An Experimental Investigation of Hybrid Oscillating Heat Pipe

Abstract

A novel oscillating heat pipe (OHP) has been constructed and experimentally investigated featuring a meandering channel formed entirely by a wicking structure. The hybrid approach utilizes the wicking structure found in traditional heat pipes, while also utilizing the meandering channels and plug flow of OHPs. Water and acetone were both tested with acetone demonstrating higher peak performance and water demonstrating a wider operating range. While OHPs typically require a high startup power, the hybrid approach presented achieves startup at very low power input and demonstrates a significant improvement in performance over the same device without any working fluid.

An investigation of a multi-layered oscillating heat pipe additively manufactured from Ti-6Al-4V powder

“…The benefit/cost of having PBF-sourced, partially-sintered channel structures within an OHP, or any other heat transfer device, will depend on its operating conditions/application. For the case of OHPs, the roughened surfaces can decrease the start-up power threshold of the OHP (due to boiling enhancements and secondary capillary action) while decreasing its power limit (since pressure balancing within the evaporator becomes easier to obtain during operation) [12,46,50,51]. However, if these characteristics were not needed or even undesirable for a certain application, methods such as purging the channels with an acidic solution to etch the sintered particles could be an option for reducing channel roughness.…”

“…The TGP is a surfacemounted, two-phase heat spreader that operates passively [3,6,7]; relying on capillary structures such as porous/sintered media and mini/micro-channels for cyclic fluid pumping. Some examples of TGPs include flat heat pipes, vapor chambers, oscillating (or pulsating) heat pipes (OHPs) and other hybrid two-phase cooling technologies [5,[8][9][10][11][12]. The mounting of a TGP typically requires that minimal stress occurs at the source-contacting interface to ensure minimal damage to heatdissipating electronics.…”

“…Although external surfaces of PBF parts can be readily machined for reducing surface roughness, internal surfaces (especially with capillary dimension) are more challenging to post process. Hence, the internal surface quality and topology of the ML-OHP channel structure is worth investigating, as such features can generally impact a fluid's wetting/wicking behavior and heat transfer in an OHP[12,45,46]. For instance, the thin film evaporation, a dominant heat transfer mechanism in the OHP evaporator, as well as the fluid pulsation and convection/condensation, throughout the OHP, depend on the fluid-to-wall wetting behavior (e.g.…”

Additive manufacturing of heat exchangers: A case study on a multi-layered Ti–6Al–4V oscillating heat pipe

“…It appears that the surface quality of the walls is gravity dependent and thus affected by the orientation of the part relative to the build plane during SLM. The observed, sintered surface quality of the internal channels may serve as secondary capillary structures -allowing for decreased OHP start-up power and the increased probability of pressure balancing between channel sections [78]. The A c c e p t e d M a n u s c r i p t 24 sintered surface condition can also be advantageous for heat transfer between the wall and the adjoining liquid -increasing the surface area for thin film evaporation [31,79].…”

Flat-Plate PHP with Gravity-Independent Performance and High Maximum Thermal Load

“…The PHP thermal resistance remained nearly independent of gravity and even slightly decreased at 10 g. A novel "hybrid" type of PHP was presented in ref. [30]. In this PHP, the meandering channel (hydraulic diameter of 0.79 mm, acetone and water as a working fluid with filling ratios between 28 and 82%) was formed entirely by a wicking structure instead of the usual solid walls.…”