3. Gas Flow & Measurement Flashcards
Flowmeters
Calibration?
Accuracy
Improved w/?
Measure flow rate gas pass thru
Individually calibrated gas
+/- 2%
Stannic Oxide -antistatic substance - reduce risk sticking
Where read from
When is O2 added
Top bobbin
Midpoint ball
Last gas added - prevents hypoxic mixture
CO2 still used?
Rates
Old machine
500ml/min - avoid hypercarbic
Turbulent flow
p
proport to
when p-v plotted
what shape
R2x Sq root pressure diff / L x density
Flow proport square root pressure diference
flow direct proport 1 divided square root length tube
flow direct proport 1 / square root denisty fluid
r = radius, L = length of tube, ΔP = pressure difference and ρ = density.
Flow is therefore inversely proportional to density and length and directly proportional to the pressure difference.
Relationship - pressure and flow - non linera
plotted = parabola
Air/O2 entrainment
100% − FiO2 = air/oxygen entrainment ratio
____________
FiO2 − 21%
Total flow =
=source gas flow + source gas flow × entrainment gas ratio
Beers Law
absorption of radiation by a given thickness of a solution of a given concentration same as that of twice the thickness of a solution of half the concentration
Bougner’s (or Lambert’s) law states
each layer of equal thickness absorbs an equal fraction of radiation which passes through it.
Boyle’s law states
that at constant temperature the volume of a given mass of gas varies inversely with absolute pressure.
Graham’s law states
that the rate of diffusion of a gas is inversely proportional to the square root of molecular weight.
Raoult’s law states
that the depression or reduction of vapour pressure of a solvent is proportional to the molar concentration of the solute.
Wave lengths in order shortest:
Xr, IR, UV, Visible, gamma
Gamma <10pm
Xray 0.01-10nm
IR 1 mm and 750 nm
Visible 400-700 nm
UV 100-400 nm (volatile)
Radio 100mm- 10000km
Carbon Dioxide
Produced
Density (& vs air)
Bond
Reactivity
BP
Crit temp
when does it turn dry ice
Crit pressure
Dissoc curve
Gas room temp
produced by the oxidation of carbon-containing substances / heating calcium (or magnesium) carbonate.
Its density at 298K is 1.98 kg/m3, about 1.5 times that of air.
The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole.
As it is fully oxidised, it is not very reactive and in particular not flammable.
It has a boiling point of -79°C and a critical temperature of 31.2°C (not minus 31°C).
At temperatures below -78°C, carbon dioxide condenses into a white solid called dry ice.
Liquid carbon dioxide forms only at pressures above 5.1 atm; at atmospheric pressure,
it passes directly between the gaseous and solid phases in a process called sublimation.
The carbon dioxide dissociation curve is steeper and more linear than the oxygen dissociation curve.
Rotameter Shape Forces Flow @ high & low flows Calibrated @ atmos - altitide & hyperbaric
Vertical tapered tube - small bottom
Downward force on it caused by gravity is equal to the upward force caused by gas molecule
low flow is a function of the viscosity of the gas Poiseuille’s law
high flow, flow depends on the density of the gas Graham’s law
Hyperbaric chamber, a flowmeter will deliver less gas than the setting
Increasing barometric pressure (as happens with increasing altitude), the actual flow rate will be higher than the flowmeter reading
Crit temp
Crit pressure
Of
oxygen
co2
nitrous
Crit temp
temp above sub cant be liquefy by pressure alone
cirt pressure = press required to liqeufy vapour
-118 50
31 73
36.5 72
Critical temp =
temp above which gas can no longer liquefy any amt pressure
