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…     

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.     

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.     

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。     

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.     

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。     

太阳能低温储粮吸附制冷系统

低温储粮是一种具有广阔应用前景及实用价值的科学储粮方法。从降低能耗的角度出发,设计并建造了一种用于低温储粮的太阳能吸附制冷系统,测试分析了系统的热性能。试验测试结果表明：通过合理配置集热器面积,太阳能制冷系统能够满足低温储粮对冷负荷的需求。     

Heat exchanger design effect on the system performance of silica gel adsorption refrigeration systems

This article presents a numerical investigation of the heat exchanger design effect on the performance of closed cycle, two-bed adsorption cooling systems with silica gel as adsorbent and water as refrigerant. It is well known that the shorter the cycle time, lower is the performance (cooling capacity and coefficient of performance). A long cycle time is responsible for lower cooling capacity. In this study, a non-dimensional switching frequency, which is inversely proportional to the cycle time, is defined and an optimum switching frequency is derived based on parametric analysis. The effect of other heat exchanger design parameters such as adsorbent number of transfer unit (NTU), bed Biot number (Bi), the heat exchanger aspect ratio (Ar) and the ratio of fluid channel radius to the adsorbent thickness (Hr), on the system performance has been investigated. The results show that the switching frequency ω, bed NTU, Ar and bed Bi have strong effects on the system performance. It is also seen that for a given set of design parameters, the system has an optimum switching frequency and the system performance will be declined seriously if the system is not operated at optimum switching frequency. The optimum switching frequency increases with the increase of NTU, Hr and with the decrease of Bi and Ar.     

A review on adsorption working pairs for refrigeration

Solid sorption refrigeration is a type of environmental benign and energy saving technology and the sorbents utilized can be divided into physical, chemical and composite sorbents, according to the nature of the forces involved in the adsorption process. The types, characteristics, advantages and disadvantages of different adsorbents, refrigerants and working pairs are summarized in this paper, together with the models that describe the adsorption equilibrium. Moreover, some of the procedures to prepare composite adsorbents are presented. The application of different working pairs for different situations is related with the adsorption heat, the adaptability to the driving temperature and to the desired working pressure. The methods to measure the adsorption quantity of different working pairs are compared, and future research directions of adsorption working pairs are also analyzed.     

The steady-state modeling and optimization of a refrigeration system for high heat flux removal

Steady-state modeling and optimization of a refrigeration system for high heat flux removal, such as electronics cooling, is studied. The refrigeration cycle proposed consists of multiple evaporators, liquid accumulator, compressor, condenser and expansion valves. To obtain more efficient heat transfer and higher critical heat flux (CHF), the evaporators operate with two-phase flow only. This unique operating condition necessitates the inclusion of a liquid accumulator with integrated heater for the safe operation of the compressor. Due to the projected incorporation of microchannels into the system to enhance the heat transfer in heat sinks, the momentum balance equation, rarely seen in previous vapor compression cycle heat exchangers modeling efforts, is utilized in addition to the mass and energy balance equations to capture the expected significant microchannel pressure drop witnessed in previous experimental investigations. Using the steady-state model developed, a parametric study is performed to study the effect of various external inputs on the system performance. The Pareto optimization is applied to find the optimal system operating conditions for given heat loads such that the system coefficient of performance (COP) is optimized while satisfying the CHF and other system operation constraints. Initial validation efforts show the good agreement between the experimental data and model predictions.     

太阳能吸附式制冷关键技术的研究

介绍了太阳能吸附式制冷技术,指出了其存在的问题,并对太阳能吸附式制冷的关键技术的研究现状进行深入的分析和探讨,进一步明确其研究方向.     

Les fuites thermiques en refrigeration solaire (thermal losses in solar refrigeration)

We show how the thermal losses determine the functioning of a solar refrigerator. After recalling preceding studies we define the parameters involved in an actual refrigeration and describe experiments carried out on a CaCl₂NH₃ solid absorption couple. In order to calculate the losses, the sample to be cooled is a measured weight of water, the amount of which, compared with the water-value of the evaporator, modifies the thermal losses and the efficiency of the apparatus. The intermittence of the frigorigene regeneration phases requires optimisation of the apparatus so as to adapt it for possible use in tropical zones.     

Design and performance simulation of a new solar continuous solid adsorption refrigeration and heating hybrid system

In this paper, the design of a new continuous solid adsorption refrigeration and heating hybrid system driven by solar energy was proposed, and its performance simulation and analysis were made under the normal working conditions. Some performance parameters of the system were obtained, and the effects of water mass in water tank on the system's COP_cooling, COP_heating etc. were discussed. The simulation indicated: the system could refrigerate continuously with such a design, and at the conditions of that the daily sun-radiation is 21.6 MJ, the mean ambient temperature is 29.9°C, the evaporating temperature is 5°C, the heat-collecting coefficient of upper bed η is 60%, and the heat-transfer coefficient between lower bed and ambient α is 2 W/m² K, by day a hybrid system of single combined bed could furnish 30 kg hot water of 47.8°C, and had a mean COP_cooling of 0.18, a mean COP_heating of 0.34, a continuous mean SCP_a of 17.6 W/kg, a continuous mean SCP_c of 87.8 W/m², and a continuous mean SHP_c of 165.9 W/m²; and at night it had a cooling capacity of 0.26 MJ/kg of adsorbent, and a cooling capacity of 1.3 MJ/m² of heat-collecting area.     

吸附式制冷在余热利用中的应用

简要介绍了现有的余热资源，列举了一些吸附式制冷在余热利用中的应用实例，指出吸附式制冷在余热利用中具有可观的市场价值和巨大的发展潜力。     

Modelling and performance study of a continuous adsorption refrigeration system driven by parabolic trough solar collector

This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP_cycle) and solar coefficient of performance (COP_s), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed.The study has put in evidence the ability of such a system to achieve a promising performance and to overcome the intermittence of the adsorption refrigeration systems driven by solar energy. Under the climatic conditions of daily solar radiation being about 14 MJ per 0.8 m² (17.5 MJ/m²) and operating conditions of evaporating temperature, T_ev = 0 °C, condensing temperature, T_con = 30 °C and heat source temperature of 100 °C, the results indicate that the system could achieve a SCP of the order of 104 W/kg, a refrigeration cycle COP of 0.43, and it could produce a daily useful cooling of 2515 kJ per 0.8 m² of collector area, while its gross solar COP could reach 0.18.