Solar process heat generation using an ETC collector field with external parabolic circle concentrator (PCC) to operate an adsorption refrigeration system

The design and construction of a collector system for process heat generation up to 150°C is described. The thermal energy is used to operate an ammonia/carbon ice maker generating block-ice for the fishing industry in developing countries.Various analytical and experimental investigations have shown that with operational temperatures beyond 100°C concentrators like CPCs (Winston, 1974; Winston and Hinterberger, 1976; Rabl, 1976; Winston and Welford, 1978) or similar ones improve substantially the efficiencies of evacuated tubular collectors (ETC). We developed and investigated a shape consisting of segments of parabolas and circles, respectively, because of the far easier manufacturing (Schreitmüller et al., 1991; Niemann, 1992; Niemann and Schreitmüller, 1993). The envisaged collector held consists of evacuated tubular collectors with external parabolic circle concentrators (PCC). The non-tracking PCC-collector with a concentration ratio of 5 is mounted in an east-west direction.The ammonia carbon adsorption ice maker was developed by the University of Warwick, Department of Engineering, Coventry, U.K. (Critoph and Gong, 1992). This unit is a rapid cycling refrigerator, producing 500 kg ice per day, in which two complete adsorption systems operate out of phase. This means one is heated whilst the other is cooled, resulting in a semi-continuous refrigeration process.     

太阳能制冷技术

夏季太阳辐射强天气炎热，人们渴望利用太阳能资源来制冷空调，下面介绍几种常用的太阳能制冷系统以飨读者。１物态变化过程中的能量转移物质在物态变化时能吸收或放出大量的热量。例如在一个标准大气压下，纯净水在１００℃开始沸腾，如果继续加热，水吸收热量后保持温度不变，水将由液态变为１００℃的水蒸汽（气态），在此条件下每千克水可吸收热量２．２５７MJ。相反的过程，１００℃的水蒸汽（气态）放出２．２５７MJ的热量后，就会变成１千克１００℃的水（液态）。这一热量称为汽化潜热。不同物质的汽化潜热是各不相同的。２液体吸…     

Solar powered cogeneration system for air conditioning and refrigeration

By employing the energetic optimization technique, the optimal performance of a focusing collector-driven, an irreversible Carnot cogeneration system for air conditioning and refrigeration is investigated. A minimum value for the total solar insolation needed to overcome internal irreversibilities for start-up of the system is defined and the effect of the collector design parameters on this value is investigated.     

Thermal design of parabolic solar concentrator adsorption refrigeration system

This study presents a thermal design of solar-powered adsorption refrigeration with the type of activated carbon-methanol pair. The designed module consists of an evacuated glass tube equipped with a parabolic solar concentrator as generator, sorption bed, evaporator, and condenser units. A thermodynamic design procedure and a mathematical model of a steady state system with activated carbon refrigerator have been developed. The adsorber is heated by solar energy collected by a parabolic solar concentrator. The temperature of the working pair in the adsorber, the amount of methanol leaving and reabsorb bed, and the refrigerated box was estimated. An optimize design of the system to achieve higher cycle COP was presented. Maximum cycle COP = 0.576 and COP_net = 0.375 with T _max reached 157.8°C, T _B = 57.5°C, M _ac = 0.907 kg, and the concentration of methanoldesorped equal to 0.206 kg/kg _ac .     

Solar refrigeration and cooling

In this paper a review of solar cooling and refrigeration technologies is presented. A discussion on the main reasons why these technologies are not presently economically feasible is carried out. and two installations in Mexico are analysed.     

