GB667171A - Improvements in or relating to temperature control apparatus for furnaces or other high temperature heating chambers - Google Patents

Abstract

667,171. Heat - transmitting media. BROWN, S. J., and WAIGHT, J. F. Dec. 3, 1949 [Nov. 6, 1948], No. 28871/48. Class 64(ii) In apparatus for controlling the temperature of a furnace or other chamber, e.g. a retort, kiln, muffle or oven, which operates at a temperature above 1500‹F. a heat transferring fluid such as oil, water or a gas flows continuously through a member 12 subjected either to the heat in the furnace or to the heat radiated by a workpiece and then flows over a thermal element 15 mounted externally of the furnace and controlling the fuel or power supply to the furnace or to the succeeding furnace of a series of furnaces. The thermal element operates at a temperature not exceeding 800‹F. and may be a thermocouple, thermopile or bimetal. As shown, the heat-transmitting fluid is circulated by a pump 11 through a conduit loop 12, e.g. of steel, copper or brass, in the furnace and.after passing over the thermal element returns by way of a cooler 16 to a reservoir in which the fluid is preheated and kept at a controlled temperature. A switch 25 operated by the thermal element 15 controls solenoid-operated relay valves 22, 23 which regulate the supplies of air and gas respectively to a burner 19. In a modified arrangement, a thermosiphonic circulation is set up by a raised reservoir with a long communication for natural cooling, to a heat-receiving member which forms part of the furnace wall. The device may be applied to furnaces arranged for series flow of workpieces so that one or more of the furnaces are controlled by the temperature of the preceding furnace or of the workpiece emerged therefrom. If air is used as the heat-transmitting fluid, after passing over the thermal element it may discharge to atmosphere or be used as preheated air for the gas burners. Specifications 633,698 and 636,953 are referred to.