Experimental Investigation of Effect of a Surfactant to Increase Cooling of Hot Steel Plates by a Water Jet

摘要

The requirement for high tensile strength steel has placed greater emphasis on the cooling methods used in the cooling of a hot steel plate. The purpose of this research is to study the effect of surfactant concentration in water jet cooling, and its applicability in the study of ultrafast cooling (UFC) of a hot steel plate. The initial temperature of the plate, before the cooling starts, is kept at 900 ℃ which is usually observed as the "finish rolling temperature (FRT)" in the hot strip mill of a steel plant. The current heat transfer analysis shows that surfactant added water jet produces higher heat flux than the pure water jet due to the higher forced convection cooling area. Dissolved surfactant increases the transition boiling heat flux, nucleate boiling heat flux and critical heat flux. At a concentration of 600 ppm, the maximum surface heat flux has been observed and further increase in surfactant concentration decreases the surface heat flux. The surface heat flux and the cooling rate show an increasing trend with the increasing water flow rate at a constant surfactant concentration. The achieved cooling rate in case of surfactant added water is almost twice that of jet with pure water, resulting in ultrafast cooling. By assuming the impinging surface consists of three different constant heat flux regions, the surface heat flux and the surface temperatures have been calculated by using intemp software.