Abstract:
This study experimentally explores the influence of inclination angle and wavy tape inserts on mixed convection heat transfer and pressure drop in a solar air heater tube. Experiments at 15° and 30° inclinations, with Reynolds numbers from 455 to 6059 reveal that increasing inclination reduces heat transfer and pressure drop. Transition Reynolds numbers vary with heat flux levels: 3 kW/m2 (2528-3793), 2 kW/m2 (2520-3801), and 1 kW/m2 (2627-3848). The Colburn factors in the laminar and transition flow regimes shows distinct characteristics but converge in turbulent flow. The wavy tape with a width ratio of 0.8 and a wave ratio of 0.75 exhibits the highest Colburn factor and friction factor, while a width ratio of 0.6 and a wave ratio of 2.25 lead to minima of these values. With increase in the inclination, the effect of buoyancy forces starts decreasing. This leads to reduced disturbance compared to a lower angular position. Novel correlations were also developed for predicting the Colburn and friction factors.