Numerical simulation of pool boiling: the effects of initial thermal boundary layer, contact angle and wall superheat

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBNResearchpeer-review

Abstract

Boiling heat transfer has been a subject of extensive investigation during the last decades. Since the subprocesses in nucleate boiling, involve quite complex physics, the development of comprehensive correlations and/or models has not been possible so far. However, more recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and heat transfer characteristics. In the present paper, heat transfer and phase-change are coupled with a previously improved and validated Volume Of Fluid (VOF) model for adiabatic bubble dynamics. The model is initially verified with an existing analytical solution for cases of evaporating bubble growth in a superheated liquid domain. Moreover, the predictions of the proposed model regarding the bubble detachment characteristics are also validated against available experimental data on pool boiling of refrigerants. The validated and optimised version of the model is further applied for the conduction of a wide range of parametric numerical simulations, identifying the effects of the initial thermal boundary layer thickness, the contact angle between the liquid/vapour interface and the heated plate, as well as the plate superheat, on the bubble detachment characteristics. It is found that the bubble growth and detachment characteristics are highly sensitive to the initially developed thermal boundary layer thickness, following a linear relationship. This has a strong implication on the experimental activities, since in many cases it is not clear at which time the initial measurements of the pool boiling characteristics have been carried out with respect to the time scale to reach the quasi steady-state condition of the thermal boundary layer, linked to the natural convection. As for the imposed contact angle effect, a threshold value is identified below which, the effect on the bubble detachment characteristics is minimal while above this value the influence is quite significant. Moreover, the bubble detachment characteristics follow an exponential increase with the corresponding increase in the superheat of the heated plate.
Original languageEnglish
Title of host publicationProceedings of 14th UK Heat Transfer Conference
Place of PublicationEdinburgh
Pages0-0
Number of pages1
Publication statusPublished - 8 Sep 2015
Event14th UK Heat Transfer Conference - Edinburgh, United Kingdom, 7–8 September, 2015
Duration: 8 Sep 2015 → …

Conference

Conference14th UK Heat Transfer Conference
Period8/09/15 → …

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thermal boundary layer
boiling
bubbles
detachment
simulation
boundary layer thickness
heat transfer
nucleate boiling
liquid-vapor interfaces
quasi-steady states
refrigerants
free convection
conduction
physics
thresholds
fluids
liquids
predictions

Cite this

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title = "Numerical simulation of pool boiling: the effects of initial thermal boundary layer, contact angle and wall superheat",
abstract = "Boiling heat transfer has been a subject of extensive investigation during the last decades. Since the subprocesses in nucleate boiling, involve quite complex physics, the development of comprehensive correlations and/or models has not been possible so far. However, more recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and heat transfer characteristics. In the present paper, heat transfer and phase-change are coupled with a previously improved and validated Volume Of Fluid (VOF) model for adiabatic bubble dynamics. The model is initially verified with an existing analytical solution for cases of evaporating bubble growth in a superheated liquid domain. Moreover, the predictions of the proposed model regarding the bubble detachment characteristics are also validated against available experimental data on pool boiling of refrigerants. The validated and optimised version of the model is further applied for the conduction of a wide range of parametric numerical simulations, identifying the effects of the initial thermal boundary layer thickness, the contact angle between the liquid/vapour interface and the heated plate, as well as the plate superheat, on the bubble detachment characteristics. It is found that the bubble growth and detachment characteristics are highly sensitive to the initially developed thermal boundary layer thickness, following a linear relationship. This has a strong implication on the experimental activities, since in many cases it is not clear at which time the initial measurements of the pool boiling characteristics have been carried out with respect to the time scale to reach the quasi steady-state condition of the thermal boundary layer, linked to the natural convection. As for the imposed contact angle effect, a threshold value is identified below which, the effect on the bubble detachment characteristics is minimal while above this value the influence is quite significant. Moreover, the bubble detachment characteristics follow an exponential increase with the corresponding increase in the superheat of the heated plate.",
author = "Anastasios Georgoulas and Marco Marengo",
year = "2015",
month = "9",
day = "8",
language = "English",
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booktitle = "Proceedings of 14th UK Heat Transfer Conference",

}

Georgoulas, A & Marengo, M 2015, Numerical simulation of pool boiling: the effects of initial thermal boundary layer, contact angle and wall superheat. in Proceedings of 14th UK Heat Transfer Conference. Edinburgh, pp. 0-0, 14th UK Heat Transfer Conference, 8/09/15.

