Fire Engineering Principles Workbook

Transcription

1 F Fire Engineering Principles Workbook R C The aim of this course is to enable the student to understand fundamental Fire Engineering Principles. It will give you the basic principles and underlying principles you need to carry out a Fire Engineered solution. It will also go through fundamental mathematical principles that Fire Engineers should have.

2 Contents Page Module 1 Basic principles of Fire Engineering 3 Module 2 Determining fire size 4 Module 3 Misconceptions 4 Module 4 What is CFD modelling? 4 Module 5 Fire modelling 4 Module 6 Case studies 5 Module 7 Application of fire modelling 5 Module 8 Fire Engineering strategy 5 Module 9 Shopping mall engineering strategy 5 Module 10 Block of flats Engineering strategy 6 Module 11 Smoke control strategy for care premises 6 Module 12 Full Fire Strategy 1 6 Module 13 Full Fire Strategy 2 6 Module 14 Full Fire Strategy 3 6 Module 15 Full Fire Strategy 4 6 Module 16 The Cone Calorimeter 6 Module 17 Porta level 7

3 Module 18 Timber framed analysis 1 7 Module 19 Timber framed analysis 2 7 Module 20 Timber framed analysis 3 7 Module 21 Probabilistic analysis 7 Module 22 Bernoulli principle 13 Module 23 Question1 14 Module 24 Question 2 15 Module 25 Question 3 16 Module 26 Question 4 17 Module 27 Question 5 18 Module 28 Question 6 19 Module 29 Dimensional analysis 20 Module 30 Differentiation 24 Module 31 Integration 1 28 Module 32 Integration 2 28 Module 33 Fires in compartments 1 40 Module 34 Fires in compartments 2 44 Module 35 Fires in compartments 3 44 Module 36 Fires in compartments 4 51 Module 37 Sprinkler calculations 1 58 Module 38 Sprinkler calculations 2 58

4 Module 1 Fire Engineering introduction This module will look at the principles of fire engineering and the core competencies that a fire engineer should possess. Module 1 This module covers the following topics: Basic principles of Fire Engineering History of Fire Engineering What is Fire Engineering? Role of Fire Engineer Fire Engineering approaches available Fire Engineering Competence.

5 . Module 2 This module covers the following topics: Determining fire size Design approaches Liaison with Fire Service Advantages of Fire Engineered Solution Disadvantages of Fire Engineered Solution Are some Fire Engineered Solutions flawed? Guidance documents Main factors to consider with Fire Engineered solution.. Module 3 This module covers the following topics: Misconceptions What if? Qualitative Design Review Published documents Assessment against criteria Competencies Module 4 This module covers the following topics: What is CFD modelling Case Studies Module 5 This module covers the following topics: Fire Modelling FDS Impulse fans Smoke control in flats - CFD Various CFD Models CIBSE Guide E

6 Module 6 This module covers the following topics: Case Studies.. Module 7 This module covers the following topics: Reconstruction using fire modelling Application of fire models Issues with smoke control in blocks of flats Module 8 This module covers the following topics; Fire engineered strategy introduction Module 9 This module covers the following topics;. Fire engineered strategy for shopping complex. Module 10 This module covers the following topics; Fire engineered strategy for block of flats.

7 Module 11 This module covers the following topics; Fire engineered strategy for smoke control system to be installed in a care premises Module 12 This module covers the following topics; Full fire engineered strategy using a performance base approach Part 1 Module 13 This module covers the following topics; Full fire engineered strategy using a performance base approach Part 2 Module 14 This module covers the following topics; Full fire engineered strategy using a performance base approach Part 3 Module 15 This module covers the following topics; Full fire engineered strategy using a performance base approach Part 4 Module 16 This module covers the following topics; The cone calorimeter

8 Module 17 This module covers the following topics; The porta-level Module 18 This module covers the following topics; Timber framed analysis 1 Module 19 This module covers the following topics; Timber framed analysis 2 Module 20 This module covers the following topics; Timber framed analysis 3 Module 21 This module covers the following topics; Probablistic analysis

