Comparison of optimized roughness parameters of some artificially roughened solar air heaters

In this study, theoretical investigation derived from experimental correlations and the artificial bee colony optimization method are used to determine the optimum geometrical parameters which maximize the termohydraulic efficiency of some artificially roughened solar air heaters. Nine different roughness types are considered, i.e., transverse wedge-shaped rib roughness, protrusion roughness, multiple v-ribs roughness, rib-grooved roughness, metal grit ribs roughness, compound turbulators roughness, v-shaped rib roughness, arc-shaped wire roughness, and discrete v-down ribs roughness. The effects of the artificial roughness element parameters on the best thermal performance and the thermohydraulic performance are compared. Optimum results are obtained with multiple v-ribs roughness for the low mass flow rate (MFR = 0.1 kg/s) and with protrusion roughness for the high mass flow rate (MFR = 0.5 kg/s). Optimum roughness parameters and corresponding thermal and thermohydraulic efficiencies are tabulated for each solar collector type. As expected, increased roughness geometry leads to higher pressure loss and reduces thermohydraulic efficiency.