Solid Adsorption Refrigeration Research Articles

Dynamic simulation and exergy-economic assessment of solar thermal refrigeration systems in different climates

In this paper, the performance of solar-thermal cooling systems for air conditioning application is investigated in different climates of Iran. Diverse climate types are considered which makes the results applicable to other countries. Available commercial refrigeration cycles that are capable of integration with solar-thermal collector systems including the closed liquid absorption cycle, closed solid adsorption cycle, and desiccant cycle are studied. First, a solar and climatic map is proposed and the representative cities have been selected for each climate. Then, the climate parameters related to each region are extracted to create an hourly database. Also, the cooling load of a reference building is modeled based on the climate database, each refrigeration cycle is simulated using thermodynamic equations, and the dynamic model is generalized daily for the hot season in each city. In the last step, each cooling system is examined using an exergy-economic analysis, and technical and economic indicators are compared. The results show that the most suitable solar-thermal refrigeration cycle that can be installed in the central plateau and semi-arid areas of Iran is the closed-cycle liquid absorption system. The annual average exergy-economic factor and the annual solar fraction in this cycle are 0.7578 and 0.57, respectively. In the southern coastal areas, due to the high humidity and air temperature in summer, the solid desiccant refrigeration system with an exergy-economic factor of 0.6978 and a solar fraction of 0.2416 is preferred. The suitable solar-thermal refrigeration cycle in the cold and mountainous regions of Iran is a solid adsorption system with a silica gel absorber. The annual solar fraction and average annual exergy-economic factor in this cycle are 0.5158 and 0.7394. Also, in northern moderate regions, the solid adsorption refrigeration system with an average annual exergy-economic factor of 0.409 and average exergy efficiency of 0.12 is comparatively beneficial.

Comprehensive Analysis for State-of-the-Art Adsorption Refrigeration Technologies

With the development of science and technology, society needs more and more energy currently, and the energy utilization efficiency has become a topic that cannot be neglected. In many cases, it is still a common phenomenon in society that a large amount of energy is wasted, which may cause more fossil energy to be burned and the greenhouse effect to be strengthened. In addition to directly improving the utilization rate of energy, we can also reduce energy waste through the recovery and reuse of waste energy. Thermal energy sorption refrigeration technology, divided into adsorption refrigeration technology using solid adsorbent and absorption refrigeration technology using liquid absorbent, could utilize waste energy or low-grade heat sources for refrigeration. Through the introduction of adsorption refrigeration technology, the research and analysis of the application of solid adsorption refrigeration technology in industry, vehicles, ships and buildings, this paper introduces the basic principle and current situation of this technology, summarizes the advantages, disadvantages and development direction of adsorption refrigeration technology, and provides reference for those who do not comprehend this technology or have doubts about the scope of its use.

Evaluation of Activated Carbon from Raphia Palm Nut Endocarp as Adsorbent for Solid Adsorption Refrigeration

Activated carbon was produced from powdered Raphia palm nut endocarp (REAC) using H3PO4 and CaCl2 as activators before carbonization, and the responses studied to investigate its suitability for solid adsorption refrigeration applications. Temperature, resident time, concentration, and impregnation ratio, were the parameters used and ash content, carbon yield and surface area were the responses. The effect of preparation sequence was evaluated. The efficiency of the activated carbon on the adsorption of methanol was investigated an experimental rig. 100 g of sample was carbonized at 200, 400 and 600oC, and the carbonized samples were used for solid adsorption refrigeration to determine the optimum carbonization temperature. Carbonization times (30, 60, 90, and 120 minutes), activating agent concentrations (25, 50, 75 and 100%) and impregnation ratios (1:1, 1:2, 1:3, and 1:4 precursor to activating agents) at the optimum temperature were used to determine the optimum resident time, concentration and impregnation ratio. The results revealed that H3PO4 activated samples at optimum conditions of 500˚C temperature, 50% concentration, 60 minutes resident time and 4 ml/g impregnation ratio yielded better response with low percentage of ash content (2.25%), high carbon yield (73.63%) and large surface area (2857.51 m2/g) activated carbon were obtained at the optimum conditions. The adsorbing efficiencies of the carbons prepared through activation with H3PO4 achieved 0.084 and 14.5 of Coefficient of Performance (COP) and Specific Cooling Power (SCP) respectively. The results indicated that the carbon is activation before carbonization is well suited solid adsorption refrigeration applications.

