Thermo-Hydraulics of Solar Air Heater Duct Roughened by Periodic Broken Arc Shaped Rib Combined with Staggered RIB

In this study, the thermo-hydraulic performance of rectangular duct roughened with a new configuration of periodic rib, broken arc rib combined with staggered rib piece on one broad wall is determined for flow Reynolds number range of 2000 to 16000. The roughened wall is uniformly heated while the remaining three walls are insulated. These boundary conditions correspond closely to those found in solar air heaters. The channel aspect ratio was 12. Four broken arc rib combined with staggered rib roughened plates having relative staggered rib position of 0.2, 0.4, 0.6 and 0.8 have been tested. The other roughness parameters such as the relative gap width, arc angle, relative gap position, relative staggered rib size, relative roughness pitch and relative roughness height were fixed as 1.0, 30°, 0.65, 5.0, 10 and 0.043 respectively. The Nusselt number and friction factor is found to be more at relative staggered rib position of 0.6 than at other relative staggered rib positions. The thermo-hydraulic performance is found to be more for relative staggered rib position of 0.6. The highest value of thermo-hydraulic performance is 2.25 corresponding to Reynolds number of 12000, as compared to 1.98 for broken arc rib roughened duct.