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Branddynamik 2 HT22 > Lektionsteori HT22 av Oisik > Flashcards

Lektionsteori HT22 av Oisik Flashcards

1
Q

Vad är det vanligaste sättet för en eld att dö på?

A

Rök

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2
Q

Beskriv fallet av ett stängt rum

A

lite läckage = högt tryck

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3
Q

Beskrivfallet av ett öppet rum

A

Mycket läckage och lågt tryck

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4
Q

What is CV?

A

Control volume: a volume in space, from a substance a substance flows

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5
Q

What is CS?

A

Control surface: the surface that surrounds the control volume

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6
Q

Beskriv: Case 1 ( 1 opening - a small opening)

A

HHR will increase pressure
Mass will flow out
No mass can come in

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7
Q

Beskriv: Case 2 (more openings or bigger openings)

A

Low pressure
Less build-up of dynamic pressure
Mass will flow in and out
Flow determined by hydrostatic pressure differences across the opening

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8
Q

Vad är entalpi?

A

Mängden lagrad (energi) i ett ämne, som sedan blir värme

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9
Q

Vad är entropi?

A

En grad av oordning i ett system

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10
Q

Pressure builds up and smoke filling depends on:

A

geometry and ventilations

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11
Q

Pressure build up fast in a _____ Room ____

A

Small room
With less or no ventialtion

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12
Q

The ways by which energy can travel between a system and its surroundings

A

Heat, Work, and energy contained in the mass

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13
Q

HRR must take into account of

A

Heat loss to the boundaries or CS

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14
Q

Pressure builds up in a ___ room with ___

A

small
no or very little ventialtions

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15
Q

Combustion products are affected by _____ entrainment in plume and also the mass flow
out through a vent- species concentration in hot layer changes.

A

Cold air

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16
Q

Species concentration shoulc be determed by considering __________________________ and the

A

mass balance

region of interest

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17
Q

Name some thing about complete combustion

A

combustion under sufficient O2
usually blue flame
no smoke
CO2 as primary by- product
More energy produced than incomplete combustion ( compered to same fuel and amount)

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18
Q

Name some thing about incomplete combustion

A

Combustion under insufficent O2
Usually yellow flame
Smoke produced
CO as a primary by-product
Less energy is produced than complete combustion ( when combusting similar amount of fuel)

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19
Q

The nature of combustion products depends on following:

A
  • Type of bombustion (falming/smouldering/ thermal decompositions)
  • The availibilty of air
  • Presence of chemical agents to retard fire
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20
Q

Give following effect of the substances
A. Inorganic gases
B. Lighter organic substance
C. Heavier organic substance
D. Particles

A

A. Suffocation by CO and HCN
Irritant by HCl, HF and NOx

B. Irritant, Allergy, Cancer

C. Longterm effect: Cancer

D. Risk: Reduced visibility
Heat radiation
Damage to the lungs
Transport toxic substances

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21
Q

For cambustions, availability of air is a significant factor
name following:
1. over ventilated or fuel lean
2. under ventilated or fuel lean
3. a perfect mixture of fuel and O2 to cause complete combustion

A
  1. Abundant air
  2. Insufficient air
  3. Stoichmetry
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22
Q

What is the difference between:
1. Yi = mi/m
2. yi =mi/mf

A

Small y: Yeild of species
Big Y: Mass fraction of species

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23
Q

Vad heter den europeiska standarden för spjäll?

A

EN 13501-3

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24
Q

Var beskrivs provningsmetoden för spjäll

A

Den beskrivs i EN 1366-2, medger i kallt tillstånd och enbart i brandteknisk klass E

25
Q

Rökdetektorns utformning kan verfieras enligt SS-EN…..

A

SS-EN 54-7

26
Q

Spjäll kan veriferas enligt SS-EN …..

A

SS-EN 15650

27
Q

Ventilationssystem
Vad är fläktens uppgift?

A

Fläktens uppgift är att ge önskat luftflöde med tillräckligt tryck för att övervinna tryckfallet i ventilationssystemet. Flöde och tryck bestäms av fläktens storlek och varvtal.

28
Q

Ventilations, Vad betecknar CAV?

A

Konstant flöde

29
Q

Vad betecknar VAV?

A

Variabla flöden, (kallas också behovsstyrd ventilation

30
Q

Vad betyder FT-system? och vad är FTX-system?

A

Från och tilluftssystem, vid energiåtervinnings. Benämns ofta som mekaniska från och tillluftsystem där mekaniska syftar på fläktarna

31
Q

F- system vad är det?

A

Mekaniskt frånlufts system

32
Q

Ur brandsynpunkt, Vad finns det för och nackdelar med F respektive FT- system?

A

F system större tryckavlastning, samlings kanalen blir flaskhalsen.
FT större brandtryck eftersom det är system som är styrt och tätare. FT system är känsligare i tryckändringar och riktningen kan vändas. Därav trycks gaser lättare runt i byggnaden

33
Q

Vad skiljer serie och parallellkopplat ventilationssystem?

A

I ett seriekopplat ökar risken för att rök och avgaser skall tryckas över till andra lägenheter.

34
Q

According to some (wink wink), there are four things essential to cause a fire. These are heat, oxygen, fuel and free radicals. However, what might be the reason that free radicals may not be an essential aspect to cause a fire?

