On the Characterization of Heat Transfer Rate in Various Boiling Regimes Using Quenchometers and Its Application for Quenching Process Simulations

When an overheated metal is submerged in quenchant, the liquid in contact immediately vaporizes and a thin film is formed, significantly reducing heat extraction rate of the metal. This is referred as Leidenfrost effect and the minimum temperature this phenomenon occurs is defined as Leidenfrost point (LFP). The heat transfer rate occurs at LFP is defined as minimum heat flux (MHF). Once the temperature drops below LFP, the liquid boiling regime changes from film boiling to transition boiling and heat transfer rate increases, until it reaches heat transfer limit defined as critical heat flux (CHF). After passing CHF, the liquid boiling regimes changes to nucleate boiling and the heat transfer eventually reduces to convection heat transfer below liquid boiling point. The heat transfer characteristics in each boiling regimes are of great interest to heat treatment industry in order to design better equipment or to optimize the quenching processes. In this paper, we conclude from literature research that heat transfer characteristics of each boiling regimes can be approximated by LFP, MHF and CHF plus properties of interacting phases of the quenchant. In addition, we develop a standard procedure using quenchometer to find LFP, MHF and CHF, as they are very much process dependent and must be determined first for future engineering tasks. Finally, we utilize the findings, in conjunction with a commercial CFD software, to simulate the quenching process, calculate temperature history and compare the result with thermocouple readings.