Dao, K.
1978-09-01
An advanced absorption refrigeration cycle was proposed as a heat-activated refrigeration system. Referred to as the double-effect regenerative absorption cycle of cycle 2R, it improves the performance of the conventional single-effect absorption cycle at high heat source temperatures. The performance of cycle 2R continually improves as input temperatures rise, in contrast to the conventional double-effect absorption cycle that has a sharp cut-off temperature below which it ceases to operate. Cycle 2R operates with two subcycles, the first-effect and the second-effect subcycles.
Investigation of ejector re-compression absorption refrigeration cycle
Wu, Shenyi
1999-01-01
This thesis describes a theoretical and experimental investigation of the ejector re-compression lithium bromide absorption refrigeration cycle. In this novel cycle, a steam ejector is used to enhance the concentration process by compressing the vapour to a state that it can be used to re-heat the solution from where it was evolved. Since this cycle recovers the heat otherwise wasted in a conventional absorption cycle, the energy performance of the cycle is improved. The theoretical study sho...
Parametric analysis for a new combined power and ejector-absorption refrigeration cycle
A new combined power and ejector-absorption refrigeration cycle is proposed, which combines the Rankine cycle and the ejector-absorption refrigeration cycle, and could produce both power output and refrigeration output simultaneously. This combined cycle, which originates from the cycle proposed by authors previously, introduces an ejector between the rectifier and the condenser, and provides a performance improvement without greatly increasing the complexity of the system. A parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the cycle performance. It is shown that heat source temperature, condenser temperature, evaporator temperature, turbine inlet pressure, turbine inlet temperature, and basic solution ammonia concentration have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. It is evident that the ejector can improve the performance of the combined cycle proposed by authors previously.
INJECTING ABSORPTION REFRIGERATION CYCLE%引射吸收式制冷循环
苏芬仙; 敖越; 等
2001-01-01
提出了引射吸收式制冷循环。它可以强化吸收，而且可以扩大吸收式制冷的应用领域。分析了引射吸收式制冷循环，提出了参数选择方法，分析了影响引射式吸收制冷循环中吸收过程的因素并与喷淋吸收过程进行了比较。%A new injecting absorption refrigeration cycle is put forward.The new refrigeration cycle can consolidate absorption of the absorption process and at the same time,the absorption refrigeration cycle can be used in more areas.The new refrigeration cycle is analyzed.A method of choosing the parameters is given.The factors are decribed which affect the absorption process.A comparison with the traditional absorption process is also made.
Chih Wu
2004-06-01
Full Text Available Abstract: On the basis of a four-heat-reservoir endoreversible absorption refrigeration cycle model, another linear heat transfer law [i.e., the heat-flux] is adopted, the fundamental optimal relation between the coefficient of performance (COP and the cooling load, as well as the maximum cooling load and the corresponding COP of the cycle coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics or thermodynamic optimization. The optimal distribution of the heat-transfer surface areas is also obtained. Moreover, the effects of the cycle parameters on the COP and the cooling load of the cycle are studied by detailed numerical examples. The results obtained herein are of importance to the optimal design and performance improvement of an absorption refrigeration cycle.
Chih Wu; Fengrui Sun; Tong Zheng; Lingen Chen
2004-01-01
Abstract: On the basis of a four-heat-reservoir endoreversible absorption refrigeration cycle model, another linear heat transfer law [i.e., the heat-flux] is adopted, the fundamental optimal relation between the coefficient of performance (COP) and the cooling load, as well as the maximum cooling load and the corresponding COP of the cycle coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics or thermodynamic optimization. The optimal distribution of...
Exergo-economic analysis of a solar driven hybrid storage absorption refrigeration cycle
Highlights: • Exergo-economic analysis for solar-powered hybrid storage absorption system is done. • Pump, SHX and generator have higher exergetic efficiencies than other components. • Initial cost of evaporator and generator should be reduced even at the expense of irreversibilities. • Irreversibilities cost in SHX should be reduced even at the expense of its initial cost. - Abstract: This paper presents the exergo-economic analysis of a 5 kW refrigeration cycle with hybrid storage system. The novel hybrid storage comprises a cold (ice) storage tank, an ammonia storage tank, a weak solution tank and a strong solution tank to suffice the nighttime cooling load. The exergo-economic analysis is performed to compare the components of the refrigeration cycle based on the costs of initial capital investment and the costs of irreversibilities. The components of the refrigeration cycle are evaluated and compared using exergo-economic variables such as the relative cost difference, exergy destruction cost rate and exergo-economic factor. The effect of generator temperature, condenser temperature and evaporator temperature on the exergetic efficiency of the system is also studied. The paper also presents a quasi-steady exergy and exergo-economic analysis for a representative summer day of Dhahran region. This study can be further used in the optimization of design variables of the studied refrigeration cycle
Intermittent Solar Ammonia Absorption Cycle (ISAAC) refrigeration for lesser developed countries
Erickson, Donald C.
1990-02-01
The Intermittent Solar Ammonia Absorption Cycle (ISAAC) refrigerator is a solar thermal technology which provides low cost, efficient, reliable ice-making to areas without ready access to electricity. An ISAAC refrigeration system consists of a compound parabolic solar collector, two pressure vessels, a condenser, a cold box or refrigerated space, and simple connective piping -- no moving parts or electrical components. Most parts are simple construction or plumbing grade materials, locally available in many remote areas. This technology has numerous potential benefits in lesser developed countries both by providing a cheap, reliable source of ice, and, since manufacture requires only semi-skilled labor, a source of employment to the local economy. Applications include vaccine storage for health care clinics; fish, meat, and dairy product storage; and personal consumption. Importantly, this technology increases the quality of life for people in lesser developed countries without depleting fossil fuel resources or increasing the release of greenhouse gases such as CO2 and chlorofluorocarbons.
A novel absorption refrigeration cycle for heat sources with large temperature change
To increase the use efficiency of available thermal energy in the waste gas/water, a novel high-efficient absorption refrigeration cycle regarded as an improved single-effect/double-lift configuration is proposed. The improved cycle using an evaporator/absorber (E/A) promotes the coefficient of performance and reduces the irreversible loss. Water–lithium bromide is used as the working pair and a simulation study under the steady working conditions is conducted. The results show that the temperature of waste gas discharged is about 20 °C lower than that of the conventional single-effect cycle and the novel cycle we proposed can achieve more cooling capacity per unit mass of waste gas/water at the simulated working conditions. -- Graphical abstract: Pressure – temperature diagram for water – lithium bromide. Highlights: ► A novel waste heat-driven absorption refrigeration cycle is presented. ► The novel cycle can reject heat at much lower temperature. ► The available temperature range of heat source of the proposed cycle is wider. ► Multiple heat sources with different temperatures can be used in the novel cycle
Highlights: • The SGAX cycle is found to be thermoeconomically efficient compared to HGAX cycle. • The HGAX cycle has higher COP and exergy efficiency compared to SGAX cycle. • Minimum product cost is found 180.5 $/GJ and 159.1 $/GJ for HGAX and SGAX, respectively. - Abstract: The main goal of this research is to compare thermoeconomic performance of a GAX absorption cycle and a hybrid GAX absorption cycle in which a compressor is employed to raise the absorber pressure. In order to do this, the ammonia–water standard GAX (SGAX) and hybrid GAX (HGAX) absorption refrigeration cycles are investigated and optimized from the viewpoints of thermodynamics and economics. Parametric studies are carried out and with the help of genetic algorithm (GA), the cycles’ performance is optimized based on the COP and exergy efficiency as well as the cost of unit product. Results indicate that although, compared to the GAX cycle, the HGAX cycle demonstrates a better performance from the view points of both the first and second laws of thermodynamics, the unit product cost for the HGAX cycle is higher. At the optimum operating conditions, the cost of unit product for the HGAX cycle is calculated as 180.5 $/GJ while the corresponding value for the SGAX cycle is obtained as 159.1 $/GJ. Also, the exergoeconomic analyses unfold that the condenser has the lowest exergoeconomic factor, f, in both the systems. In addition, inspired from nature, a new graphical plot is proposed to illustrate the fuel cost, product cost, capital investment and operating and maintenance cost and cost rates associated with the exergy destruction and losses within the system’s components
Seven-effect absorption refrigeration
DeVault, Robert C.; Biermann, Wendell J.
1989-01-01
A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.
Graphical abstract: To improve the performance of the air-cooled type absorption refrigeration, a novel non-adiabatic absorber has been applied in the cycle. Simulation results show that low grade energy is applicable for NH3/NaSCN and NH3/LiNO3 absorption refrigeration system under air cooling condition and relatively high system performance can be obtained. - Highlights: • We analyze an absorption refrigeration cycle driven by low grade energy. • Working fluids thermophysical property correlations are corrected. • Influence of non-adiabatic absorber on system performance is investigated. • We propose system operation parameters under air-cooled condition. - Abstract: An air-cooled type absorption refrigeration cycle using ammonia–lithium nitrate and ammonia–sodium thiocyanate solutions as working fluids are thermodynamically studied in this paper. In the case of many occasions especially small cooling capacity occasion where water cooling is restricted or inconvenient, application of conventional adiabatic absorbers in air-cooled type absorption refrigeration system has been studied by many investigators. Comparing to the adiabatic absorber, a novel air-cooled non-adiabatic absorber is applied to the absorption refrigeration system in this study to improve system performance. It is shown that, system performance has a significant improvement when temperatures of rich ammonia solution at the outlet of absorber decrease under the effect of the heat dissipation capacity of the non-adiabatic absorber. Another advantage is that heat load of the system heat exchangers including generator, solution heat exchanger and air-cooler, decreases with the solution temperature decrease at the outlet of the absorber under the same system cooling capacity condition, which brings benefits to the system cost reduction. Variation of system performance and other system operation parameters with generator temperature, absorption temperature and absorption efficiency has
In this work, the use of waste heat energy of jacket water in diesel engines of fishing ships was analysed for use as a heat source for absorption refrigeration systems. The thermodynamic simulation of an absorption refrigeration cycle with three different working fluid mixtures that use ammonia as a refrigerant was carried out. This analysis was assessed in terms of the cooling demand and cycle performance as a function of the evaporator, condenser and generator temperatures. Moreover, the need for rectifying the vapour stream leaving the generator was analysed together with the drag of the fraction of non-evaporated liquid to the absorber. The results show that the NH3/(LiNO3 + H2O) and NH3/LiNO3 fluid mixtures have higher values of COP as compared to NH3/H2O fluid mixture, the differences being more pronounced at low generation temperatures. If the activation temperature is set to 85 °C, the minimum evaporation temperatures that can be achieved are −18.8 °C for the cycle with NH3/LiNO3, −17.5 °C for the cycle with NH3/(LiNO3 + H2O) cycle and −13.7 °C for the NH3/H2O cycle at a condensing temperature of 25 °C. Also, for the NH3/(LiNO3 + H2O) fluid mixture, it has been demonstrated that the absorption refrigeration cycle can be operated without a distillation column and in this case the water content in the refrigerant stream entering the evaporator is less than 1.5% in weight at the operating conditions selected. - Highlights: •Ammonia absorption systems can provide refrigeration necessities for fishing ships. •Absorption refrigeration systems reduce the energy consumption of fishing ships. •The NH3/(LiNO3 + H2O) mixture is recommended for absorption refrigeration cycles
Recent Refrigeration Cycle Technologies for Household Refrigerators
Nagatomo, Shigemi
The household refrigerator is one of the most important and the biggest energy-consuming home appliances. This paper summarize recent refrigeration cycle developments in the field of domestic household refrigerators based on a survey of publications.
Highlights: • NH3–IL absorption cycles are modeled by COSMO-based Aspen simulations. • Proposed a priori computational approach is validated using experimental data. • Cycle performance was analyzed for conventional and task-specific ILs. • IL solvents with high NH3 absorption capacity improve the cycle performance. • Using IL mixtures is revealed as promising alternative in NH3 absorption applications. - Abstract: COSMO-based process simulations with Aspen Plus/Aspen HYSYS are used, for the first time, to a priori estimate the thermodynamic performance of ammonia absorption refrigeration cycles using ionic liquids as absorbents. This allows not only broadening the criteria set used to select/design ionic liquids with optimized properties to be used in that role, but also evaluating innovative strategies to improve the cycle’s performances. COSMO-RS method provides the information required for both creating the ionic liquid non-database components and specifying the COSMOSAC property model to perform Aspen Plus calculations. The computational procedure used here gives at the same time reasonable good property predictions of the vapor (refrigerant) and the condensed (ammonia + ionic liquid) phases as well as physically consistent estimations of the cycle’s performance under different conditions. Current results agree with those previously reported in the literature for several ionic liquid-based systems taken for comparison. In addition, task-specific ionic liquids, with improved properties for ammonia absorption, and also binary ionic liquid mixtures are considered in the analysis. It is obtained that ionic liquids showing higher ammonia absorption capacity among the considered absorbents simultaneously provide the best cycle’s performances. The cycle performances vary in relatively wide intervals depending on the ammonia concentration in the (refrigerant + absorbent) solutions. This behavior is strongly modulated by the ammonia absorption
Heat driven refrigeration cycle at low temperatures
HE Yijian; HONG Ronghua; CHEN Guangming
2005-01-01
Absorption refrigeration cycle can be driven by low-grade thermal energy, such as solar energy, geothermal energy and waste heat. It is beneficial to save energy and protect environment. However, the applications of traditional absorption refrigeration cycle are greatly restricted because they cannot achieve low refrigeration temperature. A new absorption refrigeration cycle is investigated in this paper, which is driven by low-grade energy and can get deep low refrigeration temperature. The mixture refrigerant R23+R134a and an absorbent DMF are used as its working fluid. The theoretical results indicate that the new cycle can achieve -62℃ refrigeration temperature when the generation temperature is only 160℃. This refrigeration temperature is much lower than that obtained by traditional absorption refrigeration cycle. Refrigeration temperature of -47.3℃ has been successfully achieved by experiment for this new cycle at the generation temperature of 157℃, which is the lowest temperature obtained by absorption refrigeration system reported in the literature up to now. The theoretical and experimental results prove that new cycle can achieve rather low refrigeration temperature.
Highlights: ► An absorption refrigeration cycle with an ejector device at the absorber inlet is presented. ► This cycle is able to reduce up to 9 °C the temperature of onset of refrigerant generation without extra energy consumption. ► At very low driving temperatures it allows increasing the cooling capacity. ► The ejector device proposed has a partially variable geometry and we study its influence on the cycle performances. -- Abstract: This paper presents a numerical model of an ejector-absorption (single-effect) refrigeration cycle with ammonia–lithium nitrate solution as working fluid, operating under steady-state conditions. In this cycle, the ejector is located at the absorber inlet replacing the solution expansion valve. The liquid–gas ejector entrains refrigerant vapor from the evaporator; this way the absorber pressure becomes higher than the evaporator pressure without any additional energy consumption. The objective of this numerical model is to evaluate the influence of the ejector geometry on the cycle performances and to determine the range of the heat source temperature in which it is convenient to use a practical ejector in the absorption cycle. The simulation is based on UA-ΔTlm models for separate heat transfer regions in a novel implementation using plate-type heat exchangers and this way the results are offered as a function of the external temperatures. This study focuses on evaluating the feasibility of an ejector whose nozzle area is adjustable while the rest of the ejector dimensions are fixed, thus being more feasible than complete variable geometry ejectors. The cycle performance is reported for different mixing tube constant diameters. Results of the simulation show that the use of an ejector allows, among others, to decrease the activation temperature approximately 9 °C in respect to the conventional single-effect absorption cycle and increasing the COP for moderate temperatures. The variable ejector nozzle geometry is of
A CAR AIR-CONDITIONING SYSTEM BASED ON AN ABSORPTION REFRIGERATION CYCLE USING SOLAR ENERGY
Prakash Kumar; Nitin Kumar; Vinod Sehrawat; Tarun Gupta
2016-01-01
The main purpose of this paper is to design and study an environment friendly vapour absorption refrigeration system of 0.2 TR capacity using ammonia (R-717) and water as the working fluids. In sunny days (summer season) vehicles becomes too much warm within a few hours a...
The Quantum Absorption Refrigerator
Levy, Amikam
2011-01-01
A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified, the cooling power Jc vanishes as Jc proportional to Tc^{alpha}, when Tc approaches the absolute zero, where alpha = 2 for a bath with flat spectral density and alpha = 3 for an Ohmic spectral density.
Quantum absorption refrigerator.
Levy, Amikam; Kosloff, Ronnie
2012-02-17
A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold, and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified; the cooling power J(c) vanishes as J(c) ∝ T(c)(α), when T(c)→0, where α=d+1 for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where d is the dimension of the bath. PMID:22401189
Ferreira, Maximino Joaquim Pina [KROMAV Engenharia, Rio de Janeiro, RJ (Brazil); Pinto, Luiz Antonio Vaz; Belchior, Carlos Rodrigues Pereira [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE)
2004-07-01
To produce cold from the heat seems a task unlikely or even impossible. However, absorption systems produce cooling from heat sources and it exist since the century XIX. In industrial places is very important to improve the energy use, even more in places where the activities involve great costs and incomes. Traditionally the alternatives conflict in the aspects of initial and operational costs. This paper describes the absorption systems operation and its main advantages and disadvantages, when compared to the traditional systems with compressor. The known fact that a vapor compressor system presents larger efficiency is not enough to validate it for all of the applications. In this sense, the initial and operational analysis of the costs of the absorption systems becomes interesting. In spite of, double effect absorption systems are demonstrating the evolution of the absorption cycle in order to obtain better performance. Turbo-generators and Turbo-compressors of the offshore platforms are thermal machines that reject great amount of heat in the exhaust gases. This heat is used for heating of water used in the Process Plant. The processes of separation of the mixture water-oil-gas from the well, for instance, use that heat. Even after the passage of the water in the Plant of Process, the residual heat is still enough for the use in absorption systems. A simulation is done using real data of an offshore platform. Two possible alternatives are compared under technical and economical aspects. Sensibility analysis is also performed in order to verify possible impacts of variations of electric power cost. (author)
冯丽洁; 付林; 张世钢; 江亿
2012-01-01
Applying the exergy efficiency and exergy loss analysis method, calculates and compares the exergy efficiency between the electric compression refrigeration cycle and the single-effect absorption refrigeration cycle and the exergy losses of each part of the two cycles under the typical condition. The results show that the exergy efficiency of the two cycles is basically the same when the generator temperature and the heat source temperature are appropriately selected; most part of exercy losses of the electric compression refrigeration cycle occur in the compressor, and most part of exercy losses of the single-effect absorption refrigeration cycle occur in the absorber and generator. Discusses the improving methods for the two cycles.%采用(火用)效率与炯损失分析方法,计算比较了电压缩式制冷循环与单效吸收式制冷循环的(火用)效率及两种制冷循环在典型工况下各环节的(火用)损失.结果表明,当采用合适的发生器温度和热源温度时,两种制冷循环的(火用)效率基本相同；电压缩式制冷循环的主要(火用)损失发生在压缩机环节,吸收式制冷循环的主要(火用)损失发生在吸收器和发生器.讨论了两种制冷循环的改进途径.
Superfluid thermodynamic cycle refrigerator
Swift, Gregory W.; Kotsubo, Vincent Y.
1992-01-01
A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.
Superfluid thermodynamic cycle refrigerator
A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of 3He in a single phase 3He-4He solution. The 3He in superfluid 4He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid 3He at an initial concentration in superfluid 4He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of 4He while restricting passage of 3He. The 3He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K. 12 figs
一个新的吸收-喷射复合制冷循环%A NOVEL COMBINED EJECTOR-ABSORPTION REFRIGERATION CYCLE
洪大良; 唐黎明; 邹云霞; 何一坚; 陈光明
2011-01-01
提出了一个新的吸收-喷射复合制冷循环.在新循环中,部分冷凝器出口的饱和液态制冷剂被冷剂泵加压到制冷剂在发生温度下对应的饱和压力,这股高压制冷剂液体在一个沸腾器里被加热成饱和高压蒸气后将预热器出口的过热制冷剂蒸气引射到冷凝压力.由于在新循环中发生压力可以比冷凝压力低,因此该系统可以利用较低品位的热量制取低温下的冷量.研究结果表明:新循环可以利用比传统两级吸收式制冷循环温度更低的热源,制取同一温度下的冷量.此外,在蒸发温度或发生温度较低时,新循环的COP比单效循环高得多；当发生温度或蒸发温度较高时,新循环和传统单效循环的COP相同.%To make refrigeration at low temperature with low-grade heat source, a novel combined ejector-absorption refrigeration cycle was proposed in this paper. In the new cycle, part of saturated liquid refrigerant from the condenser was pumped to saturated pressure of the refrigerant at generation temperature. This stream was heated into saturated vapor in a boiler and injected the superheating refrigerant vapor from a preheater to condenser pressure. Since the generation pressure is lower than condenser pressure in the new cycle, the system can make refrigeration at low temperature with low-grade heat source. The research results show that the generation temperature of the new cycle is even lower than that of the conventional two-stage absorption refrigeration cycle to make refrigeration at the same low temperature. In addition, the COP of the new cycle is much higher than that of single-effect cycle at the low refrigeration temperature and generation temperature. If the refrigeration temperature or the temperature of heat source is high enough, the COP of the new cycle is the same as that of the conventional single-effect cycle.
Satish K. Maurya
2014-03-01
Full Text Available Now a days the air conditioning system of cars is mainly uses “Vapour Compression Refrigerant System” (VCRS which absorbs and removes heat from the interior of the car that is the space to be cooled and rejects the heat to atmosphere. In vapour compression refrigerant system, the system utilizes power from engine shaft as the input power to drive the compressor of the refrigeration system, hence the engine has to produce extra work to run the compressor of the refrigerating system utilizing extra amount of fuel. This loss of power of the vehicle for refrigeration can be neglected by utilizing another refrigeration system i.e. a “Vapour Absorption Refrigerant System”. As well known thing about VAS that these machines required low grade energy for operation. Hence in such types of system, a physicochemical process replaces the mechanical process of the Vapour Compression Refrigerant System by using energy in the form of heat rather than mechanical work. This heat obtained from the exhaust of high power internal combustion engines.
This book gives a description of refrigerating engineering with introduction of refrigerating, abnormal refrigerating cycle and air compression refrigerator, refrigerant and simple steam compression refrigerating cycle, under-cooling cycle, plank cycle, multi-compression cycle, calculation for compressor and practice process of steam compression refrigerating, heat conduction, heat convection, heat radiation, compressor like booster, oil separator, gas purger, an vaporizer and the low-tension side device, operation of refrigerator, steam blast refrigerator, absorption refrigeration machine and application of refrigerating.
Graphical abstract: A methodology based on the second law of thermodynamic has been carried out in the analysis of an air-cooled type ammonia/salt absorption refrigeration system. Simulation results show that Low grade energy is applicable for NH3/NaSCN and NH3/LiNO3 absorption refrigeration system under air cooling condition and relatively high exergetic efficiency can be obtained. - Highlights: • We analyze an absorption refrigeration cycle driven by low grade energy. • Modified Methodology in entropy calculation is presented. • New exergy calculation method of ammonia/salt solution is presented. • Exergy analysis under air-cooled condition is carried out. • Influence of non-adiabatic absorber to exergetic efficiency is analyzed. - Abstract: This paper presents a methodology of exergy analysis for ammonia-lithium nitrate and ammonia-sodium thiocyanate absorption refrigeration cycle which applies a novel air-cooled type non-adiabatic absorber to improve both the coefficient of performance and exegetic efficiency of the system under air cooling condition. A modified entropy calculation method for NH3/NaSCN and NH3/LiNO3 solutions is presented in this literature and different results are obtained comparing to previous research. In addition to the variation of solution temperature and pressure from specific working state to the reference state, the variation of solution concentration, which was always neglected by previous researchers in ammonia/salt solution exergy calculation, has been taken into account while analyzing the least potential of ammonia/salt solution for doing useful work, and a corresponding approach for specific exergy calculation is presented. The effects of generator temperature, absorber outlet temperature, absorber efficiency and other system parameters on system exergetic efficiency have been discussed in this study. Analysis results indicate that relatively high system performance can be obtained by air-cooled type ammonia
Solar heating and cooling with absorption refrigeration
Montlló Casabayó, Gerard
2010-01-01
This project is focused on solar heating and cooling installations that use solar thermal energy to produce heat for domestic hot water or space heating, and cooling for air conditioning through absorption refrigeration cycle. The first part of the project is a literature review of said technology. The main components of such installations are described and results and conclusions from existing installations are reviewed. The second part is focused on designing, modelling and simula...
Quantum-enhanced absorption refrigerators.
Correa, Luis A; Palao, José P; Alonso, Daniel; Adesso, Gerardo
2014-01-01
Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators. PMID:24492860
Simulation of a new combined absorption-compression refrigeration cycle%一种新型吸收-压缩复合制冷循环模拟
唐鹏武; 陈光明; 唐黎明; 刘利华
2011-01-01
A program compiled by Visual Basic language was used to simulate a new combined absorption-compression refrigeration cycle for performance research, including the effect of generation temperature , evaporation temperature, condensation temperature, heat flux and refrigeration capacity on system performance which was compared with a conventional vapour compression refrigeration cycle. Simulation results show that when generation temperature increases, the coefficient of performance ( COP) of new cycle increases first and then decreases. When evaporation temperature or heat flux increases, the COP of new cycle increases. When condensation temperature or refrigeration capacity increases, the COP of new cycle decreases. Under most simulation conditions, the COP of new cycle can be 10% higher than that of conventional vapour compression refrigeration cycle. The new cycle can not only reduce air conditioning load greatly, but also provide the possibility of efficient utilization of low grade energy such as solar energy.%为了对一种新型吸收-压缩复合制冷循环的性能进行模拟,使用Visual Basic语言自行编制了一个程序.该程序模拟了发生温度、蒸发温度、冷凝温度、加热量、制冷量对系统性能的影响,并将其性能与传统蒸气压缩式制冷循环作了对比.模拟结果表明:当发生温度升高时,新循环的制冷系数先增大后减小；当蒸发温度升高或加热量增大时,新循环的制冷系数增大；当冷凝温度升高或制冷量增大时,新循环的制冷系数减小.在大部分假定工况下,新循环的制冷系数比传统蒸气压缩式循环的高10％以上.新循环的提出不仅能够大幅度减少空调电力负荷,还为太阳能等低品位能源的高效利用提供了可能.