A

The removal of free radicals does not alter the burning process.

35
Q

What is formed as a result of incomplete combustion inside the flame of a candle?

A

An Allotrope of carbon

36
Q

During flashover in a room fire, what is the average heat flux towards the floor?

A

20 kW/m2

37
Q

In a room fire, more air might be entrained leading to more smoke. This is possible in a room geometry that has______and in this case the gas temperature will be______.

A

High ceiling + low gas temp

38
Q

Evelina has started a fire in her room and Emilie is standing outside of that room. The fire eventually becomes a fully developed one. Emilie touched the room wall from the outside. In another room, Johannes have started a fire and Harald is outside of that room. After the fire has become fully developed, Harald, touches the wall from the outside. Both the rooms have a temperature of ca. 1200 ℃. The conductivity and density of the rooms are the same but somehow Harald burnt his hands completely (I mean, its 3rd degree burn!!). Which room have a relatively higher heat capacity?

A

Johannes

39
Q

Why some alcohols have no diameter dependence when they burn in a pool fire?

A

They have flame that is not visible and They have no radiative heat transfer to the surface

40
Q

When determining the mean flame height experimentally, the visible flame height over time is averaged. This is because:

A

Luminosity of lower part of flame is steady whereas upper part fluctuates.

41
Q

In which plume equations, a Gaussian profile is used?

A

NOT Zukoski, McCaffrey or Thomas

42
Q

Mauritz is a big fan of 80s rock and roll and he has built a rocket after listening to the song, “The final countdown.” He powers his rocket using boron and then leaves earth. What will be the colour of Mauritz’s rocket’s exhaust and what will be the rate of pressure reduction as he moves away from the earth’s surface?

A

Green and at 10 N/m2.

43
Q

The heat flux per unit area when conduction occurs through a solid for a long time is:

A

k/δ

44
Q

What are the various stages of a typical room fire? Explain those in a few words and show them all together using a graph. Also include the phenomenon of backdraft and show it in the graph.

A
  1. Flashover: The hot layer is so hot and can ignite all the area in the room. Sudden increse in energy release rate accours. Usally around 500-600 degree celcius
  2. Fully developed fire: The interedroom is ignited and flames are hitting out though the openings.
  3. Decay: The fire starts to burn out, this can be due to oxygen starvation or fuel starvation.
  4. Ignition: the fire gets ignited and starting to go over to growht phase
  5. Growth: The fire gets more strong and starts to form a hot layer in the room. This hot layer growand will get biggeras secondaryfuel ignites.
  6. Flashover: The hot layer is so hot and can ignite all the area in the room. Sudden increse in energy release rate accours. Usally around 500-600 degree celcius
  7. Fully developed fire: The interedroom is ignited and flames are hitting out though the openings.
  8. Decay: The fire starts to burn out, this can be due to oxygen starvation or fuel starvation.
    When the fire comes to oxygen dependens two thing can happand
  9. dies due to lack of oxygen
    2.More oxygen come in and during a smolering fire, the surface is so hot all over the room fire so the fire becomes fully devlop again. This is thefas proscess called backdraft and had killed many firemans though out the years. By opening up the room you let the hot gases leave the room and the risk of a backdraft gets lower.
45
Q

Standard brandkurvan nummer

A

ISO 834

46
Q

Whick fire signature may be used to detect the following?
- Gasoline fire outdoors
- Gasoline fire indoors
- Fire at floor level indoors
- Fire from wood indoors

A

Fyll i svar på denna

47
Q

What are the advantages of IR- detector

A

Insensivtive to dust and dirt
Fast
Insensitive to solar radiation, flashes, x-ray, arcs etc…
Less sensitive ro black body radiation

48
Q

What are the disadvantages of IR- detector

A

Only detect fires that produce CO2 and might give a false alarm due to water, ice, sunlight reflection or radiant objects

49
Q

UV detectors advantages

A

Very fast
can detect many types of fires
insensitiv to solar radiation

50
Q

UV detector disadvantages

A

False alarm: sensitive to oily films, organic compounds, lightning etc

51
Q

UV/IR detectors advantages

A

Very fast, less than 500 ms
Insensitive to black body radiation
Insensitive to solar radiation
Insensitive to welding, flashes, X-rays, sparks and arcs

52
Q

UV/IR detecors disadvantages

A

Only detects fires that produces CO2
Some gases can block UV radiation and prevent detection
Smoke blocks UV radiation- the detector
must be positioned so that the fire is not obscured by fire gases
Water and ice on the lens can make detection difficult

53
Q

Gas (catalytic) detectors advantages

A

Cost-effective/economical
Can detect many different combustible gases

54
Q

Gas (catalytic) detectors disadvangese

A

Not suitable for detection of early fire
Must be calibrated frequently
Consumed over time
May become contaminated

55
Q

Gas (Electrochemical) detectors disadvangese

A
  • Consumed over time
  • May become contaminated
56
Q

Gas (Electrochemical) detectors advangese

A

Very sensitive (only requires a few ppm)

57
Q

Gas (IR) detectors advangese

A

Can detect many different types of hydrocarbons
Durable
Requires less maintenance

58
Q

Gas (IR) detectors disadvangese

A

May not be suitable for early fire detection

Branddynamik 2 HT22 (9 decks)

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