CHE/CEEN/MEEN 2300
Online Engineering Thermodynamics
Instructor: Dr. Holly Moore
Test 2 – 100 pts
Show your work. Partial credit will be awarded, but only if you have shown your
work. Answers without supporting calculations will be counted wrong!!
You may use a 3"x5" index card with notes, a periodic table and a calculator. You may
also need the Properties Table booklet, either your own or you may borrow one for the
duration of the test.
1. 15 pts. Complete this table for refrigerant R-134a.
T 0F
15
10
110
P, psia
h, Btu/lbm
80
78
x
0.6
70
180
129.46
1.0
Show your work for any answers that are not just table lookups.
Phase
description
2. 10 pts. A piston cylinder device contains 0.85 kg of refrigerant R-134a at -100C.
The piston is free to move and has a mass of 12 kg and a diameter of 25 cm. The
local atmospheric pressure is 88 kPa. Now heat is transferred to the refrigerant
until the temperature is 150C. Determine
a. The final pressure
b. the change in the volume of the cylinder
c. the change in the enthalpy (h) of the refrigerant
To solve this problem, first draw and label a picture of your system. Then fill in the table
with the process conditions at state one and state two. Continue to fill in the process
conditions as you calculate them or look them up in the Property Tables.
State 1
Draw your picture here
State 2
3. 12 pts. Determine the specific volume of refrigerant R-134a vapor at 0.9 MPa and
700C based on
a. the ideal gas law
b. the generalized compressibility chart
c. data from tables
4. 10 pts. Assume you have an insulated tank containing 1.5 lbm of Helium at 80
degrees F, and at a pressure of 50 psia. The tank is stirred by a paddle wheel that uses
0.02 hp for 30 minutes. The work that enters the tank from the paddle wheel is thus
25.45 BTU.
Find the final temperature and the final pressure in the tank. Before you solve the
problem answer these questions.
a. Is Helium an ideal gas at these conditions?
b. Does Helium have constant heat capacity values?
5. 10 pts. Assume you have an insulated tank containing 1.5 lbm of Nitrogen at 80
degrees F, and at a pressure of 50 psia. The tank is stirred by a paddle wheel that uses
0.02 hp for 30 minutes. The work that enters the tank from the paddle wheel is thus
25.45 BTU.
Find the final temperature and the final pressure in the tank. Before you solve the
problem answer these questions.
a. Is Nitrogen an ideal gas at these conditions?
b. Does Nitrogen have constant heat capacity values?
6. 10 pts. Assume you have an insulated tank containing 1.5 lbm of R134a at 80 degrees
F, and at a pressure of 50 psia. The tank is stirred by a paddle wheel that uses 0.02 hp for
30 minutes. The work that enters the tank from the paddle wheel is thus 25.45 BTU.
Find the final temperature and the final pressure in the tank. Before you solve the
problem answer these questions.
a. Is R-134a an ideal gas at these conditions?
b. Does R-134a have constant heat capacity values?
7. Assume that you have a well insulated rigid tank divided into two equal sections. One
section is filled with water at 25 degrees C and 100 kPa. The other side is
evacuated. Now the partition is removed. Find the final temperature and the pressure.
To solve this problem, first draw and label a picture of your system. Then fill in the table
with the process conditions at state one and state two. Continue to fill in the process
conditions as you calculate them or look them up in the Property Tables.
State 1
Draw your picture here
State 2
8. Assume you have a piston cylinder device filled with steam at 1.6 MPa, with a freely
moving frictionless piston (keeping the pressure constant). An electric heater is used to
heat the gas from 300 C to 500 C. If the mass of the steam in the piston cylinder device
is 1 kg, find the amount of work that must be supplied to the electric heater. Notice that
there are two work terms in this problem - the electric work and the boundary work
resulting from the volume change as the piston moves.
To solve this problem, first draw and label a picture of your system. Then fill in the
table with the process conditions at state one and state two. Continue to fill in the process
conditions as you calculate them or look them up in the Property Tables.
State 1
Draw your picture here
State 2