Selection of regenerator geometry for magnetic refrigerator applications (original) (raw)
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Performance Evaluation of Room Temperature Magnetic Refrigerator Using Corrugated Plate Regenerator
Magnetic refrigeration near room temperature is a promising non-conventional technology with a realistic potential to replace the conventional cooling systems such as vapor compression. Active magnetic regenerator (AMR) is the key component determining the cooling performance of a magnetic refrigerator. A numerical analysis of the active magnetic regenerator was performed considering two different regenerator geometries (a) corrugated and (b) flat plate for a range of utilization. Gadolinium was taken as the magnetocaloric material and water as the heat transfer fluid. The numerical simulation was performed using ANSYS Fluent with user-defined functions. The peak performance for both the regenerators was found at utilization value of 0.8. It was found that the corrugated plate regenerator exhibited larger temperature spans than the flat plate regenerator in the given range of utilization. The maximum no-load temperature span of corrugated plate regenerator was seen to be around 5% higher than the flat plate.
Optimization of layered regenerator of a magnetic refrigeration device
International Journal of Refrigeration, 2015
Magnetic refrigeration, as an alternative to vapor-compression technology, has been the subject of many recent investigations. A technique to enhance the performance of magnetic refrigerators is using layers of different materials in the regenerator of such devices. In this study the choice of magnetocaloric materials in a multi-layered packed bed regenerator is investigated in order to optimize the performance. A numerical model has been developed to simulate the packed bed in this study. Optimized packed bed designs to get maximum temperature span or maximum efficiency are different. The results indicate that maximum temperature span can be achieved by choosing the materials with the highest magnetocaloric effect in the working temperature range, while maximum Carnot efficiency is achieved by choosing materials with Curie temperatures above the average layer temperature.
Experimental studies with an active magnetic regenerating refrigerator
2015
Experimental results for an active magnetic regenerator (AMR) are presented. The focus is on whether or not it pays off to partly substitute soft magnetic material with non-magnetic insulation in a flux-conducting core in the magnet system. Such a substitution reduces losses due to heat conduction and eddy currents, but also reduces the magnetic field. Two different cores were tested in the AMR system with different cooling loads and it is shown, that in the present case, replacing half of the iron with insulation lead to an average reduction in temperature span of 14%, but also a small decrease in COP, hence the substitution did not pay off. Furthermore, it is shown experimentally, that small imbalances in the heat transfer fluid flow greatly influence the system performance. A reduction of these imbalances through valve adjustments resulted in an increase in the temperature span from approximately 16 K to 27.3 K.
International Journal of Refrigeration, 2016
A hybrid numerical model of the magnetic refrigerator with multi-material microchannel regenerator has been developed. The magnetocaloric effect was implemented using instantaneous temperature rise/drop (discrete method). Two pipe-in-pipe heat exchangers at two ends of the regenerator were treated using ε-NTU method. The commercially available compounds of LaFe 13-xy Co x Si y as well as hypothetical compounds of Gadolinium were considered as the magnetocaloric materials (MCMs) with different Curie temperatures. The predicted results of the present work for parallel regenerators employing different compounds of LaFe 13-x-y Co x Si y were broadly in good agreement with the available experimental data. The cooling capacity increases as the number of MCMs increase. However, for a given length of regenerator, an optimum number of MCMs was seen yielding the maximum performance of the refrigerator. For a given number of MCMs, a smaller Curie temperature difference ΔT Cu between the MCMs was found to give higher performance.
