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Entropy: Heat Engines

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Wize University Physics Textbook (Master) > Thermodynamics

Heat Engines

3 Activities

Wize University Physics Textbook (Master) > Thermodynamics

TS-Diagrams

2 Activities

Wize University Physics Textbook (Master) > Thermodynamics

Entropy

2 Activities

A cylinder contains a diatomic gas at a pressure of 3 atm and a temperature of 250K. Its initial volume is 4.0 liters. The gas is next carried through the following processes:
a. It is expanded isobarically to a temperature of 375K.
b. It is cooled down to 250K in an isochoric process.
c. It is compressed at constant temperature until its volume is 4.0 liters,
returning it to its initial state.
a) Show this cycle in a TS Curve.
b) What is the efficiency of this heat engine?
c) What is the change of entropy for each process?
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Question A
More Heat Engines Questions:
A Carnot engine has an efficiency of 33.0% It operates between constant reservoirs differing in temperature by 95oC.
What are the temperatures of the two reservoirs?
Entropy: Heat Engines
A cylinder contains Nitrogen gas (𝐢v = 20.8Jmol.K\frac{J}{mol.K} , 𝛾 = 1.4) at a pressure of 3 atm and a temperature of 250K. Its initial volume is 2.0 liters. The Nitrogen gas is next carried through the following processes:
a. It is heated in an isochoric process to a temperature of 375K
b. It is expanded at a constant temperature to a volume of 3.0 liters
Heat Engines: Otto Cycle
Otto Cycle is made of two isochoric processes at 𝑉0 and π‘Ÿπ‘‰0 for π‘Ÿ > 1 and two adiabatic processes which compress and extend the gas between these two volumes.
Plot PV curve of this cycle and find its efficiency in terms of only compression ratio, π‘Ÿ and 𝛾.
In a Stirling heat engine, a monatomic ideal gas at initial volume V1 and temperature T1, takes in heat at a constant volume until its temperature is T2, and then expands isothermally until its volume is V2. It gives out heat at a constant volume until its temperature is again T1 and then returns to its initial state by isothermal contraction. Calculate the efficiency and compare with a Carnot engine operating between the same two temperatures.
Thermodynamics: Heat Engines
A diatomic gas undergoes some thermodynamical processes according to the following plot. Imagine the process from a to b could be changed in order to get different efficiency for the following cycle under the condition that the temperature of the gas cannot exceed the temperature at point a during the entire cycle. What is the work done by the gas from a to b in a process which makes the efficiency of the heat engine equal to the half of the efficiency of a Carnot engine which works in the same range of temperatures? (Assume we have 2 moles of the gas)
PV Curve: Heat Engines
In a Diesel cycle Vo volume of gas is expanded in an isobaric process to
𝛼𝑉o and then is expanded more to π‘Ÿπ‘‰o in an adiabatic process. The gas in then cooled down via an isochoric process and then is compressed back to its initial volume. Draw PV curve of this cycle and find the efficiency of this cycle only in terms of 𝛼, π‘Ÿ ,and 𝛾.
Which one of the following statements best describes the operation of a heat engine?
For heat engine cycle is
clockwise
while for heat pump cycle is
counterclockwise
An engine is found to have an efficiency of 0.40. If it does 200 J of work per cycle, what are the corresponding quantities of heat absorbed and rejected?
More TS-Diagrams Questions:
A system of a cylinder and a piston has the shape of the diagram below when the temperature of the gas inside the cylinder is 300℃ and its pressure is 200πΎπ‘ƒπ‘Ž. The piston has a mass of 50 π‘˜π‘” and its radius is . 06 π‘š and pushes against a set of stops at initial condition so that the height of the cylinder is 80 π‘π‘š. The temperature outside the cylinder is 30℃ and the pressure is 1 π‘Žπ‘‘π‘š. The cylinder cools down by exchanging heat with the environment.
a. Draw a free body diagram of the piston.
b. At what temperature and pressure does the piston start to move
PV and TS Diagrams
A system of a cylinder and a piston has the shape of the diagram below when the temperature of the gas inside the cylinder is 300℃ and its pressure is 200πΎπ‘ƒπ‘Ž. The piston has a mass of 50 π‘˜π‘” and its radius is . 06 π‘š and pushes against a set of stops at initial condition so that the height of the cylinder is 80 π‘π‘š. The temperature outside the cylinder is 30℃ and the pressure is 1 π‘Žπ‘‘π‘š. The cylinder cools down by exchanging heat with the environment.
a. Draw a free body diagram of the piston.
b. At what temperature and pressure does the piston start to move down?
More Entropy Questions:
Entropy: Heat Engines
A cylinder contains Nitrogen gas (𝐢v = 20.8Jmol.K\frac{J}{mol.K} , 𝛾 = 1.4) at a pressure of 3 atm and a temperature of 250K. Its initial volume is 2.0 liters. The Nitrogen gas is next carried through the following processes:
a. It is heated in an isochoric process to a temperature of 375K
b. It is expanded at a constant temperature to a volume of 3.0 liters
Thermodynamics: Entropy
If 3.0 kg of water at 100.0℃ is mixed with 1.0kg of ice at βˆ’10.0℃ . Find the
final temperature and the total change in entropy of the system.
(Cw=4190 Jkgβ‹…K, Ci=2100 Jkgβ‹…K, Lf=334Γ—103 JKg)\left(C_w=4190\ \frac{J}{kg\cdot K},\ C_i=2100\ \frac{J}{kg\cdot K},\ L_f=334\times10^3\ \frac{J}{Kg}\right)
How does entropy differ from energy?
Predict the sign of the Ξ”H, Ξ”S,(+ or -) and identify when the following reactions are spontaneous at low temperature, high temperature, or all temperatures (low, high, all). Use commas to write your answers ie. +,+,low
For freezing of a popsicle: Ξ”H is ___________, Ξ”S is ___________. Reaction is spontaneous at ____________________ temperatures
For evaporation of liquid water: Ξ”H is ___________, Ξ”S is ___________. Reaction is spontaneous at ____________________ temperatures
Arrange the following compounds in order of increasing entropy, assuming 1 mol of each compound:
Ar(g)Fe(s)CH3CH2CH3(g)HOCH2CH2CH2OH(l)Ar(g) \hspace{15pt}Fe(s)\hspace{15pt} CH_3CH_2CH_{3(g)} \hspace{15pt} HOCH_2CH_2CH_2OH_{(l)}
Ar(g)Ar(g)