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Thermo > Definitions and E Balance > Flashcards

Definitions and E Balance Flashcards

1
Q

A ____ system has no mass exchange

A

Closed

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2
Q

A open system that has mass exchanged is studied by looking at a…

A

Control Volume

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3
Q

Are boundaries fixed?

A

No, they may move or change shape/size over time

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4
Q

A ___ system has no mass exchange and no ____

A

Isolated, energy

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5
Q

A process is a transformation from one state…

A

to another state

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6
Q

A property is a __________ of a system that desciribes its ____

A

macroscopic characteristic, condition

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7
Q

An intensive property is

A

size INDEPENDENT

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8
Q

an Extensive property is

A

size DEPENDENT

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9
Q

_____ is a condition of a system at a given time described by it’s properties

A

STATE

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10
Q

A State is called “fixed” if….

A

a minimum number of properties known to describe it completely

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11
Q

Energy is a ____ property

A

extensive

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12
Q

Some examples of intensive properties

A

Temperature, Pressure, density, molar mass

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13
Q

True or false: there may be infinitely many process paths between any 2 given states

A

TRUE

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14
Q

at ___ state, the system condition does not change with time

A

steady

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15
Q

_____ is the lowest energy state possible, where the system usually is at ____

A

DEAD STATE, equilibrium with its surroundings

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16
Q

An equilibrium is ….

A

the balance of an influence (ex mechanical, chemical, phase)

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17
Q

Thermodynamic Equilibrium means….

A

all influences on a system are in balance at the same time

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18
Q

Quasi-equilibrium state means…

A

system is very close to equilibrium, it’s a very slow process, completed in a piece wise equilibrium

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19
Q

____ is energy in transit

A

Work

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20
Q

Equation for work (mechanical)

A

W = integral{Ft * ds}

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21
Q

2nd law

A

entropy naturally increases; restoring order requires effort

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22
Q

Work is = 0 if there is no ____ in the direction of the force applied at the boundary

A

displacement

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23
Q

Power = F_vector *…

A

(dot product) w/ velocity vector

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24
Q

Work is _____ energy transit

A

path dependent

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25
Q

Change in stored system energy is ____

A

path independent

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26
Q

Equation for Work done by a gas through volume expansion under pressure

A

W = integral{p * dv}

27
Q

Equation for Work (electric)

A

Integral { V(t)I(t)dt}

28
Q

Work_dot (electric) = Power =

A

I*V

29
Q

0th law

A

When two objects at different temperatures, energy flows from warmer to colder in the form of heat until they reach thermal equilibrium (same temperature)

30
Q

Work is ____ valuable form of energy transfer than heat

A

More

31
Q

These 2 types of heat interaction rely on physical contact

A

convection and conduction

32
Q

____ is the dominant mode of heat transfer in solids

A

conduction

33
Q

Internal energy is tied to the ____ of a system

A

temperature

34
Q

for an incompressible substance, c_p =

A

c_v = c

35
Q

delta U of an ideal gas =

A

mc_vdeltaT

36
Q

The 1st law states

A

energy is conserved

37
Q

A reversible process is ______ concept

A

an ideal

38
Q

Irreversibilities may be ____ and/or ____

A

internal; external

39
Q

A thermal reservoir is….

A

a body at constant temp while its energy changes; ideal object

40
Q

A polytropic process is described by

A

p*V^n = constant

41
Q

A quasi-static process is…

A

a process that happens infinitely slowly

42
Q

A quasi equilibrium process is…

A

a quasi-static process in which the system is always in equilibrium (ie. slow expansion or compression)

43
Q

For expansion and contraction of gases, Work =

A

area under PV curve

44
Q

change in total E for a cycle =

A

0

45
Q

For a cycle, average rate of E_in =

A

average rate of E_out

46
Q

Delta (any property) = 0 for

A

a cycle

47
Q

A power cycle…

A

converts heat to work

48
Q

Examples of irreversibilities

A

electrical resistance; friction; mixing of liquids or vapors, plastic deformation

49
Q

Efficiency of a power cycle =

A

W_net out/Q_heat in from warm reservoir

50
Q

COP_Refrig =

A

QL/W_net in

51
Q

COP_heat

A

QH/W_net in

52
Q

Is the reverse of the Kelvin Plank statement true?

A

Yes

53
Q

Can carnot efficiencies be applied to individual processes?

A

No, only cycles

54
Q

If the SCI = 0 then system is

A

internally reversible

55
Q

An impossible system has an SCI …

A

< 0

56
Q

SCI gives a measure of …

A

irreversibilities and relative inefficiencies

57
Q

Units of entropy

A

kJ / K

58
Q

Entropy production is a measurement of…

A

the irreversibilties in a given process

59
Q

Can sigma_p < 0 ?

A

NO

60
Q

If there is heat flow out of your system, system entropy should

A

decrease

61
Q

Can SCI be applied to individual processes?

A

NO

62
Q

Is entropy conserved?

A

NO

63
Q

Can entropy balance be applied to processes?

A

YES

Thermo (4 decks)

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