POWER CYCLES IN 1001 Flashcards
Which of the following thermodynamic cycles is the most efficient?
(A) Brayton
(B) Rankine
(C) Carnot
(D) Combined Brayton-Rankine
(C) Carnot
The ideal reversible Carnot cycle involves several basic processes. What type of processes are they?
(A) all adiabatic
(B) all isentropic
(C) two adiabatic and two isentropic
(D) two isothermal and two isentropic
(D) two isothermal and two isentropic
What is the temperature difference of the cycle if the entropy difference is ΔS and the work done is W?
(A) W - ΔS
(B) W / ΔS
(C) ΔS / W
(D) W(ΔS)
(B) W / ΔS
For a heat engine operating between two temperatures (T2 > T1), what is the maximum efficiency attainable?
(A) 1 - (T2 / T1)
(B) 1 - (T1 / T2)
(C) T1 / T2
(D) 1 - (T1 / T2)ᵏ
(B) 1 - (T1 / T2)
Which of the following is NOT an advantage of a superheated, closed Rankine cycle over an open Rankine cycle?
(A) increased efficiency
(B) increased turbine work output
(C) increased turbine life
(D) increased boiler life
(D) increased boiler life
Which of the following statements regarding Rankine cycles is FALSE?
(A) Use of a condensible vapor in the cycle increases the efficiency of the cycle.
(B) The temperature at which energy is transferred to and from the working liquid are less separated than in a Carnot cycle.
(C) Superheated increases the efficiency of a Rankine cycle.
(D) In a practical terms, the susceptibility of the engine materials to corrosion is not a key limitation on the operating efficiency.
(D) In a practical terms, the susceptibility of the engine materials to corrosion is not a key limitation on the operating efficiency.
Which of the following sets of reversible processes describes an ideal Otto cycle?
I. adiabatic compression, constant volume heat addition, adiabatic expansion, constant volume heat rejection
II. isothermal compression, isobaric heat addition, isothermal expansion, isobaric heat rejection
(A) I only
(B) II only
(C) I and II in succession
(D) II and I in succession
(A) I only
A steam generator produces saturated steam at 700.5 kPa from saturated liquid at 101.35 kPa. If the heat source is a bath at 171°C that provides 1860.8 kJ/kg, which of the following is true?
(A) The device violates the first law of thermodynamics only.
(B) The device violates the second law of thermodynamics only.
(C) The device violates both the first and second laws of thermodynamics.
(D) No thermodynamic laws are violated
(A) The device violates the first law of thermodynamics only.
A device that is meant to extract power from waste process steam starts with steam of 75% quality at 700.5 kPa. The exit conditions of the steam are 70% quality at 101.35 kPa. Which of the following statements are true?
(A) This device violates the first law of thermodynamics
(B) This device violates the second law of thermodynamics
(C) The device generates positive net power.
(D) The device generates no net power.
(C) The device generates positive net power.
An engineer devises a scheme for extracting some power from waste process steam. The engineer claims that the steam enters the device at 700.5 kPa and quality 75%, and the steam exits at 101.35 kPa and 65% quality. Which of the following statements are true?
I. The device produces 316 kJ/kg of work.
II. The device violates the second law of thermodynamics.
III. The device violates the first law of thermodynamics.
I. The device produces 316 kJ/kg of work.
II. The device violates the second law of thermodynamics.
A carnot refrigerator operates between two reservoirs. One reservoir is at a higher temperature, TH, and the other is at a cooler temperature, Tc. What is the coefficient of performance, COP, of the refrigerator?
(A) TH - (TC/TH)
(B) 1 - (TC/TH)
(C) (TH/TC) - TC
(D) TC / (TH - TC)
(D) TC / (TH - TC)
What is the ideal compression ratio of an Otto cycle that uses air as the gas and has an efficiency of 50%?
(A) 4.3:1
(B) 5.0:1
(C) 5.7:1
(D) 6.2:1
(C) 5.7:1
What is the ideal efficiency of an Otto cycle with a compression ratio of 6:1? The gas used is air.
(A) 0.167
(B) 0.191
(C) 0.488
(D) 0.512
(D) 0.512