Experimental study of the effect of enhanced mass transfer on the performance improvement of a solar-driven adsorption refrigeration system

The current work demonstrates a novel prototype of a solar adsorption refrigeration system with enhanced mass transfer based on an ideal basic solid adsorption refrigeration cycle with activated carbon-methanol as the working pair. The working principle of the hypothesis was analysed, and the coefficient of performance (COP) was used to assess the system’s performance. A solar simulator consisting of a halogen lamp light resource array was adopted to provide a light source for heating. Different comparative tests under different input radiation energy conditions were carried out to prove the hypothesis that a lower condensing pressure can be realized by using an enhanced mass transfer method and is good for increasing the amount of desorption. The variations of the adsorbent bed temperature, system pressure and ice production were analysed. The maximum COP and maximum ice-making capacity of the enhanced mass transfer adsorption refrigeration system were 0.142 and 7 kg, respectively. The average COP of the novel system showed an improvement of 35.9% compared with the average COP of the natural mass transfer adsorption refrigeration system when the input radiation energy was not less than 14.7 MJ during a refrigeration cycle.

Simple Analysis Solar Solid Adsorption Refrigeration in the Application of Central Air Conditioning

Advantage of solid adsorption refrigeration is environmental protection, energy saving, simple structure, no noise and the advantages of stable and reliable operation, the use of solar energy driven refrigeration is an energy-saving environmental protection technology, it can effectively reduce the huge energy consumption and environmental pollution due to the burning of fossil energy resources. This article introduces the general situation of development of solar adsorption refrigeration, puts forward the research progress and application prospect of the solar energy air conditioning system.

The Impact of Condensing Pressure on the Performance of Solar Solid Adsorption Refrigeration System

A new solar solid adsorption refrigeration system is established in this paper, and the variation relationship between the adsorbent bed temperature and pressure with time are analyzed, and the effects of adsorbent bed condensing pressure on the system performance is researched. Results show that, under the same working conditions, when the condensing pressure is 39 kPa, the daily ice-making capacity of system reach to 5.5 kg with the refrigerating capacity of 2.26 MJ; And when the condensing pressure is 63 kPa, the ice-making capacity of system is only for 3 kg with the refrigerating capacity of 1.48 MJ; The refrigerating capacity of the former is 1.5 times of the latter.

Dynamic Simulation of Solid Adsorption Solar Refrigerator System with AC/CH<sub>3</sub>OH as a Working Pair

Solid adsorption system, one of alternative refrigeration systems, is utilized to provide cold for refrigerator or air-conditioner and can be operated by assistance of solar heat. System performance study through computer usage to develop simulation program and simulate behaviors of system operation can give designed system which suits for user’s need. Also, the present study aims to develop dynamic simulation program of solid adsorption refrigeration system operated by solar assistance to simulate behaviors of system operation and its performance. Flat plate collectror is utilized to provide thermal energy for system’s adsorber and activated carbon/methanol is used to be a suitable working pair. Simulation procedure starts with various solar radiation intensities as input energy on solar collector and water is used as collector working fluid. Behavior of system operation can be considered to be 4 steps as isosteric heating, isobaric desorption, isosteric cooling and isobaric adsorption, respectively. This research studies the effect of varying solar radiation intensity on temperature, pressure of adsorber, adsorption ratio at each steps of system operated ranging from 6:00 am (the first day) to 6:00 am (the next day) and system performance which is defined as coefficient of performance, COP. In addition, the simulation result shows monthly average COP of 0.43 compared to a result of another previous research work under the same operating condition and the percentage error is 7.5%.

Structure optimization and performance experiments of a solar-powered finned-tube adsorption refrigeration system

A large-diameter aluminum-alloy finned-tube absorbent bed collector was designed and optimized by enhancing the heat and mass transfer in the collector. The collection efficiency of the adsorbent bed collector was between 31.64% and 42.7%, and the temperature distribution in the absorbent bed was relatively uniform, beneficial to adsorption/desorption of the adsorbate in the absorbent bed. A solar-powered solid adsorption refrigeration system with the finned-tube absorbent bed collector was built. Some experiments corresponding to the adsorption/desorption process with and without a valve control were conducted in four typical weather conditions: sunny with clear sky, sunny with partly cloudy sky, cloudy sky and overcast sky. Activated carbon–methanol was utilized as the working pair for adsorption refrigeration in the experiments. The experiments achieved the maximum COP of 0.122 and the maximum daily ice-making of 6.5kg. Under the weather conditions of sunny with clear sky, sunny with partly cloudy sky, and cloudy sky, ice-making phenomenon were observed. Even in the overcast-sky weather condition, the cooling efficiency of the system still reached 0.039 when the total solar radiation was 11.51MJ. The cooling efficiency of the solar-powered adsorption refrigeration system with a valve control in the adsorption/desorption process was significantly higher than that without a valve control.

