@Rob Thanks for responding .if you do not mind can you explain it with more clarity
Here i have attached the governing equations
Are you denoting the fourth equation??
( )T3+( )T4 =0.5Qdel x+k(dT/dx)
( )T3+( )T4 =0.5Qdel x-(-k(dT/dx))
( )T3+( )T4 =0.5Qdel x- q(heat flux)
and i don't understand "dx increses(to the right )" can you explain it also please??

for more details: here i have attached ansys file
please help me to find it Rob .