CHAPTER 7 Flashcards
(40 cards)
Which of the following processes does not typically occur during a topping cycle?
Condensation of steam at low pressure
A thermodynamic process where the pressure of the system remains constant.
Isobaric
It is used to get mechanical work from a high energy fluid such as a gas or steam.
Turbine
In a topping cycle, electricity is generated first, and the waste heat created throughout the process
is used for heating. This is the most prevalent type of cogeneration.
Both statements are true
Works by using heat transfer to convert a gas or vapor into a liquid, effectively releasing heat in
the process.
Condenser
What is the efficiency of a topping cycle?
60% to 80%
Which of the following statements is true about the bottoming cycle?
The waste heat of the process is recovered via heat exchanger.
Adiabatic processes typically occur very quickly. Some processes are adiabatic.
Only the fisrt statement is true
Cogeneration is commonly known as ____________?
Combined Heat and Power
How much heat source does a bottoming cycle system require?
260C
What does efficiency primarily measure in thermodynamic systems?
Useful output relative to input
In a power plant, what does overall efficiency account for that simple thermal efficiency does not?
Auxiliary component losses and total system losses
According to Çengel et al. (2015), energy conversion efficiency (η) is defined as:
Useful energy output divided by total energy input
What property enables us to determine the useful work potential of a given energy amount at a
specified state?
Exergy
Gibbs Free Energy is particularly useful for systems at constant:
pressure and temperature
What does a negative change in Helmholtz Free Energy (A<0) indicate about a process at
constant volume and temperature?
Spontaneous process
What key difference separates exergy from free energy like Gibbs Free Energy?
Exergy explicitly accounts for environmental reference states
In exergy analysis for power generation, what is primarily identified in each component like
turbines and pumps?
Irreversibilities and energy quality losses
The Carnot efficiency formula for an ideal heat engine operating between two reservoirs is:
η = 1 - TL/TH
What performance term is used instead of “efficiency” for refrigerators and heat pumps?
Coefficient of Performance (COP)
Which of the following best describes the First Law of Thermodynamics?
Energy cannot be created or destroyed, it can only be transformed from one form to
another.
According to the Kelvin-Planck statement, which of the following is true?
It is impossible for any device to receive heat from a single reservoir and produce a net amount of work.
Which of the following best describes the Second Law of Thermodynamics?
The Second Law sets limits on the efficiency of energy conversion systems and asserts that energy has both quality and quantity.
Which of the following statements about entropy is true?
Entropy is a measure of the disorder or randomness of a system, with higher entropy indicating less useful energy for doing work.
