GB629789A - Improvements in or relating to resistance thermometers - Google Patents

Abstract

629,789. Temperature-variable resistances. BAUER, S. G. Dec. 1, 1947, No. 31654. [Class 37] A resistance thermometer for flowing fluids comprises a thin-walled metal tube, extending between inlet and outlet pipes or pipe-couplings, a resistance winding embedded in the outer surface of said tube in heat-conducting, electrically-insulating relation thereto, and a plug within said tube defining with the tube an annular passage co-extensive with the winding and of cross-sectional area substantially smaller than that of the inlet and outlet pipes or couplings. As shown, the tube 8 extends between pipe couplings 9 carrying flanges 10 by means of which the thermometer is inserted into the pipe line 19, 20 and flanges 11 to which is secured the casing 13 protecting the resistance winding 22. The winding is wound in an external thread of the tube 8, the thread having a root conforming in shape to the wire of the winding. The winding may be of bare or varnished wire and the tube of anodized aluminium. The plug is constituted by two metal tubes 15 having their inner ends cupped and secured by a bolt 17 serving also to clamp the pipe couplings and the tube 8 together, and having slots 16 in their walls, through which the flow is diverted into the annular passage between the tube 8 and the tubes 15, the slots also increasing the turbulence of the fluid in flow. The couplings 9 are shaped as shown, so that the internal diameter of the tube 8 exceeds the effective diameter of the pipe couplings, the increased area of heat contact between the fluid and the tube 8 and the increased velocity and turbulence of the fluid in the annular passage increasing the quickness of response of the thermometer to changes in temperature.