Experimental study of boiling phenomena and heat transfer performances of FC-72 over micro-pin-finned silicon chips

Experimental study of nucleate pool boiling of FC-72 on micro-pin-finned surface under microgravity

“…Moreover, the boiling curve of chip PF30-60 is very steep and the wall superheat shows a very small change with further increasing to the high heat flux region. This phenomenon was also observed by Honda et al [23] and Wei et al [10].…”

“…According to our previous studies [8][9][10][11][12], the fin size of 30-50 lm appears to be a preferable size for the design of micro-pin-finned surfaces in the enhancement of nucleate boiling heat transfer. Following the enhanced boiling heat transfer mechanisms for the micro-pin-finned surfaces, it is supposed that although the bubbles staying on the top of the micro-pin-fins cannot detach soon in microgravity, the fresh bulk liquid may still access to the heater surface through interconnect tunnels formed by the micro-pin-fins due to the capillary forces, which is independent of the gravity level.…”

“…3; the lower column in the figure shows a close-up of micro-pin-fins. Detailed description about the properties of the test chips were reported in our previous paper [10]. The chip was Joule heated by a direct current or voltage.…”

“…The deterioration of these surfaces performance is caused by a large number of mushroom bubbles staying above the surface microstructure, which prevented the bulk liquid from contacting the superheated wall for vaporization. Since 2002, Honda and Wei [8][9][10][11][12] have made a series of experimental study on boiling heat transfer enhancement by use of micro-pin-fins lm in thickness and 60-200 lm in height) which were fabricated by dry etching. From the boiling incipience to the critical heat flux, the micro-pin-finned surfaces showed a sharp increase in the heat flux with increasing wall superheat.…”

Bubble dynamics in nucleate pool boiling on micro-pin-finned surfaces in microgravity

“…At high heat fluxes, although the large coalesced bubble can also depart from the heater surface and the wall temperature is a little bit higher than that in normal gravity, it indicates that boiling heat transfer in microgravity is deteriorated as compared with that in normal gravity. Compared with the smooth surface, pool boiling heat transfer over micro-pin-finned surfaces has a lot of advantages including increase in heat transfer area and reduction of thermal resistance, and thus improving the heat transfer coefficient and CHF in terrestrial experiments in our previous study [22]. In the high heat flux region, although the micro-pin-finned surfaces are covered with large bubbles, the capillary force generated by the bubbles drives plenty of fresh liquid into contact with the superheated wall for vaporization through the regular interconnected structures, as well as improves the micro-convective heat transfer by the motion of liquid around the micro-pin-fins.…”