Highlights: • TFE + [emim][BF4] (or [bmim][BF4]) absorption heat transformer cycles are studied. • Influence of various operating conditions on cycle’s performance is investigated. • Performance comparisons with H2O + LiBr and TFE + TEGDME cycles are done. • Enthalpy data for TFE + [emim][BF4] (or [bmim][BF4]) liquid mixtures are calculated. • TFE + [emim][BF4] (or [bmim][BF4]) cycles have higher gross temperature lift (GTL). - Abstract: A detailed thermodynamic performance analysis of a single-stage absorption heat transformer and double absorption heat transformer cycles using new working pairs composed of ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])) as absorbent and 2,2,2-trifluoroethanol (TFE) as refrigerant has been studied. Several performance indicators were used to evaluate and compare the performance of the cycles using the TFE + [emim][BF4] and TFE + [bmim][BF4] working pairs with the conventional H2O + LiBr and organic TFE + TEGDME working pairs. The obtained results show that the ionic liquid based working pairs are suitable candidates to replace the conventional H2O + LiBr working pairs in order to avoid the disadvantages associated with it mainly crystallization and corrosion and also they perform better (higher gross temperature lift) than TFE + TEGDME working pair at several operating conditions considered in this work
Quantum-enhanced absorption refrigerators
Correa, Luis A; Alonso, Daniel; Adesso, Gerardo
2014-01-01
Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step t...
Satish K. Maurya; Saurabh Awasthi
2014-01-01
Now a days the air conditioning system of cars is mainly uses “Vapour Compression Refrigerant System” (VCRS) which absorbs and removes heat from the interior of the car that is the space to be cooled and rejects the heat to atmosphere. In vapour compression refrigerant system, the system utilizes power from engine shaft as the input power to drive the compressor of the refrigeration system, hence the engine has to produce extra work to run the compressor of the refrigerating s...
Analysis of crystallization risk in double effect absorption refrigeration systems
Absorption refrigeration systems are an alternative to vapor compression ones in cooling and refrigeration applications. In comparison with single effect absorption units, double effect systems have improved performance. Also, they are more available commercially than the other multi effect absorption cycles. An important challenge in the operation of such systems is the possibility of crystallization within them. This is especially true in developing air-cooled absorption systems, which are attractive because cooling tower and associated installation and maintenance issues can be avoided. Therefore, distinguishing the working conditions that may cause crystallization can be useful in the design and control of these systems. In this paper a computational model has been developed to study and compare the effects of operating parameters on crystallization phenomena in three classes of double effect lithium bromide-water absorption refrigeration systems (series, parallel and reverse parallel) with identical refrigeration capacities. It is shown that the range of operating conditions without crystallization risks in the parallel and the reverse parallel configurations is wider than those of the series flow system. - Highlights: → We study crystallization of double effect absorption refrigeration systems. → We consider series, parallel and reverse parallel cycles. → We study the effect of operating conditions on crystallization. → We choose optimum distribution ratio for parallel and reverse parallel systems. → Crystallization possibility is low in parallel and reverse parallel cycles.
A class of internally irreversible refrigeration cycles
Ait-Ali, Mohand A.
1996-03-01
A Carnot-like irreversible refrigeration cycle is modelled with two isothermal and two non-adiabatic, irreversible processes. The generic source of internal irreversibility, measured by the Clausius inequality, is a general irreversibility term which could include any heat leaks into the Joule - Thompson expansion valve, the evaporator and compressor cold boxes. This cycle is optimized first for maximum refrigeration power and maximum refrigeration load, then for maximum coefficient of performance. Its performances are compared with those of the endoreversible refrigeration cycle, based on a propane stage of a classical cascade liquefaction cycle example. Both cycle models achieve optimum power and maximum refrigeration load at nearly the same refrigeration temperature, but only the coefficient of performance of the irreversible refrigeration cycle reaches a maximum. Moreover, its prediction of heat conductance allocation between evaporator and condenser appears to be not only more conservative, but also more realistic for actual design considerations of refrigeration cycles.
Highlights: ► Two novel fundamental concepts of the absorption refrigeration cycle were proposed. ► The interaction mechanism of compressor pressure increasing with other key-parameters was investigated. ► A set of optimal operating condition of hybrid refrigeration cycle was found. ► A simulation and investigation for R134a-DMF hybrid refrigeration cycle was performed. - Abstract: The absorption–compression hybrid refrigeration cycle has been considered as an effective approach to reduce the mechanical work consumption by using low-grade heat, such as solar energy. This work aims at studying the thermodynamic mechanism of the hybrid refrigeration cycle. Two fundamental concepts have been proposed, which are the ultimate refrigerating temperature (or the ultimate temperature lift) and the behavior turning. On the basis of that, the interaction mechanism of compressor pressure increasing with other key-parameters and the impact of compressor pressure increasing on the cycle performance have been investigated. The key-parameters include the concentration difference, the circulation ratio of working fluid, etc. The work points out that the hybrid refrigeration cycle performance varies with the change of compressor outlet pressure and depends on which one achieves dominance in the hybrid refrigeration cycle, the absorption sub-system or the compression sub-system. The behavior turning point during parameters changing corresponds to a maximum value of the heat powered coefficient of performance. In this case, the hybrid refrigeration cycle performance is optimal because the low-grade heat utilization is the most effective. In addition, to validate the theoretical analysis, a solar hybrid refrigeration cycle with R134a–DMF as working pair was simulated. The Peng–Robinson equation of state was adopted to calculate thermophysical properties when the reliability assessment of the prediction models on the available literature data of R134a–DMF system had been
Romero Paredes, H.; Ambriz, J.J.; Vargas, M.; Godinez, M.; Gomez, F.; Valdez, L.; Pantoja, G. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Departamento de Ingenieria de Procesos e Hidraulica, Mexico D. F. (Mexico)
1995-12-31
Day after day the electric power generation tends to be done in the most efficient way in order to diminish the generation costs and the rate of environmental pollution per KWh generated. This paper discusses the application of absorption refrigeration systems for the cooling of the air entering the compressor of a gas turbine in a combined cycle, in order to increase the mass air flow and with it the turbine output. The flows with remanent energy content that are not used in a combined cycle can be used for the operation of the absorption refrigeration system. This way, the required thermal energy for the cooling system is free. With this system it is possible to raise the gas turbine generation output from 5% to 25%. [Espanol] La generacion electrica dia con dia pretende realizarse de la manera mas eficiente posible con el objeto de disminuir los costos de generacion y la tasa de contaminacion ambiental por Kwh generado. En el presente trabajo se introduce la aplicacion de sistemas de refrigeracion por absorcion para el enfriamiento del aire de entrada al compresor de la turbina de gas de un ciclo combinado, con el objeto de aumentar el flujo masico del aire y con ello la potencia de salida de la turbina. Las corrientes con contenido remanente de energia termica que no se usan en una planta de ciclo combinado pueden servir para operar el sistema de refrigeracion por absorcion. De esta manera, la energia termica requerida para el sistema de enfriamiento es gratuita. Con este sistema es posible incrementar la potencia de generacion de la turbina de gas de 5 a 25%.
Artificial neural network analysis of triple effect absorption refrigeration systems
Hajizadeh Aghdam, A. [Department of Mechanical Engineering, Islamic Azad University (Iran, Islamic Republic of)], email: a.hajizadeh@iaukashan.ac.ir; Nazmara, H.; Farzaneh, B. [Department of Mechanical Engineering, University of Tabriz (Iran, Islamic Republic of)], email: h.nazmara@nioec.org, email: b_farzaneh_ms@yahoo.com
2011-07-01
In this study, artificial neural networks are utilized to predict the performance of triple effect series and parallel flow absorption refrigeration systems, with lithium bromide/water as the working fluid. Important parameters such as high generator and evaporator temperatures were varied and their effects on the performance characteristics of the refrigeration unit were observed. Absorption refrigeration systems make energy savings possible because they can use heat energy to produce cooling, in place of the electricity used for conventional vapour compression chillers. In addition, non-conventional sources of energy (such as solar, waste heat, and geothermal) can be utilized as their primary energy input. Moreover, absorption units use environmentally friendly working fluid pairs instead of CFCs and HCFCs, which affect the ozone layer. Triple effect absorption cycles were analysed. Results apply for both series and parallel flow systems. A relative preference for parallel-flow over series-flow is also shown.
Thermodynamic Analysis of the Irreversibilities in Solar Absorption Refrigerators
Emma Berrich Betouche
2016-03-01
Full Text Available A thermodynamic analysis of the irreversibility on solar absorption refrigerators is presented. Under the hierarchical decomposition and the hypothesis of an endoreversible model, many functional and practical domains are defined. The effect of external heat source temperature on the entropy rate and on the inverse specific cooling load (ISCL multiplied by the total area of the refrigerator A/Qe are studied. This may help a constructor to well dimension the solar machine under an optimal technico-economical criterion A/Qe and with reasonable irreversibility on the refrigerator. The solar concentrator temperature effect on the total exchanged area, on the technico-economical ratio A/Qe, and on the internal entropy rate are illustrated and discussed. The originality of these results is that they allow a conceptual study of a solar absorption refrigeration cycle.
Not all counterclockwise thermodynamic cycles are refrigerators
Dickerson, R. H.; Mottmann, J.
2016-06-01
Clockwise cycles on PV diagrams always represent heat engines. It is therefore tempting to assume that counterclockwise cycles always represent refrigerators. This common assumption is incorrect: most counterclockwise cycles cannot be refrigerators. This surprising result is explored here for quasi-static ideal gas cycles, and the necessary conditions for refrigeration cycles are clarified. Three logically self-consistent criteria can be used to determine if a counterclockwise cycle is a refrigerator. The most fundamental test compares the counterclockwise cycle with a correctly determined corresponding Carnot cycle. Other criteria we employ include a widely accepted description of the functional behavior of refrigerators, and a corollary to the second law that limits a refrigerator's coefficient of performance.
Ben Ezzine, N.; Garma, R.; Bellagi, A. [U.R. Thermique et Thermodynamique des Procedes Industriels, Ecole Nationale d' Ingenieurs de Monastir, Av. Ibn Jazzar, 5060 Monastir (Tunisia)
2010-05-15
Research on new working fluid for uses in absorption systems has been continued. The feasibility of a solar driven DAR using the mixture R124/DMAC as working fluid is investigated by numerical simulation. The cycle is simulated for two cooling medium temperatures, 27 C and 35 C, and four driving heat temperatures in the range [90 C-180 C]. The performance characteristics of this system is analyzed parametrically by computer simulation for a design cooling capacity of 1 kW. The results show that the system performance and the lowest (minimum) evaporation temperature reached are largely dependent upon the absorber efficiency and the driving temperature. It is shown that for solar applications this fluid mixture has a higher COP and may constitute an alternative to the conventional ammonia-water system. (author)
Orthogonal Design for Thermosyphon Operated in Absorption Refrigeration Cycles%小型吸收式制冷热虹吸泵的正交试验设计
王欣; 杨洪海; 张总辉; 杨丰畅; 叶志秦
2015-01-01
Thermosyphon was the core component of mini-type solar absorption refrigerator.Its efficiency decided the perform-ance of mini-type solar absorption refrigerator,and mostly depended on the capability of lift pipe.In this paper,according to the design requirements of lithium bromide absorption refrigeration cycle,thermosyphon theoretical model and performance simulation results,we has designed the experiment device and parts of thermosyphon visualization,successfully build and debug experiment device.Using orthogonal test method research factors such as heat,system pressure and immerson ratio influence on thermal si-phon pump performance,the analysis indicates that for the thermal siphon performance,the most important influencing factor is heat,the secondary factor is system pressure and the immerson ratio has minimal impat.%热虹吸泵是小型无泵溴化锂吸收式制冷机的核心部件，对制冷机的运行及工作性能起关键影响。本文根据溴化锂吸收式制冷循环的设计要求，以热虹吸泵理论模型和性能模拟结果为指导，进行了热虹吸泵沿程加热可视化试验装置的方案设计和部件设计，搭建并调试成功试验装置。采用正交试验法研究加热量、系统压力和沉浸比等因素对热虹吸泵提升性能的影响，分析得知，对于热虹吸泵提升性能影响最大的因素是加热量，次要影响因素是系统压力，沉浸比对其影响最小。
Highlights: • Ammonia/LiNO3 and ammonia/NaSCN combined ejector–absorption refrigeration cycles are analyzed. • The performance of combined cycles is compared to that of single effect cycles. • Ejector is used to facilitate pressure recovery of the absorber and improve mixing. • For low generator temperatures combined cycles have better performance. • Influence of various operating parameters on performance of cycles is investigated. - Abstract: Alternatives to ammonia/water absorption refrigeration cycles that have no need for purification include ammonia/LiNO3 and ammonia/NaSCN cycles. Similar to the other absorption refrigeration cycles they have low coefficients of performance and exergy efficiencies at low generator temperatures. Combined single effect cycles can reduce this problem. In these cycles the solution expansion valve is replaced with an ejector to allow for pressure recovery from the absorber and to enhance mixing of the weak solution and refrigerant vapor from the evaporator. Simulations are used to examine the influence of various operating parameters on performance and the possibility of crystallization in these cycles, and to compare their performances with single effect cycles. It is shown that the combined cycles have better performance than single effect ones at low generator temperatures
A resorption cycle for the cogeneration of electricity and refrigeration
Graphical abstract: A novel resorption cycle driven by low grade heat for cogeneration of electricity and refrigeration is studied. The cycle features in high exergy efficiency, very little or no ammonia liquid inside and simple structure. Highlights: ► A resorption cogeneration cycle for electricity and refrigeration is proposed. ► The cycle improved refrigeration COP by 10 times compared with Goswami cycle. ► The highest exergy efficiency of the cogeneration cycle is as high as 0.9. ► The cycle also features in safety and simple structure. - Abstract: This paper describes a novel resorption cycle driven by the low grade heat for the cogeneration of electricity and refrigeration, which is based on ammonia adsorption refrigeration technology. The presented cycle features a variable endothermic process which stands for higher adaptability if compared with the traditional Rankine cycle, very little or no ammonia liquid in the system which is a safety feature, solid adsorbents inside the beds, and simple structure for the fact of no rectifying equipment and circulation pumps required by the working fluids. This cycle can be utilised for the heat source with the temperature higher than 100 °C, and it has an electricity generation exergy efficiency of up to 0.69 and a refrigeration coefficient of performance (COP) of up to 0.77. If compared with the Goswami cycle, which is established based on the absorption Kalina cycle for the cogeneration of electricity and refrigeration, the novel resorption cycle kept the merit of the high exergy efficiency for electricity generation, meanwhile, it overcame the limitation of the low refrigeration coefficient of performance (COP) of Goswami cycle, and improved the COP by 10 times. The optimum overall exergy efficiency is as high as 0.9, which is 40–60% improved compared with the Goswami cycle under the same working conditions
The Absorption Refrigerator as a Thermal Transformer
Herrmann, F.
2009-01-01
The absorption refrigerator can be considered a thermal transformer, that is, a device that is analogous to the electric transformer. The analogy is based on the correspondence between the extensive quantities, entropy and electric charge and the intensive variables, temperature and electric potential. (Contains 1 footnote and 6 figures.)
The absorption refrigerator as a thermal transformer
Herrmann, F [Abteilung fuer Didaktik der Physik, Universitaet Karlsruhe (Germany)
2009-03-15
The absorption refrigerator can be considered a thermal transformer, that is, a device that is analogous to the electric transformer. The analogy is based on the correspondence between the extensive quantities, entropy and electric charge and the intensive variables, temperature and electric potential.
Benhmidene Ali
2011-01-01
Full Text Available The mathematical model will be able to predict the operated condition (required tube diameters, heat input and submergence ratio….. That will result in a successful bubble pump design and hence a refrigeration unit. In the present work a one-dimensional two-fluid model of boiling mixing ammonia-water under constant heat flux is developed. The present model is used to predict the outlet liquid and vapor velocities and pumping ratio for different heat flux input to pump. The influence of operated conditions such as: ammonia fraction in inlet solution and tube diameter on the functioning of the bubble pump is presented and discussed. It was found that, the liquid velocity and pumping ratio increase with increasing heat flux, and then it decreases. Optimal heat flux depends namely on tube diameter variations. Vapour velocity increases linearly with increasing heat flux under designed conditions.
This paper continues and concludes the study of the proposed high-efficiency combined desalination and refrigeration system based on the LiBr-H2O absorption cycle introduced in the paper that is Part 1 [Proposal and analysis of a high-efficiency combined desalination and refrigeration system based on the LiBr-H2O absorption cycle--Part 1: System configuration and mathematical model. Energy Convers Manage 2010;52:220-7], in which also the mathematical model and its validation are presented in detail. Specifically, the thermal performance of the proposed ARHP-MEE (absorption refrigeration heat pump integrated with a multi-effect evaporation desalter) system, is analyzed, and a parametric sensitivity analysis and a rough economic evaluation are carried out, to clarify and quantify the performance of this combined refrigeration and water system. Typically, driving steam with saturation pressure of 0.15-0.35 MPa and corresponding saturation temperature of 111.4-138.9 oC is applied to run the system. The combined system has good internal synergy, as demonstrated by an energy saving rate of 42% compared with the separate refrigeration-only and water-only systems in a base-case study. The refrigeration-heat cogenerated ARHP subsystem is the main reason for the synergy, with a coefficient of performance of about 1.6 and exergy efficiency above 60% when driven by 0.25 MPa saturated steam. A rough economic analysis indicates qualitatively that there is no penalty in capital equipment for an ARHP-MEE system when compared with the two single-purpose systems, and the higher energy utilization rate of the system makes the energy/operating cost lower.
Design and Simulation of an Absorption Diffusion Solar Refrigeration Unit
Chaouachi, B; S. Gabsi
2007-01-01
The purpose of this study was the design and the simulation of an absorption diffusion refrigerator using solar as source of energy, for domestic use. The design holds account about the climatic conditions and the unit cost due to technical constraints imposed by the technology of the various components of the installation such as the solar generator, the condenser, the absorber and the evaporator. Mass and energy conservation equations were developed for each component of the cycle and solve...
YAKAR, Gülay; KARABACAK, Rasim; Burçin DEDA ALTAN
2005-01-01
In this study, energy and exergy analysis of absorption refrigeration system using LiBr- water and mechanical compression refrigeration system using R134-a were performed at different evaporation temperatures. The results are presented in tables and figures.
Hossein Rezvantalab; Seyyed Abdolreza Fazeli; Farshad Kowsary
2011-01-01
In this study, a new combined power and refrigeration cycle is proposed, which combines the Rankine and absorption refrigeration cycles. Using a binary ammonia-water mixture as the working fluid, this combined cycle produces both power and refrigeration output simultaneously by employing only one external heat source. In order to achieve the highest possible exergy efficiency, a secondary turbine is inserted to expand the hot weak solution leaving the boiler. Moreover, an artificial neural ne...
Short Time Cycles of Purely Quantum Refrigerators
Feldmann, Tova
2012-01-01
Four stroke Otto refrigerator cycles with no classical analogue are studied. Extremely short cycle times with respect to the internal time scale of the working medium characterize these refrigerators. Therefore these cycles are termed sudden. The sudden cycles are characterized by the stable limit cycle which is the invariant of the global cycle propagator. During their operation the state of the working medium possesses significant coherence which is not erased in the equilibration segments due to the very short time allocated. This characteristic is reflected in a difference between the energy entropy and the Von Neumann entropy of the working medium. A classification scheme for sudden refrigerators is developed allowing simple approximations for the cooling power and coefficient of performance.
Anon.
2009-04-15
Absorption and adsorption techniques make it possible to provide cold water at a typical air conditioning level by means of solar heat. Often, absorption refrigerators using lithium bromide dissolved in water as absorption agent and water as refrigerant are used for this purpose. (orig.)
Exergoeconomic Analysis of a Refrigeration Cycle
Durriye Bilge; Galip Temir
2004-01-01
The exergoeconomic theory is applied to a two stage vapour compression refrigeration cycle. An exergy-aided cost analysis, taking into account pressure drops and heat gain/loss for all of the components in the refrigeration system as well as the pipe connections, has been made. Exergoeconomic factors, showing whether the monetary expenditures mostly originate from capital investment and Operating and Maintenance (O&M) costs or from exergy destruction and exergy loss, are found and shown i...
Automotive exhaust gas flow control for an ammonia–water absorption refrigeration system
A considerable part of the energy generated by an automotive internal combustion engine is wasted as heat in the exhaust system. This wasted heat could be recovered and applied to power auxiliary systems in a vehicle, contributing to its overall energy efficiency. In the present work, the experimental analysis of an absorption refrigeration system was performed. The exhaust system of an automotive internal combustion engine was connected to the generator element of an absorption refrigeration system. The performance of the absorption refrigerator was evaluated as a function of the supplied heat. The use of a control strategy for the engine exhaust gas mass flow rate was implemented to optimize the system. Exhaust gas flow was controlled by step-motor actuated valves commanded by a microcontroller in which a proportional-integral control scheme was implemented. Information such as engine torque, speed, key temperatures in the absorption cycle, as well as internal temperatures of the refrigerator was measured in a transient regime. The results indicated that the refrigeration system exhibited better performance when the amount of input heat is controlled based on the temperature of the absorption cycle generator. It was possible to conclude that, by dynamically controlling the amount of input heat, the utilisation range of the absorption refrigeration system powered by exhaust gas heat could be expanded in order to incorporate high engine speed operating conditions. - Highlights: •An absorption refrigerator was driven by automotive exhaust gas heat. •A system for controlling the refrigeration system heat input was developed. •Excessive exhaust gas heat leads to ineffective operation of the refrigerator. •Control of refrigerator's generator temperature led to better performance. •The use of exhaust gas was possible for high engine speeds
Emma Berrich Betouche; Ali Fellah; Ammar Ben Brahim; Fethi Aloui; Michel Feidt
2016-01-01
A thermodynamic approach based on the hierarchical decomposition which is usually used in mechanical structure engineering is proposed. The methodology is applied to an absorption refrigeration cycle. Thus, a thermodynamic analysis of the performances on solar absorption refrigerators is presented. Under the hypothesis of an endoreversible model, the effects of the generator, the solar concentrator and the solar converter temperatures, on the coefficient of performance (COP), are presented an...
Coefficient of Performance Enhancement of Refrigeration Cycles
Eng. Naser R. M. AL-Ajmi
2015-03-01
Full Text Available Refrigerator is one of the home appliance utilizing mechanical vapor compression cycle in its process. Performance of the systems become the main issue and many researches are still ongoing to evaluate and improve the efficiency of any used system. Therefore, this paper presents an experimental investigation of the performance of the refrigeration cycles. A small rrefrigerator is used as the test rig. The Coefficient of Performance (COP is studied by using different condenser designs and under varying evaporator loads. Three condenser designs are used in present work. These condensers are regular condenser of domestic refrigerator, condenser with copper plain tubes (Cond.1 and condenser with copper tubes welded with stainless steel flat plate (Cond.2. pressures and temperatures measurements of each point in the refrigeration cycle are collected in order to evaluate the refrigerator performance. The results showed that the average COP of Cond.1 and Cond.2 are increased up to 20 % and 14% respectively more than regular condenser design under no load. The evaporator load effects on the machine performance, where the COP of the machine increases with the increase of the evaporator load.
Thermo-economic optimization of an endoreversible four-heat-reservoir absorption-refrigerator
Based on an endoreversible four-heat-reservoir absorption-refrigeration-cycle model, the optimal thermo-economic performance of an absorption-refrigerator is analyzed and optimized assuming a linear (Newtonian) heat-transfer law applies. The optimal relation between the thermo-economic criterion and the coefficient of performance (COP), the maximum thermo-economic criterion, and the COP and specific cooling load for the maximum thermo-economic criterion of the cycle are derived using finite-time thermodynamics. Moreover, the effects of the cycle parameters on the thermo-economic performance of the cycle are studied by numerical examples
Design and Simulation of an Absorption Diffusion Solar Refrigeration Unit
B. Chaouachi
2007-01-01
Full Text Available The purpose of this study was the design and the simulation of an absorption diffusion refrigerator using solar as source of energy, for domestic use. The design holds account about the climatic conditions and the unit cost due to technical constraints imposed by the technology of the various components of the installation such as the solar generator, the condenser, the absorber and the evaporator. Mass and energy conservation equations were developed for each component of the cycle and solved numerically. The obtained results showed, that the new designed mono pressure absorption cycle of ammonia was suitable well for the cold production by means of the solar energy and that with a simple plate collector we can reach a power, of the order of 900 watts sufficient for domestic use.
Energy and exergy analyses of the diffusion absorption refrigeration system
This paper describes the thermodynamic analyses of a DAR (diffusion absorption refrigeration) cycle. The experimental apparatus is set up to an ammonia–water DAR cycle with helium as the auxiliary inert gas. A thermodynamic model including mass, energy and exergy balance equations are presented for each component of the DAR cycle and this model is then validated by comparison with experimental data. In the thermodynamic analyses, energy and exergy losses for each component of the system are quantified and illustrated. The systems' energy and exergy losses and efficiencies are investigated. The highest energy and exergy losses occur in the solution heat exchanger. The highest energy losses in the experimental and theoretical analyses are found 25.7090 W and 25.4788 W respectively, whereas those losses as to exergy are calculated 13.7933 W and 13.9976 W. Although the values of energy efficiencies obtained from both the model and experimental studies are calculated as 0.1858, those values, in terms of exergy efficiencies are found 0.0260 and 0.0356. - Highlights: • The diffusion absorption refrigerator system is designed manufactured and tested. • The energy and exergy analyses of the system are presented theoretically and experimentally. • The energy and exergy losses are investigated for each component of the system. • The highest energy and exergy losses occur in the solution heat exchanger. • The energy and the exergy performances are also calculated
Combined Cycle for Power Generation and Refrigeration Using Low Temperature Heat Sources
Vijay Chauhan; P. Anil Kishan; Sateesh Gedupudi
2014-01-01
A combined refrigeration and power cycle, which uses ammonia-water as the working fluid, is proposed by combining Rankine and vapour absorption cycles with an advantage of varying refrigeration capacity to power output ratio. The study investigates the usage of low temperature heat sources for the cycle operation. Results of parametric analysis are presented, which show the scope for optimization. Results of thermodynamic optimization of the cycle for second law efficiency performed using gen...
Small quantum absorption refrigerator with reversed couplings.
Silva, Ralph; Skrzypczyk, Paul; Brunner, Nicolas
2015-07-01
Small quantum absorption refrigerators have recently attracted renewed attention. Here we present a missing design of a two-qubit fridge, the main feature of which is that one of the two machine qubits is itself maintained at a temperature colder than the cold bath. This is achieved by "reversing" the couplings to the baths compared to previous designs, where only a transition is maintained cold. We characterize the working regime and the efficiency of the fridge. We demonstrate the soundness of the model by deriving and solving a master equation. Finally, we discuss the performance of the fridge, in particular the heat current extracted from the cold bath. We show that our model performs comparably to the standard three-level quantum fridge and thus appears appealing for possible implementations of nanoscale thermal machines. PMID:26274153
Stirling-Cycle Refrigerator Containing Piezoelectric Pumps
Jalink, Antony, Jr.; Hellbaum, R. F.
