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1.
Experimental investigation of mass recovery adsorption refrigeration cycle   总被引:1,自引:0,他引:1  
The study investigates the performance of silica gel–water adsorption refrigeration cycle with mass recovery process by experimental prototype machine. In an adsorption refrigeration cycle, the pressures in adsorber and desorber are different. The mass recovery cycle utilizes the pressure difference to enhance the refrigerant mass circulation. Moreover, novel cycle was proposed for improvement of cooling output. In our previous study, simulation analysis shows that mass recovery cycle has the advantage over conventional single-stage. Experiments with prototype machine were conducted to investigate the performance improvement of mass recovery cycle in the present paper. Specific cooling power (SCP) and coefficient of performance (COP) were calculated with experimental data to analyze the influences of operating conditions. The proposed cycle was compared with the single-stage cycle in terms of SCP and COP. The results show that SCP of mass recovery cycle is superior to that of conventional cycle and mass recovery cycle is effective with low temperature heat source.  相似文献   

2.
A novel cascading adsorption cooling cycle for refrigeration purposes is proposed in this paper. This cycle consists of two zeolite adsorbent beds and a silica gel adsorbent bed. The working refrigerant for the three adsorbers is water. The zeolite adsorbent bed is configured as the high temperature stage while the silica gel adsorbent bed acts as the low temperature stage. Both heat and mass recovery are carried out between the two zeolite adsorbent beds. In addition, heat is also exchanged between the zeolite adsorbent and the silica gel adsorbent beds. A lumped model is assumed for this cascading cycle. The COP for the base case is found to be 1.35, which is much higher than the COP of an intermittent cycle (about 0.5) and a two-bed combined heat and mass recovery cycle (about 0.8). However, its specific cooling power (SCP) of 42.7 W/kg is much lower than that of the intermittent cycle. The numerical results indicate that an optimal middle temperature exists for a prescribed driven temperature. The optimal COP increases with an increase in the driven temperature. However, when the driven temperature increases beyond 503 K, there is negligible change in the COP.  相似文献   

3.
An adsorption cooling system was developed and tested and various operation procedures have been tried. The experimental results show that the heat recovery operation between two adsorption beds will increase the COP by about 25% if compared with one adsorber basic cycle system. It was also proved that mass recovery is very effective for heat recovery adsorption cooling operation, which may help to obtain a COP increase of more than 10%. Theoretical analyses on the COP have been completed for various heat and mass recovery cycles, such as basic intermittent adsorption cycle, continuous two-adsorber heat recovery cycle, mass recovery cycle, mass recovery with sensible heat recovery, and mass recovery with both sensible heat and heat of adsorption recovery. The theoretical results are in good agreement with experimental values. Based upon the developed theoretical model, it is possible to predict the COP for various operation procedures of a real adsorption cooling system.  相似文献   

4.
A newly developed adsorption water chiller is introduced and tested. In the new adsorption refrigeration system, there are no refrigerant valves, the problem of mass transfer resistance resulting in pressure drop along refrigerant passage in conventional systems when methanol or water is used as refrigerant can be absolutely solved. Silica-gel–water is used as working pair and mass recovery-like process is adopted in order to use low temperature heat source ranging from 70 to 85 °C effectively. The experiment results demonstrate that the chiller (26.4 kg silica-gel in each adsorber) has a cooling capacity of 2–7.3 kW and COP ranging 0.2–0.42 according to different evaporating temperatures. Based on the experimental tests of the first prototype, the second prototype is designed and tested; the experimental data demonstrate that the chiller performance has been greatly improved, with a heat source temperature of 80 °C, a COP over 0.5 and cooling capacity of 9 kW has been achieved at evaporating temperature of 13 °C.  相似文献   

5.
A theoretical study of a novel regenerative ejector refrigeration cycle   总被引:1,自引:0,他引:1  
There has been a demand for developments of the ejector refrigeration systems using low grade thermal energy, such as solar energy and waste heat. In this paper, a novel regenerative ejector refrigeration cycle was described, which uses an auxiliary jet pump and a conventional regenerator to enhance the performance of the novel cycle. The theoretical analysis on the performance characteristics was carried out for the novel cycle with the refrigerant R141b. Compared with the conventional cycle, the simulation results show that the coefficient of performance (COP) of the novel cycle increases, respectively, by from 9.3 to 12.1% when generating temperature is in a range of 80–160 °C, the condensing temperature is in a range of 35–45 °C and the evaporating temperature is fixed at 10 °C. Especially due to the enhanced regeneration with increasing the pump outlet pressure, the improvement of COP of the novel cycle is approached to 17.8% compared with that in the conventional cycle under the operating condition that generating temperature is 100 °C, condensing temperature is 40 °C and evaporating temperature is 10 °C. Therefore, the characteristics of the novel cycle performance show its promise in using low grade thermal energy for the ejector refrigeration system.  相似文献   

