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