柴油机余热吸附式制冷系统的动力学实验研究

提出了一种发动机排气余热驱动的以氯化钙－氨为工质对的吸附式制冷机的设计方法，在实际工况下对该系统进行了测试，得出了系统的工作特性曲线，并采用吸附制冷单管实验台，对制冷系统单元吸附床在解吸和吸附过程中的传热传质特性进行了研究，结果表明，在恒定蒸发压力下，制冷能力随进入发生器的热流变化，吸附床内的传质过程主要受传热过程影响。     

Solar refrigeration for rural applications

A large proportion of people in developing countries live in rural or remote locations where grid electricity is presently unavailable and is not envisaged in the foreseeable future. Since conventional, electrically powered vapour compression refrigeration systems may not be of much use in such areas, for essential applications such as food and drug preservation, alternative refrigeration systems are required. Such systems are presented and discussed in this paper. These include photovoltaic (PV) powered vapour compression systems; continuous and intermittent liquid or solid absorption systems; and adsorption systems. Typical application examples are drawn from recent experiences worldwide. Technical and financial constraints which limit their widespread application are reviewed, and strategies for overcoming them are discussed.     

Experimental investigation and mathematical modelling of a solid adsorption refrigeration system

The objective of this work is to study the thermodynamic mechanism and performance of an engine exhaust-powered adsorption refrigeration system using CaCl₂ as adsorbent and NH₃ as refrigerant. A 6 kW nominal refrigerating capacity adsorption refrigerator was developed. The working performance of the refrigerator is presented. It is concluded that the refrigerating capacity at constant evaporating temperatures varies with the input heat into the generator, and the heat transfer affects strongly the mass transfer in the adsorbent, making it work in different mean generation and adsorption temperatures. A conventional test bed was developed for investigating the properties of CaCl₂–NH₃ adsorption/desorption unit tube. A mathematical model based on non-equilibrium thermodynamics was developed to describe the performances of the adsorption refrigerating system.     

Study on intermittent refrigeration phenomenon for solar solid adsorption refrigeration

A valveless solar solid adsorption ice maker has been used for carrying out experiments under real solar radiation intensity conditions. Different performance variations of the solar ice maker are obtained under the effect of sky cloudy cover. The experimental results indicated that the performance of the solar ice maker was severely affected by the sky cloudy cover, and no ice would be obtained if cloudy conditions prevailed for intervals exceeding 3 h. A heat and mass transfer model validated by the experiments has been used to analyze intermittent refrigeration phenomenon of solar solid adsorption refrigeration. The performance variation due to the effecting of sky cloudy cover has also been demonstrated by simulated results. The analysis of both experimental and simulated results has provided an objective climate resource choice which could be available now in applications to solar solid refrigeration, it also has made a scientific analysis method for solar solid adsorption ice maker application.     

太阳能热泵系统

太阳能与热泵相结合的技术是新能源利用技术发展的一个重要方面。文章介绍了太阳能热泵的基本知识，并结合所做的相关试验分析了太阳能和热泵相结合应用的特点。     

Solar refrigeration in the Egyptian climate

An experimental intermittent solar refrigerator using aqua-ammonia has been manufactured and tested in the Egyptian climate. Tests on this experimental intermittent refrigerator prove that cooling by solar energy using NH₃---H₂O systems is technically feasible in the Egyptian climate without the need of any help from other external sources of energy. The present paper reports data and results obtained from such tests and compares these experimental results with their corresponding theoretical values.     

基于混合吸附剂的解吸温度对吸附式制冷系统性能影响的实验研究

搭建了混合吸附剂吸附性能实验装置和混合吸附剂吸附式制冷系统实验台。通过实验研究,发现当质量比例为10∶3时,4A分子筛和铝条的混合吸附剂获得最佳吸附性能。同时对该混合吸附剂吸附制冷在不同解吸温度下的制冷性能进行了实验研究。结果表明:解吸温度从74.0℃逐渐升高到98.0℃时,蒸发温度随解吸温度的升高而降低,当解吸温度为98.0℃,蒸发温度最低为10.7℃;解吸温度从74.0℃逐渐升高到98.0℃时,系统制冷量与解吸温度成正比关系,解吸温度为98.0℃时,系统制冷效果最好,系统制冷量最大达到305 W。     

Numerical simulation of heat transfer in regenerator of solid adsorption refrigeration system

In this paper a theoretical model of the heat-transfer processes in a solid adsorbent packed bed is established. Based on discretized energy control equations of the fluid in the heat-transfer coil and transient heat conduction equations of the adsorbent in the bed with unsteady boundary conditions, a numerical analysis is made. Through numerical computation, a coupling temperature distribution in the adsorbent and the heat-transfer coil is obtained. This will make for an optimal design of the solid adsorbent packed bed.     

