Study of pressure drop-flow rate and flow resistance characteristics of heated porous materials under local thermal non-equilibrium conditions

Abstract

Porous materials are used as pneumatic components in a wide range of industrial applications. Such porous materials contain thousands of interconnected irregular micro-pores that produce a large pressure drop (ΔP) between the upstream and downstream sides of the porous material when a fluid flows through it. The relationship between the pressure drop and flow rate (i.e., the ΔP−G characteristic) and the relationship between flow resistance (γ) and flow rate (the γ-G characteristic) are two very important basic characteristics. One factor affecting them is temperature, whose variation changes the viscosity and density of the fluid. In this study, we experimentally and theoretically analyzed the effect of temperature on ΔP−G and flow resistance characteristics of porous materials by heating them under constant electric heating power. The resulting experimental ΔP−G and flow resistance curves shift upward relative to their counterparts at room temperature owing to the increase in fluid temperature, but remain within the adiabatic and room temperature curves. The temperature-effect ratio η at constant heating power increases from 1.3 to 1.7 as the flow rate decreases from 21.53×10−5kg/s to 5.80×10−5kg/s, indicating that ΔP−G and flow resistance characteristics and pumping power change significantly when a porous material is heated. Furthermore, temperature distributions were obtained numerically to gain deeper understanding of the temperature effect. The effects of heating power values, characteristic porous material coefficients, and average fluid density on ΔP−G and flow resistance characteristics were also investigated.