LOCAL HEAT (MASS) TRANSFER IN A ROTATING SQUARE CHANNEL WITH EJECTIONHOLES

The objective of this experimental investigation was to examine the ef fects of rotation, now ejection, channel orientation, and transverse r ibs on the local heat (mass) transfer distribution for radial outward flow in a square channel, rotating about a perpendicular axis. The tes t channel was oriented so that the direction of rotation was perpendic ular or at a 45 deg angle to the Leading and trailing walls. There wer e eight ejection holes along the leading or trailing wall of the test channel. The diameter of each ejection hole was equal to one-fifth of the channel hydraulic diameter. The wall with the ejection holes was e ither smooth or roughened with seven transverse ribs. The ribs were lo cated midway between two ejection holes. The height of the ribs was eq ual to one-tenth of the channel hydraulic diameter, and the spacing be tween two ribs was equal to 10 times the rib height. The Reynolds numb er was 5.5 x 10(3) and the rotation number range was between 0.0 and 0 .24. In a smooth normally oriented channel, rotation in the direction of the ejection flow significantly reduced the local heat/mass transfe r on the Leading wall, except in the vicinity of the ejection holes. R otation in a direction opposite to that of the ejection flow widened t he high heat/mass transfer regions near the ejection holes on the trai ling wall, and reduced the heat/ mass transfer in the regions between the ejection holes, In a smooth diagonally oriented channel, the trend of higher heat/mass transfer near the leading side of the Leading wal l rather than near the trailing side was the opposite of the expected trend for the radial outward now through a smooth diagonally oriented channel with no ejection holes, Flow reattachment downstream of transv erse ribs and now acceleration toward ejection holes together caused v ery high heat/mass transfer in bell-shaped regions around the ejection holes. Rotation changed the shape of the local heat/mass transfer dis tribution more on the leading wall than on the trailing wall of a rib- roughened diagonally oriented channel.