Design a ventilation system for the toilets in an Auditoria as shown in the accompanying drawings.. The Male Toilet and Female Toilet should each have separate extract ventilation system
Trang 1Design a ventilation system for the toilets in an Auditoria as shown in the accompanying drawings
The Male Toilet and Female Toilet should each have separate extract ventilation systems to avoid ‘cross-talk’ and spread of smoke within the ductwork system
The mechanical ventilation rate from Table 3.1 CIBSE Guide B2 (2001) is at least 3 air
changes per hour
For the purposes of this exercise use a value of 8 AC/h
Trang 2MALE TOILET
The volume of the Male Toilet is: 4.5 x 3.0 x 2.7 m = 36.45 m3
The ventilation rate in m3/h is:
Ventilation Rate (m3/h) = Room volume (m3) x air change rate (ac/h)
Ventilation Rate (m3/h ) = 36.45 m3 x 8 AC/h
= 291.6 m3/h Divide by 3600
The ventilation rate is = 0.081 m3/s
A simple method of duct sizing would be:
Duct area = volume flow rate / air velocity
An appropriate maximum air velocity for a toilet is 4 m/s
(See Ventilation - Ventilation Design section)
Therefore duct area = 0.081 / 4 = 0.02025 m2
If a square duct is used then the duct size is: ( 0.02025 )0.5
= 0.142 m x 0.142 m
The nearest standard size is 0.150 m x 0.150 m
or, 150mm x 150mm
The drawing below shows the ductwork layout for the Toilets
The flexible ductwork may be sized using the same technique as above
Trang 3Volume flow rate through each flexible = 0.081 m /s / 2 = 0.041 m/s.
A simple method of duct sizing would be: Duct area = volume flow rate / air velocity
An appropriate air velocity for a flexible in this situation is 4 m/s
Therefore duct area = 0.041 / 4 = 0.01025 m2
Cross sectional area = p d2 / 4 d = ( 4 CSA / p )0.5
Therefore flexible diameter = ( 4 x 0.01025 / p )0.5 = 0.114
m = 114 mm diameter
The nearest standard size of PVC flexible is 125mm
The flexible size should be smaller than the duct to which it is attached to enable a boot or branch to be spot welded into position, as shown below
The Female Toilet may be sized using the same method but since the physical dimensions are so close to the Male Toilet then the same duct sizes can be used, this also standardizes the complete ventilation system so that the two fans are also identical
Fans
To choose suitable fans for this example the duct pressure drop and fittings pressure drop would be calculated
If the total pressure drop is assumed to be 200 Pa and the flow rate is 0.081 m3/s (81 litres/s) then a suitable catalogue can be used to pick the fan
See http://www.flaktwoods.com Go to Other Fans section
A tube fan or boxed fan can be used for this project