Abstract
Thermal spray coating processes have been employed in the current study to deposit well-adhered, dense skins on the surfaces of open-cell nickel foams. Using foam with 10 and 40 PPI (pores per inch) pore sizes, square channels were made with a height of 20mm and having a length of 250mm. In a unique process that prevents the deposited skin from penetrating the foam substrate via a paste comprised of a thermoset resin and powder particles, a dense stainless steel skin with an average thickness of 400 μm is applied to the exterior of the foam sample. The result is a channel that consists of a Ni foam core and a stainless steel skin wall that can be used as a compact heat-exchanger by directing the coolant flow through the foam. To study the feasibility of the metallic foam heat-exchangers, hydraulic and heat-transfer characteristics were investigated experimentally. The local wall and fluid temperature distribution and the pressure drop along the length of the heat exchanger were measured for heat-flux of 1540.35 – 9627.38 W/m2. Experiments were conducted using air as the coolant and varying flow velocity from 10 – 80 L/min. For non-Darcy flow with inertia effects in the porous media, the Dupuit and Forchheimer modification is employed with the experimental results to determine foam characteristics such as permeability (K), Ergun coefficient (CE) and the friction factor (f). To measure the heat-transfer performance of the metal foam filled channels, a length average Nusselt number is derived based on the local wall and fluid temperatures. Heat transfer was shown to have nearly doubled compared to that of a channel without a foam core.
