Study On The Flow And Heat Transfer Laws Of Working Medium In The Stack Of Thermoacoustic Refrigerator

Thermoacoustic refrigerator is based on the theory of thermoacoustic effect.It transfers the heat of the object to be cooled with lower temperature to the environmental medium to obtain cooling capacity.With its unique advantages of cleanliness and environmental protection,it has attracted the attention of the world.However,there are low cooling efficiency,miniaturization difficult technical bottlenecks existing thermoacoustic refrigerator,not widely used.To improve cooling efficiency,herein,the following studies conducted around the heat exchanger and the law of motion between the stack and the plate under the gas micelles acoustic standing wave field.In this paper,the Lagrangian method is used to calculate the corresponding control equations for the moving micro air masses.The time-space equation of the physical parameters of the micro gas mass under the influence of the standing wave sound field is derived.The mathematical model of heat transfer between the micro gas mass and the plate stack in the thermal cycle is established.The model of temperature change and heat exchange with solid plate stack is established by the numerical simulation method.The temperature and heat change at any time during vibration refrigeration are analyzed in detail.The optimal combination of parameters of each working condition is explored by selecting the appropriate level and orthogonal table to simulate the experiment,and the way to improve the refrigeration efficiency is studied.Through the establishment of a test platform for experimental exploration,the test results are compared with the numerical simulation results,and the influence of each parameter on the refrigeration effect is grasped.The thermal cycle of the micro gas mass on the plate stack is divided into four parts.During the process of movement,the gas micro mass has undergone compression,heat release,expansion,and heat absorption.The micro gas mass is compressed with the increase of pressure and the internal energy increases;the pressure decreases and the internal energy decreases.The microclusters are heat-absorbing on the right side of the balance position and the plate stack is exothermic on the left side of the balance position.But in the whole cycle,the micro air mass has no net heat exchange and no energy consumption on both sides.This shows that the gas inside the stack in the pure standing wave sound field can move heat,pumping the sound work and the absorbed heat to the high-temperature end.The numerical simulation results show that the most important factor to the refrigeration process is the thermal conductivity of the laminated material,followed by the amplitude of the gas micro clusters,the lowest is the vibration frequency,and the optimal factor level combination is(A3B4C4).The selection of laminated materials is superior to other factors,and the amplitude control is second to the material selection.Under the condition that the sensitivity of the first two factors is taken to a better level,the vibration frequency can be selected in a large range,which provides the basis for obtaining a large amplitude.The amplitude and frequency are considered independent factors.It is found that the effect of refrigeration is not affected by the frequency changing in a wide range.The results of the orthogonal test indicate that the excitation frequency can be set on the first-order piston modal frequency to obtain the maximum amplitude without considering the influence of frequency variation.Through experimental exploration and analysis combined with numerical simulation results,it is concluded that asbestos material is the material with the best temperature difference effect among the selected materials.Different thermal conductivity has a greater influence on temperature difference,and the larger the amplitude,the greater the temperature difference.Through the above research,it provides a theoretical basis for the optimization of the parameters of the thermoacoustic refrigerator and the improvement of the cooling effect.