HEAT TRANSFER FROM HIGH-TEMPERATURE SURFACES TO FLUIDS III – CORRELATION OF HEAT-TRANSFER DATA FOR AIR FLOWING IN SILICON CARBIDE TUBE WITH ROUNDED ENTRANCE, INSIDE DIAMETER OF 3/4INCH AND EFFECTIVE LENGTH OF 12 INCHES

摘要

A heat-transfer investigation was conducted with air flowing through an electrically heated silicon carbide tube with a rounded entrance, an inside diameter of 3/4 inch, and an effective heat-transfer length of 12 inches over a range of Reynolds numbers up to 300,000 and a range of average inside-tube-wall temperatures up to 2500° E. The highest corresponding local outside-tube-wall temperature was 3010° R.nCorrelation of the heat-transfer data using the conventional Nusselt relation wherein physical properties of the fluid were evaluated at average bulk temperature resulted in a separation of data with tube-wall-temperature level. A satisfactory correlation of the heat-transfer data was obtained, however, by the use of modified correlation parameters wherein the mass velocity G (or product of average air density and velocity evaluated at bulk temperature PbVb) in the Reynolds number was replaced by the product of average air velocity evaluated at the bulk temperature and density evaluated at either the average inside-tube-wall temperature or the average film temperature;in addition, all the physical properties of air were correspondingly evaluated at either the average inside-tube-wall temperature or the average film temperature .