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Vntilation 4 Natural Vntilation Vladimír Zmrhal (room no. 814) http://ur.f.cvut.cz/~zmrhavla/indx.

1 Vntilation 4 Natural Vntilation Vladimír Zmrhal (room no. 814) Útav tchniky protřd dí 1 Natural vntilation Th air flow i drivn by prur diffrnc acro th building nvlop. Prur diffrnc i caud by: air dnity diffrnc (tmpratur diffrnc btwn indoor and outdoor air) wind prur 2 1

2 Natural vntilation natural vntilation by larg opning (prmannt) haft vntilation (prmannt) hat ourc intruptd natural vntilation (tim limitd) infiltration (tim limitd) dpnd on outdoor climatic condition 3 Natural vntilation Balancd natural vntilation for vntilation in indutry with prmannt hat gain - natural vntilation by larg opning in ridntial infiltration and intrruptd vntilation Natural local xhaut haft vntilation 4 2

3 Natural vntilation Stack prur - hydrotatic prur caud by th ma of a column air locatd inid or outid a building Stack prur diffrnc ( ) p = hg ρ ρ 1 2 ( ρ ρ ) p = p p = g dy h 5 Natural vntilation Wind prur 2 w pw = Cp ρ 2 whr C p i wind urfac prur cofficint (mpirical); it dpnd on wind dirction, orintation of th building urfac, C p = -1,4 to 1,2 6 3

4 Natural vntilation by larg opning 7 Natural vntilation by larg opning Prur diffrnc (tack ffct) p = hg t i t = oz ( ρ ρ ) + t 2 x i Vrtical air tmpratur chang cofficint of hat rmoval fficincy B [-] Mcir B = M + M cir 8 4

5 Natural vntilation by larg opning Hat balanc ( ) M ct + Mct = M + M ct cir x cir oz toz t B = < 1 t t x B = 0,25 to 0,4 Summr: t oz t 5 K; t = 25 C Wintr: t oz,min = 10 C; t = 0 C in Czch Rp. 9 Natural vntilation by larg opning Hat cofficint B Indutry application Stl mill Rolling mill Foundry Gla factory baic furnac lctric furnac cat hall furnac rolling ction mlting-hou, cupola cat into ingot cooling ction tank furnac pot furnac B 0,30-0,35 0,35-0,40 0,25-0,30 0,25-0,30 0,25-0,45 0,40-0,45 0,37-0,40 0,65-0,70 0,26-0,30 0,26-0,

6 Natural vntilation by larg opning Ma air flow Q M = c t t ( ) x Opning ara M = M = M x µ A ρ w = µ A ρ w w = x x x x p µ ρ = p A 2 2 x x x 2 2 x µ ρ A 2 p ρ 11 Natural vntilation by larg opning Dicharg cofficint for opning µ µ = αϕ whr ϕ...vlocity cofficint [-] α cofficint of contraction [-] w ϕ = w α = A A t ral and thortical vlocity ratio ral and thortical ara ratio wa V µ = = w A V t t ral and thortical volum flow ratio 12 6

7 Natural vntilation by larg opning Dicharg cofficint for opning µ Opning H/B Shuttr angl α Supply air with louvr 1 0,5 0,15 0,13 0,3 0,27 0,44 0,39 0,56 0,56 0,64 0,61 Singl baffl cntrhingd 1 0,1 0,15 0,13 0,3 0,27 0,44 0,39 0,56 0,56 0,64 0,61 13 Natural vntilation by larg opning for prur diffrnc p, p x can b writtn p = p + p x Opning ara [m 2 ] A M Mx = Ax = µ 2 p ρ µ 2 p ρ x x x Location of th opning in ummr (by th floor) and wintr (mallr opning and highr location - up to 4 m). 14 7

8 Natural vntilation by larg opning Exampl 1: Calculat A =? and A x =? Intrnal hat gain Q = 50 kw Outdoor air tmpratur t = 25 C (ummr) Atmophric prur p b = 100 kpa h = 12 m B = 0,35 µ = 0,75; µ x = 0,65 A x / A = 1 / 3 p 273 ρ = 1,293 b t 15 Shaft vntilation prur diffrnc du to tack ffct p = hg ( ρ ρ ) i prur lo (friction and local lo) 2 l w plo = λ + ζ + 1 ρi d 2 p p V = lo Q ρc t ( t ) Not: valu 1 i 16 8

9 Shaft vntilation aumption: th prur in th haft i approximatly qual to atmophric prur p i = p ffct of th ara of th upply opning 17 Infiltration uncontrolld natural vntilation through th crack, gap around clod window and door, mortar joint air lakag through th building nvlop poitiv ffct of infiltration vntilation ngativ ffct of infiltration hat lo in wintr prnt - day tight window 18 9

10 Infiltration 19 Infiltration Airflow through th gap n ( ) V = i l p whr p prur diffrnc acro th lakag path [Pa] i flow cofficint [m 3 /(.m.pa 0,67 )] l lnght of th gap [m] n flow xponnt n = 0,67 Vntilation hat lo ( ) Q = V ρc t t vnt i 20 10

11 Infiltration Exampl: Room 10 m 2, hight 2,6 m, window 1,2 x 1,5 m, t = -12 C, t i = 20 C Old window Rquirmnt Common window Top window i [m 3 /(m..pa 0,67 )] 0, ,00001 to 0, , , I [h -1 ] 0,80 0,02 to 0,36 0,10 0,02 Q vnt [W] to Infiltration Air prmability (ČSN EN 12207) Q 2 / 3 p = Q [m 3 /h.m] Q 100 p rfrntial air prmability 100 Pa [m 3 /h.m] tt prur [Pa] i Q = / 3 [m 3 /.m.pa 0,67 ] 22 11

12 Infiltration Cla Rfrntial air prmability Q 100 [m 3 /h m] 12,50 6,75 2,25 0,75 Max. tt prur [Pa] Air prmability Q for 1 Pa [m 3 /h m] - 0,580 0,313 0,104 0,035 Flow cofficint Q for 1 Pa [m 3 / m] = i [m 3 / m Pa 0,67 ] 1, , , , Intruptd natural vntilation caual opning of th window lowr and highr part of th window ma balanc M = M = M M x = µρ w S 24 12

13 Intruptd natural vntilation 2 px dm = µρ bdx = µ 2gx ( ρ ρi ) ρ bdx ρ 25 Intruptd natural vntilation h / 2 1/ 2 2 h M = µ b 2g ( ρ ρi ) ρ x dx = µ b 2g ( ρ ρi ) ρ h = µ b 2 g ( ρ ρi ) ρ M = µ b g ( ρ ρi ) ρh /

14 Thank you for your attntion 27 14

Calculation of electromotive force induced by the slot harmonics and parameters of the linear generator

Calculation of electromotive force induced by the slot harmonics and parameters of the linear generator Calculation of lctromotiv forc inducd by th lot harmonic and paramtr of th linar gnrator (*)Hui-juan IU (**)Yi-huang ZHANG (*)School of Elctrical Enginring, Bijing Jiaotong Univrity, Bijing,China 8++58483,