Applied Thermal Engineering, 2015
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Analysis of room temperature magnetic regenerative refrigeration
International Journal of Refrigeration, 2005
Results of a room temperature magnetic refrigeration test bed and an analysis using a computational model are presented. A detailed demonstration of the four sequential processes in the transient magnetocaloric regeneration process of a magnetic material is presented. The temperature profile during the transient approach to steady state operation was measured in detail. A 5 8C evolution of the difference of temperature between the hot end and the cold end of the magnetocaloric bed due to regeneration is reported. A model is developed for the heat transfer and fluid mechanics of the four sequential processes in each cycle of thermal wave propagation in the regenerative bed combined with the magnetocaloric effect. The basic equations that can be used in simulation of magnetic refrigeration systems are derived and the design parameters are discussed. q
Practical Study of Magnetic Refrigeration Performance and Optimization
Active Magnetic Refrigeration Apparatus is a novel device that has zero vapor pressure and causes, zero ozone depleting gases. The magnetic refrigerator has the prospective to become a realistic choice instead of present vapor compression refrigeration systems. In the present study a Magnetic refrigerator designed and constructed in Iraq (the first one as our knowledge), used as laboratory device to investigate the effects of many operational parameters on its performance. The results indicated that an experimental parallel plate AMR device demonstrates the high performance, and due to their relatively low pressure drop to the heat transfer performance and to be quite versatile, in terms of operational parameters and various aspects of the cooling capacity .The hot end had a prescribed temperature of 299K a zero cooling loads applied at the cold end. So, temperature span observes be about 11K, which evaluated as the difference temperature between the hot and cold ends of the magnetocaloric regenerator. All thermal losses through the regenerator housing and the cold end go to the ambient through the hot end, within an insulated cold end, due to, no heat exchangers were used at the cold and hot ends. Therefore, this test machine used to measure the no-load temperature span.
Magnetic Refrigeration Design Technologies: State of the Art and General Perspectives
Energies, 2021
Magnetic refrigeration is a fascinating superior choice technology as compared with traditional refrigeration that relies on a unique property of particular materials, known as the magnetocaloric effect (MCE). This paper provides a thorough understanding of different magnetic refrigeration technologies using a variety of models to evaluate the coefficient of performance (COP) and specific cooling capacity outputs. Accordingly, magnetic refrigeration models are divided into four categories: rotating, reciprocating, C-shaped magnetic refrigeration, and active magnetic regenerator. The working principles of these models were described, and their outputs were extracted and compared. Furthermore, the influence of the magnetocaloric effect, the magnetization area, and the thermodynamic processes and cycles on the efficiency of magnetic refrigeration was investigated and discussed to achieve a maximum cooling capacity. The classes of magnetocaloric magnetic materials were summarized from previous studies and their potential magnetic characteristics are emphasized. The essential characteristics of magnetic refrigeration systems are highlighted to determine the significant advantages, difficulties, drawbacks, and feasibility analyses of these systems. Moreover, a cost analysis was provided in order to judge the feasibility of these systems for commercial use.
International Journal of Refrigeration, 2014
In this paper, numerical and experimental investigations on a magnetic refrigeration device based upon the active magnetic regeneration (AMR) cycle operating near room temperature are presented. A numerical 1D model based on the transient energy equations is proposed for modelling the heat exchange between the magnetocaloric material and the carrier fluid in the regenerator bed. The validity of 1D AMR-numerical model is investigated through the recently developed magnetic cooling demonstrator by Clean Cooling Systems SA (CCS) at the University of Applied Sciences of western Switzerland (HESÀSO). The obtained results including the temperature span, the coefficient of performance and the cooling power are presented and discussed. In general, good agreements have been noted between the experimental and numerical results.
Optimization of Active Magnetic Regenerative Refrigeration Cycles with Design of Experiments
2008
This paper attends to demonstrate the usefulness of Design of Experiments (DOE) method in magnetic refrigeration (MR) understanding and optimization. A numerical DOE is applied to a simple 1D finite difference model describing an Active Magnetic Regenerative Refrigeration (AMRR) system. The heat transfer fluid is water, the regenerator consists of stacked gadolinium plates and the model is based on the assumption of an equivalent single plate. A two-level 2 7-3 fractional DOE based on Box methodology is used to evaluate the effect of seven parameters on the temperature span, namely material and fluid thicknesses, length, equivalent width, mass flow rate, cycle frequency and magnetocaloric effect (MCE).