1995-01-01
Advanced Stirling-cycle cryogenic apparatus suitable for cooling sensitive infrared detectors to very low temperatures. Working fluid in refrigerator helium. Working fluid compressed and circulated by three piezoelectrically actuated diaphragm pumps offering advantages of greater reliability, relative simplicity, and lower cost.
Performance of an irreversible quantum refrigeration cycle
He Ji-Zhou; Ouyang Wei-Pin; Wu Xin
2006-01-01
A new model of a quantum refrigeration cycle composed of two adiabatic and two isomagnetic field processes is established. The working substance in the cycle consists of many non-interacting spin-1/2 systems. The performance of the cycle is investigated, based on the quantum master equation and semi-group approach. The general expressions of several important performance parameters, such as the coefficient of performance, cooling rate, and power input, are given. It is found that the coefficient of performance of this cycle is in the closest analogy to that of the classical Carnot cycle. Furthermore, at high temperatures the optimal relations of the cooling rate and the maximum cooling rate are analysed in detail. Some performance characteristic curves of the cycle are plotted, such as the cooling rate versus the maximum ratio between high and low "temperatures" of the working substances, the maximum cooling rate versus the ratio between high and low "magnetic fields" and the "temperature" ratio between high and low reservoirs. The obtained results are further generalized and discussed, so that they may be directly applied to describing the performance of the quantum refrigerator using spin-J systems as the working substance. Finally, the optimum characteristics of the quantum Carnot and Ericsson refrigeration cycles are derived by analogy.
Energy and Exergy Analysis of Vapour Absorption Refrigeration Cycle—A Review
Kanabar, Bhaveshkumar Kantilal; Ramani, Bharatkumar Maganbhai
2016-02-01
In recent years, an energy crisis and the energy consumption have become global problems which restrict the sustainable growth. In these scenarios the scientific energy recovery and the utilization of various kinds of waste heat become very important. The waste heat can be utilized in many ways and one of the best practices is to use it for vapour absorption refrigeration system. To ensure efficient working of absorption cycle and utilization of optimum heat, exergy is the best tool for analysis. This paper provides the comprehensive picture of research and development of absorption refrigeration technology, practical and theoretical analysis with different arrangements of the cycle.
Energy and Exergy Analysis of Vapour Absorption Refrigeration Cycle—A Review
Kanabar, Bhaveshkumar Kantilal; Ramani, Bharatkumar Maganbhai
2016-07-01
In recent years, an energy crisis and the energy consumption have become global problems which restrict the sustainable growth. In these scenarios the scientific energy recovery and the utilization of various kinds of waste heat become very important. The waste heat can be utilized in many ways and one of the best practices is to use it for vapour absorption refrigeration system. To ensure efficient working of absorption cycle and utilization of optimum heat, exergy is the best tool for analysis. This paper provides the comprehensive picture of research and development of absorption refrigeration technology, practical and theoretical analysis with different arrangements of the cycle.
Hossein Rezvantalab
2011-01-01
Full Text Available In this study, a new combined power and refrigeration cycle is proposed, which combines the Rankine and absorption refrigeration cycles. Using a binary ammonia-water mixture as the working fluid, this combined cycle produces both power and refrigeration output simultaneously by employing only one external heat source. In order to achieve the highest possible exergy efficiency, a secondary turbine is inserted to expand the hot weak solution leaving the boiler. Moreover, an artificial neural network (ANN is used to simulate the thermodynamic properties and the relationship between the input thermodynamic variables on the cycle performance. It is shown that turbine inlet pressure, as well as heat source and refrigeration temperatures have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. In addition, the results of ANN are in excellent agreement with the mathematical simulation and cover a wider range for evaluation of cycle performance.
Exergoeconomic Analysis of a Refrigeration Cycle
Durriye Bilge
2004-01-01
Full Text Available The exergoeconomic theory is applied to a two stage vapour compression refrigeration cycle. An exergy-aided cost analysis, taking into account pressure drops and heat gain/loss for all of the components in the refrigeration system as well as the pipe connections, has been made. Exergoeconomic factors, showing whether the monetary expenditures mostly originate from capital investment and Operating and Maintenance (O&M costs or from exergy destruction and exergy loss, are found and shown in the form of tables. The true cost of the heat drawn from cold room, which is the product of a refrigeration sytem, has been calculated. In this way, it will be possible to reflect the cost of cold room storage to the market price of the goods completely and precisely.
Gülay YAKAR
2005-02-01
Full Text Available In this study, energy and exergy analysis of absorption refrigeration system using LiBr- water and mechanical compression refrigeration system using R134-a were performed at different evaporation temperatures. The results are presented in tables and figures.
A Cold Cycle Dilution Refrigerator for Space Applications Project
National Aeronautics and Space Administration — The cold cycle dilution refrigerator is a continuous refrigerator capable of cooling to temperatures below 100 mK that makes use of a novel thermal magnetic pump....
Modelling and data validation for the energy analysis of absorption refrigeration systems
Martínez Maradiaga, David Estéfano
2013-01-01
Data validation and reconciliation techniques have been extensively used in the process industry to improve the data accuracy. These techniques exploit the redundancy in the measurements in order to obtain a set of adjusted measurements that satisfy the plant model. Nevertheless, not many applications deal with closed cycles with complex connectivity and recycle loops, as in absorption refrigeration cycles. This thesis proposes a methodology for the steady-state data validation of absorption ...
An innovative ecological hybrid refrigeration cycle for high power refrigeration facility
Cyklis Piotr; Janisz Karina
2015-01-01
Searching for new refrigerants is one of the most significant scientific problems in refrigeration. There are ecological refrigerants commonly known: H2O and CO2. H2O and CO2 known as natural refrigerants, but they have problems:a high freezing point of H2O and a low triple point of CO2. These problems can be solved by the application of a hybrid sorption-compression refrigeration cycle. The cycle combines the application possibility of H2O in the high temperature sorption stage and the low t...
PECULIARITIES OF THE IDEALIZED CYCLES OF VAPOR COMPRESSOR REFRIGERATING MACHINES
Вассерман, А. А.; Лавренченко, Г. К.; Слынько, А. Г.
2014-01-01
Efficiency of the idealized cycles of vapor compressor refrigerating machines with adiabatic or isothermal compression of refrigerantwas investigated. To these cycles concern cycles with adiabatic compression of steam without regeneration (S-cycle) and with limiting regeneration (SR-cycle), and also with isothermal compression and limiting regeneration (T-cycle). Three characteristics of cycles are compared: refrigerating coefficient of performance e, specific-volume cooling capacity qv and t...
Transitions between refrigeration regions in extremely short quantum cycles
Feldmann, Tova; Kosloff, Ronnie
2016-05-01
The relation between the geometry of refrigeration cycles and their performance is explored. The model studied is based on a coupled spin system. Small cycle times, termed sudden refrigerators, develop coherence and inner friction. We explore the interplay between coherence and energy of the working medium employing a family of sudden cycles with decreasing cycle times. At the point of maximum coherence the cycle changes geometry. This region of cycle times is characterized by a dissipative resonance where heat is dissipated both to the hot and cold baths. We rationalize the change of geometry of the cycle as a result of a half-integer quantization which maximizes coherence. From this point on, increasing or decreasing the cycle time, eventually leads to refrigeration cycles. The transition point between refrigerators and short circuit cycles is characterized by a transition from finite to singular dynamical temperature. Extremely short cycle times reach a universal limit where all cycles types are equivalent.
Thermodynamic Analysis of the Irreversibilities in Solar Absorption Refrigerators
Emma Berrich Betouche; Ali Fellah; Ammar Ben Brahim; Fethi Aloui; Michel Feidt
2016-01-01
A thermodynamic analysis of the irreversibility on solar absorption refrigerators is presented. Under the hierarchical decomposition and the hypothesis of an endoreversible model, many functional and practical domains are defined. The effect of external heat source temperature on the entropy rate and on the inverse specific cooling load (ISCL) multiplied by the total area of the refrigerator A/Qe are studied. This may help a constructor to well dimension the solar machine under an optimal tec...
Closed cycle refrigeration for routine magnetotransport measurements
Gunawardana, Binuka; Ye, Tianyu; Wegscheider, Werner; Mani, Ramesh
2015-03-01
Condensed matter physics is often interested in the behavior of materials at very low temperatures. Low temperatures have traditionally been realized using liquid helium. However, the recent scarcity of liquid helium and the rapid rise in its cost has encouraged the development of alternative approaches, based on closed cycle refrigerators, for realizing low temperatures. Here, we convey our experiences in developing a home-made, low cost, variable temperature closed cycle refrigeration system for routine magnetotransport measurements down to 10K, and present measurements obtained with this system relating to the electronic properties of the high mobility GaAs/AlGaAs 2D semiconductors system. The setup was constructed to examine 0.5cm × 0.5cm semiconductor chips including up to 49 leads and reach ~ 10K within 3 hours. A computer controlled data acquisition system was assembled to collect resistivity and Hall effect data, and extract the carrier Hall mobility and density as a function of the temperature.
Research on performance of mixed absorption refrigeration for solar air-conditioning
2008-01-01
A novel lithium bromide/water mixed absorption refrigeration cycle that is suitable for the utilization of solar air-conditioning and can overcome the drawbacks of low system overall efficiency of traditional solar absorption refrigeration air-condition systems is presented.The accessorial high pressure generator was added in the cycle.The lithium bromide solution flowing out from the high pressure generator was mixed with the solution from the low pressure absorber to increase lithium bromide solution concentration and decrease pressure in the high pressure absorber.The performance of a mixed absorption refrigeration cycle was analyzed.The theoretical analysis shows that the highest COP is 0.61,while the highest available temperature difference of heat resource is 33.2℃.The whole coefficient of performance of the solar air-conditioning using mixed absorption cycle is 94.5% higher than that of two-stage absorption.The advantages of solar air-conditioning can be markedly made use of by the cycle.
任秀宏; 王林
2012-01-01
A new type of solar-driven air-cooled NH3H2O absorption refrigeration cycle was proposed. It have rectification e-quipment for purifying ammonia steam and recovers heat from rectifier and absorber. By these realizing small size, air - cooled and the effective use of solar energy. So the coefficient of performance (COP) is increased compared with traditional models. Based on energy conservation, solution mass conservation and ammonia components mass conservation,the thermodynamic math-ematic model of each component is established. Then cycle performance is calculated by writing programs. The effect of main operation parameters(heat source temperature, evaporating temperature,condensing temperature)on the coefficient of performance ( COP) was studied, laying the foundation for optimization design and operation of refrigeration system.%提出一种新型太阳能风冷氨水吸收式制冷循环系统,该系统设置精馏器提纯氨蒸汽,并有效回收精馏器精馏热及中温吸收器吸收热,实现对太阳能的有效利用以及机组风冷化和小型化,与传统系统相比其系统性能系数(COP)显著提高.基于能量守恒、溶液质量守恒和氨组分质量守恒建立系统各部件热力学数学模型,在此基础上编写程序对系统循环特性进行理论计算,分析热源温度、蒸发温度、冷凝温度等参数对系统COP的影响,为系统优化设计及建立最优运行方案提供理论支持.
Simultaneous production of fresh water and refrigeration are often required, e.g. in warm-climate water-deficient regions, and this study is a proposal and analysis of an efficient way of producing both of them by consuming mainly low-grade heat. After introducing the configuration choice methodology, a combined refrigeration and water system, ARHP-MEE (absorption refrigeration heat pump and multi-effect evaporation desalter), which is the integration of a LiBr-H2O refrigeration unit, a LiBr-H2O heat pump, and a low-temperature multi-effect evaporation desalination unit, is proposed, and the mathematical model is presented and validated. The model serves for conducting a performance analysis of the combined system, reported in Part 2 of this two-part paper.
Performance Enhancement Technology for the Vapor Compression Refrigeration Cycle
Man'o, Tatsunori
High efficiency refrigerator have been developed. For energy saving that is concerned with against global warming, performance enhancement of vapor compression refrigerator is required in field of air condition and refrigeration facility. In this paper, a review of recent performance enhancement technologies for the vapor compression refrigeration cycle is presented. This review contains high performance cycles of large sized centrifugal chiller, small to middle sized chiller and packaged air conditioner. Moreover, researches and developments of the refrigeration cycle recovering throttling loss, applications of ejector to boost in compressor suction pressure and to recirculate vapor refrigerant in the evaporator for heat transfer enhancement, and applications of expander to employ expansion work for compression work, are reviewed.
Refrigeration Carnot-type cycle based on isothermal vapour compression
Meunier, F. [Laboratoire du Froid EA 21, Cnam-IFFI, 292 rue Saint-Martin (France)
2006-01-01
A refrigeration Carnot-type cycle based on isothermal compression and two reversible expansions is proposed. Although ideal, this cycle is close to a realistic one which could be designed with existing hardware. (author)
Modeling And Experimental Analysis Of Generator In Vapour Absorption Refrigeration System
Christy V Vazhappilly
2013-09-01
Full Text Available A breadboard prototype of an absorption system for refrigeration using heat from the exhaust-gases is to be designed, built and tested. In the commercial vapour absorption refrigeration system a heating coil generator system has been employed to vaporize the ammonia efrigerant. In the present work, the heating coil generator system has been replaced by the frame plate type heat exchanger. The exhaust gases from the IC engine have been utilized to vaporize the ammonia refrigerant. The available heat in the exhaust gases has to be estimated based on actual I.C-Engine driving cycles. The frame plate type heat exchanger has to be modeled and flow analysis inside the heat exchanger has to be analyzed. In addition, the recoverable energy of the exhaust gases is to be analyzed for representative Internal Combustion Engine.
New Regenerative Cycle for Vapor Compression Refrigeration
Mark J. Bergander
2005-08-29
second step of compression. In the proposed system, the compressor compresses the vapor only to 50-60% of the final pressure, while the additional compression is provided by a jet device using internal potential energy of the working fluid flow. Therefore, the amount of mechanical energy required by a compressor is significantly reduced, resulting in the increase of efficiency (either COP or EER). The novelty of the cycle is in the equipment and in the way the multi-staging is accomplished. The anticipated result will be a new refrigeration system that requires less energy to accomplish a cooling task. The application of this technology will be for more efficient designs of: (1) Industrial chillers, (2) Refrigeration plants, (3) Heat pumps, (4) Gas Liquefaction plants, (5) Cryogenic systems.
Applying design of experiments to a compression refrigeration cycle
Nuno Ricardo Costa
2015-12-01
Full Text Available Refrigeration cycles are used in a large diversity of industrial and domestic (residential and non-residential equipment and their efficiency depend on several variables. To better understanding of how controllable variables impact on a compression refrigeration cycle efficiency, statistically designed experiments were conducted and data were analyzed. A quadratic polynomial model was fitted to Coefficient of Performance and variable settings to maximize cycle efficiency identified. Results give confidence to use the illustrated approach for refrigeration cycle design and operation improvement purposes.
Cavity-enhanced absorption for optical refrigeration
Seletskiy, Denis V; Sheik-Bahae, Mansoor
2009-01-01
A 20-fold increase over the single path optical absorption is demonstrated with a low loss medium placed in a resonant cavity. This has been applied to laser cooling of Yb:ZBLAN glass resulting in 90% absorption of the incident pump light. A coupled-cavity scheme to achieve active optical impedance matching is analyzed.
Boukhchana, Yasmina; Fellah, Ali; Ben Brahim, Ammar [Unite de Recherche, Thermodynamique Appliquee (99/UR/11-21), Universite de Gabes, Ecole Nationale d' ingenieurs, 6072 Gabes (Tunisia)
2011-01-15
No abstract prepared. [French] La modelisation en regime dynamique de la phase generation d'une installation frigorifique a absorption solaire a fonctionnement intermittent utilisant le couple ammoniac/eau a ete elaboree. L'etude basee sur l'intermittence du fonctionnement a permis d'elaborer, a travers les bilans matieres et thermiques, un modele thermodynamique reliant les temperatures, les debits et les fractions massiques dans les differents compartiments. Des journees ensoleillees representatives des quatre saisons de l'annee ont ete considerees. Les variations du taux d'ensoleillement, des temperatures et des concentrations ont ete explorees. Les resultats ont montre, moyennant les hypotheses adoptees en particulier a pression de fonctionnement constante, que la demarche proposee a permis d'avoir une temperature de generation autour de 135 C et une temperature de condensation de 60 C. Ces temperatures sont atteinte par l'adaptation de la convection naturelle a l'air pour le fonctionnement du condenseur. (orig.)
Optimization of a solar driven absorption refrigerator in the transient regime
Highlights: ► Dynamic behavior of a solar absorption refrigerator endoreversible model. ► Using the principles of classical thermodynamics, mass and heat transfers. ► Minimizing heat exchange time to reach maximum performances. ► Major influence of the collector temperature on the model’s characteristics. ► Analogous effects of both the thermal load and the thermal conductance. -- Abstract: This contribution deals with the theoretical study in dynamic mode of an absorption refrigerator endoreversible model. The system is a cold generating station driven by solar energy. The main elements of the cycle are a refrigerated space, an absorption refrigerator and a solar collector form. A mathematical model is developed. It combines the classical thermodynamics and mass and heat transfers principles. The numerical simulation is made for different operating and conceptual conditions. A global minimizing time optimization is performed in view to reach maximum performances. Appropriate dimensionless groups are defined. The results are presented in normalized charts for general applications. The collector temperature presents major influence on the conceptual and functional characteristics compared to the stagnation temperature influence. On the other hand the thermal load in the refrigerated space and the thermal conductance of the walls has analogous effects, therefore important to be considered in actual design. As a result, the model is expected to be a useful tool for simulation, design, and optimization of solar collector based energy systems.
Experimental Investigation on an Absorption Refrigerator Driven by Solar Cells
Zi-Jie Chien
2013-01-01
Full Text Available This experiment is to study an absorption refrigerator driven by solar cells. Hand-held or carried in vehicle can be powered by solar energy in places without power. In the evenings or rainy days, it is powered by storage battery, and it can be directly powered by alternating current (AC power supply if available, and the storage battery can be charged full as a backup supply. The proposed system was tested by the alternation of solar irradiance 550 to 700 W/m2 as solar energy and 500ml ambient temperature water as cooling load. After 160 minutes, the proposal refrigerator can maintain the temperature at 5–8°C, and the coefficient of performance (COP of NH3-H2O absorption refrigeration system is about 0.25. Therefore, this system can be expected to be used in remote areas for refrigeration of food and beverages in outdoor activities in remote and desert areas or long-distance road transportation of food or low temperature refrigeration of vaccine to avoid the deterioration of the food or the vaccines.
Refrigeration Cycle Design for Refrigerant Mixtures by Molecular Simulation
Smith, W.R.; Francová, Magda; Kowalski, M.; Nezbeda, Ivo
2010-01-01
Roč. 75, č. 4 (2010), s. 383-391. ISSN 0010-0765 R&D Projects: GA AV ČR IAA400720710 Grant ostatní: NSERC(CA) OGP1041 Institutional research plan: CEZ:AV0Z40720504 Keywords : refrigerants * molecular simulations * vapor–liquid equilibrium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.853, year: 2010
Applying design of experiments to a compression refrigeration cycle
Nuno Ricardo Costa; João Garcia
2015-01-01
Refrigeration cycles are used in a large diversity of industrial and domestic (residential and non-residential) equipment and their efficiency depend on several variables. To better understanding of how controllable variables impact on a compression refrigeration cycle efficiency, statistically designed experiments were conducted and data were analyzed. A quadratic polynomial model was fitted to Coefficient of Performance and variable settings to maximize cycle efficiency identified. Results ...
Highlights: • A novel dual-nozzle ejector enhanced refrigeration cycle is proposed. • The novel cycle is evaluated by using the developed mathematical model. • The results show the performances of the novel cycle could be significantly improved. • The novel cycle shows its promise in household refrigerator-freezers applications. - Abstract: In this study, a novel dual-nozzle ejector enhanced refrigeration cycle is presented for dual evaporator household refrigerator-freezers. The proposed ejector equipped with two nozzles can efficiently recover the expansion work from cycle throttling processes and enhance cycle performances. The performances of the novel cycle are evaluated by using the developed mathematical model, and then compared with that of the conventional ejector enhanced refrigeration cycle and basic vapor-compression refrigeration cycle. The simulation results show that for the given operating conditions, the coefficient of performance (COP) of the novel cycle using refrigerant R134a is improved by 22.9–50.8% compared with that of the basic vapor-compression refrigeration cycle, and the COP improvement is 10.5–30.8% larger than that of the conventional ejector enhanced refrigeration cycle. The further simulation results of the novel cycle using refrigerant R600a indicate that the cycle COP and volumetric refrigeration capacity could be significantly improved
Absorber-evaporator unit for an absorption-refrigeration system
Hallatt, R.J.; Rorschach, R.L.
1965-01-26
This low temperature absorption-refrigeration system uses an absorber-evaporator. A conduit is connected between the upper portion of the absorber and the lower portion of the evaporator to conduct inert gas from the absorber to the evaporator. A second conduit connects the upper portion of the evaporator to the lower portion of the absorber and a blower in this conduit circulates the inert gas through the closed system. By placing the blower between the evaporator ad the absorber, the pressure in the evaporator is maintained at a minimum so that the working temperature is as low as possible. The medium to be cooled by the refrigerant is circulated through a heat exchanger located within the evaporator, whereby the latent heat of vaporization of the liquid refrigerant is employed to cool the outside medium. (2 claims)
Industrial trigeneration using ammonia-water absorption refrigeration systems (AAR)
In many industrial processes there is a simultaneous need for electric power and refrigeration at low temperatures. Examples are in the food and chemical industries. Nowadays the increase in fuel prices and the ecological implications are giving an impulse to energy technologies that better exploit the primary energy source and integrated production of utilities should be considered when designing a new production plant. The number of so-called trigeneration systems installations (electric generator and absorption refrigeration plant) is increasing. If low temperature refrigeration is needed (from 0 to -40 deg. C), ammonia-water absorption refrigeration plants can be coupled to internal combustion engines or turbogenerators. A thermodynamic system study of trigeneration configurations using a commercial software integrated with specifically designed modules is presented. The study analyzes and compares heat recovery from the primary mover at different temperature levels. In the last section a simplified economic assessment that takes into account disparate prices in European countries compares conventional electric energy supply from the grid and optimized trigeneration plants in one test case (10 MW electric power, 7000 h/year)
SOLAR MULTI-STAGE ABSORPTION REFRIGERATION SYSTEMS BASED ON FILM TYPE HEAT-MASS EXCHANGE APPARATUSES
Дорошенко, О.В.; Антонова, А.Р.; Людницький, К.В.
2015-01-01
The paper presents the developed circuit solutions for alternative refrigeration systems based on the of heat-absorption cycle and solar energy utilization for regeneration (recovery) of the absorbent solution. Cascade principle of heat-mass exchange apparatuses construction was applied, of drying and cooling loops with varying of temperature level and increasing of absorbent concentration on the cascade steps. Film type heat and mass transfer equipment, which is the part of the drying and ...
Modelling and Simulation of a Two-Stage Refrigeration Cycle
Verheyleweghen, Adriaen
2015-01-01
A two-stage refrigeration cycle was modelled and optimized in MATLAB. The optimum was found to be very flat, resulting in small losses from disturbances and implementation errors. The two unconstrained degrees of freedom were used to implement self-optimizing controllers. A subset of five measurements was used for the self-optimizing controller since this gave reasonably small losses. The controllers assured optimal steady-state operation of the refrigeration cycle even when disturbed. Studie...
An innovative ecological hybrid refrigeration cycle for high power refrigeration facility
Cyklis Piotr
2015-09-01
Full Text Available Searching for new refrigerants is one of the most significant scientific problems in refrigeration. There are ecological refrigerants commonly known: H2O and CO2. H2O and CO2 known as natural refrigerants, but they have problems:a high freezing point of H2O and a low triple point of CO2. These problems can be solved by the application of a hybrid sorption-compression refrigeration cycle. The cycle combines the application possibility of H2O in the high temperature sorption stage and the low temperature application of CO2 in the compression stage. This solution gives significant energy savings in comparison with the two-stage compressor cycle and with the one-stage transcritical CO2 cycle. Besides, the sorption cycle may be powered by low temperature waste heat or renewable heat. This is an original idea of the authors. In the paper an analysis of the possible extension of this solution for high capacity industrial refrigeration is presented. The estimated energy savings as well as TEWI (Total Equivalent Warming Impact index for ecological gains are calculated.
A small quantum absorption refrigerator with reversed couplings
Silva, Ralph; Skrzypczyk, Paul; Brunner, Nicolas
2015-01-01
Small quantum absorption refrigerators have recently attracted renewed attention. Here we present a missing design of a two-qubit fridge, the main feature of which is that one of the two machine qubits is itself maintained at a temperature colder than the cold bath. This is achieved by 'reversing' the couplings to the baths compared to previous designs, where only a transition is maintained cold. We characterize the working regime and the efficiency of the fridge. We demonstrate the soundness...
