Electrical resistance heating element for a heating device for heating a flowing gaseous medium

Abstract

An electrical resistance heating element for a heating device, with at least one flow canal through which the gaseous medium is able to flow from a canal inlet side to a canal outlet side of the resistance heating element, and with at least one heating resistor that extends essentially in the direction of the flow canal, with the medium flowing past the heating resistor and being heated in the process. The heating resistor is rod-shaped and produced from an electrically conductive ceramic material. The electrical resistance heating element is intended for installation in a heating tube into which air, for example, is blown at one end. The heated flow of air exits from the other end of the heating tube.

1 . An electrical resistance heating element for heating a gaseous medium, with at least one heating resistor that extends essentially in the longitudinal direction of the electrical resistance heating element, with the medium flowing past the heating resistor and being heated in the process, and with at least one flow canal that extends along the heating resistor and through which the medium is able to flow from a canal inlet side to a canal outlet side of the resistance heating element, with the heating resistor comprising an electrically conductive ceramic material for conducting the current, wherein
 the heating resistor is rod-shaped and is held by carrier plates that are located at the canal inlet side and the canal outlet side of the resistance heating element, with the flow canal continuing in said carrier plates, and with the heating resistor positively engaging the carrier plates at its ends.   
   
   
       2 . A resistance heating element as claimed in  claim 1 , wherein the conductive ceramic material has a specific resistance of between 0.01 and 1.0 Ω-cm. 
   
   
       3 . A resistance heating element as claimed in  claim 1 , wherein the ratio of the length to the cross-sectional area of the ceramic material of the heating resistor ranges between 1 and 500 cm −1 . 
   
   
       4 . A resistance heating element as claimed in  claim 1 , wherein the heating resistor is essentially U-shaped. 
   
   
       5 . A resistance heating element as claimed in  claim 1 , wherein the carrier plates are formed from an electrically non-conductive ceramic material. 
   
   
       6 . A resistance heating element as claimed in  claim 1 , wherein the carrier plates have recesses that match the cross-sectional shape of the heating resistor and serve to accept the ends of the heating resistor, and also have passages through which the flow of the gaseous medium is able to pass. 
   
   
       7 . A resistance heating element as claimed in  claim 1 , wherein the heating resistor is positively connected to the carrier plates. 
   
   
       8 . A resistance heating element as claimed in  claim 1 , wherein the heating resistor has indentations and/or raised areas in order to enlarge its surface for the contact with the flow of the gaseous medium, in comparison with a flat surface. 
   
   
       9 . A resistance heating element as claimed in  claim 1 , wherein the conductive ceramic material is a mixed ceramic material with a conductive and a non-conductive component, with the conductive ceramic component having a positive thermal coefficient, and with molybdenum disilicide (MoSi 2 ) used as the conductive ceramic component, and aluminum oxide (Al 2 O 3 ) used as the non-conductive ceramic component. 
   
   
       10 . A heating device for heating a flowing gaseous medium, with an electrical heating element as claimed in  claim 1  surrounded by a heating tube positioned in a flow of the gaseous medium, with the flow being generated by a blower provided on the heating device or being provided from an external pressurized reservoir.