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Thermodynamics > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

Sign convention is that Qin and Wout are

A

positive

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2
Q

Brouwers Rules:

Rule 6

A

Ethics

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3
Q

Fundamental cannons of engineering ethics

A
  1. hold paramount the safety, health, and welfare of the public
  2. build their reputation on the merit of their services, shall not compete unfairly with others
  3. be faithful agents or trustees, avoid conflicts of interest
  4. objective and truthful
  5. consider environmental impacts
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4
Q

Closed system

A

No transfer of mass

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5
Q

Open system

A

region of space through which mass flows

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6
Q

Change in energy of closed system

A

ΔE=ΔU+ΔKE+ΔPE

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7
Q

W>0 means work is done ____ the system

A

by

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8
Q

Q>0 means heat transfer ___ the system

A

to

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9
Q

Rankine Cycle Model

A
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10
Q

Rankine Cycle

Turbine Work Equation

A
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11
Q

Rankine Cycle

Condenser Heat Transfer Eq

A
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12
Q

Rankine Cycle

Pump Work Eq

A
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13
Q

Rankine Cycle

Boiler Heat Transfer Eq

A
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14
Q

Rankine Cycle

Thermal Efficiency

A
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15
Q

Rankine Cycle

Back Work Ratio

A
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16
Q

Rankine Cycle Processes

1-2

2-3

3-4

4-1

A
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17
Q

Rankine Cycle Ideal

TS Diagram

A
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18
Q

Rankine cycle

Increasing Boiler pressure (increases or decreases) thermal efficiency?

What is the TS diagram?

A

Increase

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19
Q

Rankine Cycle

Decreasing compressor pressure (increases or decreases) thermal efficiency?

What is the TS diagram?

A

Increases

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20
Q

Rankine cycle

Isentropic efficiency turbine

A
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21
Q

Rankine Cycle

Isentropic Pump Efiiciency

A
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22
Q

Rankine Cycle

Most significant source of irreversibility

A

combustion

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23
Q

Rankine Cycle

What is superheat?

A

Adding heat to vapor before entering the turbine so that the vapor is supereated

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24
Q

Rankine Cycle

The superheater in the cycle is a ___ and the combination of the boiler and superheater is called a ______.

A

heat exchanger

steam generator

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25
Q

Rankine Cycle

Using a superheater ____ the thermal efficiency. It also ____ the quality at the turbine exit.

A

increases

increases

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26
Q

Rankine Cycle

With reheat, a power plant can take advantage of ____ efficiency that results from ____ boiler pressure and avoid ____ quality steam at the turbine exit.

A

increased

higher

low

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27
Q

Rankine Cycle

Advancements in materials have allowed for power plants to operate with steam generator pressures exceeding the critical pressure of water. These plants are called _____ vapor power plants.

A

Supercritical.

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28
Q

Rankine Cycle

Ideal reheat diagram

A
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29
Q

Rankine Cycle

Ideal Reheat TS Diagram

A
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30
Q

Rankine Cycle

Supercritical TS Diagram

A
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31
Q

Rankine Cycle

During regeneration, the average temperature of heat addition is ____, thereby tending to ____ the thermal efficiency.

A

increased

increase

32
Q

Rankine Cycle

An open feedwater heater is

A

a type of direct contact heat exchanger in which streams at different temperatures mix to foorm a stream at an intermediate temperature

33
Q

Rankine Cycle

A source of irrevirsibility with open feedwater heaters is in ____.

A

mixing

34
Q

Rankine Cycle

With open feedwater heaters, the amount of energy to vaporize or superheat steam is ____, resulting in ____ thermal efficiency.

A

reduced

increased

35
Q

Rankine Cycle

Closed feedwater heaters are shell-and-tube type recuperators in which the feedwater temperature _______ as the extracted steam condenses on the outside of the tubes carrying the feedwater.

A

increases

36
Q

Rankine Cycle

Open feedwater heater diagram

A
37
Q

Rankine Cycle

Open feedwater heater TS diagram

A
38
Q

Rankine Cycle

Closed Feedwater heater diagram

A
39
Q

Rankine Cycle

Closed feedwater heater TS diagram

A
40
Q

Rankine Cycle

Cogeneration systems are

A

integrated systems that simultaneously yield two valuable products- electricity and steam- from a single fuel input.