9 Unravelling the mystery surrounding Bernoulli s Daniel Bernoulli was a Dutch born Swiss Scientist, who discovered basic principles of fluids. The Bernoulli principle is that a fluid (liquid or gas) in motion can have three types of energy Potential energy Kinetic energy Pressure energy These can be interchanged but unless energy is taken out (e.g. turbulence or friction) or energy is put in (e.g. pump) then the total energy must be constant. The frictional loss is neglected in calculations due to being small compared to the total energy, however, you must consider frictional loss in certain circumstances e.g. sprinkler calculations To use Bernoulli s theorem in calculations it is important to have all three forms of energy in the same units. The Systems International (SI) unit for energy is the Joule (kg.m 2 /s 2 ) however; when using Bernoulli the energy is expressed per unit mass or per unit volume. Therefore, there are different forms of the Bernoulli Equation depending on whether we are working with either joules per kilogram (j/kg) or joules per meter cubed (j/m 3 ). In order to simplify the matter, I am only going to use the Bernoulli Equation that expresses the energy in the form of joules per metre 3 (j/m 3 ) which I believe is easier to apply to IFE examination questions. Potential energy This is the energy due to the potential above the datum line from which all the energies are measured. The potential energy per m 3 of fluid can be considered as Where ρgo (Joules/m 3 ) p = density (kg/m 3 ) g = acceleration due to gravity (9.81 m/sec 2 ) H = height (m) Kinetic energy The kinetic energy is due to the fluid being in motion. The Kinetic energy can be considered as ½ ρv 2 (Joules/m 3 ) Where p = density (kg/m 3 )

10 V = Velocity (m/sec) Pressure energy The pressure energy is due to being under pressure. The SI unit of pressure is Pascal but in the Fire Service, the Bar and metres head are still used. Therefore, you must remember to use the correct formula To convert from Bar to Pascal s you use the following P X 100,000 (Joules/m 3 ) Where P = Pressure (Bar) Bernoulli Pascal s To convert metres head pressure to Pascal s, you use the following ρgz (Metres head) (Joules/m 3 ) Where ρ = Density (kg/m 3 ) g = acceleration due to gravity 9.81 m/sec 2 Where the pressure energy is Pascal s z = height (m) P A + ρgh A + ½ ρv A 2 = P B + ρgh B + ½ ρv B 2 Where P A is pressure energy at point A (joules) ρgh A is the potential energy at point A ( joules) ρ = Density of fluid (kg/m3) g = Acceleration due to gravity 9.81 m/sec H = height of column of water ½ ρv A 2 is the kinetic energy at point A (joules) V = velocity m/sec Where the pressure energy is Bar P A x 100,000+ ρgh A + ½ ρv A 2 = P B x100, 000+ ρgh B + ½ ρv B 2

11 Where the pressure energy is metres head ρgz A + ρgh A + ½ ρv A 2 = ρgz B + ρgh B + ½ ρv B 2 Continuity equation When considering Bernoulli it is also very important to understand the continuity equation. This is due to the fact that in a closed system the rate of flow Q (m 3 /sec) can be considered as constant. Q = VA Where Q = Rate of flow (m 3 /sec) V = Velocity (m/sec) A = Area (m 2 ) If the flow is constant then Q = V AA A = V BA B This is shown here in this diagram showing a pipe As the water flows down the pipe and it tapers out what you will find is that the waters velocity will reduce. In other words as the area increases the velocity falls. This is a very important relationship when attempting Bernoulli calculations as will be shown later. Before we attempt questions involving the use of these equations, I would like to give you a few tips to ensure mistakes are not made.

12 Tip one Produce a sketch and enter all the details given in the question first. understanding the problem much clearer. This will make Tip two Always convert ALL units to SI units before attempting to answer the question. Many candidates make mistakes because they don t convert the units and simply place the number in the formula.

