Flow through Concentric Annuli for Different Cross Sections at Varied Porosities

Abstract

Magnetic refrigeration is an alternative way to provide cooling at room temperature. The magnetocaloric effect (MCE) is the basis of magnetic refrigeration. When a magnetocaloric material gets adiabatically magnetized or demagnetized, the entropy within the material changes. The material will then either reject or absorb heat. Recently, there have been more studies on the subject with the aim of solving some of the design challenges in order to achieve a more optimal system. Space constraints need to be considered when designing a magnetic refrigeration system. One way to help develop a more efficient system is to look at the cross sectional shape of the duct where the cooling fluid flows. More specifically, the annular geometry where the magnetocaloric material is the boundary for the inner radius of the annulus, and the magnets are the boundary for the outer radius of the annulus. The purpose of this study is to compare the pressure drop and heat transfer of water flowing through different cross sectional geometries containing porous media in order to verify which geometry is best suited for optimal design of magnetic refrigeration systems. More specifically, this study is based on a magnetic refrigeration set up in which the magnetic field was generated from a magnetization process for a k = 2 configuration. Circular, hexagonal, and square annular geometries will be considered with porosities of pure aluminum media at 0.2, 0.4, 0.6, 0.8, and 1. For non-circular geometries, the given shape making up the annulus will be inscribed by the circle created by the inner and outer radius.