COBEM99

S10 Fluidodinâmica de Escoamento Multifásico

Title:

A CORRELATION TO THE HEAT TRANSFER COEFFICIENT IN NUCLEATE BOILING

Summary :

NUCLEATE BOILING HEAT TRANSFER IS A COMPLEX PHENOMENON, MAKING THE DEVELOPMENT OF A CORRELATION FOR THE HEAT TRANSFER COEFFICIENT RATHER CUMBERSOME DUE TO THE NUMBER OF PHYSICAL PARAMETERS INVOLVED IN IT. SOME AUTHORS HAVE FOLLOWED A PRAGMATIC APPROACH TO THE PROBLEM BY CORRELATING THE HEAT TRANSFER COEFFICIENT IN TERMS OF REDUCED PRIMITIVE PROPERTIES. TWO OF THE MOST KNOWLEDGEABLE AUTHORS WHO HAVE FOLLOWED THIS APPROACH ARE GORENFLO AND COOPER. COMPARISONS HAVE BEEN PERFORMED AMONG RESULTS FROM THE CORRELATIONS PROPOSED BY THESE RESEARCHERS AND EXPERIMENTAL RESULTS OBTAINED ELSEWHERE FOR REFRIGERANTS R-11, R-113 AND R-114. THESE COMPARISONS HAVE SHOWN THAT COOPER’S CORRELATION IS BEST FITTED FOR HALOCARBON REFRIGERANTS. THE CORRELATION PROPOSED BY GORENFLO ADS THE DIFFICULTY OF INCLUDING A NUMERICAL FACTOR SPECIFIC FOR EACH FLUID. LEINER MODIFIED GORENFLO’S CORRELATION TO DETERMINE THE NUMERICAL FACTOR AS A FUNCTION OF KNOWN PHYSICAL PARAMETERS OF THE FLUID. IN PRESENT STUDY, THE FORM OF THIS FUNCTION HAS BEEN INVESTIGATED FOR HALOCARBON REFRIGERANTS. THE OBTAINED CORRELATION IS WRITTEN IN TERMS OF THE FOLLOWING PARAMETERS: REDUCED PRESSURE, ECCENTRIC AND COMPRESSIBILITY FACTORS AT THE CRITICAL STATE, AND A DIMENSIONLESS SPECIFIC HEAT OF THE VAPOR PHASE. THE CORRELATION COMPARES WELL WITH EXPERIMENTAL RESULTS.

Author :

Jabardo, José M. Saiz
Ribatski, Gherhardt 0

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