Study of adsorption characteristics in silica gel–water adsorption refrigeration

As one of environmentally friendly refrigeration methods, solid adsorption refrigeration has tracked much interest over the world. Silica gel is popularly used in adsorption refrigeration systems as the adsorbent. Like a compressor in a compression refrigeration system, the adsorbent is vital to the performance of adsorption refrigeration systems. In this work, many different silica gel samples were prepared according to their application surroundings in silica gel–water adsorption refrigeration systems. The adsorption characteristics including variations, deterioration, and improvements of the adsorption property were detected. The specific surface area, silanol content, adsorption capacity, and pore size distributions of those samples were tested. The corresponding adsorption isotherms were achieved. The experimental results indicated that the adsorption capacity of the silica gel was influenced by many factors. But pollution by solid particulates was the primary factor to decline the adsorption capacity.

Numerical Analysis of Heat and Mass Transfer in an Annular Porous Adsorber for Solar Cooling System

The present study deals with a solid adsorption refrigerator analysis using activated carbon/methanol pair. It is a contribution to technology development of solar cooling systems. The main objective consists to analyse the heat and mass transfer in an annular porous adsorber that is the most important component of the system. The porous medium is contained in the annular space and the adsorber is heated by solar energy. A general model equation is used for modelling the transient heat and mass transfer. Effects of the key parameters on the adsorbed quantity, the coefficient of performance, and thus on the system performance are analysed and discussed.

Mathematics model for heat and mass transfer on an adsorption bed

AbstractIn a solid adsorption refrigeration system, the real cycle with non‐equilibrium adsorption is different from the ideal cycle with equilibrium adsorption. To investigate the heat and mass transfer process inside the adsorption bed, a model was established. Mathematical models were then solved by numerical method. The best cycle time of 24 minutes was ascertained through the strategy of SCP priority and paying attention to COP. The influence of the length of adsorption cell tube to the performance of refrigeration system is discussed. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20271 Copyright © 2009 Wiley Periodicals, Inc.

Heat and mass transfer in adsorbent bed with consideration of non-equilibrium adsorption

In the solid adsorption refrigeration cycles, the actual adsorption processes are all non-equilibrium. To investigate the heat and mass transfer in adsorbent bed, mathematical model is established and solved by a numerical method. The relations between adsorption temperature, adsorption velocity, adsorption quantity, coefficient of performance (COP), specific cooling power (SCP) and time are discussed during the process of cooling the adsorbent bed. The relations between desorption temperature, desorption velocity, desorption quantity and time are discussed during the process of heating the adsorbent bed. It indicates that there is a peak value for adsorption velocity in the adsorption process and there is also a peak value for desorption velocity in the desorption process. It also shows that the changing rate of the adsorbent temperature tends to let up, and the coefficient of performance value grows nearly linearly in the adsorption process and there is a peak value of SCP in the adsorption process.

Design improvements for a collector/generator/adsorber of a solid adsorption solar refrigerator

A study of the effects of different collector design parameters on the performances of a solar powered solid adsorption refrigerator is presented. The refrigerator uses activated carbon/methanol as the adsorbent/refrigerant pair. The study was undertaken using a computer simulation program developed from a transient analysis of the system. The parameters tested are the collector plate emissivity/absorptivity combination, adsorbent packing density, tube spacing, outer tube outside diameter, adsorbent thermal conductivity, heat transfer coefficient at adsorbent/tube interface, and adsorbent tube/collector plate materials combination. Two performance indicators namely, condensate yield and coefficient of performance (COP) were used in the study as figures of merit. A multiple regression technique was used to correlate the performance indicators with the collector parameters through a quadratic relation. Consequently an objective function, suitable for selecting optimal values of the parameters is defined, subject to specified constraints. Selecting the COP as the preferred indicator parameter, optimization was then carried out. Improvements in the ranges of 29–38% for COP and 26–35% for condensate yield were obtained with optimal choices of tube spacing, adsorbent packing density and collector plate/adsorbent tube material combinations.

