2.2.2. Measurement of the temperature distribution in the boundary layer
It DL-TBOA important for the study of NuφNuφ to measure the temperature distribution in the boundary layer around the cylinder. In the present study, a specially designed micro-thermocouple is employed to measure the temperature distribution at different angles φφ and spaces to the surface of the cylinder yy (see Fig. 2).
Fig. 2. Schematic of the micro-thermocouple.Figure optionsDownload full-size imageDownload as PowerPoint slide
The micro-thermocouple can be revolved from 0° to 360° around the cylinder axis. The diameter of thermocouple wire is 0.05 mm and the one of welded spot is about 0.1 mm so root system the influence on the temperature boundary layer is negligible. In order to reduce the heat conduction along the thermocouple wires and decrease the measurement error, the micro thermocouple is placed in the form of ∏ and parallel to the cylinder.
During the measuring process, the cold end of micro-thermocouple was put into the mixture of ice and water, and the thermoelectromotive force was obtained by a data collecting instrument and stored in a computer.