Building Services Engineering 5th Edition Handbook

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Ventilation and air conditioning 157 Consider the injection of tracer gas into a room such that its concentration is C r %. A stirring fan is used. Ventilation of the room is at the rate of N air changes per hour. The tracer gas concentration falls to C τ % during time interval τ. The room air change rate can be found as follows: N = 1 τ ln ( Cr C τ ) so that, ( ) Cr Nτ = ln C τ and hence, e Nτ = C r /C τ Thus the concentration C τ at time τ is given by: C τ = C r × e −Nτ EXAMPLE 5.10 Nitrous oxide tracer gas is admitted into a building and mixed with the internal air to achieve a 8% concentration. After 45 min, the tracer gas concentration has fallen to 1.5%. Calculate the air change rate per hour. N air changes h = 1 τ h × ln ( Cr C τ ) Now, τ = 45 min = 0.75 h C r = 8% and, C τ = 1.5% Hence, N = 1 ( ) 8 0.75 ln 1.5 = 1.33 ln 5.33 = 2.23 air changes/h
158 Ventilation and air conditioning Materials for ventilation ductwork The materials used for ventilation ductwork are listed in Table 5.3. Thin-gauge galvanized mild steel sheet ducts are the most popular because of their low cost. Prefabricated ducts and fittings allow rapid site erection. Circular, rectangular, flat or spirally wound circular ducts are generally used. Joints are pop-riveted and sealed with waterproof adhesive tape, hard-setting butyl bandage or heat-shrunk plastic sleeves. Large ducts have bolted angle-iron flanges, which also act as support brackets. Stiffening steel strips or tented sheets are used to reduce the drumming effect on flat duct sides caused by air turbulence. Bare metal is painted with metal oxide or zinc chromate paint. Ducts are thermally insulated with resin-bonded glass fibre boards or expanded polystyrene. An air pressure consisting of the design operational pressure plus 250 pascal (Pa) (1 Pa = N/m 2 ) is applied after installation for test purposes. The maximum allowed leakage rate is 1% of the system design air flow rate and leaks must not be audible. Chlorofluorocarbons Chlorofluorocarbons (CFC) are numbered to represent the chemical combination. Those in common use are listed in Table 5.4. When CFCs are released into the atmosphere as a result of leakage from refrigeration systems, the production of expanded foam, venting to the atmosphere during maintenance of refrigeration compressors, the use of aerosols, chemical cleaning or the destruction of refrigerators, they find their way to the upper atmosphere, where they are broken down by the action of ultraviolet solar radiation and chlorine is released. This degradation will continue for many years. Atmospheric ozone is destroyed by the chlorine, and it is reported that the resulting increase in the levels of ultraviolet radiation reaching the earth’s surface will cause ecological damage as well as an increase in skin cancer. Table 5.3 Ventilation ductwork materials. Material Application Jointing technique Galvanized mild steel sheet All ductwork Riveted slip joints, machine-formed snap-lock, flanged, butyl cement bandage, heat-shrunk sleeve UPVC and polypropylene Prefabricated systems for Flanged, socket and spigot housing and toilet extract Resin-bonded glass fibre Low-velocity and domestic Butt, sleeved, socket and spigot warm-air heating Asbestos cement Prefabricated circular and rectangular for flues and chemical exhausts Socket and spigot Flexible glass fibre, proofed fabric reinforced with galvanized spring wire helix Aluminium, copper, wired glass, stainless steel Brick, concrete, timber, fibre- or plasterboard Short connections from a duct to a terminal unit Kitchen extract hoods, ornamental use Recirculation airways within suspended ceilings and floors, surfaces sealed against dust release Jubilee clip, waterproof tape Flanges As appropriate
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Building Services Engineering
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Building Services Engineering Fifth
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Contents Preface to fifth edition A
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Contents vii Sick building syndrome
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Contents ix Circuit design 294 Cabl
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Preface to fifth edition Building S
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Acknowledgements I am particularly
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Units and constants xv Table 2 Mult
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Symbols xvii Symbol Description Uni
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Symbols xix Symbol Description Unit
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2 Built environment Introduction Th
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4 Built environment Ventilation The
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6 Built environment (a) At full occ
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8 Built environment Table 1.2 Compa
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10 Built environment Because of the
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12 Built environment Visual display
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14 Built environment v = 7 m/s t a
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16 Built environment 1.4 Sling psyc
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18 Built environment 1.7 Thermistor
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20 Built environment t res = t g (1
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22 Built environment great care wit
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24 Built environment 16. An hotel l
