Experimental investigation on the local heat transfer with a circular jet impinging on a metal foamed flat plate

• Published in: International journal of heat and mass transfer 2020-12, Vol.162, p.120405, Article 120405
• Main Authors: Yogi, Ketan, Godase, Mayur Manik, Shetty, Mikhil, Krishnan, Shankar, Prabhu, S.V.
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air jets; Aluminum; Augmentation; Circular jet; Density; Diameters; Flat plates; Fluid flow; Foamed metals; Heat transfer; Heat transfer coefficients; Infrared cameras; Jet impingement; Local heat transfer; Metal foam; Metal foam pore density; Metal foams; Metal foils; Nozzles; Nusselt number; Porosity; Reynolds number; Stagnation point; Temperature distribution; Thickness; Thin metal foil technique; Viscosity
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2020.120405

•Air jet is made to impinge on metal foamed flat plate.•Effect of Re, z/d and PPI on Nu is investigated for air jet.•Metal foamed flat plate enhance heat transfer performance compared to flat plate.•10 PPI metal foam perform better than 20 PPI and 40 PPI metal foam.•Region wise correlations for Nu are developed for metal foamed flat plate. The present study is concerned with an experimental investigation of the local heat transfer coefficient for an air jet impinging on a metal foamed flat plate having different pore densities using a thin metal foil technique. The augmentation of heat transfer caused by the metal foams in comparison with heat transfer on a flat plate is quantified. The experiments are performed to measure the temperature distribution of the metal foamed flat plate with the help of an infrared themal camera. Alunumium metal foams having 8 mm thickness and pore densities of 10, 20 and 40 pores per inch (PPI) are studied. The porosity and thickness of the each aluminum metal foam is 92 %. The range of the Reynolds number (based on the nozzle diameter) covered in the study is 10000 to 25000 and the nozzle to plate spacing varied from 2 to 10 nozzle diameter. The local Nusselt number is highest at the stagnation region, and it decreases in the radial direction away from the stagnation point. Metal foamed flat plate enhances the heat transfer performance compared to a smooth flat plate irrespective of metal foam pore density (pores per inch). The stagnation Nusselt number and average Nusselt number for the metal foamed flat plate is consistently higher compared to the smooth flat plate. A metal foamed flat plate with a pore density of 10 PPI results in higher augmentation of the stagnation and average Nusselt number compared to metal foamed flat plates with a pore density of 20 and 40 PPI. Metal foamed flat plate shows little decrement in the stagnation Nusselt number with an increase in the nozzle to plate spacing irrespective of the pore density. The average Nusselt number seems to be insensitive to the nozzle to plate spacing. Region wise semi-empirical correlations of the local Nusselt number based on the Reynolds number (Re), non-dimensional radial distance (r/d) and non-diamnesional nozzle to plate spacing (r/d) are proposed.