Performance of a new refrigeration cycle using refrigerant mixture R32/R134a for residential air-conditioner applications

In this paper, a new refrigeration cycle (NRC) using the binary non-azeotropic refrigerant mixture R32/R134a is presented, which can be an alternative refrigeration cycle applied in residential air-conditioner. In the NRC, refrigerant circuit of the evaporator is separated into two branches. Because the non-azeotropic mixture has the characteristic of temperature glide, an important benefit of such configuration is that the Lorentz cycle can be realized. Compared with that of conventional cycle configuration, the new cycle efficiency can be improved. The calculating results show that, in the conventional refrigeration cycle (CRC), the mixture R32/R134a has a close performance to that is obtainable with pure refrigerant R22. However, the mixture R32/R134a in the NRC will result in a better performance. The maximal COP can be improved in a range of 8–9% over that of the CRC, and the volumetric refrigerating capacity can be approximately increased by 9.5%.     

A theoretical study of an innovative ejector enhanced vapor compression heat pump cycle for water heating application

This study presents a novel vapor compression heat pump cycle in which an ejector associated with a subcooler is applied to enhance the heating performance for air-source heat pump water heater application. The heating coefficient of performance (COP_h) and heating capacity of the novel cycle using the non-azeotropic mixture refrigerant R417A are theoretically investigated, for the ranges of evaporating temperature (−15 to 10 °C) and condensing temperature (55-60 °C). The theoretical results show that the COP_h and volumetric heating capacity of the novel cycle are better than that of the conventional heat pump cycle. It is found that for the operating conditions considered, the maximum COP_h and volumetric heating capacity can be improved by up to 1.62-6.92% and 15.20-37.32% over the conventional heat pump cycle, respectively. The performance characteristics of the novel cycle show its promise in air-source heat pump water heater applications.     

Combined air conditioning and tap water heating plant using CO2 as refrigerant

A combined air conditioning and tap water heating plant using carbon dioxide (CO₂) as refrigerant has been investigated theoretically and experimentally. The system is suitable for countries with year around cooling demand, such as Indonesia or Singapore, and a need for hot tap water. A unique CO₂ transcritical cycle characteristic for heating process can afford an improvement to a CO₂ air conditioning system when rejected heat from the system is recovered. Some parameters affecting performance of the combined system are discussed.     

CO2跨临界水源热泵两级供热系统理论比较

在供热系统中，需要的水温较高时，由于回水温度高而导致CO2跨临界水源热泵能效比下降。如果降低回不温度，就要求不同温度的热水分级处理。CO2跨临界水源热泵两级供热系统可以实现能量的分级利用。分析对比了3种形工的CO2跨临界水源热泵两级供热系统，发现它们各有特点，可根据不同的使用要求采用适宜的两组系统。     

带膨胀机CO2跨临界热泵系统运行特性

建立了带膨胀机CO2跨临界热泵系统的数学模型,将模拟计算结果与实验测量结果进行了比较,验证了模型的准确性。利用数学模型分析了冷却水进口温度和质量流量、冷冻水进口温度和质量流量对带膨胀机CO2跨临界热泵系统的制冷性能系数及最佳高压侧压力的影响。降低冷却水进口温度和提高其质量流量不仅有利于提高制冷性能系数,而且能降低最佳高压侧压力。提高冷冻水进口温度及质量流量有利于提高制冷性能系数,对最佳高压侧压力影响不大。     

替换R290的热泵型空调器供暖实验研究

为探讨热泵型空调器更换R290后的供暖特性,在重庆地区开展了供暖工况下充注R290空调器与原R22空调器的对比实验,测试了空调器的送回风温湿度、耗电量、风量等数据。研究了两组空调器的送回风温湿度差异及与室外温度变化的关系,比较了2台空调供热量、耗电功率及COP等数据。结果表明:在重庆地区热泵型空调中替代充注R290后,空调器制热效果良好,室内空气温湿度与原空调器处理的空气温湿度较为接近;但由于制冷剂质量流量减小,平均供热量降低14.6%;尽管COP整体降低了7.5%,但在运行稳定后COP能接近原空调器。     

R32用于喷气增焓热泵热水器中可行性研究

理论分析了R32作为空气源热泵热水器制冷剂的可行性,并设计搭建带有喷气增焓装置的实验系统,分别充注R32和R410A制冷剂进行性能对比测试。实验结果表明:对于本实验系统R410A的最佳充注量为1.4 kg,R32的最佳充注量比R410A减少约25%,且名义工况下R32热泵系统的COP要高出R410A热泵系统约4.2%;低温工况下,采用双级压缩系统的压缩比最高在3左右,有效缓解了常规热泵系统低温工况下压缩比过高的问题;低温工况下,R32热泵系统的COP明显高于R410A热泵系统。     

