Heater Orientation Effects on Pool Boiling of Micro-Porous-Enhanced Surfaces in Saturated FC-72

Chang, Joonho; You, Seungkwon

doi:10.1115/1.2822592

“…According to the results by Howard and Mudawar (1999) and Brusster (1997), where the effect of surface orientation on CHF was examined with water and FC-72, the CHF is little affected by angle of inclination and takes similar values from  =0 to 90. Chan and You (1996) measured the CHF of FC-72 and show that the variation in CHF is about 14% in the  =0 to 90 range. Considering these results, it is thought that Eq.…”

Section: Critical Heat Fluxesmentioning

confidence: 99%

Critical heat flux on a vertical surface in saturated pool boiling at high pressures

Sakashita

¹

2016

JTST

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This paper investigates the CHF in saturated pool boiling of ethanol, R141b, and water on a 7 mm diameter vertical copper surface at high pressures. The pressures are from 0.1 to 3 MPa for ethanol, 0.1 to 1.5 MPa for R141b, and 0.1 to 0.8 MPa for water. The results show that the occurrence of CHF is accompanied by the formation of large vapor masses covering most of the heating surface with all three liquids over the whole range of pressures investigated here. The well-known Kutateladze-type CHF correlation explains the variations in the CHF with pressure well for ethanol and R141b, and underestimates the pressure dependence of the CHF for water. A correlation considering the effect of surface wettability on the CHF agrees fairly well with the CHF for water in the whole range of pressures here, when the temperature dependence of the contact angle determined from available data is incorporated into the correlation. This suggests that it is necessary to consider changes in surface wettability with pressure to be able to predict the CHF of water at high pressures.

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“…According to the results by Howard and Mudawar (1999) and Brusster (1997), where the effect of surface orientation on CHF was examined with water and FC-72, the CHF is little affected by angle of inclination and takes similar values from φ =0° to 90°. Chan and You (1996) measured the CHF of FC-72 and show that the variation in CHF is about 14% in the φ =0° to 90° range. Considering these results, it is thought that Eq.…”

Section: Critical Heat Fluxesmentioning

confidence: 99%

Critical Heat Flux on a Vertical Surface in Saturated Pool Boiling at High Pressures

Sakashita

¹

2016

The Proceedings of the Thermal Engineering Conference

0

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This paper investigates the CHF in saturated pool boiling of ethanol, R141b, and water on a 7 mm diameter vertical copper surface at high pressures. The pressures are from 0.1 to 3 MPa for ethanol, 0.1 to 1.5 MPa for R141b, and 0.1 to 0.8 MPa for water. The results show that the occurrence of CHF is accompanied by the formation of large vapor masses covering most of the heating surface with all three liquids over the whole range of pressures investigated here. The well-known Kutateladze-type CHF correlation explains the variations in the CHF with pressure well for ethanol and R141b, and underestimates the pressure dependence of the CHF for water. A correlation considering the effect of surface wettability on the CHF agrees fairly well with the CHF for water in the whole range of pressures here, when the temperature dependence of the contact angle determined from available data is incorporated into the correlation. This suggests that it is necessary to consider changes in surface wettability with pressure to be able to predict the CHF of water at high pressures.

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“…O'Connor and You (1995) found a 109% increase in the CHF limit over a non-painted surface in saturated FC-72 with almost 80% reduction in nucleate boiling superheat. Chang and You (1996) obtained approximately 80% reduction in incipient superheat, 330% enhancement in nucleate boiling heat transfer, and 100% enhancement in CHF using micro-porous layer coatings made of copper particles (1-50 m) and aluminum particles (1-20 m). Dizon et al (2004) obtained up to more than 100% increase in the CHF value at different angular locations of a downward facing curved surface under transient quenching conditions.…”

Section: Introductionmentioning

confidence: 99%

Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling

Yang

¹

,

Cheung

²

,

Rempe

³

et al. 2005

Heat Transfer: Volume 2

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Four types of steady-state boiling experiments were conducted to investigate the efficacy of two distinctly different heat transfer enhancement methods for external reactor vessel cooling under severe accident conditions. One method involved the use of a thin vessel coating and the other involved the use of an enhanced insulation structure. By comparing the results obtained in the four types of experiments, the separate and integral effect of vessel coating and insulation structure were determined. Correlation equations were obtained for the nucleate boiling heat transfer and the critical heat flux. It was found that both enhancement methods were quite effective. Depending on the angular location, the local critical heat flux could be enhanced by 1.4 to 2.5 times using vessel coating alone whereas it could be enhanced by 1.8 to 3.0 times using an enhanced insulation structure alone. When both vessel coating and insulation structure were used simultaneously, the integral effect on the enhancement was found much less than the product of the two separate effects, indicating possible competing mechanisms (i.e., interference) between the two enhancement methods.

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Heater Orientation Effects on Pool Boiling of Micro-Porous-Enhanced Surfaces in Saturated FC-72

Cited by 204 publications

References 15 publications

Critical heat flux on a vertical surface in saturated pool boiling at high pressures

Critical heat flux on a vertical surface in saturated pool boiling at high pressures

Critical Heat Flux on a Vertical Surface in Saturated Pool Boiling at High Pressures

Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling

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