Question

2lb/min of a certain gas whose R=767ft-lb/lb-R undergoes a steady flow isentropic process from 50 psia, 90ft/lb and 300ft/s until the pressure and velocity are doubled, and the volume is reduced by one third of its inital value. Determine a)H b)U c) Work

Answer 1

Velocity is directly proportional to the Temperature of a system.

This means that when the velocity is doubled, the Absolute Temperature is doubled

P₁/P₂ = 1/2

V₂/V₁ = 1/3

P₁/P₂ = (V₂/V₁)^γ

1/2 = (1/3)^γ

γ = 0.631

$W = \dfrac{1}{γ -1}(p_1V_1 - p_2V_2)$

$W = \dfrac{1}{0.631- 1} (150V_2 - 50V_2)$

$W = -2.71(100V_2) = -271V_2$

$∆U = -W = 271V_2$