Ayala Delgado, Ramon; Heard, Christopher Lionel [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1996-12-31
The use of the absorption/compression refrigeration in the industrial area is analyzed. It is estimated than in Mexico 50% of the food is wasted for lack of refrigeration in the producing centers and by the inefficient distribution system, as well as for the hot climate. The functioning of the absorption refrigeration and the hybrid system absorption/compression which can operate with the two thermodynamic cycles in variable proportions, depending on the specific application, looking for operational advantages and energy efficiency is described. This type of technology could be applied in Mexico due to the lack of industrial refrigeration and to the need of substituting compressors in some companies which have up to 20 years of use [Espanol] Se analiza el uso de la refrigeracion por absorcion/compresion en el area industrial. En Mexico se estima que se desperdicia el 50% de los alimentos por falta de refrigeracion en los centros productores y por el deficiente sistema de distribucion, asi como por el clima calido. Se describe el funcionamiento de la refrigeracion por absorcion y la refrigeracion por absorcion/compresion o sistema hibrido, el cual puede funcionar con los dos tipos de ciclos termodinamicos, en proporciones variables, dependiendo de la aplicacion especifica, buscando ventajas de operacion y eficiencia energetica. Este tipo de tecnologia podria aplicarse en Mexico debido a la falta de refrigeracion industrial y a la necesidad de sustituir compresores en algunas empresas los cuales tienen hasta 20 anos de uso
Ecological optimization for an irreversible magnetic Ericsson refrigeration cycle
An irreversible Ericsson refrigeration cycle model is established, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leakage, and the efficiency of the regenerator are taken into account. Expressions for several important performance parameters, such as the cooling rate, coefficient of performance (COP), power input, exergy output rate, entropy generation rate, and ecological function are derived. The influences of the heat leakage and the time of the regenerative processes on the ecological performance of the refrigerator are analyzed. The optimal regions of the ecological function, cooling rate, and COP are determined and evaluated. Furthermore, some important parameter relations of the refrigerator are revealed and discussed in detail. The results obtained here have general significance and will be helpful in gaining a deep understanding of the magnetic Ericsson refrigeration cycle. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Ecological optimization for an irreversible magnetic Ericsson refrigeration cycle
Wang Hao; Wu Guo-Xing
2013-01-01
An irreversible Ericsson refrigeration cycle model is established,in which multi-irreversibilities such as finite-rate heat transfer,regenerative loss,heat leakage,and the efficiency of the regenerator are taken into account.Expressions for several important performance parameters,such as the cooling rate,coefficient of performance (COP),power input,exergy output rate,entropy generation rate,and ecological function are derived.The influences of the heat leakage and the time of the regenerative processes on the ecological performance of the refrigerator are analyzed.The optimal regions of the ecological function,cooling rate,and COP are determined and evaluated.Furthermore,some important parameter relations of the refrigerator are revealed and discussed in detail.The results obtained here have general significance and will be helpful in gaining a deep understanding of the magnetic Ericsson refrigeration cycle.
The performance of an open cycle dilution refrigerator
The idea of an open cycle dilution refrigerator is that two separate flows of 3-helium an 4-helium are mixed at low temperature, overcoming the influence of the gravitation. We have measured the performance of the refrigerator for a high concentration of 3He, where the mixture appears in two phases, and we discuss the possibility of running at a lower concentration (single phase). We discuss the use of such a refrigerator to cool bolometers for telescopes, on earth or in space. (author)
Modeling and Simulation of a Desiccant Assisted Brayton Refrigeration Cycle
Nobrega, Carlos E.L.; Sphaier, Leandro Alcoforado
2012-01-01
The phase-out of CFCs has shed a new light over natural refrigerants, which have null global warming potentials. Air would be a natural choice, and although the Brayton cycle usually exhibits a lower coefficient of performance when compared to vapor-compression systems of same capacity, it has been considered in applications other than aircraft cooling. These include gas separation, food processing and preservation, refrigerated containers and train air-conditioning. Price perspectives in the...
Highlights: • Absorption refrigeration is powered by data center waste heat. • Waste heat from 3 to 5 server racks produces cooling for an additional rack. • An economic analysis shows the payback period can be as short as 4–5 months. - Abstract: This paper addresses the technical and economic issues associated with waste heat recovery in data centers through the use of absorption cooling machines. The theoretical possibility of utilizing the heat dissipated by a server, or a number of servers, to power an absorption system, which in turn produces cooling for other servers in the data center, is investigated. For this purpose, a steady-state thermodynamic model is developed to perform energy balance and exergy analyses for a novel configuration of an on-chip two-phase cooling system and an absorption refrigeration system. This combination is created by replacing the condenser in the on-chip cooling circuit with the generator of an absorption refrigeration cycle. The performance of the developed model in simulating both LiBr–water and water–ammonia absorption cooling systems is examined through verification of the model results against the reference data available in the literature. The verification indicates the superiority of LiBr–water absorption system for data center/server operating conditions. Therefore, a LiBr–water absorption refrigeration system is modeled in the novel combined heat recovery system. For these systems it is shown that the traditional definition for the coefficient of performance (COP) is not appropriate to evaluate the performance and, in its place, introduce a new figure of merit. Through a sensitivity analysis, the effects of server waste heat quality, server coolant type, solution peak concentration, solution heat exchanger effectiveness, evaporator temperature, and operating pressures on the performance of the novel system are investigated. Finally, using the thermodynamic model and cost information provided by the
Automated modelling of complex refrigeration cycles through topological structure analysis
We have developed a computational method for analysis of refrigeration cycles. The method is well suited for automated analysis of complex refrigeration systems. The refrigerator is specified through a description of flows representing thermodynamic sates at system locations; components that modify the thermodynamic state of a flow; and controls that specify flow characteristics at selected points in the diagram. A system of equations is then established for the refrigerator, based on mass, energy and momentum balances for each of the system components. Controls specify the values of certain system variables, thereby reducing the number of unknowns. It is found that the system of equations for the refrigerator may contain a number of redundant or duplicate equations, and therefore further equations are necessary for a full characterization. The number of additional equations is related to the number of loops in the cycle, and this is calculated by a matrix-based topological method. The methodology is demonstrated through an analysis of a two-stage refrigeration cycle.
Efficiency analysis of alternative refrigerants for ejector cooling cycles
Highlights: • Advantages of using alternative refrigerants as ejector refrigerants were presumed. • Computer software basing on theoretical model of Huang et al. (1999) was prepared. • Optimal temperature range of primary vapor for each working fluid was calculated. - Abstract: Computer software, basing on the theoretical model of Huang et al. with thermodynamic properties of selected refrigerants, was prepared. Investigation was focused on alternative refrigerants that belong to two groups of substances: common solvents (acetone, benzene, cyclopentane, cyclohexane and toluene) and non-flammable synthetic refrigerants applied in Organic Rankine Cycle (ORC) (R236ea, R236fa, R245ca, R245fa, R365mfc and RC318). Refrigerants were selected to detect a possibility to use them in ejector cooling system powered by a high-temperature heat source. A series of calculations were carried out for the generator temperature between 70 and 200 °C, with assumed temperatures of evaporation 10 °C and condensation 40 °C. Investigation revealed that there is no single refrigerant that ensures efficient operation of the system in the investigated temperature range of primary vapor. Each substance has its own maximum entrainment ratio and COP at its individual temperature of the optimum. The use of non-flammable synthetic refrigerants allows obtaining higher COP in the low primary vapor temperature range. R236fa was the most beneficial among the non-flammable synthetic refrigerants tested. The use of organic solvents can be justified only for high values of motive steam temperature. Among the solvents, the highest values of entrainment ratio and COP throughout the range of motive temperature were noted for cyclopentane. Toluene was found to be an unattractive refrigerant from the ejector cooling point of view
ASHRAE`s new application guide for absorption cooling/refrigeration using recovered heat
Dorgan, C.B.; Dorgan, C.E.; Leight, S.P. [Dorgan Associates, Inc., Madison, WI (United States)
1995-12-31
ASHRAE has a new publication, Application Guide for Absorption Cooling/Refrigeration Using Recovered Heat. This guide is a comprehensive reference manual for the application of indirect-fired absorption machines. An indirect-fired absorption machine uses heat recovered from another process or heat cycle machine versus a direct-fired absorption machine, which uses a primary fuel source. The Guide is designed to help engineers, owners, developers, and marketing personnel to become familiar with the requirements of an absorption system, evaluate indirect-fired absorption machines for specific requirements, evaluate the potential of available recovered heat sources, select the most economical system, and understand both lithium bromide (LiBr) and ammonia absorption machines. The Guide provides information on the application and economics of absorption machines. Detailed design of an absorption system is covered in other publications, which are listed in the Guide. The Guide introduces absorption technology through comparison with and using the terminology of vapor-compression technology. This information is then expanded to enable the reader to apply absorption technology to many situations where recovered heat is available.
Rotating Carnot-cycle magnetic refrigerators for use near 2 K
The application or removal of a magnetic field of order 5 T to some Gd compounds at low temperatures results in 10-20 K adiabatic temperature changes or the isothermal expulsion or absorption of heat. In particular, the heat absorbed by 1 liter of appropriate magnetic material at 2 K is several hundred J. A rotating device is decribed which will allow cycle times of much less than 1 sec, resulting in approximately 1-kW refrigeration capacity for each liter of paramagnetic Gd compound. This heat could be expelled with better than 80% of Carnot efficiency into a helium refrigerator operating at 10-14 K
Waste Heat Powered Ammonia Absorption Refrigeration Unit for LPG Recovery
Donald C, Energy Concepts Co.; Lauber, Eric, Western Refining Co.
2008-06-20
An emerging DOE-sponsored technology has been deployed. The technology recovers light ends from a catalytic reformer plant using waste heat powered ammonia absorption refrigeration. It is deployed at the 17,000 bpd Bloomfield, New Mexico refinery of Western Refining Company. The technology recovers approximately 50,000 barrels per year of liquefied petroleum gas that was formerly being flared. The elimination of the flare also reduces CO2 emissions by 17,000 tons per year, plus tons per year reductions in NOx, CO, and VOCs. The waste heat is supplied directly to the absorption unit from the Unifiner effluent. The added cooling of that stream relieves a bottleneck formerly present due to restricted availability of cooling water. The 350oF Unifiner effluent is cooled to 260oF. The catalytic reformer vent gas is directly chilled to minus 25oF, and the FCC column overhead reflux is chilled by 25oF glycol. Notwithstanding a substantial cost overrun and schedule slippage, this project can now be considered a success: it is both profitable and highly beneficial to the environment. The capabilities of directly-integrated waste-heat powered ammonia absorption refrigeration and their benefits to the refining industry have been demonstrated.
Dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle
The basic SAR (solar-driven adsorption refrigeration) machine is an intermittent cold production system. Recently, the CO-SAR (continuous operation solar-powered adsorption refrigeration) system is developed. The CO-SAR machine is based on the theoretical CTAR (constant temperature adsorption refrigeration) cycle in which the adsorption process takes place at a constant temperature that equals the ambient temperature. Practically, there should be a temperature gradient between the adsorption bed and the surrounding atmosphere to provide a driving potential for heat transfer. In the present study, the dynamic analysis of the CTAR cycle is developed. This analysis provides a comparison between the theoretical and the dynamic operation of the CTAR cycle. The developed dynamic model is based on the D-A adsorption equilibrium equation and the energy and mass balances in the adsorption reactor. Results obtained from the present work demonstrate that, the idealization of the constant temperature adsorption process in the theoretical CTAR cycle is not far from the real situation and can be approached. Furthermore, enhancing the heat transfer between the adsorption bed and the ambient during the bed pre-cooling process helps accelerating the heat rejection process from the adsorption reactor and therefore approaching the isothermal process. - Highlights: • The dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle is developed. • The CTAR theoretical and dynamic cycles are compared. • The dynamic cycle approaches the ideal one by enhancing the bed precooling
Experimental Investigation on an Absorption Refrigerator Driven by Solar Cells
Zi-Jie Chien; Hung-Pin Cho; Ching-Song Jwo; Chao-Chun Chien; Sih-Li Chen; Yen-Lin Chen
2013-01-01
This experiment is to study an absorption refrigerator driven by solar cells. Hand-held or carried in vehicle can be powered by solar energy in places without power. In the evenings or rainy days, it is powered by storage battery, and it can be directly powered by alternating current (AC) power supply if available, and the storage battery can be charged full as a backup supply. The proposed system was tested by the alternation of solar irradiance 550 to 700 W/m2 as solar energy and 500ml ambi...
Morejon, C.F.M.; Brum, N. de C. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Programa de Engenharia Mecanica]. E-mails: Camilo_freddy@hotmail.com; Nisio@serv.com.ufrj.br
2000-07-01
This work presents a development of a thermal fluid dynamics model and a solution of a steady state absorption refrigeration cycle, with ammonia water as the working fluid. Analytical thermodynamics models expressing the enthalpy in function of pressure, temperature and composition (h=f(P,T,x)), are used with the aim to design all of the cycle devices, moved by any type of energy such as solar, natural gas, steam or electrical energy (Morejon and Hackenberg, 1978). The development of the analysis is carried out by the application of thermal fluid dynamics concepts together with a detailed study of the heat and mass transfer in the different cycle stages. The thermodynamic cycle model, obtained from equation of state for ammonia - water mixtures (Ziegker and Trepp, 1984), is represented by the relation h - x (enthalpy-composition) for different pressures and temperatures. The obtained models are used to implement computational codes in MAPLE-V facilitating the design and simulation of refrigeration system. This study can be applied in the systems of air conditioning and refrigeration chambers design. (author)
A comparative study on the GAX based absorption refrigeration systems: SGAX, GAXH and GAX-E
In this paper, two GAX-ejector absorption refrigeration cycles are proposed and investigated thermodynamically. In the first cycle (GAX-E Model A), the ejector draws vapor from the evaporator and raises the absorber pressure. In the second combined cycle (GAX-E Model B), the ejector is used to raise the condenser pressure. The performances of these two cycles are compared with those of the standard GAX (SGAX) cycle and two different arrangements of the hybrid GAX (GAXH Model A and GAXH Model B) cycles at the same working conditions. The comparison is performed through parametric studies in which the effects of generator and evaporator temperatures as well as the degassing range on the first and second law efficiencies are investigated. It is found that the COP of GAX-E Model B cycle is higher than that of the SGAX cycle by up to 16.7%. The maximum second law efficiency for the GAX-E Model B cycle is only slightly lower than the highest efficiency value which is obtained for the GAXH Model B cycle. As there is no compressor in the GAX-E Model B cycle, this cycle can be recommended for refrigeration purposes from the viewpoint of thermo-economics. - Highlights: ► Five different configurations of GAX based cycles are compared thermodynamically. ► For all the GAX cycles the highest exergy destructions occur in the absorber–desorber. ► The COP of standard GAX cycle is enhanced by 16.7% when an ejector is employed.
Cooling, freezing and heating with the air cycle: air as the ultimate green refrigerant
Verschoor, M.J.E.
2000-01-01
Due to the recent concern about the damage that CFCs cause to the environment (ozone layer, global warming) and the absence of commonly acceptable alternative refrigerants, the search for alternative refrigeration concepts is going on. Air as refrigerant in the Joule-Brayton cycle (air cycle) is one of the most natural refrigerants, and it meets all criteria for a refrigerant being environmentally benign. For this reason the air cycle is one of the most promising long-term alternatives for re...
Abdelaziz, Omar; Fricke, Brian; Vineyard, Edward A.
2012-01-01
Commercial refrigeration systems are known to be prone to high leak rates and to consume large amounts of electricity. As such, both the direct emissions related to refrigerant leakage and the indirect emissions resulting from primary energy consumption contribute greatly to their Life Cycle Climate Performance (LCCP). In this paper, an LCCP design tool is used to evaluate the performance of a typical commercial refrigeration system with alternative refrigerants and minor system modifications...
Thermodynamics of an ionic-liquid (IL) based absorption refrigeration system has been numerically analyzed. It provides an alternative to the normally toxic working fluids, such as the ammonia in conventional absorption systems. The use of ILs also eliminates crystallization and metal-compatibility problems of the water/LiBr system. Mixtures of refrigerants and imidazolium-based ILs are theoretically explored as the working fluid pairs in a miniature absorption refrigeration system, so as to utilize waste-heat to power a refrigeration/heat pump system for electronics cooling. A non-random two-liquid (NRTL) model was built and used to predict the solubility of the mixtures. Saturation temperatures at the evaporator and condenser were set at 25 °C and 50 °C, respectively, with the power dissipation of 100 W. Water in combination with [emim][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) gave the highest coefficient of performance (COP) around 0.9. The refrigerant/IL compatibility indicated by the circulation ratio, alkyl chain length of the IL, and thermodynamic properties of the refrigerants, such as latent heat of evaporation were proven to be important factors in determining the performance of the absorption system. The negative effect of high viscosity was mitigated by dilution of the IL with the refrigerant and the use of slightly larger microfluidic channel heat exchangers. -- Highlights: ► Mixtures of refrigerant/ionic-liquid are studied for absorption system. ► We carry out comprehensive theoretical thermodynamic analysis. ► The essential factors of refrigerant/IL affecting the performance are identified. ► Water/[emim][BF4] showed the best performance of COP. ► The effects of high viscosity ILs on the system performance are not significant.
PERFORMANCE OF A TWO-CYCLE REFRIGERATOR/FREEZER USING HFC REFRIGERANTS
A two-cycle 18 ft3 (0.51 m3) refrigerator/freezer (R/F) was tested utilizing American National Standards Institute (ANSI)/AHAM (1988) standards for energy consumption testing. A 34.9% energy consumption reduction was realized. This work presents a proven method of reducing the ...
Darwish, N.A.; Al-Hashimi, S.H.; Al-Mansoori, A.S. [The Chemical Engineering Program, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates)
2008-11-15
The Robur absorption-refrigeration water-ammonia (ARWA) system is analyzed using Aspen Plus flowsheet simulator. The results are compared with experimental and some manufacturer data reported in the open literature. Among performance parameters analyzed are coefficient of performance (COP), heat duties of the evaporator, absorber, and the condenser, refrigerant concentration in the weak and strong solution, and flow rates of the weak solution and the flow rate of refrigerant passing through the evaporator. In general, a very good agreement between the simulator's results and the experimental measurements was found. Also, results obtained for the effect of separator (input) heat duty on the COP agree well with the reported experimental data with a maximum percentage deviation of 1.8%. Efficiency of the separator in splitting off the refrigerant at the column top is shown to be of crucial importance; COP increased by 15% in going from 1 to 5 theoretical equivalent mass transfer stages in the separator. Some innovative modifications to Robur cycle aimed at enhancing the separator operation have shown a promising improvement in the COP. In particular, introducing a throttling process directly before the separator can alleviate the separator heat load and enhance the COP by up to 20%. Use of stripping gas injected at the bottom of the boiler is another strategy that has been investigated in this work. (author)
Hourly performance prediction of ammonia–water solar absorption refrigeration
This paper deals with the hourly performance investigation of solar absorption refrigeration (SAR) system with evacuated tube collector and ammonia–water (NH3–H2O) solution. The SAR system is presented to simulate the system characteristic variations using hourly atmospheric air temperature and solar radiation data for Adana province in Turkey. The evaluation is performed for the maximum temperature occurrence day on July 29. First, the variations of various parameters, such as absorption refrigeration machine efficiency, condenser capacity and heat transfer rate in the generator and absorber during the day, are calculated for different cooling capacities and generator temperatures. Later, the minimum evacuated tube collector surface area is determined. According to the obtained results, the SAR system is considerably suitable for home/office-cooling purposes between the hours 09:00 and 16:00 in the southern region of Turkey such as Adana province. The most suitable performance of the absorption cooling system is calculated for the generator temperature values equal to or higher than 110 °C. The performance coefficient of the cooling (COPcooling) varies in the range of 0.243–0.454 while that of the heating (COPheating) changes from 1.243 to 1.454 during the day. Evacuated tube collector area for a 3.5 kW cooling load capacity is found to be 35.95 m2 for the region at 16:00 whereas it is 19.85 m2 at 12:00. - Highlights: ► Hourly performance investigation of solar absorption NH3–H2O refrigeration system is performed. ► Hourly atmospheric temperature and solar radiation on July 29 for Adana province in Turkey were used in the analysis. ► Optimum generator temperature for evacuated tube collector type was determined as higher than 110 °C. ► COPcooling was calculated in the range of 0.243–0.454 between hours 09:00 and 16:00.
General performance characteristics of an irreversible ferromagnetic Stirling refrigeration cycle
G. Lin; E.H. Bruck; O. Tegus; L. Zhang
2004-01-01
A new magnetic-refrigeration-cycle model using ferromagnetic materials as a cyclic working substance is set up, in which finite-rate heat transfer, heat leak and regeneration time are taken into account. On the basis of the thermodynamic properties of a ferromagnetic material, the general performanc
In this contribution, a study of the thermal losses effect undergone by the different parts of an intermittent absorption solar refrigeration cycle using the Ammonia/Water mixture is presented. After having shown the interest of the intermittent cycles through the discussion of the problem of the adaptation of these cycles to solar energy, mass and thermal assessments for each compartment of the installation were established for the two cases without and with thermal losses. The resulting differential equations system is solved numerically. The theoretical results obtained concern the temperature variations, the vapor flow as well as the compositions of the rich and the poor solutions
Emma Berrich Betouche
2016-03-01
Full Text Available A thermodynamic approach based on the hierarchical decomposition which is usually used in mechanical structure engineering is proposed. The methodology is applied to an absorption refrigeration cycle. Thus, a thermodynamic analysis of the performances on solar absorption refrigerators is presented. Under the hypothesis of an endoreversible model, the effects of the generator, the solar concentrator and the solar converter temperatures, on the coefficient of performance (COP, are presented and discussed. In fact, the coefficient of performance variations, according to the ratio of the heat transfer areas of the high temperature part (the thermal engine 2 Ah and the heat transfer areas of the low temperature part (the thermal receptor Ar variations, are studied in this paper. For low values of the heat-transfer areas of the high temperature part and relatively important values of heat-transfer areas of the low temperature part as for example Ah equal to 30% of Ar, the coefficient of performance is relatively important (approximately equal to 65%. For an equal-area distribution corresponding to an area ratio Ah/Ar of 50%, the COP is approximately equal to 35%. The originality of this deduction is that it allows a conceptual study of the solar absorption cycle.
Solar Absorption Refrigeration System for Air-Conditioning of a Classroom Building in Northern India
Agrawal, Tanmay; Varun; Kumar, Anoop
2015-10-01
Air-conditioning is a basic tool to provide human thermal comfort in a building space. The primary aim of the present work is to design an air-conditioning system based on vapour absorption cycle that utilizes a renewable energy source for its operation. The building under consideration is a classroom of dimensions 18.5 m × 13 m × 4.5 m located in Hamirpur district of Himachal Pradesh in India. For this purpose, cooling load of the building was calculated first by using cooling load temperature difference method to estimate cooling capacity of the air-conditioning system. Coefficient of performance of the refrigeration system was computed for various values of strong and weak solution concentration. In this work, a solar collector is also designed to provide required amount of heat energy by the absorption system. This heat energy is taken from solar energy which makes this system eco-friendly and sustainable. A computer program was written in MATLAB to calculate the design parameters. Results were obtained for various values of solution concentrations throughout the year. Cost analysis has also been carried out to compare absorption refrigeration system with conventional vapour compression cycle based air-conditioners.
Theoretical Study of New Combined Absorption-Ejector Refrigeration System
Abed, A. M.; Sopian, K.; Alghoul, M. A.; Al-Shamani, A. N.; Ruslan, M. H.; Mat, S.
2015-09-01
An improved system of the new combined single stage absorption cycle operated with NH3/H2O as working fluid was performed. In order to enhance performance the cycle a new configuration of absorption system was utilized. The performances of two configurations of the combined absorption cycle were compared; a) with common solution heat exchanger and b) divided the streamline of solution heat exchanger to recover the internal heat. Based on the analysis, it has been shown that the second configuration a significant reduction of the required generator and absorber loads by about 20% and 17% respectively, with increased coefficient of performance (COP) about 12% compared to the first configuration. This improvement in the overall COP is found due to improve energy utilization efficiency significantly.
Building and Experimentation of Diffusion Absorption Refrigeration Machines
R. Mbarek
2013-01-01
Full Text Available This paper presents an experimental investigation of a drivenn-butane/octane (C4H10/ C8H18 diffusion absorption cooling machine according to the cycleof Platen and Munters. For that purpose, we construct a prototype designed for air-conditioning applications. The cooling capacity of the constructed machine is 55 W. A clear description of the constructed prototype is given. These researchers have a final goal which is coupling these types of cooling machines with solarenergy. In this paper, our major challenge is to design and choose the kind, the shape and dimensions of all components, which will afford a final and complete machine. In this experimental case, the value of COP reached was 0.3. Experimental results show that such refrigerator, simply fabricated, gives promising results and could be used for clean and safe use where there is agrowing interest.
Performance analysis of solar powered absorption refrigeration system
Abu-Ein, Suleiman Qaseem; Fayyad, Sayel M.; Momani, Waleed; Al-Bousoul, Mamdouh
2009-12-01
The present work provides a detailed thermodynamic analysis of a 10 kW solar absorption refrigeration system using ammonia-water mixtures as a working medium. This analysis includes both first law and second law of thermodynamics. The coefficient of performance (COP), exergetic coefficient of performance (ECOP) and the exergy losses (Δ E) through each component of the system at different operating conditions are obtained. The minimum and maximum values of COP and ECOP were found to be at 110 and 200°C generator temperatures respectively. About 40% of the system exergy losses were found to be in the generator. The maximum exergy losses in the absorber occur at generator temperature of 130°C for all evaporator temperatures. A computer simulation model is developed to carry out the calculations and to obtain the results of the present study.
Parametric optimum design of an irreversible spin quantum refrigeration cycle
Lin Bi-Hong; Chen Jin-Can
2005-01-01
The general performance characteristics of an irreversible quantum refrigeration cycle using many non-interacting spin-1/2 systems as the working substance and consisting of two adiabatic and two isomagnetic field processes are investigated, based on the quantum master equation and semi-group approach. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the refrigeration cycle subject to the finite cycle duration is optimized. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal region of the coefficient of performance and the optimal ranges of the temperatures of the working substance and the times spent on the two isomagnetic field processes are determined. Moreover, the optimal performance of the cycle in the high-temperature limit is also analysed in detail. The results obtained here are further generalized, so that they may be directly used to describe the performance of the quantum refrigeration cycle using spin-J systems as the working substance.
Theoretical Study on CO2 Transcritical Cycle Combined Ejector Cycle Refrigeration System
卢苇; 马一太; 李敏霞; 查世彤
2003-01-01
Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming (CO2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO2 transcritical cycle with ejector cycle is proposed in this paper. The CO2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system). In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants (NH3, H2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.
Menken, Jan Christoph; Weustenfeld, Thomas; Köhler, Jürgen
2014-01-01
Recent attempts to find energy-efficient thermal management systems for electric and plug-in hybrid electric vehicles have led to secondary loop systems as an alternative approach to meet dynamic heating and cooling demands and reduce refrigerant charge. As such, a thorough understanding of the vapor compression cycle, which serves as the central thermal supply unit, is required. In addition to design considerations concerning the type and size of components such as the heat exchangers or com...
New Regenerative Cycle for Vapor Compression Refrigeration
Bergander, Mark J [Magnetic Development, Inc.; Butrymowicz, Dariusz [Polish Academy of Scinces
2010-01-26
This project was a continuation of Category 1 project, completed in August 2005. Following the successful bench model demonstration of the technical feasibility and economic viability, the main objective in this stage was to fabricate the prototype of the heat pump, working on the new thermodynamic cycle. This required further research to increase the system efficiency to the level consistent with theoretical analysis of the cycle. Another group of objectives was to provide the foundation for commercialization and included documentation of the manufacturing process, preparing the business plan, organizing sales network and raising the private capital necessary to acquire production facilities.
