A comprehensive three-dimensional numerical model is developed to evaluate the effect of bending on water-copper cylindrical heat pipes. This model distinguishes itself from other models by its ability to uniquely determine the operating pressure of the heat pipe based on the operating and physical conditions. The effects of one 90-degree bend and two 90-degree bends are evaluated on the performance of a heat pipe. Two types of wicks are considered: a screen mesh wick and a sintered powder wick. The obtained results show that bending does affect the vapor pressure drop; however, the changes are not significant when compared to the operating pressure of the heat pipe. If the bending is performed in a manner where the wick is not damaged and the liquid is not blocked from returning to the evaporator, the performance of the heat pipe will not be affected significantly. In addition, if the heat pipe is operating in the horizontal direction, where both evaporator and condenser legs are at the same level, bending does not affect the liquid pressure drop significantly; however, the screen mesh does provide a higher capillary limit. The results also showed that the effects of gravity can be important when bending heat pipes and consideration should be given for this factor. When the bent heat pipe works against gravity, the sintered powder wick heat pipes showed higher capillary limits.

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