Hi, friends. I’m new at this forum and I would like you to help me to try to solve the following:

I’ve been looking forward tutorials or information about how to simulate the heat transfer through a composite wall for calculating the heat loss but I haven’t found anything. So I’m going to explain what I did during the attempts to simulate this and maybe someone could tell me what’s wrong:

1- I drew the wall in 3D as you could see below:

The wall is composed by: 1/2 foot of brick, 36 cm of reinforced concrete and 2 cm of mortar.

2 - I meshed the wall and all were right.

3 - Then, I choosed a ‘heat transfer - advanced’ analysis whose properties I choosed were ‘Steady-state’ and ‘Non-linear analysis’.

4 - I started defining the materials with its respective thermal conductivity, density and specific heat. I assigned the materials that compose the wall to the volumes but here I found the first trouble: I don’t know how to define the Ris (Internal thermal surface resistance [m^2K/W]) and Res (External thermal surface resistance [m^2K/W]) so I omit that and just defined the volume of the room with the properties of air at 25 ºC.

5 - After the material assignment, I defined the boundary conditions but just the temperature because my goal is that SimScale could ‘tell’ me (calculate) the heat loss with an internal temperature of 25 ºC (293,15 K) and a outdoor one of 0 ºC (273,15 K) for what I defined the internal surface as the room’s surface in contact with the wall, and the external surface as the 1/2 foot of brick’s surface.

6 - Finally, I created a new run and after some minutes the result is:

‘The solution matrix is not factorable. This might be caused by an unconstrained rigid body motion or by overconstrained degrees of freedom due to multiple linear relations at at least one node.’

I hope someone could help me because that’s important for my air-conditioning project and I would be really grateful and happy to learn this.

Thank you in advance to this great community.