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Research Papers: Evaporation, Boiling, and Condensation

Subcooled Pool Boiling in Variable Gravity Environments

[+] Author and Article Information
Rishi Raj

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742rraj@umd.edu

Jungho Kim1

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742kimjh@umd.edu

John McQuillen

 NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135john.b.mcquillen@nasa.gov

1

Corresponding author.

J. Heat Transfer 131(9), 091502 (Jun 25, 2009) (10 pages) doi:10.1115/1.3122782 History: Received October 09, 2008; Revised March 16, 2009; Published June 25, 2009

Virtually all data to date regarding parametric effects of gravity on pool boiling have been inferred from experiments performed in low-g, 1g, or 1.8g conditions. The current work is based on observations of boiling heat transfer obtained over a continuous range of gravity levels (0g1.8g) under subcooled liquid conditions (n-perfluorohexane, ΔTsub=26°C, and 1 atm), two gas concentrations (220 ppm and 1216 ppm), and three heater sizes (full heater-7×7mm2, half heater-7×3.5mm2, and quarter heater-3.5×3.5mm2). As the gravity level changed, a sharp transition in the heat transfer mechanism was observed at a threshold gravity level. Below this threshold (low-g regime), a nondeparting primary bubble governed the heat transfer and the effect of residual gravity was small. Above this threshold (high-g regime), bubble growth and departure dominated the heat transfer and gravity effects became more important. An increase in noncondensable dissolved gas concentration shifted the threshold gravity level to lower accelerations. Heat flux was found to be heater size dependent only in the low-g regime.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the trajectory of the parabolic flight with corresponding acceleration levels

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Figure 2

The schematic of the heat transfer contributions for the natural convection (left) and forced convection (right) cases

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Figure 3

Heat flux versus acceleration during transition for (a) ΔTw=9°C and (b) ΔTw=44°C, full heater (96 elements)

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Figure 4

Plot of heat flux versus acceleration for high gas case (cg∼1216 ppm), full heater (96 elements), at ΔTw=44°C, with superimposed bottom view images at 0.01g, 0.3g, 0.85g, and 1.68g

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Figure 5

Plot of heat flux versus acceleration for the high gas case (cg∼1216 ppm), full heater (96 elements) for ΔTw (a) 24°C, (b) 29°C, (c) 34°C, and (d) 39°C

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Figure 6

A plot of the slope m (Eq. 4) in low-g and high-g regime

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Figure 7

Comparison between the values of adepart obtained from the Fritz correlation and experiment

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Figure 8

Boiling curve at different gravity levels for high gas (cg∼1216 ppm), full heater (96 elements), with superimposed bottom view images for 1.7g and 0.1g at different temperatures

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Figure 9

Plot of heat flux versus acceleration for low gas case (cg∼220 ppm), full heater (96 elements), at ΔTw=44°C, and with superimposed bottom view images at 0.01g, 0.28g, 0.74g, and 1.71g

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Figure 10

(a) Boiling curve at three accelerations for low and high gas, (b) heat flux versus acceleration in at ΔTw=29°C, for two dissolved gas concentrations, full heater (96 elements)

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Figure 11

A schematic of the bubble size and apparent contact angle for the two gas concentrations in the low-g regime

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Figure 12

Comparison between the values of adepart obtained from the Fritz correlation and experiment (low gas)

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Figure 13

Boiling curve for three different heater sizes, high gas (cg∼1216 ppm) at (a) 1.7g and (b) 1g, (c) 0.3g, and (d) 0.05g

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