EFFECTS OF VARIABLE THERMAL CONDUCTIVITY OF WATER-BASED NANOFLUIDS SATURATED WITH POROUS MEDIUM ON NATURAL CONVECTION HEAT TRANSFER ENHANCEMENT

In this work, the natural convection fluid flow and heat transfer in a vertical rectangular duct filled with nanofluids and saturated with a porous medium was investigated numerically. The non-Darcy model was used to define the porous matrix. Water was used as the base fluid with different types of nanoparticles, such as copper, titanium oxide, silver, and diamond. The flow was considered to be laminar and fully developed, the thermal conductivity was assumed to vary linearly with the temperature, and the viscosity was assumed to be constant with the temperature. The two-dimensional Navier-Stokes and energy equations were solved simultaneously using the finite-difference method. The effect of the fluid flow and heat transfer characteristics, such as the velocity, temperature, volumetric flow rate, skin friction, and rate of heat transfer distribution in the duct, was investigated. The results showed that the flow accelerates with an increase in the variable thermal conductivity parameter, Grashof number, Brinkman number, and aspect ratio, whereas the inertial parameter and solid volume fraction decelerates the flow. The rate of heat transfer increased for the nanofluid when compared to the regular fluid for all of the nanoparticles considered in the study.