Optimisation of electronic device coupled LiBr–H2O absorption heat pump system working at ambient temperature using Taguchi approach

The study attempts to optimise the parameters of a lithium bromide–water (LiBr–H₂O) miniature absorption refrigeration system using Taguchi approach for electronic cooling working at ambient conditions. Thermodynamic optimisation was performed to obtain the optimum coefficient of performance (COP) for heat removal of 100?W by using the Taguchi approach. Three factors were considered: generator temperature (T_g), condenser temperature (T_c) and absorber temperature (T_a), at three different levels. The result showed that the percentage contribution of generator temperature is more on COP. Optimisation of three significant heat exchangers: evaporator, condenser and absorber, was performed by using the Taguchi approach. The study was carried out individually for all the components by varying the hydraulic diameter and aspect ratio at three different levels. The results showed that the hydraulic diameter contributes more than the aspect ratio.     

电压缩式制冷循环与吸收式制冷循环的热力学比较分析

采用效率与损失分析方法,计算比较了电压缩式制冷循环与单效吸收式制冷循环的效率及两种制冷循环在典型工况下各环节的损失。结果表明,当采用合适的发生器温度和热源温度时,两种制冷循环的效率基本相同;电压缩式制冷循环的主要损失发生在压缩机环节,吸收式制冷循环的主要损失发生在吸收器和发生器。讨论了两种制冷循环的改进途径。     

Einstein单压制冷系统热力学性能对比分析

介绍了Einstein单压吸收式制冷循环的工作原理,对国内两种有代表性的改进型Einstein制冷系统(Ⅰ ,Ⅱ)进行了对比。运用质量、能量守恒定理,建立了系统各部件的热力学模型,并对其性能进行了分析。结果表明:相同工况下,系统Ⅱ的COP较高,达到0.255 1。工况的变化并不能有效改善二者的COP,而通过合理匹配系统各部件,优化管道阻力,采用热回收系统及高效气泡泵,以及选择最佳的发生温度,能够有效改善系统制冷性能。详尽研究内容对Einstein制冷循环系统的性能优化及工业应用具有指导意义。     

Internal irreversibilities’ influence on the new thermo-ecological criterion for real absorption refrigerators

Irreversibility is classified in two main types: internal and external irreversibilities. Internal irreversibility is due to turbulence, pressure gradients, mixing and diffusion processes within the system, which is represented by two irreversibility parameters indicating the deviation from an endoreversible case. This paper studies and analyses the effects of two internal irreversibility parameters (the internal irreversibility parameter for generator–absorber assembly and the internal irreversibility parameter for condenser–evaporator assembly) on the optimal ecological performances of an irreversible four-heat-source absorption refrigerator based on the ecological coefficient of performance (ECOP) criterion. The ECOP objective function is defined as the ratio of the cooling load to the loss rate of availability (or entropy generation rate). The results obtained show that the internal irreversibility parameter for condenser–evaporator assembly affects more the ecological performance of the system than the internal irreversibility parameter for generator–absorber assembly. This is of importance to the optimal design and performance improvement of absorption refrigeration cycles.     

提高绝热吸收器压力的风冷技术分析

吸收器是吸收式制冷机的关键部分,传统吸收器基本采用水冷却。本文在传热传质分离技术的基础上,通过热力学理论分析,提出提高绝热吸收器压力的方法,建立了制冷系统仿真模型,并通过模型的求解,分析了提高绝热吸收器压力对实现吸收式风冷技术的有效性。研究结果表明,在溶液浓度不变甚至有所降低的情况下,提高绝热吸收器的压力,可显著提高风冷冷却器的传热温差,有效降低系统再循环倍率,且系统对外界空气温度敏感度较低,从而能很好地实现风冷技术。     

Energy analysis of single-stage LiBr–water vapour absorption refrigeration system using artificial neural network approach

In this study, artificial neural network (ANN) has been used as a new approach for carrying out the energy analysis of a single-stage absorption refrigeration cycle with water–lithium bromide as the working fluid pair. Energy analysis of an absorption system is a very complicated process mainly because of the limited experimental data and analytical functions required for calculating the thermodynamic properties of fluid pairs, which usually involves the solution of complex differential equations. Instead of complex differential equation and limited experimental data, faster and simpler solutions were obtained by using equations derived from the ANN model. As seen from the results obtained, the calculated thermodynamic properties are within acceptable results. Thermodynamic properties of each point in the cycle are calculated using related equations of the state. Heat flow rate of each component in the cycle and some performance parameters are calculated from the first law analysis. The results show that a high coefficient of performance value is obtained at high generator and evaporator temperatures and also at low condenser and absorber temperatures.     

