An experimental rotating wickless heat pipe apparatus was designed and machined. The apparatus includes a rotating heat pipe assembly, test stand, spray cooling assembly, safety shielding, and instrumentation. A revised condensing limit for the operation of the rotating heat pipe was obtained by modifying Ballback's Nusselt film condensation theory to include the effects of a thermal resistance in the condenser wall and in the condenser outside surface cooling mechanism. Approximate results, obtained for half-cone angles of 1, 2, and 3 degrees, show that less heat can be removed than originally predicted by Ballback, and that the outside heat transfer coefficient can significantly alter the condensing limit. An improved Nusselt theory was developed which applies for all half-cone angles, and which includes the effects of the thermal resistances in the condenser wall and in the condenser outside surface cooling mechanism. This formulation led to a second-order non-linear differential equation for the film thickness which was numerically integrated using a free-overfall boundary condition at the condenser exit. Results obtained for a half-cone angle of 0 degrees are substantially less than the results obtained from the approximate solution for half-cone angles of 1, 2, and 3 degrees. (Author)
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