NUMERICAL-ANALYSIS OF THE FLOW AND HEAT-TRANSFER CHARACTERISTICS FOR FORCED CONVECTION-RADIATION IN ENTRANCE REGION OF AN INTERNALLY FINNEDTUBES

The flow and heat transfer characteristics of combined forced convecti on and radiation in the entrance region of internally finned tubes are investigated numerically in this paper. The uniform flow is considere d for an inlet flow condition. A three dimensional parabolic problem i s solved by a marching-type procedure envolving a series of two dimens ional elliptic problems in the cross-stream plane. The SIMPLER-algorit hm and Raithby's pressure-velocity coupling method are employed to ana lyze the flow and heat transfer characteristics. For the calculation o f radiative heat transfer, the P-1-approximation and the weighted sum of gray gases method (WSGGM) are used. The effects of fin height, numb er of fins, optical thickness, reference temperature, and Planck numbe r on the flow and heat transfer characteristics are examined. It was f ound that the effect of fin-height on the heat transfer characteristic is more dominant than that of number of fins. The present results sho w that the optimal non-dimensional fin height and number of fins are 0 .4 and 16, respectively.