Er3Ni颗粒4-40 K温区表观热导率测量及其回热器漏热研究

The apparent thermal conductivity of Er3Ni particles at 4-40 K and measures to reduce the heat leakage of its regenerator

摘要:

磁性材料的应用对低温制冷机的发展有着重要的意义。目前磁性材料在液氮以下温区热物性参数的缺乏严重限制了制冷机回热器的设计与优化。研制了颗粒状磁性材料低温表观热导率测量装置，对Er3Ni在4-40 K及不同氦气压力下的表观热导率进行了测量并计算了Er3Ni热导率系数。在不同温区的测试结果表明，真空状态下，Er3Ni颗粒表观热导率为0.11-0.22 W/m·K，对应的热导率系数为0.31-0.53；当氦气压力增大至1.4-2.2 MPa后，表观热导率趋于稳定，稳定后的平均值为3 W/m·K，对应的热导率系数为7。进一步研究了Er3Ni型回热器不同工况下的漏热特性，提出了丝网与颗粒混合填充的方案以降低冷热两端的轴向漏热。结果表明，在Er3Ni回热器中混合填充尼龙网和316 L不锈钢丝网后制冷性能显著提高，在1.6 MPa压力下漏热降低幅度分别高达12%和8%。

Abstract:

The application of magnetic materials is of great significance to the development of cryocoolers. At present, the lack of thermal properties of magnetic materials at temperatures below 80 K severely limits the design and optimization of cryocooler regenerators. A low-temperature apparent thermal conductivity measurement apparatus for granular magnetic materials has been developed. The apparent thermal conductivity of Er3Ni under various pressures of helium in the 4-40 K temperature range has been measured, and then its thermal conduction factor has been calculated. The test results in different temperature ranges show that the apparent thermal conductivity of Er3Ni particles is 0.11-0.22 W/m·K under vacuum, corresponding to the thermal conduction factor of 0.31-0.53. When the pressure increases to 1.4-2.2 MPa, the apparent thermal conductivity tends to a definite value of 3 W/m·K, corresponding to the thermal conduction factor of 7. Furthermore, the heat leakage characteristics of the Er3Ni regenerator under different operating conditions have been studied, and a mixed filling scheme of particles with wire mesh has been proposed to reduce the axial heat leakage between the cold and hot ends of the regenerator. The results show that the cooling performance can be improved after the nylon mesh and 316 L stainless steel mesh are filled in the Er3Ni regenerator, and the reduction of heat leakage under the pressure of 1.6 MPa helium is as high as 12% and 8%, respectively.