Download Thermal Comfort - Building Services and Fire Engineering - Past Exam and more Exams Safety and Fire Engineering in PDF only on Docsity! CORK INSTITUTE OF TECHNOLOGY INSTITIĆID TEICNEOLAĆOCHTA CHORCAĆ Autumn Examinations 2010 Module Title: Building Services and Fire Engineering for Structural Engineers Module Code: CIVL 8005 School: Building & Civil Engineering Programme Title: Bachelor of Engineering (Honours) in Structural Engineering ā Year 3 Programme Code: CSTRU_8_Y3 External Examiner(s): Dr. M. G. Richardson, Mr. J. OāMahony Internal Examiner(s): Mr. Fergus Delaney, Mr. Andrew MacIlwraith Instructions: Attempt 2 questions from Section A. Attempt 2 questions from Section B Use separate answer books for each section Duration: 2 Hours Sitting: Autumn 2010 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. Section A Building Services (Answer 2 question) Question QA1. QA1(a) Define thermal comfort (2 marks) QA1(b) Discuss deterministic methods and adaptive methods used to specify thermal comfort. (10 marks) QA1(c) Explain what is meant by PMV and PPD and discuss how they are used in specifying thermal comfort. (10 marks) QA1(d) The summer comfort criteria for a general office is given as operative temperature 21-23 o C, activity level 1.2 met, clothing level of 0.85 clo and 8 l/s per person ventilation rate. Assuming this spec results in a PMV of +/- 0.25 calculate the PPD from the equation 3.1 ļØ ļ©ļ ļ24 2179.003353.0exp95100 PMVPMVPPD ļ«ļļļ½ (5 marks) Question QA2. QA2(a) The building in fig. A2.1 is to be naturally ventilated. The building can be considered as a single cell and the ventilation process is to be driven by buoyancy effects only. The external air temperature is 22 o C and the internal air temperature is 26 o C. The volumetric flow rates and the discharge coefficients for the openings are given in table A2.1. Calculate the size of openings required to achieve the volumetric flow rates. Air density can be approximated by the equation ļ²T =1.2(273+20)/(273+T). (20 Marks) PART B: FIRE ENGINEERING ANSWER 2 QUESTIONS FROM THIS PART (50 MARKS) Question QB1. QB1(a) BS 476: 1972 defines a standard Time/Temperature curve which gives the furnace temperature for a test of specified duration. What durations would be common in a fire test? In what way does an actual fire temperature profile differ from the standard test curve? What is the approximate maximum temperature of an actual fire? How do these differences affect a designerās thinking when carrying out fire safety engineering design? . (12 marks) QB1(b) Describe the different classes of flammable liquid fuels giving examples of each class? Discuss limits of flammability, giving examples, and explain why certain flammable liquids are more dangerous than others. (6 marks) QB1(c) Flashover and backdraught are among the most dangerous effects of certain types of fires. Explain each phenomena giving possible scenarios where each could occur? ( 7 marks) Question QB2. QB2(a) A proposed medical facility intends using a walling system to provide an insulating barrier between the storage area and its adjoining clean room. Using the transient heat flow method, calculate the minimum thickness of walling, to the nearest mm, required to prevent the temperature on the clean room side of the wall rising 160 0 C above ambient for a 30 minute period of fire exposure. The fire within the storage area is at a steady temperature of 750 0 C. The initial ambient temperature in the clean room may be taken as 20 0 C. 5-minute time intervals may be taken as a suitable accuracy level. Thermal Diffusivity ( ļ” ) = ļ¬ ļ² . Cp Fourier Number = Ā½ = ļ” . ļt ļX 2 ļ¬ = Thermal Conductivity of Walling = 0.15 Wm -1 K -1 ļ² = Density of Walling = 700 kgm -3 Cp = Specific Heat Capacity of Walling = 850 Jkg -1 K -1 ļt = Time interval (s) ļX = Thickness of a notional layer within the walling (m) (16 marks) QB2(b) Describe the 4 different types of atria, and discuss the fire engineering advantages & disadvantages of each. (4 marks) QB2(c) Explain clearly the process of combustion of a Class A type material, and discuss the effect of the available surface area on the combustion process. (5 marks) Question QB3. QB3(a) Discuss in detail the physiological effects of smoke and heat on persons involved in a fire scenario. (8 marks) QB3(b) A new single storey office building, with plan dimensions of 40m by 20m, is to have a sprinkler system installed. The overhead sprinkler system is 5m above the control gauge, which are 500mm above the floor level. The sprinkler layout configuration is a side centre, with a side feed. As this building type is ordinary purpose group III, then the minimum design density can be taken as 5mm/min, and the assumed maximum area of operation taken as 216m 2 . Using 32mm diameter range pipes, and 100mm diameter distribution pipes & riser, design a suitable sprinkler head layout for this installation. Maximum area of coverage per sprinkler is 12m2, and the maximum spacing both along the range and between the range pipes is 4.0m. Calculate the water flow requirements of the system in litres/min. What pressure is required at the control gauge in order to ensure a minimum pressure of 1.5 Bar at each sprinkler head? (17 marks) Pressure Loss per metre length of 32 mm pipe = 57 mBar Pressure Loss per metre length of 100 mm pipe = 3 mBar Equivalent length of a 32 mm elbow = 1.04 m Equivalent length of a 32 mm T-piece = 2.13 m Equivalent length of a 100 mm elbow = 3.04 m Equivalent length of a 100 mm T-piece = 6.10 m Extracts from CIBSE Guide B
āTable 3.2 Recommended moxitnucn duct
velocities for medium und high pressure
Volume flow Velosity / mvs"!
induct Medi pressace High pressure
systems systerss
a 7
Ā» a
iH 18
8 20
3-2
Table 13 Gride wo moxiqnuen duet velocities in risers and ceifingetĀ®?
Duet location Duct ope Moxintaim air velocity ā msā!
for stased room type
āGiGHā āNormalā Noseeiieal
Riser orabove Rocungotar 3 3 io
plasterboard ceiling Citeular 7 n 1
Above suspended ceiling Rectangoler 3 5 6
Circular 5 7 18
x w Sy 5
x
7 | [600 mm
i i
500 rom }600 mm
If Wess than or equal to 1000 mon. X = 200 mm, $= 400 mm
IEW greater then 2000 mm: X = 400 mm, Ā§ = 600 rome
{a} insulated ducts
FV less than or equal to 100 mma: X = 100 mm, $= 300 mm
HEW grooter than 1000 men: X= 300mm, 5 = 400 mn
th} Uninsutated ducts
Figure A3.Z Space allowance for tectangular, ciroutar and flat oval
Suctwork (reproduced from MoD Desiga onal Maintenance Guide
8482; Ā© Ceown copyright mareral is reproduced with the permission
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