Experimental investigation of combined forced and free convection in horizontal and inclined tubes

The effects of free convection on the laminar flow of water through a circular duct are investigated. Boundary conditions are for essentially constant heat transfer rate longitudinally, and circumferentially uniform wall temperature. The effects of the Reynolds ana Rayleigh numbers on heat transfer are investigated for both horizontal and inclined orientations. The experiment covers the range 200-2300 for the inlet RE-number, and 6,000-70,000 for Ra. The effects of pipe inclination are investigated for the slope angle values over the horizontal ranging between 0° and 60°, with laminar ascending flow.