Question

A frictionless piston–cylinder device contains 5 kg of nitrogen at 100 kPa and 250 K. Nitrogen is now compressed slowly according to the relation PV1.4 = constant until it reaches a final temperature of 450 K. Calculate the work input during this process

Answer 1

Answer:

The work input during this process is -742 kJ

Explanation:

Given;

Initial temperature of nitrogen T₁ = 250 K

final temperature of nitrogen T₂ = 450 K

mass of nitrogen, m = 5 kg

$PV^{1.4} = constant$

The work input during the process is calculated as;

$W = \frac{m*R(T_2-T_1)}{1-n}$

where;

R is gas constant = 0.2968 kJ/kgK

substitute given values in above equation.

$W = \frac{m*R(T_2-T_1)}{1-n} = \frac{5*0.2968(450-250)}{1-1.4} = -742 \ kJ$

Therefore, the work input during this process is -742 kJ