13 Here is a list of the most common units. SI unit Length (L) m Area (A) m 2 Velocity (V) Acceleration due to gravity (g) Height (h) Metres head (z) m/sec 9.81 m/sec 2 m m Tip three Energy (joule) kg.m 2 /s 2 Pressure (Pascal) n/m 2 Volumetric flow (Q) m 3 /sec You have to place a datum line which is where you are measuring the energies from. Now if this is a horizontal pipe you always put the datum in the centre of the pipe because in this way you have zero potential at both points. This is because the potential energy above and below the datum cancels out. Now if the situation is not in a horizontal pipe for example like this example. What you do is always place your datum line at the lowest point in the system. In this way only one of the points will have potential energy and it makes it easier to answer the question. Module 22 This module covers the following topics; Bernoullis theorem (principles)

14 Bernoulli s Exercises Module 23 This module covers the following topics; Question 1 Question 1 A pump is pumping 2m 3 /min of water the surface of which is 5m below the pump inlet. At the outlet the pump has a diameter of 100mm and at this point the pressure is 8 Bar. From the nozzle (which is at the same level as the pump outlet) the jet rises 35m. A) Calculate the energy/kg of the water (1) At the outlet of the pump (2) At the top of the throw of the jet B) Explain why (1) and (2) are not equal (acceleration due to gravity is 9.81m/sec2)

15 Module 24 This module covers the following topics; Question 2 Question 2 Water is flowing horizontally through a 250mm diameter pipe and into a constriction of 100mm diameter. The pressure difference is measured as 23.5mm of mercury. Using Bernoulli s theorem, calculate the rate of flow. (Density of mercury = 13,600 kg/m 3 ) (Density of water = 1000 kg/m 3 ) ( g = 9.81) Pressure difference = 23.5mm mercury Density of mercury = 13,600 kg/m 3 )

16 Module 25 This module covers the following topics; Question 3 Question 3 A foam generator consists of a horizontal tube of circular cross section which tapers from an input of 80mm internal diameter to 20mm diameter. 750 lts/min of concentrate (Density 1200 kg/m) is flowing through the generator and the pressure inlet is 12 Bar. What is the pressure at the point where the diameter is 20mm?

17 Module 26 This module covers the following topics; Question 4 Question 4 Water is flowing in a vertical tapering pipe 2 metres in length. The top of the pipe is 100mm diameter and the bottom is 50mm diameter. The quantity of water flowing is 1300 litres/minute. Calculate the pressure difference between the top and the bottom of the pipe?

18 Module 27 This module covers the following topics; Question 5 Question 5 A pump supplies 4kw of energy to the water flowing through a 45mm hose. The water flows 15m vertically and through a 25mm branch at a rate of 500 litres/minute. Use Bernoulli s theorem and find the pressure at the branch. Make a sketch and fill all details as shown here

19 Module 28 This module covers the following topics; Question 6 Question 6 If the manometer readings are 800mm and 200mm, what is the flow? (Density of water = 1000kg/m 3 )

20 Dimension analysis Module 29 This module covers the following topics; Question 1 Dimensional analysis Determine the dimensions of the constant a? 2 Q at Where Q = Heat release rate (kw) t = seconds (s) Question 2 Determine the dimensions of the parameter R? Q H C R Where Q = Heat release rate (Kj.s -1 ) Hc = Heat of combustion (kg.s -1 )

21 Question 3 Determine the dimensions of the parameter T? T m T Q /( Mc 0 P P ) Where Q P = Heat release rate (Kj.s -1 ) M = Mass flow rate (kg.s -1 ) Cp = Specific heat capacity (kj.kg -1.K -1 ) Question 4 Determine the dimensions of the Stephan boltzman constant? I r Where f T f 4 Dimensionless Dimensionless I r = Radiative heat flux (kw.m -2 ) Tf = Temperature (K) Question 5 Determine the dimensions of the froud number Fr? Fr U gl Where U = Velocity (m.s -1 ) g = Gravity (m.s -2 ) l = Specific heat capacity (m)

22 Question 6 Determine the dimensions of the parameter H c? m f Q H c Where m f = Mass flow rate (kg.s -1 ) Q = Gravity (kj.s -1 ) Question 7 Determine the dimensions of the parameter q K? q k Where Question 8 mch A f C m c = Mass (kg) H c = Calorific value (mj.kg -1 ) A F = Floor area (m 2 ) Determine the dimensions of the parameter Q? Q m f H c Where m f = Mass flow rate (kg.s -1 ) = Calorific value (kj.kg -1 )