蒸气压缩式和溴化锂吸收式制冷系统能量经济性比较

利用能量分析和经济分析相结合的方法，对蒸气压缩式和溴化锂吸收式制冷系统进行了分析比较。结果表明，蒸气压缩式制冷系统的一次能源能效比普遍高于溴化锂吸收式制冷系统，直燃型溴化锂吸收式制冷系统的单位冷量成本较其它系统相对要高。     

Improvement of solar-electric compression refrigeration system through ejector-assisted vapour compression chiller for space conditioning in subtropical climate

In this study, improvement was made for the solar-electric compression refrigeration system by incorporating the ejector design to a conventional vapour compression chiller within the system. Through year-round dynamic simulation, the performances of the ejector-assisted vapour compression chiller (EAVCC) were evaluated under the intermittent and changing supply of solar energy in the subtropical climate. In addition, the effect of three common refrigerants, R22, R134a and R410A on the EAVCC was assessed and compared. It was found that the coefficient of performance of the chiller was increased and the total primary energy consumption of the system was decreased for all the three refrigerants, in which the degree of enhancement from R134a was the most significant. It was also noted that the effect of R410A on EAVCC was not apparent, and the overall system energy improvement was marginal. With appropriate ejector design and refrigerant selection of the solar-electric compression refrigeration system, the reduction potential of year-round primary energy consumption could be more than 5%. This would be certainly helpful in promoting the application of solar air-conditioning for building use in the subtropical climate.     

吸收器传热传质强化的研究综述

本文综述了国内外溴化锂吸收式制冷机吸收过程强化传热传质的有关研究现状。强化方法主要包括改进传热管、添加表面活性剂、改进吸收式制冷系统等,如改进传热管以增大传热吸收面积和吸收液的扰动;加入表面活性剂,以强化Marangoni(马拉格尼对流)效应;改进吸收式制冷系统以增大制冷剂的质量流量,并增大吸收器内的吸收推动力。     

变温热源不可逆制冷机分析

利用有限时间热力学分析了变温热源制冷循环性能，计入了工质与高低温侧换热器的热阻损失，热源之间的热漏损失及工质内部耗散的不可逆损失。在给定制冷率条件下，推导出最大性能系数和高低温侧循环工质温度的解析式，通过数值计算，分析了各不可逆损失对循环性能的影响。     

Operation costs exergoeconomic of transcritical refrigeration cycle with carbon dioxide

ABSTRACT

In this work, the thermodynamic and exergoeconomic studies are performed to a single vapour compression refrigeration cycle which uses CO₂ as a refrigerant in transcritical conditions. This analysis establishes the behaviour of the compressor discharge pressure based on the gas cooler temperature, when it is operating at ambient conditions greater than 20°C. The effect of varying the cooling chamber temperature is also shown. In the analysis, the coefficient of performance (COP), exergetic efficiency and exergoeconomic operation costs for each equipment are obtained, considering a refrigeration capacity of 5 TR. For instance, at a gas cooler temperature of 45°C and a cooling chamber temperature of ?5°C, the maximum COP is 1.78 to a gas cooler pressure of 120 bar and the exergetic efficiency is 0.1556; however, operating at these conditions, it generates an exergoeconomic operation cost of 1.74?€?h^?1.     

天然气总能系统制冷性能及成本分析

探讨了天然气总能系统(IES)制冷方式和利用尾气余热为吸收制冷提供热量的方法。对电机驱动压缩制冷，天然气直燃吸收制冷，燃气发动机驱动压缩制冷，燃气轮机发电和吸收制冷系统的一次能源利用率和装置成本进行了比较分析。     

Integration of trigeneration in an indirect cascade refrigeration system in supermarkets

This article presents an energy and economic analysis of a trigeneration configuration for supermarket applications. The energy system in a supermarket is relatively complex, because it includes lighting, air conditioning, cabinets, refrigeration system, etc. A trigeneration system could be used to simultaneously satisfy heating, refrigeration and electricity demands in supermarkets. More specifically, this article studies the integration of a trigeneration system and an indirect refrigeration cascade compression system in a supermarket in Barcelona. The trigeneration system consists of a cogeneration engine and an ammonia/water absorption chiller unit. The results of simulating energy usage, life cycle costs and CO₂ emissions have been compared with a conventional indirect refrigeration cascade compression system for the supermarket studied. Several trigeneration configurations have been studied. They all show a payback time of less than 6 years but the profitability of the investment depends strongly on the ratio between the prices of natural gas and electricity. This study shows that this novel trigeneration system is economically feasible and environmentally more viable than conventional supermarket systems.     

