Seong Hwan Yi is an ASHRAE member and CEO of Ventilation Institute of Korea Ltd.

Intelligent smokes extract and ventilation system for an underground parking lots

Seong Hwan Yi, PhD

[ASHRAE Member]

ABSTRACT HEADING

Underground parking lot emits CO, Black Carbon and the other gases in normal operation and before a certain time limit is able to empty the car park

from smoke after a fire is extinguished, with its known risks. In order to exreact smokes within a certain time limit, the ventilation system of

underground parking lots can be designed by duct or jet fantypically. Regardless of which system design is chosen, the mechanical rooms should be

considered in planning the system. To meet smokes management code requirements, for instance 12ACH, due to big fans, initial construction costs for the

mechanical room and energy consumption will be increased in the system on the aforementioned accordingly. On the other hand, the THRUVENT

system can meet the code requirements without fan rooms. Furthermore, the air is supplied to the premises and or a shaft at high thrust by

THRUVENT fan array assembled by jet fans in the required direction. The fan array provides the high thrust with impulse that causes the

surrounding air to be carried onwards with low noise and low energy consumption even under the circumstances of smoke extraction.

On the top of this, Ventomatic is an intelligent smoke extract and ventilation control solution for the underground parking lots. It measures air quality

using sensor terminal in real time, and measured data is collected on the control server by through wireless communication. Then the control server

aiutomatically detrermines the parking lots air pollution and operates it supply fan, exgaust fan and jet fans depending on the current levels of air

pollution, in order to maintain optimal air quality and or a certain time limit is able to empty the car park from smoke after a fire is extinguished at the

underground parking lots.

INTRODUCTION

Underground parking lots can be either fully enclosed or partially open. Fully enclosed parking areas are usually

require mechanical ventilation. Since 1996, the Jet fan system is being introduced to the market in Korea instead of

duct system. However, this Jet Fan system still needs a space for an installation of either supply or an exhaust fan

room. Also, these big fans are usually very noisy, in addition to high initial costs and high electric energy consumption.

In order to reduce the initial construction costs and save energy, this study proposes a new concept of the named as

THRUVENT for underground parking lot’s ventilation system.

Jet Fan system is composed of supply fan, Jet fan and exhaust fan as shown in Fig. 1(a) of an underground parking lot.

However, space is required to house the supply and exhaust fans. This would elevate the initial construction costs

because a mechanical room is required. Even so, the space could not be used efficiently in the mechanical room.

Because of voluminous fan, heavy duty power consumption for a fan operation, maintenance and repair expenses are

high and indoor sound condition is usually poor as well.

THRUVENT is a system using only shafts for air supply and exhaust and, therefore, no fan rooms are required as

shown in Fig. 1 (b). The air is supplied to the premises or a shaft at high speed by jet fan array in the required

direction. The jet fan array provides the supply air with the impulse that induces surrounding air onwards. And,

polluted air insides is diluted and discharged through exhaust shaft the same way as the Jet Fan system. Due to

installation of a series of small Jet fans without fan rooms, space and energy saving, installation flexibility, and a fair

initial construction cost reduction and low noise are realized. To summarize, THRVUENT system is composed of the

jet fan arrays for supply and exhaust and a single Jet fans as shown in Fig.1 and 2.

Figure 1 (a) Jet fan system and (b) Thruvent system.

Figure 2 (a) Jet fan array for supply and (b) Jet fan for exhaust.

REQUIREMENTS VENTILATION RATE FOR DIFFERENT TYPES OF FACILITY

During 1990’s in Korea, CO concentration for a design criterion was 10ppm. Based on 10ppm calculation, in case of

an apartment, the maximum air flow rate was 9.7㎥/hr㎡. But, due to vehicle emissions have been reduced over the

years, the maximum outdoor CO concentration has also been reduced down to 3ppm as per the data given by Central

Meteorological Office measured from 1992 to 1999. Thus, the maximum ventilation rate also be shifted to 7㎥/hr㎡

accordingly. Table 2 shows the maximum ventilation rate per square meter in each types of facility. Mainly four factor

as well as the heaped data gathered through more than 10 years were considered as below:

1. Acceptable CO limit is 25 ppm.

2. Number of cars in operation during peak condtion

3. Length of travel and the operatingtime for cars in the garage

4. Emission rate of a typical car under various conditions).

Table 1. Threshold CO Limit for an Underground Parking lot

Country Limit Country Limit

U.S.A 35 ppm Germany 25 ppm Japan 35 ppm Korea 25 ppm (for an 8 hr exposure)

Table 2. Maximum Ventilation Rates for Different Types of Facility

Type of facility

Frequency Number of in and out

cars/hr

Emission rate of CO

(g/hr)