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26 Built environment 37. Are any of
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28 Built environment building has a
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30 Built environment 73. What was t
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32 Energy economics Introduction Bu
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34 Energy economics 16. air-to-air
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36 Energy economics 1 kWh = 1 kWh
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38 Energy economics 2. Heat transfe
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40 Energy economics For solid fuel
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42 Energy economics gas cost = 1.80
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44 Energy economics Table 2.5 Carbo
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46 Energy economics EXAMPLE 2.8 A h
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48 Energy economics annual cost = u
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50 Energy economics EXAMPLE 2.12 Ex
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52 Energy economics l = 0.035 ( 1 0
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54 Energy economics Table 2.11 Valu
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56 Energy economics From Table 2.4
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58 Energy economics 3. Minimum outs
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3 Heat loss calculations Learning o
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62 Heat loss calculations Table 3.1
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64 Heat loss calculations Table 3.6
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66 Heat loss calculations Where onl
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68 Heat loss calculations The venti
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70 Heat loss calculations The surro
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72 Heat loss calculations The speci
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74 Heat loss calculations where R m
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76 Heat loss calculations The addit
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78 Heat loss calculations operation
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80 Heat loss calculations 2. The fo
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82 Heat loss calculations internal
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84 Heat loss calculations 27. Which
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86 Heating Key terms and concepts a
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88 Heating 4.2 Electrically heated
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90 Heating Sheet steel case Removab
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92 Heating Floor finish Screed with
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94 Heating Flue Return air plenum F
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96 Heating Table 4.1 Classification
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98 Heating Table 4.2 Heat output fr
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100 Heating Table 4.3 Flow of water
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102 Heating and, maximum available
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104 Heating This means that one vol
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Page 133 and 134: 112 Heating 3. A building energy ma
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Page 145 and 146: 124 Heating 4. Heat supplied is cha
Page 147 and 148: 126 Ventilation and air conditionin
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Page 199 and 200: 6 Hot- and cold-water supplies Lear
Page 201 and 202: 180 Hot- and cold-water supplies Wa
Page 203 and 204: 182 Hot- and cold-water supplies po
Page 205 and 206: 184 Hot- and cold-water supplies Ce
Page 207 and 208: 186 Hot- and cold-water supplies st
Page 209 and 210: 188 Hot- and cold-water supplies 0.
Page 211 and 212: 190 Hot- and cold-water supplies 53
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Page 215 and 216: 194 Hot- and cold-water supplies Ta
Page 217 and 218: 196 Hot- and cold-water supplies Ta
Page 219 and 220: 198 Hot- and cold-water supplies (a
Page 225 and 226: 204 Hot- and cold-water supplies 49
Page 227 and 228: 206 Soil and waste systems Introduc
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208 Soil and waste systems Open to
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210 Soil and waste systems 7. Bends
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212 Soil and waste systems The inte
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214 Soil and waste systems 40 mm wa
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216 Soil and waste systems Table 7.
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218 Soil and waste systems 50 mm ve
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220 Soil and waste systems 3. Long
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222 Surface-water drainage Table 8.
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224 Surface-water drainage Rectangu
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226 Surface-water drainage The solu
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228 Surface-water drainage 7. A PVC
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230 Below-ground drainage Design ca
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232 Below-ground drainage Manhole:
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234 Below-ground drainage From Fig.
