Temporary Foam Coating Increasing the Cryogenic Quenching Efficiency
Abstract - Experiments are described, which establish enhanced boiling conditions during quenching by use of temporary heat transfer enhancer at cryogenic temperature range in liquid nitrogen. Foam coating based on surfactants were used as temporary heat transfer enhancer. These coatings make it possible to reduce and even eliminate the film boiling regime and significantly shorten the transition to nucleate boiling regime which provides an increase in heat flux. It is established that heat transfer intensity by use of foam coating may be adjusted by means of coating structure characteristics change. The influence of water concentration in foam on foam structure characteristics was determined. The structure of the temporary coating was characterized using scanning electron microscope(SEM) technique .It was found that there is a dependence of the heat flux as a result of the characteristics of the formed foam coating. Calculation of median integral heat flux increase by quench for SAE 1045 cylinder with 30 mm in diameter and 200 mm in length shows up to 4.6 times in heat flux increase of coated compare to an uncoated specimen. The results may be used for development of temporary heat transfer enhancing technologies.
Keywords - Cryogenic quenching, Foam, Heat flux enhance, Pool boiling, Temporary porous coating.