New water-stainless steel rod-plate heat pipe: model and experiments

Abstract

This work proposes a novel flat heat pipe technology, namely the rod-plate heat pipe, formed by the diffusion bonding of a set of parallel rods, of around 8 mm diameter, between flat plates of approximately 500 × 60 × 2 mm³. This design is inspired by the mini wire-plate heat pipe concept. This work is the first in the literature to apply this technology to large size heat pipes. A theoretical model is devised and used to predict the fluid distribution along the heat pipe, detect regions of flooding and dry-out and determine the best charging volume. Experiments are performed with a stainless-steel device operating in horizontal orientation with water as working fluid. Electrical cartridge resistances play the role of the evaporator heat source, while the condenser is cooled by either natural convection and radiation or heat exchangers linked to a thermal bath. For the experiments using a device with an exposed condenser, the minimum thermal resistance is 0.147 °C/W, for 88.50 W for heat input. The operation temperature increases with heat input up to 326.56 °C for a heat load of 191.40 W. The thermal resistances of the heat pipe cooled by heat exchangers have a minimum of 0.123 °C/W at 171.57 W heat transport rate, for a 40 °C thermal bath temperature. The theoretical results and data obtained so far corroborate the feasibility of this technology, with devices able to transfer up to 22.18 W per groove.