吸附式制冷系统吸附床内非平衡态热力学分析

从非平衡态热力学角度，对以氯化钙—氨为工质对的固体吸附式制冷系统吸附床内传热传质过程进行了分析，建立了吸附床内热质耦合模型，并通过对模型的数值模拟，探讨了解吸／吸附过程中各热力学流之间的作用关系及其对吸附床熵产率的影响。     

A review on adsorption refrigeration technology and adsorption deterioration in physical adsorption systems

As one kind of environmentally friendly refrigeration, the adsorption refrigeration has attracted many attentions in resent decades. This paper introduces the researches of adsorption refrigeration systems with the commonly used working pairs, advanced adsorption cycles, heat and mass transfer enhancement and attempts of adsorption refrigeration applications. Poor heat and mass transfer problem is a bottleneck to prevent the improvements of the adsorption refrigeration technique. Two ways to enhance the heat and mass transfer are discussed in this paper. The adsorption deterioration of adsorbent, another obstacle to physical adsorption refrigeration applications, is also pointed out. And the possible reasons and the possible methods are analyzed.     

Environmentally benign working pairs for adsorption refrigeration

This paper begins from adsorption working pairs: water and ethanol were selected as refrigerants; 13x molecular sieve, silica gel, activated carbon, adsorbent NA and NB, proposed by authors, were selected as adsorbents, and the performance of adsorption working pairs in adsorption refrigeration cycle was studied. The adsorption isotherms of adsorbents (NA and NB) were obtained by high-vacuum gravimetric method. Desorption properties of adsorbents were analyzed and compared by thermal analysis method. The performance of adsorption refrigeration was studied on simulation device of adsorption refrigeration cycle. After presentation of adsorption isotherms, the thermodynamic performance for their use in adsorption refrigeration system was calculated. The results show: (1) the maximum adsorption capacity of water on adsorbent NA reaches 0.7 kg/kg, and the maximum adsorption capacity of ethanol on adsorbent NB is 0.68 kg/kg, which is three times that of ethanol on activated carbon, (2) the refrigeration capacity of NA–water working pair is 922 kJ/kg, the refrigeration capacity of NB–ethanol is 2.4 times that of activated carbon–methanol, (3) as environmental friendly and no public hazard adsorption working pair, NA–H₂O and NB–ethanol can substitute activated carbon–methanol in adsorption refrigeration system using low-grade heat source.     

Silica gel water advanced adsorption refrigeration cycle

We present results of an analytic investigation on the influence of the thermal conductance of sorption elements (adsorber/desorber, evaporator and condenser) on the performance of a silica-gel-water advanced adsorption chiller, with consideration of the thermal capacitance ratio of the adsorbent and metal of the adsorber/desorber heat exchanger. The analysis was performed by using a cycle-simulation model developed by us and a coworker. The chiller is driven by exploiting waste heat at a temperature 50°C with a cooling source at 30°C for air-conditioning and refrigeration purposes. The results show that the cycle performance is strongly affected by the thermal capacitance and adsorber/desorber thermal conductance due to severe sensible heating/cooling requirements resulting from batched cycle operation. The model is somewhat sensitive to the thermal conductance of the evaporator. The thermal conductance of the condenser is the least sensitive parameter, as the adsorption behavior of the adsorbent/adsorbate pair at a fixed temperature is defined for desorption and condensation.     

太阳能固体吸附式制冷技术应用的一些探讨

总结了自行设计的太阳能固体吸附式制冷装置所取得的一些成果,对太阳 能固体吸附式制冰机系统的实际应用从工艺上、操作上、成本上作了分析与说明,并对 进一步开展太阳能固体吸附式制冷装置的研究作出了展望。