Exhaust rate

(㎥/hr) Coefficient

Maximum exhaust rate

per ㎡ (㎥/hr)

Calculation Application

Apartment 2.1 33 1,391.5 31,165 1.2 7.0 7.0

Complex 4.43 71 2,981.6 66,777 2.14 15.0 15.0

Hospital 6.4 99 4,153.5 93,024 2.99 21.0 21.0

Public 7.1 110 4,613.54 103,327 3.32 23.2 23.0

Office 3.6 56 2,353.94 52,720 1.69 11.8 12.0

Accomodation 5.5 85 3,567.4 79,897 2.56 17.9 18.0

Commercial 5.9 92 3,860.34 86,458 2.77 19.4 20.0

Theater 4.2 65 2,730.5 61,154 1.96 13.7 14.0

Wedding shop 3.1 48 2,019.2 45,223 1.45 10.2 10.0

Culture 3.8 59 2,479.5 55,532 1.78 12.5 13.0

Terminal 7.3 113 4,739.1 106,139 3.41 23.9 24.0

PRINCIPAL POINTS OF THRUVENT SYSTEM

From a jet fan blow air with a relatively high velocity. From this jet fan array, air flows continuously with a velocity of,

for example 12-13m/s and this primary air stream will produce a secondary air stream in the area. The exact air

velocity and the total air volume of jet fan array used to the thrust calculation for intelligent smokes extract CFD

analysis, which must be made for each car park.

CHARCTERSTICS OF A JET FAN AND FAN ARRAY

Computational Fluid Dynamics (CFD) program (NFX, Midas IT, Korea) used to analyze the characteristics of a jet

fan as well as a jet fan array. Input data and boundary condition, as used by CFD, are given in Tables 3 and 4.

Table 3. Input Data by CFD

Variable Input data

Domain X=530 Y=-285 Z=285, X=530 Y=285 Z=285

X=530 Y=-285 Z=-285, X=530 Y=285 Z=-285 Menu VR mode Grid 570×570×180

Main Fluid Air Solution variables Pressure, Temperature

Relax control Pressure : P1=0, Temperature : T=25 Turbulent intensity Kinetic Energy=0.01m²/sec², Distance=0.01m

Model k-ε Model

Table 4. Boundary Conditions

Boundary Input Data (Free Jet) Input Data (Confined Jet)

Velocity of 1st jet Diameter φ 360 (mm),

Velocity ul=0, vl=11.08m/s, wl=0 Diameter φ 360 (mm),

Velocity ul=0, vl=11.08m/s, wl=0

Inducing condition at damper None

Dimension

570(mm)ⅹ570(mm)ⅹ180(mm) Velocity ul=0, vl=5.17m/s, wl=0

Characterstics of jet fan.

Figs. 3(a) and 3(b) show air jet profiles at a jet fan in free and 300mm apart from jet fan in confined space respectively.

Compared to free jet under the same conditions, confined jet induced air flow is 5,500㎥/h.

Figure 3 (a) Free jet (b) Confined jet and (c) Simulation object.

Characterstics of various fan arrays.

Table 5 gives an idea of fan array in practice, and it can be assembled up to CN-8000 (440,000㎥/h).

Table 5. Boundary Conditions

Type CN 400 CN 600 CN 900 CN 1200

Supply air

Flow

Minimum Required

area

The impulse, which is the performance of the fan array, will be express in Newton. So a fan array delivers a certain

amount of Newton. The nominal thrust of a fan array is calculated by multiplying the volume with density and the fan

outlet velocity as below.

(1) where:

Fan arrays used in car park have the following thrusts, for an example, as shown in Table 6. In order to adjust and

maintain for a certain thrust generated by each fan array, VENTOMATIC is recommended. Depending on the status

of indoor air quality and or a fire, thrust will be varied by VENTOMATIC.

Table 6. Boundary Conditions

Fan Array Qv [㎥/s] Ρ[1.kg/㎥] Ν[m/s] Thrust[N]

CN400 6.11 1.2 8 58 CN600 9.17 1.2 7.7 84 CN900 13.75 1.2 7 110 CN1200 18.33 1.2 6.7 131 CN8000 122.22 1.2 3 440

To analyze thrust of CN1200 fan array, for an instance, a building that is 70m (length) ×40m (width) ×3.0m (height)

as Table 7 is selected.

Table 7. Air Thrust Profile at each Floor by CN 1200

Axis CN 400

Z axis (radius of jet)

qv = Volume of jet fan [m³/s]

ρ = Air density, [1.2Kg/m³]

ν = Outlet velocity of jet fan [m/s]

MODEL CN1200S FORM

REQUIREMENTS FOR SMOKE CLEARANCE.

The building regulations for most countries require that the ventilation systems are able to make smoke clearance.

