Flow Through Heater

Abstract

An improved construction for a flow-through heater for heating water or other liquid and/or generating steam is disclosed. The flow-through heater has a cylindrical member formed from an inner tubular portion and an outer tubular portion that extends over a portion of the exterior surface of the inner tubular portion. The outer tubular portion houses a plurality of heating elements, which can be electrically connected in series or in parallel, thus providing more control over the heat distribution from the heater to the fluid flowing through it.

1 . A flow-through heater comprising:
 an inner tubular portion extending along a longitudinal axis and including an exterior surface;   an outer tubular portion extending over the exterior surface of the inner tubular portion;   a plurality of heating elements contained in the outer tubular portion and extending generally longitudinally along the exterior surface of the inner tubular portion, the plurality of heating elements forming part of an electric circuit;   each heating element comprising an elongated metal sheath, a coiled resistance wire extending coaxially along the length of the elongated metal sheath, and an electrically insulating material disposed between the elongated metal sheath and the coiled resistance wire; and   wherein each heating element is configured to form an intermediate section and a pair of leg sections extending from opposite ends of the intermediate section; and   wherein the exterior surface of the inner tubular portion is selectively heated by powering at least a portion of the plurality of the heating elements ON and OFF.   
   
   
       2 . The flow-through heater of  claim 1  wherein the outer tubular portion includes at least one of receptacles and fins for receiving the plurality of heating elements, wherein the receptacles and fins extend longitudinally and the fins project radially outwardly from the longitudinal axis. 
   
   
       3 . The flow-through heater of  claim 1  wherein the coiled resistance wire has a pitch that varies along the length of the heating element. 
   
   
       4 . The flow-through heater of  claim 1  wherein at least a portion of the plurality of heating elements are powered ON and OFF separately from the remainder of the plurality of heating elements. 
   
   
       5 . The flow-through heater of  claim 1  wherein the plurality of heating elements are electrically connected in parallel. 
   
   
       6 . The flow-through heater of  claim 1  wherein the plurality of heating elements are electrically connected in series. 
   
   
       7 . A flow-through heater comprising:
 a cylindrical member extending generally along a longitudinal axis and comprising an inner tubular portion and an outer tubular portion that extends over an exterior surface of the inner tubular portion; and   a plurality of heating elements positioned at locations around the circumference of the outer tubular portion and extending generally longitudinally along the exterior surface of the inner tubular portion, the plurality of heating elements being electrically connected to one another.   
   
   
       8 . The flow-through heater of  claim 7  wherein the cylindrical member comprises a single-component construction, the inner tubular portion and the outer tubular portion being constructed from a single piece of material. 
   
   
       9 . The flow-through heater of  claim 7  wherein the cylindrical member comprises a two-component construction, the outer tubular portion being attached to the inner tubular portion by at least one of a taper fit, an interference fit, a wedge, brazing or a thermal epoxy. 
   
   
       10 . The flow-through heater of  claim 7  wherein the outer tubular portion comprises a plurality of receptacles for receiving the plurality of heating elements. 
   
   
       11 . The flow-through heater of  claim 7  wherein the outer tubular portion comprises a plurality of fins extending radially and outwardly from the longitudinal axis, and wherein the plurality of heating elements are located between adjacent fins. 
   
   
       12 . The flow-through heater of  claim 11  wherein the plurality of heating elements are attached to the plurality of fins. 
   
   
       13 . The flow-through heater of  claim 7  wherein the plurality of heating elements each have a U-shaped construction and include a pair of leg sections and an intermediate curved section. 
   
   
       14 . The flow-through heater of  claim 13  wherein at least some of the plurality of heating elements have a wattage that varies along its length. 
   
   
       15 . A flow-through heater comprising:
 a cylindrical member extending generally along a longitudinal axis, the cylindrical member comprising an inner tubular portion and an outer tubular portion that extends over a portion of the exterior surface of the inner tubular portion; and   a plurality of heating elements attached to the outer tubular portion and positioned around the exterior surface of the inner tubular portion, wherein at least a portion of the plurality heating elements are electrically connected in parallel.   
   
   
       16 . The flow-through heater of  claim 15  wherein the cylindrical member comprises a single-component construction, the inner tubular portion and the outer tubular portion being constructed from a single piece of material. 
   
   
       17 . The flow-through heater of  claim 15  wherein the cylindrical member comprises a two-component construction, the outer tubular portion being attached to the inner tubular portion by at least one of a taper fit, an interference fit, a wedge, brazing or a thermal epoxy. 
   
   
       18 . The flow-through heater of  claim 15  wherein the outer tubular portion comprises a plurality of receptacles for receiving the plurality of heating elements. 
   
   
       19 . The flow-through heater of  claim 15  wherein the outer tubular portion comprises a plurality of fins extending in a longitudinal direction and projecting radially outwardly from the longitudinal axis, and wherein the plurality of heating elements are located between adjacent fins. 
   
   
       20 . The flow-through heater of  claim 15  wherein at least some of the plurality of heating elements have a wattage that varies along its length.