Heat transfer rate and uniformity of mist flow jet impingement for glass tempering

• Published in: International journal of heat and mass transfer 2017-12, Vol.115, p.368-378
• Main Authors: Yu, Pingping, Zhu, Keqian, Sun, Tao, Yuan, Ningyi, Ding, Jianning
• Format: Article
• Language: English
• Subjects: Air/mist two phase flow; Conjugate heat transfer; Glass tempering; Small jet impingement
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.08.065

•Use of mist flow jet impingement cooling technology on ultra-thin glass.•Correlation for surface average Nusselt number is given.•Controlling droplet diameter can obtain better heat transfer uniformity.•Mist flow jet impingement reduces the amount of air and save energy. The thinning and miniaturization of components, such as liquid crystal display and solar cells, has increased the market demand for tempered ultra-thin glass. The physical tempering in glass, which is less than 2mm thick, is difficult to achieve in air jet impingement. In this study, we propose the use of mist flow jet impingement cooling technology on ultra-thin glass. The effects of the mist flow droplets diameters, nozzle inlet temperature, and mass fraction on the heat transfer rate and uniformity are numerically studied. Our performance in terms of the heat transfer rate and the uniformity is accounted for through an evaluation of the surface-averaged temperature, averaged Nusselt number, surface-averaged Nusselt number, and surface standard deviation percentage of the Nusselt number. The empirical correlation for the surface averaged Nusselt number asa function of mist flow droplet diameters is provided. The droplet diameter is the major factor affecting the heat transfer rate, while the jet inlet temperature is a minor factor. We can obtain a better heat transfer uniformity by controlling the droplet diameter of the mist flow jet impingement. Using mist flow jet impingement, we would not only greatly reduce the amount of air and save energy, but also meet the needs of sudden cooling for tempered glass with a thickness of less than 2mm.