A CONTACT METHOD FOR SIMULTANEOUS MEASURING THE LIQUID FILM THICKNESS AND TEMPERATURE

We present a contact method for local measurements of liquid film thickness and temperature. The sensing element is a microthermocouple with flat bead working on the Seebeck effect. The bead size of the manufactured thermocouple is less than 3 mu m. A special software is developed which synchronizes microthermocouple readings and the motorized stage position, allowing automatic determination of the thickness of the liquid layer. The interface position is determined as a position of abrupt change in temperature. In some cases this measured temperature difference corresponds to the temperature jump value. In the case of the absence of a temperature difference, the interface position is determined from the difference in temperature gradients, from the so-called fracture of the temperature profile at the interface that occurs due to the difference in thermal conductivity between the gas and the liquid. Four different types of liquid, H2O, C2H5OH, CH2I2 , and HFE-7100, are used in the experiments. This technique simultaneously provides data on the local film thickness and temperature profile, including the temperature value at the liquid-gs interface, using one instrument. Our measurements are in excellent agreement with the measurements by the shadow method. The method can be adopted for measurements of void fraction in two-phase flow. In the case of the existence of measurable temperature jump the thermal resistance of the liquid-gas interface can be estimated.