[JuBong]

Hi everyone,

To give the temperature because it can not give heat flux conditions to the inlet.

I want to change the heat flux condition to the temperature equation.

For example, When T2 is the temperature of the side cell in the flow direction, try to give T1 = T2 - dx / k * q ''.

for example,
In a square module with one cell of 0.001 m2, if the temperature T1 at the inlet is a function of T2 (the temperature of the next cell in the direction of flow), how to use UDF code to express T1 (y) = T2 (y) + 100 ?


example

#include "udf.h"
DEFINE_PROFILE(temperature, thread, position)
{
real x[ND_ND];
real y;
face_t f;
C_T(c,t);

begin_f_loop(f, thread)
{
F_CENTROID(x,f,thread);
y = x[1];
F_PROFILE(f, thread, position) = C_T(c,t) + 100;
}
end_f_loop(f, thread)
}


Could you give me some advice on how to change the code?
Or is there another way of giving heat?

[pakk]

Before you do this, make sure that you really need this.
Are you maybe confusing conductive heat transfer with convective heat transfer? What you want (a temperature gradient at the inlet) is physically possible, but normally points towards a wrong choice of boundary conditions, or a domain that is too small.

And if you are sure that this is what you need, just ask the question once, not four times. Posting it four times will not increase the number of people answering your question, and it makes it more difficult for you because now you have to look at four places if you received an answer...

[JuBong]

Hello, pakk.

Thank you very much for your reply.
Sorry. This forum is the first time I did not know how to delete posts and posted four.
Solar energy enters with the heat flux and I want to put the heat flux into the entrance boundary condition. Can you tell me how?
Thank you.

JuBong.

[pakk]

What else comes in at your inlet? Gas? Liquid?

[JuBong]

Gas come in at inlet pakk.

[pakk]

And besides the gas, sunlight comes through the inlet?

If this is really your set-up, you should think again what you want to simulate. It makes no sense. Probably you are confused about convective vs conductive, but if you are not you should choose a bigger domain.

[JuBong]

Thanks very much pakk.

I listened to you and tried to think more.
The solar heat reflected from the solar absorber was shot into the inlet of the honeycomb shaped channel.
So the passing air gets heat by the convection and the hot gas comes out at the exit.

Originally, there are several small channels overlapping and measuring the heat flux at the inlet of each channel. Think of these channels as prous media and try to count them as fluent. So the process of calculating the heat flux, rather than the wall, was created.

I tried to apply C_T (c, t) to the boundary condition of the inlet by bringing the temperature of the center of the cell at inlet.
However, the fluent will shut down.

Is the use of C_T (c, t) to get the temperature of the cells wrong?

How can I get the temperature of the center of the cell?

This is my code.
------------------------------------------------------------------

#include "udf.h"

DEFINE_PROFILE(temperature, thread, position)
{
real x[ND_ND];
real y;
face_t f;
Thread *t;
cell_t c;
real temp;

begin_f_loop(f, thread)
{
F_CENTROID(x,f,thread);
y = x[1];
temp = C_T(f,t);
F_PROFILE(f, thread, position) = temp + 30;
}
end_f_loop(f, thread)
}

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