Angular Dependency on Film Boiling Heat Transfer From Relatively Long Inclined Flat Plates

Abstract

The ejfect of inclination angle of the downward facing flat plate on the interfacial wavy motion is investigated utilizing the water quenching test apparatus downward ebullient laminar transition apparatus flat surface (DELTA-FS) in a quasi-steady state. Film boiling heat transfer coefficients are obtained on the relatively long surface in the flow direction. Interfacial velocities at the various inclination angles and wall superheat conditions are determined through the analysis of the visualized continuous snapshots with 1000 fps. Visualization of the vapor film reveals that the interfacial wavelength increases and the interfacial velocity decreases as the flat plate moves from the vertical to downward facing locations. A new semi-empirical correlation is developed from the measured heat transfer coefficients and interfacial velocities. The correlation shows good agreement with the previous water test results on vertical plates. In the case of the previous other fluid experimental results on the vertical plates, the correlation overpredicts the film boiling heat transfer coefficients at the experimental condition.

Inclination dependence of planar film boiling stability

“…In Sec. 6 we compare predictions from the stability analysis with certain experimental measurements by Kim and Suh (2013). Finally, the important messages of the present study are summed up in Sec.…”

“…A steady-state solution with the properties h ∼ x 1/4 and h ∼ a −1/4 has been presented before by authors such as Nishio and Chandratilleke (1991) and Kim and Suh (2013). However, Eq.…”

“…There are few works on film boiling considering the effect of inclination away from the vertical. Examples are Nishio and Chandratilleke (1991) and Kim and Suh (2013).…”

“…The goal is to achieve this analysis with a relatively simple model, in order to gain insight and practically useful expressions. While Kim and Suh (2013) consider the inclination dependence of film boiling stability, the actual onset of instability in their model is given by the critical Reynolds number, an empirical parameter that is fitted to the experiments. The present work avoids any free empirical parameters, and thus offers ab initio predictions on stability.…”

“…Unfortunately there are few experimental works studying the influence of inclination on film boiling stability. However, one such study was published by Kim and Suh (2013), which included indirect approximate measurements of the maximum stable film thickness for water film boiling. The principle behind the measurements is as follows: A planar film boiling experiment is performed with a plate much longer than the characteristic wavelengths of instability.…”