Section 1
Exercises: Things Engineers- Thinks about
Of mass, energy, and entropy, which are conserved?
Both entropy and enthalpy are introduced in this text without accompanying physical pictures. Can you think of other such properties?
How might you explain the entropy production concept in terms a child would understand?
Referring to Fig. 2.3, if systems A and B operate adiabatically, does the entropy of each increase, decrease, or remain the same?
If a closed system would undergo an internally reversible process and an irreversible process between the same end states, how would the changes in entropy for the two processes compare? How would the amounts of entropy produced compare?
Is is possible for the entropy of both a closed system and its surroundings to decrease during a process?
Describe a process of a closed system for which the entropy of both the system and its surroundings increase.
How can entropy be transferred into, or out of, a closed system? A control volume?
What happens to the entropy produced in a one-inlet, one-exit control volume at steady state?
The two power cycles shown to the same scale in the figure are composed of internally reversible processes. Compare the net work developed by these cycles. Which cycle has the greater thermal efficiency?
Sketch $T-s$ and $p-v$ diagrams of a gas executing a power cycle consisting of four internally reversible processes in series: constant specific volume, constant pressure, isentropic, isothermal.
Sketch the $T-s$ diagram for the Carnot vapor cycle of Fig. 5.12.
All states of an adiabatic and internally reversible process of a closed system have the same entropy, but is a process between two states having same entropy necessarily adiabatic and internally reversible?
Discuss the operation of a turbine in the limit as isentropic efficiency approaches $100 \%$; in the limit as isentropic efficiency approaches $0 \%$.
What can be deduced from energy and entropy balances about a system undergoing a thermodynamic cycle while receiving energy by heat transfer at temperature $T_{\mathrm{C}}$ and discharging energy by heat transfer at a higher temperature $T_{\mathrm{H}}$, if these are the only energy transfers the system experiences?
Reducing irreversibilities within a system can improve its thermodynamic performance, but steps taken in this direction are usually constrained by other considerations. What are some of these?