eLFH - Density and Viscosity

Question 1

Density definition and equation

Answer 1

Mass per unit volume

Density = mass / volume

Question 2

Effect of pressure on density / viscosity

Answer 2

Increased pressure increases density and viscosity

More particles in a smaller area

Question 3

Effect of temperature on density / viscosity

Answer 3

Increased temperature reduces density and viscosity

Higher average kinetic energy of molecules within the gas so particles move further apart

Question 4

Specific gravity of gases definition

Answer 4

Density of the gas divided by the density of air (1.2 kg/m^3)

Question 5

Specific gravity of gases interpretation

Answer 5

Gases with specific gravity > 1 are more dense than air
< 1 less dense than air

Question 6

Specific gravity of liquids and solids

Answer 6

Density is compared with density or water

Question 7

Viscosity definition

Answer 7

Tendency of a fluid to resist flow
Denoted with Greek letter Eta (η) (or sometimes Mu)

Question 8

Units of viscosity

Answer 8

Poise (P)

Question 9

Newtonian fluid

Answer 9

Fluid where viscosity is unaffected by the shear or tangential stresses inflicted upon it

Viscosity solely dependent on temperature and pressure

Most gases are Newtonian fluids

Question 10

Non-Newtonian fluid

Answer 10

Fluid which may deform when stirred or become less viscous

Question 11

SI units of flow

Answer 11

kg/s

Question 12

Types of flow

Answer 12

Laminar - streamlined flow in smooth layers

Turbulent - interrupted flow with swirls

Question 13

Importance of viscosity vs density in laminar vs turbulent flow

Answer 13

Viscosity more important in laminar flow

Density more important in turbulent flow

Question 14

Hagen-Poiseuille equation

Answer 14

Can be used for laminar flow only, not turbulent flow

Question 15

Where does turbulent flow occur in a tube

Answer 15

At and orifice

Question 16

Orifice definition

Answer 16

Tube in which diameter exceeds length

Question 17

How to measure gas flow

Answer 17

Rotameter:
Uses bobbin of fixed size
Moves up and down as pressure from gas flow pushes bobbin up until gravitational force pushing down counteracts it and pressure across the bobbin is constant

Flow calculated from Poiseuille’s law and pressure to give flow

Question 18

Which part of bobbin to read flow from

Answer 18

Top of a flat topped bobbin

Middle of a sphere bobbin

Question 19

Colour of oxygen cylinder

Answer 19

Black with white collar

Question 20

Atomic weight of oxygen

Answer 20

16

Question 21

Molecular weight of oxygen

Answer 21

32
As is O2 molecule

Question 22

How is oxygen produced for hospital use

Answer 22

Fractional distillation of air

Question 23

Colour of nitrous oxide (N2O) cylinder

Answer 23

Completely blue

Question 24

How is nitrous oxide produced for medical use

Answer 24

Heating ammonium nitrate and extracting N2O from impurities

Question 25

Why can't use nitrous oxide in pneumothorax or ophthalmic surgery

Answer 25

Nitrous oxide 40x more soluble than nitrogen Diffuses into air filled cavities faster than nitrogen can diffuse out and therefore increases size if air filled cavities

Question 26

How is Entonox produced

Answer 26

Bubbling oxygen through liquid nitrous oxide (Poynting effect) 50% N2O + 50% O2

Question 27

Colour of Entonox cylinder

Answer 27

Blue with blue and white collar

Question 28

Safety point for Entonox storage

Answer 28

Pseudocritical temperature -5.5 degrees Celsius at 117 bar and -7 degrees at 137 bar Therefore cylinders must be kept above this temperature to prevent liquefaction and hence separation out of N2O which can lead to delivery of hypoxic mixture

Question 29

Colour of CO2 cylinder

Answer 29

Completely grey

Question 30

How is Carbon dioxide produced for medical use

Answer 30

heating calcium carbonate or magnesium carbonate

Question 31

Colour of helium cylinder

Answer 31

Completely brown

Question 32

Features / medical use of helium

Answer 32

Lower density but higher viscosity than nitrogen Therefore in upper airway obstruction where turbulent flow is present, Helium-oxygen mixture will increase flow compared with nitrogen-oxygen mixture

Question 33

Heliox

Answer 33

Helium-oxygen mixture 79% helium 21% Oxygen

Question 34

Colour of Heliox cylinder

Answer 34

Black with Brown and White collar

Question 35

Boiling point of oxygen

Answer 35

-183 degrees Celsius

Question 36

Melting point of oxygen

Answer 36

-219 degrees Celsius

Question 37

Critical temperature of oxygen

Answer 37

-118 degrees Celsius

Question 38

Critical pressure of oxygen

Answer 38

50 Bar

Question 39

Saturated vapour pressure of oxygen at 20 degrees Celsius

Answer 39

1.4 Bar

Question 40

Boiling point of Nitrous oxide

Answer 40

-88 degrees Celsius

Question 41

Melting point of Nitrous oxide

Answer 41

-91 degrees Celsius

Question 42

Critical temperature of Nitrous oxide

Answer 42

36.5 degrees Celsius

Question 43

Critical pressure of Nitrous oxide

Answer 43

72 Bar

Question 44

Saturated vapour pressure of Nitrous oxide at 20 degrees Celsius

Answer 44

50.8 Bar

Question 45

Boiling point of CO2

Answer 45

-79 degrees Celsius

Question 46

Melting point of CO2

Answer 46

-57 degrees Celsius

Question 47

Critical temperature of CO2

Answer 47

30 degrees Celsius

Question 48

Critical pressure of CO2

Answer 48

73 Bar

Question 49

Saturated vapour pressure of CO2 at 20 degrees Celsius

Answer 49

57 Bar

Question 50

Boiling point of helium

Answer 50

-269 degrees Celsius

Question 51

Melting point of helium

Answer 51

-272 degrees Celsius

Question 52

Critical temperature of helium

Answer 52

-268 degrees Celsius

Question 53

Critical pressure of helium

Answer 53

2.3 Bar

Question 54

Saturated vapour pressure of helium at 20 degrees Celsius

Answer 54

N/A

Question 55

Reynold's number definition

Answer 55

Dimensionless number which predicts likelihood of laminar or turbulent flow Not absolute

Question 56

Reynold's number equation

Answer 56

Reynold's number = (Velocity of fluid x density of fluid x diameter of tube) / viscosity of fluid

Question 57

Reynold's number interpretation

Answer 57

< 2000 predicts laminar flow 2000 - 4000 predicts transitional flow > 4000 predicts turbulent flow