Sub-Channels-Inserted Porous Evaporator for Efficient Divertor Cooling

A sub-channels-inserted porous evaporator is proposed as a heat removal device of the divertor with a heat load exceeding 10 MW/m². The porous medium is made by sintering copper particles of micro size in diameter and has several sub-channels to enhance discharge of generated vapor outside the porous medium. This porous cooling devise is attached onto the backside of the divertor and remove the heat by evaporating water passing through the porous medium against the heat flow. In order to prove the effect of the sub-channels, the heat transfer characteristics of this porous device are evaluated experimentally using a plasma arcjet as a high heat flux source. The result shows that the heat transfer performance of copper-particles-sintered porous medium with the sub-channels enables to remove much higher heat flux under lower flow rate and lower wall superheat conditions, compared with the normal porous media. The removal heat flux, 8.1 MW/m², is 1.8 times as higher than that of the normal porous medium at a wall superheat of 50 degrees (the heat transfer coefficient, 1.6 × 10⁵ W/m²/K, is 2.4 times as higher). The removal heat flux reaches almost 10 MW/m² although the wall superheat exceeds 100 degrees (The wall temperature is approximately 220 degrees C. still in a fully developed boiling regime). In addition, the removal heat flux exceeds 20 MW/m² by increasing the number of the sub-channels under lower wall superheat conditions, which proves high potential of the sub-channels-inserted porous evaporator.