Heat transfer during cavitation bubble collapse

Abstract

Cavitation phenomenon has found various industrial applications. The collapse process of a cavitation bubble is extremely violent in its final stage and the gas within the bubble can become extraordinarily hot. This paper introduces a heat transfer model to calculate accurately the temperature change and heat transfer during a bubble collapse based on the Rayleigh–Plesset (RP) equation and CFD modelling. To demonstrate the variations of pressure, temperature and velocity distribution in the liquid and bubble, a two-phase compressible CFD model developed to simulate the process of the bubble collapse. Results from the RP equation – modified with conduction and radiation effects – match the numerical CFD results very well. Further investigations were carried out on the bubble collapse and temperature increase, heat transfer rate by conduction and radiation, and accumulative heat transfer of bubbles with different bubble sizes. When a cavitation bubble with initial maximum radius of 2 mm collapses, the maximum temperature of the air can rise up over 0.02 mega degrees Kelvin (MK) and the transferred heat by radiation and conduction accumulated in the first cycle of collapse can reach 40 micro-joules (µJ). The solution to the modified RP equation provides a practical method for the estimation of heat transfer and temperature increase in cavitation equipment.