الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 79 |  |  |
| | | from | 79 | | |
Abstract
Heat Convection across circular concentric gaps between cylinders is crucial in industrial applications, including electronic cooling, heat exchangers, and solar collectors. The effect of longitudinal and annular grooves on the outside surface of the inside tube on natural convective heat transfer in encloser concentric circular annulus is experimentally investigated in the present work. Twin pairs of circular aluminum cylinders with the same radius ratio, length, and surface area were examined. Each one consists of two concentric circular cylinders. To maintain a steady heat flux, the inside cylinder of each pair has an electrical heater connected. The results indicate that the increases in the Nusselt number of around 25%, 43%, 67%, 123%, 142%, 157%, and 172% are seen for groove depths of 0.05 cm, 0.10 cm, 0.15 cm, 0.20 cm, 0.25 cm, 0.3 cm, 0.35 cm, and 0.4 cm. In addition, increasing the depth of the longitudinal groove raises the Nusselt number by roughly 33%, 51%, 79%, 99 %, 136 %, 153 %, 173 %, and 184 %. The longitudinal grooves with a depth of 4.0 mm enable a 38% increase in free convection heat transfer over prior research. An annular groove of 4.0 mm depth increases free convection heat transfer by 36%.