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CHEE 203 > EXAM 2 > Flashcards

EXAM 2 Flashcards

1
Q

What does compressible mean?

A

fluid can change shape/size as we change P/T

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2
Q

Are gases compressible/incompressible?

A

compressible

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3
Q

Mach number equation

A

u/c where c is speed of sound in fluid

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4
Q

What mathematically is true for incompressible flow?

A

(rho1/rho2) < 2 AND (Ma < 0.3)

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5
Q

What energy balance do you follow for incompressible flow? What fluids does this describe?

A

Chapter 2 … all liquids and slow moving gases

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6
Q

What two things could prove the show is compressible?

A

pressure ratio large or flow very fast

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7
Q

When compressible flow, what are the dominant terms of mechanical energy balance?

A

kinetic energy and compressible effects (large change in density)

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8
Q

What kind of flow is air through AC duct?

A

incompressible

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9
Q

What find of flow is flow from a high pressure tank through a short tube?

A

compressible

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10
Q

What does Mach number indicate?

A

importance of compressibility and velocity

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11
Q

What variable represents mass velocity?

A

G

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12
Q

Eqn of mass velocity?

A

G = (velocity)*(density)

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13
Q

What are the units of mass velocity?

A

kg/(m^2*s)

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14
Q

What does k represent?

A

ratio of heat capacity (Cp/Cv)

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15
Q

What is the k value for monoatomic processes?

A

1.67

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16
Q

What is the k value of diatomic processes?

A

1.40

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17
Q

What is the k value of triatomic processes?

A

1.32

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18
Q

What does it mean when a system is adiabatic?

A

There is no mass/heat transfer between system and environment

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19
Q

What kind of system is an isolated system?

A

adiabatic

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20
Q

What happens to velocity as a fluid moves down an adiabatic system?

A

it increases

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21
Q

What happens to density as a fluid moves down an adiabatic system?

A

it decreases because pressure decreases

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22
Q

What happens to pressure as a fluid moves down an adiabatic system?

A

it decreases

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23
Q

What happens to temperature as a fluid moves down an adiabatic system?

A

unknown without knowing about flow… if the frictional loss is greater than the impact of velocity change, temperature will increase

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24
Q

What happens to Ma as a fluid moves down an adiabatic system?

A

it increases

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25
Q

What happens to mass velocity as a fluid moves down an adiabatic system?

A

it stays the same

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26
Q

What is the relationship between the pressure at the outlet of an adiabatic system and the pressure of the surroundings?

A

they are equivalent

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27
Q

What is choked flow?

A

Largest possible flow rate in pipe with friction (sonic velocity at outlet)

28
Q

If the pressure of the surroundings of an adiabatic system at choked flow continues to decrease, what happens to velocity and flow rate?

A

Velocity remains sonic because gas leaving system cannot go any faster, and flow rate remains unchanged

29
Q

What are the outlet temperature, pressure, and density dependent on in an adiabatic system with friction?

A

Mach number only

30
Q

What is the difference between equations of adiabatic and isothermal systems?

A

adiabatic system eqns contain Y terms

31
Q

What does the mechanical energy balance relate for an adiabatic system?

A

Ma and frictional loss in length of pipe

32
Q

In an isothermal system, as the pressure of the surroundings decreases, what happens to the flow rate?

A

it increases until reaching choked flow

33
Q

What is the limiting exit for isothermal?

A

Ma = 1/sqrt(k)

34
Q

What is the limiting exit for adiabatic?

A

Ma = 1

35
Q

What happens to the temperature of the system as fluid moves down an isothermal system?

A

It stays the same

36
Q

What happens to the velocity of the system as fluid moves down an isothermal system?

A

it increases

37
Q

What happens to the mass velocity of the system as fluid moves down an isothermal system?

A

it stays the same

38
Q

What happens to the pressure of the system as fluid moves down an isothermal system?

A

it decreases

39
Q

What happens to the Mach number of the system as fluid moves down an isothermal system?

A

it increases

40
Q

What is the relationship between the T at choking conditions and at inlet for an isothermal system?

A

they are equivalent

41
Q

What is the relationship between the P at choking conditions and at inlet for an isothermal system?

A

Pch = P1Ma1(sqrt(k))

42
Q

What is the relationship between the density at choking conditions and at inlet for an isothermal system?

A

rho(ch) = rho(1)Ma1(sqrt(k))

43
Q

What is the relationship between the velocity at choking conditions and at inlet for an isothermal system?

A

u(ch) = (u(1)/(Ma1*sqrt(k)))

44
Q

What are the units of dynamic viscosity?

A

kg/(ms) or Pas

45
Q

What is an example of Bingham Plastic?

A

toothpaste, peanut butter, butter

46
Q

What is an example of a dilatant?

A

quick sand

47
Q

What kind of shear is dilatant?

A

thickening (n>1)

48
Q

What kind of shear is pseudoplastic?

A

thinning (n<1)

49
Q

Describe graph of pseudoplastic

A

starts at origin and eventually curves downward

50
Q

Describe graph of dilatant

A

starts at origin and eventually curves upward

51
Q

Describe graph of Bingham Plastics

A

is linear and has y-intercept > 0

52
Q

Describe graph of general plastics

A

has y-intercept > 0 and eventually curves downward

53
Q

What type of non-newtonians do we deal with?

A

time independent

54
Q

What variable does the velocity eqn of a Bingham plastic contain that the other NN fluids do not?

A

m

55
Q

What variable does the velocity eqn of a power law fluid contain that the other NN fluids do not?

A

K

56
Q

What variables are in the velocity eqn of a power law fluid that differentiates it from the others?

A

K and m

57
Q

What has characteristics of both Bingham Plastics and Power law fluids?

A

General Plastics

58
Q

What kind of NNs are power law fluid?

A

pseudoplastics and dilatants

59
Q

What does the n in the total stress eqn represent?

A

plastic viscosity

60
Q

What NN has a plug like core?

A

Bingham Plastics

61
Q

When m≥1 for Bingham plastics, what is true of velocity?

A

it is 0

62
Q

When is flow of a Bingham plastic frozen?

A

when Tau(w)«Tau(not)

63
Q

What does Tau(w) represent?

A

Wall stress (Josh thinks)

64
Q

What is nearly always negligible for a Bingham Plastic mechanical energy balance?

A

velocity term

65
Q

For what type of NN do we use Re(gen)?

A

Power law fluids

CHEE 203 (3 decks)

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