Question

Engine oil at 100°C and a velocity of 0.1 m/s flows over both surfaces of a 1-m flat plate which is maintained at 20°C. Determine: The velocity and thermal boundary layer thicknesses at the trailing edge of the plate The local heat flux and surface shear stress at the trailing edge The total drag force and rate of heat transfer per unit width of the plate Plot the velocity boundary layer thickness and local values of the surface shear stress, convection coefficient, and heat flux as functions of x for 0 s x S 1 m. a. b. c. d.

Start by checking your Reynolds number (Re) at the end of the plate, where it will be at a maximum. This will determine if your boundary layer is simply laminar along the length of the plate or if it becomes turbulent (the "mixed BL" condition). Once you know the conditions of the flow, you can solve for the velocity BL thickness directly with an equation from the list of external flow correlations (posted). Your properties should be looked up at the film temperature. Use the determined flow correlations to determine the LOCAL transfer coefficient, the shear and force (from the skin friction coefficient, C_f) and the heat flux. Don't forget that BOTH sides of the flat plate are exposed to the flow. You should find the heat flux at the trailing edge to be about 1300 W/m^2, and the total heat transfer from the plate to be about 5200 W. Plot the functions, which are only functions of x, in a software and print them.

Answer 1

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