Experimental Investigation of a Porous Evaporator for a Heat Pipe-Based DEMO Divertor Target Concept

Heat pipes can effectively transport heat from a heat source to a heat sink by means of phase transitions of the working fluid inside and capillary forces. Because of their high effective conductivity, they are under consideration for the DEMO in-vessel plasma-facing components. With proper condenser length, heat pipes can enlarge the heat transfer area to the cooling circuit, thus relaxing the requirements for the cooling circuit. The reduced fluid inventory of the heat pipe would also limit the amount of liquid released in case of damage or accidents compared to an actively cooled plasma-facing component, thus increasing the reactor’s safety. Recent engineering studies indicate that it is possible to design a water-based heat pipe with mixed capillary structures (axial grooves at the condenser and adiabatic zones and sintered porous material at the evaporator) that would have a capillary driving force large enough to transport an amount of heat corresponding to an applied heat flux of 20 MW/m 2 . However, to validate the design for such high heat fluxes, the capability of the evaporator to withstand such loads should be investigated first. ... mehrHence, a dedicated experiment focusing on the performance of the proposed heat pipe evaporator was designed. The experimental results show the operating characteristics of two different evaporator designs: one with a porous structure and one with channels on the porous surface. The influence of liquid inventory and heat sink flow rates on the heat pipe performance are also discussed here.