HEAT TRANSFER INVESTIGATION IN A SMOOTH ROTATING CHANNEL WITH THERMOGRAPHY LIQUID CRYSTAL

An experiment investigation was conducted in a smooth cooling channel under rotating conditions on a new rotating facility. The heat transfer phenomenon of rotating channel with constant heat flux boundary conditions was measured using PIV and TLCs (Thermography Liquid Crystal). The square cross-section channel is manufactured from Plexiglas. Four 1 mm thick transparent ITO (Indium Tin Oxide) heater glasses taped on four Plexiglas walls independently to provide the same constant heat flux boundary conditions. The size of the heated channel is 600 mm*80 mm*80 mm. TLCs was used for measuring the two-dimensional detail distribution of the temperature on the leading surface and trailing surface of the channel. The pixel-level calibration method was used for reducing the error of the TLCs. In the experiments, the Reynolds number, based on the channel hydraulic diameter(D) of 80 mm and the bulk mean velocity, is 20000, and the rotation number are 0, 0.068, 0.135, 0.205, 0.273, respectively. The obtained result shows that rotation has an important different effects on the heat transfer of leading and trailing side. On the trailing side, the heat transfer increases with the rotation number monotonically along the stream wise (X direction), and rotation enhances the local Nu/Nu(s) up to 20%. On the leading side, rotation weakens the Nu/Nu(s) around 25% with the rotation number of 0.273. However, on the leading side, with the increase of rotation number, the Nu/Nu(s) is not decreasing monotonically along the stream wise, there is a slight enhancement (turning point) along the stream wise with different rotation numbers. The position of turning point on the leading side is different with various rotation numbers. With higher rotation number, the turning point moves closer to the inlet of the channel. This phenomenon is an important reference to investigate the flow field in our future work with PIV. More details of two-dimensional distribution Nu on the leading and trailing side will be shown in this work.