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Mec132 > Thermofluids > Flashcards

Thermofluids Flashcards

1
Q

What is the second law of thermodynamics?

A

The total entropy of an isolated system can only increase with time. “You never get out what you put in”

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2
Q

What is the first law of thermodynamics?

A

/\U=Q-W

Where U is the internal energy, Q is the heat supplied to the system and W is the work done BY the system

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3
Q

What type of process does a throttle valve represent?

A

An ISENTHALPIC one.

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4
Q

Define isentropic.

A

No change in entropy. This is ideal.

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5
Q

Define viscosity.

A

Viscosity is a quantity expressing the magnitude of internal friction in a fluid, as measured by the force per unit area resisting uniform flow

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6
Q

What is the specific volume of a substance?

A

It is the ratio of a substances volume to it’s mass. Measured in m^3/kg

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7
Q

What is absolute pressure?

A

Absolute pressure is a comparison between your measured pressure and a vacuum.

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8
Q

What is gauge pressure?

A

Gauge pressure is a comparison between your pressure and a reference pressure (such as that of the atmosphere).

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9
Q

Name 3 properties of an ideal gas

A
  • Particles are treated as point-masses
  • Particles collide elastically with the walls of the container
  • Particles may pass through each other. They contain no attractive potential energy
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10
Q

What is the purpose of a U-tub manometer?

A

To measure the difference between two unknown pressures.

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11
Q

What is Bernoulli’s Equation?

A

P + pgh + (pC*C)/2 = constant(k)

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12
Q

When does cavitation occur?

A

When the pressure of the fluid is below the saturated-vapour pressure, cavitation (vapour bubbles) occurs.

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13
Q

What is the critical Reynolds number?

A

2000

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14
Q

What is incompressible flow?

A

When the density of a fluid remains constant as it goes through fluid flow.

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15
Q

Define inviscid flow.

A

A flow where viscous effects do not significantly influence the flow and are this neglected.

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16
Q

What is a Newtonian fluid?

A

A fluid with a constant viscosity.

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17
Q

What does HCP mean? What is the stacking sequence?

A

Hexagonal closed packed.

Stacking sequence is ABABABAB

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18
Q

What is atomic packing fraction?

A

APF=((Number of particles)*(Particle Volume))/(Unit Cell Volume)

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19
Q

How many atoms in a bcc and fcc cubic?

A

fcc cubic = 4 atoms per unit cell

bcc cubic = 2 atoms per unit cell

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20
Q

What is ionic bonding?

A

Electrostatic attraction arising from an exchange of electrons to form +ve and -ve species

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21
Q

What is metallic bonding?

A

+ve ions in a sea of -ve bonding electrons

22
Q

What is covalent bonding?

A

Bonding electrons shared between two atoms

23
Q

What is the equation for bond stiffness?

A

S=Ea.

a. is the interatomic distances

24
Q

What is the equation for Poisson’s Ratio?

A

v=(transverse strain)/(longitudinal strain)

25
Q

What is the FCC stacking sequence?

A

ABCABCABC

26
Q

80 Hb 12/1427/30

Explain this

A 
80 is the hardness
Hb is the type of test
12 is the ball diameter
1427 is the load in kgfmm^-2
30 is the load duration in seconds
27
Q

How many Newtons in 1kgf?

A

9.81 Newtons =1kgf

28
Q

What is stress intensity factor (k)?

What is the formula?

A

The stress intensity factor (K) is used in the field of fracture mechanics. It predicts stress intensity near the tip of a crack caused by a remote load or residual stresses.

Let ó=stress

K=Yó(pi*a)^0.5
a is the crack size
Y is the geometry factor (calculated)

29
Q

Name the four processes in the Carnot cycle.

A

Isothermal Expansion 》Isentropic Expansion 》Isothermal Compression 》Isentropic Compression

30
Q

Define adiabatic.

A

Relating to or denoting a process or condition in which heat does not enter or leave the system concerned.

“the adiabatic expansion of a perfect gas”

31
Q

Define Toughness.

A

A measure of a materials ability to deform plastically without fracturing, as measured by the energy under the stress strain curve

32
Q

Strength - define it

A

The measure of a materials resistance to plastic deformation

33
Q

What are the four types of “impurities” that mean a material can never really reach its theoretical strength?

A
  • Vacancy
  • Interstitial Atom
  • Interstitial Impurity Atom
  • Substitutional Impurity Atom
34
Q

What is theoretical strength approximately equal to?

A

E/3

35
Q

Define stiffness?

A

The resistance of a material to deformation under an applied force

36
Q

Define stiffness?

A

The resistance of a material to deformation under an applied force

37
Q

What does the Frenkel Model represent?

A

The frenkel model predicts the critical shear stress of two closed packed planes sliding over each other.

38
Q

Why is the Frenkel Model too simplistic?

A

It predicts that the stress can only vary sinusoidally. It doesn’t consider a linear defect separating slipped from unslipped regions. No consideration is given to dislocations.

39
Q

What are the three main primary bonds? How do they relate to a material’s stiffness?

A

Covalent - Highest bond stiffness
Metallic - Medium bond stiffness
Ionic - Lower bond stiffness

40
Q

What is a covalent bond?

A

Pairs of electrons are shared by two adjacent atoms.

41
Q

What is a metallic bond?

A

The sharing of free electrons in a lattice of positively charged ions.

42
Q

What is ionic bonding?

A

The bond formed by electrostatic attraction between positively and negatively charged species. Electrons are shared because sharing is caring.

43
Q

What happens to a shear thinning fluid as a shear stress is applied.

A

It becomes LESS viscous.

44
Q

What is a saturated liquid?

A

A liquid that is on the verge of boiling.

45
Q

What is a compressed liquid?

A

A stable liquid that is either at a lower temperature or a higher pressure than a saturated liquid.

46
Q

What is a saturated vapour?

A

A vapour that is on the verge of condensing.

47
Q

What is a superheated vapour?

A

A stable vapour that is either at a lower pressure or higher temperature than a saturated vapour.

48
Q

Why does the Carnot cycle have the maximum possible efficiency?

A
  • The rectangle has the maximum possible area for the given temperatures.
  • The isentropic processes are impossible to engineer in real life
  • All of the heat is added at the maximum temperature
49
Q

For the Carnot cycle, what is the compressor/turbine order?

A
  • Isothermal Turbine
  • Isentropic Turbine
  • Isothermal Compressor
  • Isentropic Compressor
50
Q

For an ISENTROPIC feed pump. How do you calculate the change in enthalpy?

A

dh=v(p2-p1)

51
Q

True or false, for your true stress strain curve. Your true stress strain equals n (your power).

A

TRUE

52
Q

What is the equation for Bulk Modulus.

A

B=E/3(1-2v)

Mec132 (1 decks)

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