Features of Supercritical Heat Transfer at Short Times and Small Sizes

• Published in: International journal of thermophysics 2021-07, Vol.42 (7), Article 110
• Main Authors: Skripov, P. V., Rutin, S. B.
• Format: Article
• Language: English
• Subjects: Classical Mechanics; Condensed Matter Physics; Conductive heat transfer; Critical pressure; Critical temperature; Geophysics; Heat transfer; Heating; Industrial Chemistry/Chemical Engineering; Physical Chemistry; Physics; Physics and Astronomy; Thermodynamic equilibrium; Thermodynamics; Thermophysical properties
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-021-02869-y

In this article, we present new data on the non-stationary heat transfer in supercritical water at different heating regimes with characteristic times from 5 ms to 15 ms. The pressure, being the parameter of the experiment, was varied from the critical pressure p c up to 4.5 p/p c (namely, up to 1 kbar). These data serve as a significant addition to the well-known picture of supercritical heat transfer by phenomena inherent in the non-stationary case. The impetus for the study came from the discovery of an unexpected result observed in conductive heat transfer experiments under a powerful heat release—namely, the effect of a decrease in the intensity of heat transfer in the course of a rapid transition of the compressed fluid to the supercritical region of temperatures along the supercritical isobar. The observed effect, which exhibits a threshold character in the vicinity of the critical temperature, occurs up to pressures of 3–4 p/p c . The discussion is based on the hypothesis of a suppression of fluctuations by various external factors. It is assumed that under conditions of a short-term experiment, the complete thermodynamic equilibrium cannot be reached. This factor, along with the large temperature gradient and the presence of a heating surface, “cuts off” large-scale fluctuations responsible for the anomalous behaviour of thermophysical properties in the stationary conditions.