23 Question 9 Determine the dimensions of the parameter q K? Q * c 0 Q 1/ 2 5/ 2 pt0 g D s Where Q = Heat release rate(kj.s -1 ) C p = Heat capacity (kj.kg -1. K -1 P 0 = Ambient air density (kg.m -3 ) T 0 = Ambient air temperature (k) g = Acceleration due to gravity (m.s -2 ) D s = Linear dimension (m) Question 10 Determine the dimensions of the parameter D? D Dm f V t b Where D m = Mass optical density (m 2.kg -1 ) V t = Total volume of smoke (m 3 ) f b = Total mass of fuel (kg)

24 In this module we are going to look at differentiation. Module 30 Differentiation This module covers the following topics; Differentiation Differentiate the following formula Exercise 1 2 y x Exercise 2 3 y x

25 Exercise 3 5 y x Exercise 4 10 y x Exercise 5 y 2 x Exercise 6 y 5 x Exercise 7 11/ 2 y x Exercise 8 y 13/3 x Exercise 9 y 1 x 4

26 Exercise 10 y 1 x 2 Exercise 11 y x 6x 4 3 x Exercise y 9x 11x 7 5 x Exercise 13 y x 2 x 8 Exercise 14 y x 6 2x 9 Exercise 15 y x 10 2

27 Exercise 16 y x 3 x Exercise 17 y 4x 4 8x Exercise 18 y Exercise 19 y 1 2x 3 x 1 8x 8 x Exercise 20 y 4.5x x 2 5 x x x x 3.5

28 Integration In this module we are going to look at integration Module 31 This module covers the following topics; Integration 1 Module 32 This module covers the following topics; Integration 2

29 Exercise 1 Determine the integral of the following? F( x) 6 Exercise 2 Determine the integral of the following? F( x) x 7 Exercise 3 Determine the integral of the following? F( x) x Exercise 4 10 Determine the integral of the following? F( x) 10x 4 Exercise 5 Determine the integral of the following? F( x) 8x 12

30 Exercise 6 Determine the integral of the following? F( x) 1 x Exercise 7 Determine the integral of the following? F( x) e 2x Exercise 8 Determine the integral of the following? F( x) Exercise 9 e 4x Determine the integral of the following? F( x) e 3x Exercise 10 Determine the integral of the following? F( x) e 2x

31 Exercise 11 Determine the integral of the following? 3 8z 4z 6z 2 dz Exercise 12 Determine the integral of the following? 4 9z 5z 12z 3 dz Exercise 13 Determine the integral of the following? 8 3z 2z 4z 7 dz Five steps Step 1 Turn into form you can integrate Step 2 Integrate the formula Step 3 Substitute in the point you are given as x and y Step 4 Solve for C Step 5 Write down final answer with C in correct place

32 Exercise 14 Determine the integral of the following when you know that the curve goes through the point (3,2)? dy x dx x x Exercise 15 Determine the integral of the following when you know that the curve goes through the point (4,6)? dy dx Exercise 16 x x 2 x 3 Determine the integral of the following when you know that the curve goes through the point (1,1)? dy dx Exercise x 4x 2.5x Determine the integral of the following when you know that the curve goes through the point (2,3)? dy dx 3 2 4x 12x 2x

33 To integrate when you have simple limits you use the following method. Step 1 Integrate as normal, however don t add the C but put the results in square brackets showing the limits Step 2 Step 3 Step 4 Substitute the top limit in and evaluate it Substitute the bottom limit Subtract the value to find the answer Exercise 18 Determine the integral of the following? x 2 2xdx Exercise 19 Determine the integral of the following? x 2 x 3 xdx Exercise 20 Determine the integral of the following? x 4x 2 xdx Determining area under graph Step 1 Write down in form of integral Step 2 Integrate the formula Step 3 Evaluate it

34 Exercise 21 Determine the area under the following curve between x =1 and x = 8? y 7x x 3 3dx

35 Exercise 22 Determine the area under the following curve between x =4 and x = 10? 3 2 y 4x 3x 2xdx

36 Exercise 23 Determine the area under the following curve between x =8 and x = 12? y 6x 2 14x 5dx

37 Exercise 24 Determine the mass flow rate of smoke out of an opening 0.5m high x 1.2m wide with a slow growing fire in a banking hall over 1 minute 30 seconds? 2 1/3 Q pw0 0 m h Using 0 60 m dt w 2/3 0 h 0 a 1/3 t 5/

