The understanding of coalescence phenomenon is important for designing a spray cooling system, manufacturing paint and varnish products and making an anti-icing system in aviation.
A liquid cooling spray system, when a liquid film is formed as a result of a directed flow of drops and partially or completely wets the heating surface, is one of the most promising cooling systems. Accordingly, there is a need for a deeper study of the dynamics of heat transfer when drops fall on a solid surface and merge. This is a complex phenomenon because of the presence of different factors such as surface tension, wettability, surface geometry, etc.
To determine the heat flux during spray cooling in the area of the contact line of drops or during the formation of a liquid layer, the thin foil method (25 µm) is used. Constantan foil is fixed between two brass electrodes. Foil size of length 80 mm and width 35 mm. A power source is connected to the foil and the power released on the foil is regulated. The liquid drop is introduced to the foil using a metal needle and syringe pump. A drop is placed on one side of the foil, and the other side of the foil is covered with black paint. Using the Flir Titanium 540 IR scanner, this side of the foil is photographed. The side-walls are assumed adiabatic and the electrical power is measured by the power supply. The Cauchy problem for the Laplace equation of general form is one of the well-known ill-posed problems and its solution is unstable. The instability of the solution of the Cauchy problem becomes apparent when using any numerical method for solving it. In this paper, we used a method that reduces the solution of the Cauchy problem to the solution of the problem of moments. The process of coalescence of vertical drops over the heated thin foil is investigated.