Capillary performance analysis of copper powder-fiber composite wick for ultra-thin heat pipe

Excellent ultra-thin heat pipes (UTHP) require a wick with high capillary force (Delta P-c) and a good permeability performance (K). In this work, a copper powder-fiber composite wick was fabricated by sintering of the copper powder and fiber mixture. Effects of the copper powder particle size, copper powder volume ratio, as well as the super-hydrophilic treatment were investigated, and the results indicate that the copper powder volume ratio is the most significant factor by orthogonal experiments. Moreover, sensitivity analysis shows that super-hydrophilic treatment contributes the lower capillary force and higher permeability, except when copper powder particle size is high to 80 mesh and powder ratio is low to 20%. Interestingly, the overall capillary performance (Delta P-c center dot K) of the super-hydrophilic treated wicks is significantly improved. Besides, for the super-hydrophilic treated wicks, both the smaller copper powder particle size and volume ratio contribute the higher permeability and better comprehensive performance, even though a worse capillary force.