The Research Of Refrigeration Performance For A Combined Type Permanent Magnet Room Temperature Magnetic Refrigerator

Room temperature magnetic refrigeration is a novel refrigeration technology.Comparing to the traditonal vapor compression refrigeration the room temperature magneticrefrigerrtion has no harm for the environment with high thermaldynamic cycle efficiency. Anovel large scale permanent magnet room temperature magnetic refrigerator is presented inthis paper. The key components of it are consisted of magnetic fields and active magneticregenerator paked wirh porous magnetocaloric materials. The magnet fields are provided bynesting concentric Halbach cylinder arrays which are made of NdFeB permanent magnets.The two magnetic fields keep180°phase angle meshed with gears. In this way, thecirculation frequency can be promoted and it can accelerate the formmation of thetemperature span of regenerators. The rotation of internal cylinders can alter magnetic fieldsto meet the magnetocaloric materials accomplishing the thermal dynamic cycle of Brayton.In order to make providing refrigerating capacity for freezers with large volumebecome a reality, many cooling perfomances of this room temperature magnetic refrigerator,for exemple, cooling temperature span, the temperature of cold end, cooling rate and coolingpower, have been studied with different curie temperatures magnetocaloric materials, cycletime, active magnetic regenerator beds and magnetic field structures.Firstly, the spherical particles of Gd based alloys are as the benchmark study. Thediameter of spherical particles is0.3—0.5mm, and the porous rate of active magneticregenerator beds is about36%. Different single cycle volume of heat transfer fluid which canimpact the refrigerator’s cooling capacity are presented to determine the optimal single cyclevolume in order to make the room temperature magnetic refrigerator reach best coolingcapacity under other conditions constant.Secondly, to determine the performance of different curie temperature magnetocaloricmaterials, the research studied the cooling temerature span and cooling power under varyroom temperature. Learned the affect of room temperature for regenrrator beds and find approriate cooling power formula. Three kinds of Gd based materials can obtain15.9Ktemperature cooling temperature span for about2hours with117liters refrigerator box. Thecooing power is about186W. So far the cumulative running time of the prototype has beenmore than236hours.Furthermore, We also design the lower magnetic field to reduce the cost. Manyexperiments’ results presents better perfomance than the original magnetic field. With65liters freezers this magnetic refrigerator can achieve the maximal temperature span26.4K.The maximal cooling temperature span is21K. The temperature breakthrough272K(-1℃)within freezer and the temperature of cold end can achieve269.4K. This means that themagnetic refrigerator can provide cooling capacity for a freezer.Finally, the research studied four kinds curie temperature LaFeCoSi alloys pakedregenerator beds under lower magnetic field. The research also studied the relationshipbetween the angle of isofield process and perfomance of refrigerator to accord with thethermal dynamic cycle of Brayton in theory and to weaken the inevitable designed error. Thetests’ results demonstrate that the small angle of isofield process displayed better result.Many tests are performed to demonstrate that the time magnetization process ordemagnetizition process will influence the cooling results. If the cycle time isdecreacing, the cooling perfomance of both process will be better. The results conformto the adiabatic demagnetization theory.