Combined Convection Heat Transfer to Thermally Developing Air Flow inside a Circular Inclined Cylinder

Abstract

Heat transfer by mixed convection to a hydro dynamically developed airflow from the inside surface of inclined circular cylinder subjected to a constant heat flux investigated experimentally. An experimental test rig has a test section with 500 mm length and 46 mm inside diameter aluminum cylinder (L/D = 10.87) proceeds with 1100 mm calming section having a Teflon bell mouth piece at its inlet to adopt a fully developed flow hydrodynamically at the test section inlet. The experiments covered Reynolds number ranged between 350 to 850, heat flux varies between 100 w/m 2 to 700 w/m 2 and cylinder orientation varies between 0˚ (horizontal) to 90˚ in the assistant mixed convection situations and -20˚ in the opposite mixed convection situation. The surface temperature distributions have general shape which increases with the increasing heat flux rate and decreasing Reynolds number. The local and average heat transfer coefficient results demonstrate that the local heat transfer coefficient represents the axial position at which can accept a fully developed flow thermally. The average heat transfer coefficient result of the horizontal tcylinder shows a reduction in heat transfer coefficient as heat flux increases. The results also show average Nusselt number variation with axial dimensionless distance Z + . For five angles of inclinations, correlation equations between average number and ZZ parameter have been delivered. Another five correlation equation between average Nusselt number and ZZq Parameter based on the modified Grashof Nussult number also have been introduced.A comparison with previous work shows an agreement in the heat transfer trends for the horizontal and inclined opposing mixed convection situations.