Heat transfer in supercritical fluids under pulse heating regime

Heat transfer under high-power heating of liquids. 3. Threshold decrease of heat conduction in supercritical region

“…In the second paper, by the example of water we discussed the phenomenon of threshold decrease in the intensity of heat transfer in the course of transition of the substance from the initial stable state (with the temperature T 0 < T c and the pressure value p > p c ) into supercritical state (T > T c ) along the isobar [2], where subscripts ''0'' and ''c'' refer to an initial state and a critical point, correspondingly. This phenomenon was previously revealed for organic liquids as well [3,4]. The penetration into supercritical region was implemented so rapidly (probe heating rate was 10 4 -10 5 K/s) that the convective component of heat transfer did not have time ''to be switched on'' and the parameters of the response signal were reliably reproduced in a series of successive pulses.…”

“…The penetration into supercritical region was implemented so rapidly (probe heating rate was 10 4 -10 5 K/s) that the convective component of heat transfer did not have time ''to be switched on'' and the parameters of the response signal were reliably reproduced in a series of successive pulses. The characteristic pulse length of the probe heating within the technique of constant power was of the order of milliseconds; the characteristic heating layer thickness was of the order of micrometers [1][2][3][4].…”

Heat transfer under high-power heating of liquids. 1. Experiment and inverse algorithm

“…Experimental results are obtained using a constant heating power mode [9,10]. The method implements electrical power control directly during the pulse.…”

“…, 2 cm. As usual [3][4][5][6][7][8][9][10][11][12], probe combines functions of both a heater and a resistance thermometer. Standard reference table for platinum thermometers is implemented for resistance-to-temperature conversio n. A relative version of the method was applied.…”

“…This motivated the developmen t of the probe pulse heating method combined with numerical simulation of heat transfer parameters based on the experimental results. The key feature of our approach is electronic control of the probe heating power against a background of the thermophysical propertie s variation s with the temperature of both probe and substance [9][10][11]. An advanced variant of the electroni c control system for quasi-static conditions (with respect to the temperat ure) is described elsewhere [12].…”