heat transfer with constant wall temperature

Marco

hi! i am modeling a gap in 2d, or you can say two parallel plates which are infinite wide. so in 2d i got two rectangles and in between i got a flow of liquid which should cool down. now i am asked to model some kind of rod inbetween the two plates which should cool down the fluid some more. because of the infinite width of my plates the rod also is infinite wide and has got no contact to the surrounding, its completely surrounded by liquid. so in reality the rod would heat up to the liquids temperature and wouldnt lead off some more heat because it has no contact to any other part. i am supposed to define a constant temperature for the rod,which is cooler than the liquid so it can absorb the heat. i tried to set the walls of the rod under boundary conditions from "coupled" to "temperature" and define the temperature, then the rod had the temperature, but it did not lead away some heat of the liquid. can someone tell me how to set the boundary conditions etc so that heat is led off? thank you in advance

Marco