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236 Below-ground drainage storage v
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238 Below-ground drainage 14. The f
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240 Condensation in buildings mould
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242 Condensation in buildings The w
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244 Condensation in buildings EXAMP
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246 Condensation in buildings This
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248 Condensation in buildings Tempe
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250 Condensation in buildings and,
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252 Condensation in buildings EXAMP
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254 Condensation in buildings Tempe
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256 Condensation in buildings For t
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258 Condensation in buildings 4. Ev
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11 Lighting Learning objectives Stu
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262 Lighting Table 11.1 Typical val
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264 Lighting Light sources 9 9 9 Wi
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266 Lighting Utilization factor The
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268 Lighting From Table 11.3, for a
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270 Lighting Table 11.4 Lamp data.
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272 Lighting number of lamps = 12.8
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274 Lighting 3. Sketch and describe
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276 Lighting 4. Insufficient inform
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278 Lighting 3. 800 lm/m 2 . 4. 260
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12 Gas Learning objectives Study of
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282 Gas Open to atmosphere Rubber p
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284 Gas EL = (1.25 × 34) m = 42.5
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286 Gas become exhausted. SNG will
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288 Gas are ignited and an air flow
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290 Gas 3. The pipe from a gas mete
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292 Electrical installations Key te
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294 Electrical installations curren
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296 Electrical installations 1 Volt
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298 Electrical installations power
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300 Electrical installations For1mm
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302 Electrical installations Table
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304 Electrical installations Incomi
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306 Electrical installations energi
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308 Electrical installations Starte
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310 Electrical installations Ethyle
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312 Electrical installations Test o
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314 Electrical installations Joint
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316 Electrical installations 4. 100
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318 Electrical installations 39. Wh
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320 Electrical installations 51. Wh
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322 Room acoustics 20. understand t
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324 Room acoustics pump blades and
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326 Room acoustics ceiling, Q is 4.
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328 Room acoustics Table 14.2 Solut
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330 Room acoustics Table 14.3 Fan s
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332 Room acoustics Table 14.4 Illus
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334 Room acoustics (Sound Research
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336 Room acoustics The target room
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338 Room acoustics Table 14.6 Noise
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340 Room acoustics 100 90 80 70 Sou
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342 Room acoustics 24. A forced-dra
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344 Room acoustics The room directi
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346 Room acoustics 3. Multiple sour
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348 Room acoustics 55. Which is not
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350 Fire protection computer monito
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352 Fire protection halogen gas, wh
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354 Fire protection the reach of tu
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356 Fire protection Range pipe Spri
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358 Fire protection Fire compartmen
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360 Fire protection 16. Which are c
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362 Plant and service areas Key ter
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364 Plant and service areas 2.0 1.5
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366 Plant and service areas Fuel st
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368 Plant and service areas a minim
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370 Plant and service areas An unde
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372 Plant and service areas Air cha
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374 Plant and service areas 100 mm
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376 Plant and service areas Fire co
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378 Plant and service areas Table 1
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380 Plant and service areas 11. Wha
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17 Mechanical transportation Learni
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384 Mechanical transportation Table
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386 Mechanical transportation Crowd
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388 Mechanical transportation Hydra
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390 Mechanical transportation 4. Co
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18 Question bank Learning objective
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394 Question bank 8. Which correctl
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396 Question bank 5. This building
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398 Understanding units Questions 1
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400 Understanding units 15. Which i
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402 Understanding units 29. Which o
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404 Understanding units 43. Which i
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Appendix: answers to questions Chap
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408 Appendix Chapter 3 Heat loss ca
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410 Appendix 4. 0.007469 kg H 2 O/k
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412 Appendix 32. 5 33. 5 34. 3 35.
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414 Appendix 23. Lighting 1200 h/ye
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416 Appendix 27. 37 dB. 28. 39 dB.
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418 Appendix 15. 5 16. 2 17. 5 18.
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References Action Energy, Departmen
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Index Absorption 154, 324 Absorptio
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424 Index Gas burner controls 289 G
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426 Index Sensible heat gains 137 S
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