Insulated pipe heat transfer

gundy · May 12, 2014, 03:46

In simulating heat transfer through a pipe with convection boundary conditions on the inside and out, I used the field function

($$Position(@CoordinateSystem("Laboratory.Cylindri cal"))[0]<0.3)?55:0.04

to define a thermal conductivity of 55 W/m-K when the radius is <0.3 (for the pipe) and 0.04 W/m-K for radius>0.3 (for the insulation). However, I get the error message

"Field function "Variable Conductivity" cannot be evaluated on region Pipe solid"

when assigning this field function to the Thermal Conductivity material property. Any suggestions?

me3840 · May 12, 2014, 20:58

Why do you need a field function for this? Just put a different BC on the inside and outside of the pipe.

gundy · May 12, 2014, 21:33

Thanks for the reply. Perhaps I wasn't clear; I simulated the pipe and insulation as one solid cylinder with a hole in the middle (there are, of course, other ways to do this). For the sake of experimenting with field functions, I intended on using my function to define the conductivity of the outside portion (.3<r<.4) of the pipe as .04 (effectively creating the insulation) and the inside (.2<r<.3) as 55 (the pipe).

I've used field functions before to set initial values for temperature and such, I just can't figure out why it won't work for material properties.

me3840 · May 12, 2014, 22:41

I don't think this is a very good idea. You're leaving material properties down to an interpolation algorithm.

I would recommend you mesh the two solids and interface them instead.

May 12, 2014, 03:46	Insulated pipe heat transfer	#1
gundy New Member Andrew Gunderson Join Date: May 2014 Posts: 2 Rep Power: 0	In simulating heat transfer through a pipe with convection boundary conditions on the inside and out, I used the field function ($$Position(@CoordinateSystem("Laboratory.Cylindri cal"))[0]<0.3)?55:0.04 to define a thermal conductivity of 55 W/m-K when the radius is <0.3 (for the pipe) and 0.04 W/m-K for radius>0.3 (for the insulation). However, I get the error message "Field function "Variable Conductivity" cannot be evaluated on region Pipe solid" when assigning this field function to the Thermal Conductivity material property. Any suggestions?

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May 12, 2014, 20:58		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Why do you need a field function for this? Just put a different BC on the inside and outside of the pipe.

May 12, 2014, 21:33		#3
gundy New Member Andrew Gunderson Join Date: May 2014 Posts: 2 Rep Power: 0	Thanks for the reply. Perhaps I wasn't clear; I simulated the pipe and insulation as one solid cylinder with a hole in the middle (there are, of course, other ways to do this). For the sake of experimenting with field functions, I intended on using my function to define the conductivity of the outside portion (.3<r<.4) of the pipe as .04 (effectively creating the insulation) and the inside (.2<r<.3) as 55 (the pipe). I've used field functions before to set initial values for temperature and such, I just can't figure out why it won't work for material properties.

May 12, 2014, 22:41		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	I don't think this is a very good idea. You're leaving material properties down to an interpolation algorithm. I would recommend you mesh the two solids and interface them instead.