Often this requirement is 12 air changes per hour. But the amount of make air is dependent on the smoke zone

barrier maximum allowable leakage ratios, whether or not the areas are protected by an automatic sprinkler system,

the differential pressures permitted by the AHJ, and maintaining the required door opening or closing forces below

code allowed maximums. The engineering of the smoke management systems should use this guideline: Handbook of

Smoke Control Engineering. "Published in cooperation with ICC, NFPA, and SFPE, the Handbook of Smoke Control

Engineering provides authoritative, comprehensive guidance on the latest in smoke control practice, incorporating the latest research and

current engineering approaches."

Result of a Value Engineering of Thruvent System.

Table 8. Calculations of the Initial Cosys and Energy Costs

Project Name Area Car Parking Lots

“P” project, Yeouido, Seoul, Korea 106,712㎡ 2,498 spaces

Overview

Table 9. Overview of Existing and Thruvent System

Description Existing System Thruvent System

Supply fan

Exhaust fan

Remarks

Type Install one large diameter axial fan, supply by MVD Problems: 1. High Power consumption : 2,300kW 2. High Noise : more 89dB(A) 3. Added installation : Large silencer and noise

chamber 4. Added installation : Fire damper, Back Draft damper

Type Small Axial fan Array / Mounted in shaft

(Walltype) Install turbo jet fan for airflow induction. Advantages: 1. Low Power consumption : 559.8kW , reduced

75.66% 2. Low Noise : 65dB(A)/unit , 78dB(A)/set 3. With Integral Damper : FD+BDD 4. Static pressure : 25mmAq

Table 10. Overview of Existing and Thruvent System

Description Thruvent System Thruvent System

Initial costs

1. Supply fan A. Quantity : 34sets (525units) B. Cost : $1,069,500

2. Exhaust fan A. Quantity : 38sets (525units) B. Cost : $1,040,300

3. Turbo Jet fan A. Quantity : 431units B. Cost : $319,300

SUB TOTAL ＄2,429,100

Reasons why value engineering

1. High initial costs and construction difficulties

2. High energy consumption

3. Noise pollutions generated by big axial fans

Not easy to maintain

Energy costs Per year

559.80kWᆞ$0.099/kWhᆞ 8rsᆞ 360Days

= $159,610 (24.34%)

2,300kWᆞ$0.099/kWhᆞ 8hrsᆞ 360Days

= $655,776 (100%)

By this comparison, when floor area total is 100,000 m² or more, the THRUVENT system cuts 75% of energy cost

against the existing system. And the additional benefits of energy savings are as follows.

Table 11. Energy Savings

Description Total Amount Remarks

Energy savings / 8 hours operation per day

$496,166 $655,776 – 159,610

Additional benefits / Interest on energy savings

$17,365.81 $496,166 ⅹ3.5%/year

Table 12 shows a comparison of the required area for the mechanical rooms. The THRUVENT system requires only

38% of space required for the ductless system. So, THRUVENT system can save extra space. Table 12 shows that

55.85㎡ or 5 car spaces is saved as a consequence.

Table 12. Required Total Area of Thruvent and Jet Fan Syatem (Area: 9,000 ㎡)

THRUVENT System JET FAN System

Requirement Area

for shaft

Supply 3.8m × 1.5m = 5.7㎡

Exhaust 3.8m × 1.5m = 5.7㎡

Supply 5.0m × 1.0m = 5.0㎡

Exhaust 5.0m × 1.0m = 5.0㎡

Installation area of fans

Supply －

Exhaust 3.8m × 1.5m = 5.7㎡

Supply 5.0m × 3.5m = 17.5㎡

Exhaust 5.0m × 3.5m = 17.5㎡

Total requirement

area

17.1㎡/place × 2places

= 34.2㎡ (38%)

45.0㎡/place × 2places

= 90.0㎡ (100%)

Increased parking area: 90.0㎡ － 34.2㎡ = 55.8㎡

Increased parking capacity : 55.8㎡ ÷ (5m×2.3m)/1car ≈ 5 cars

THRUVENT system and existing ductless system is compared briefly in the following conditions as initial and energy

cost per year. For comparison, the underground parking lot space is limited to 9,000㎡ (Table 12).

By this comparison, when total floor area is 9,000㎡ or more, the THRUVENT system cuts 20% of energy cost and

37.1% of initial cost against the existing ductless system. Table 11 shows a comparison of required area for the

mechanical rooms. The THRUVENT system requires only 38% of space required for ductless system. So,

THRUVNT system can save extra space. Table 7 shows that 55.8㎡ or 5 car spaces is saved as consequence.

