Thermo-Hydraulic Characteristics Evaluation of a Triangular Solar Air Heater Duct Having Transverse Ribs With Gaps: An Experimental Study

An experimental investigation is carried out to analyze the thermo-hydraulic characteristics of a triangular solar air heater duct having transverse ribs with gaps. The roughness parameters, such as non-dimensional pitch (P/e or P¯) and non-dimensional height (e/Dh or e¯) are kept in the range of 4.88–20 and 0.021–0.044, respectively. Reynolds number (Re) is kept in the range of 4000–18,000. Two and three gaps of each of 0.01 m are provided to each odd and even number ribs, respectively. Non-dimensional primary width (w1/W) and non-dimensional secondary width (w2/W) are kept constant at 0.29 and 0.4, respectively. A maximum heat transmission of 3.14 times that of the base model is achieved for the transverse ribs with gaps having non-dimensional pitch and height of 9.76 and 0.044, respectively, at Re = 18,000. In the parametric range, the highest friction factor of 3.88 times the base model is encountered for the non-dimensional pitch and height of 4.88 and 0.044, respectively, at Re = 4000. The highest thermal enhancement ratio of 2.31 is reported for the non-dimensional pitch and height of 9.76 and 0.044, respectively, at Re = 18,000. The correlation for the Nusselt number and friction factor is formulated, agreeing with experimental data within ±12% and ±8% deviation, respectively.