Patent ID: 6484795
Filing Date: 2002-11-26
Classification: F28F,Y10T

Abstract:
An integral ceramic insert for a radiant tube, wherein said integral ceramic insert has a substantially helical shape, and wherein:(a) said integral ceramic insert is comprised of at least 40 volume percent of a material selected from the group consisting of silicon, silicon carbide, silicon nitride, and mixtures thereof, (b) said integral ceramic insert has a thermal expansion rate of less than 6.0Ã—10âˆ’6 meters/meter/degree Celsius, (c) said integral ceramic insert has a thermal conductivity, at a temperature of 25 degrees Celsius, of at least 0.2 calories/centimeter/second/degree Celsius, (d) said integral ceramic insert has a diameter of from about 2 to about 10 inches and a length such that the ratio of said length to said diameter of said integral ceramic insert is from about 2/1 to about 8/1, (e) said helical shape is comprised of one or more pitches of from about 2 to about 32 inches, each which defines a helix angle of from about 15 to about 80 degrees, provided that there is from about 0.5 to about 8 inches of pitch per inch of diameter of the integral ceramic insert, and (f) said ceramic insert has a cross-sectional shape defined by a centerpoint and extending radially outwardly therefrom at least one wing.