Magnetic refrigeration: The promise and the problems (original) (raw)

Study of Room Temperature Magnetic Refrigeration

2020

In this paper Thermodynamic performance analysis for a magneto caloric material such as Gadolinium and Terbium is presented. Performance parameter is taken as magnetic entropy change and temperature change at constant room temperature, different magnetic fields. Furthermore the thermodynamic performance is compare between gadolinium and Terbium. Also, a study on the development of magnetic refrigerator at room temperature has been also carried out a model of Rotating Magnetic refrigeration has been developed. By use of MCE it is possible to create magnetic refrigerators—the machines where magnetic materials are used as working bodies instead of a gas, and magnetization/demagnetization is used instead of compression/expansion in conventional refrigerators. To realize any cooling process, it is necessary to have a system in which entropy depends on temperature and some external parameter. In the case of a gas this parameter is pressure, and in the case of a magnetic material it is mag...

AN INTRODUCTION TO MAGNETIC REFRIGERATION

At present a great amount of research work is performed to develop new magneto caloric materials, which are the refrigerants of magnetic refrigerators. This leads to a continuous development of more performant magnetic refrigerants with higher entropy differences ∆S, higher adiabatic temperature differences ∆T ad and lower hysteresis effects. Also an increased activity to design better thermo-magnetic refrigerators is occuring and numerous promising patents on machines with magneto caloric porous beds have been deposited. In a new IIR working party on magnetic refrigeration the different activity groups get into close relation, leading to welcome interactions between material scientists, physicists working on magnetism and specialists on fluid dynamics and thermodynamic machine design. All these increasing activities lead to a very high potential of magnetic refrigerators for a market penetration, which most probably at first will occur in some niche markets. After that for some main sales domains of refrigeration -e.g. as for usual commercial refrigerators -an entrance to the market also seems feasible. Other markets are in air conditioning, heat pump applications, process technics, automobile industry, medical domains, etc.

Magnetic refrigeration-towards room-temperature applications

… B Condensed Matter, 2003

Modern society relies very much on readily available cooling. Magnetic refrigeration based on the magneto-caloric effect (MCE) has become a promising competitive technology for the conventional gas-compression/expansion technique in use today. Recently, there have been two breakthroughs in magnetic-refrigeration research: one is that American scientists demonstrated the world's first room-temperature, permanent-magnet, magnetic refrigerator; the other one is that we discovered a new class of magnetic refrigerant materials for room-temperature applications. The new materials are manganese-iron-phosphorus-arsenic (MnFe(P,As)) compounds. This new material has important advantages over existing magnetic coolants: it exhibits a huge MCE, which is larger than that of Gd metal; and its operating temperature can be tuned from about 150 to about 335 K by adjusting the P/As ratio. Here we report on further improvement of the materials by increasing the Mn content. The large entropy change is attributed to a fieldinduced first-order phase transition enhancing the effect of the applied magnetic field. Addition of Mn reduces the thermal hysteresis, which is intrinsic to the first-order transition. This implies that already moderate applied magnetic fields of below 2 T may suffice. r 2002 Published by Elsevier Science B.V. Keywords: Magnetic refrigeration; Magneto-caloric effect 0921-4526/03/$ -see front matter r 2002 Published by Elsevier Science B.V. PII: S 0 9 2 1 -4 5 2 6 ( 0 2 ) 0 1 7 6 9 -6

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.

Solid state magnetic refrigerator

2012

The viability and operation of a fully solid state magnetic refrigeration system with envisaged applications on chip, sensor and device cooling is here tested using numerical simulations. The proposed system relies on the combined use of materials displaying the magnetocaloric effect and of materials whose thermal conductivities are controlled by an external magnetic field. This allows the switching of the heat flow direction in sync with the temperature variation of the magnetocaloric material, removing the necessity to use fluids which has for long hindered the implementation of magnetic refrigeration. We have found the optimum operating conditions of the proposed refrigerator, for which a cooling power density of 2.75WcmAˋ2wasobtainedforanoperatingtemperatureof2.75 W cm À2 was obtained for an operating temperature of 2.75WcmAˋ2wasobtainedforanoperatingtemperatureof296 K, using Gadolinium as the magnetocaloric material and an applied magnetic field of 1 T. The coefficient of performance (COP) achieved by this refrigerator was found to be COP $1.5, making it a viable alternative to thermoelectric refrigeration.

Magnetic Refrigeration: The Modern Refrigeration Technique-A Review

International Journal of Analytical, Experimental and Finite Element Analysis, 2020

This paper involves the information about type of newly refrigeration. The aim of this study is to give the working principle, operating cycle of the cooling due to the magnetic field. The aim behind the cooling effect is Magneto-Caloric effect MCE. According to this effect when magnetic material like gadolinium is subjected to field developed due to the magnet, temperature of that material increases and when source to develop the magnetic field is removed it returns to its normal temperature. The cooling effect caused uses the magnetic effect in the various ways. Gadolinium is kept as it will pass through magnetic field. As it transfers through the magnetic field the gadolinium heats up as it enters the magneto-caloric effect. There is need to circulate the cooled water to remove the heat out of the metal when it is in magnetic field. As the material lives the source of field, the materials decreases its temperature down its original temperature as the result of magnetic effect. Then this cold gadolinium is used to remove the heat from the refrigerator coils.

Design Principles and Performance Metrics for Magnetic Refrigerators Operating Near Room Temperature

2014

In the past decade, active magnetic regenerative (AMR) refrigeration technology has progressed towards commercial application. The number of prototype systems and test apparatuses has steadily increased thanks to the worldwide research efforts. Due to the extensive variety of possible implementations of AMR, design methods are not well established. This thesis proposes a framework for approaching AMR device design. The University of Victoria now has three functional AMR Refrigerators. The newest system constructed in 2012 operates near-room-temperature and is intended primarily as a modular test apparatus with a broad range of control parameters and operating conditions. The design objectives, considerations and analysis are presented. Extensive data has been collected using the machines at the University of Victoria. Performance metrics are used to compare the devices. A semi-analytical relationship is developed that can be used as an effective modelling tool during the design process.

Material requirements for magnetic refrigeration applications

International Journal of Refrigeration-revue Internationale Du Froid, 2018

A primary motivation underlying the research on room-temperature magnetic refrigeration is reaching energy efficiency levels beyond what is achievable with vapor-compression technology. However, the goal of building commercially viable magnetic refrigeration systems with high performance and competitive price has not been achieved yet. One of the obstacles to reach this goal is the inadequate properties of the currently existing magnetocaloric materials. In this article, the needed improvements in the properties of the magnetocaloric materials is investigated. Two existing vapor-compression refrigerators are used as reference for the required performance, and magnetic refrigerators are simulated using a numerical model. Apart from the requirements such as uniformity of transition temperature for each layer, small increment in transition temperature in adjacent layers, and mechanical strength of the materials, the study shows that for the investigated cases materials with adiabatic entropy change 2.35 times larger than the existing materials are needed to outperform vapor-compression systems.