Week 5 Lecture 7 Flashcards

1
Q
A
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2
Q

Rate of entropy change =

A

Rate of entropy transfer + rate of entropy production

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3
Q

At steady state the rate of entropy change is ____

A

0

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4
Q

At steady state, the equation for rate of entropy is:

A

0 = rate of entropy transfer + rate of entropy production

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5
Q

The rate of entropy transfer =

A

Σ(Qk/Tk) + Σmisi - Σmjsj

(Qk/Tk) represents the heat transfer occuring at temperature Tk
i and j refer to the inlet and outlet streams

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6
Q

Rate of entropy production

A

S gen

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7
Q

Rate of entropy transfer + Rate of entropy production equation

A

Σ(Qk/Tk) + Σmisi - Σmjsj + S gen = 0

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8
Q

Entropy is not a ________ quantity

A

conserved

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9
Q

If the process is irreversible, there maybe an ________

A

internal generation

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10
Q

If the process is ________, there maybe an internal generation

A

irreversible

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11
Q

Type of diagram used for Rankine cycle

A

T-S diagram

T is for temperature
S is for entropy

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12
Q

enthalpy-entropy chart

A

h-s diagram

enthalpy-entropy chart

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13
Q

p-h diagram

A

pressure enthalpy diagram

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14
Q

constant entropy

A

isentropic

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15
Q

isentropic conditions are shown by a ____ line on T-S and H-S diagrams

A

straight vertical

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16
Q

example of a reversible heat engine

A

carnot cycle

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17
Q

The two vertical steps on a carnot engine are ____ processes

A

adiabatic

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18
Q

The two horizontal steps on a carnot engine are ____ processes

A

isothermal

19
Q

Carnot engine adiabatic compression equation for work

A

W = nCv(Th-Tc)

20
Q

Carnot engine adiabatic expansion equation for work

A

W = nCv(Tc-Th)

21
Q

Carnot engine isothermal expansion equation for work

A

W = nRT ln(P2/P3)

22
Q

Carnot engine isothermal compression equation for work

A

W = nRT ln(P1/P4)

23
Q

Net work of carnot cycle =

A

net work = W12 + W23 + W34 + W41
as W12 and W34 cancel, net work reduces to
net work = W23 + W41

24
Q

Type of diagram carnot cycle is shown on

A

P-V

25
Q

Result of carnot engine analysis shows that

A
  • No engine can be more efficient than the Carnot engine
  • Net work extracted is the area inside the cycle
26
Q

Thermal or cycle efficiency, for a reversible process =

A

η = 1 - Tc/Th

27
Q

Reason why no engine can be more efficient than Carnot engine

A

irreversibility

28
Q

COP refrigeration

A

COP = Tc/ (Th - Tc)

29
Q

COP heat pump

A

COP = Th/ (Th - Tc)

30
Q

For a reversible heat engine:

A

W = Qh/Th (Th - Tc)
Qh/Th = Qc/Tc

31
Q

Used to produce most forms of electricity

A

Vapour power cycle

32
Q
A
33
Q
A
34
Q

Rankine cycle components order

A

Pump
Boiler
Turbine
Condenser

Please Break The Chair

35
Q

In Rankine cycle, has input of work

A

Pump

36
Q

In Rankine cycle, has output of work

A

turbine

37
Q

Process over the pump in rankine cycle

A

reversible adiabatic compression (isentropic)

38
Q

Process over the turbine in rankine cycle

A

reversible adiabatic expansion (isentropic)

39
Q

Rankine cycle heat input/output

A

Heat input > condenser heat output

40
Q

Rankine cycle power input/output

A

Steam turbine power output&raquo_space; pump power input

41
Q

Type of diagram Rankine cycle usually depicted on

A

T-S diagram

42
Q

High moisture content in the turbine leads to

A

Poor efficiency

43
Q

Step in Rankine cycle where Qh is added to the system

A

boiler

44
Q

Step in Rankine cycle where Qc exits the system

A

condenser