总火积耗散中占比增大,导致系统的传热不可逆损失增加。     

替代制冷剂在不同领域的研究进展

面临传统制冷剂临近淘汰的问题,寻找理想替代制冷剂成为行业内研究的热点。文中归纳了理想制冷剂的替代目标,介绍了R290等在家用空调领域、R1234yf等在车载空调领域、R417C等在热泵热水器领域、R1234ze以及R1234ze与R32等混合制冷剂在大型冷水(热泵)机组领域的替代情况。同时,针对不同制冷剂在替代时的不足提出了不同的解决方案或建议,如用喷气增焓等方法解决R32排气温度高的问题,通过减小管径解决R290制热量略低的问题,而针对R1234yf、R1234ze制热量低的问题提出了增加中冷器或与在该方面有优势的R32制冷剂混合的方法等。通过汇总替代制冷剂在不同应用领域的研究进展,为选择理想替代制冷剂提供了参考。     

非共沸混合工质应用于复叠式高温热泵系统低温回路的试验研究

为研究不同滑移温度的混合工质应用于复叠式热泵系统低温回路对热泵机组性能的影响,搭建复叠式高温热泵实验台,选用R245fa与R134a/R245fa(质量比分别为9:1、8:2、7:3、6:4)作为高温、低温级循环工质,蒸发器进水温度在20～40℃,冷凝器出水温度在110～130℃的情况下进行试验,并对机组的COP、制热...     

HFC245fa用于高温热泵系统的循环性能评价

以寻求冷凝温度为80～110℃的高温热泵工况范围内的适用工质为目的,对臭氧破坏势COP为零、温室效应势GWP较低的工质HFC245fa进行了循环性能理论和实验研究。结果表明,HFC245fa的理论循环性能优于传统工质CFC114;在实验工况范围内,HFC245fa系统的实际循环性能随运行工况温度的提高而提高。实验中,系统的热输出温度达到了102℃。     

基于采用分液冷凝有机闪蒸循环分液干度分析及优化

分液冷凝是一种新兴的强化传热方法,可以显著提高冷凝传热系数。将分液冷凝应用于有机闪蒸循环(OFC),采用R227ea、R236ea、R245fa、R600、R601、R600a、R601a、R1234ze和R1234yf为循环工质,分别研究了进口干度、分液干度、冷却水温升和质流密度对冷凝器换热面积的影响。研究结果表明:当进口干度较大时,换热面积会随着分液干度的增大而先减小后增大;当分液干度较小时,分液干度越接近进口干度换热面积越小。采用分液冷凝后的冷凝器换热面积相对不分液时减少13.2%~55.3%,且相对减少量随着进口干度的增大而减小。     

分液冷凝有机朗肯循环系统R245fa/HFOs工质选择研究

有机朗肯循环是中低品位热能高效利用的有效技术之一,分液冷凝有机朗肯循环（LSCORC）是基于分液冷凝传热强化的新型热力循环。为寻找新型环保替代工质,建立LSCORC系统的热力学模型,以最大化净输出功为目标,重点考虑了雅各布数、冷热源换热匹配对系统性能的影响,对R245fa/HFOs工质进行了对比筛选。结果表明：工质的雅各布数越大,其净输出功越小;在基础工况下,R245fa/R1336mzz(Z)的热力性能及热经济性表现最佳;当热源参数变化时,雅各布数较小工质的性能表现普遍优于雅各布数较大的工质组合;当冷源参数变化时,在分液冷凝器两个流程中温度滑移和冷源温升匹配越好的工质组合,其系统净输出功越大。     

混合制冷剂在空气源热泵热水器系统中替代R22的可行性研究

空气源热泵热水器系统所用制冷剂主要包括R410A,R407C,R134a,它们的GWP值较高,会对大气环境造成不利影响。将R1234ze/R152a,R290/R1234ze,R152a/R134a分别按一定比例组成混合制冷剂,通过理论分析混合制冷剂的环境影响指数、热力学性能、安全性以及经济性能等因素,并与R410A,R407C,R134a进行对比。分析结果表明,对于配比为3∶7的R290/R1234ze混合制冷剂,其对环境影响较小,饱和压力线与R22相接近,饱和液体密度为R22的1/2,饱和气体比热容大于R22,COP为R22的90%、压力比比R22低5.2%,排气温度比R22和R410A分别低18,20℃。综上可知,混合制冷剂R290/R1234ze是一种性能良好的近共沸混合制冷剂,可替代R22。     

R1234ze(E)与R134a在水平双侧强化管外的凝结换热对比实验

搭建了水平单管降膜蒸发试验台,以第四代制冷剂R1234ze(E)和第三代制冷剂R134a作为工质,在新型水平双侧强化管管外分别进行了改变管内水速、热流密度和冷凝温度条件的凝结换热实验。使用Wilson-Gnielinski图解法计算得到管内表面传热系数h_i,进一步采用热阻分离法分离出两种制冷剂的管外表面传热系数,并分析了管内冷却水水速、冷凝温度和壁面过冷度的变化对其换热性能的影响。实验结果表明:同根实验管下不同制冷剂凝结换热性能的差异与制冷剂物性与强化管结构之间的匹配特性有关,实验管型下,R1234ze(E)的管外凝结换热性能高于R134a。     

