The Validity of Existing Pool Boiling Curve Models for Spheres in Nitrogen

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This experiment determined the validity of existing pool boiling curve models for spheres in nitrogen. We quenched copper, stainless steel and brass spheres of two different diameters in a pool of nitrogen. We created boiling curves comparing the temperature difference between the sphere surface and saturated nitrogen to the heat flux from the sphere. The curves were then compared to Rohsenow’s material dependent equation for nucleate boiling and other models to predict the minimum and maximum heat fluxes, independent of surface material. The relationship between heat flux and temperature change is different than the relationship found by Rohsenow, and is size and material dependent. We also found that maximum and minimum heat flux depends on material and radius. There is no correlation between thermal conductivity and heat transfer coefficient based on our findings; however, spheres with a larger diameter have larger maximum convection heat transfer coefficient.

INTRODUCTION

With knowledge of a pool boiling curve, it is possible to predict the amount of heat transfer induced by the boiling of a fluid. The level of heat transfer that can be obtained for engineering applications is highly dependent on the difference in temperature between the heating surface and the surrounding fluid. The shape of this curve is dependent on the shape of heating surface as well as the material properties of the heated surface and fluid. Both empirical constants and dimensionless numbers are used to form a boiling curve. Optimal operation conditions for an application can be predicted with the understanding of how different factors can shape the boiling curve [1].

Boiling curves are generally divided into four types of boiling: film, tra...

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