AMME2200 Thermofluids
Quiz 3 - Thermodynamics
12 November 2021
Allowed writing time: 45 minutes
Instructions:
1. Solutions can be written on tablets/computers or on sheets of paper. You will need probably one
page per question.
2. Write your FULL NAME and SID on the very top of every page.
3. Number the pages sequentially at the bottom of each page.
4. Solutions: Solutions should be neatly written. Please make sure that you write the question number
at the start followed by the solution. Show your workings clearly and underline your answers.
5. Upload instructions to Canvas: Export your solution as a pdf or, if writing on paper, scan it by using
an App (eg. OneDrive, CamScanner) which combines multiple photos into a single pdf file.
6. Upload instructions to Canvas: ONLY one single pdf file can be uploaded on Canvas. Multiple
files and other formats will NOT be accepted.
7. You should stop writing after 45 minutes. You are then given an additional 15 minutes to upload
your answers on Canvas. Note that Canvas will not accept late submissions so it is important to use
the additional time only to prepare and upload your answers.
8. If you have technical difficulties uploading your files, please email the course coordinator.
Useful, quick reference data:
1atm = 101.3kPa
Acceleration due to gravity, g = 9.81m/s2
Tables and psychrometric chart are provided in the last page.
Attempt all questions
Notes:
1. REPLACE “Y” ADJACENT TO NUMBERS WITH THE LAST DIGIT OF YOUR SID:
(Example: if your SID ends in 5, then in Question 1, 1.Y kg/s = 1.5 kg/s
In Question 3: 3Y kg/s = 35 kg/s).
Question 1
A steady stream of carbon dioxide enters an adiabatic compressor at 100 kPa and 300K at a rate of 1.Y kg/s
and exits at 600 kPa and 450K. Neglecting the kinetic energy changes and assume constant specific heats
at room temperature, determine:
a) The temperature at the exit of the compressor assuming isentropic conditions (K).
b) The actual power input to the compressor (kW).
c) The isentropic efficiency of the compressor.
Question 2
A simple Brayton cycle using air as the working fluid has a pressure ratio of 10. The minimum and
maximum temperatures in the cycle are 295K and 1240K. Assume an isentropic efficiency of 83% for the
compressor and 87% for the turbine.
a) Show the cycle on a T-s diagram and label all processes.
Use constant specific heats at room temperature to determine:
b) The air temperature at the turbine exit (K).
c) The net specific work output (kJ/kg)
d) The thermal efficiency.
Question 3
A steam power plant operates on a simple ideal Rankine cycle between the pressure limits of 3MPa and 50
kPa. The temperature of the steam at the turbine inlet is 300 oC and the mass flowrate of steam through the
cycle is 3Y kg/s.
a) Show the cycle on a T-s diagram with respect to saturation lines.
b) Determine the power input into the pump (kW).
c) Determine the net power output of the power plant (MW)
General Data
mRTTR
M
m
PV u == Ru = 8.314 kJ/kmol-K
Room Temperature: Cp (kJ/kg-K) Cv (kJ/kg-K) k = Cp/Cv M (kg/kmol) R (kJ/kg-K)
Air 1.0 0.718 1.4 28.97 0.287
Carbon Dioxide 0.846 0.657 1.289 44.01 0.1889
Water: ? = 1000kg/m3 C = 4.18kJ/kgK
Incompressible steady flow
For ideal gas, isentropic (n=k), or polytropic (1 < n < k) process: