I wrote some expressions for Nu and htc and when I drew contours I got negative values for them. Here are my expressions
Myhtc=Wall Heat Flux/(T-780[K])
Nu=Myhtc*0.06[m]/0.31[W m^-1 K^-1]
But as it can be seen in the pic. I got negative values for Nu. Is there any problem related to the expressions?
Thanks in advance