Convective heat transfer by a row of confined air jets from round holes equipped with triangular tabs

Experimental study was conducted to investigate the heat transfer produced by single row of impinging jets inside a confined channel with different tab orientations of the triangular tabs at the jet exits. The effects of the tab number, tab orientation angle and tab penetration length on the jet impingement heat transfer behaviors were experimentally tested under nozzle-to-plate spacing of 1-3 diameters and jet Reynolds number of 10,000-20,000. A numerical computation was also carried out on the simulation of impinging jet flow fields to reveal the trends and differences observed in the heat transfer measurements. The results show that the presence of tabs increases the jet core velocity and induces array pairs of vortices, and hence enhances the heat transfer in the impingement region over the no-tab case. The tabs oriented upwards or downwards at 45° can better improve the heat transfer than the normal inclination case. The heat transfer enhancement produced by the tabs increases with the tab penetration length for the given range of 0.12-0.23 diameter. For the arrays of 4-12 triangular tabs, the array of 8 tabs seems to produce more effective heat transfer enhancement.