DETERMINATION OF THERMAL PROPERTIES OF SOLID POROUS MEDIA ON A SINGLE-BLOW TESTING APPARATUS

摘要

The efficiency of regenerative cycle refrigerators greatly depends upon the high performance of the regenerator. The design of high performance cryogenic regenerators is a challenge because several variables must be competitively balanced. Using published correlations, it is relatively easy to design extremely high performance regenerators but there are numerous manufacturing realities that limit observed regenerator performance. A methodology is presented to evaluate solid porous matrices that differ in nature and geometry, by balancing the effective thermal conductivity, heat transfer coefficient and friction factor. We have designed and built a single-blow testing apparatus to measure the design parameters for different porous solid matrices, by flowing a heated fluid through it and recording the temperature profiles as a function of time and location, for different values of Reynolds Number. The determination of these parameters is obtained by fitting the experimental profiles with theoretical profiles from the solution of the energy balance equations in the fluid-solid system. Here, we present the results obtained on Dysprosium sphere particles with average particle size of 288 μm, as an initial demonstration of a characterization and testing methodology for high performance regenerator matrices. Important considerations with respect to the longitudinal conductance are also made.