| 摘要 |
499,623. Electric heating resistances. NAAMLOOZE VENKOOTSCHAP MOLYBDENUM CO. March 22, 1938, No. 8742, Convention date, July 22, 1937. [Class 39 (iii)] A heating element for an electric furnace comprising a metallic or non-metallic conductor surrounded by a sheathing of heat insulating ceramic material impervious to gas is characterized in that the thickness of the sheathing is such that the fall in temperature therein does not exceed 70‹ C. In a concentric arrangement of the heating conductor and sheathing the maximum thickness of the sheathing is dimensioned according to the rule d being the thickness of the envelope in centimetres, r, the conductor radius in cms., A the coefficient of heat conductivity of the sheathing in cal. /cm., q the specific electric load in cal. /cm. In the case of strip-shaped conductors from which heat is emitted on both sides, the maximum thickness of the sheathing is calculated according to the rule b being the width of the conductor in centimetres, and d, #, q q representing the same quantities as above. |
