Using Porous Fins for Heat Transfer Enhancement

Abstract

This work introduces a novel method that enhances the heat transfer from a given surface by using porous fins. The thermal performance of porous fins is estimated and compared with that of the conventional solid fins. It is found that using porous fin of porosity ε may enhance the performance of an equal size conventional solid fin and, as a result, save 100 ε percent of the fin material. The effect of different design and operating parameters on the porous fin thermal performance is investigated. Examples of these parameters are Ra number, Da number, and thermal conductivity ratio. It is found that more enhancement in the porous fin performance may be achieved as Ra increases especially at large Da numbers. Also, it is found that there is an optimum limit for the thermal conductivity ratio beyond which there is no further improvement in the fin performance.

Thermal Analysis of Natural Convection Porous Fins

“…It should be noted that in the following figures wherever the following values are needed they are fixed as follows: Da = 1 × 10 −6 , Ra = 1 × 10 7 , and L = 0.125 m, t = 0.025 m, W = 1, and k s = 204,W/m K, K r = 3200 and the convection heat transfer coefficient for the case of solid fin is h = 15 W/m 2 K. These values are the same values used by (Kiwan and Al-Nimr, 2001) to study porous fins. They are adopted here for comparison purposes.…”

“…Porous blocks have been used to control the flow and heat-transfer characteristics of an external surface (Huang and Vafai, 1994). Kiwan and Al-Nimr (2001) introduced the concept of using porous fins to enhance the heat transfer from a given porous surface. The basic philosophy behind using porous fins is to increase the effective area through which heat converted to ambient fluid.…”

Investigations of fin geometry on heat exchanger performance by simulation and optimization methods for diesel exhaust application

“…Though production cost is often the primary limitation, several other selection aspects such as temperature ranges, pressure limits, thermal performance, pressure drop, fluid flow capacity, clean-ability, maintenance and materials, are important issues. One of the most effective methods to increase heat transfer is using the extended surfaces or fins which are widely used by the researchers [5][6][7][8][9]. Some of the special HEX designs to recover the exhaust heat are introduced in the following.…”

Experimental Pressure Drop and Heat Transfer in a Rectangular Channel With a Sinusoidal Porous Screen

“…The objectives of the studies are to replace the solid fins with the porous fins that provide similar thermal performance as the solid fins but with the advantage of significant weight reduction for the compact heat exchanger design. The investigations [6,7] show the augmentation of heat transfer and friction factor in a porous finned channel relative to a smooth channel with varying effects from the fin geometry, porosity, and thermal conductivity. Numerical and experimental investigations by Zhang and Chen [8] report the mean f and Nu across periodic triangular ducts where the walls are solid non-porous.…”

“…Numerical models by Kiwan and Al-Nimr [6], and Hamdan and Al-Nimr [7] employ 1-dimensional porous fins periodically between parallel plates to perturb laminar flow. The objectives of the studies are to replace the solid fins with the porous fins that provide similar thermal performance as the solid fins but with the advantage of significant weight reduction for the compact heat exchanger design.…”