41
Q

Rankine Cycle

Regenerative vapor power cycle w open feedwater heater

Equations for turbine, pump, steam generator, and condenser

A
42
Q

Rankine Cycle

y for open feedwater heater

A
43
Q

Rankine Cycle

y for closed feedwater heater

A
44
Q

Deaeration is

A

a process of purifying the working fluid in a multiple-feedwater-heater system to prevent corrosion ( heater operating at P> Patm so that oxygen and other dissolved gasses can be vented)

45
Q

________ is used as the working fluid in the vast majority of vapor power systems

A

demineralized water

46
Q

Organic Rankine Cycles employ _____ as working fluids due to their relatively low boiling points, allowing for low-temp power production

A

organic substances like hydrocarbons, refrigerants, ammonia, and silicon oiol

47
Q

Gas Power Systems

Compression Ratio is defined as

A

the volume of the dead center divided by the volume at the top dead center

48
Q

Gas Power Systems

Two principle types of reciprocating internal combustion engines are

A

Spark-ignition engine

compression-ignition engine

49
Q

in a spark ignition engine, a mixture of ____ and ____ is ignited by a _____.

A

fuel

air

spark plug

50
Q

In a compression ignitioin engine, ____ is compressed to a high enough temperature and pressure that _____ occurs spontaneously when fuel is injected

A

air

combustion

51
Q

In engines, the mean effective pressure is

A

the theoretical constant pressure that, when acted on by a piston during the power stroke, would produce the same net work as actually developed in one cycle

52
Q

mep=

A

(net work for one cycle) / (displacement volume)

53
Q

Which energy variables should be used for first law analysis of the “open” (control volume, CV) and “closed” (control mass) thermodynamic cycles?

A

Enthalpy (H) for open systems and internal energy (U) for closed systems

54
Q

Which of the following statements is not true?

A

Entropy of a working fluid undergoing a process within a system can only increase.

55
Q

The figure below shows p-v diagram for Carnot cycle. Which one of the following processes are incorrectly matched with what is happening during the process?

Process 3-4: Adiabatic Expansion

None of the above

Process 4-1: Isothermal Compression

Process 1-2: Adiabatic Compression

Process 2-3: Isothermal Expansion

A

None of the above

56
Q

Which one of the following options correctly represents the Rankine cycle’s thermal efficiency?

W_net/Q_in

1-(T_cold/T_hot)

1-(Q_out/Q_in)

(h1’-h4)/(h2’-h3)

A

W_net/Q_in

or

1-(Q_out/Q_in)

57
Q

Which one of the following is true about Otto and Diesel Cycles?

Assuming the same compression ratio, Otto cycle is more efficient.

Otto cycle is practically more efficient than Diesel cycle

The working fluid of both cycles is a mixture of air and fuel that when analyzing cycles, thermal properties of the mixture have to be accounted for.

Diesel cycle is more efficient because heat addition occurs at constant pressure instead of at constant volume.

A

Assuming the same compression ratio, Otto cycle is more efficient.

58
Q

Select all that are true about Air standard assumptions.

The working fluid is air and behaves as an ideal gas.

The exhaust process is replaced by the heat rejection process.

All the process are internally reversible.

“Cold air standard assumptions” is just an another name for Air standard assumptions.

When analyzing the combustion process, the air standard assumptions cannot be applied because they do not account for any fuel-mixing effect.

A

The working fluid is air and behaves as an ideal gas.

The exhaust process is replaced by the heat rejection process.

All the process are internally reversible.

59
Q

Otto Cycle

TS Diagram

A
60
Q

Diesel Cycle

TS Diagram

A
61
Q

Dual Cycle

TS Diagram

A
62
Q

Otto Cycle

Process

A
63
Q

Brayton cycle

Ideal Shematic

A
64
Q

Brayton cycle

TS Diagram ideal

A
65
Q

Brayton Cycle

Reheat TS Diagram

A
66
Q

Brayton Cycle

Combined Schematic

A
67
Q

Brayton Cycle

Regeneration TS Diagram

A
68
Q

Brayton Cycle

Reheat and intercooling Schematic

A
69
Q

Brayton Cycle

Reheat and intercooling TS Diagram

A
70
Q

Brayton Cycle

Regeneration Schematic

A
71
Q

Brayton Cycle

Reheat Schematic

A
72
Q

Ericsson TS Diagram

A
73
Q

Stirling TS Diagram

A
74
Q

Jet Engine Schematic

A
75
Q

Jet Engine TS Diagram

A

Thermodynamics (2 decks)

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