Objective
 

By surroundings of the room, I suppose you mean the flow and thermal field within the room. In literal sense, surroundings of the room mean everything outside the room and not inside.

This is scenario 1 and my recommendation would be to follow the approach outlined for this scenario in my previous post.

vinerm,
i Want to ask in outlet conditions what i have to enter the backflow temperature?
and second Ambient temperature is enough or heat flux should be given also at the walls of empty room?

Boundary Condition
 

At outlet you can specify 300. This number matters only if there is any flow reversal. Otherwise, this is not important. On the walls, you can use surrounding temperature or convection condition with surrounding temperature and 5-10 as convection coefficient, assuming outside the room there is no strong wind flow.

Thank you Vinerm.
How can i change the material of wall from aluminum to Solid bricks. It does not have any option available for that.

Wall Material
 

That material is not important until and unless you provide some thickness for the wall. If you want to model the wall thickness, then you have to create a material under Materials > Solid or modify the properties of Aluminum to those of brick and mortar.

Do i have too provide any material to AC WALLS? because it is also treating as aluminium?

Wall Material
 

Materials for the walls are not relevant until and unless some thickness is provided. You can neglect these.