Apparatus for studying heat transfer in nanofluids under high-power heating

Abstract

A technique of electronic control of the probe heating power is developed using the method of controlled pulse heating of a wire probe, that is a resistance thermometer, was developed. An apparatus implementing this technique was fabricated. The characteristic parameters of the apparatus are as follows: the heating pulse length, 1 to 10 ms; the heat flux density through the surface of a 20 μm probe, 1 to 10 MW/m 2 ; repeatability of selected power value in a series of pulses is on a level of 0.05%. As an example, the constant heating power mode is applied for comparing the thermal resistance of nanofluids in the region of stable states of liquid and superheated (with respect to the liquid-vapor equilibrium temperature of the base liquid) ones. The parameter was the content of Al 2 O 3 nanoparticles in the base liquid (isopropanol).

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

“…Generally, the driving voltage parameters can be chosen arbitrarily. Based on our experience, a constant heating power mode generally works well for determination of thermophysical propertie s. Repeatability level, obtained in a series of pulses, was 0.05% [9]. Schemat ic diagram of the home-made experimental setup is shown on Fig.…”

“…Noise spectrum is flat random over the entire frequenc y range. As a result, data array is smoothed using the cubic spline [9]. This procedure can significantly improve the sensitivity of the method, without loss of informat ion in the recorded data.…”

“…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].…”