Coming from an Electronic Engineering background I am currently a bit lost with a problem involving heat transfer. Essentially, I would like to know whether it is possible to roughly predict the final temperature of a sealed housing containing a heat source, which exchanges temperature with its surroundings. Refer to the following illustration where $T_1$, $T_2$ and $T_\mathrm{amb}$ denote respectively the temperature of the heat source, housing, and ambient/room.
Note: The housing is completely sealed and $T_\mathrm{amb}$ is controlled.
Without the sealed housing, I was able to roughly calculate the temperature using the thermal impedance of the heat source. However, with the addition of the housing, I cannot foresee how $T_2$ is going to suffer with the rather limited convective cooling. Any ideas about how it can be solved?