Watt density on electric bundle heaters

[XL83NL]

Dear all, were appyling an electric heater used for evaporating propylene in a pressure vessel. If the heat input from the heater bundle is too high, concern is that decomposition of the prop. will initiate. Im looking for both reference data (i.e. literature references) and values on the maximum allowable watt density for evaporating propylene, which can be used as an input variable for design of the electric heating bundle.

 

[moltenmetal]

[Why would you want to place the electric heater inside of the pressure vessel ?

This makes heater maintenance and eventual replacement difficult and dangerous, IMHO/quote]

Flanged electric immersion heaters are used for heating and vapourizing flammables all the time. There's nothing inherently more hazardous about using or maintaining them than any other type except perhaps a FIRED heater, which of course is far more hazardous- but those are used for flammables to, on a gigantic scale.

If your choice is between building a new heating utility (steam, hot oil, Dowtherm vapour etc.) for one or two users or using electric directly, and the duty is modest so the energy consumption isn't a huge cost issue, the selection is a fairly easy one.

You can put the heating element on the outside of the heater shell if you only need a tiny amount of surface area and you don't care about surface metal temperatures. With a propylene vapourizer, that's not likely to be the case.

If you're really worried about heater surface temperatures, and your energy source is ultimately electricity, then you need an intermediate fluid- something like hot oil or Dowtherm vapour.