Numerical Investigation of Thermofluid Performance of a Regenerator Relative to the Matrix Geometry

Abstract

Regenerators are essential component of systems such as Stirling engines, gas turbines and even IC engines. Designing compact and high performance regenerative system however is quite difficult and has impeded the development of engines such as Stirling engine despite its multifuel capability and potential of reducing the dominance of fossil fuel as a primary energy source. Here the Flow dynamics through regenerators defined by channel matrix geometry and how they impact on convective heat transfer and pressure losses in the system were studied for 0.01<Re<950 using ANSYS FLUENT. Ten values of Re were considered within this range for three matrix geometries-sphere, cube and diamond. Heat transfer in the systems were strongly influenced by the area of convective heat transfer surface, scale of vortex formed and the thermal boundary layer thickness developed from the point of flow separation. The friction coefficient (C f) which measures the pressure losses were found to be proportional to the size of the wake or recirculating region downstream of the flow. The suitability of a geometry for use in regenerator matrix design was determined by the ratio of C f to heat transfer per unit area of matrix. The sphere and diamond matrix gave a similar and better performance than the cube for the range of Re considered.