R1234yf有机朗肯循环系统热力学性能研究

为提高有机朗肯循环（Organic Rankine Cycle, ORC）在中低温地热发电领域的效率,本文以R1234yf为工质,依据热力学第一定律与第二定律分析了系统单位质量热水净发电功率和系统?效率,并与目前应用广泛的R245fa工质进行了性能对比。研究结果表明,存在最佳蒸发温度和最佳冷凝温度,使得ORC发电系统单位质量热水净发电功率、?效率最大。对于热源温度为110℃ ~ 150℃的ORC发电系统,R1234yf对应的最大系统单位质量热水净发电功率和最大?效率均大于R245fa     

Prospect Evaluation of Low-GWP Refrigerants R1233zd(E) and R1336mzz(Z) Used in Solar-Driven Ejector-Vapor Compression Hybrid Refrigeration System

In this paper, the entrainment ratio, pump work, heat loads of heat exchangers and COPthermal were theoretically evaluated for a solar-driven ejector-vapor compression hybrid refrigeration system with R1233 zd(E) and R1336 mzz(Z) as the working fluids. The evaluation of the utilization potentials of R1233 zd(E) and R1336 mzz(Z) was presented by comparing the system performance with that of R245 fa, a commonly used refrigerant in the ejector system. The results indicated that the systems with R1233 zd(E) and R1336 mzz(Z) had a higher entrainment ratio and lower pump work. The pump works when using R1233 zd(E) and R1336 mzz(Z) can be up to 14.59% and 38.05% lower than those of R245 fa, respectively. Meanwhile, the system showed the highest COP_(thermal) utilizing R1233 zd(E) followed by that of R245 fa, with the R1336 mzz(Z) system having the lowest value. The differences between R1233 zd(E) and R1336 mzz(Z) systems, R1233 zd(E) and R245 fa systems were 4.33% and 2.0%, respectively. This paper was expected to provide a good reference for the utilizing prospect of R1233 zd(E) and R1336 mzz(Z) in ejector refrigeration systems.     

Investigation of Vapor-liquid Ejector with Organic Working Fluids

The vapor-liquid ejector is a simply flow device and driven by thermal energy. In this paper, a modified mathematical model of the vapor-liquid ejector is proposed, and the validation shows good agreements with the experimental data. A study is carried out with six organic working fluids, namely R1233 zd(E), R1336 mzz(Z), R236 ea, R245 ca, R245 fa and R365 mfc. The influences of the entrainment ratio, the area ratio, the superheating at the vapor nozzle inlet, the subcooling at the liquid nozzle inlet, and the pressures at these inlets on the pressure lifting are parametrically investigated. An increase in the subcooling leads to the great increasing of pressure lifting and the superheating has slight effect on the pressure lifting, whereas others have the opposite tendency. The studies of the pressures and temperatures at the typical locations inside the vapor-liquid ejector are further conducted by using R1336 mzz(Z). The results show that the above parameters have great influence on these pressures and temperatures inside except that the pressures are insignificantly impacted by the superheating, and the temperatures are negligibly affected by the area ratio. R1336 mzz(Z) is recommended as a good working fluid for the vapor-liquid ejector.     

Optimum composition ratios of multicomponent mixtures of organic Rankine cycle for engine waste heat recovery

With the temperature glide in saturation states, the mixture working fluids have the advantages in thermal energy conversion. In this study, through the investigation in optimum mass fractions of multicomponent mixture working fluids, the economic performance enhancement of the organic Rankine cycle system is obtained for recovering waste heat from engine. The zero ozone-depletion-potential and dry working fluids of R236fa, R245fa, and R1336mzz(Z) are selected as the components of multicomponent mixtures in the system. The net power output, heat transfer calculation, and apparatus cost evaluation are employed to evaluate the power cost of the organic Rankine cycle system. Parameters of temperatures of waste heat sources and efficiencies of expanders are taken into account. The comparisons of economic performances for single-component working fluid and multicomponent mixtures with optimum mass fractions are proposed. The results show that R245fa, having a levelized cost of energy, LCOE, of 8.75 × 10⁻² $/kW-h, performs the best for single-component working fluids, better than R236fa by 1.6% and R1336mzz(Z) by 8.3%. All the two-component mixtures are superior to their single-component working fluids in economic performance. Among the three two-component mixture working fluids, R1336mzz(Z)/R236fa has the lowest LCOE_min, 8.57 × 10⁻² $/kW-h, followed by R236fa/R245fa and R245fa/R1336mzz(Z). In addition, R236fa/R245fa/R1336mzz(Z) mixture, which has a LCOE_min of 8.47 × 10⁻² $/kW-h, economically outperforms all other working fluids and has a lower LCOE_min than R236fa/R245fa by 1.7% and R245fa/R1336mzz(Z) by 2%.     

