Derivation of a Look-Up Table for Trans-Critical Heat Transfer for Water-Cooled Tubes

Abstract

A trans-critical look-up table (LUT) provides predictions of heat transfer for the region near and beyond the critical point for water. The trans-critical LUT starts at the high subcritical pressure of 19 MPa and extends to supercritical pressures, up to 30 MPa. The intended range of application of the LUT is sufficiently wide to fit all conditions for which conventional single- phase correlations do not apply. This article describes the progress made in deriving a trans- critical LUT for tubes cooled by vertical upflow of high-pressure water. The University of Ottawa (UO) team has compiled a large trans-critical water database and combined it with supercritical water (SCW) databases from other organizations. The expanded database has been carefully examined and duplicate data as well as obvious outliers and data not satisfying a heat balance have been removed. The expanded UO database includes more than 25,000 screened data points. A literature review has been performed in parallel with the LUT compilation and has identified 18 single-phase, near-critical and supercritical (SC) heat transfer correlations. The predictions of these correlations have been compared to the experimental values of the UO expanded database and a statistical error analysis of the comparison results has been performed. The parametric trends of the uncertainty of the more promising correlations are described in this paper. A skeleton LUT has been constructed in which the heat transfer coefficients are assumed to be unique functions of pressure, mass flux, heat flux (or surface temperature) and fluid enthalpy; the LUT domain has been subdivided into sub-domains, each associated with a distinct heat transfer mechanism. The sub-domains include high pressure subcritical regions (liquid, subcritical vapor, and subcritical two-phase regions), SC regions (high-density state or SC liquid-like region, and low-density state or SC vapor-like region) and a near-critical or near-pseudo-critical region. For each region, the best correlations were identified and subsequently used for the construction of the skeleton LUT, which will be updated by experimental data suitably normalized. The parametric trends of the skeleton table have been examined and compared to experimental data.