Heat Transfer Study for ADS Solid Target: Surface Wettability and Its Effect on a Boiling Heat Transfer

Abstract

In relationship to a solid target cooling system of an accelerator-driven system (ADS), wettability effect on boiling heat transfer has been experimentally investigated by irradiation with ultraviolet and gamma rays (γ-rays). The experimental apparatus consists of a copper heater block, a rectangular container, and a thermostat bath. Two copper heater blocks were fabricated: one is for radiationinduced surface activation (RISA) and the other is for photoelectric reaction by ultraviolet whose heat transfer surface is coated by a TiO 2 film. These copper heater blocks were irradiated by ultraviolet or by γ-rays to change the surface wettability. Boiling heat transfer under subcooling conditions was measured before and after the irradiations to study the wettability effect. Experimental results show that nucleate boiling curves are shifted to the higher wall superheated side with the irradiated surface because of the decrease of the active nucleation sites. Heat transfer enhancement was found in both the critical heat flux and microbubble emission boiling (MEB) regions under these experimental conditions.

Spatial–temporal thermal‐fluid behaviors of microbubble emission boiling (MEB)

“…Columns (a) and (b) indicate the temporal variation of q ′ and the “pseudo‐” boiling curve, respectively. Note again that the vertical axes for both of (a) and (b) express the “quasi‐” heat flux; this q ′ corresponds to the transient heat flux obtained from the temperature in transient condition in the rod 11 . The pseudo‐boiling curves in column (b) are illustrated by plotting all data of q ′ against the wall superheat for any instant.…”

“…Effect of Δ T sub on the heat transfer characteristics were examined intensively 5‐9 . Not only the effect of the temperature of the bulk liquid, but also the characteristics of the heated surfaces and the geometries has been discussed; such as their wettability 10,11 and shape and/or size (on squared surface 10 ; in micro/mini channels 12,13 ; on wires 12,14 ).…”