6.
This paper presents the results of a predictive two-dimensional mathematical model of an adsorption cooling machine consisting of a double consolidated adsorbent bed with internal heat recovery. The results of a base-case, taken as a reference, demonstrated that the COP of the double bed adsorption refrigeration cycle increases with respect to the single bed configuration. However, it was verified that, in order to maximize also the specific power of the machine, the adsorbent beds must have proper thermo-physical properties.Consequently, a sensitivity analysis was carried out, studying the influence of the main heat and mass transfer parameters on the performance of the machine. The results obtained allowed us to define the adsorbent bed design that maximizes its heat and mass transfer properties, as well as the most profitable heat recovery conditions.  相似文献   

7.
In order to settle the problem of the corrosion between sea water and the steel adsorber for ammonia system, a split heat pipe type adsorption ice making test unit, which use compound adsorbent of CaCl2 and activated carbon to improve the adsorption performance, is designed and constructed. For this test unit there is mass recovery function between two beds and the CaCl2 in compound adsorbent per bed is 1.88 kg, and there is only one pump for the whole heating and cooling phase for adsorbers. Performances of this system are tested; the lowest evaporating temperature is as low as −42 °C. At the evaporating temperature of −35 and −25 °C, the cooling powers are 0.89 and 1.18 kW, respectively. At the evaporating temperature of −15 °C, its average cooling power is 1.37 kW, which corresponds coefficient of performance of refrigeration COP=0.41 and specific cooling power per kilogram CaCl2 of each adsorber SCP=731 W kg−1. The mass recovery process has improved SCP and COP for the system by 15.5 and 24.1%, respectively. Heat transfer performance is also improved by the split heat pipe construction; the average heat transfer coefficient for a whole cycle is 155.8 W m−2 °C−1.  相似文献   

8.
Over the past few decades there have been considerable efforts to use adsorption (solid/vapor) for cooling and heat pump applications, but intensified efforts were initiated only since the imposition of international restrictions on the production and utilization of CFCs and HCFCs. In this paper, a dual-mode silica gel–water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. This adsorption chiller utilizes effectively low-temperature solar or waste heat sources of temperature between 40 and 95 °C. Two operation modes are possible for the advanced chiller. The first operation mode will be to work as a highly efficient conventional chiller where the driving source temperature is between 60 and 95 °C. The second operation mode will be to work as an advanced three-stage adsorption chiller where the available driving source temperature is very low (between 40 and 60 °C). With this very low driving source temperature in combination with a coolant at 30 °C, no other cycle except an advanced adsorption cycle with staged regeneration will be operational. The drawback of this operational mode is its poor efficiency in terms of cooling capacity and COP. Simulation results show that the optimum COP values are obtained at driving source temperatures between 50 and 55 °C in three-stage mode, and between 80 and 85 °C in single-stage, multi-bed mode.  相似文献   

9.
Thermal heat driven adsorption systems have been gained considerable attention on the recent energy utilization trend. However, the drawbacks of these adsorption systems are their poor performance. It is urgently necessary to improve the system performance of the adsorption cycles. There are two major ways for the system performance improvement. One is to develop new adsorbent material well suited to low temperature heat regeneration. The other is to enhance heat and mass transfer in the adsorber/desorber heat exchanger. The objective of the paper is to investigate the system performance of an adsorption cycle. The cycle utilizes activated carbon fiber (ACF)/methanol as adsorbent/refrigerant pair. In this paper, specific cooling effect SCE and COP of the system are numerically evaluated from the adsorption equilibrium theory with different hot, cooling and chilled fluid inlet temperatures. It is confirmed that the influences of hot, cooling and chilled fluid inlet temperatures on the system performance are qualitatively similar to those of silica gel/water pair. Even though, the driving temperature levels of ACF/methanol and silica gel/water are different. There is an optimum condition for COP to reach at maximum for ACF/methanol pair. Particularly, the ACF/methanol system shows better performance with lower chilled fluid inlet temperature between −20 and 20 °C.  相似文献   

