Numerical study of saturated boiling heat transfer over the flat and curved surfaces

Abstract

AbstractIn boiling phenomena, the heater surface gets covered by a vapor, which results in a decrease in the overall heat transfer coefficient (HTC). The curvature of the surface helps to reduce this vapor blanketing by vapor sliding over the curved surface. The sliding generates fluid circulation and makes the heater surface available for boiling liquid. Therefore, in the present work, the vapor dynamics, nucleation and growth, pinch‐off of the bubble, and heat transfer characteristics over smooth and uniform surfaces with different curvature ratios (δ = 0, 0.01, 0.05, 0.15, and 0.25) are numerically studied. Also, the effect of the degree of superheat (ΔT = 10, 20, 30, and 40 K) on the bubble formation, vapor sliding, and fluid recirculation over the curved surface have been observed. Furthermore, investigated the dome formation and multiple pinch‐off of the bubble on the heated curved surfaces. The dominance of the curvature and degree of superheat on the bubble departure has been investigated using PDF of FFT of vapor void fraction at the surface. At higher curvature of the surface, there is less significance of the degree of superheat on the departure frequency of vapor bubbles. Furthermore, it is found that there is an increase in the average HTC with an increase in the curvature ratio, while the pinch‐off time of the bubble decreases. The HTC is enhanced by 86% with curved surfaces as compared to flat surfaces. Furthermore, the curved surface with a curvature (δ) of 0.15 showed better performance than the curved surface with δ = 0.25. Boiling over a curved surface leads to vapor sliding and recirculation of the fluid, leading to enhancement in surface renewal and an increase in HTC.