二元混合制冷剂气相pVTx性质测量

主要运用了Burnett法原理搭建了高精度PVT实验台,对新型环保混合制冷剂R290/R1234ze(E)进行了热物性测试。实验中控制温度为260.15~320.15K,测定了质量分数分别为80%/20%和75%/25%混合制冷剂R290/R1234ze(E)的PVT性质。实验装置的压力不确定度为±1 k Pa,温度不确定度为±10 m K,所测实验数据的相对误差都在1%之内。拟合出了相应温度与压力下该混合工质的密度与气体维里方程,为R290/R1234ze(E)作为新型替代制冷剂提供依据。     

Performance characteristics of a two-stage transcritical N2O refrigeration cycle with vortex tube

ABSTRACT

The thermodynamic analysis has been presented in this article using nitrous oxide as the refrigerant in a two-stage transcritical cycle with the vortex tube (TSTCVT) instead of the expansion valve and its results are compared with the two-stage transcritical cycle with the expansion valve (TSTCEV). The evaporator and the gas cooler temperature ranges in both the cycles have been considered between ?55°C to 5°C and 35°C to 60°C for the analysis. Gas cooler and intercooler pressures are simultaneously optimised to obtain the maximum cooling coefficient of performance (COP). The COP of the TSTCVT improves by 1.97–27.19% in comparison to TSTCEV. A decrease in evaporator temperature and an increase in gas cooler exit temperature reduce the COP of TSTCVT. The comparison of refrigerants N₂O and CO₂ in TSTCVT shows that N₂O exhibits higher cooling COP, higher second law of efficiency and lower optimum gas cooler pressure under the considered operating conditions.     

Use of nanoparticles to make mineral oil lubricants feasible for use in a residential air conditioner employing hydro-fluorocarbons refrigerants

The application of nano-fluids in refrigerating systems is considered to be a potential way to improve the energy efficiency and reliability of HVAC&R facilities and to make economic the use of environment-friendly refrigerants. In this paper, we report a method that uses nanoparticles to enhance the energy efficiency of retrofitted residential air conditioners (RAC) employing HFCs as alternative refrigerants. The reliability and performance of RAC with nanoparticles in the working fluid have been investigated experimentally. A new mineral-based nano-refrigeration oil (MNRO), formed by blending some nanoparticles (NiFe₂O₄) into naphthene based oil B32, was employed in the RAC using R410a as refrigerant. A method showing how to disperse the NiFe₂O₄ nanoparticles in the mineral oil refrigeration lubricants is presented together with an investigation of their stability. The solubilities of the new MNRO in R134a, R407C, R410a and R425a were measured. The performances of the RAC, such as the cooling/heating capacity, the power input and the energy efficiency ratio, were determined. The results indicate that the mixture of R410a/MNRO works normally in the RAC. The cooling/heating EER of the RAC increased about 6% by replacing the Polyol-Easter oil VG 32 lubricant with MNRO.     

制冷剂R290及其混合物燃爆特性与安全性研究

将具有燃爆性制冷剂R290（丙烷）分别与物理抑制剂CO2和化学抑制剂R13I1（三氟碘甲烷）混合,根据混合制冷剂的热物性参数确定R290的占比。实验结果表明：R13I1与R290组成的混合工质可直接替代传统制冷剂,根据所要替代的现有制冷剂的热物性参数可确定配比。用可燃气体/蒸气爆炸试验测试装置测试R290分别与CO2和R13I1混合后的爆炸参数,实验得出CO2和R13I1环境下,二者的体积分数分别为26.5%和6.42%时,R290不再具有燃爆性。同时,针对R290,推导出化学抑制剂最小惰化浓度的预测理论公式。     

Theoretical study of R32 to replace R410A in variable refrigerant flow systems

In recent years, global warming has reached critical levels and this has caused a gradual decrease in the use of refrigerants. In the 1997 Kyoto Conference, it was announced that after 2011, use of refrigerants which have higher global warming potential (GWP) of 150 will be restricted. Hence, it was foreseen that R410A, with a GWP of 2088, which has been used in residential heating, ventilating and air conditioning systems, will be prohibited in the near future. This study investigates the thermodynamic performance using R32, which is a potential alternative because of its low GWP, and R410A in variable refrigerant flow (VRF) systems. As a result of theoretical analysis, it was observed that the coefficient of performance of R32 is 5% higher in heating mode and 6% higher in cooling mode than that of R410A. Considering all of this, it was confirmed that R32 can be used in VRF systems as a replacement for R410A in terms of performance.     

