Abstract
A drop impingement on a hot surface is known as an effective way for heat removal. The present work uses a VOF (volume of fluid) model to simulate the flow behavior and temperature distribution on a 50 °C heated plate while relatively cold water drop is impinging. The temperature distribution at the impingement zone is used to examine the transient heat transfer coefficients using a single drop and double drops conditions. The spreading factor is tested in both cases. A test rig is built to verify the temperature distribution and a heat balance method is introduced to find the experimental heat coefficients on the heated. The CFD solution and its flow results gives a good agreement for single drop previous results. The results for the double drop condition show a high tendency for rebound and splash of the drop leaving the central zone without water drop coverage which way causes a burn out in case of high heat fluxes. The single drop condition show a symmetrical temperature and heat transfer coefficients distribution while the double drop impingement gives lower value of coefficients with non-uniform and unsymmetrical distribution specially at the bigger drop to plate distances. The experimental average heat coefficients gives relatively low error of only 5% in case of double drop when compared to the single drop values.
Highlights
Drops impingement a promising mechanism for enhancing heat transfer
The point on which the drop impact will be under the effect of convection in the zone of water drop impact while the unexposed points are assumed exposed to an air of with natural convection, the temperature variations are small
Experimental Results: Experimental work was conducted in order to examine the effect of single drop of 3mm diameter of water at temperature of 25 °C impact on a heated plate made of stainless steel with thickness of 0.55mm and at relatively higher constant temperature of 50 °C
Summary
Drops impingement a promising mechanism for enhancing heat transfer. Drop effect happens if a drop of liquid hits a surface of solid. If a drop of liquid hits a desiccated surface of solid, first it will in general spread over this surface, and after that it will retract when the effect being sufficiently active for causing the drop to expand out further than it would in general propagate owing to its static retreating angle of contact. The droplet that hits a liquid interface can show a Superhydrophobic-like Bouncing, featured via the coefficient of restitution not depending on the characteristics of the underlying liquid, the contact time and the spreading dynamics [8]. The geometrical path is air whose dimensions consist of a length that varies according to the heights, the nozzle from which one or two drops of flow forms on the surface of the plate. The mentioned thickness is used on the suitable plate thickness available in the market
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