Study On Convective Heat Transfer Characteristics In Partially Filled Porous Media Channnel Considering Internal Heat Source

The heat transfer problem of porous media considering internal heat source is widely existed in some engineering applications,such as absorption and exothermic reaction in chemical reaction,heat dissipation of electronic devices,storage and preservation of agricultural products in agriculture,spontaneous combustion of combustible materials（pulverized coal）and so on.It is of practical significance to study convective heat transfer characteristics in partially filled porous media channels with internal heat source.Firstly,based on the LTNE model,the fluid flow and heat transfer characteristics in a partially filled porous media channel with internal heat source are studied.It is assumed that the internal heat source exists in the solid phase of the porous medium region.The Brinkman-extended Darcy model is used to calculate the equation of motion in the porous media region.At the interface between the porous media region and the free fluid region,the interface model of continuous velocity and stress jump is adopted.Ignoring the effects of radiation heat transfer and natural convection,the analytical solutions of the velocity and temperature distributions of the fluid in the partially filled porous channel with internal heat source are obtained.The influence of different characteristic parameters such as interfacial stress jump coefficientβ,internal heat source W_s,Biot number Bi,thermal conductivity ratio K,Darcy number Da and dimensionless height S in free fluid zone on the heat transfer performance of the channel is analyzed,and the maximum flow solid temperature difference valueΔθ_max in porous medium is also analyzed.The results show that the influence ofβon fluid velocity needs to be considered when Da is large,S is small andβis low.When Da is small,the fluid velocity in porous media will appear a velocity called Darcy velocity which does not change with Y,and this Darcy velocity will decrease with the decrease of Da.Considering that the temperature difference of fluid-solid two phases in porous media under internal heat source is larger than that without internal heat source,increasing Bi,decreasing K,increasing S,decreasingβand decreasing Da will all lead to decreasing temperature difference of fluid-solid two phases in porous media.In addition,when introducing the inner heat source,the influence law of K and Bi as the delta theta Max with no inner heat source is the same,the smaller K,Bi larger and larger S can make as the maximum temperature difference between the two phase delta theta maximum decreases,and show the effectiveness of LTE,increases the W_s absolute value increases solid two phase flow of porous medium temperature difference,the need to consider the local thermal equilibrium effect.The influence of Da onΔθ_max is not negligible only when K is large and S is small.It is worth mentioning that the temperature bifurcation of the fluid-solid phase in the porous medium will occur when the heat absorption and exothermic properties of the internal heat source are changed.The numerical solutions of velocity and temperature distribution and Nusselt number in each region of the partially filled porous media channel are obtained by using finite difference method,and the influence of related parameters on velocity field,temperature field and Nusselt number is further analyzed.The results show that the influence of the inertia parameter F_f on the fluid velocity in each region of the channel will be weakened by the decrease of Da and the increase of the hollow rate S,and the influence of F_f on the fluid velocity only needs to be considered when Da is large and S is small.Nu gradually decreases with the increase of heat source W_s in the solid phase.A small change of W_s will make Nu change greatly,so it can be seen that W_s has a great influence on the heat transfer effect of the channel.Increasing F_f and decreasing the absolute value of W_s will reduce the temperature difference between the two phases,and the influence of Bi,W_s and F_f on the temperature distribution in the channel is more obvious when K is larger.However,whether F_f is considered or not,the change of the heat absorption and exothermic property of W_s is consistent to the fluid-solid temperature bifurcation phenomenon in the channel.