Thermal problem !

Dear All !

I had one non-understood problem when i made thermal excerise as below : Analysis in ANSYS

"One closed box with bonded-contact parts which was placed in 50 C ambient temperature. I made boundary as Convection with simplied case film coeffient and 50 C ambient temperature. Then i analyzed with two cases of Box material.

First, Box material is Composite with 50(W/m.k) Isotropic Thermal Conduction. Second, Box material is Cast Iron with 0.48(W/m.k) Isotropic Thermal Conduction.

And, the result: Composite Box had maximum of outter surface temperature is 41.

Cast Iron Box had maximum of outter surface temperature is 32  ".

I dont understand why composite have smaller Isotropic Thermal Conductin but bigger outter surface temperature !!!!!!

If somebody know that problem, pls help me for guiding !

thank, brg