Refrigeration cycle for cryogenic separation of hydrogen from coke oven gas
Kun CHANG; Qing LI; Qiang LI
2008-01-01
Ten billion cubic meters of hydrogen are dissip-ated to the environment along with the emission of coke-oven gas every year in China. A novel cryogenic separation of hydrogen from coke oven gas is proposed to separate the hydrogen and liquefy it simultaneously, and the cooling capacity is supplied by two refrigeration cycles. The perform-ance of the ideal vapor refrigeration cycle is analyzed with methane and nitrogen as refrigerant respectively. The results show that the coefficient of performance (COP) of methane refrigeration cycle is 2.7 times that of nitrogen refrigeration cycle, and the figure of merit (FOM) of methane refrigera-tion cycle is 1.6 times that of nitrogen refrigeration cycle. The performance of ideal gas refrigeration cycle is also analyzed with neon, hydrogen and helium as refrigerant respectively. The results show that both the coefficient of performance and figure of merit of neon refrigeration cycle is the highest. It is thermodynamically possible to arrange the refrigeration cycle with methane and neon as refrigerant, respectively.
Cooling, freezing and heating with the air cycle: air as the ultimate green refrigerant
Verschoor, M.J.E.
2000-01-01
Due to the recent concern about the damage that CFCs cause to the environment (ozone layer, global warming) and the absence of commonly acceptable alternative refrigerants, the search for alternative refrigeration concepts is going on. Air as refrigerant in the Joule-Brayton cycle (air cycle) is one
Experimental investigation of the ecological hybrid refrigeration cycle
Cyklis Piotr; Kantor Ryszard; Ryncarz Tomasz; Górski Bogusław; Duda Roman
2014-01-01
The requirements for environmentally friendly refrigerants promote application of CO2 and water as working fluids. However there are two problems related to that, namely high temperature limit for CO2 in condenser due to the low critical temperature, and low temperature limit for water being the result of high triple point temperature. This can be avoided by application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption high temperature cycle used ...
Gas Vapor Injection on Refrigerant Cycle Using Piston Technology
Colmek, Sophie; Goderneaux, Laurent
2012-01-01
Gas vapor injection on refrigerant cycle is always used with Scroll, Rotary or others compressors technology to improve efficiency of the system at low and high ambient temperatures. Probably this kind of compressor is more adapted than the piston technology owing to their mechanical system. In this paper, we present the challenge of vapor injection realized on piston technology compressor range non for improving the cooling capacity of the system but to maintain the compressor temperature in...
AN EXPERIMENTAL STUDY ON A VAPOR COMPRESSION REFRIGERATION CYCLE BY ADDING INTERNAL HEAT EXCHANGER
Muhammad Asmail Eleiwi
2013-01-01
Thispaper presents practical study to improve the indication COP of a vaporcompression refrigeration cycle in instrumented automobile air conditioner bydesigning internal heat exchanger and installing it in the vapor compressionrefrigeration cycle. Two cases of vapor compression refrigeration cycle were takenin this paper: the first case is thatthe vapor compression refrigeration cycle without internal heat exchanger andin the second case the vapor compressionrefrigeration cycle with heat...
Computational tool for simulation of power and refrigeration cycles
Córdoba Tuta, E.; Reyes Orozco, M.
2016-07-01
Small improvement in thermal efficiency of power cycles brings huge cost savings in the production of electricity, for that reason have a tool for simulation of power cycles allows modeling the optimal changes for a best performance. There is also a big boom in research Organic Rankine Cycle (ORC), which aims to get electricity at low power through cogeneration, in which the working fluid is usually a refrigerant. A tool to design the elements of an ORC cycle and the selection of the working fluid would be helpful, because sources of heat from cogeneration are very different and in each case would be a custom design. In this work the development of a multiplatform software for the simulation of power cycles and refrigeration, which was implemented in the C ++ language and includes a graphical interface which was developed using multiplatform environment Qt and runs on operating systems Windows and Linux. The tool allows the design of custom power cycles, selection the type of fluid (thermodynamic properties are calculated through CoolProp library), calculate the plant efficiency, identify the fractions of flow in each branch and finally generates a report very educational in pdf format via the LaTeX tool.
Monfared, Behzad; Furberg, Richard; Palm, Björn
2014-01-01
This paper seeks to shed light on the question whether a magnetic household refrigerator with permanent magnets is more environmentally friendly than a conventional, vapor-compression refrigerator. Life cycle assessment has been used as a tool to investigate the environmental impacts associated with the life cycle of a magnetic refrigerator. The results of the assessment have been compared with those of a conventional, vapor-compression refrigerator with the same functionality. The comparison...
Performance of the Oxford miniature Stirling cycle refrigerator
Bradshaw, T. W.; Delderfield, J.; Werrett, S. T.; Davey, G.
The 'Oxford Cryocooler' miniature Stirling cycle cooler, a 5-kg mass split-cycle refrigerator developed for use aboard spacecraft, had as its design performance goal the production of 0.5 W of cooling power at 80 K for 30 W of electrical input power. The goal has actually been exceeded, prompting the present discussion of the compressor power budget and displacer losses. Attention is given to graphs of the cold-end temperature vs. compressor input power and cooling power. The cooler is to be used on the Improved Stratospheric and Mesospheric Sounder experiment of the Upper Atmosphere Research Satellite.
ASHRAE`s new application guide for absorption cooling/refrigeration using recovered heat
Dorgan, C.B.; Dorgan, C.E.; Leight, S.P. [Dorgan Associates Inc., Madison, WI (United States)
1995-07-01
This article is a brief overview of the Guide for Absorption Cooling/Refrigeration Using Recovered Heat. The overview examines the applications of the guide, it`s format and topics on a chapter basis. The authors report that ASHRAE`s purpose for developing this manual is to encourage more engineers and owners to consider using recovered heat for cooling and refrigeration.
Study of optimal discharge pressure of compressor in CO_2 refrigerating trans-critical cycle
无
2008-01-01
In this paper, a carbon dioxide trans-critical refrigerating system which is different from a conventional subcritical refrigerating cycle was studied. The trans-critical carbon dioxide refrigerating systems are based on the Gustav Lorntzen cycle. Emphasis was focused on how to determine the optimal discharge pressure of compressor in CO2 trans-critical cycle. The factors related with the optimal discharge pressure were analyzed. A formula was developed based on cycle simulation, which could be used to pred...
Conceptual design of nuclear CHP using absorption cycle
This paper aims at providing a conceptual idea on the combined heat and power (CHP) using the absorption cycle to simultaneously generate both electricity and useful heat, which is applicable to the conventional nuclear power plants (NPPs). The originality of the scheme is 1) it does not change the operation strategy of the NSSS, 2) the thermal energy of waste heat can be transferred to a long distance, and 3) the thermal energy can be used for cooling as well. As it is expected that the number and the share of NPPs increases soon, the necessity of a partial load operation was raised in argument in case of South Korea. This means the surplus of nuclear energy. In order to make the best of nuclear fuels loaded once, we proposed a combined cycle instead of cutting back reactor power to meet a partial load demand. Figure 1 shows the schematic drawing of the proposal. Since a steam demand in the turbine cycle is equivalent even though an electricity demand is different, the operation strategy of the NSSS does not need to be changed. When a partial load demand is triggered off, turbine power is cut back and a bypass path is open. The bypass path is used for transferring waste heat to an absorption cycle. The CHP using absorption principles was initially developed over 100 years ago. The absorption cycle is a process by which heating and/or cooling effect is produced through the use of two fluids and some quantity of heat input. The absorption cycles accomplish heat transferring through the evaporation of a refrigerant at a low pressure and the rejection of heat through the condensation of the refrigerant at a higher pressure. In the absorption cycles, a secondary fluid or absorbent is used to circulate the refrigerant. Absorption cycles are commercially available today in two basic configurations; lithium bromide/water and water/ammonia (respectively absorbent/ refrigerant). We can have several advantages in this idea. This principle can design a heat transfer mechanism
Control structure selection for vapor compression refrigeration cycle
Yin, Xiaohong; Li, Shaoyuan [Shanghai Jiao Tong Univ., Shanghai (China). Dept. of Automation; Shandong Jianzhu Univ., Jinan (China). School of Information and Electrical Engineering; Cai, Wenjian; Ding, Xudong [Nanyang Technological Univ., Singapore (Singapore). School of Electrical and Electronic Engineering
2013-07-01
A control structure selection criterion which can be used to evaluate the control performance of different control structures for the vapor compression refrigeration cycle is proposed in this paper. The calculation results of the proposed criterion based on the different reduction models are utilized to determine the optimized control model structure. The effectiveness of the criterion is verified by the control effects of the model predictive control (MPC) controllers which are designed based on different model structures. The response of the different controllers applied on the actual vapor compression refrigeration system indicate that the best model structure is in consistent with the one obtained by the proposed structure selection criterion which is a trade-off between computation complexity and control performance.
Combined Refrigeration Cycle for Thermal Power Plant Using Low Grade Waste Steam
Satish Maurya*,
2014-02-01
Full Text Available Now a days, In most of the thermal power plant, where low-pressure steam is being exhausted to the atmosphere as a waste steam. This waste heat could be use to operate many small preheating or cooling equipments or small scale plants. There are many refrigeration systems present for refrigeration and air condition purpose. Such as air refrigeration, vapour compression, vapour absorption etc. In this paper we have presented the concept of combined vapour absorption and vapour compression refrigeration system. We present about the idea discuss here that how a vapour absorption and vapour compression can be used together as one complete working refrigeration plant. By using such concept of refrigeration we can improve the co-efficient of performance of whole plant by minimizing the input. We can also named the system as waste heat recovery refrigeration system.
Second law-based thermodynamic analysis of water-lithium bromide absorption refrigeration system
In this study, the first and the second law of thermodynamics are used to analyze the performance of a single-stage water-lithium bromide absorption refrigeration system (ARS) when some working parameters are varied. A mathematical model based on the exergy method is introduced to evaluate the system performance, exergy loss of each component and total exergy loss of all the system components. Parameters connected with performance of the cycle-circulation ratio (CR), coefficient of performance (COP), Carnot coefficient of performance (COPc ), exergetic efficiency (ξ) and efficiency ratio (τ)-are calculated from the thermodynamic properties of the working fluids at various operating conditions. Using the developed model, the effect of main system temperatures on the performance parameters of the system, irreversibilities in the thermal process and non-dimensional exergy loss of each component are analyzed in detail. The results show that the performance of the ARS increases with increasing generator and evaporator temperatures, but decreases with increasing condenser and absorber temperatures. Exergy losses in the expansion valves, pump and heat exchangers, especially refrigerant heat exchanger, are small compared to other components. The highest exergy loss occurs in the generator regardless of operating conditions, which therefore makes the generator the most important component of the cycle
Stirling-cycle rotating magnetic refrigerators and heat engines for use near room temperature
The application (or removal) of a magnetic field to the ferromagnetic Gd metal near its Curie point (293 K) will produce adiabatic heating (or cooling) of 14 K or isothermal expulsion (or absorption) of 32 kJ of heat per liter of Gd metal. A refrigerator and a heat engine are described for which porous Gd metal forms the rim of a wheel rotating into and out of a magnetic field region. Fluid forced to flow through the porous metal exchanges heat; the field and flow configurations are such that the metal executes a magnetic Stirling cycle allowing a very wide temperature span (many times 14 K) while maintaining the 32-kJ/l capacity. Efficiencies approaching that of Carnot are expected at 1-Hz rotation rates, resulting in 32-kW/l refrigeration or heating capacity
Combined Refrigeration Cycle for Thermal Power Plant Using Low Grade Waste Steam
Satish Maurya*,; Dharmendra Patel
2014-01-01
Now a days, In most of the thermal power plant, where low-pressure steam is being exhausted to the atmosphere as a waste steam. This waste heat could be use to operate many small preheating or cooling equipments or small scale plants. There are many refrigeration systems present for refrigeration and air condition purpose. Such as air refrigeration, vapour compression, vapour absorption etc. In this paper we have presented the concept of combined vapour absorption and vapour compression refri...
THERMODYNAMIC EVALUATION OF FIVE ALTERNATIVE REFRIGERANTS IN VAPOR-COMPRESSION CYCLES
The paper gives results of a thermodynamic evaluation of five alternative refrigerants in a vapor-compression refrigeration cycle, utilizing throttling, super-heating, and combined throttling and superheating. ive alternative refrigerants (R32, R125, R134a, R143a, and R152a) were...
Experimental investigation of the ecological hybrid refrigeration cycle
Cyklis, Piotr; Kantor, Ryszard; Ryncarz, Tomasz; Górski, Bogusław; Duda, Roman
2014-09-01
The requirements for environmentally friendly refrigerants promote application of CO2 and water as working fluids. However there are two problems related to that, namely high temperature limit for CO2 in condenser due to the low critical temperature, and low temperature limit for water being the result of high triple point temperature. This can be avoided by application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption high temperature cycle used to cool down the CO2 compression cycle condenser. The adsorption process is powered with a low temperature renewable heat source as solar collectors or other waste heat source. The refrigeration system integrating adsorption and compression system has been designed and constructed in the Laboratory of Thermodynamics and Thermal Machine Measurements of Cracow University of Technology. The heat source for adsorption system consists of 16 tube tulbular collectors. The CO2 compression low temperature cycle is based on two parallel compressors with frequency inverter. Energy efficiency and TEWI of this hybrid system is quite promising in comparison with the compression only systems.
Experimental investigation of the ecological hybrid refrigeration cycle
Cyklis Piotr
2014-09-01
Full Text Available The requirements for environmentally friendly refrigerants promote application of CO2 and water as working fluids. However there are two problems related to that, namely high temperature limit for CO2 in condenser due to the low critical temperature, and low temperature limit for water being the result of high triple point temperature. This can be avoided by application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption high temperature cycle used to cool down the CO2 compression cycle condenser. The adsorption process is powered with a low temperature renewable heat source as solar collectors or other waste heat source. The refrigeration system integrating adsorption and compression system has been designed and constructed in the Laboratory of Thermodynamics and Thermal Machine Measurements of Cracow University of Technology. The heat source for adsorption system consists of 16 tube tulbular collectors. The CO2 compression low temperature cycle is based on two parallel compressors with frequency inverter. Energy efficiency and TEWI of this hybrid system is quite promising in comparison with the compression only systems.
Frequency Response Adaptive Control of a Refrigeration Cycle
Jens G. Balchen
1989-01-01
Full Text Available A technique for the adaptation of controller parameters in a single control loop based upon the estimation of frequency response parameters has been presented in an earlier paper. This paper contains an extension and a generalization of the first method and results in a more versatile solution which is applicable to a wider range of process characteristics. The application of this adaptive control technique is illustrated by a laboratory refrigeration cycle in which the evaporator pressure controls the speed of the compressor.
Highlights: • Thermodynamic analysis of a combined power-absorption cooling system is provided. • Effect of important operating parameters on combined cycle performance is studied. • Compares performance of combined cycle with power cycle without absorption system. • Gives quantitative comparison of power cycle performance with and without water heater. • Analysis on vapor power and water–LiBr absorption refrigeration system is not available. - Abstract: Detail thermodynamic analysis of a combined reheat regenerative steam turbine (ST) based power cycle and water–LiBr vapor absorption refrigeration system (VARS) is presented in this study. The power cycle uses one open and one closed water heater (CWH) for purpose of feed water heating. A parametric analysis is performed to investigate the effects of boiler pressure, fuel flow rate, VARS evaporator cooling load and operating temperatures on performance of the topping power cycle and bottoming VARS. Further a performance comparison of the combined power and cooling plant is made with the power plant (without VARS) to quantify the performance variation due to VARS integration. Comparative performance analysis is also provided for the power plant (without VARS) with and without the CWH in the plant. The analysis indicates that the fuel flow rate and boiler pressure affects only the power cycle performance while the evaporator cooling load and VARS components’ operating temperature has its combined effect both on the power and the cooling system, the evaporator cooling load is the most crucial among them. A sensitive analysis shows that the power and efficiency of the topping cycle change very little with VARS operating temperatures. VARS coefficient of performance is more sensitive to the change in condenser and absorber temperature compared to change in generator and evaporator temperature
In this paper, an auto-cascade ejector refrigeration cycle (ACERC) is proposed to obtain lower refrigeration temperature based on conventional ejector refrigeration and auto-cascade refrigeration principle. The thermodynamic performance of ACERC is investigated theoretically. The zeotropic refrigerant mixture R32 + R236fa is used as its working fluid. A parametric analysis is conducted to evaluate the effects of some thermodynamic parameters on the cycle performance. The study shows that refrigerant mixture composition, condenser outlet temperature and evaporation pressure have effects on performance of ACERC. The theoretical results also indicate that the ACERC can achieve the lowest refrigeration temperature at the temperature level of −30 °C. The application of zeotropic refrigerant mixture auto-cascade refrigeration in the ejector refrigeration cycle can provide a new way to obtain lower refrigeration temperature utilizing low-grade thermal energy. - Highlights: • An auto-cascade ejector refrigerator with R32 + R236fa mixed refrigerant is proposed. • The cycle can obtain a refrigeration temperature at −30 °C temperature range. • The effects of some thermodynamic parameters on the cycle performance are evaluated
This paper presents a new methodology for energy integration of systems that require absorption refrigeration. It allows heat exchange among process hot and cold streams and the integration of excess process heat as well as external utilities provided by solar energy, fossil fuels and biofuels. An optimization formulation is developed to address the multiple objectives of simultaneously minimizing the total annualized cost and the greenhouse gas emissions while the social impact is measured by the number of jobs generated by the project in the entire life cycle. The economic function accounts for the tax credit obtained by the reduction of greenhouse gas emissions when cleaner technologies are used. The proposed model also considers the optimal selection of different types of solar collectors and the optimal time-based usage of solar energy, fossil fuel, and biofuel. Two example problems are presented to show the applicability of the proposed methodology. -- Highlights: ► An approach for the thermal integration of refrigeration processes is proposed. ► Different forms of sustainable energies are considered in the optimization process. ► Economic and environmental objectives are considered quantifying the number of jobs. ► The availability for the different forms of energy is taken into account. ► Results show significant advantages obtained with the proposed approach
A new technology for fishing vessels: the use of ejector expansion refrigeration cycle
Memet, Feiza; Mitu, Daniela Elena
2015-02-01
A challenge that fishing industry is facing is the improvement of the refrigeration technology on board of fishing vessels. This paper deals with vapor compression refrigeration systems included on board of these ships. In these systems, significant thermodynamic losses are encountered in the expansion valve, during throttling process. Because it is possible to improve a thermodynamic process by decreasing irreversibility, in this paper it is used an ejector in order to reduce throttling irreversibility. A new technology results, the use of an ejector as a refrigerant expander leading to the ejector expansion refrigeration cycle. The theoretical study developed here will reveal a performance improvement of the new cycle. Also, because the traditional refrigerant used in marine refrigeration is R 134a, which presents a high value of its Global Warming Potential, the performance analysis is extended for the case of the use of other more environmentally friendly refrigerants: propane and isobutane.
Materials and systems developments on solid absorption refrigeration with CaCl2·xNH3
The paper presents some developments on the stabilization of CaCl2 for use as a solid absorption material in refrigerators, the development of a refrigerator using the stabilized salt, and computer modelling of the refrigerator system. (author). 8 refs, 19 figs
A hybrid system mainly consisting of a PEMFC (proton exchange membrane fuel cell) and an absorption refrigerator is proposed, where the PEMFC directly converts the chemical energy contained in the hydrogen into electrical and thermal energies, and the thermal energy is transferred to drive the bottoming absorption refrigerator for cooling purpose. By considering the existing irreversible losses in the hybrid system, the operating current density region of the PEMFC permits the absorption refrigerator to exert its function is determined and the analytical expressions for the equivalent power output and efficiency of the hybrid system under different operating conditions are specified. Numerical calculations show that the equivalent maximum power density and the corresponding efficiency of the hybrid system can be respectively increased by 5.3% and 6.8% compared to that of the stand-alone PEMFC. Comprehensive parametric analyses are conducted to reveal the effects of the internal irreversibility of the absorption refrigerator, operating current density, operating temperature and operating pressure of the PEMFC, and some integrated parameters related to the thermodynamic losses on the performance of the hybrid system. The model presented in the paper is more general than previous study, and the results for some special cases can be directly derived from this paper. - Highlights: • A CHP system composed of a PEMFC and an absorption refrigerator is proposed. • Current density region enables the absorption refrigerator to work is determined. • Multiple irreversible losses in the system are analytically characterized. • Maximum power density and corresponding efficiency can be increased by 5.3% and 6.8%. • Effects of some designing and operating parameters on the performance are discussed
Thermodynamic Analysis and Comparison on Low Temperature CO2-NH3 Cascade Refrigeration Cycle
查世彤; 马一太; 申江; 李敏霞
2003-01-01
This paper is focused on the cascade refrigeration cycle using natural refrigerant CO2-NH3. The properties of refrigerants CO2 and NH3 are introduced and analyzed.CO2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO2-NH3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH3-NH3 cascade refrigeration cycles, the mass flow rate ratio of CO2-NH3 is larger than those of R13-R22 and NH3-NH3, the theoretical COP of CO2-NH3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH3-NH3 cascade cycle. But the real COP of CO2-NH3 cascade cycle will be higher than those of R13-R22 and NH3-NH3 because the specific volume of CO2 at low temperature does not change much and its dynamic viscosity is also small.
AN EXPERIMENTAL STUDY ON A VAPOR COMPRESSION REFRIGERATION CYCLE BY ADDING INTERNAL HEAT EXCHANGER
Muhammad Asmail Eleiwi
2013-05-01
Full Text Available Thispaper presents practical study to improve the indication COP of a vaporcompression refrigeration cycle in instrumented automobile air conditioner bydesigning internal heat exchanger and installing it in the vapor compressionrefrigeration cycle. Two cases of vapor compression refrigeration cycle were takenin this paper: the first case is thatthe vapor compression refrigeration cycle without internal heat exchanger andin the second case the vapor compressionrefrigeration cycle with heat exchanger ; in these two cases, the temperatureat each point of a vapor compressionrefrigeration cycle, the low and the high pressure ,the indoor temperature andthe outdoor temperature were measured at each time at compressor speed 1450 rpmand 2900 rpm for each blower speed 1, blower speed 2 and blower speed 3.Therefrigerant fluid was used in the vapor compression refrigeration cycle withoutIHE and with IHE is R134a..
Gomes, Alberto Regio; Litch, Andrew D.; Wu, Guolian
2016-03-15
A refrigerator appliance (and associated method) that includes a condenser, evaporator and a multi-capacity compressor. The appliance also includes a pressure reducing device arranged within an evaporator-condenser refrigerant circuit, and a valve system for directing or restricting refrigerant flow through the device. The appliance further includes a controller for operating the compressor upon the initiation of a compressor ON-cycle at a priming capacity above a nominal capacity for a predetermined or calculated duration.
A thermodynamic review of cryogenic refrigeration cycles for liquefaction of natural gas
Chang, Ho-Myung
2015-12-01
A thermodynamic review is presented on cryogenic refrigeration cycles for the liquefaction process of natural gas. The main purpose of this review is to examine the thermodynamic structure of various cycles and provide a theoretical basis for selecting a cycle in accordance with different needs and design criteria. Based on existing or proposed liquefaction processes, sixteen ideal cycles are selected and the optimal conditions to achieve their best thermodynamic performance are investigated. The selected cycles include standard and modified versions of Joule-Thomson (JT) cycle, Brayton cycle, and their combined cycle with pure refrigerants (PR) or mixed refrigerants (MR). Full details of the cycles are presented and discussed in terms of FOM (figure of merit) and thermodynamic irreversibility. In addition, a new method of nomenclature is proposed to clearly identify the structure of cycles by abbreviation.
The Use of Water Vapor as a Refrigerant: Impact of Cycle Modifications on Commercial Viability
Brandon F. Lachner, Jr.; Gregory F. Nellis; Douglas T. Reindl
2004-08-30
This project investigated the economic viability of using water as the refrigerant in a 1000-ton chiller application. The most attractive water cycle configuration was found to be a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers. Component level models were developed that could be used to predict the size and performance of the compressors and heat exchangers in this cycle as well as in a baseline, R-134a refrigeration cycle consistent with chillers in use today. A survey of several chiller manufacturers provided information that was used to validate and refine these component models. The component models were integrated into cycle models that were subsequently used to investigate the life-cycle costs of both an R-134a and water refrigeration cycle. It was found that the first cost associated with the water as a refrigerant cycle greatly exceeded the savings in operating costs associated with its somewhat higher COP. Therefore, the water refrigeration cycle is not an economically attractive option to today's R-134a refrigeration system. There are a number of other issues, most notably the requirements associated with purging non-condensable gases that accumulate in a direct contact heat exchanger, which will further reduce the economic viability of the water cycle.
Thermodynamic analysis of transcritical CO2 refrigeration cycle with an ejector
A comparative study on transcritical carbon dioxide refrigeration cycle with ejector and with throttling valve was performed by the first and second laws of thermodynamics in theory. The effects of the entrainment ratio of the ejector, heat rejection pressure, outlet temperature of gas cooler and evaporating temperature on the coefficient of performance (COP) and exergy loss were investigated in transcritical carbon dioxide refrigeration cycle with ejector and with throttling valve. It is found that ejector instead of throttling valve can reduce more 25% exergy loss and increase COP more 30%. In addition, critical entrainment ratio of the ejector, optimal heat rejection pressure and critical outlet temperature of gas cooler affects COP greatly for the transcritical carbon dioxide refrigerating cycle with ejector. - Research highlights: →Transcritical CO2 refrigeration cycle with ejector was analyzed by the laws of thermodynamics. → The ejector instead of throttling valve reduces more 25% exergy loss and increases COP more 30% in transcritical CO2 refrigeration cycle. → COP of transcritical CO2 refrigeration cycle with ejector was affected greatly by entrainment ratio of ejector, rejection pressure and outlet temperature of gas cooler. → Running condition of transcritical CO2 refrigeration cycle with ejector is limited by critical entrainment ratio of the ejector.
