A steady state heat pipe model, capable of calculating temperature and pressure distributions in the working fluid of a rotating heat pipe, is described here. The model can predict the performance of rotating heat pipes with a round cross-section, containing an annular gap composite wick structure. In addition to straight heat pipes, with a longitudinal axis that may or may not coincide with the axis of rotation, the model also allows for simulation of bent heat pipes. Using this model, results are generated for a bent heat pipe proposed for use in cooling rotating machinery. For the bent heat pipe, the condenser and adiabatic sections coincide with the axis of rotation, while the evaporator consists of an off-axis eccentrically rotating component, and a bend that allows for portion of the evaporator to be nearly perpendicular to the axis of rotation. The presence of the composite wick allows for heat pipe operation in both the rotating and stationary operating modes. Model results for the stationary operating mode compare favorably to the steady state heat pipe analysis code HTPIPE [1]. These comparisons for the stationary operating limit are significant, since HTPIPE has been benchmarked against experimental heat pipe data for nearly 30 years. As the rotational speed is increased, the rotation induced forces are used to drive the liquid flow to the evaporator. At high rotation rates, the liquid recedes from the wick, and forms a thin layer against the inside wall of the heat pipe. The results show that when a stable liquid layer is formed against the wall of the pipe, the shear stress opposes the rotation induced forces acting on the liquid, and limits the magnitude of the pressure and temperature rises in the working fluid (from the values predicted using a hydrostatic approximation).

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