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A problem about transient thermoelectric cooler analyse in ANSYS
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fain84@gmail.com
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Joined: 11 May 2006
Posts: 1

PostPosted: Thu May 11, 2006 1:35 pm    Post subject: A problem about transient thermoelectric cooler analyse in ANSYS Reply with quote

Does someone here konw about thermoelectric analysis with ANSYS, I've
got some question to ask.

I am quite intrested in thermoelectric cooler and want to simulate it
with ANSYS. But I got a problem.

I read the ANSYS 9.0 documentation and found an example of
thermoelectric cooler. I modified it in the foolowing step.

1. In the original model, the temperature of the two junctions are
fixed. In order to simulate some 'real' conditions, I applied
convection loads on the junctions. On the cold junction, the film
coeffiency is normal and on the other one, the film coefficency is
quite large.
2. The original example applied a static analysis. But in some
conditions, transient analysis is requied. So I applied a new transient
analysis.

After the simulation, I got a curve of temperature of the cold junction
according to time. But the problem came out.

First I set the analyse time to 20 and the final cold junction
temperature is about 24 deg.C. The second time, I set the time to 50,
the temperature is the same! In my opinion, the first curve should be
part of the second one. But now, the second one seemes to be the first
curve, stretched 2.5 times according time.

It' quite werid. I look up the ANSYS 9.0 documentation and found that
the thermoelectric analyse was a new function of that version of the
software. I searched the library, but coludn't get any help.

Hope someone could answer me this question.

Post my batch code in the following:
!==================================================================
FILNAME, THERMOELECTRIC COOLER
/TITLE, THERMOELECTRIC COOLER
/VUP,1,Z ! specifies the global cartesian coordinate system
reference orientation.
/VIEW,1,1,1,1 ! view point
/TRIAD,OFF !
/NUMBER,0 ! show colors and numbers
/UNITS,SI ! standard international units
!/NOPR

/PREP7
L=1E-2 ! element height
W=1E-2 ! element width and length
HS=2E-3 ! strap height

TOFFST,273 ! temperature offset, deg.C

! N-type material
MP,RSVX,1,1E-5 ! electrical resistivity, ohm*m
MP,KXX,1,1.8 ! thermal conductivity, watt/(m*k)
MP,SBKX,1,-170E-6 ! seebeck coefficient, volt/k
MP,DENS,1,3E3 ! density, kg/(m^3)
MP,C,1, 0.8e3 ! specific heat, Joule/(kg*deg.C)

! P-type material
MP,RSVX,2,0.769E-5 ! electrical resistivity, ohm*m
MP,KXX,2,1.4 ! thermal conductivity, watt/(m*k)
MP,SBKX,2,180E-6 ! seebeck coefficient,volt/k
MP,DENS,2,3e3 ! density, kg/(m^3)
MP,C,2, 0.8e3 ! specific heat, Joule/(kg*deg.C)

! connecting straps (copper)
MP,RSVX,3,1.7E-8 ! resistivity, ohm*m
MP,KXX,3,400 ! thermal conductivity, watt/(m*k)
MP,DENS,3,8.9e3 ! density, kg/(m^3)
MP,C,3,0.39E3 ! specific heat, Joule/(kg*deg.C)

! FE model
ET,1,226,110 ! 20-NODE THERMO-ELECTRIC BRICK
ET,2,227,110 ! 10-NODE THERMO-ELECTRIC TET

! modeling
BLOCK,W/2,3*W/2,,W,,L
BLOCK,-3*W/2,-W/2,,W,,L
BLOCK,-3*W/2,3*W/2,,W,L,L+HS
BLOCK,-1.7*W,-W/2,,W,-HS,0
BLOCK,W/2,1.7*W,,W,-HS,0
VGLUE,ALL

ESIZE,W/5 ! element size
TYPE,1 ! element type 1
MAT,1 ! material type 1
VMESH,1 ! mesh volume 1
MAT,2 ! material type 2
VMESH,2 ! mesh volume 2
TYPE,2 ! element type 2
MAT,3 ! material type 3
LESIZE,61,HS/3
LESIZE,69,HS/3
LESIZE,30,W/8
LESIZE,51,W/8
LESIZE,29,W/8
LESIZE,50,W/8
VMESH,6,8 ! mesh connecting straps
EPLOT

! boundary conditions and loads
NSEL,S,LOC,Z,L+HS ! select cold junction
CP,1,TEMP,ALL ! couple temp dofs
NC=NDNEXT(0) ! get master node number

NSEL,S,LOC,X,-1.7*W ! first electric terminal
D,ALL,VOLT,0 ! ground

NSEL,S,LOC,X,1.7*W ! second electric terminal
CP,2,VOLT,ALL ! couple volt dofs
NI=NDNEXT(0) ! get master node
NSEL,ALL

FINI

/SOLU ! solve begin
ANTYPE,4 ! transient solve

TIME,50 ! total solve time
DELTIM,5,2,10 ! specify step
OUTRES,ALL,1 ! wirte every step to file

TUNIF,27 ! initial temperature distribution

NSEL,S,LOC,Z,L+HS ! convection on all nodes on the cold junction
SF,ALL,CONV,0.014,27
NSEL,S,LOC,Z,-HS ! convection on all nodes on the hot junction
SF,ALL,CONV,500,27

I=28.7 ! input current
F,NI,AMPS,I ! apply current i, amps to the master node

ALLSEL
SOLVE

/POST26
NSOL,4,NODE(0,W/2,-HS),TEMP,,T_H
NSOL,3,NODE(0,W/2,L+HS),TEMP,,T_C
PLVAR,3,4
FINISH
!=================================================================
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