Schmid, Fabian; Bierling, Bernd; Spindler, Klaus [Stuttgart Univ. (Germany). Inst. fuer Thermodynamik und Waermetechnik (ITW)
2012-07-01
The diffusion-absorption refrigeration process offers the possibility of a wear-free refrigeration system without electricity and noise. At the Institute for Thermodynamics and Thermal Engineering (Stuttgart, Federal Republic of Germany), a decentralized solar refrigeration system is developed based on this process. The expeller and the thermosiphon pump of this process are integrated in the collector, and thus are heated directly. The diffusion-absorption refrigeration process also can be used for domestic water heating by means of a second cycle in the collector. A cooling capacity of 400 W is to be achieved for each solar collector (2.5 m{sup 2}). Several refrigeration systems can be modular interconnected for higher cooling capacities. As part of the DKV Conference 2011, the construction of the plant, the first measurement data and results were presented. Since then, both the cooling capacity and the coefficient of performance of the diffusion-absorption refrigeration system could be increased significantly. For this, solvent heat exchanger, evaporator, absorber and gas heat exchanger have been optimized in terms of system efficiency. In addition, a stable system operation could be achieved by means of a bypass line. About this line, an exaggerated refrigerant already is removed in the solvent heat exchanger. In addition, a condensate pre-cooler was integrated in order to increase the efficiency. For a detailed investigation of the auxiliary gas cycle facilities, the volume flow and the concentration of the auxiliary gas circuit were examined under utilization of an ultrasonic sensor. In order to evaluate the influence factors by means of a parametric study, the mass transfer in the auxiliary gas circuit was simulated using the two-fluid model. The results of these studies, the current system configuration and the current results are presented in the contribution under consideration.
Application of waste heat powered absorption refrigeration system to the LNG recovery process
Kalinowski, Paul; Hwang, Yunho; Radermacher, Reinhard [Center for Environmental Energy Engineering, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742 (United States); Al Hashimi, Saleh; Rodgers, Peter [The Petroleum Institute, Abu Dhabi (United Arab Emirates)
2009-06-15
The recovery process of the liquefied natural gas requires low temperature cooling, which is typically provided by the vapor compression refrigeration systems. The usage of an absorption refrigeration system powered by waste heat from the electric power generating gas turbine could provide the necessary cooling at reduced overall energy consumption. In this study, a potential replacement of propane chillers with absorption refrigeration systems was theoretically analyzed. From the analysis, it was found that recovering waste heat from a 9 megawatts (MW) electricity generation process could provide 5.2 MW waste heat produced additional cooling to the LNG plant and save 1.9 MW of electricity consumption. Application of the integrated cooling, heating, and power is an excellent energy saving option for the oil and gas industry. (author)
FUZZY THERMOECONOMIC APPROACH TO NANOFLUID SELECTION IN VAPOR COMPRESSION REFRIGERATION CYCLE
D. Kuleshov
2014-06-01
Full Text Available The working fluid selection in the vapour compression refrigeration cycles has been studied as a fuzzy thermoeconomic optimization problem. Three criteria: thermodynamic (COP Coefficient Of Performance, economic (LCC Life Cycle Cost, and ecologic (GWP – Global Warming Potential are chosen as target functions. The decision variables X as an information characteristics of desired refrigerant are presented by its critical parameters and normal boiling temperature. Local criteria are expressed via thermodynamic properties restored from information characteristics of refrigerant X, as well as life cycle costs are calculated by the standard economic relationships. GWP values are taken from the refrigerant database. Class of substances under consideration is presented by the natural refrigerant R600a embedded with nanostructured materials.
The Effects of Internal and External Irreversibility of a Vapor Compression Refrigeration Cycle
Wang, Fu-Jen; Chiou, Jeng-Shing
The concept of finite-time thermodynamics is employed to investigate the optimal refrigeration rate for an irreversible refrigeration cycle. The heat transfer between the system (internal) fluid and cooling (external) fluid takes place at the actual heat exchanger, which has the finite-size heat transfer area and the realistic heat transfer effectiveness. The internal irreversibility results from the compression process and the expansion process are also considered. The optimal refrigeration rate is calculated and expressed in terms of the irreversibility parameter (Ir), coefficient of performance (COP), the time ratio(γ) of heat transfer processes and the effectiveness of heat exchanger. The derived COP which consider both the external and internal irreversibility can thus be considered as the benchmark value for a practical refrigeration cycle, and the parametric study can provide the basis for both determination of optimal operating conditions and design of a practical refrigeration cycle.
Harris, R.L.; Olson, G.K.; Mah, C.S.; Bujalski, J.H.
1977-11-01
The first step in the economic analysis of the integration of geothermally powered absorption refrigeration into a food processing plant was an evaluation of the potential geothermal sites in the Western United States. The evaluation covered availability of raw materials, transportation, adequate geothermal source, labor, and other requirements for food processing plants. Several attractive geothermal sites were identified--Raft River, Idaho; Sespe Hot Springs, California; Vale Hot Springs, Oregon; Weisler-Crane Creek, Idaho; Cosco Hot Springs, California; and the Imperial Valley, California. The most economically attractive food processing industry was then matched to the site based on its particular energy, raw material, and transportation requirements. The more promising food processors identified were for frozen potato or vegetable products, freeze-dried products, and meat processing. For the refrigeration temperature range of +32/sup 0/F to -40/sup 0/F and geothermal temperature range of 212/sup 0/F to 300/sup 0/F, an absorption refrigeration system had to be identified, designed, and evaluated. Both the conventional ammonia/water and an organic absorption refrigeration system using monochlorodifluoromethane (R-22) as the refrigerant and dimethyl formamide (DMF) as the absorbent were studied. In general, only a 60/sup 0/F to 100/sup 0/F temperature drop would be effectively used for refrigeration leaving the remainder of the allowable temperature drop available for other use. The economic evaluation of the geothermal system installed in a food processing plant required the comparison of several principal alternatives. These alternatives were evaluated for three different food processing plants located at their optimum geothermal site: a forzen potato product processing plant located at Raft River, Idaho; a freeze-dried product plant located at Sespe Hot Springs, California; a beef slaughter operation located in the Imperial Valley of California. (JGB)
Performance evaluation of an ejector subcooled vapor-compression refrigeration cycle
Highlights: • An ejector subcooled vapor-compression refrigeration cycle is proposed. • The performance of the cycle with ejector subcooling is evaluated theoretically. • Increase in refrigeration capacity can be achieved by the ejector subcooled cycle. • The new cycle exhibits higher COP compared to the basic single-stage cycle. • Performance of the new cycle depends on the operation pressures of the ejector. - Abstract: In this study, a novel vapor-compression refrigeration cycle with mechanical subcooling using an ejector is proposed to improve the performance of a conventional single-stage vapor-compression refrigeration cycle. In the theoretical study, a mathematical model is developed to predict the performance of the cycle by using R404A and R290, and then compared with that of the conventional refrigeration cycle. The simulation results show that the performance of the ejector subcooled cycle is better than that of the conventional cycle. When the evaporator temperature ranges from −40 to −10 °C and the condenser temperature is 45 °C, the novel cycle displays volumetric refrigeration capacity improvements of 11.7% with R404A and 7.2% with R290. And the novel cycle achieves COP improvements of 9.5% with R404A and 7.0% with R290. In addition, the improvement of the COP and cooling capacity of this novel cycle largely depends on the operation pressures of the ejector. The potential practical advantages offered by the cycle may be worth further attention in future studies
Nat Suvarnakuta; Nutthanun Keerlatiyadatanapat; Thanarath Sriveerakul
2014-01-01
This paper presents the COP prediction of an ejector refrigeration cycle combined with a vapour compression cycle for automotive air conditioning. Using computational fluid dynamics (CFD) technique, the performance of an ejector was analyzed in term of the entrainment ratio (Rm) and critical back pressure (CBP). The results from this study were compared with a previous study of combined ejector refrigeration system for automotive air conditioning application [1] which the entrainment ratio (R...
Bartolomeu, Lair S.; Torres, Ednildo A. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Escola Politecnica. Lab. de Energia e Gas; Silva, Gabriel F. [Universidade Federal de Sergipe (UFS), Aracaju, SE (Brazil); Martins, Ronaldo M. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Materiais. CQDM; Campos, Michel F. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Gerencia de Tecnologia do Gas Natural. Rede GasEnergia
2004-07-01
This work has the purpose to analyze an alternative method in the conservation of tropical fruits in chamber cooled through the technology of use of the natural gas as energy source. The study it was carried through in chiller of absorption, Robur model, of 5TR, which meets in the campus of the Federal University of Sergipe (UFS/LEG). The energy analysis had as objective to study the process involving the cycle and its components. Of the analysis of first law was gotten a power of refrigeration of 8,8 kW and a COP=0,32 and the analysis of second law {beta}=0,29. The exergetic analysis had for intention to evaluate the amount and the quality of the energy in the system. The heat generator was the component that presented the biggest irreversibility, whose relation with the total irreversibility was about 70%. In the absorber the lesser exergetic efficiency was verified. Project is supported by the GasEnergia/PETROBRAS. (author)
Study of optimal discharge pressure of compressor in CO2 refrigerating trans-critical cycle
Fu Liehu; Wang Ruixiang; Li Qingdong; Wu Yezheng
2008-01-01
In this paper, a carbon dioxide trans-critical refrigerating system which is different from a conventional subcritical refrigerating cycle was studied. The trans-critical carbon dioxide refrigerating systems are based on the Gustav Lorntzen cycle. Emphasis was focused on how to determine the optimal discharge pressure of compressor in CO2 trans-critical cycle. The factors related with the optimal discharge pressure were analyzed. A formula was developed based on cycle simulation, which could be used to predict the optimal discharge pressure of a basic CO2 trans-critical cycle. After further studies on CO2 trans-critical cycles with a regenerator or expander, two more formulas were also developed. These formulas could provide an access to improve the COP of CO2 trans-critical cycle.
Thermodynamic Investigation of Two-Stage Absorption Refrigeration System Connected by a Compressor
L. Kairouani
2005-01-01
Full Text Available The present work is to analyze a two-stage cycle based on the ammonia-water absorption system, with intermediate compression. The two generators of the system are heated by geothermal energy at low temperature. The study shows that this system makes it possible at lower generator temperature, under the limits permitted by the systems suggested up to now. For Tg = 335 K, Tc = Ta = 308 K and Te = 263 K, based on the electric consumption, the system efficiency is 8.2. The comparative study of the hybrid system and vapor compression systems shows the superiority of the proposed system. Supplied by the geothermal sources of the Tunisian south, the system makes it possible to obtain for a pilot geothermal station, a production of 75 tons of ice per day. The greenhouse gas emissions should thus be reduced by about 2.38 tons of CO2 per day. Therefore, based on the typical geothermal energy sources in Tunisia which present a global refrigeration potential of 4.4 MW, the daily quantity of ice that could be produced is about 865 tons. The greenhouse gas emissions should thus be reduced by about 10,000 tons of CO2 per year.
Neon turbo-Brayton cycle refrigerator for HTS power machines
Hirai, Hirokazu; Hirokawa, M.; Yoshida, Shigeru; Nara, N.; Ozaki, S.; Hayashi, H.; Okamoto, H.; Shiohara, Y.
2012-06-01
We developed a prototype turbo-Brayton refrigerator whose working fluid is neon gas. The refrigerator is designed for a HTS (High Temperature Superconducting) power transformer and its cooling power is more than 2 kW at 65 K. The refrigerator has a turboexpander and a turbo-compressor, which utilize magnetic bearings. These rotational machines have no rubbing parts and no oil-components. Those make a long maintenance interval of the refrigerator. The refrigerator is very compact because our newly developed turbo-compressor is volumetrically smaller than a displacement type compressor in same operating specification. Another feature of the refrigerator is a wide range operation capability for various heat-loads. Cooling power is controlled by the input-power of the turbo-compressor instead of the conventional method of using an electric heater. The rotational speed of the compressor motor is adjusted by an inverter. This system is expected to be more efficient. We show design details, specification and cooling test results of the new refrigerator in this paper.
Lingen Chen, Xuxian Kan, Fengrui Sun, Feng Wu
2013-01-01
The operation of a universal steady flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, two constant thermal-capacity cooling branches and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate optimization criterion as the objective. The relations between the profit rate and the temperature ra...
Zhenying Zhang; Lirui Tong; Xingguo Wang
2015-01-01
Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external interco...
The general performance characteristics of a two-stage magnetic Brayton refrigeration cycle consisting of three constant magnetic fields and three irreversible adiabatic processes are investigated. Based on the thermodynamic properties of a magnetic material and the irreversible cycle model of a two-stage Brayton refrigerator, expressions for the cooling load and coefficient of performance of the refrigeration system are derived. The influence of the finite-rate heat transfer in the heat exchange processes, irreversibilities in the three adiabatic processes, ratios of two magnetic fields in the three constant magnetic field processes, and heat leak losses between two heat reservoirs on the performance of the two-stage magnetic Brayton refrigeration cycle are analyzed in detail. Some important performance curves, which can reveal the general characteristics of the refrigeration system, are presented and the maximum values of cooling load and coefficient of performance are numerically calculated. The optimal choices and matches of other parameters at the maximum cooling load or the maximum coefficient of performance are discussed and the optimally operating regions of some important parameters in the refrigeration system are determined. The results obtained here are compared with those derived from other models of the magnetic Brayton refrigeration cycles, and consequently, the advantage of an inter-cooled process is expounded.
Thermoeconomic optimization of subcooled and superheated vapor compression refrigeration cycle
An exergy-based thermoeconomic optimization application is applied to a subcooled and superheated vapor compression refrigeration system. The advantage of using the exergy method of thermoeconomic optimization is that various elements of the system-i.e., condenser, evaporator, subcooling and superheating heat exchangers-can be optimized on their own. The application consists of determining the optimum heat exchanger areas with the corresponding optimum subcooling and superheating temperatures. A cost function is specified for the optimum conditions. All calculations are made for three refrigerants: R22, R134a, and R407c. Thermodynamic properties of refrigerants are formulated using the Artificial Neural Network methodology
Reduction of Thermal Energy Loss in Cyclic Operation of Refrigeration Cycle
Gommori, Masahiko; Kogure, Hiroshi; Hara, Toshitsugu
Investigation of thermal energy loss in cyclic operation of refrigeration cycle in a refrigerator-freezer were made. The energy loss was found to consist of three parts ; hot gas-refrigerant entering loss, cooling lag loss, and evaporator superheat loss. Hot gas-refrigerant entering loss is occured when high temperature gaseous refrigerant in a condenser flows into an evaporator to heat up the refrigerant in it. Main results are as follows ; 1) Hot gas-refrigerant entering loss, which was the most dominant, was found to be from 7.6 to 12.3% (for reciprocationg compressor) and from 11.9 to 17.4% (for rotary compressor) of the cooling load, respectively. 2) The thermal energy loss was confirmed to be able to be reduced when hot gas-refrigerant was restricted to flow in the evaporator with control valves. It follows to reduce electrical power consumption by 10 and 15%, in the case of reciprocating compressor and of rotary compressor, respectively. 3) Cycle frequency was made to be optimized theoretically and experimentally in the case of with and without valves.
Second law comparison of single effect and double effect vapour absorption refrigeration systems
Gomri, Rabah [Engineering Faculty, Department of Genie Climatique, Constantine University, 25000 Constantine (Algeria)
2009-05-15
In this paper a comparative study between single effect and double effect absorption refrigeration systems with identical cold output is carried out. Simulation results were used to study the influence of the various operating parameters on the performance coefficient, the thermal loads of the components, exergetic efficiency (rational efficiency) and the total change in exergy of the two systems. It is concluded that the COP of double effect system is approximately twice the COP of single effect system but the exergetic efficiency of double effect system increase slightly compared to the exergetic efficiency of single effect system. It is found that for each condenser and evaporator temperature, there is an optimum generator temperature where the total change in exergy of the single effect and double effect absorption refrigeration systems is minimum. At this point the COP and exergetic efficiency of the systems become maximum. In this study and when the evaporation temperature is varied from 4 C to 10 C, condenser and absorber temperatures are varied from 33 C to 39 C and generator (HPG) temperature is varied from 60 C to 190 C the maximum COP values of the single effect refrigeration systems are in the range of 0.73-0.79 and for double effect refrigeration systems are in the range of 1.22-1.42. The maximum exergetic efficiency values of the single effect refrigeration systems are in the range of 12.5-23.2% and for double effect refrigeration systems are in the range of 14.3-25.1%. (author)
Optimal configuration for a finite low-temperature source refrigerator cycle with heat transfer law
Jun Li, Lingen Chen, Yanlin Ge, Fengrui Sun
2016-01-01
Full Text Available The optimal configuration of a refrigeration cycle operating between a finite low-temperature source and an infinite high-temperature sink are derived by using finite time thermodynamics based on a complex heat transfer law, including Newtonian heat transfer law, linear phenomenological heat transfer law, radiative heat transfer law, Dulong-Petit heat transfer law, generalized convective heat transfer law and generalized radiative heat transfer law. In the refrigeration cycle model the only irreversibility of finite rate heat transfer is considered. The optimal relation between cooling load and coefficient of performance (COP of the refrigeration cycle is also derived by using an equivalent temperature of low-temperature source. The obtained results include those with various heat transfer laws and infinite low-temperature source, and can provide some theoretical guidelines for the designs of practical refrigerators.
Mehrpooya, Mehdi; Dehghani, Hossein; Ali Moosavian, S. M.
2016-02-01
A combined system containing solid oxide fuel cell-gas turbine power plant, Rankine steam cycle and ammonia-water absorption refrigeration system is introduced and analyzed. In this process, power, heat and cooling are produced. Energy and exergy analyses along with the economic factors are used to distinguish optimum operating point of the system. The developed electrochemical model of the fuel cell is validated with experimental results. Thermodynamic package and main parameters of the absorption refrigeration system are validated. The power output of the system is 500 kW. An optimization problem is defined in order to finding the optimal operating point. Decision variables are current density, temperature of the exhaust gases from the boiler, steam turbine pressure (high and medium), generator temperature and consumed cooling water. Results indicate that electrical efficiency of the combined system is 62.4% (LHV). Produced refrigeration (at -10 °C) and heat recovery are 101 kW and 22.1 kW respectively. Investment cost for the combined system (without absorption cycle) is about 2917 kW-1.
This study reports a comparison from the first and second law of thermodynamics of a conventional vapor compression cooling system, a compression-absorption single-stage (CASS) system, and a compression-absorption double-stage (CADS) system operating with CO2 and R134a in the compression cycle and H2O/LiBr in the absorption cycles. The CADS system is being by the first time proposed in the literature. The performance of the systems were analyzed as function of diverse operating parameters. It was found that the electrical energy consumption in the refrigeration cycles was about 45% lower than in the classical compression refrigeration cycles using CO2 and R134a as refrigerants under the same operating conditions. The results showed that the COP for the CADS could be 50% higher than those obtained with the CASS system. The systems operating with R134a always achieved higher COP than those obtained using CO2. From the exergy analysis it was clear that the highest irreversibilities occurs in the absorber and the evaporator for both mixtures. It was also found that the irreversibilities of the proposed system using R134a in the compression cycle were 17% lower than those obtained with the system using CO2 - Highlights: • A compression-absorption double-stage (CADS) system is by the first time proposed. • The compression power in cascade cycles was 45% lower than in compression cycles. • The COP for proposed system was up to 45.2% higher than those with other systems. • The systems operating with R134a achieved higher COP than those obtained using CO2. • The irreversibilities for the CADS using R134a were 17% lower than using CO2
Coherence-assisted single-shot cooling by quantum absorption refrigerators
Mitchison, Mark T.; Woods, Mischa P.; Prior, Javier; Huber, Marcus
2015-01-01
The extension of thermodynamics into the quantum regime has received much attention in recent years. A primary objective of current research is to find thermodynamic tasks which can be enhanced by quantum mechanical effects. With this goal in mind, we explore the finite-time dynamics of absorption refrigerators composed of three qubits. The aim of this finite-time cooling is to reach low temperatures as fast as possible and subsequently extract the cold particle to exploit it for information ...
Karno, Ali; Ajib, Salman
2008-05-01
A theoretical analysis was undertaken to examine the efficiency characteristics of acetone-zinc bromide solutions for an absorption refrigeration machine, using low generator temperatures (47 60°C), which allows the use of flat plate solar collectors. The results of the simulation were confirmed with an experimental investigation. The main results showed that the solution is well suited to operate the machine at low temperatures (higher than 50°C).
In China, the application of small size gas-fired air-cooled absorption refrigeration systems as an alternative for electric compression air conditioning systems has shown broad prospects due to occurrence of electricity peak demand in Chinese big cities and lack of water resources. However, for conventional air-cooled absorption refrigeration systems, it is difficult to enhance the heat and mass transfer process in the falling film absorber, and may cause problems, for example, remarkable increase of pressure, temperature and concentration in the generators, risk of crystallization, acceleration of corrosion, degradation of performance, and so on. This paper presents a gas-fired air-cooled adiabatic absorption refrigeration system using lithium bromide-water solutions as its working fluid, which is designed with a cooling capacity of 16 kW under standard conditions. The system has two new features of waste heat recovery of condensed water from generator and an adiabatic absorber with an air cooler. Performance simulation and characteristic analysis are crucial for the optimal control and reliability of operation in extremely hot climates. A methodology is presented to simulate thermodynamic performance of the system. The influences of outdoor air temperature on operation performances of the system are investigated
Annamalai, Mani; Pasupathy, Balamurugan
2012-01-01
Vapour absorption refrigeration systems (VARS) has regained the attention due to their potential for renewable/waste heat utilization. To improve the efficiency of these systems, it becomes obligatory to make component level studies on processes. In this present study, investigations on the heat and mass transfer in compact generator of the vapour absorption refrigeration system have been carried out using R134a-Dimethyl formamide (DMF). An experimental facility of VARS has been fabricated us...
The performance characteristics of an irreversible quantum Otto harmonic refrigeration cycle
无
2009-01-01
In this paper, an irreversible quantum Otto refrigeration cycle working with harmonic systems is established. Base on Heisenberg quantum master equation, the equations of motion for the set of harmonic systems thermodynamic observables are derived. The simulated diagrams of the quantum Otto refrigeration cycle are plotted. The relationship between average power of friction, cooling rate, power input, and the time of adiabatic process is analyzed by using numerical calculation. Moreover, the influence of the heat conductance and the time of iso-frequency process on the performance of the cycle is discussed.
The performance characteristics of an irreversible quantum Otto harmonic refrigeration cycle
HE JiZhou; HE Xian; TANG Wei
2009-01-01
In this paper,an irreversible quantum Otto refrigeration cycle working with harmonic systems is estab-lished.Base on Heisenberg quantum master equation,the equations of motion for the set of harmonic systems thermodynamic observables are derived.The simulated diagrams of the quantum Otto refrig-eration cycle are plotted.The relationship between average power of friction,cooling rate,power input,and the time of adiabatic process is analyzed by using numerical calculation.Moreover,the influence of the heat conductance and the time of iso-frequency process on the performance of the cycle is dis-cussed.
Optimal analysis on the performance of an irreversible harmonic quantum Brayton refrigeration cycle.
Lin, Bihong; Chen, Jincan
2003-11-01
An irreversible model of a quantum refrigeration cycle working with many noninteracting harmonic oscillators is established. The refrigeration cycle consists of two adiabatic and two constant-frequency processes. The general performance characteristics of the cycle are investigated, based on the quantum master equation and the semigroup approach. The expressions for several important performance parameters such as the coefficient of performance, cooling rate, power input, and rate of entropy production are derived. By using numerical solutions, the cooling rate of the refrigeration cycle subject to finite cycle duration is optimized. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal region of the coefficient of performance and the optimal ranges of temperatures of the working substance and times spent on the two constant-frequency processes are determined. Moreover, the optimal performance of the cycle in the high-temperature limit is compared with that of a classical Brayton refrigerator working with an ideal gas. The results obtained here show that in the high-temperature limit a harmonic quantum Brayton cycle may be equivalent to a classical Brayton cycle. PMID:14682856
Pilatowsky, I.; Gamboa, S.A.; Rivera, W. [Centro de Investigacion en Energia - UNAM, Temixco, Morelos (Mexico); Romero, R.J. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas - UAEM, Cuernavaca, Morelos (Mexico); Isaza, C.A. [Universidad Pontificia Bolivariana, Medellin (Colombia). Instituto de Energia y Termodinamica; Sebastian, P.J. [Centro de Investigacion en Energia - UNAM, Temixco, Morelos (Mexico); Cuerpo Academico de Energia y Sustentabilidad-UP Chiapas, Tuxtla Gutierrez, Chiapas (Mexico); Moreira, J. [Cuerpo Academico de Energia y Sustentabilidad-UP Chiapas, Tuxtla Gutierrez, Chiapas (Mexico)
2007-10-15
In this work, a computer simulation program was developed to determine the optimum operating conditions of an air conditioning system during the co-generation process. A 1 kW PEMFC was considered in this study with a chemical/electrical theoretical efficiency of 40% and a thermal efficiency of 30% applying an electrical load of 100%. A refrigeration-absorption cycle (RAC) operating with monomethylamine-water solutions (MMA-WS), with low vapor generation temperatures (up to 80 C) is proposed in this work. The computer simulation was based on the refrigeration production capacity at the maximum power capacity of the PEMFC. Heat losses between the fuel cell and the absorption air conditioning system at standard operating conditions were considered to be negligible. The results showed the feasibility of using PEMFC for cooling, increasing the total efficiency of the fuel cell system. (author)
Lingen Chen, Xuxian Kan, Fengrui Sun, Feng Wu
2013-01-01
Full Text Available The operation of a universal steady flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, two constant thermal-capacity cooling branches and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate optimization criterion as the objective. The relations between the profit rate and the temperature ratio of working fluid, between the COP (coefficient of performance and the temperature ratio of working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit rate and the utilization factor (COP for endoreversible refrigeration cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, performance analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical example. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson, Dual and Brayton refrigeration cycles.
A new combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces both power output and refrigeration output simultaneously. It can be driven by the flue gas of gas turbine or engine, solar energy, geothermal energy and industrial waste heats. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. And a parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the performance of the combined cycle. In addition, a parameter optimization is achieved by means of genetic algorithm to reach the maximum exergy efficiency. The results show that the biggest exergy loss due to the irreversibility occurs in heat addition processes, and the ejector causes the next largest exergy loss. It is also shown that the turbine inlet pressure, the turbine back pressure, the condenser temperature and the evaporator temperature have significant effects on the turbine power output, refrigeration output and exergy efficiency of the combined cycle. The optimized exergy efficiency is 27.10% under the given condition.
Chen, Lingen; Kan, Xuxian; Sun, Fengrui; Wu, Feng [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)
2013-07-01
The operation of a universal steady flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, two constant thermal-capacity cooling branches and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate optimization criterion as the objective. The relations between the profit rate and the temperature ratio of working fluid, between the COP (coefficient of performance) and the temperature ratio of working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit rate) and the utilization factor (COP) for endoreversible refrigeration cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, performance analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical example. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson, Dual and Brayton refrigeration cycles.