新型环保制冷剂R1234ze/R600a PVTx性质

在Burnett原理基础上搭建了高精度PVT实验台,对新型环保混合制冷剂R1234ze/R600a进行了热物性测试。在温度范围为280.15~330.15 K时,测量了质量分数为80%/20%和75%/25%的R1234ze/R600a混合制冷剂的PVT性质,同时拟合出了相应温度与压力下该混合工质的密度与气体维里方程,为进一步研究该混合制冷剂作为新型替代制冷剂的性能提供了热物性参数。     

Modelling and simulation of a heat pump for simultaneous heating and cooling

The heat pump for simultaneous heating and cooling (HPS) carries out space heating, space cooling and hot water production for small office and residential buildings. It works under heating, cooling and simultaneous modes to produce hot and chilled water according to the thermal demand of the building. A subcooler connected to a water tank is placed after the condenser to recover some energy by subcooling of the refrigerant during a heating mode. The water loop at a higher temperature than ambient air is used subsequently as a source for a water evaporator. Average winter performance is improved compared to a standard reversible heat pump (HP). The air evaporator is defrosted by a two-phase thermosiphon without stopping the heat production. The operation of the HPS is modelled using TRNSYS software. The model is validated using results of an experimental study carried out on a HPS prototype working with R407C. Annual simulations of the HPS coupled to a hotel are run in order to evaluate annual performance and energy consumption of the system. The results are compared to the ones of a standard reversible HP. Depending on the scenario, savings in electric energy consumption and annual performance improvement can reach respectively 55% and 19%.     

同时供冷供热的双级压缩制冷热泵循环性能研究

本文提出了一种双级压缩制冷热泵循环,它能够实现冷热量的同时独立调节.通过实际案例,理论分析了不同制冷剂质量流量分配率、环境温度、热水温度以及过冷与过热度工况下新循环的性能,并考察了特征温度的影响因素.     

变频准二级压缩空气源热泵的低温性能优化实验研究

为了提高空气源热泵的低温适应性,采用共沸工质R410a、变频压缩机和带经济器的补气增焓技术,通过在焓差实验室不同环境温度、不同频率、不同进水温度下运行特点实验验证新型热泵在大负荷和低气温条件下可靠运行,得出机组运行性能曲线并分析原因,为低温型热泵在华北乃至东北市场广泛应用带来积极作用。     

环保型空调器的研究与试验

选择对臭氧层无破坏作用的Ｒ３２／Ｒ１３４ａ混合工质作为家用空调器工质Ｒ２２的替代物，对其与润滑油的相溶性，可燃性等进行了实验研究，并对使用这种工质的压缩机，空调器进行了实验。     

Performance analysis of a transcritical N2O refrigeration cycle with vortex tube

In the present study, vortex tube is used in transcritical vapour compression cycle as expansion device to improve the coefficient of performance (COP). The thermodynamic analysis has been performed using nitrous oxide in transcritical cycle with vortex tube (TCVT) and its results are compared with those of a transcritical cycle with expansion valve (TCEV). The evaporator and the gas cooler temperatures have been varied between ?55°C and 5°C and between 35°C and 60°C, respectively, for the analysis. The COP of the TCVT improves by 1.72–27.01% compared to TCEV. A decrease in evaporator temperature and an increase in gas cooler exit temperature result in a decrease in COP. The increase in cold mass fraction brings a negligible increase in maximum COP. The performance comparison of N₂O and CO₂ in TCVT shows that maximum cooling COP for N₂O is higher than for CO₂, but the optimum pressure required for N₂O is lower than for CO₂.     

CO_2跨临界水——水热泵循环系统的实验研究

在作者设计和建立的实验台上进行了CO2 跨临界水—水热泵多种工况的循环性能实验研究 ,系统运行稳定、调节方便。实验结果表明 ,系统运行时的最大制冷 (热 )系数取决于系统的蒸发温度和气体冷却器出口温度。CO2 跨临界循环热泵较之传统工质热泵具有较大优势 ,尤其是在高温热泵领域。指出了系统的改善措施     

Economy of exploiting heat from low-temperature geothermal sources using a heat pump

The article describes the economy of exploiting heat from low-temperature geothermal sources for high-temperature heating of buildings using a heat pump. For the exploitation of low-temperature geothermal sources, a two stage heat pump with a heat exchanger was planned. The pump consists of two single stage heat pumps which use different refrigerants at each stage. At stage 1, the calculation of the heat pump is conducted with refrigerant R407c; at stage 2 of the heat pump, the refrigerant R600a is used. The main operational characteristics of a two stage heat pump are presented in the form of diagrams. For the exploitation of heat from geothermal water with a temperature of 45 °C, a profitability evaluation of the investment in the heat pump was carried out, using the method of the net present value. In the research, also the coefficient of profitability and the period of time in which the investment is going to return itself were established.