A new heat transfer correlation for supercritical water flowing in a vertical tube - an hitherto approach

This paper provides an hitherto new approach of a heat transfer correlation based on heat flux to mass flux ratio for predicting wall temperature of supercritical water flowing in a bare vertical tube. Totally 10,174 numbers of experimental data were collected, Out of which 4236 data are heat flux/mass flux <= 0.4 and 5938 data are heat flux/mass flux>0.4. These data were obtained from various experimental resources and Lookup table and it covers q/G ranges from 0.085 to 1.295, mass flux ranges from 201 to 3500 kgm(-2) s(-1), heat flux ranges from 129 to 1600 kWm(-2), pressure ranges from 225 to 320 bar, diameter of the tube 4.4 to 38 mm and bulk fluid enthalpy ranges of 250 to 3200 kJkg(-1) of vertical tube working at various supercritical working conditions based on normal, enhancement and deteriorated heat transfer regions. By using these data, a new heat transfer correlation is derived for finding the wall temperature by Levenberg-Marquardt (LM) algorithm of multi dimensionless analysis method with Nonlinear curve fitting method. A general form of forced convection heat transfer correlation was obtained by Buckingham. theorem. The Wall temperatures predicted by various 7 existing correlations along with this new correlation are found by Visual basic program and compared with experimental data for evaluating the deviations. The rank was provided based on error band from +/- 0.5% to +/- 50% etc., and error analysis were conducted for proving the best fitting correlation.

Automated summary

This paper introduces a new heat transfer correlation based on the heat flux to mass flux ratio for predicting the wall temperature of supercritical water flowing in a bare vertical tube. By using various dimensionless analysis methods and a nonlinear curve fitting approach, a strong correlation for heat transfer was derived. Error analysis was conducted to evaluate and rank various existing correlations along with the new one, proving the best fitting correlation in the process.