Fluid motion and heat transmission in a horizontal liquid laser heated locally from free surface

Heat transfer from a heated wire and a heated vertical plate, located just below a liquid surface, was studied experimentally. The curve representing the heat transfer coefficient as a function of the temperature difference between the heaters and a cooled tray could be divided into four parts. The range of each part depended strongly upon the size of the heaters, the depth of the tray and the liquid properties. The mechanism of heat transfer from the heaters in each part was discussed. The following observations were made. In the first part, where the temperature difference was the smallest, convective heat transfer was obscured by conduction. The heat transfer was mainly due to natural convection in the second part, and was mainly due to Marangoni convection in the fourth part. The third part could be considered as a transition regime. Furthermore, it was found that the transition was suppressed by the meniscus of the liquid surface which was in contact with the heaters.