38 Exercise 25 Determine the mass flow rate of smoke out of an opening 0.34m high x 1.6m wide with a FAST growing fire over 2 minute 15 seconds? 2 1/3 Q pw0 0 m h Using m dt w 2/3 0 h 0 a 1/3 t 5/

39 Exercise 26 a) Determine the mass flow rate of smoke out of an opening 0.28m high x 3.4m wide with a FAST growing fire in the first 2 minutes of fire development. b) What would it have been if the fire growth rate was ultra-fast instead? 2 1/3 Q pw0 0 m h Using m dt w 2/3 0 h 0 a 1/3 t 5/

40 Compartment fires This module will cover the issue of Fires in Compartments Module 33 At the end of this presentation you will have a good understanding of: Introduction Stages in compartment fires Ceiling jet.

41 Fires in Compartment Fires Legions Of Armed Romans Tend to Fight Quickly L Locate the sprinkler, heat or smoke detector from seat of fire O Determine the operating temperature of the device A Use Alpert s equations to determine time to operate and velocity of gases R Determine RTI and apply it to determine thermal lag T Determine actual time for sprinkler operation by adding thermal lag to output from step 3 F Determine the actual fire size on sprinkler, heat or smoke operation Q Determine the quantity of water required to control fire /3 Q r T T H 5/3. Q r T T H. Q U 0.96 H 2/3 1/ 3 H r H r H U. 1/ 3 Q H r 5/ 6 1/ 2 r H 0.15

42 Exercise 1 Determine the temperature of the hot gases and gas velocity of a wall ceiling jet at a heat detector located at 0.2m from the plume in a room with a height from the base of the fire to the ceiling of 3.2m? The fire size is 450kW.

43 Exercise 2 Determine the temperature of the hot gases and gas velocity of a corner ceiling jet at a heat detector located at 0.5m from the plume in a room with a height from the base of the fire to the ceiling of 3m? The fire size is 250Kw. Exercise 3 Determine the temperature of the hot gases and gas velocity of an axi-symmetric ceiling jet at a heat detector located at 2.6m from the plume in a room with a height from the base of the fire to the ceiling of 4.6m? The fire size is 570kW.

44 Module 34 At the end of this presentation you will have a good understanding of: Fire Size 7 Step Guide Exercises. Module 35 At the end of this presentation you will have a good understanding of: Exercises utilising the 7 step guide. Exercise 4 Determine the fire size at the time the sprinkler operates in the following situation? Fast response sprinkler colour -red Assume ambient temperature is 293K Occupancy is a shop (fast fire growth from BS9999).

45 Exercise 5 Determine the fire size at the time the heat detector operates in the following situation? Operating temperature of the heat detector = 70C RTI of heat detector = 12 Spacing of heat detectors = 15m The height from the base of the fire to the ceiling of 11m. ambient temperature is 293K Occupancy - shop (fast fire growth from BS9999)

46 Exercise 6 A natural smoke control system is proposed for a large warehouse undergoing refurbishment with the following parameters. The sprinkler head is red with a fast response sprinkler head with a spacing of 4.5m The height from the base of the fire to the ceiling of 16m. ambient temperature is 293K The building is to store contents with a medium fire growth. a) Determine the fire size at sprinkler operation? b) If the building was used to store products with an ultra-fast fire growth rate, how would that affect the fire size on sprinkler operation? c) What would have been the impact of the sprinklers were standard response with an RTI of 120 for the ultra-fast fire growth?

47 Exercise 7 Determine the fire size at the time the sprinkler operates in the following situation? Fast response sprinkler is coloured red with a spacing of 8m The height from the base of the fire to the ceiling of 7.5m. ambient temperature is 293K Occupancy is a banking hall (slow fire growth from BS9999)

48 Exercise 8 Determine the fire size at the time the sprinkler operates in the following situation? Standard sprinkler (RTI = 90) is coloured green with a spacing of 6.5m The height from the base of the fire to the ceiling of 5.6m. ambient temperature is 293K Occupancy is a bingo hall (medium fire growth from BS9999)

49 Exercise 9 Determine the fire size at the time the sprinkler operates in the following situation? Standard sprinkler (RTI = 90) is coloured red with a spacing of 9.0m The height from the base of the fire to the ceiling of 17m. ambient temperature is 293K Occupancy is a storage building (ultra-fast fire growth from BS9999)