Brown, Timothy D.; Bruno, Nickolaus M.; Chen, Jing-Han; Karaman, Ibrahim; Ross, Joseph H.; Shamberger, Patrick J.
2015-09-01
In giant magnetocaloric effect (GMCE) materials a large entropy change couples to a magnetostructural first-order phase transition, potentially providing a basis for magnetic refrigeration cycles. However, hysteresis loss greatly reduces the availability of refrigeration work in such cycles. Here, we present a methodology combining a Preisach model for rate-independent hysteresis with a thermodynamic analysis of nonequilibrium phase transformations which, for GMCE materials exhibiting hysteresis, allows an evaluation of refrigeration work and efficiency terms for an arbitrary cycle. Using simplified but physically meaningful descriptors for the magnetic and thermal properties of a Ni45Co5Mn36.6In13.4 at.% single-crystal alloy, we relate these work/efficiency terms to fundamental material properties, demonstrating the method's use as a materials design tool. Following a simple two-parameter model for the alloy's hysteresis properties, we compute and interpret the effect of each parameter on the cyclic refrigeration work and efficiency terms. We show that hysteresis loss is a critical concern in cycles based on GMCE systems, since the resultant lost work can reduce the refrigeration work to zero; however, we also find that the lost work may be mitigated by modifying other aspects of the transition, such as the width over which the one-way transformation occurs.
Quantum refrigeration cycles using spin-1/2 systems as the working substance.
He, Jizhou; Chen, Jincan; Hua, Ben
2002-03-01
The cycle model of a quantum refrigerator composed of two isothermal and two isomagnetic field processes is established. The working substance in the cycle consists of many noninteracting spin-1/2 systems. The performance of the cycle is investigated, based on the quantum master equation and semigroup approach. The general expressions of several important performance parameters, such as the coefficient of performance, cooling rate, and power input, are given. Especially, the case at high temperatures is analyzed in detail. The results obtained are further generalized and discussed, so that they may be directly used to describe the performance of the quantum refrigerator using spin-J systems as the working substance. Finally, the optimum characteristics of the quantum Carnot refrigerator are derived simply. PMID:11909203
Brask, Jonatan Bohr; Brunner, Nicolas
2015-12-01
A small quantum absorption refrigerator, consisting of three qubits, is discussed in the transient regime. We discuss time scales for coherent dynamics, damping, and approach to the steady state, and we study cooling and entanglement. We observe that cooling can be enhanced in the transient regime, in the sense that lower temperatures can be achieved compared to the steady-state regime. This is a consequence of coherent dynamics but can occur even when this dynamics is strongly damped by the dissipative thermal environment, and we note that precise control over couplings or timing is not needed to achieve enhanced cooling. We also show that the amount of entanglement present in the refrigerator can be much larger in the transient regime compared to the steady state. These results are of relevance to future implementations of quantum thermal machines.
Wang, Hao; Wu, GuoXing
2012-02-01
A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established, in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically. Expressions for the COP, cooling rate, power input, the minimum ratio of the two magnetic fields, etc., are derived. It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable. It is important that we have obtained several optimal criteria, which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator. The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.
Simplified Helium Refrigerator Cycle Analysis Using the `Carnot Step'
P. Knudsen; V. Ganni
2006-05-01
An analysis of the Claude form of an idealized helium liquefier for the minimum input work reveals the ''Carnot Step'' for helium refrigerator cycles. As the ''Carnot Step'' for a multi-stage polytropic compression process consists of equal pressure ratio stages; similarly for an idealized helium liquefier the ''Carnot Step'' consists of equal temperature ratio stages for a given number of expansion stages. This paper presents the analytical basis and some useful equations for the preliminary examination of existing and new Claude helium refrigeration cycles.
Thermodynamic performance analysis of a vapor compression–absorption cascaded refrigeration system
Highlights: • Study includes first and second law analysis with alternatives refrigerants. • Power consumption in cascaded system is 61% less than vapor compression system. • COP of compression system is improved by 155% with cascaded absorption system. • Condenser is more sensitive to external fluid temperature as compare to evaporator. - Abstract: In the present study, a thermodynamic model for cascaded vapor compression–absorption system (CVCAS) has been developed which consists of a vapor compression refrigeration system (VCRS) coupled with single effect vapor absorption refrigeration system (VARS). Based on first and second laws, a comparative performance analysis of CVCAS and an independent VCRS has been carried out for a design capacity of 66.67 kW. The results show that the electric power consumption in CVCAS is reduced by 61% and COP of compression section is improved by 155% with respect to the corresponding values pertaining to a conventional VCRS. However there is a trade-off between these parameters and the rational efficiency which is found to decrease to half of that for a VCRS. The effect of various operating parameters, i.e., superheating, subcooling, cooling capacity, inlet temperature and the product of effectiveness and heat capacitance of external fluids are extensively studied on the COP, total irreversibility and rational efficiency of the CVCAS. Besides, the performance of environment friendly refrigerants such as R410A, R407C and R134A is found to be almost at par with that of R22. Hence, all the alternative refrigerants selected herein can serve as potential substitutes for R22. Furthermore, it has been found that reducing the irreversibility rate of the condenser by one unit due to decrease in condenser temperature depicted approximately 3.8 times greater reduction in the total irreversibility rate of the CVCAS, whereas unit reduction in the evaporator’s irreversibility rate due to increase in evaporator temperature reduced
Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander
Zhenying Zhang; Lili Tian
2014-01-01
The impulse turbo expander (ITE) is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reductio...
First Law Analysis of a Two-stage Ejector-vapor Compression Refrigeration Cycle working with R404A
Feiza Memet; Daniela-Elena Mitu
2011-01-01
The traditional two-stage vapor compression refrigeration cycle might be replaced by a two-stage ejector-vapor compression refrigeration cycle if it is aimed the decrease of irreversibility during expansion. In this respect, the expansion valve is changed with an ejector. The performance improvement is searched in the case of choosing R404A as a refrigerant. Using the ejector as an expansion device ensures a higher value for COP compared to the traditional case. On the basis...
Experimental simulation of a magnetic refrigeration cycle in high magnetic fields
Dilmieva, E. T.; Kamantsev, A. P.; Koledov, V. V.; Mashirov, A. V.; Shavrov, V. G.; Cwik, J.; Tereshina, I. S.
2016-01-01
The complete magnetic refrigeration cycle has been simulated on a sample of gadolinium in magnetic fields of a Bitter coil magnet up to 12 T. The total change of temperature of the sample during the cycle is a consequence of magnetic refrigeration, and the dependence of the magnetization of the sample on the magnetic field exhibits a hysteretic behavior. This makes it possible to determine the work done by the magnetic field on the sample during the magnetic refrigeration cycle and to calculate the coefficient of performance of the process. In a magnetic field of 2 T near the Curie temperature of gadolinium, the coefficient of performance of the magnetic refrigeration is found to be 92. With an increase in the magnetic field, the coefficient of performance of the process decreases sharply down to 15 in a magnetic field of 12 T. The reasons, for which the coefficient of performance of the magnetic refrigeration is significantly below the fundamental limitations imposed by the reversed Carnot theorem, have been discussed.
Highlights: • It addresses the size and cost estimation of cascaded refrigeration system. • Cascaded system is a promising decarburizing and energy efficient technology. • Second law analysis is carried out with modified Gouy-Stodola equation. • The total annual cost of plant operation is optimized in present work. - Abstract: This paper addresses the size and cost estimation of vapor compression–absorption cascaded refrigeration system (VCACRS) for water chilling application taking R410a and water–LiBr as refrigerants in compression and absorption section respectively which can help the design engineers in manufacturing and experimenting on such kind of systems. The main limitation in the practical implementation of VCACRS is its size and cost which are optimized in the present work by implementing Direct Search Method in non-linear programming (NLP) mathematical model of VCACRS. The main objective of optimization is to minimize the total annual cost of system which comprises of costs of exergy input and capital costs in monetary units. The appropriate set of decision variables (temperature of evaporator, condenser, generator, absorber, cascade condenser, degree of overlap and effectiveness of solution heat exchanger) minimizes the total annual cost of VCACRS by 11.9% with 22.4% reduction in investment cost at the base case whereas the same is reduced by 7.5% with 11.7% reduction in investment cost with reduced rate of interest and increased life span and period of operation. Optimization results show that the more investment cost in later case is well compensated through the performance and operational cost of the system. In the present analysis, optimum cascade condensing temperature is a strong function of period of operation and capital recovery factor. The cascading of compression and absorption systems becomes attractive for lower rate of interest and increase life span and operational period
Design, Fabrication and Performance Evaluation of a Micro-Absorption Refrigerator
Hyginus .U. Ugwu
2012-11-01
Full Text Available Developments in absorption cooling technology present an opportunity to achieve significant improvements on micro-scale to buildings, cooling, heating and power systems for residential and light commercial buildings. Their resultant effects are effective, energy efficient and economical. This study therefore contributes an important knowledge and method in the development, fabrication and application of an absorption refrigerator as a better alternative to the commonly used compressor refrigerators. In its embodiment, the work focuses on the design and fabrication of the absorption chiller system with low or no vibration since there are virtually no moving parts. Also, it dovetailed into the selection of a suitable refrigerant that is economically friendly in order to reduce or eliminate its ozone depleting effect. Consequently, the design was fabricated using adapted locally sourced materials. This is to encourage local ingenuity and to reduce cost of production comparable to already made custom-imported ones. It is designed to be simple, handy and readily available to be used by anyone in case of malfunctioning and for easy relocation. Though, the main limitation of the system fabricated is the long time it uses to achieve cooling, the performance of the machine generally is very efficient as its calculated coefficient of performance ( C.O.P is 1.21, which compared favourably well with the literature value of 1.00-2.00. Also, the total cost including an over-head of 30% of the machine was estimated at forty-one thousand, two hundred and fifty-nine (N41,259.40 naira, forty kobo only based on current price structure compared to an equivalent custom-made-imported type estimated at between sixty to seventy thousand (N60,000.00 to N70,000.00 naira. Hence, the machine is affordable to all, and is highly recommended for local entrepreneurs for mass production because of its cost effectiveness, simplicity and availability of spare parts.
Analysis of engineering cycles power, refrigerating and gas liquefaction plant
Haywood, R W
1991-01-01
Extensively revised, updated and expanded, the fourth edition of this popular text provides a rigorous analytical treatment of modern energy conversion plant. Notable for both its theoretical and practical treatment of conventional and nuclear power plant, and its studies of refrigerating and gas-liquefaction plant. This fourth edition now includes material on topics of increasing concern in the fields of energy 'saving' and reduction of environmental pollution. This increased coverage deals specifically with the following areas: CHP (cogeneration) plant, studies of both gas and coal burning p
The performance of the transcritical CO2 refrigeration system requires further improvement in order to save energy. In this paper, the effect of the internal heat exchanger (IHE) on the performance of the ejector expansion transcritical CO2 refrigeration system is analyzed theoretically based on the first law of thermodynamics. The possible parameters affecting system efficiency are investigated. The variation of ejector entrainment ratio, pressure recovery, ejector efficiency and the coefficient of performance (COP) is obtained for the ejector expansion transcritical CO2 refrigeration cycles with and without IHE. It is found that the addition of IHE in the CO2 ejector refrigeration cycle increases the ejector entrainment ratio and the ejector efficiency, and decreases pressure recovery under the same gas cooler pressures. Unlike in a conventional throttle valve cycle, an IHE addition does not always improve the system performance in the ejector expansion cycle. Whether the energy efficiency of the ejector cycle by IHE can be improved depends on the isentropic efficiency level of the ejector. The utilization of IHE is only applicable in the cases of lower ejector isentropic efficiencies or higher gas cooler exit/evaporator temperatures for the ejector expansion system from the view of energy efficiency. - Highlights: ► The effect of internal heat exchanger on the performance of ejector transcritical CO2 refrigeration system is analyzed. ► The variation of entrainment ratio, pressure recovery, ejector efficiency and coefficient of performance is obtained. ► An internal heat exchanger does not always improve the system performance in the ejector expansion cycle. ► Whether the ejector cycle performance by internal heat exchanger can be improved depends on the ejector isentropic efficiency.
Plura, S.; Baumeister, D.; Koeberle, T.; Radspieler, M.; Schweigler, C. [Bayerisches Zentrum fuer Angewandte Energieforschung e.V. (ZAE Bayern), Garching (Germany)
2007-07-01
A new system concept for higher efficiency of cogeneration systems is developed in which a cogeneration unit is combined with a two-stage absorption refrigerator, and the waste heat of the cogeneration unit is directly passed on into the regenerator of the absorption refrigerator. The higher temperature level of the waste heat makes it possible to use a two-stage absorption cycle for higher energy efficiency. For simultaneous utilisation of low-temperature heat, the two-stage cycle is combined with a one-stage cycle for additional heat supply at a lower temperature level so that the exhaust of a typical cogeneration unit will be cooled to about 120 degC. At the same time, further waste heat of the cogeneration unit will be transferred to the heat pump via a hot water circuit. This concept with a combined single-stage and two-stage absorption circuit is referred to as a double-effect/single-effect circuit. The new system is used for energy supply in a spa, where the two-stage absorption refrigerator cools the water used for swimming pool cleaning with a refrigerating capacity of 350 kW and provides low-temperature heat for swimming pool heating with a capacity of 700 kW. (orig.)
Performance evaluation of combined ejector LiBr/H2O absorption cooling cycle
Hasan Sh. Majdi
2016-03-01
Full Text Available The objective of this work is to develop a computer simulation program to evaluate the performance of solar-assited combined ejector absorption (single-effect cooling system using LiBr/H2O as a working fluid and operating under steady-state conditions. The ejector possess no moving parts and is simple and reliable, which makes it attractive for combination with single-stage absorption cycle for further improvement to the system's performance. In this research, improvement to the system is achieved by utilizing the potential kinetic energy of the ejector to enhance refrigeration efficiency. The effects of the entrainment ratio of the ejector, operating temperature, on the thermal loads, and system performance have been investigated. The results showed that the evaporator and condenser loads, post-addition of the ejector, is found to be permanently higher than that in the basic cycle, which indicates a significant enhancement of the proposed cycle and the cooling capacity of the system increasing with the increase in evaporator temperature and entrainment ratio. The COP of the modified cycle is improved by up to 60 % compared with that of the basic cycle at the given condition. This process stabilizes the refrigeration system, enhanced its function, and enabled the system to work under higher condenser temperatures.
Potgieter, Marthinus Christiaan
2013-01-01
Several steps are followed in order to evaluate the cycle as the title suggests. The diffusion absorption refrigerator (DAR) cycle performance is evaluated when using helium or hydrogen as auxiliary gas. A slight increase in COP is found when using helium, but it is not sufficient to justify the cost. A secondary simulation of an alternate dual-pressure cycle using a pump is done as feasibility comparison with the same parameters as the diffusion cycle. It was found that the second cycle is n...
Although the last decade witnessed dramatic progress in refrigerator efficiencies, inefficient, outdated refrigerators are still in operation, sometimes consuming more than twice as much electricity per year compared with modern, efficient models. Replacing old refrigerators before their designed lifetime could be a useful policy to conserve electric energy and greenhouse gas emissions. However, from a life cycle perspective, product replacement decisions also induce additional economic and environmental burdens associated with disposal of old models and production of new models. This paper discusses optimal lifetimes of mid-sized refrigerator models in the US, using a life cycle optimization model based on dynamic programming. Model runs were conducted to find optimal lifetimes that minimize energy, global warming potential (GWP), and cost objectives over a time horizon between 1985 and 2020. The baseline results show that depending on model years, optimal lifetimes range 2-7 years for the energy objective, and 2-11 years for the GWP objective. On the other hand, an 18-year of lifetime minimizes the economic cost incurred during the time horizon. Model runs with a time horizon between 2004 and 2020 show that current owners should replace refrigerators that consume more than 1000 kWh/year of electricity (typical mid-sized 1994 models and older) as an efficient strategy from both cost and energy perspectives
Xu, Zhichao; Guo, Juncheng; Lin, Guoxing; Chen, Jincan
2016-07-01
On the basis of the Langevin theory of classical statistical mechanics, the magnetization, entropy, and iso-field heat capacity of ferromagnetic materials are analyzed and their mathematical expressions are derived. An irreversible regenerative Ericsson refrigeration cycle by using a ferromagnetic material as the working substance is established, in which finite heat capacity rates of low and high temperature reservoirs, non-perfect regenerative heat of the refrigeration cycle, additional regenerative heat loss, etc. are taken into account. Based on the regenerative refrigeration cycle model, a thermoeconomic function is introduced as one objective function and optimized with respect to the temperatures of the working substance in the two iso-thermal processes. By means of numerical calculation, the effects of the effective factor of the heat exchangers in high/low temperature reservoir sides, efficiency of the regenerator, heat capacity rate of the low temperature reservoir, and applied magnetic field on the optimal thermoeconomic function as well as the corresponding cooling rate and coefficient of performance are revealed. The results obtained in this paper can provide some theoretical guidance for the optimal design of actual regenerative magnetic refrigerator cycle.
An Automated Ac Susceptibility Set up Fabricated Using a Closed-Cycle Helium Refrigerator
Kundu, S
2011-01-01
We have described here the design and operation of an automated ac susceptibility set up using a closed cycle helium refrigerator. This set up is useful for measuring linear and nonlinear magnetic susceptibilities of various magnetic materials. The working temperature range is 2 K to 300 K. The overall sensitivity of the set up is found to be 10-3 emu.
SUPERCONDUCTING MAGNET FOR 60 TONNE/HOUR MINERAL SEPARATOR WITH CLOSED CYCLE 4 KELVIN REFRIGERATION
Good, J.; White, K.
1984-01-01
Cryogenic Consultants Limited has constructed a superconducting magnet system for magnetic separation, with a three metre long dipole magnet cooled by a closed-cycle refrigerator. This paper considers the design and construction of the magnet system in relation to a theoretical expression for processing capacity.
Simarpreet Singh; Nilesh Purohit; M.S. Dasgupta
2016-01-01
This paper presents a comparative study of performance of six prominent modifications on the basic trans-critical CO2 refrigeration system to investigate their suitability to high ambient temperature application (35–55 °C). To explore the application in chiller, domestic refrigeration and air cooling the evaporator temperature chosen are −10 °C, 0 °C and 10 °C respectively. In general the cycle modifications have a positive effect on the overall COP of the system. However, to comprehend pract...
The optimal performance of a quantum refrigeration cycle working with harmonic oscillators
The cycle model of a quantum refrigeration cycle working with many non-interacting harmonic oscillators and consisting of two isothermal and two constant-frequency processes is established. Based on the quantum master equation and semi-group approach, the general performance of the cycle is investigated. Expressions for some important performance parameters, such as the coefficient of performance, cooling rate, power input, and rate of the entropy production, are derived. Several interesting cases are discussed and, especially, the optimal performance of the cycle at high temperatures is discussed in detail. Some important characteristic curves of the cycle, such as the cooling rate versus coefficient of performance curves, the power input versus coefficient of performance curves, the cooling rate versus power input curves, and so on, are presented. The maximum cooling rate and the corresponding coefficient of performance are calculated. Other optimal performances are also analysed. The results obtained here are compared with those of an Ericsson or Stirling refrigeration cycle using an ideal gas as the working substance. Finally, the optimal performance of a harmonic quantum Carnot refrigeration cycle at high temperatures is derived easily
Applications of closed cycle refrigerator for some physical experiments
Full text: It is known that CCRs give a good possibility to conduct various experiments in a wide range of temperatures from 2.5 K up to 500 deg. C. These do not need nor liquid helium, nor liquid nitrogen and create a quick, precise and stable conditions for researchers. Some applications of such CCRs from Lake Shore corporation will be consider ed in this communication. The first one is a measurement of temperature dependence of the viscosity by drop-falling method of some special liquids which can be used in ultra cold neutron investigations. The second one is an experiment for receiving the perfect solid crystals of methane which are need in producing ultra cold neutrons in medium power reactors. For these experiments some special arrangements were installed on the cold head of refrigerator with long vertical or small round windows on the screens through which the processes studied were visually observed and measured. (authors)
Thermodynamic Analysis of an Absorption/Compression Refrigeration System Using Geothermal Energy
L. Kairouani
2005-01-01
Full Text Available This article presents the potential use and exploration of geothermal energy for cooling applications using a combined absorption/compression system. The considered system uses R134a for the compression part and the cool water-ammonia for the absorption part of the installation. The geothermal temperature source is in the range 343-349K, the condensation temperature is 308 K, and in order to produce ice, the R134a evaporation temperature is 263 K. The COP is about 5.4. Therefore, based on the typical geothermal energy sources in Tunisia which present a refrigeration potential power of 9.1 MW, the quantity of ice that could be produced is about 82 tons per hour. The greenhouse gas emissions should thus be reduced by about 5884 tons of CO2 per year, which represents (59%.
Absorption refrigeration using waste heat; Refrigeracion por absorcion utilizando calor de desecho
Heard, Christopher; Ayala, Ramon; Best, Roberto [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1994-07-01
In this article a detailed analysis is made of the absorption refrigeration system that uses waste heat and because of being of low temperature, can make the processes more efficient being at the same time an important factor in the country`s energy resources saving, since the system permits to increase the availability of electricity and fuel`s energy. The Instituto de Investigaciones Electricas (IIE) and the Universidad Nacional Autonoma de Mexico (UNAM) absorption refrigeration experience is described and the economic aspects related with this system are analyzed. [Espanol] En este articulo se presenta un analisis detallado del sistema de refrigeracion por absorcion que utiliza calor de desecho y que, siendo de baja temperatura, puede hacer mas eficientes los procesos y ser a la vez un factor importante en el ahorro de los recursos energeticos del pais, pues el sistema permite aumentar la disponibilidad energetica de electricidad y combustibles. Se describe la experiencia del Instituto de Investigaciones Electricas (IIE) en refrigeracion por absorcion y la de la Universidad Nacional Autonoma de Mexico (UNAM), y se analizan los aspectos economicos relacionados con este sistema.
Solution procedure and performance evaluation for a water–LiBr absorption refrigeration machine
The water–lithium bromide absorption cooling machine was investigated theoretically in this paper. A detailed solution procedure was proposed and validated. A parametric study was conducted over the entire admissible ranges of the desorber, condenser, absorber and evaporator temperatures. The performance of the machine was evaluated based on the circulation ratio which is a measure of the system size and cost, the first law coefficient of performance and the second law exergy efficiency. The circulation ratio and the coefficient of performance were seen to improve as the temperature of the heat source increased, while the second law performance deteriorated. The same qualitative responses were obtained when the temperature of the refrigerated environment was increased. On the other hand, simultaneously raising the condenser and absorber temperatures was seen to result in a severe deterioration of both the circulation ratio and first law coefficient of performance, while the second law performance indicator improved significantly. The influence of the difference between the condenser and absorber exit temperatures, as well as that of the internal recovery heat exchanger on the different performance indicators was also calculated and discussed. - Highlights: • Analysis of a water–LiBr absorption machine, including detailed solution procedure. • Performance assessed using first and second law considerations, as well as flow ratio. • Effects of heat source and refrigerated environment temperatures on the performance. • Effects of the difference between condenser and absorber temperatures. • Effects of internal heat exchanger efficiency on overall cooling machine performance
Sun Lunan
2016-01-01
Full Text Available This article regard the solar lithium-bromide absorption refrigerating air conditioning system as the research object, and it was conducting adequate research of the working principle of lithium bromide absorption refrigerating machine, also it was analyzing the requirements of control system about solar energy air conditioning. Then the solar energy air conditioning control system was designed based on PLC, this system was given priority to field bus control system, and the remote monitoring is complementary, which was combining the network remote monitoring technology. So that it realized the automatic control and intelligent control of new lithium bromide absorption refrigerating air conditioning system with solar energy, also, it ensured the control system can automatically detect and adjust when the external conditions was random changing, to make air conditioning work effectively and steadily, ultimately ,it has great research significance to research the air conditioning control system with solar energy.
Definition of a reference dataset for life cycle consideration of refrigeration systems
Mas Méndez, Roger
2013-01-01
In recent decades society has increased its concern about environmental protection, in order to achieve the goal of sustainable development. However, there are several economic sectors like refrigeration industry, which still are cause for a wide number of environmental impacts and, therefore, require improvement in their processes. The purpose of this final work is to establish the current state of the art regarding Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), particularized to ...
Most modern refrigerators incorporate heat transfer between the refrigerant in a capillary tube and the refrigerant in a suction line. This heat transfer is achieved by a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger and is supposed to improve the performance of the small vapor compression refrigeration cycle by removing some enthalpy of the refrigerant at the evaporator entrance. To investigate the effects of this heat transfer on the refrigeration cycle, a computer program was developed based on conservation equations of mass, momentum, and energy. The non-adiabatic capillary tube model is based on a homogeneous two-phase flow model. The simulation results show that both the location and length of the heat exchange section influence the coefficient of performance (COP) as well as the cooling capacity. It is noteworthy that the influence was not monotonic; that is, the performance may be deteriorated under certain conditions
Zhenying Zhang
2015-04-01
Full Text Available Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI, double-compression external intercooler cycle with an expander (DCEIE, double-compression flash intercooler cycle (DCFI, double-compression flash intercooler cycle with an expander (DCFIE. The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external intercooler cycle. The use of an expander in the DCEI cycle leads to a decrease of the optimum gas cooler pressure and little variation of the optimum intermediate pressure. However, the replacement of the throttle valve with an expander in the DCFI cycle results in little variation of the optimal gas cooler pressure and an increase of the optimum intermediate pressure. The DCFI cycle outperforms the DCEI cycle under all the chosen operating conditions. The DCEIE cycle outperforms the DCFIE cycle when the evaporating temperature exceeds 0 °C or the gas cooler outlet temperature surpasses 35 °C. When the gas cooler exit temperature varies from 32 °C to 48 °C, the DCEI cycle, DCEIE cycle, DCFI cycle and DCFIE cycle yield averaged 4.6%, 29.2%, 12.9% and 22.3% COP improvement, respectively, over the basic cycle.
