[emmkell]

Hi

I need to change the heat transfer coefficient on a wall with changing temperature on the wall. I have written a simple UDF to change the heat transfer coefficient, which is interpreting into Fluent with no problems, but when I run a monitor on the wall for Total surface heat transfer coefficient it is giving me strange answers with negative values. I know that very low values of ln() will give a negative answer but anything over ln(0.4) in this equation will give a postivie answer. At a temperature of 297, this equation should give a h value of 3.06, but instead it keeps returning a value of 0.0002.

Is my UDF too basic? or is the problem with my monitor?

#include "udf.h"

DEFINE_PROFILE(HTC, thread, index)
{
face_t f;
real Temp = 293.15;
F_PROFILE(f, thread, index) = 1.2854*log(Temp - 293) + 1.2822;
}

Or should i be using the return HTC function as is used in DEFINE_PROPERTY which change with temperature also?