Technology Development and Comparative Study of Adsorption Refrigeration Cycles Parash Goyal 1 Prashant Baredar 2 Arvind Mittal 3

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1 IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 05, 2015 ISSN (online): Technology Development and Comparative Study of Adsorption Refrigeration Cycles Parash Goyal 1 Prashant Baredar 2 Arvind Mittal 3 1,2,3 Department of Energy Centre 1,2,3 Maulana Azad National Institute of Technology, Bhopal, India Abstract Energy is considered the continuous driving power for economic growth and the major requirement for technological developments. The increasing rate of population, industry, and the per capita energy consumption are the major forces that cause the increase in energy demand during the coming years. However, the conventional energy types are neither reliable nor sustainable and the world s reserves of oil are not large enough to be dependable in the near future. As a consequence, securing sustainable and renewable resources of energy with reasonable costs and without adverse impacts on our environment are the challenge. One solution to this is the application of the adsorption refrigeration systems that are driven by either solar energy or by waste heat. In the present study we have discussed the technological development of various adsorption refrigeration cycles. Moreover, we have provided a comparative study of some important adsorption refrigeration cycles. Key words: Adsorption Refrigeration Cycle, Hybrid System, Solar Refrigeration, Hybrid Systems I. INTRODUCTION Currently 80% on the energy on Earth emanates from fossil fuel resources [1]. It is estimated that this global energy consumption increases by 71% among 2003 and 2030 [2]. This rising energy consumption world- wide makes it urgent to find new solutions to use the energy resources in the more efficient in addition to rational way. In addition, The International Initiate of Refrigeration in Paris (IIF/ IIR) has estimated that approximately 15% of all the so-called electricity produced in depends upon is employed regarding refrigeration and air-conditioning processes of assorted kinds, and the force consumption for air-conditioning systems has been estimated to 45% on the whole households in addition to commercial buildings. The more common vapour compression refrigeration cycles are driven simply by electricity or temperature, which strongly increases the consumption of electricity and fossil vitality. Moreover, peak electricity demand during summer has re-enforced by the actual propagation of air- treatment appliances. So utilization of electricity is a big problem for vapour compression refrigeration program. In developing international locations, a large proportion of individuals live in rural areas where grid electricity is seldom available at present and is likely to be the case for your next few years. Therefore conventional, electrically powered watery vapor compression refrigeration systems might not be of much use for them. Moreover, these regular vapour compression program are driven simply by commercial, non-natural functioning fluids, like the actual chlorofluorocarbons (CFCs), the hydro chlorofluorocarbons (HCFCs) as well as the hydro fluorocarbons (HFCs). They're directly responsible regarding in ozone depletion and/or global increased temperatures. Therefore, the awareness on issues including the decrease of fossil gas resources (with the actual consequent increasing prices of energy), the severe environmental problems or maybe the location challenges (e. g., remote areas) involve the development involving new technologies in addition to led the human kind to appear with greater curiosity for ecological in addition to renewable energy resources. These include wind flow, solar, hydropower, biomass in addition to geothermal energies, or maybe thermal waste from various processes. The use of power from the sun for environmental control receives much attention due to the projected world energy shortage as a result of coincidence between the actual peak of cooling demand as well as the solar radiation availability. Refrigeration is a fascinating application of power from the sun because the incident radiation as well as the need for chilly production both achieve maximum levels inside the same period. With developing countries, solar refrigeration is surely an increasingly acknowledged priority because of the desires for food in addition to vaccine preservation and mainly because that solar energy is mostly widely available in these countries. Fig. 1 illustrates a possible classification of solar chillers and refrigeration cycles. Each of the strategy, except the adsorption cooling technique, maintains some great benefits of its conventional type but is afflicted with certain limitations. Photo voltaic refrigerators, in spite of these commercial success amid solar refrigerators, have high mounted cost and hopeless prospects for on the rural site manufacture. Liquid absorption units possess the problem of producing some absorbent using the refrigerant during age group, thus requiring rectification. Reliable absorbents characteristically break down after repeated cycles of operation, as regarding the CaCl2/NH3 couple [3, 4]. Generally, special treatments on the absorbents are necessary to obtain hard porous granules [5, 6], thereby increasing the system first cost. Solar adsorption refrigerators tend not to possess these drawbacks. Most importantly, they may be completely autonomous functioning and easily flexible to simple (soft) in addition to complex (high) engineering [7]. Adsorption occurs with the surface interface involving two phases, in which cohesive forces which include electrostatic forces in addition to hydrogen bonding, act relating to the molecules of all substances regardless of their state involving aggregation. Unbalanced surface forces with the phase boundary cause changes inside the concentration of molecules with the solid/fluid interface. The method of adsorption involves separation of a substance from one phase together with its accumulation or concentration with the surface of an additional. The adsorbing phase could be the adsorbent, and the material concentrated or adsorbed with the surface of that phase could be the adsorbate. Adsorbents are seen as surface properties for instance surface area in addition to polarity. There are a number of working pairs regarding solid adsorption. For the successful operation of a solid adsorption process, careful selection of the working medium All rights reserved by 350

