A wicked heat pipe fabricated using metal additive manufacturing

Abstract

Additive Manufacturing (AM) has emerged as a high-potential manufacturing technology for fabricating all-in-one heat exchange devices that incorporate embedded two-phase heat transport and spreading systems. A key enabler of this technology is the capacity for AM to fabricate porous wick structures. To this end, this work experimentally investigates a simple AM-fabricated aluminum structure with an inner cavity. Within the cavity, a single-sided wick heat pipe is fabricated, again by aluminum AM. To facilitate capillary wicking within the embedded heat pipe, while being amenable to the direct metal laser sintering (DMLS) AM process, a novel cross-hatched porous wick structure is introduced. The wicks were fabricated by printing layered rows of fine wire-like features at different angles to one another in successive layers, creating a porous 3D structure. The resulting 3D wick structure was varied by controlling the hatch distance between neighboring printed wires in each layer, resulting in different wick properties. In this investigation, the capillary performance of three wicks were interrogated using the Rate of Rise technique, which also facilitated estimation of important wick properties such as permeability and effective pore radius. By varying the hatch distance between 0.6 mm and 1.0 mm, the permeability ranged between 35.6 and 39.6μm2 with a corresponding range of 127–88 μm for the effective pore radius and 43–59% for the porosity. The efficacy of the proposed metal AM heat pipe concept was then verified by enclosing the wicks within a lid casing, creating two-part flat heat pipes, and experimentally characterizing them with acetone used as the working fluid. This study includes performance indicators such as overall thermal resistance, effective wick thermal conductivity, and effective thermal conductivity of the heat pipe cavity region.

Keywords

• Heat pipe
• Additive manufacturing
• Porous wicks
• Capillary structure