viscous dissipation modelling

mahjoob

Hi I try to modelling viscous dissipation in channel, i do it in dimentionless ,for example tetta=(T-Tw)/(Te-Tw), X=x/Dh , in viscous dissipation modellind occore Brikman Number(Br) that it is possitive in cooling and negative in heating. I have the problems:

1- How can i defined the Brikman Number(Br) in fluent?

2- how can i defined the negative Brikman Number?

3- in heating the inlet dimentionless temprature equal to one ,and the wall dimentionless temprature equal to zero,now in heating should the temprature of wall should higher than inlet temprature and brikman number is negative,it is contradiction

Please if any can ,hellp me to modeling the heating in dimentionless with viscous dissipation,thanks for your hellp.