In order to enhance the heat transfer performance

an experimental study on the pool boiling heat transfer was conducted at three different degrees of subcooling(15

25

35 K)for different staggered micro-pin-finned surfaces of silicon chips in FC-72

and smooth surface was also tested for comparison. The dimensions of the silicon chips were 10 mm×10 mm×0.5 mm(length×width×thickness)

and the micro-pin-finned silicon surfaces were fabricated by dry etching technique. Three center-to-center spacings

(45

60

75 μm)were chosen for two kinds of square micro pin-fins of 30 μm×60 μm and 30 μm×120 μm(width×height). One center-to-center spacing of 60 μm was chosen for two different circular micro pin-fins of 38 μm×60 μm and 38 μm×120 μm(diameter×height). The center-to-center spacing of fins was found to have significant effects on the boiling heat transfer coefficient and critical heat flux

but the influence was not monotonous. In nuclear boiling

the surface with the center-to-center spacing of 45 μm showed the highest heat transfer coefficient than other surface with the same fin height. The surface with the center-to-center spacing of 60 μm showed the highest critical heat flux(54.6 W/cm

2

)for the surfaces with a fin height of 60 μm

while the surface with the center-to-center spacing of 75 μm showed the highest critical heat flux(60.72 W/cm

2

)for the surfaces with a fin height of 120 μm. When the ratio of center-to-center spacing to thickness was greater than or equal to 2

the center-to-center spacing had slight effect on critical heat flux

and the difference was 2% at most. However

when the ratio was less than 2

the difference reached up to 14%. Compared with square pin-fins

circular pin-fins showed better heat transfer performance under the same surface area

and the critical heat flux was increased by 13% and 124% for square micro-pin-finned surface and smooth surface respectively. Besides

the critical heat flux was increased with the degree of subcooling

and the onset of nucleate boiling was delayed.