2 is important. It is since, the performance of the system varies over lots using different functioning pairs at diverse temperatures. The benefits and drawbacks of different functioning media and the properties are stated and discussed in this section. For virtually any refrigerating application, the adsorbent need to have high adsorptive potential at ambient temperatures and low demands but less adsorptive potential at high temperatures and high demands. A prominent difficulty for adsorption refrigeration is that this COP is small. For a conventional simple cycle under the condition of air conditioning, generally COP is lower than 0. 4 [8]; if during ice making using a refrigerating temperature lower than 0 C, commonly COP is lower than 0. 2 and beneath some conditions is even lower than 0. 1 [9, 10, 11] mainly because that the adsorption effectiveness usually decreases using the evaporation temperature. The reason behind the low COP is especially caused by the actual big temperature fluctuation on the adsorption bed under the condition of alternating heating in addition to cooling processes. As a way to improve the COP on the adsorption refrigeration program, the concept involving heat recovery seemed to be proposed. The principle involving heat recovery was submit by Tchernev at first [12], for that this heat transfer water was preheated through the adsorption heat, then was heated through the boiler and passed to the adsorber to supply the desorption heat. Nowadays the warmth recovery cycles analyzed by researchers largely include double-bed temperature recovery cycle, cascading cycle, multi-stage never-ending cycle, thermal wave neverending cycle, and so with. In the present study we have extensively discussed the actual technological development involving different adsorption refrigeration cycles. Moreover, a comparative study for your various adsorption cycles available is also offered. II. ADSORPTION REFRIGERATION CYCLES The adsorption refrigeration cycle system can roughly be summarized in fig.2 through the development history of adsorption refrigeration as well as the study status of scholars intercontinental. By the working principle the adsorption refrigeration cycle can be divided into intermittent cycles and continuous cycles. For the intermittent adsorption refrigeration cycles there seemed to be always one bed utilized within the system. For the continuous refrigeration cycles there are generally a couple of beds running alternately, which provide continuous refrigeration output. For an adsorption refrigeration cycle Fig. 1: classification of solar chillers and refrigeration cycles only if the heating and desorbing process as well as the cooling and adsorbing process are participating, it is generally defined for the reason that basic adsorption refrigeration cycle. The advanced adsorption refrigeration cycles are commonly termed as the cycles with heat and mass recovery processes, such as two-bed heat recovery process, multi-bed heat recovery process, mass recovery procedure, thermal wave, and convective arctic wave cycles. According to this adsorption system characteristics and temp source selections, the advanced refrigeration cycles of multistage and cascading refrigeration system can even be constructed. A. A Basic Adsorption Cycle An elementary adsorption cycle consists of a number of thermodynamic steps, which can be well represented with Fig. 2: Classification of adsorption refrigeration cycles the Clapeyron diagram, as revealed in Fig. 1. The idealized cycle begins at a point (point A in Fig. 3) where the adsorbent is at low heat range TA and at low-pressure PE All rights reserved by 351

