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Flashcards in Thermofluids Deck (52)
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1

What is the second law of thermodynamics?

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

2

What is the first law of thermodynamics?

/\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

3

What type of process does a throttle valve represent?

An ISENTHALPIC one.

4

Define isentropic.

No change in entropy. This is ideal.

5

Define viscosity.

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

6

What is the specific volume of a substance?

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

7

What is absolute pressure?

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

8

What is gauge pressure?

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

9

Name 3 properties of an ideal gas

-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

10

What is the purpose of a U-tub manometer?

To measure the difference between two unknown pressures.

11

What is Bernoulli's Equation?

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

12

When does cavitation occur?

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

13

What is the critical Reynolds number?

2000

14

What is incompressible flow?

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

15

Define inviscid flow.

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

16

What is a Newtonian fluid?

A fluid with a constant viscosity.

17

What does HCP mean? What is the stacking sequence?

Hexagonal closed packed.
Stacking sequence is ABABABAB

18

What is atomic packing fraction?

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

19

How many atoms in a bcc and fcc cubic?

fcc cubic = 4 atoms per unit cell
bcc cubic = 2 atoms per unit cell

20

What is ionic bonding?

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

21

What is metallic bonding?

+ve ions in a sea of -ve bonding electrons

22

What is covalent bonding?

Bonding electrons shared between two atoms

23

What is the equation for bond stiffness?

S=Ea.
a. is the interatomic distances

24

What is the equation for Poisson's Ratio?

v=(transverse strain)/(longitudinal strain)

25

What is the FCC stacking sequence?

ABCABCABC

26

80 Hb 12/1427/30

Explain this

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

How many Newtons in 1kgf?

9.81 Newtons =1kgf

28

What is stress intensity factor (k)?
What is the formula?

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

Name the four processes in the Carnot cycle.

Isothermal Expansion 》Isentropic Expansion 》Isothermal Compression 》Isentropic Compression

30

Define adiabatic.

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"