Investigations on the effects of heater surface characteristics on the bubble waiting period during nucleate boiling at low subcooling

D Sarker, W Ding, R Franz, O Varlamova… - … Thermal and Fluid …, 2019 - Elsevier
D Sarker, W Ding, R Franz, O Varlamova, P Kovats, K Zähringer, U Hampel
Experimental Thermal and Fluid Science, 2019Elsevier
In nucleate boiling the 'bubble waiting period', that is, the time duration between the
departure of a grown bubble and the start of the formation of a new bubble from a cavity,
plays a crucial role for the total heat transfer. Experiments were performed to study the
influence of the heater surface characteristics on this parameter. A femtosecond pulsed laser
was used to produce nano-and micro-patterned surfaces with roughness in the range of
micrometers on stainless steel heater surfaces. Boiling experiments were conducted on a …
Abstract
In nucleate boiling the ‘bubble waiting period’, that is, the time duration between the departure of a grown bubble and the start of the formation of a new bubble from a cavity, plays a crucial role for the total heat transfer. Experiments were performed to study the influence of the heater surface characteristics on this parameter. A femtosecond pulsed laser was used to produce nano- and micro-patterned surfaces with roughness in the range of micrometers on stainless steel heater surfaces. Boiling experiments were conducted on a vertically oriented heater at atmospheric pressure and with degassed deionized water. Bubble generation, departure, sliding, detachment and inception of the next bubble have been recorded by high-resolution optical shadowgraphy. Bubble waiting periods were found to be longer for low-wettability smooth and rough surfaces. High-wettability rough surfaces showed a shorter bubble waiting period. The shortest (approximately 3 ms) and the longest (approximately 30 ms) bubble waiting periods were found for well-wetting surfaces with Sq = 0.18 µm and for low-wetting surfaces with 0.12 µm, respectively. These corresponding roughness heights are denoted as ‘optimal roughness heights’.
Elsevier
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