Car park ventilation system –
Alternative option
O. Common terms Date:
03.10.2024
1. IAQ – Indoor Air Quality
2. ACH – Air change per hour
3. Air flow rate – cu.m/hr
A. Jet fans – design notes
1. Jet fan area coverage and spacing = 400 sq.m
2. Jet fan spacing – longitudinal 2/3 of effective throw = approx. 20-30 meter.
3. Lateral spacing = usually 10-15m
4. Primary jet termination velocity = 0.5m/s
5. Floor to ceiling height effect (More height = less throw)
Control sequencing
1. Jet fans can be operated on a demand-based sequence
For e.g. based on Co levels 0 ppm no jet fans, CO>15ppm, 15<CO<35
ppm selected jet fans, CO>35ppm all jet fans, CO>100ppm all jet fans
at high speed.
2. Jet fans can operate on time delays.
B. Basement car park area approx. = 10974 sq.mt
C. Design air flow for car park exhaust = for 10 Ach = 28000 l/s
D. No of jet fans required will be approx. 28 nos (actual shall be as per CFD)
E. Free area required at ramp for exhaust air discharge will be 6 sq.m (4m x
1.5 m) with 4 nos exhaust fans discharging outside the ramp.
F. Basment-1 clear height: Floor to slab = 3.1 to 3.5m plus attic slab.
G. Option 1: The IAQ scheme: Design principal Fire and Smoke purging mode.
1. CAR PARK EXHAUST AIR PLENUM
Vent 9
sq.m Cancelle
d
Basement-1 Smoke Ground floor architecture Model Exhaust air
layout plan Plenum box
2. TRANSFORMER ROOM
Vent 4
sq.m
Cancelle
d
Basement-1 Ventilation Ground floor architecture Model Plenum box
layout plan
3. GENERATOR ROOM
Vent 5 Vent 10
sq.m sq.m
Cancelle
d
Basement-1 Ventilation Ground floor Model Plenum box
layout architecture plan
4. LV ROOM
Not Required
Basement-1 AC layout Ground floor architecture Model Plenum box
plan
H. Operating sequence:
1. Fresh and Exhaust air ventilation will be carried out in basement-1 high
level for
a. Transformer room
b. Generator room: It is emergency operation and will be operational only
in specific conditions, also as per current revised design generator is
already exhausting air into basement-1 due to revised air flow rate
requirements as per generator load.
c. Car park jet fans will be deployed to push the air to ramp exit exhaust
fans.
d. Car park jet fans and Exhaust/Make fans operating control sequencing
to be set to allow for fresh air input into basement-1 and push exhaust
air out of Basement-1 in carefully controlled format to ensure IAQ is
maintained in basement-1 car park,
e.g.:
i. For maintaining IAQ due to exhaust from Transformer room – Only
exhaust and Make fan operating to maintain 3 ACH in the car park.
ii. For maintaining CO levels due to car exhaust – A set of jet fans and
exhaust and make up fan operates to maintain 6 ACH in the car park.
iii. For fire mode condition all jet fans, exhaust and make fan operates
to control fire conditions.
I. Constraints:
a. FLS consultant need to be contacted for local regulation compliance in
using car park fans for maintaining IAQ.
b. CFD simulation by specialist to be carried out to analyze the air flow
patterns and jet fans position w.r.t to flow obstruction and floor to
ceiling height.
c. Open area of ramp to be located for free exhaust air discharge to
environment.
d. Cost offsetting for car park fire rated exhaust duct and jet fans with
control panel
J. Option 2: The AsR scheme:
In this scheme since the plenum box is empty and only used for air containment
the aspect ratio which means HXWXL can be altered substantially by reducing
the height of the box to allow for clear view of office space by increasing the
cross-sectional areas as height compensation.
This will allow a flat slab at low height to be constructed continuously and
utilized as air discharge pockets using cage or bar grilles at side slab and
pushing the duct air plenum inside the basement-1 room.
Continuous flat slab can be used as walkway or access etc.
Below the slab will be air discharge and intake outlet serving ventilation for
service rooms and car park exhaust as shown – clear diagrams will need to be
modelled in BIM.
Additional information:
1. Exhaust fans hanging at ramp discharge:
2. Jet fans models
i. Axial flow fan with deflectors -
ii. Induced jet air fan model
iii. Jet fan Working principle
iv. CFD analysis.
