This preview shows pages 1–2. Sign up to view the full content.
MEAM 203
FALL 2002
THERMO  MIDTERM II
Closed books.
Answer all three questions.
Write clearly!
Explain all steps.
Answers without
clear explanation will be discounted.
GOOD LUCK
.
(30%)
1.
In a counter flow heat exchanger air is used to heat up water.
Air enters the heat
exchanger at 2 kg/s, 125 kPa, and 1000 K and leaves at 100kPa and 400 K. Water enters at 0.5
kg/s, 200kPa, 20C, and it leaves as liquid vapor mixture at 200kPa.
(15 %)
(A) What is the quality of the exiting steam?
(
5%)
(B) What is the rate of change in the air entropy?
(10%)
(C) What is the total rate of entropy generation?
Assume that the air is an ideal gas with temperatureindependent specific heat Cp=1kJ/kgK and
R=0.287kJ/kgK.
The properties of the water are given below:
Water: T=20C; p=200kPa;
u=84kJ/kg;
h=84kJ/kg;
v=0.001m
3
/kg;
s=0.3kJ/kgK
Saturated water at
p=200kPa;
u
v
=2530kJ/kg;
h
v
=2707kJ/kg;
s
v
=7.13kJ/kgK;
u
l
= 505kJ/kg;
h
l
= 505kJ/kg;
s
l
=1.53kJ/kgK;
(30%)
2.
An adiabatic tank of volume V is initially evacuated. The tank is connected through a
valve to a line that carries an ideal gas at pressure p
L
and temperature T
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 Bau

Click to edit the document details