50 Exercise 10 A fire risk assessor identifies that a sprinkler system has been incorrectly fitted with standard response sprinklers with an RTI of 120, when it should have been fitted with fast response sprinklers, can you determine the impact on the fire size at time of sprinkler operation? The sprinkler head is yellow with a spacing of 6.0m The height from the base of the fire to the ceiling of 10m. ambient temperature is 293K Occupancy is a storage building (fast fire growth)

51 Module 36 At the end of this presentation you will have a good understanding of: Interaction between smoke vents and sprinklers Single opening in compartment Heat release rate required for flashover Single opening into compartment. When there is a single opening in the compartment you can determine the temperature increase of the gases using the following formula. T g 2 Q / 2 Ao h0 h k A T 1/3 T g = Increase in temperature of gas K Q = Heat release rate (kw) A o = Area of ventilation opening (m 2 ) h o = height of opening h k = Effective heat transfer coefficient (kw/m 2.K) A T = Total area of compartment enclosing surfaces(m 2 )

52 Firstly, determine if thermally thick using the following formula t p 2 wall 2 Cwall wall wall If the time is less than t p then use formula 1 if not use formula 2 Formula 1 h K K Cp t Formula 2 h k k wall wall Exercise 11 Calculate the upper layer temperature of a room 4.7m x 3.4m in floor area and 2.7m high. There is a door opening 2.0m high and 1.0m wide. The fire source is steady 1250Kw FIRE. The wall lining material is 0.02m ceramic fibre insulation board plaster (k wall = kW/m.K. c wall = kj/kg.k. p wall = 800 kg.m -3. Perform the calculations at time 20, 60 and 120 seconds after ignition.

53 Exercise 12 Calculate the upper layer temperature of a room 8.4m x 4.2m in floor area and 3.2m high. There is a door opening 2.1m high and 2.1m wide. The fire source is steady 750Kw FIRE. The wall lining material is 0.02m ceramic fibre insulation board plaster k wall = kW/m.k. c wall = kj/kg.k. p wall = 900 kg.m -3. Perform the calculations at time 30, 60 and 180 seconds after ignition.

54 Time to flashover Babrauskas Q FO 600 A H Hagglund Q FO A t At McCaffrey / /( A H O 1/ ) 3. Q FO 740 hk AT A0 H Thomas Q FO 7.8 A 378 A H T O 1/ 2

55 Exercise 13 Determine the heat release rate required to cause flashover for the following building with a single opening using the four models available?

56 Example 14 Determine the heat release rate required to cause flashover for the following building with a single opening using the four models available?

57 Example 15 Determine the heat release rate required to cause flashover for the following building with a single opening using the four models available?.

58 Sprinkler Calculations This module will look at the methodology for determine the pressure and flow requirements of sprinkler systems to BS EN To carry out the exercises you do need access to a copy of the standard. Module 37 At the end of this presentation you will have a good understanding of:. Overview Extent of sprinkler protection Hazard classification Area of operation Module 38 At the end of this presentation you will have a good understanding of: Exercises

59 Exercise 1 Determine the pressure and flow requirements of a sprinkler set used to protect an area which is classified as OH2 and they are using 32mm cast iron pipework. The sprinklers are spaced 3.0m apart. There is a 90 degree screwed elbow in the pipework system and a rise of 6.5m above the valve. The K value of the sprinkler is 115.

60 Exercise 2 a) Determine the pressure and flow requirements of a sprinkler set used to protect an area which is classified as LH and they are using 20mm steel pipework. The sprinklers are spaced 4.59m apart with each sprinkler covering 21m 2. There is a 45 degree screwed elbow in the pipework system and a rise of 3.4m above the valve. b) What would the flow and pressure required at the valve have be have been if you had used 25mm steel pipework

61 Exercise 3 a) Determine the pressure and flow requirements of a sprinkler set used to protect an area which is classified as high hazard for roof sprinklers. As the contents are mixed, choose the highest HH standard. They are using 40mm steel pipework. The sprinklers are spaced 3m apart with each sprinkler covering 9m 2. There is a 90 degree screwed elbow in the pipework system and a rise of 8.6m above the valve. The K value of the sprinkler is 115.