Hi @Kazi,

Your explanation of the problem must be a little more detailed for a good answer to be produced. But it seems you want to initiate temperatures in the room and let the heat dissipate to the outer ambient.

For setting a different initial condition before starting the simulation, you can use the "Patch" option in the "Initialization" section in Fluent. This is assuming you have defined discrete regions for the room and ambient, in which case you can select your desired zone in the dialog that pops up and associate the regions with the temperatures you want.

Cheers.

Dear Mohammad

Thank you for your reply.

I want to find out the volumetric flow rate and the air distribution pattern of a room and the temperature of the room to find out the ventilation rate.

I used transient state and the patch option to specify zone temperature and turned on the gravity option.

So my quarries are:

How and where should put the wind direction in fluent?

Do I need to take any other measure for using zero thickness walls while measuring the temperature?

go to plots and select temperature curve

Dear Kazi,

Consider using a density based solver after consulting the software documentation, as it has a number of parameters you should take into account before choosing your solver.

Your problem is a 3D, transient mixed convection problem and you have a pretty small area where the 25 degree temperature fluid resides. So you should also be careful what the size of your mesh is. Maybe consider refining your mesh where you have the most changes.

About your first question, the direction of the wind should be put into the inlet condition when specifying the boundary condition for your inlet boundary. The default option is "Normal to boundary" but you can change that to "Components" or "Magnitude, direction". I myself find the "Components" option easier to use.

And about your second inquiry, I'm not entirely sure what you mean, but seeing that you have windows (contact with the ambient flow directly), I think the whole domain should be one whole zone, with a patched temperature region in the middle (the small room). Not sure what the condition on the walls should be, but if you have no heat moving through the walls a zero heat flux BC sounds right.

Kazi Shafrin Shahid

How the temperature of the room is maintained at 25 degrees? there should be a heat source obviously.

Looking at your problem and boundary conditions, they do not seem to be logical. Eventually, without a heat source, the temperature of your room gonna reach your inlet temperature (28 degrees) and you will not have any temperature gradient.

Even a transient simulation will take only a few seconds unit the temperature gradient ends up reaching zero and you will get the same 28 degrees of temperature in your entire domain.

Dear Farhad Afsharpanah

Thank you so much for your valuable observation.

Sorry for not being able to make you understand the whole thing. The outdoor air temperature is typically 28 degrees in the summer time and the indoor temperature is 2-3 degrees lower than the outside temperature (because of the materials used in the floor and the walls). And the situation gets reversed in the winter time.

So, I don't want to keep 25 degrees of indoor temperature or say constant. All I really want is what the temperature will be after combining the outside air with the indoor air.

Am I missing something??

Thanks and Happy New year

Kazi Shafrin Shahid

Look, without a heat sink or source, insulation can only delay reaching to a uniform temperature in your problem, it does not prevent it.

Imagine laying down under a blanket, the blanket itself does not make you warm, it reduces the thermal loss from your body. The body is creating the heat, not the blanket. Without the body heat, the temperature under and on the blanket should be technically the same.

Now in your case, you have insulated the room expecting a different temperature inside, but you don't get a different temperature because there is not a heat sink or source inside the room.

Try adding a heat flux or a specific temperature boundary, for example, for the bottom surface of the room, then you will get a different result.

Even in real cases there is something, a gas heater, a radiator, or an air conditioning system. The insulation can only reduce the thermal loss or the amount of required energy for maintaining the temperature difference. For heating the place or making it cold there should be something.

Thanks Farhad Afsharpanah . I am trying.