Answer to Question #115784 in Mechanical Engineering for Smith

Question

During the constant pressure reversible non-flow process with air, the temperature increases from 400 0F to 1600 0F. Show process on the p-V and T-s coordinates and find the heat transfer in BTU/lbm.

Answer 1

$T_1 = 400^o F$

$T_2 = 1600^o F$

The key point for solving this problem is : the heat transfer for a non-flow reversible constant pressure process equals to the change in enthalpy of the system. Therefore,

$q = c_p(T_2-T_1)$

regardless of the temperature, cp could be found by

$c_p=R.k/k-1$

$R= 0.06856 BTU/lb ^oF$ The value for k also assumed to be 1.4.

Thus, $c_p = 0.2399= 0.24$

$=> Q=0.24(1600-400)= 288 BTU/lb$