heat tracing - second post

[picasa]

I posted the following in a different forum. Thought may be I could get better response here!

For a simple finite element model for flow of slurry through a pipe, boundary conditions on the pipe wall need to be decided. The different cases are: 1. Heat traced pipe 2. Steam-jacketted pipe 3. Insulated pipe without any heat input 4. Bare pipe 5. Pipe with color applied to it.

Typically boundary conditions on the pipe wall can be: 1. Constant heat flux 2. Variable heat flux (function of time) 3. Constant temperature 4. Variable temperature (function of time)

Depending on the nature of the different physical cases in the first paragraph, the boundary conditions for the model need to be decided. Any input on how to match the different boundary conditions in paragraph 2 with the different cases in paragraph 1 is appreciated.

 

[BigInch]

Heat trace, constant flux
Jacket, constant flux
Insulation, constant temp (unless exterior ambient temp varies)
Bare pipe, (assumed black) constant or varies with ambient temp and wind or convection (exposure) and often with solar radiation, plus conduction if buried, see below.
Pipe with color, constant or varies daily with radiation and spectrum adsorbing quality of color and exposure, assumed not buried.

Typically, buried pipe w/ or w/o insulation can vary in start-up conditions as dirt in contact with pipe heats up. It may take several months depending on heat capacities and temperatures.