Department of Chemical Engineering
Chemical Engineering Thermodynamics
Tutorial 1
Basic Concepts and the First Law of
Thermodynamics
Due Date: Thursday, 27th February 2025 @ 9h30
Question 1
Answer the following questions:
a) In what forms can energy cross the boundaries of a closed system?
b) When is the energy crossing the boundaries of a closed system heat and when is
it work?
c) A gas in a piston–cylinder device is compressed, and as a result its temperature
rises. Is this a heat or work interaction?
d) A room is heated by an iron that is left plugged in. Is this a heat or work interaction?
Take the entire room, including the iron, as the system.
e) An insulated room is heated by burning candles. Is this a heat or work interaction?
Take the entire room, including the candles, as the system.
f) What are point and path functions? Give at least 2 examples of each.
Question 2
An ideal gas is undergoing a series of three operations: The gas is heated at constant
volume from 300 K and 100 kPa to a pressure of 200 kPa. It is expanded in a reversible
adiabatic process to a pressure of 100 kPa. It is cooled at constant pressure of 100 kPa
to 300 K. Determine the heat and work effects for each step. Assume Cp = 29.3 kJ/kmol.K.
Question 3
Air passes through a gas turbine system at a rate of 4.5 kg/s. It leaves the turbine system
with a velocity of 90 m/s and a specific volume of 0.85 m3/kg. It leaves the turbine system
with a specific volume of 1.45 m3/kg. The exit area of the turbine system is 0.038 m 2. In
its passage through the turbine system, the specific enthalpy of air is reduced by 200
kJ/kg and there is a heat transfer loss of 40 kJ/kg. Determine:
(a) The inlet area of the turbine in m2.
(b) The exit velocity of air in m/s.
(c) The power developed by the turbine system in kW.
Question 4
A fluid flows at the rate of 4kg/s. It enters the system at a pressure of 600kPa, a velocity
of 220m/s, internal energy of 2200kJ/kg and a specific volume of 0.42m 3/kg. It leaves the
system at a pressure of 150kPa, a velocity of 145m/s, internal energy of 1650kJ/kg and
specific volume of 1.5m3/kg. During its passage through the system, the fluid has a loss
Tut 1: 20th February 2025
of heat transfer of 40kJ/kg to the surroundings. Determine the power of the system, stating
whether it is from or to the system. Neglect any change in potential energy.
Question 5
A quantity of gas has a volume of 0.15m 3 at a temperature of 1200C and a pressure of
1.2MPa. The air is expanded to a pressure of 200kPa according to the law PV 1.32 = C.
Determine
(a) the work transfer
(b) the change of internal energy
(c) the heat transfer
Take Cp = 1.006kJ/kg.K, Cv = 0.717kJ/kg.K
ALL QUESTIONS ARE COMPULSORY
ONLY SELECTED QUESTIONS WILL BE MARKED
A FULL MEMORANDUM WILL BE POSTED TO BLACKBOARD
Tut 1: 20th February 2025