Question

Constant pressure lines in the superheated region of the Mollier diagram will have

• A. A positive slope
• B. A negative slope
• C. Zero slope
• D. Both positive and negative slope

Answer 1

The correct option is A A positive slope


$\text{As we know,}$
$TdS=dh-vdp$

$TdS=dh$

($dp=0,$ constant pressure lines)

$\frac{dh}{dS}=T$

$\because$ $T>0$

$\frac{dh}{dS}>0$

$\text{Mollier diagram slope}>0$

$\text{Points To Remember:}$
In superheated regions, constant pressure lines diverge, because with increasing temperature, the slope increases.