Application of exergy method to an irreversible inter-cooled refrigeration cycle
Chen, C-K. [National Cheng-Kung University, Tainan (Taiwan). Department of Mechanical Engineering; Su, Y-F. [Far East College, Tainan (Taiwan). Department of Automation and Control Engineering
2005-12-15
The exergy method, based on the maximum exergetic efficiency criterion, has been applied to an irreversible inter-cooled refrigeration cycle. The exergetic efficiency defined as the ratio of the rate of exergy output to the rate of exergy input is taken as the objective function to be maximized. Multi-irreversibilities include finite-rate heat transfer, internal dissipation of the working fluid, and heat leaks between heat reservoirs. The maximum exergetic efficiency can be determined analytically by introducing the internal irreversibility parameter, which represents the degree of internal irreversibility. The corresponding performances of the irreversible refrigeration system are obtained simultaneously. The results show that the exergy method can be used as an effective criterion in designing an irreversible inter-cooled refrigeration system. (author)
Farshi, L.G.; Mahmoudi, S.M.S. [Tabriz Univ., Tabriz (Iran, Islamic Republic of). Faculty of Mechanical Engineering; Mosafa, A.H. [Islamic Azad Univ., Bonab (Iran, Islamic Republic of)
2008-07-01
A study was conducted in which the effect of inlet air cooling on the performance of a gas turbine was investigated. Compared to steam turbines, gas turbines have lower capital cost, are compact in size, and offer better environmental performance with fast starts and loading. They require less manpower for operating and do not need water sources. However, they have lower efficiency than steam turbines and have a strong influence on climatic conditions. In addition, thermal energy in the form of exhaust gases is delivered to, and wasted in, the environment. In order to increase the power and efficiency of gas turbine plants, this low grade thermal energy can be put to beneficial use in a heat exchanger of a regenerative gas turbine (RGT) or in the generator of an absorption refrigeration cycle (ARC). This paper focused on ways to increase the performance of gas turbine plants by using an ARC for inlet air cooling. The authors studied the feasibility of installing an ARC at the gas turbine inlet. The work showed that the net work and the efficiency will increase by 6-10 per cent and 1-5 per cent respectively for every 10 degrees C decrease of inlet temperature. Since the coefficient of performance (COP) of ARC is low, the thermal energy of exhaust gases cannot supply all the needed thermal energy for the refrigeration cycle. The results showed that when an ejector is included in the refrigeration cycle, the need for external energy source required for refrigeration cycle is reduced. 22 refs., 8 tabs., 18 figs.
Experimental results of a direct air-cooled ammonia–lithium nitrate absorption refrigeration system
Absorption thermal cooling systems driven by renewable energy are a viable option in order to reduce fossil fuel consumption and the associated emissions. This work shows the results of an air cooled absorption cooling prototype working with an ammonia–lithium nitrate mixture at high ambient temperatures. An absorption refrigeration system was designed and built. The prototype is a one stage ammonia–lithium nitrate air cooled chiller. The experimental system was instrumented to evaluate each component. This paper shows the operation conditions in the experimental unit as well as some of the heat loads encountered at different operating conditions. The system was operated successfully at ambient temperatures in the range of 25–35 °C. A series of test showed that even at ambient temperatures it can be operated at evaporator temperatures below 10 °C producing chilled water for air conditioning applications such as radiative cooling panels. The system proved to stabilize very quickly and no risk of crystallization was encountered so the first results are promising in order to continue with the development of a more advanced prototype. - Highlights: •Experimental results of a direct air-cooled ammonia–lithium nitrate system. •The prototype is a one stage ammonia–lithium nitrate air cooled chiller. •The absorption system was operated successfully at ambient temperatures. •Cooling loads of 4.5 kW were reached in the chilled water side
A Comparative Cycle and Refrigerant Simulation Procedure Applied on Air-Water Heat Pumps
Mader, Gunda; Palm, Björn; Elmegaard, Brian
2012-01-01
small capacity heat pump applications today. Many of the applicable refrigerants also reach their technical limits regarding low vapor pressure for very low source temperatures and high discharge temperatures for high sink temperatures. These issues are especially manifest for air-water heat pumps. Many...... alternative cycle setups and refrigerants are known to improve the energy efficiency of a vapor compression cycle and reduce discharge temperatures. However not all of them are feasible for small capacity heat pumps from a cost and complexity point of view. This paper presents a novel numerical approach......A vapor compression heat pump absorbs heat from the environment at a low temperature level and rejects heat at a high temperature level. The bigger the difference between the two temperature levels the more challenging is it to gain high energy efficiency with a basic cycle layout as found in most...
Optimum criteria of an irreversible quantum Brayton refrigeration cycle with an ideal Bose gas
An irreversible cycle model of the quantum Brayton refrigeration cycle is established, in which finite-time processes and irreversibility in the two adiabatic processes are taken into account. On the basis of the thermodynamic properties of an ideal Bose gas, by using the optimal control-theory, the mathematical expressions for several important performance parameters, such as the coefficient of performance, power input and cooling load, are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of a Bose-Brayton refrigeration cycle are obtained and analyzed. Furthermore, some optimal operating regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail
Brown, T. D.; Karaman, I.; Shamberger, P. J.
2016-07-01
Magnetic refrigeration technology based on the giant magnetocaloric effect in solid-state refrigerants is known qualitatively to be limited by dissipative mechanisms accompanying hysteresis in the magneto-structural solid–solid phase transition. In this paper, we quantitatively explore the dependence of cycle performance metrics (cooling power, temperature span, work input, and fractional Carnot efficiency) on hysteresis properties (thermal hysteresis, one-way transition width) of the magneto-structural phase transition in a Ni45Co5Mn36.6In13.4 alloy system. We investigate a variety of Ericsson-type magnetic refrigeration cycles, using a Preisach-based non-equilibrium thermodynamic framework to model the evolution of the alloy's magnetic and thermal properties. Performance metrics are found to depend strongly on hysteresis parameters, regardless of the cycle chosen. However, for a given hysteresis parameter set, the material's transformation temperatures determine a unique cycle that maximizes efficiency. For the model system used undergoing Ericsson cycles with 5 and 1.5 {{T}} maximum field constraint, fractional Carnot efficiencies in excess of 0.9 require thermal hysteresis below 1.5 {{K}} and 0.5 {{K}}, respectively. We conclude briefly with some general materials considerations for mitigating these hysteresis inefficiencies through microstructure design and other materials processing strategies.
Miquel Nogués
2005-12-01
Full Text Available
Absorption cycles are an alternative to compression cycles in cooling and refrigeration applications. Our analysis of an absorption cycle is based on the exergy and the structural analysis. Once the exergy analysis has been achieved, the coefficients of structural bonds (CSBs of the main heat and mass exchangers can be determined by a structural analysis. The CSBs show how the modification of the irreversibility of one component, by means of a variation of its efficiency, affects the whole cycle. It will be wise to put much of the design effort in improving the efficiency of a component, knowing that a slight decrease of the irreversibility of that component, thanks to a higher efficiency, results in an important improvement in the total irreversibility of the cycle. This methodology is applied to a single effect ammonia-water absorption cooling cycle. We also study how the selection of efficiency parameters affects the results comparing CSBs of heat exchangers obtained from the minimum temperature differences or the UA-values.
Results show that the UA is a more suitable parameter than the minimum temperature difference. Concerning the CSB values, we obtain very high values for the refrigerant heat exchanger. Values above one are also observed for the absorber, condenser and generator.
Lower values are found for the generator and the solution heat exchanger. A more detailed analysis should investigate the dependence of the CSB values on the range of efficiencies. As a further step, these results could be used in the thermoeconomic analysis and economical optimization.
Modeling and Control of a Double-effect Absorption Refrigerating Machine
Hihara, Eiji; Yamamoto, Yuuji; Saito, Takamoto; Nagaoka, Yoshikazu; Nishiyama, Noriyuki
For the purpose of impoving the response to cooling load variations and the part load characteristics, the optimal operation of a double-effect absorption refrigerating machine was investigated. The test machine was designed to be able to control energy input and weak solution flow rate continuously. It is composed of a gas-fired high-temperature generator, a separator, a low-temperature generator, an absorber, a condenser, an evaporator, and high- and low-temperature heat exchangers. The working fluid is Lithium Bromide and water solution. The standard output is 80 kW. Based on the experimental data, a simulation model of the static characteristics was developed. The experiments and simulation analysis indicate that there is an optimal weak solution flow rate which maximizes the coefficient of performance under any given cooling load condition. The optimal condition is closely related to the refrigerant steam flow rate flowing from the separator to the high temperature heat exchanger with the medium solution. The heat transfer performance of heat exchangers in the components influences the COP. The change in the overall heat transfer coefficient of absorber has much effect on the COP compared to other components.
Highlights: • The feasibility of performance of four-heat-source irreversible refrigerators is investigated. • The latter is achieved using NSGA algorithm and thermodynamic analysis. • Three well known decision makers are accomplished to indicate optimum outputs obtained with optimization process. - Abstract: This paper presents a developed ecological function for absorption refrigerators with four-temperature-level. Moreover, aforementioned absorption refrigerator is optimized by implementing ecological function. With the aim of the first and second laws of thermodynamics, an equivalent system is initially determined. To reach the addressed goal of this research, three objective functions that the coefficient of performance (COP), the ecological function (E) and thermoeconomic criterion (F) have been involved in optimization process simultaneously. Three objective functions are maximized at the same time. Developed multi objective evolutionary approaches (MOEAs) on the basis of NSGA-II method is implemented throughout this work
Improving Energy Efficiency of a Refrigeration System with a Rankine Cycle and an Expander
Subiantoro, Alison
2015-01-01
A method to increase energy efficiency of a vapor compression refrigeration system by using a Rankine cycle and an expander is studied. The systems studied include the R134a and the transcritical CO2 cycles with a 5 kW capacity. The working fluids of the Rankine cycle are R134a, propane and R123. The available heat input power is 1-5 kW. The results show that in the R134a and CO2 systems, 18-40% and 30-67% improvements of Coefficient of Performance (COP), respectively, can be achieved. The me...
Coherence-assisted single-shot cooling by quantum absorption refrigerators
Mitchison, Mark T.; Woods, Mischa P.; Prior, Javier; Huber, Marcus
2015-11-01
The extension of thermodynamics into the quantum regime has received much attention in recent years. A primary objective of current research is to find thermodynamic tasks which can be enhanced by quantum mechanical effects. With this goal in mind, we explore the finite-time dynamics of absorption refrigerators composed of three quantum bits (qubits). The aim of this finite-time cooling is to reach low temperatures as fast as possible and subsequently extract the cold particle to exploit it for information processing purposes. We show that the coherent oscillations inherent to quantum dynamics can be harnessed to reach temperatures that are colder than the steady state in orders of magnitude less time, thereby providing a fast source of low-entropy qubits. This effect demonstrates that quantum thermal machines can surpass classical ones, reminiscent of quantum advantages in other fields, and is applicable to a broad range of technologically important scenarios.
Nat Suvarnakuta
2014-03-01
Full Text Available This paper presents the COP prediction of an ejector refrigeration cycle combined with a vapour compression cycle for automotive air conditioning. Using computational fluid dynamics (CFD technique, the performance of an ejector was analyzed in term of the entrainment ratio (Rm and critical back pressure (CBP. The results from this study were compared with a previous study of combined ejector refrigeration system for automotive air conditioning application [1] which the entrainment ratio (Rm were predicted from one-dimensional (1-D equation. The performance of an ejector (Rm and CBP from CFD and onedimensional method were analyzed and used as database for a mathematical modeling. In order to predict the COP of the combined system, a set of mathematical equations was developed using EES. The operating conditions are chosen accordingly as, intercooler temperature between 15 ๐ C and 25 ๐ C, condenser temperature equal to 35 ๐ C and evaporator temperature equal to 5 ๐ C. However, when generator temperatures are 80 ๐ C, 85 ๐ C and 90 ๐ C, the results showed average relative errors of the COP of an ejector refrigeration cycle (COPej, between CFD and 1-D are 44.64%, 50.47% and 59.68% respectively, and between CFD and 1-D NEW are 1.54%, 0.08% and 6.49% respectively.
Performance of V-type Stirling-cycle refrigerator for different working fluids
Tekin, Yusuf; Ataer, Omer Ercan [Erciyes University, Engineering Faculty, Mechanical Engineering Department, Melikgazi, 38 039 Kayseri (Turkey)
2010-01-15
The thermodynamic analysis of a V-type Stirling-cycle Refrigerator (VSR) is performed for air, hydrogen and helium as the working fluid and the performance of the VSR is investigated. The V-type Stirling-cycle refrigerator consists of expansion and compression spaces, cooler, heater and regenerator, and it is assumed that the control volumes are subjected to a periodic mass flow. The basic equations of the VSR are derived for per unit crank angle, so time does not appear in the equations. A computer program is prepared in FORTRAN, and the basic equations are solved iteratively. The mass, temperature and density of working fluid in each control volume are calculated for different charge pressures, engine speeds, and for fixed heater and cooler surface temperatures. The work, instantaneous pressure and the COP of the VSR are calculated. The results are obtained for different working fluids, and given by diagrams. (author)
Ayala Delgado, R.; Heard, C. L. [Instituto de Investigaciones Electricas, Cuernavaca, (Mexico); Pardubicki, J. [LAJ International, Mexico D. F. (Mexico)
1995-12-31
The absorption refrigeration ammonia-lithium nitrate offers great advantages compared with the mechanical compression refrigeration with ammonia as well as with the absorption ammonia-water refrigeration. With heat temperatures of 1000 to 1400 Celsius degrees, for instance low pressure steam the generation of cold at low temperatures (-100 to -200 Celsius degrees) is possible. The system has less components and is much less expensive than the ammonia-water equipment with a price very similar to the ammonia mechanical compression equipment. The equipment consists of five main heat exchangers and a solution pump, resulting in a high reliability of its operation, requiring a minimum maintenance. The operation cost depends directly of the cost of the energy source. In case of using residual heat the operation cost is only the maintenance cost. Nowadays the cost of the electric energy is below the production cost, which can be a short term situation. In time terms of the comparable useful life time of an absorption refrigeration system (in excess of 20 years), it is reasonable to think that the operation costs will be less than the operation costs of an equipment with mechanical compression. To this day it is available a demonstration unit to exhibit the system in industrial plants with different energy sources. [Espanol] La refrigeracion por absorcion amoniaco/nitrato de litio ofrece grandes ventajas comparada tanto con la refrigeracion por compresion mecanica con amoniaco como con la refrigeracion por absorcion amoniaco/agua. Este sistema es mas eficiente y sencillo que el sistema de amoniaco/agua. Con calor de temperatura (100 a 140 grados centigrados por ejemplo vapor de baja presion, se permite la generacion de frio a temperaturas bajas (-10 a -20 grados centigrados). El sistema tiene menos componentes y es mucho mas barato que equipo de amoniaco/agua con un precio muy similar a sistemas por compresion mecanica de amoniaco. El sistema consiste en cinco
Kausik Sadhukhan
2012-06-01
Full Text Available The thermodynamic analysis and optimization of combined power and refrigeration cycle as well as the improved vapour absorption refrigeration system necessitate the development of computer based thermodynamic properties of ammonia-water mixture. In this work, a computer code has been developed for the thermodynamic properties of ammonia water mixture for different pressures, temperatures and ammonia mass fraction concentration. This has been achieved by using some exact thermodynamic relations and some co-relations available in the literature. The computed results have been compared with the published experimental data and the agreement is found to be of good accuracy. The errors in the computed results for different thermodynamic properties are slightly more at comparatively high pressure and temperature. The maximum error is found to be with saturated liquid mixture entropy and its value is also less then 3.8% even at a high pressure of 34.47 bar.
Proﬁt rate performance optimization for a generalized irreversible combined refrigeration cycle
Kang Ma; Lingen Chen; Fengrui Sun
2009-10-01
Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalized irreversible combined refrigeration cycle model with ﬁnite-rate heat transfer, heat leakage and internal irreversibility is presented in this paper. The operation of the generalized irreversible combined refrigeration cycle is viewed as a production process with exergy as its output. The performance optimization of the cycle is performed by taking proﬁt as the objective. The optimal proﬁt rate, optimal COP (coefﬁcient of performance), as well as the relation between the optimal proﬁt rate and COP of the cycle are derived. The focus of this paper is to obtain the compromise optimization between economics (proﬁt rate) and the energy utilization factor (COP) for the cycle, by searching the optimum COP at maximum proﬁt rate, which is termed as the ﬁnite time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price ratio, on the proﬁt rate performance of the cycle are analysed by detailed numerical examples.
Bihong Lin; Yingru Zhao; Jincan Chen
2008-05-01
An irreversible model of an Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas is established, which is composed of two isothermal and two isobaric processes. The influence of both the quantum degeneracy and the finite-rate heat transfer between the working fluid and the heat reservoirs on the performance of the cycle is investigated, based on the theory of statistical mechanics and thermodynamic properties of an ideal Fermi gas. The inherent regeneration losses of the cycle are analyzed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Especially, the optimal performance of the cycle in the strong and weak gas degeneracy cases and the high temperature limit is discussed in detail. The analytic expressions of some optimized parameters are derived. Some optimum criteria are given. The distinctions and connections between the Ericsson refrigeration cycles working with the Fermi and classical gases are revealed.
First Law Analysis of a Two-stage Ejector-vapor Compression Refrigeration Cycle working with R404A
Feiza Memet
2011-10-01
Full Text Available The traditional two-stage vapor compression refrigeration cycle might be replaced by a two-stage ejector-vapor compression refrigeration cycle if it is aimed the decrease of irreversibility during expansion. In this respect, the expansion valve is changed with an ejector. The performance improvement is searched in the case of choosing R404A as a refrigerant. Using the ejector as an expansion device ensures a higher value for COP compared to the traditional case. On the basis of the ejector approach it possible to identify the highest COP value for a given condensation temperature, when the evaporation temperature varies.
Performance optimization of quantum Brayton refrigeration cycle working with spin systems
The new model of a quantum refrigeration cycle composed of two adiabatic and two isomagnetic field processes is established. The working substance in the cycle consists of many non-interacting spin-1/2 systems. The performance of the cycle is investigated, based on the quantum master equation and semi-group approach. The general expressions of several important performance parameters, such as the coefficient of performance, cooling rate and power input, are given. It is found that the coefficient of performance of this cycle is a close analogue of the classical Carnot-cycle. Some performance characteristic curves relating the cooling rate, the coefficient of performance and power input are plotted. Further, for high temperatures, the optimal relations between the cooling rate and the coefficient of performance are analyzed in detail
The optimal performance of a quantum refrigeration cycle working with harmonic oscillators
Lin Bi Hong; Hua Ben
2003-01-01
The cycle model of a quantum refrigeration cycle working with many non-interacting harmonic oscillators and consisting of two isothermal and two constant-frequency processes is established. Based on the quantum master equation and semi-group approach, the general performance of the cycle is investigated. Expressions for some important performance parameters, such as the coefficient of performance, cooling rate, power input, and rate of the entropy production, are derived. Several interesting cases are discussed and, especially, the optimal performance of the cycle at high temperatures is discussed in detail. Some important characteristic curves of the cycle, such as the cooling rate versus coefficient of performance curves, the power input versus coefficient of performance curves, the cooling rate versus power input curves, and so on, are presented. The maximum cooling rate and the corresponding coefficient of performance are calculated. Other optimal performances are also analysed. The results obtained here ...
A. B. Kasaeian
2013-04-01
Full Text Available In this study, a new model of a solar combined ejector-vapor compression refrigeration system has been considered. The system is equipped with an internal heat exchanger to enhance the performance of the cycle. The effects of working fluid and operating conditions on the system performance including COP, entrainment ratio (ω, compression ratio (rp and exergy efficiency were investigated. Some working fluids suggested are: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e and R1234ze(z. The results show that R114 and R1234ze(e yield the highest COP and exergy efficiency followed by R123, R245fa, R365mfc, R141b, R152a and R600a. It is noticed that the COP value of the new solar ejector-vapor compression refrigeration cycle is higher than that of the conventional ejector cycle with R1234ze(e for all operating conditions. This paper also demonstrates that R1234ze(e will be a suitable refrigerant in the solar combined ejector-vapor compression refrigeration system, due to its environmental friendly properties and better performance. ABSTRAK: Kajian ini menganalisa model baru sistem penyejukan mampatan gabungan ejektor-wap solar.Sistem ini dilengkapi dengan penukar haba dalaman untuk meningkatkan prestasi kitaran.Kesan bendalir bekerja dan keadaan operasi pada prestasi sistem termasuk COP, nisbah pemerangkapan (ω, nisbah mampatan (rp dan kecekapan eksergi telah disiasat.Beberapa bendalir bekerja yang dicadangkan adalah: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e dan R1234ze(z.Hasil kajian menunjukkan R114 dan R1234ze(e menghasilkan COP dan kecekapan eksergi tertinggi diikuti oleh R123, R245fa, R365mfc, R141b, R152a dan R600a.Didapati nilai COP kitaran penyejukan mampatan bagi ejektor-wap solar baru adalah lebih tinggi daripada kitaran ejektor konvensional dengan R1234ze(e bagi semua keadaan operasi.Kertas kerja ini juga menunjukkan bahawa R1234ze(e boleh menjadi penyejuk yang sesuai dalam sistem penyejukan mampatan gabungan ejektor
An analysis of the performance of an ejector refrigeration cycle working with R134a
Memet, F.; Preda, A.
2015-11-01
In the context of recent developments in the field of energy, the aspect related to energy consumption is of great importance for specialists. Many industries rely on refrigeration technologies, a great challenge being expressed by attempts in energy savings in this sector. In this respect, efforts oriented towards efficient industrial refrigeration systems have revealed the necessity of a proper design. The most commonly used method of cooling is based on vapor compression cycles. Compared to vapor compression refrigeration systems, an ejector refrigeration system shows an inferior performance, indicated by the Coefficient of Performance of the cycle, but it is more attractive from energy saving point of view. In this respect, the present study deals with a theoretically analysis of an Ejector Refrigeration System, started with the presentation of the typical ejector design. It is stated that ejector refrigeration is a thermally driven system which requires low grade thermal energy for its working. After a short description of the analyzed system, are given equations for thermal loads and Coefficient of Performance calculation, on First Law basis. The working fluid considered in this research is Freon R134a. The developed study is focused on the effect of generating temperature variation on the Coefficient of Performance (COP) and on the work input to the pump when the cooling effect, the condensation temperature, the evaporation temperature and the reference state temperature are kept constant. Are obtained results in the following conditions: the condensation temperature is tc = 33°C, the evaporation temperature is te = 3°C, the reference state temperature is to = 23°C. The generating temperature varies in the range 82 ÷ 92°C and the cooling effect is 1 kW. Also, are known the isentropic efficiencies of the ejector, which are 0.90, and the isentropic efficiency of the pump, which is 0.75. Calculation will reveal that the Coefficient of Performance is
Analysis of Decentralized Control for Absorption Cycle Heat Pumps
Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard; Andersen, Palle; Pedersen, Tom Søndergård; Bendtsen, Jan Dimon
Email Print Request Permissions This paper investigates decentralized control structures for absorption cycle heat pumps and a dynamic nonlinear model of a single-effect LiBr-water absorption system is used as case study. The model has four controllable inputs, which can be used to stabilize the...
Enhancement of LNG plant propane cycle through waste heat powered absorption cooling
In liquefied natural gas (LNG) plants utilizing sea water for process cooling, both the efficiency and production capacity of the propane cycle decrease with increasing sea water temperature. To address this issue, several propane cycle enhancement approaches are investigated in this study, which require minimal modification of the existing plant configuration. These approaches rely on the use of gas turbine waste heat powered water/lithium bromide absorption cooling to either (i) subcool propane after the propane cycle condenser, or (ii) reduce propane cycle condensing pressure through pre-cooling of condenser cooling water. In the second approach, two alternative methods of pre-cooling condenser cooling water are considered, which consist of an open sea water loop, and a closed fresh water loop. In addition for all cases, three candidate absorption chiller configurations are evaluated, namely single-effect, double-effect, and cascaded double- and single-effect chillers. The thermodynamic performance of each propane cycle enhancement scheme, integrated in an actual LNG plant in the Persian Gulf, is evaluated using actual plant operating data. Subcooling propane after the propane cycle condenser is found to improve propane cycle total coefficient of performance (COPT) and cooling capacity by 13% and 23%, respectively. The necessary cooling load could be provided by either a single-effect, double-effect or cascaded and single- and double-effect absorption refrigeration cycle recovering waste heat from a single gas turbine operated at full load. Reducing propane condensing pressure using a closed fresh water condenser cooling loop is found result in propane cycle COPT and cooling capacity enhancements of 63% and 22%, respectively, but would require substantially higher capital investment than for propane subcooling, due to higher cooling load and thus higher waste heat requirements. Considering the present trend of short process enhancement payback periods in the
Integrated vacuum absorption steam cycle gas separation
Chen, Shiaguo; Lu, Yonggi; Rostam-Abadi, Massoud
2011-11-22
Methods and systems for separating a targeted gas from a gas stream emitted from a power plant. The gas stream is brought into contact with an absorption solution to preferentially absorb the targeted gas to be separated from the gas stream so that an absorbed gas is present within the absorption solution. This provides a gas-rich solution, which is introduced into a stripper. Low pressure exhaust steam from a low pressure steam turbine of the power plant is injected into the stripper with the gas-rich solution. The absorbed gas from the gas-rich solution is stripped in the stripper using the injected low pressure steam to provide a gas stream containing the targeted gas. The stripper is at or near vacuum. Water vapor in a gas stream from the stripper is condensed in a condenser operating at a pressure lower than the stripper to concentrate the targeted gas. Condensed water is separated from the concentrated targeted gas.
Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander
Zhenying Zhang
2014-08-01
Full Text Available The impulse turbo expander (ITE is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reduction of the friction losses of the rotor. The performance of the novel cycle is investigated based on energy and exergy analysis. A correlation of the optimum intermediate pressure in terms of ITE efficiency is developed. The improved ITE cycle increases the exergy efficiency by 1.4%–6.1% over the conventional ITE cycle, 4.6%–8.3% over the economizer cycle and 7.2%–21.6% over the base cycle. Furthermore, the improved ITE cycle is also preferred due to its lower exergy loss.
Yoon, Won Jae; Jung, Hae Won; Chung, Hyun Joon; Kim, Yongchan [Department of Mechanical Engineering, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-713 (Korea, Republic of)
2011-01-15
A two-circuit cycle with parallel evaporators (called a ''parallel cycle'') for a domestic refrigerator-freezer (RF) shows energy saving potential compared with a conventional cycle with a single loop or serial evaporators because of a low compression ratio in the fresh food compartment (R)-operation. The objective of this study is to investigate the effects of the refrigerant charge, R-capillary tube, and refrigerant recovery operation on the performance of a parallel cycle. In addition, design guidelines for the heat transfer area and air flow rate of an R-evaporator are proposed. When the parallel cycle was optimized in terms of the refrigerant charge and R-capillary tube diameter, the energy consumption was reduced by 7.8% over a bypass two-circuit cycle with the same RF platform. In addition, an additional energy saving of 1.8% was obtained by the optimization of the operating sequence and refrigerant recovery operation. (author)