Comparative study of V-ribs miniature with dimple hybrid roughness along with dimples shaped roughness used in solar air heating system

In this work, a numerical and experimental study on flow-dynamics and heat transfer in a solar air heater (SAH) provided with dimpled and dimple with v-miniature as roughness element over plate (absorber). For experimental study a staggered dimple was created on the plate (absorber) as a roughness element and ANSYS was used for the simulation. By providing the relative longway length (L/d), relative depth of dimple, and relative short way length (S/d) range from 15-25, 0.024-0.036, and 10-15, respectively. The RNG k-epsilon model was used to model turbulence, and Nusselt number and friction factor values are estimated for a proposed roughness. The simple duct was validated using Dittus Boelter along with this comparison is also made for roughened plate with experimental and numerical values. The thermal and hydraulic performance parameter of the proposed roughness was also studied by varying the Reynolds numbers from 5000 to 20,000. Results revealed that dimple with v-miniature at relative short way lengths (S/d) value of 15 shows the highest heat transfer at Reynolds number value of 20,000. It was observed that maximum thermal and hydraulic performance parameter has achieved value of 1.73 at alpha = 45 degrees, L/d = 20 and S/d = 15 at Reynolds number 20,000 for the dimple with v-miniatures roughness.