Numerical simulation of pool boiling: the effects of initial thermal boundary layer, contact angle and wall superheat. / Georgoulas, Anastasios; Marengo, Marco.

Proceedings of 14th UK Heat Transfer Conference. Edinburgh, 2015. p. 0-0.

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNConference contribution with ISSN or ISBNResearchpeer-review

TY - GEN

T1 - Numerical simulation of pool boiling: the effects of initial thermal boundary layer, contact angle and wall superheat

AU - Georgoulas, Anastasios

AU - Marengo, Marco

PY - 2015/9/8

Y1 - 2015/9/8

N2 - Boiling heat transfer has been a subject of extensive investigation during the last decades. Since the subprocesses in nucleate boiling, involve quite complex physics, the development of comprehensive correlations and/or models has not been possible so far. However, more recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and heat transfer characteristics. In the present paper, heat transfer and phase-change are coupled with a previously improved and validated Volume Of Fluid (VOF) model for adiabatic bubble dynamics. The model is initially verified with an existing analytical solution for cases of evaporating bubble growth in a superheated liquid domain. Moreover, the predictions of the proposed model regarding the bubble detachment characteristics are also validated against available experimental data on pool boiling of refrigerants. The validated and optimised version of the model is further applied for the conduction of a wide range of parametric numerical simulations, identifying the effects of the initial thermal boundary layer thickness, the contact angle between the liquid/vapour interface and the heated plate, as well as the plate superheat, on the bubble detachment characteristics. It is found that the bubble growth and detachment characteristics are highly sensitive to the initially developed thermal boundary layer thickness, following a linear relationship. This has a strong implication on the experimental activities, since in many cases it is not clear at which time the initial measurements of the pool boiling characteristics have been carried out with respect to the time scale to reach the quasi steady-state condition of the thermal boundary layer, linked to the natural convection. As for the imposed contact angle effect, a threshold value is identified below which, the effect on the bubble detachment characteristics is minimal while above this value the influence is quite significant. Moreover, the bubble detachment characteristics follow an exponential increase with the corresponding increase in the superheat of the heated plate.

AB - Boiling heat transfer has been a subject of extensive investigation during the last decades. Since the subprocesses in nucleate boiling, involve quite complex physics, the development of comprehensive correlations and/or models has not been possible so far. However, more recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and heat transfer characteristics. In the present paper, heat transfer and phase-change are coupled with a previously improved and validated Volume Of Fluid (VOF) model for adiabatic bubble dynamics. The model is initially verified with an existing analytical solution for cases of evaporating bubble growth in a superheated liquid domain. Moreover, the predictions of the proposed model regarding the bubble detachment characteristics are also validated against available experimental data on pool boiling of refrigerants. The validated and optimised version of the model is further applied for the conduction of a wide range of parametric numerical simulations, identifying the effects of the initial thermal boundary layer thickness, the contact angle between the liquid/vapour interface and the heated plate, as well as the plate superheat, on the bubble detachment characteristics. It is found that the bubble growth and detachment characteristics are highly sensitive to the initially developed thermal boundary layer thickness, following a linear relationship. This has a strong implication on the experimental activities, since in many cases it is not clear at which time the initial measurements of the pool boiling characteristics have been carried out with respect to the time scale to reach the quasi steady-state condition of the thermal boundary layer, linked to the natural convection. As for the imposed contact angle effect, a threshold value is identified below which, the effect on the bubble detachment characteristics is minimal while above this value the influence is quite significant. Moreover, the bubble detachment characteristics follow an exponential increase with the corresponding increase in the superheat of the heated plate.

M3 - Conference contribution with ISSN or ISBN

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