3 (evaporating pressure). A B signifies the heating of adsorbent, along with adsorbate. The collector is linked to the condenser and the progressive heating on the adsorbent from B to D causes some adsorbate to be desorbed and its vapor to be condensed (point C). When your adsorbent reaches its maximum heat range TD; desorption ceases. Then the liquid adsorbate is transferred into the evaporator from C to E along with the collector is closed and cooled off. The decrease in temperature Deb to F induces the reduction in pressure from PC to PE: Then a collector is connected to your evaporator and adsorption and evaporation occur while the adsorbent is cooled from F to some. During this cooling period heat is withdrawn to diminish the temperature of the adsorbent. Fig. 3: Basic adsorption refrigeration system B. Double-Bed Heat Recovery Cycle, Cascading Cycle, and Multi-stage Cycle: For such form of cycles in the heat recovery process heat from a high-temperature adsorption bed is delivered to the low-temperature adsorption bed because of the temperature potential. Because the heat recovered is mainly the sensible heat of the actual adsorbers, the heat cannot be recovered from your low temperature bed to the high temperature bed. Thus the coefficient of heat recovery is fixed. In the research for the actual continuous refrigeration cycle with double-bed heat recovery process [12-17], the heat recovery coefficient gleaned from experiments is [18]. The very best result of heat recovery coefficient for that cascading cycle is 0. 5 [8, 19], although in the simulation it is often [88]. Among three kinds of cycles, i. e., double-bed heat recovery cycle, cascading cycle and also multi-stage cycle, the typical cycle is usually a multi-stage and six-bed adsorption routine proposed by Saha and Kashiwagi [20]. The three-stage cycle system using silica gel water for the reason that working pair can decrease the actual driven temperature effectively. The experimental results showed which can obtain a chillier water of 12 C if your heat source temperature is 50 C and the second law of thermodynamics productivity is Its driven temperature is leaner than that of the LiBr assimilation system. Such a technology provided a good way for the recycling use of low grade heat of C. SJTU also developed a sort of two-stage cycle for the snowy conditions, such a type of cycle could be driven by a heat source while using temperature lower than 100 C, and can generate the cooling power with temperatures the small sum of 15 C when the environmental temperature is just about C [21]. Fig. 4: Two-stage cascading double effect adsorption refrigeration cycle (adsorption heat utilization). (a) Diagram of the temperature for the cycle and (b) the heating and cooling processes of adsorbent bed. the same equilibrium temperature difference for both metal C. Thermal Wave and Convective Thermal Wave Cycle hydrides under the condition of same pressure, a very steep Thermal wave cycle was proposed by Shelton [22]. His thermal wave can be generated by the accumulating theory indicated that the heat recovery coefficient of a temperature effect in the adsorption bed. Critoph [24] thermal wave cycle can reach 0.7 and the COP of the heat suggested a convective thermal wave cycle. In such a cycle, pump is The principle of the thermal wave cycle is to the refrigerant served as the heat transfer fluid, which could use the flow of the thermal fluids, which transferred the heat improve the heat recovery efficiency effectively because of within the adsorbers to form a steep temperature wave. For the direct contact between the heat transfer fluid and the such technology the heat can be transferred from the low solid adsorbent. temperature adsorber to the high temperature adsorber [8]. Fig. 5 shows the schematics and process of the This concept has been applied to chemical heat pumps. thermal wave and convective thermal wave adsorption Willers et al. have studied a multi-hydride thermal-wave refrigeration cycle. concept [23]. For this cycle, through the combination of low-temperature and high-temperature metal hydride, with All rights reserved by 352

4 Fig. 6: Schematics of Mass Recovery Cycle Fig. 5: Thermal wave and convective thermal wave adsorption cycles D. Mass Recovery Cycle In addition to the heat recovery cycle there is a mass recovery cycle. The mass recovery cycle is that the refrigerant gas in the high pressure generator after desorption is transferred to the low pressure generator of adsorption as a result of the pressure difference between two adsorption beds. It can effectively improve the adsorption/desorption quantity because of the large pressure difference between two beds, thereby enhance the cooling capacity and improving the COP. If compared with the basic cycle, the largest COP increment of the system can reach 100%. Fig. 6 shows the schematic design of a mass recovery cycle. E. Combined Adsorption-Absorption Refrigeration Cycle/ Hybrid cycles Two-stage or three-stage combined adsorption-absorption refrigeration cycle is composed of the adsorption refrigeration system driven by a high temperature heat source and the absorption refrigeration system driven by the exhaust heat from the adsorption system. The total theoretical COP of the combination refrigeration cycle with adsorption chiller of NiCl2-NH3 (COP=0.27) or two-bed zeolite water adsorption chiller (COP=0.50) as the first stage cycle, and absorption chiller of lithium bromide water (COP =0.75) as the second stage cycle is The theoretical COP of the combination refrigeration cycle with metal hydride adsorption chiller as the first stage cycle, and silica gel water or lithium bromide water absorption chiller as the second stage cycle is expected to reach 1.5. The COP of combination refrigeration cycle is high, but the system is very complicated. A brief comparison of the above discussed adsorption refrigeration cycles is presented in table1. Table 1: Comparison of Adsorption refrigeration cycles All rights reserved by 353

5 III. CONCLUSION Since 1970, the issue of energy crisis started cropping up and in the view of controlling the adverse climatic scenario many protocols and conventions were brought into practice. Also, an intensified stress was put on the search of the alternatives to the conventional vapor compression cycles. The solution was the application of the adsorption refrigeration phenomenon. Various researchers developed numerous adsorption refrigeration cycles. Among all, a few major adsorption refrigeration cycles have been discussed here. Also, a comparison of the adsorption refrigeration cycles is also presented here. Their COP, SCP, operating temperatures are discussed. All the cycles possess some advantages as well as some disadvantages. But on the basis of comparison provided we can conclude that among all thermal wave adsorption refrigeration cycles and hybrid adsorption cycles gives the best performances. REFERENCES [1] Desideri U, Proietti S, Sdringola P. 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