10.
An experimental investigation of the performance of a micro-combined cooling, heating and power (CCHP) system is described. The natural gas and LPG-fired micro-CCHP system uses a small-scale generator set driven by a gas engine and a new small-scale adsorption chiller, which has a rated electricity power of 12 kW, a rated cooling of 9 kW and a rated heating capacity of 28 kW. Silica gel–water is used as working pair in the adsorption cooling system. The refrigeration COP of the adsorption chiller is over 0.3 for 13 °C evaporation temperature. The test facility designed and built is described, which supplies better test-rig platform for cooling, heating and power cogeneration. Experimental methodology of this system is presented and the results are discussed. An energetic analysis of micro-CCHP system is performed as well. The overall thermal and electrical efficiency is over 70%.  相似文献   

11.
The paper is aimed to develop a high performance rotary solid desiccant cooling system using a novel compound desiccant wheel (DW). The unique feature of the desiccant wheel is that it can work well under a lower regeneration temperature and have a higher dehumidification capacity due to the contribution of the new compound desiccant materials. Experimental results indicate that the novel desiccant wheel under practical operation can remove more moisture from the process air by about 20–40% over the desiccant wheel employing regular silica gel. A mathematical model that is used to predict the system performance has been validated with the test results. By integrating the desiccant wheel with evaporative cooling, heat recovery and heating for regeneration sections, a solid desiccant cooling system can be formed. Simulation results show that because of the use of the new compound desiccant, the desiccant cooling system can work under much lower regeneration temperature and have a relative high COP, thus low grade thermal energy resources, such as solar energy, waste heat, etc., can be efficiently utilized to drive such a cooling cycle.  相似文献   

12.
This paper presented a novel autocascade refrigeration cycle (NARC) with an ejector. In the NARC, the ejector is used to recover some available work to increase the compressor suction pressure. The NARC enables the compressor to operate at lower pressure ratio, which in turn improves the cycle performance. Theoretical computation model based on the constant pressure-mixing model for the ejector is used to perform a thermodynamic cycle analysis for the NARC with the refrigerant mixture of R23/R134a. The effects of some main parameters on cycle performance were investigated. The results show the NARC has an outstanding merit in decreasing the pressure ratio of compressor as well as increasing the COP. For NARC operated at the condenser outlet temperature of 40 °C, the evaporator inlet temperature of −40.3 °C, and the mass fraction of R23 is 0.15, the pressure ratio of the ejector reaches to 1.35, the pressure ratio of compressor is reduced by 25.8% and the COP is improved by 19.1% over the conventional autocascade refrigeration cycle.  相似文献   

13.
This paper is a part in a series that reports on the experimental study of the performance of the two-phase ejector expansion refrigeration cycle. In the present study, three two-phase ejectors are used as an expansion device in the refrigeration cycle. The effects of throat diameter of the motive nozzle, on the coefficient of performance, primary mass flow rate of the refrigerant, secondary mass flow rate of the refrigerant, recirculation ratio, average evaporator pressure, compressor pressure ratio, discharge temperature and cooling capacity, which have never before appeared in open literature, are presented. The effects of the heat sink and heat source temperatures on the system performance are also discussed.  相似文献   

14.
Refrigerant vapor-injection technique has been well justified to improve the performance of systems in refrigeration applications. However, it has not received much attention for air conditioning applications, particularly for air conditioning in hot climates and for heat pumping in cold climates. In this study, the performance of an 11 kW R410A heat pump system with a two-stage vapor-injected scroll compressor was experimentally investigated. The vapor-injected scroll compressor was tested with the cycle options of both flash tank and internal heat exchanger configurations. A cooling capacity gain of around 14% with 4% COP improvement at the ambient temperature of 46.1 °C and about 30% heating capacity improvement with 20% COP gain at the ambient temperature of −17.8 °C were found for the vapor-injected R410A heat pump system as compared to the conventional system which has the same compressor displacement volume.  相似文献   