06/02004 Design, simulation and performance of a waste heat driven adsorption ice maker for fishing boat: Wang, L. W. et al. Energy, 2006, 31, (2–3), 244–259

A no valve, flat plate solar ice maker is developed on the basis of previous research achievements of a large number experiments and theory analysis. There are no valves and measure gauges installed on this advanced device, also no moving parts on this device, activated carbon and methanol is used as working pairs for this no valve solar ice maker. Experimental results under both indoor and outdoor showed that each subsystem, such as adsorbent bed, condenser, evaporator, demonstrated a good performance on system running processes; this no valve solar ice maker prototype is approached to practical application of mass production from view of cost and techniques. After the successful study of this no valve solar ice maker, two new improved economic solar ice makers are fabricated for mass application in China now. All this will accelerate practical application of solid adsorption refrigeration driven by solar energy.

Study of the Advanced Application Characteristics of a Solar Solid Adsorption Refrigerator

On the basis of previous research work on solar solid adsorption refrigeration, some advanced application methods for a solar ice maker have been studied. These include the efficient design of a new adsorbent bed; experimental studies of working pairs for a solar ice maker using activated carbon—methanol and activated carbon—ethanol; the effects of sky cloud cover on a solar ice maker; and the efficient utilization of a solar ice maker with provision for heating and cooling. The provision of tables to assist in the choice of a mass-produced solar ice maker was also examined. Simulation of the characteristics of a solar ice maker has been undertaken in some areas in Tibet where the natural climatic conditions appear to be ideal for the operation of such a device.

Investigation of non-equilibrium adsorption character in solid adsorption refrigeration cycle

The adsorber is the key element in an adsorption refrigeration system. Its characteristic coupled with heat and mass transfer and adsorption dominats the cycle performance. In general, the velocity of adsorption in adsorber is not faster than that of heat transfer, that is, the adsorption rate does not reach the equilibrium value at each status point in real operation. The feature of non-equilibrium adsorption results of apparent different characteristic on adsorption refrigeration performance comparing with the case of equilibrium adsorption model. Based on numerical simulation, both models with equilibrium and non-equilibrium adsorption are compared with each other. The simulations condition includes various surface diffusing velocity coefficients. This paper shows the characteristic of temperature and adsorbed mass rate distribution in adsorber and some thermodynamic analysis on adsorption refrigeration cycle. It could be observed that non-equilibrium adsorption should be taken into account in adsorption refrigeration particularly for short cycle time and vacuum system.

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 CaCl 2 as adsorbent and NH 3 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 CaCl 2–NH 3 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.

TRANSIENT EFFECTS ON THE PERFORMANCES OF A SOLID ADSORPTION SOLAR REFRIGERATOR

A study of the heat and mass transfer behaviours of a solar energy collector/generator/adsorber for use in solid adsorption refrigeration system is presented. The collector/generator/adsorber uses activated carbon as the adsorbent and methanol as the refrigerant. The study was undertaken using an earlier developed mathematical model of the transient system. The refrigerator performance was found to depend very strongly on the heat and mass transfers to and from the adsorbent in the collector/generator/adsorber. The two values of the thermal conductivity of activated carbon of the order of 0.1 W/mk is due mainly to its poor porosity characteristics. However, improvement in the refrigerator performance indicators, such as condensate yield, mass of ice produced and coefficient of performance are possible with either distributing adsorbents between fins or use of special additives or both. A similar level of improvement in its heat and mass transfer behaviour is possible with construction materials of lighter weight and higher conductivity such as aluminum plate and tube. JMDMES Vol.2(1) 2003: 27-38

Development of no valve solar ice maker

A no valve, flat plate solar ice maker is developed on the basis of previous research achievements of a large number experiments and theory analysis. There are no valves and measure gauges installed on this advanced device, also no moving parts on this device, activated carbon and methanol is used as working pairs for this no valve solar ice maker. Experimental results under both indoor and outdoor showed that each subsystem, such as adsorbent bed, condenser, evaporator, demonstrated a good performance on system running processes; this no valve solar ice maker prototype is approached to practical application of mass production from view of cost and techniques. After the successful study of this no valve solar ice maker, two new improved economic solar ice makers are fabricated for mass application in China now. All this will accelerate practical application of solid adsorption refrigeration driven by solar energy.