An experimental investigation on heat transfer enhancement of sprayed wire-mesh heat exchangers

Three different porosities of aluminum wire meshes (10PPI, 14PPI, 20PPI) and three different diameters of aluminum wires were used to fabricate heat exchangers by connecting aluminum tubes to increase the heat transfer surface area. A twin wire-arc thermal spraying system can generate a dense, high strength aluminum coating to connect wires and aluminum tube. Tiled and clamped connections between the wire mesh and tube were applied to obtain an efficient heat exchanger. The heat transfer characteristics for plain tube, three sprayed tube-wire and six sprayed wire-meshes (SPW) heat exchangers were experimentally tested. Also, heat exchanger surface temperatures were measured using infrared camera. Ideal fin model was applied after validation using data of sprayed tube-wire heat exchangers. The tube inlet temperature ranged from 100 to 200 °C and the wind tunnel air velocity was from 2 to 20 m/s. The results indicate that all the SPW heat exchangers can enhance the heat transfer compared with plain tube heat exchanger. Tube outside Nusselt number was fitted with Reynolds number and wire mesh porosity. 20PPI clamped SPW was suggested to be used in the future design of compact heat exchangers due to the maximum 76.7% equivalent efficiency compared with ideal fin model.