压缩-喷射二级制冷系统热性能系数的研究

介绍了压缩喷射二级制冷系统的结构,比较了喷射制冷、压缩喷射二级制冷、压缩制冷系统的热性能系数,结果表明压缩喷射二级制冷系统的热性能系数大于喷射制冷系统,在低焓能领域有应用前景。     

有辅助能源的太阳能吸收式制冷循环模式

为了扩大太阳能吸收式制冷系统的适用范围,必须对不连续、不稳定的太阳辐射进行能量补偿。从功量补偿角度出发,提出基于太阳能吸收式制冷与蒸气压缩制冷的联合制冷系统。从工作原理上分析了联合制冷系统的联合制冷循环模式的可行性,它可根据太阳辐射的强弱在蒸气压缩制冷与吸收式制冷之间切换和组合,使太阳能吸收式制冷系统的适用性大大增强。     

120～150℃热水用于双效吸收制冷循环热力分析

针对集中供热热水用于溴化锂吸收式制冷时的温度不匹配问题,提出在双效并联循环中增加一个加压装置的办法,通过补偿一部分电能以扩大双效循环对热源温度的适用范围,从而使得双效溴化锂吸收式制冷可以使用集中供热一次热源作为驱动能源。经过分析,加压装置安装在蒸发器与吸收器之间效果最好,但安装在高发与低发之间蒸汽压缩量最少。     

Magnetic refrigeration: a promising new technology for energy saving

Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magnetocaloric effect. The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative refrigeration). In this paper, attention is directed towards the near-room-temperature range. We compare the energetic performance of a commercial R134a refrigeration plant to that of a magnetic refrigerator working with an AMR cycle. The comparison is carried out by means of a mathematical model. In these simulations, we consider different solid magnetic refrigerants, namely, Gd, Gd_0.95Dy_0.05, Gd_0.9Tb_0.1,Gd₅Si₂Ge₂, MnAs_0.9Sb_0.1, and MnAs_0.95Sb_0.05. We compared two different geometries of the regenerator: a porous medium and a flat plate. In the former, the Coefficient of Performance (COP) of the AMR cycle is better than that of the vapour compression plant only in the low mass flow-rate range. Whereas in a flat plate regenerator, the COP of the AMR cycle is better than that of the vapour compression plant only in the high mass flow-rate range.     

Advancement of solar desiccant cooling system for building use in subtropical Hong Kong

The solar desiccant cooling system (SDCS) had a saving potential of the year-round primary energy consumption as compared to the conventional air-conditioning system for full fresh air application in the subtropical Hong Kong. In order to further enhance its energy efficiency, advancement of the basic SDCS was carried out through a strategy of hybrid design. Six hybrid system alternatives of SDCS were therefore proposed, three for full fresh air design while another three for return air design for the building zone. Year-round performance evaluation of each solar hybrid desiccant cooling system was conducted for typical office application under different climatic and loading conditions. All the six hybrid system alternatives were found technically feasible, with up to 35.2% saving of year-round primary energy consumption against the conventional air-conditioning systems. Among the hybrid alternatives, recommendations were made on the SDCS hybridized with vapour compression refrigeration for full fresh air design; and the SDCS hybridized with vapour absorption refrigeration for return air design, since they had the saving potentials of both primary energy and initial cost. These two hybrid system alternatives used evacuated tubes, a more economical type of solar collectors compared to the PV or PVT panels.     

Optimisation of process parameters for electroless nickel plating on SS316L for refrigeration systems

Nowadays, refrigeration systems are important for industrial and domestic applications. The coefficient of performance of a vapour compression refrigeration system can be improved if a reduction in the work of compression can be achieved by a suitable technique for a specified heat removal rate. The present study investigates the effect of material coating of electroless nickel (EN) plating. The friction and wear experiments were performed using a four-ball machine tribo tester. Controlling the EN plating parameters plays an important role in the quality of coating. It depends on the wear scar rate of the coated material. So it is necessary to optimise the process parameters of EN plating. The experimental studies have been conducted under varying pressure, load and time on quality characteristics. In this paper, optimisation of process parameters using response surface methodology technique for EN plating was discussed.     

以风力驱动的热泵空调系统

本文介绍了风力制热以及风力驱动的压缩式、吸收式与机动车热泵空调系统,重点分析了风力制热,以风电、蓄电池和市电并联共同驱动的压缩式热泵空调装置和风力驱动的吸收式制冷(热泵)机组,分析了风力热泵的节能环保性能。