Boiling heat flux prediction for real nucleate boiling using bubble dynamics simulation for single-bubble nucleate boiling

초록

To transfer a large amount of thermal energy under a limited temperaturecondition, nucleate boiling heat transfer is used in diverse applications. However, due to the large density ratio between the liquid and gas phases, the interfacial motion of numerous bubbles is very irregular. The large latent heatcauses a large thermal discontinuity at the phase interface. Thus, the reliability of continuum-mechanics based CFD simulation has always been suspected. However, in the case of single-bubble nucleate boiling, where the motion of the phase boundary is relatively simple, numerical results from different researchers have shown good consistency and excellent agreement with experiments. Using bubble dynamics variables such as bubble departure diameter and frequency obtained from a CFD simulation of the single-bubble nucleate boiling, the present study predicts the boiling heat flux for actual nucleate boiling involving many randomly nucleated bubbles. The wall superheat-heat flux relationship has been successfully obtained for various fluids including water and HFE fluids up to a wall superheat of 25 degrees. With the acceleration of electrification and digitalization, various new refrigerants are being launched one after another. The present study would be a useful tool for evaluating the nucleate boiling characteristics of new fluids prior to experimentation.

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