15.
In this study, an improved cooling cycle for a conventional multi-evaporators simple compression system utilizing ejector for vapour precompression is analyzed. The ejector-enhanced refrigeration cycle consists of multi-evaporators that operate at different pressure and temperature levels. A one-dimensional mathematical model of the ejector was developed using the equations governing the flow and thermodynamics based on the constant-area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The energy efficiency and the performance characteristics of the novel cycle are theoretically investigated. The comparison between the novel and conventional system was made under the same operating conditions. Also, a comparison of the system performances with environment friendly refrigerants (R290, R600a, R717, R134a, R152a, and R141b) is made. The theoretical results show that the COP of the novel cycle is better than the conventional system.  相似文献   

16.
相比于传统的吸附式制冷,再吸附制冷作为一种新型的制冷方式,其结构更加简单,并且其制冷性能系数也比相同条件下的吸附式制冷系统要高,故有较好的应用前景。但受到吸附剂的传热传质性能的限制,难以实现高效的再吸附制冷。本文利用硫化石墨作为吸附剂的基质,对其导热系数以及渗透率进行了测试比较,优选吸附剂。并且针对再吸附制冷系统建立了相关数学模型,分析不同工况条件下吸附剂工质对的性能。对整个再吸附制冷过程进行模拟仿真,从而得到不同工况下的制冷性能。结果表明,采用新型复合吸附剂的再吸附系统,COP最大可达到0.3以上,SCP最大可达到161 W/kg。  相似文献   

17.
The performance of a single-stage metal hydride cooling system working with the ZrMnFe/MmNi4.5Al0.5 pair has been evaluated based on heat transfer and reaction kinetics considerations. Results show that the initial and operating costs of the system have to be minimized by optimizing the bed thickness, effective thermal conductivity and overall heat transfer coefficients. Of the three operating temperatures (heat source, heat sink and refrigeration temperatures), refrigeration temperature has the greatest influence on system performance, as desorption during the refrigeration process normally controls the cycle time and specific alloy output. However, heat source and heat rejection temperatures assume importance at high refrigeration temperatures. The average COP of the above system lies between 0.45 and 0.50.  相似文献   

18.
A ‘three-temperature’ model of the adsorption cycles with heat regeneration is used for investigating and analysing the influence of different parameters on the performance of such cycles. The influence of the heat source temperature on the thermodynamic efficiency (COP/COPCarnot) is investigated. The result is that the thermodynamic efficiency of the cycle is always limited. In order to reduce the internal irreversibilities, different internal vapour transports for pressurising (depressurisation) the adsorber are investigated: first, adiabatic direct pressurisation (depressurisation) with the condenser (evaporator) instead of pressure changes by heat transfer; second, adiabatic internal vapour recovery between the adsorbers (partial pressurisation/depressurisation); third, separation of the adsorber into separate compartments between which vapour cannot be redistributed during pressurisation or depressurisation. Results show that the first process significantly reduces the COP, while the second one enhances the cooling power, and the third one does not change the performance. Analysis gives satisfactory explanation of these results.  相似文献   

19.
A refrigeration system was developed which combines a basic vapor compression refrigeration cycle with an ejector cooling cycle. The ejector cooling cycle is driven by the waste heat from the condenser in the vapor compression refrigeration cycle. The additional cooling capacity from the ejector cycle is directly input into the evaporator of the vapor compression refrigeration cycle. The governing equations are derived based on energy and mass conservation in each component including the compressor, ejector, generator, booster and heat exchangers. The system performance is first analyzed for the on-design conditions. The results show that the COP is improved by 9.1% for R22 system. The system is then compared with a basic refrigeration system for variations of five important variables. The system analysis shows that this refrigeration system can effectively improve the COP by the ejector cycle with the refrigerant which has high compressor discharge temperature.  相似文献   

20.
提出R404A直接接触凝结换热的制冷循环,分析R404A直接接触凝结制冷循环的热力性能,并与常规双级压缩制冷循环的性能进行对比。得出结论:在一定的冷凝温度、蒸发温度和过冷液体的过冷度下,直接接触凝结制冷循环存在最佳的饱和液体温度,并在此最佳的饱和液体温度下,获得最优的性能和最小的冷凝热负荷,随着过冷液体的过冷度增大和蒸发温度升高,直接接触凝结制冷循环的性能系数增加、冷凝热负荷减少,获得最优性能的最佳饱和液体温度值提高。过冷液体的过冷度为25℃时,直接接触凝结制冷循环的最佳性能系数较双级压缩制冷循环的最佳性能系数提高6.2%。直接接触凝结制冷循环的最小冷凝热负荷较双级压缩制冷循环的最小冷凝热负荷减小1.8%。  相似文献   

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