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Title: Boiling on horizontal surfaces coated with porous metal wicks

Abstract

Boiling experiments intended to simulate heat pipe operating conditions were conducted on a copper surface covered with copper foametal and nickel fiber wicks 3.175 and 4.760 mm thick. The experiments were conducted on a horizontal surface open to the atmosphere with water as the working fluid. The experimental surface was operated like a heat pipe with distilled water supplied upstream of the heated section and transported by capillary action across a section which was adiabatic to the heated section where boiling took place. At low excess temperature, less than 10 to 20 C, the heat flux from the porous coated surfaces is comparable to or greater than that predicted for a smooth surface using the Rohsenow correlation. At higher excess temperatures corresponding to heat fluxes between 10{sup 5} and 10{sup 6} W/m{sup 2} the increase in heat flux with excess temperature is much less than that predicted by the Rohsenow correlation. When the wicks were vented by cutting slots covering 10 to 20% of the total surface area the heat flux increased, in some cases by a factor of three, for a given excess temperature. The heat flux at which the slope of the boiling curve decreased also increased formore » the vented surfaces. This is attributed to the provision of a low resistance path for the steam to escape providing a surface that is more highly wetted. A mathematical model for the transport with boiling in the porous wick is developed in an attempt to gain further understanding of the processes involved. The model predicts dryout conditions that are in reasonable agreement with experimental observations. However, the model predicts decreasing vapor pressure, and hence temperature, adjacent to the heated surface with increasing heat flux as a result of the decrease in relative permeability of the partially saturated wick.« less

Authors:
;
Publication Date:
Research Org.:
Faculty of Engineering-Mataria, Cairo (EG)
OSTI Identifier:
20014425
Resource Type:
Conference
Resource Relation:
Conference: 32nd National Heat Transfer Conference, Baltimore, MD (US), 08/08/1997--08/12/1997; Other Information: PBD: 1997; Related Information: In: ASME proceedings of the 32nd national heat transfer conference (HTD-Vol. 349). Volume 11: Interfacial thermal phenomena in thin films; Heat pipes and thermosyphons; Heat and mass transfer in porous media, by Goodson, K.; Chang, W.S.; Charmchi, M.; Hadim, H. [eds.], 211 pages.
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; BOILING; OPERATION; SIMULATION; HEAT PIPES; HEAT PIPE WICKS; POROUS MATERIALS; EXPERIMENTAL DATA; WORKING FLUIDS; DRYOUT; HEAT TRANSFER

Citation Formats

Abou-Zyan, H.Z., and Plumb, O.A. Boiling on horizontal surfaces coated with porous metal wicks. United States: N. p., 1997. Web.
Abou-Zyan, H.Z., & Plumb, O.A. Boiling on horizontal surfaces coated with porous metal wicks. United States.
Abou-Zyan, H.Z., and Plumb, O.A. Tue . "Boiling on horizontal surfaces coated with porous metal wicks". United States. doi:.
@article{osti_20014425,
title = {Boiling on horizontal surfaces coated with porous metal wicks},
author = {Abou-Zyan, H.Z. and Plumb, O.A.},
abstractNote = {Boiling experiments intended to simulate heat pipe operating conditions were conducted on a copper surface covered with copper foametal and nickel fiber wicks 3.175 and 4.760 mm thick. The experiments were conducted on a horizontal surface open to the atmosphere with water as the working fluid. The experimental surface was operated like a heat pipe with distilled water supplied upstream of the heated section and transported by capillary action across a section which was adiabatic to the heated section where boiling took place. At low excess temperature, less than 10 to 20 C, the heat flux from the porous coated surfaces is comparable to or greater than that predicted for a smooth surface using the Rohsenow correlation. At higher excess temperatures corresponding to heat fluxes between 10{sup 5} and 10{sup 6} W/m{sup 2} the increase in heat flux with excess temperature is much less than that predicted by the Rohsenow correlation. When the wicks were vented by cutting slots covering 10 to 20% of the total surface area the heat flux increased, in some cases by a factor of three, for a given excess temperature. The heat flux at which the slope of the boiling curve decreased also increased for the vented surfaces. This is attributed to the provision of a low resistance path for the steam to escape providing a surface that is more highly wetted. A mathematical model for the transport with boiling in the porous wick is developed in an attempt to gain further understanding of the processes involved. The model predicts dryout conditions that are in reasonable agreement with experimental observations. However, the model predicts decreasing vapor pressure, and hence temperature, adjacent to the heated surface with increasing heat flux as a result of the decrease in relative permeability of the partially saturated wick.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jul 01 00:00:00 EDT 1997},
month = {Tue Jul 01 00:00:00 EDT 1997}
}

Conference:
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