Learning Forum

[anasnurf]

Hello, I'm trying to simulate a thermoelectric generator consists of 127 pair semi-conductors. I find a tutorial online and try to replicate the boundary conditions. I have three boundary condition which are temperature (hot and cold wall) and voltage with 0 value at the cross-sectional of copper connected to a p-leg wall.

[Bill Bulat]

Maybe I'm missing something, but one thing I don't see is some modeled representation of a second electric terminal. It might be necessary to connect some kind of electrical load (e.g., a resistor) across the terminals of the model, so that current resulting from the thermoelectrically-induced voltage can flow, or to at least designate a second open terminal using nodal coupling (couple the VOLT DOF).
By the way, representation of a lumped electrical load such as a resistor requires a command object to define a CIRCU124 element (this is not natively exposed in the Mechanical GUI). The MAPDL Help includes documentation on this element type. I haven't looked at the attached examples for quite some time but from the name of the directory I saved them in, it appears I may have added a CIRCU124 resistor in one or both of them. Perhaps they will help you modify your model so that it converges. It appears they were saved at V19.1, so if you are using a newer version you should be able to restore the attached archives.
Another thing that I find is that for many problems the current convergence criterion is needlessly tight. It can be loosened in Details of Analysis Settings, often without compromising the accuracy of the calculated results.
I hope this helps you.
Kind regards Bill

[FLaasch]

Hello Bill,

is your command snippet for adding a CIRCU124 still available somewhere? (First time using this forum, so I'm not sure if I'm just missing the download button.)

Thank you,

BR,
Felix

[FLaasch]

 

 

So in case anybody is looking for this: this is how it worked for me. (Not the cleanest code, for example propably not all of the allsels are needed.) Postprocessing by the way was the most complex for me to get right as a first time user of apdl snippets. In my case I needed to add multiple resistors, each between a surface I defined beforehand as a named selection or component (not sure how it’s called in english) and a defined voltage. The snippet takes the named selection, couples all nodes together, adds another node somewhere else, inserts a circu124 between them and adds the voltage on the new node.

First snippet (added below the “steady-state thermal-electric conduction” branch of the tree)

!   Commands inserted into this file will be executed just prior to the ANSYS SOLVE command.

!   These commands may supersede command settings set by Workbench.

 

!   Active UNIT system in Workbench when this object was created:  Metric (mm, kg, N, s, V, A)

!   NOTE:  Any data that requires units (such as mass) is assumed to be in the consistent solver unit system.

!                See Solving Units in the help system for more information.

 

 

/Prep7

 

u1=0 ! Input voltage in Volt

r1= 1e-3  ! Resistor, Ohm, in this example 1 mOhm

 

cmsel,s,NS_Plus_2,node ! select all nodes of the named component NS_Plus_2

CP,NEXT,VOLT,ALL ! Nodal coupling to connect them all

*GET,NCMaster2,NODE,,NUM,MIN, , , , ! get the master node of the modal coupling

N,1000002,1,1,2,0,0,0 ! Insert another node somewhere

cmsel,s,NS_Plus_3,node ! repeat for each resistor

CP,NEXT,VOLT,ALL ! Nodal coupling

*GET,NCMaster3,NODE,,NUM,MIN, , , , !

N,1000003,1,1,3,0,0,0 ! 

[…]

 

et,100,circu124,0 ! define element type

r,100,r1 !definiert real constant 100 for the resistors value

type,100 ! activate element type

real,100 ! activate real constant

 

EN,2000002,1000002,NCMaster2 ! add element

EN,2000003,1000003,NCMaster3 ! repeat for every resistor

[…]

 

ALLSEL

d,1000002,volt,u1 ! bring the voltage to the other side of the resistor

ALLSEL ! maybe not needed

d,1000003,volt,u1 ! repeat for every resistor

[…]

 

! *GET,my_units,ACTIVE,,UNITS 

! Warning, Workbench units must be set to Volt and Ampere to be able to work in Ohm here.

 

ALLSEL

/SOLU

 

Second snippet for postprocessing (added under the “solution” branch of the tree)

 

set, last

allsel ! propably not needed…

 

*Get,my_NodalCurrent2,NODE,1000002,RF,AMPS ! use the default output search prefix function _my to get this into the results area under details of the snippet.

*Get,my_NodalCurrent3,NODE,1000003,RF,AMPS ! repeat for every resistor base node

[…]

 

allsel ! propably not needed…