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Effect of an Internal Heat Exchanger on the Performances of a Double Evaporator Ejector refrigeration cycle

Fluid Dynamics & Materials Processing 2023年第5期19卷 1115-1128页

作者： Rachedi Khadraoui Latra Boumaraf Philippe Haberschill Mechanical Engineering Department Badji Mokhtar UniversityAnnabaAlgeria Center for Thermal Sciences of Lyon INSAVilleurbanneFrance

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction ***,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is *** assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for *** model also accounts for the friction effect in the ejector mixing *** equations of this model are solved using an Engineering Equation Solver(EES)for different *** are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and *** simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.

关键词： refrigeration cycle double evaporator ejector IHX performance improvement environment-friendlyrefrigerants

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Computational Analysis of Silica gel-Water Adsorption refrigeration cycle with Vapor Recovery

Computational Analysis of Silica gel-Water Adsorption Refrig...

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第一届亚洲制冷空调大会

作者： Akira AKAHIRA K.C.Amanul Alam Yoshinori HAMAMOTO Atsushi AKISAWA Takao KASHIWAGI Tokyo University of Agr. ＆ Tech. 2-24-16 Nakacho Koganei Tokyo 184-8588 Tokyo University of Agr. ＆ Tech. 2-24-16 Nakacho Koganei Tokyo 184-8588 Tokyo University of Agr. ＆ Tech. 2-24-16 Nakacho Koganei Tokyo 184-8588 Tokyo University of Agr. ＆ Tech. 2-24-16 Nakacho Koganei Tokyo 184-8588 Tokyo University of Agr. ＆ Tech. 2-24-16 Nakacho Koganei Tokyo 184-8588

＜正＞The study aims at clarifying the performance of silica gel-water adsorption refrigeration cycle with mass recovery process. A new strategy of mass recovery is proposed. Two cases of mass recovery process are studied and the performances are compared with the performances of conventional two-bed adsorption cycle. One is the conventional mass recovery process in which no heating and cooling are applied to the beds during the mass recovery process, the other is the newly proposed mass recovery process in which beds heating and cooling process are continued during the mass recovery proofs. A cycle simulation program is developed tn predict the performance of the proposed cycle. The results show that the proposed strategy along with mass recovery cycle improves cooling capacity significantly, which is highly desirable in view point of reducing system size. It is slso seen that COP values of the cycle without heating and cooling is increased by 28%, and cooling capacity of the mass recovery cycle with heating and cooling is increased from 11% than those of conventional single stage cycle at hot water temperature 60℃. The results show that mass recovery process has influential effect if the heat source temperature is low.

关键词： Adsorption refrigeration cycle Mass recovery Silica gel Cooling capacity

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A Review on Technologies for the Use of CO2 as a Working Fluid in refrigeration and Power cycles

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Energy and Power Engineering 2024年第6期16卷 217-256页

作者： Orelien T. Boupda Hyacinthe D. Tessemo Isidore B. Nkounda Fongang Francklin G. Nyami Frederic Lontsi Thomas Djiako Laboratory of Energy Higher National Polytechnic School of Douala University of Douala Douala Cameroon Institut Ucac-Icam Douala Cameroon Department of Energy and Mechanical Engineering ISTA-IUG University of Ngaoundere Ngaoundere Cameroon

The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.

关键词： refrigeration cycle Power cycle System Performance Transcritical CO2 cycles Working Fluid

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Thermodynamic analysis on direct air capture for building air condition system:Balance between adsorbent and refrigerant

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Energy and Built Environment 2023年第4期4卷 399-407页

作者： Ying Ji Jinyuan Yong Wei Liu Xuejun Zhang Long Jiang Institute of refrigeration and Cryogenics.Zhejiang University Hangzhou 310027China

Direct air capture(DAC)is one of the most potential technologies to mitigate CO_(2) *** technol-ogy is recognized as a promising CO_(2) capture method in view of its desirable characteristics including reusability of adsorbents and low capital *** further improve thermal performance,evaporation/condensation heat of vapor compression refrigeration(VCR)cycle in air condition system of buildings is adopted for adsorp-tion/desorption process of *** performance of a 4-step temperature swing adsorption process(TSA)is analyzed at various adsorption/desorption temperatures by using different *** on Coefficient of Performance(COP)of VCR cycle is also conducted in search for a balance between adsorbent and *** both real working capacity and COP into consideration,Mg-MOF-74&R134a is the best choice for more amounts of CO_(2).Real working capacity of Mg-MOF-74 is up to 0.38 mol•kg−1 at 70°C,which is twice as much as that of zeolite *** zeolite 13X&R134a shows the best performance of two cycles in view of exergy efficiency and COP,which could reach 81.9%and 7.21,respectively,at 35°*** matches will provide some guidelines for the practical application of the combination of DAC with heating,ventilation and air conditioning(HVAC).

关键词： Direct air capture Temperature swing adsorption refrigeration cycle Condensation heat

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Performance Analysis of an Irreversible Refrigerator with Finite Thermal Capacity Reservoirs

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Journal of Donghua University(English Edition) 2017年第4期34卷 529-532页

作者：赵刘波黄跃武 College of Environmental Science and Engineering Donghua UniversityShanghai 201620China

To explore the influence of heat reservoirs of total thermal capacity at high and low temperature side heat exchanger of an irreversible refrigeration cycle on the coefficient of performance,the cycle model is established. By using the irreversible thermodynamics,much progress had been made in the studies of thermal resistance,heat leak and irreversible factors on the cycle of the coefficient of performance. The analytical formula of coefficient of performance and the distribution ratio of total thermal capacity are derived when the total thermal capacity at high and low temperature side heat exchanger is a constant. The influences of cycle parameters and different kinds of irreversible factors on the coefficient of performance and the optimal distribution ratio are analyzed by numerical computation. The results indicate that the coefficient of performance increases with the increase of the total heat capacity,and decreases with heat leak and internal irreversible factors. Furthermore,the optimal distribution ratio of total thermal capacity,when coefficient of performance reaches the maximum value,only has a connection with the internal dissipation.

关键词： irreversible thermodynamics refrigeration cycle optimization

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