Effects of Ultrasounds on the Heat Transfer Enhancement From a Circular Cylinder to Distilled Water in Subcooled Boiling

Abstract

The main aim of this work is to investigate experimentally the influence of ultrasonic waves, on the heat transfer enhancement, from a stainless steel circular cylinder to distilled water, in subcooled boiling conditions. This study has carried on for a few years at the Department of Energetics “L.Poggi.” The effect was observed since the 1960s: Different authors had investigated the cooling effect due to the ultrasonic waves at different heat transfer regimes, especially from a thin platinum wire to water. They had found out that the highest heat transfer coefficient enhancement was in subcooled boiling conditions. So this paper has the purpose to clarify the physical phenomenon and optimize a large range of variables involved in the mechanism. It reports the experimental results obtained with ultrasound at the frequency of 38 kHz, at two different subcooling degrees, ΔTsub=25°C and 35°C. The heat fluxes applied on the cylinder, the ultrasonic generator power Pgen, and also the placement of the heater inside the ultrasonic generator tank were varied. The ultrasonic waves seem to be very useful for a practical application in the last generation electronic components’ cooling: They need dissipating huge heat fluxes and avoiding high temperatures (≈150°C), after that they could damage themselves.