THE EFFECT OF BENDING ON SINTERED WICKED HEAT PIPES FOR MULTIPLE COMPONENT COOLING

This study details an experimental investigation into the degenerative effects of bending on a sintered wicked copper-water heat pipe for multiple-component cooling. The aim of this study was to provide empirical data that could be employed to estimate the performance of heat pipes within complex space-constrained systems where it is necessary that a heat pipe be bent to cool multiple components. To this end, the performance of a 400 mm long, 6 mm diameter sintered wicked copper-water heat pipe was investigated for both singular and double bend configurations. Bend angles were limited to 0-90°, and bend locations were confined to two points. Results show that the evaporators closest to the condenser were unaffected by bending and that changes were only observable in the final evaporator. As such, thermal resistance values for each discrete evaporator were observed. When the heat pipe was bent from 0-90°, thermal resistance of the final evaporator increased by 15-126% while the other evaporators remained unchanged. It was also found that bending within the first adiabatic region had a much greater effect (8-26%) on performance than the addition of a bend further along the heat pipe. These results indicate that the vapour pressure drop induced by bending is minimal when thermal loads are relatively low and resulting vapour velocities are small. It is therefore postulated that exceeding the capillary limit, which causes localised dry out of the wick structure, is the main contributor to performance degradation. Furthermore, it is speculated that the effects of bend location are due to axial variance in both vapour and liquid mass flow rates within a heat pipe during operation. Both of which reach a maximum within the adiabatic region; therefore, it is inferred that pressure losses due to deformation of the vapour channel and wick structure within this region would be of a greater magnitude.