Geometrical effect of natural convection in an air channel with a cavity at the turning section on thermal behavior and heat removal performance

Abstract

The geometrical effect of natural convection in an air channel with a cavity at the turning section was investigated experimentally by controlling the vertical upper gap (G, 100–75 mm) and horizontal lower channel gap (B, 100 - 300 mm) and varying the heat load conditions (P, 1.35–6.20 kW). The thermal behavior in the channel was considered in terms of the temperature distributions of the walls, and the air temperature field was estimated from the measured air temperature. Additionally, the heat removal performance was analyzed for changes in each parameter to find the critical design parameter on cooling performance.The heat load condition positively affected the heat removal performance, but it did not affect the trend of the wall temperature distributions or the shape of the temperature field in the channel. A lower channel gap directly affected the cooling in the lower channel (cavity) between the lower curved wall and bottom but did not appreciably affect the cooling in the upper vertical channel between both vertical walls and overall heat removal performance (RSDMax = 3.2 %). As a result, the most critical parameter was the upper vertical channel gap because it affected both lower and upper channels and played a vital role in determining the overall heat transfer performance (RSDMax = 11.0 %). Additionally, it was confirmed that the location where the peak wall temperature appeared changed as the vertical gap size was altered.Interestingly, we found that the transition phenomenon eliminating the entrance effect occurred above the mid-height of the vertical channel in all experimental cases, and it was directly related to the heat removal performance. The temperature profiles developed smoothly along the height in only the G175 cases, which were the maximum heat removal performance cases, owing to the minimized entrance effect in the channel. In contrast, the temperature profiles below the mid-height of the vertical channel changed rapidly due to the entrance effect in other cases.