Accession Number : AD0679119

Title :   MODEL OF CRITICAL HEAT FLUX IN SUBCOOLED FLOW BOILING.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Fiori,Mario P. ; Bergles,Arthur E.

Report Date : SEP 1968

Pagination or Media Count : 157

Abstract : The physical phenomenon occurring before and at the critical heat flux (CHF) for subcooled flow boiling has been investigated. The first phase of this study established the basic nature of the flow structure at CHF. A photographic study of the flow in a glass annular test section was accomplished by using microflash lighting. The results showed that the flow structure at CHF for high heat flux (1 to 5 million Btu/hr-sq ft), high subcooling (50-110F), at low pressures (less than 100 psia) was slug or froth flow depending on the mass velocity. Nucleation was shown to exist in the superheated liquid film. Pin-holes in the burned-out test sections suggested that the CHF condition was extremely localized. Flow regime studies in tabular and annular geometries, using an electrical resistance probe, provided further evidence of the slug or froth nature of the flow, and also showed that dryout of the superheated liquid film was not responsible for CHF. Since this evidence was contradictory to previously formulated models of CHF, a new model was proposed. (Author)

Descriptors :   (*HEAT FLUX, FLUID FLOW), (*FLUID FLOW, BOILING), COOLING, CONVECTION(HEAT TRANSFER), NUCLEATION, MATHEMATICAL MODELS, FLOW VISUALIZATION, PHOTOGRAPHY, WATER, TEMPERATURE, QUENCHING, HEAT EXCHANGERS, BUBBLES

Subject Categories : Fluid Mechanics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE