# time varying thermal conductivity for transient thermal analysis

Member Posts: 6

Hello,

Is there a way to define time varying quantities of thermal conductivity for a transient thermal?

I'm trying to solve a transient thermal problem, where in I knew the time variation of conductivities a priori. Basically, i was doing a multiple solve, and a each step i was using the MPDELE, and then try to redefine the material at a given time using MPDATA.

The solver triggered a warning that ' changing the material property during solution is a 'non-standard way'. Is it a correct way to define time varying quantities of a thermal- material property?

May i know if there any other standard way to define it.

Below is the script i tried to come up with

FINISH

/CLEAR,NOSTART

/PREP7

LENGTH=2e-03         ! 2*LENGTH, mm

HEIGHT=LENGTH/100    ! HEIGHT, mm

THICK=HEIGHT

esize=HEIGHT

area=HEIGHT*THICK

kxx_1   = 5.000000000E-03 ! VALUE AT initial time, t=0

cx_1   = 4.039360000E-02  ! VALUE AT initial time, t=0

t1= 358.000         ! inital temperature

mptemp,1,t1

mpdata,KXX,1,1,kxx_1

mpdata,C,1,1,cx_1

R,1,area    ! AREA

k,1,-0.5*LENGTH

k,2, 0.0

k,3, 0.5*LENGTH

l,1,2

l,2,3

lglue,1,2

lesize,all,esize

type,1

real,1

mat,1

lmesh,all

esel,s,type,,1

nsle,r

IC,all,temp,1

allsel,all,all

d,node(-0.5*LENGTH,0,0),temp,0

d,node(0.5*LENGTH,0,0),temp,0

FINISH

/SOLU,

ANTYPE,TRANS

KBC,0

nleng=40

deltime=2

*dim,dxx_1,array,nleng,1

*dim,ccstinter_1,array,nleng,1

*do,tt,1,40

currtime=deltime*tt

curr_temp=(273+85)+2*deltime*(tt)

dxx_1(tt,1)=D0_1*exp((-ED_1)/(R*curr_temp))

ccstinter_1(tt,1)=RH*S0_1*P0_1*exp((ES_1-EVP_1)/(R*curr_temp))

mptemp,1,0

mpdele,kxx,1

mpdata,kxx,1,,dxx_1(tt,1)

mpdele,c,1

mpdata,c,1,,ccstinter_1(tt,1)

allsel,all,all

OUTRES,ALL,ALL

TIME,currtime

NSUBS,1,1,1

solve

*enddo

FINISH

• PunePosts: 191Forum Coordinator