APPARATUS METHOD TO DETERMINE CONVECTIVE HEATTRANSFER COEFFICIENT FRICTION FACTOR IN REGENERATORS

摘要

The essential component of Active Magnetic Refrigeration (AMR) technology is the regenerator where performance is constrained by imperfect heat transfer between the magnetocaloric material and the heat transfer fluid. Because of the broad range of scales between the hydraulic diameter and the overall size of the regenerator, thermal modeling often uses volume averaged transport correlations. The ability to accurately determine the pressure drop and convection coefficient for a particular matrix is needed for the design and modeling of AMR systems. This paper describes an experimental device used to determine convection coefficient and friction factor by inducing a controlled oscillating sinusoidal water flow across a particle matrix comprised of 1 mm diameter, 304 grade stainless steel spheres. Reynolds Numbers between 100 and 2000 are generated at four distinct utilizations in the range of 0.4 to 0.8. A temperature gradient is established across the matrix and the resulting temperature distribution is recorded Under local cyclic-equilibrium conditions. The results are numerically post-processed to extract convection coefficient and friction factor.