[hello77]

Hello everyone,
I'm trying to simulate the flow around a multi tubes and fins heat exchanger in starting up condition, transient, using Fluent. The input conditions for water and air are given using the UDF shown below.
When the simulation was run, the water and air inlet temperatures did not change according to the UDF. I mean they keep changing using the equations in the first interval (from 0 to 8000 sec) and did not go to the second condition even the running time was greater than 8000 sec. My experience is very limited in programming with C language and I guess there something wrong with the UDF!
I appreciate your help to solve this issue.

UDF:
#include "udf.h"

DEFINE_PROFILE(RAMP_waterIN, thread, position)
{

float t, waterIN;
face_t f;

t = RP_Get_Real("flow-time");
if (0 < t < 8000)
{ waterIN = (-0.00000000007*(t*t*t))+(0.0000005*(t*t))+(0.0052*t )+296.071;
}
else if (8000 <= t <= 10000)
{ waterIN = 333;
}



begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = waterIN;
}
end_f_loop(f, thread)

}

DEFINE_PROFILE(RAMP_airIN, thread, position)
{

float t, airIN;
face_t f;

t = RP_Get_Real("flow-time");
if (0 < t < 8000)
{ airIN = (-0.000000000006*(t*t*t))+(0.00000006*(t*t))+(0.0002 *t)+292.23;
}
else if (8000 <= t <= 10000)
{ airIN = 294.91;
}



begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = airIN;
}
end_f_loop(f, thread)

}

[kamer]

Try to change
if (0 < t < 8000) to if (0<t&&t<8000),
use && as "and" in C language.
other sentences can be treated as the same.

[kamer]

Try to change
if (0 < t < 8000) to if (0<t&&t<8000),
use && as "and" in C language.
other sentences can be treated as the same.

[hello77]

Thank you kamer. its working now.