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Thermo > Eng Storage 1 > Flashcards

Eng Storage 1 Flashcards

1
Q

Merits of Pumped Hydro ES

A

mature technology, low running cost, reasonable round trip efficiency, good volume and power, can store for long periods, long life

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2
Q

Cons of pumped hydro ES

A

geographic restriction, large land use is needed, low energy density, high capex, evaporation losses, environmental concerns

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3
Q

3 types of hydro turbine based on flow

A

Axial, Radial, Mixed

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4
Q

2 types of hydro turbine based on pressure change

A

Impulse (no change, ex pelton), Reaction (yes change, ex francis and kaplan)

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5
Q

Friction factor is a function of

A

Reynolds # and pipe roughness/diameter

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6
Q

Gas turbine power plants are cheaper or more expensive than vapor power plants

A

cheaper

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7
Q

In air-standard analysis, air behaves…

A

as an ideal gas

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8
Q

In cold air standard analysis, what is assumed constant

A

cp wrt temperature

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9
Q

Isentropic processes are also…

A

adiabatic, but not the other way around

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10
Q

In the brayton cycle, the expansion and compression are treated as

A

adiabatic

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11
Q

In an ideal brayton cycle, the flow through the energy exchangers is _______ and the flow through compressor/turbine is _____

A

isobaric; isentropic

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12
Q

Brayton Cycle is for ___; Rankine Cycle is for ____

A

air(+gas) ; steam

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13
Q

The PV diagram shows _____; the T-s diagram shows _____

A

Work interactions (int:Vdp); Heat interactions (int:Tds)

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14
Q

Increasing the pressure ratio increases the Brayton cycle ____ and ____ and ____

A

efficiency, back work ratio, turbine inlet temperature

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15
Q

The biggest source of irreversibility (entropy production) in a gas turbine cycle is

A

combustion

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16
Q

Name 3 ways of modifying gas cycles

A

regeneration, multi-stage compression, multi-stage expansion

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17
Q

A regenerator increases ____ by preheating ____

A

thermal efficiency, air entering the combustor (using the exhaust heat from the turbine)

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18
Q

For a regenerator, the temperature entering the cold side must be ____ than the temperature entering the hot side (exhaust)

A

less than

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19
Q

SSS’s are … (combined cycle)

A

synchro self shifting (clutch)

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20
Q

Thrust in a jet engine comes from

A

Increase in nozzle exit velocity relative to diffuser inlet velocity

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21
Q

Pr in A-22 is

A

relative pressure

22
Q

Ideal gas model assumes u and h vary solely with

A

temperature

23
Q

dh = cp or cv * dT?

A

cp

24
Q

h =

A

u + pv

25
Q

Cp =

A

R+Cv

26
Q

3 main types of compressed air energy storage

A

Diabatic, advanced adiabatic, isothermal

27
Q

k for air =

A

1.4

28
Q

Isothermal expansion can deliver electrical energy without…

A

natural gas combustion for preheating

29
Q

High efficiency of flywheels is restricted by

A

storage time - only feasible in short periods

30
Q

Flywheels can be useful for supplying high ____ specialty needs

A

instantaneous power

31
Q

For a flywheel, doubling the mass doubles the force, but doubling the speed…

A

quadruples the force

32
Q

Depth of Dischage for a FW is

A

differnce between max KE (operating at highest speed) and minimum KE (operating at lowest speed)

33
Q

Liquid Air Energy Storage is also sometimes called

A

Cryogenic energy storage

34
Q

Nitrogen liquifies at about…

A

-196C

35
Q

For liquid air energy storage, the liquid is stored at ___ pressure

A

low

36
Q

The Linde-Hampson cycle is used to

A

liquify air

37
Q

The gas in a Linde-Hampson cycle is coolest when it leaves…

A

the expansion valve

38
Q

LAES generation scheme without _____ is considered too inefficient to be practical

A

additional energy input (slide 27)

39
Q

R134a is an example of an

A

Organic refrigerant

40
Q

For generation with LAES, __ and ___ cycles are 2 that could be added to boost net work

A

Cryogenic Organic Rankine and Cold Brayton

41
Q

The working fluid in an Organic Rankine cycle has a____

A

low boiling point

42
Q

Some advantages to LAES

A

Low upfront and lifetime costs, long lifetime, can be scales up, uses mature technologies, can be integrated with other industrial processes, not geographically restricted

43
Q

Disadvantages of LAES

A

Low round trip efficiency, safety risks, needs large scale to be efficient and cost effective

44
Q

Electricity, energy transfer, gasoline, etc are examples of

A

Secondary forms of energy

45
Q

Working Fluid for pumped thermal ES is often

A

Air or Argon

46
Q

Desrues and Howe are examples of

A

Cycles for Pumped Thermal energy storage

47
Q

A transcritical rankine cycle uses what as the working fluid

A

CO2

48
Q

In a transcritical power cycle, the working fluid is kept as a ___ during compression and as a ___ or as supercritical during expansion

A

liquid; vapor

49
Q

At the critical point on the phase diagram, the substance..

A

is indistinguishable from a liquid and a gas

50
Q

A saturation state is a state where…

A

a phase change begins or ends

51
Q

Curves bordering the vapor dome on a pvt chart are called

A

saturated vapor lines

52
Q

saturation temperature designates

A

the temp at which a phase change occurs at a specified pressure

Thermo (4 decks)

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