AbstractsEngineering

Local heat transfer profiles under a confined inclined slot jet discharging from a sharp-edged re-entry straight channel nozzle with various inclinations were measured. Average heat transfer was determined by integrating local profiles between positions of equal local Nusselt number. In the absence of significant heat transfer surface motion, impingement heat transfer expressed as stagnation and average Nusselt number with the present nozzles set either normal or 15$ sp circ$ from normal, is similar to that with ASME standard contoured entry nozzles at a nozzle-to-surface spacing of 6 nozzle widths. As this spacing is reduced by one-half, heat transfer becomes much larger for the re-entry channel nozzles, by 100% for average Nusselt number, by 250% for stagnation Nusselt number under the conditions tested. For an impingement surface moving at high speed, highest heat transfer is obtained with the nozzle set at inclinations between normal and 15$ sp circ$ with the jet opposing the impingement surface motion. Use of jets in the aiding flow orientation result in large drops in heat transfer rate, as does the use of opposing jets inclined at angles large than 15$ sp circ$ from normal. The same large advantage of the re-entry straight channel nozzle over the ASME standard contoured entry nozzle applies for impingement surface moving at high speeds as in the absence of surface motion. The importance of asymmetric exhaust port location is documented for the case of inclined slot jets impinging on moving or stationary impingement surface, and for normal slot jets impinging on high speed heat transfer surfaces.