" EXPERIMENTAL AND COMPUTATIONAL INVESTIGATION OF SPRAY HEAT EXCHANGER PERFORMANCE "

Abstract

A study of the impact dynamics of liquid droplets on a solid surface is required for modeling industrial processes such as spray cooling of hot surfaces, fire . extinguishing systems by sprinklers, plasma coating, evaporative cooling, hot tubes or surface cooling (quenching ),...ect. In these cases the surface is often very hot, sometimes the

temperature is above the leidenfrost point of the liquid droplet. For this case the heated surface. is wetted slightly and the impinging droplets are rebounded or reflected from the surface after a very small period of time which is usually called waiting time. The tendency of a droplet to deposit •or to rebound, upon impact is determined primarily by the liquid viscosity,

liquid contact angle, surface temperature and impinging droplet impact velocity.. Also. the placement of a subcooled impinging droplet on a heated surface results in complex transient spreading orrebounding activity during. heating up the liquid droplet upon contact. •Spray cooling with phase change has been demonstrated to be a viable effective method to remove high heat from hotsurface. The present analytical solution and experimental study are conducted

to evaluate :

a- Sprayeddropletmitigation in the surrounding vapour

b- The droplet phase change and the heat transfer. between heated tube surface and impinging water liquid droplet.