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Physics > 6. Temperature & humidity > Flashcards

6. Temperature & humidity Flashcards

1
Q

What is absolute humidity

whats it in the upper trachea

A

amount of water bappour per unit volume of gas at given temp and pressure

34g/m3
34mg/l

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2
Q

Gas driven nebuliser droplet size & humidity

A

2-4um droplets
deposited upper airway
60g/m3

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3
Q

Ultrasonic neb
size
absolute humid
problems

A

<2um - capable reach alveloi
Absolute humid 90g.m3
Over-hydration - flood lung
increase resistance

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4
Q

Cold and hot water baths abs humidity

problems

A

produce an absolute humidity of 10 and 40 g/m

Hot - airway burns if water trap not used

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5
Q

HME benefit
abs humidity

how efficient

A

Retain heat+; moisture from expire gas
Cheap
Abs humid 25g/m3 (rel 60-80%)

> 70% efficient
not more efficient and effective as ambient temp inspired gas increases

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6
Q

IR principle

A

Stefan Boltzmann eqn

Directly related to the fourth power of the temperature.

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7
Q

Metal oxide Thermistor Principle

A

Change in electrical resistance
Wheatstone is part but not the principle

resitsance falls exponentuially with increase temp

Difficult claiblrate

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8
Q

Liquid expansion thermometers principle - Mercury

A

Thermal expansivity

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9
Q

Platinum wire principles

A

Electrical resistance

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10
Q

Thermocouple Relies on

A

Seebeck effect is
temperature between two dissimilar electrical conductors or semiconductors
produces a voltage difference between the two metals.

temp increase - flow increase

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11
Q

What is temperature

A

Property of system determins if heat is transferred to or from other systems

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12
Q

What in kelvin, C & F are
Absolute 0
Melting point Ice
Boiling point water

A

Abs 0
0 kelvin, -273.15°C or -459°F

Melting point Ice
273.15 kelvin, 0°C or 32°F

BP water
373 kelvin, 100°C or 212°F.

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13
Q

Triple point of water

what is it & temps

A

Water exists simultaneously in solid, liquid and gaseous states
273.16 K or 0.01°C

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14
Q

Mercury solidify at temp C

A

-38.87°C, so is a liquid at -37°C.

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15
Q

Absolute humidity

Depends on

A

Mass of water vapour present - given volume of air, g/m3 or mg/litre

Maximum water vapour present in a given volume air determined - temperature (both ambient and body).

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16
Q

Abs humidity can be increased

A

Tmperature increases the amount of water which can be present as vapour also increases

Hence fully saturated air at 20°C contains about 17 g/m3 whereas at 37°C it contains 44 g/m3 when saturated.

17
Q

fully saturated air at 20° abs humidt

A

17g/m3

18
Q

Increase temperature
To humidity
relative humidity
dew point

A

crease in temperature produces:

Increased absolute humidity
The same relative humidity
Increased dew point temperature.

19
Q

Decrease or increase in barometric pressure affect on humidty

A

No change in absolute or relative humidity and dew point temperature.

20
Q

Thermocouple
is
used
Consists of (what)

What happens when contact

A

A thermocouple is a device that is used to measure temperature ‘electronically’.
It consists of a pair of dissimilar metal wires or strips bonded together, typically copper and constantan (an alloy of 55% copper and 45% nickel).

When these wires contact each other, a small voltage is generated in the order of millivolts.
The magnitude of the thermojunction electromotive force (EMF) is proportional to applied temperature (the Seebeck effect).
This physical principle can be applied to the measurement of temperature. The electromotive force at the measuring junction is proportional to temperature.

Two wires bonded together with different coefficients of expansion can be used as a switch for thermostatic control.

The resistance of the measuring junction of a thermocouple is irrelevant.

The resistance of a platinum wire varies LINEARLY with temperature and the resistance of a thermistor varies exponentially with temperature. This unknown resistance is incorporated into a Wheatstone bridge to indirectly measure temperature.

21
Q

Hygrometer

A

measure humidity.
By inserting a water-absorbing substance between the two plates, this has an effect on the resistance between the plates of the capacitor. The resultant change can be directly related to humidity.

22
Q

Thermistor - response time

A

Response time any electrical device measure temp
-> size + material
mainly size
length width and site no relevance

smaller - smaller spec heat capacity = react quicker
.1-15sec

23
Q

Filtration

A
  1. Direct inteception - >1um - too large to pass
  2. Inertial impaction 0.5-1um - collide w/ fibres held by VdW

3 Diffusion interception -[ small particle - sml mass - constant movement - inevitbale collision w, fibres

  1. Electrostati cttaction - charged

5 gravitational setting - large particles

24
Q

Triple point

A
  1. 01C

273. 16K

25
Q

Mercury therm take how long equil

A

2-3 mins

Poisonous

Freezes at -39C
Boils >250

26
Q

Alcohol freezing and BP

A

-117 + 78.5

27
Q

At absolute 0 an ideal gas

A

occupies 0 volume

28
Q

Humidity 1cm air at 20c

A

17g m3

29
Q

Humidity upper trach at 37

A

34

30
Q

humid lower trach 37

A

44g m3

31
Q

Humidity can be asses

measured

A

uv light transmission

measured blowing air thru ether - determine dew point in regnaults hygrometer

using hair hygrometer - accurate detecting humidity 30-90%

32
Q

temp loss %

A

1 radiation 40-60% - ir rad patient to second system not direct contact - lower temp
prop to enciro core diff ^ 4

2 convection 30%
heat lose - air immed surround body - loss proport veolicty air

3 evaporation 8-15%

resp 8-10%

condcution
5%

33
Q

Latent heat of vaporisation

water

at zero is

A

It is defined as the heat required to change one mole of liquid at its boiling point under standard atmospheric pressure. It is expressed as kg/mol or kJ/kg.

decrease with water is curved

its crit temp

34
Q

Ntitrous oxide - latent heat

A

heat energy from liq N2O -> vapor

pressure falls - pressure decrease cooling

35
Q

Viscosit of a gas w increase temp

A

increase - more energy

36
Q

Viscosity liquid

A

reduces vdw forces - viscosity decreases

37
Q

Effifiency low to high of humidification

A

cold water bubble thru

HME
change reg - mositure accum inc resist

Heated water bath
(40-45C)

Heated bernoulli neb + anvil

U/S neb

38
Q

Latent heat vaporization trachea

how avoided

how much lost warming

A

15% heat loss in trachea

humidifaction

2% basal heat lost warm gas

more heat lost humdifying vs warming

39
Q

Specific heat capactiy

mean value for tissue spec heat capcicty of person

gases high or low spec heat capcity

water spec heat cap

radiation proport to what

A

amt heat required raise temp 1kg sub by 1 kelvin (specific bit = 1kg)

3.5Kj/Kg per C

Gases low spec heat cap (low density)

Water = 4.18Kj / K

radiation is proportional to 4th power of absolute temperature

Physics (11 decks)

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