Simulation And Analysis Of The Heat Transfer In Room-temperature Magnetic Refrigerator

Room-temperature magnetic refrigeration is a high efficiency,energy saving and environment friendly cooling technology. Althoughthis technology has not got commercial applications yet, recent studiesshow that it is a most potential for replacing conventional coolingtechnology and may have practical applications soon. However, theroom-temperature magnetic refrigeration is a system engineering,effective heat transfer is an important part of magnetic refrigeration. Inthis paper, we report on the establishment of heat transfer model based onan improved Navier-Stokes equation for the AMR cycle reciprocatingmagnetic refrigerator, and the simulation of the magnetic refrigerationcycle of Gadolinium using numerical simulation method. With onedimensional heat exchanging model, we studied the effects of the porosityon the temperature span between hot side and cold side. Keeping theother parameters, we studied the effects of cycle frequency and fluidvelocity on the cooling capacity. With two dimensional heat exchangingmodel, we mainly studied the temperature distribution characteristics inregenerator, and discussed the impact of the length of regenerator ontemperature distribution. The theoretical and numerical results arefollowing: In one-dimensional model, as the porosity ranges from0.15to0.4, thesmaller the value of porosity the better cooling capacity. While the cyclefrequency ranges from0.21Hz to0.42Hz, the higher frequency leads tohigher cooling capacity. When the fluid velocity ranges from0.2m/s to0.4m/s, the faster velocity makes the higher cooling capacity.In two-dimensional model, the temperature distribution in thecooling chamber has a gradient. The temperature is high near the hot sideand low near the cold side. In a certain time, the increase of regeneratorlength will lead to nonuniform temperature distribution, but thetemperature span has any change. With increasing operating time, thetemperature span becomes larger and the temperature distributionbecomes uniform, indicating that the heat exchange becomes better withincreasing length of regenerator.This work is important for understanding the heat exchange process inmodern magnetic refrigerators, how to select heat exchange media, howto design the size of cooling chamber, how to select a proper coolingrefrigerant.