Correlation for Flow Boiling Heat Transfer at Low Liquid Reynolds Number in Small Diameter Channels

摘要

In view of significance of a heat transfer correlation of flow boiling under the conditions of low liquid Reynolds number or liquid laminar flow, and very few correlations in principle suitable for such flow conditions, this study is aiming at developing a heat transfer correlation of flow boiling at low liquid Reynolds number for small diameter channels. The correlation is developed based on superimposition of two main flow boiling mechanisms, namely nucleate boiling and forced convection. In the correlation, two terms corresponding to nucleate boiling and forced convection are obtained from the pool boiling correlation by Forster and Zuber and the analytical annular flow model by Hewitt and Hall-Taylor, respectively. An extensive comparison with a collected database indicates that the developed correlation works satisfactorily with mean deviation and rms errors of 19.1% and 24.3%, respectively, under many experimental conditions such as different channel geometries (circular and rectangular) and flow orientations (vertical and horizontal) for some test fluids (water, R11, R12, and R113). A detailed discussion reveals that existing correlations for turbulent flow boiling such as Chen's correlation, Schrock and Grossman's correlation, and Dengler and Addoms's correlation may be derived from a generalized form of the newly developed correlation.