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Gravity scaling parameter for pool boiling heat transfer / Rishi Raj in Journal of heat transfer, Vol. 132 N° 9 (Septembre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 9 (Septembre 2010) . - pp. [091502-1/9] Titre : Gravity scaling parameter for pool boiling heat transfer Type de document : texte imprimé Auteurs : Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur Article en page(s) : pp. [091502-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Scaling  parameter  Variable  gravity  Pool  boiling  Microgravity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Although the effects of microgravity, earth gravity, and hypergravity (>1.5 g) on pool boiling heat flux have been studied previously, pool boiling heat flux data over a continuous range of gravity levels (0–1.7 g) was unavailable until recently. The current work uses the results of a variable gravity, subcooled pool boiling experiment to develop a gravity scaling parameter for n-perfluorohexane/FC-72 in the buoyancy-dominated boiling regime (Lh/Lc>2.1). The heat flux prediction was then validated using heat flux data at different subcoolings and dissolved gas concentrations. The scaling parameter can be used as a tool to predict boiling heat flux at any gravity level in the buoyancy dominated regime if the data under similar experimental conditions are available at any other gravity level. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Gravity scaling parameter for pool boiling heat transfer [texte imprimé] / Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur . - pp. [091502-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 9 (Septembre 2010) . - pp. [091502-1/9] Mots-clés : Scaling  parameter  Variable  gravity  Pool  boiling  Microgravity Index. décimale : 536 Chaleur. Thermodynamique Résumé : Although the effects of microgravity, earth gravity, and hypergravity (>1.5 g) on pool boiling heat flux have been studied previously, pool boiling heat flux data over a continuous range of gravity levels (0–1.7 g) was unavailable until recently. The current work uses the results of a variable gravity, subcooled pool boiling experiment to develop a gravity scaling parameter for n-perfluorohexane/FC-72 in the buoyancy-dominated boiling regime (Lh/Lc>2.1). The heat flux prediction was then validated using heat flux data at different subcoolings and dissolved gas concentrations. The scaling parameter can be used as a tool to predict boiling heat flux at any gravity level in the buoyancy dominated regime if the data under similar experimental conditions are available at any other gravity level. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Heater size and gravity based pool boiling regime map / Rishi Raj in Journal of heat transfer, Vol. 132 N° 9 (Septembre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 9 (Septembre 2010) . - pp. [091503-1/10] Titre : Heater size and gravity based pool boiling regime map : transition criteria between buoyancy and surface tension dominated boiling Type de document : texte imprimé Auteurs : Rishi Raj, Auteur ; Jungho Kim, Auteur Article en page(s) : pp. [091503-1/10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Pool  boiling  Capillary  length  Heater  size  Gravity  Surface  tension  Buoyancy  Regime  map Index. décimale : 536 Chaleur. Thermodynamique Résumé : A pool boiling regime map demarcating the boundary between the surface tension and buoyancy dominated boiling regimes is developed based on heater size and gravity. For large heaters and/or high gravity conditions, boiling is dominated by buoyancy, and the ebullition cycle dominates the contribution to heat transfer. As the gravity level and/or heater size is decreased, surface tension forces become increasingly dominant, and a decrease in heat transfer is observed. The ratio of the heater size Lh (length of a side for a square heater) to the capillary length Lc is found to be a suitable parameter to define the transition criterion between these regimes. Based on the data obtained using FC-72 and pentane, the threshold value of Lh/Lc above which pool boiling is buoyancy dominated was found to be about 2.1. This transition criterion was found to be the same for gravity levels between ~0g–1.7g and liquid subcoolings between 6.6°C and 26.6°C. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Heater size and gravity based pool boiling regime map : transition criteria between buoyancy and surface tension dominated boiling [texte imprimé] / Rishi Raj, Auteur ; Jungho Kim, Auteur . - pp. [091503-1/10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 9 (Septembre 2010) . - pp. [091503-1/10] Mots-clés : Pool  boiling  Capillary  length  Heater  size  Gravity  Surface  tension  Buoyancy  Regime  map Index. décimale : 536 Chaleur. Thermodynamique Résumé : A pool boiling regime map demarcating the boundary between the surface tension and buoyancy dominated boiling regimes is developed based on heater size and gravity. For large heaters and/or high gravity conditions, boiling is dominated by buoyancy, and the ebullition cycle dominates the contribution to heat transfer. As the gravity level and/or heater size is decreased, surface tension forces become increasingly dominant, and a decrease in heat transfer is observed. The ratio of the heater size Lh (length of a side for a square heater) to the capillary length Lc is found to be a suitable parameter to define the transition criterion between these regimes. Based on the data obtained using FC-72 and pentane, the threshold value of Lh/Lc above which pool boiling is buoyancy dominated was found to be about 2.1. This transition criterion was found to be the same for gravity levels between ~0g–1.7g and liquid subcoolings between 6.6°C and 26.6°C. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size / Rishi Raj in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 13 p. Titre : On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size Type de document : texte imprimé Auteurs : Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Boiling  Heat  transfer  Surface  tension  Zero  gravity  experiments Index. décimale : 536 Chaleur. Thermodynamique Résumé : A framework for scaling pool boiling heat flux is developed using data from various heater sizes over a range of gravity levels. Boiling is buoyancy dominated for large heaters and/or high gravity conditions and the heat flux is heater size independent. The power law coefficient for gravity is a function of wall temperature. As the heater size or gravity level is reduced, a sharp transition in the heat flux is observed at a threshold value of Lh/Lc = 2.1. Below this threshold value, boiling is surface tension dominated and the dependence on gravity is smaller. The gravity scaling parameter for the heat flux in the buoyancy dominated boiling regime developed in the previous work is updated to account for subcooling effect. Based on this scaling parameter and the transition criteria, a methodology for predicting heat flux in the surface tension dominated boiling regime, typically observed under low-gravity conditions, is developed. Given the heat flux at a reference gravity level and heater size, the current framework allows the prediction of heat flux at any other gravity level and/or heater size under similar experimental conditions. The prediction is validated using data at over a range of subcoolings (11 °C <= DeltaTsub <= 32.6 °C), heater sizes (2.1 mm <= Lh <= 7 mm), and dissolved gas concentrations (3 ppm <= cg <= 3500 ppm). The prediction errors are significantly smaller than those from correlations currently available in the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] On the Scaling of Pool Boiling Heat Flux With Gravity and Heater Size [texte imprimé] / Rishi Raj, Auteur ; Jungho Kim, Auteur ; John McQuillen, Auteur . - 2012 . - 13 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 13 p. Mots-clés : Boiling  Heat  transfer  Surface  tension  Zero  gravity  experiments Index. décimale : 536 Chaleur. Thermodynamique Résumé : A framework for scaling pool boiling heat flux is developed using data from various heater sizes over a range of gravity levels. Boiling is buoyancy dominated for large heaters and/or high gravity conditions and the heat flux is heater size independent. The power law coefficient for gravity is a function of wall temperature. As the heater size or gravity level is reduced, a sharp transition in the heat flux is observed at a threshold value of Lh/Lc = 2.1. Below this threshold value, boiling is surface tension dominated and the dependence on gravity is smaller. The gravity scaling parameter for the heat flux in the buoyancy dominated boiling regime developed in the previous work is updated to account for subcooling effect. Based on this scaling parameter and the transition criteria, a methodology for predicting heat flux in the surface tension dominated boiling regime, typically observed under low-gravity conditions, is developed. Given the heat flux at a reference gravity level and heater size, the current framework allows the prediction of heat flux at any other gravity level and/or heater size under similar experimental conditions. The prediction is validated using data at over a range of subcoolings (11 °C <= DeltaTsub <= 32.6 °C), heater sizes (2.1 mm <= Lh <= 7 mm), and dissolved gas concentrations (3 ppm <= cg <= 3500 ppm). The prediction errors are significantly smaller than those from correlations currently available in the literature. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]