Experimental investigation of moderately high temperature water source heat pump with non-azeotropic refrigerant mixtures

Experimental investigations were carried out on non-azeotropic refrigerant mixtures, named M1A (mass fraction of 20%R152a and 80%R245fa), M1B (mass fraction of 37% R152a and 63%R245fa) and M1C (mass fraction of 50%R152a and 50%R245fa), based on a water-to-water heat pump system in the condensing temperature range of 70–90 °C with a cycle temperature lift of 45 °C. Performance of R245fa was tested for comparison. Unfair factors in experimental comparative evaluation research with the same apparatus were identified and corrected. Experimental cycle performance of the mixtures were tested and compared with improved experimental assessment methodology. The results show that all of the mixtures deliver higher discharge temperature, higher heating capacity, higher COP and higher ε_h,c than R245fa. M1B presents the most excellent cycle performance and is recommended as working fluid for moderate/high temperature heat pump.     

Exergy analysis of a novel low-heat recovery organic Rankine cycle (ORC) for combined cooling and power generation

A thermodynamic modification of an ORC integrated with turbine bleeding and regeneration (ORCTBR) is presented. The objective is to modify the ORCTBR for both cooling and power generation (ORCNOV). First, a thermodynamic break down of the components based on exergy was performed followed by a sensitivity analysis. The results indicate that at based conditions the maximum efficiency obtained with ORCNOV was about 52% using R245fa at a heat input of 252 kW. The improvement in efficiency was estimated at 7.2% when compared with ORCTBR. The highest cooling rate was achieved using R1234yf, R245fa, and R1234ze by 11.14, 10.60, and 10.11 kW, respectively. Additionally, the ORCNOV showed improved performance in turbine output power of approximately 2%. However, the sensitivity studies show that the exergy destruction gap was not greater than 45% between the ORCTBR and ORCNOV, and high cooling rates are feasible at increased condenser (1) pressure.     

采用不同工质的高温复合热泵开水器特性研究

热泵开水器具有较高的能源利用效率,是公共场所电加热开水装置的理想替代品。从提高能源效率和一机两用的角度,构建了一种高温复合热泵开水器系统。建立了系统热力学模型,选R236fa、R245fa、R365mfc、R245ca、RC318和R236ea等6种较高临界温度的制冷工质,通过能量分析和[火用]分析的方法,探讨了不同制冷工质对高温复合热泵开水器系统性能的影响。研究结果表明:R245fa作为工质的高温复合热泵开水器系统具有最佳的性能,而以RC318作为工质的系统性能最差。在给定工况下,R245fa作为工质系统制热性能系数(COP_h)为2.47,而其制冷性能系数(COP_c)为3.37,[火用]损失和[火用]效率分别为9.47 kW和49.07%;与R245fa相比,RC318作为工质系统的总能耗增加了39.53%。     

Experimental study on a small‐scale pumpless organic Rankine cycle with R1233zd(E) as working fluid at low temperature heat source

This paper focuses on the novelty pumpless organic Rankine cycle (ORC) and its choice of working fluids. Based on the selection criteria, the refrigerant of R1233zd(E) is firstly chosen and investigated in the pumpless ORC system. In the system, the feed pump is removed, and the refrigerant flows back and forth between two heat exchangers, which act as the evaporator or condenser, respectively. The impacts of the heating water temperature and loads on the system performance are studied to find out the best operating conditions. The low‐grade heat source is simulated by an electric boiler. The temperature of the heat resource ranges from 80°C to 100°C with the interval of 5°C. The temperature of the cooling water inlet is 10°C and is kept constant. The largest average power output is 127 W under the condition of 100°C heating water with nine loads. Because the cycle efficiency with heating steam temperature of 100°C cannot be determined, the highest energy and exergy efficiencies are 3.5% and 17.1%, respectively, for heating water of 95°C with seven loads. The experimental results show that the energy and exergy efficiencies increase with the increase of the heating temperature. The power and current outputs increase when the loads increase under the condition of the constant heating water temperature, whereas the voltage output decreases meanwhile. The generating time increases when the loads increase. This phenomenon is mainly caused by the increasing evaporating pressure and decreasing condensing pressure when the loads increases.     

风力机直驱蒸汽压缩式热泵系统实验研究

从现有风能直驱式热泵系统存在的突出问题入手,利用软连接管路突破了风能直驱热泵系统硬连接的瓶颈问题,提出新型风力机直驱蒸汽压缩式热泵系统,并对该系统进行了实验研究。实验结果表明,热泵机组制热量随压缩机转速呈近似线性规律,热泵机组COP随转速呈近似指数变化规律,机组存在最佳转速;金属软管阻力损失对制冷剂焓值影响可以忽略,但是对冷凝温度有较显著影响,如需要保证热水温度,则需要提高冷凝压力,相应COP会降低,机组运行稳定,初步证明系统可行。