Flat flexible polymer heat pipes

Flat, flexible, lightweight, polymer heat pipes (FPHP) were fabricated. The overall geometry of the heat pipe was 130 mm x 70 mm x 1.31 mm. A commercially available low-cost film composed of laminated sheets of low-density polyethylene terephthalate, aluminum and polyethylene layers was used as the casing. A triple-layer sintered copper woven mesh served as a liquid wicking structure, and water was the working fluid. A coarse nylon woven mesh provided space for vapor transport and mechanical rigidity. Thermal power ranging from 5 to 30 W was supplied to the evaporator while the device was flexed at 0 degrees, 45 degrees and 90 degrees. The thermal resistance of the FPHP ranged from 1.2 to 3.0 K W-1 depending on the operating conditions while the thermal resistance for a similar-sized solid copper reference was a constant at 4.6 K W-1. With 25 W power input, the thermal resistance of the liquid-vapor core of the FPHP was 23% of a copper reference sample with identical laminated polymer material. This work shows a promising combination of technologies that has the potential to usher in a new generation of highly flexible, lightweight, low-cost, high-performance thermal management solutions.