COBEM99

SR27 Transferência de Calor e Massa

Title:

OCCURRENCE OF REVERSE HEAT FLUX IN CONJUGATED HEAT TRANSFER IN FINNED CONCENTRIC TUBES

Summary :

ABSTRACT. THE OCCURRENCE OF REVERSE HEAT FLUX IN THE FLOW BETWEEN FINNED CONCENTRIC TUBES IS STUDIED. THIS PHENOMENON MUST BE ANALYZED WITH A CONJUGATED HEAT TRANSFER APPROACH, WHERE THE CONDUCTION IN THE SOLID AND THE CONVECTION IN THE FLUID ARE SIMULTANEOUSLY CALCULATED USING A UNIQUE DOMAIN. THE MASS, MOMENTUM, ENERGY AND TURBULENCE MODEL EQUATIONS ARE DISCRETISED BY THE FINITE ELEMENT TECHNIQUE AND SOLVED WITH A SEGREGATED FORMULATION. SEVERAL CONFIGURATIONS ARE STUDIED VARYING HEIGHT/PITCH OF THE FINS AND SOLID-FLUID THERMAL CONDUCTIVITY RATIO. THE RESULTS SHOWED THE OCCURRENCE OF REVERSE HEAT FLUX (FROM FLUID TO SOLID) AT THE FIN ROOT. THE HEAT TRANSFER IN THIS REGION IS WEAK AND THE RECIRCULATING FLOW HAS LOW VELOCITIES VALUES (DEAD ZONE). THE REVERSE HEAT FLUX MAGNITUDE INCREASES WITH REYNOLDS NUMBER AND IT IS HIGHER IN THE WATER FLOW THAN THE AIR ONE. KEYWORDS: REVERSE HEAT FLUX, CONJUGATED HEAT TRANSFER, FINS, FINITE ELEMENT.

Author :

ANDRADE, CLAUDIA REGINA
ZAPAROLI, EDSON LUIZ

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