| 摘要 |
An electric immersion heating apparatus for heating highly corrosive liquids includes a flexible cable-type immersion heater having a continuous coiled resistance heating element disposed in axially spaced pitches and being enclosed in a continuous tubular outer jacket formed of a flexible plastic material, such as polytetrafluoroethylene with a PFA side chain, resistant to chemical attach by highly corrosive liquids. The outer jacket is received over the coiled heating element in closely fitting relationship and has a wall thickness sufficiently thin to provide efficient heat transfer from the coiled element to the liquid being heated. Because of its thinness the outer tubular jacket is subject to permeation of damaging corrosive vapors through the jacket to the coiled heating element. During use the heater is immersed in the corrosive liquid except for its ends and a continuous flow of pressurized dry gaseous medium is circulated through the jacket in surrounding relation to the coiled element from one end of the heater to the other for continuously scavenging any corrosive vapors which may have permeated through the outer jacket into the interior of the heater.
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