Numerical investigation of effect of central gap's width and length of magnetic material on heat transfer and pressure loss of water flow using computational fluid dynamics

摘要

This research studied heat transfer and pressure loss due to water flow through the compressed magnetic powder using Computational Fluid Dynamics. The Reynolds number was determined, ranging from 3, 000 to 7, 000, corresponding to the working flow-rate range in the magnetic refrigeration system. To model the compressed magnetic powder as porous media, the porosity and permeability, calculated from experimental results, were 0.1684 and 3.3076×10~(-10) m~2, respectively. In this research, porous media which have constant heat flux, were in a cylindrical shape. They had a diameter of 0.012 m and 0.05, 0.10 and 0.15 m in length. The width of the central gap was 0.001, 0.002, 0.003, 0.004 and 0.005 m. The numerical results showed that the Nusselt number and the friction factor increased when the width decreased and the length increased. The maximum friction factor and the Nusselt number were 27.85 and 16.83, respectively at 0.001 m in width and 0.15 m in length under the Reynolds number of 3, 000. However, the highest thermal performance was 1.91 at 0.004 m in width and 0.15 m in length under the Reynolds number of 7, 000. The results obtained in this research could be utilized for the geometric design of magnetic material for the magnetic refrigeration system in the future.