Experimental Investigation on Cooling Performance of Borated Water During Immersion Quenching at the Saturated and Sub-Cooled Conditions

Abstract

Film boiling occurs when an overheated sample is rapidly plunged into the liquid. The study of film boiling is paramount in many engineering applications, like, cooling of nuclear reactor fuel rods, regenerative cooling of rockets, and wet treatment of blast slag furnaces. The objective of the present study is to explore the influence of boric acid at various concentrations (0.5%, 1%, 3%, and 5% vol.) and subcooling temperature on film boiling heat transfer using stainless steel rod (304 L). We performed vertical immersion quenching experiments in subcooled (50 °C) and saturation temperature at atmospheric conditions. Under saturated conditions, the sample quenched in deionized water took 73 s to cool down to 100 °C, while in the subcooled condition, the sample only took 13 s. At both saturated and subcooled conditions, 1% vol. boric acid solution accelerated the quenching rate and facilitated lowest film boiling time than other solutions considered. Conversely, film boiling time is higher when the sample is quenched in deionized water with 5% vol. of boric acid. The coolant temperature and additive concentration influence the film boiling time and Leidenfrost temperature, with a local build-up of boric acid concentration at the liquid–vapor interface being the governing mechanism.