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DYNAMIC MODEL OF ENHANCED BOILING HEAT TRANSFER ON POROUS SURFACES.

Author(s) : NAKAYAMA W.

Type of article: Article

Summary

PART I: EXPERIMENTAL INVESTIGATION. ENHANCEMENT OF NUCLEATE BOILING HEAT TRANSFER HAS BEEN STUDIED WITH THE STRUCTURED SURFACES COMPOSED OF INTERCONNECTED INTERNAL CAVITIES IN THE FORM OF TUNNELS AND SMALL PORES CONNECTING THE POOL LIQUID AND THE TUNNELS. THE BOILING CURVES OF R-11, WATER AND NITROGEN SHOW 80 TO 90 PERCENT REDUCTION OF WALL SUPERHEAT REQUIRED TO TRANSFER THE SAME HEAT FLUX AS THAT ON PLAIN SURFACES, WHEN THE PORE DIAMETER IS SET AROUND 0.1 MM. THE EXPERIMENTAL DATA ON BUBBLE FORMATION SHOWED A SIGNIFICANT CONTRIBUTIONOF LATENT HEAT TRANSPORT TO THE ENHANCEMENT. A VISUALIZATION STUDY MADE WITH A TRANSPARENT STRUCTURED MODEL SUGGESTED THAT THE LIQUID SUCTION INTO THE TUNNEL IS TRIGGERED BY THE BUBBLE GROWTH AT ACTIVE PORES AND SUBSEQUENT EVAPORATION INSIDE THE TUNNEL PLAYS A VITAL ROLE IN DRIVING THE BUBBLE FORMATION CYCLE. THIS OBSERVATION LED TO A CONCEPTION OF THE DYNAMIC MODEL EXPOUNDED IN PART II. PART II: REPORTED IN PART I, AN ANALYTICAL MODEL OF THE DYNAMIC CYCLE OF BUBBLE FORMATION IS PROPOSED. THE CYCLE CONSISTS OF A WAITING PERIOD AND A BUBBLE GROWTH PERIOD; IN THE FORMER THE PRESSURE IN THE TUNNEL IS INCREASED DUE TO EVAPORATION FROM INTERNALLY HELD MENISCUSES AND IN THE LATTER A CERTAIN AMOUNT OF POOL LIQUID IS SUCKED IN THE TUNNEL TO BE SUBSEQUENTLY EVAPORATED. THE EQUATIONS ARE FORMULATED WITH THE ADOPTION OF A MODERATE NUMBER OF EMPIRICAL CONSTANTS. THEIR SOLUTIONS GIVE THE PREDICTIONS OF LATENT HEAT FLU.

Details

  • Original title: DYNAMIC MODEL OF ENHANCED BOILING HEAT TRANSFER ON POROUS SURFACES.
  • Record ID : 1982-0049
  • Languages: English
  • Source: J. Heat Transf. - vol. 102 - n. 3
  • Publication date: 1980
  • Document available for consultation in the library of the IIR headquarters only.

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