CONCLUSION

As previously examined, This THRUVENT system give the solution for many practical problems that are caused by

existing ventilation and or Jet fan system for car parks. The most important advantages can be summarized as follows:

1. Space saving

Space saving is realized because the function of fan rooms will be taken over by fan arrays installed in a shaft and or

insides of car park. The fan array efficiency supply, spread and exhaust the air all over the car park floor from the air

supply to the air exhaust. No fan rooms are necessary, which gives 3% additional car parking space, saving.

Table 13. Space saving

Project Name ACH Air volume

(CMH) Additional Car Parking Lots

Country

Bajaj Emerald 12 520.000 9 India Commercial B/D 12 773.500 40 India India-Bulls Center 12 247.000 3 India

NCP Wadala 12 7.488.000 556 India The Park 12 5.687.500 58 India

Star Residence 12 2.101.000 6 Malaysia

YLY(鄭州) 10 1.298.000 18 China

Samsung SDS Data Center

8 291.500 16 Korea

POSCO Center BD 8 852.500 43 Korea Ga-Rak Apartment 6 1.699.500 370 Korea Ha-Nam Star Field 10 6.330.500 85 Korea

2. Installation flexibility

Various tests have shown that position of the fan arrays is very flexible. The positions of the fan arrays vary depends

on a structure given by site conditions without influencing the function of system as shown in Fig. 4.

Figure 4 (a) and (b) vary fan array “supply”

3. Perfect smokes evacuation

By only using a ducted supply and or an exhaust fan installed in a mechanical room there will be not enough thrust of

air at all. But by using fan arrays the excess heat and smokes on the car park floor will be completely extract in the

path of the parking floor by thrust comes from fan array, as shown in Fig. 5, as a result of which the smokes will be

much fast extracted in comparison with a Traditional Jet Fan system.

Figure 5 Thrust by fan arrays.

4. Better indoor air quality all over the car park

To maintain a better indoor air quality, from 0% up to 100% will often be operated depending on the level of

concentrated pollution or a customer demands. With the fan array and jet fan it is possible to supply fresh air with an

air movement in every part of the car park and maintain better indoor air quality. No “dead spots” will rise.

5. Possibility of energy saving

Considering that in a Traditional Jet Fan system the air velocity through the ducts connected with a big fan is higher,

the resistance including absorbed power will also be high. With the fan array system as THRUVENT the shafts itself

will be used as an air duct, the air velocity is low and the required power is not less than 40% lower than Traditional

Jet Fan system as well.

Table 14. Energy Saving

Project Name Power Consumption (kW)

Saving (kW) % Country Existing Thruvent

Bajaj Emerald 202,30 104,20 98,1 48,5 India

Commercial B/D 270,000 130,90 139,1 51,5 India

India-Bulls Centre None 23,90, - India

NCP Wadala None 2.371,20 - India

The Park 3.102,50 1.049,30 2.053,2 66,2 India

Maga Pars 1.716,25 386,10 1.330,2 77,5 Iran

Star Residence 1.282,40 280,90 1.001,5 78,1 Malaysia

YLY 930,00 222,90 707,1 76,0 China

Samsung SDS Data Centre 80,80 43,46 37,3 46,2 Korea

POSCO Centre BD 370,00 98,40 271,6 73,4 Korea

Ga-Rak Apartment 631,60 253,38 378,2 59,9 Korea

Ha-Nam Star Field 1.770,00 943,82 826,2 46,7 Korea

Parc. 1 2.300,00 430,50 1.869,5 81,3 Korea

6. Cost reduction

If fan rooms are not used, a fair not less than 20% of an initial cost reduction will be realized. The second cost

reduction factor is that the fan arrays can be selected at lower static pressure because the resistance of the air duct

system does not exist. This results in a fan array with a lower speed, which gives a sound reduction. We have realize

that the system with fan array needs more cabling and a larger control panel. But in spite of these extra costs the

saving aspects are in many cases, certainly in larger car parks, very realistic.

7. Easy commissioning

There are no adjustable dampers needed to get the right supply and or an exhaust fan air volume in a fan array. Each

jet fans composed of fan array has an unique back drafted fire damper which activates close and open by gravity force

provides by jet fan in a supply direction which is better than motorized fire damper equipped in Traditional Jet Fan

system as shown in Fig. 6.

Figure 5 Motorized Fire Damper

Variation with regard to the volume and required thrust is realized by switching fans on/off or using intelligent

control.

8. Smoke control possibilities

Theoretically it is possible to control smoke in a car park by fan arrays and jet fans. At this very movement the most

practical tests carried out in car parks are performed with cold smoke and in these tests the theory is working well. In

2006 VIKOREA developed and executed the first full scale fire test. Since then we developed different kind of smoke

tests. One fact is certain: it is impossible to control the smoke with old conventional ducted system.

This study also presented maximum exhaust rate (㎥/h・㎡) to maintain acceptable CO level of 25ppm. And quoting

this data can help to save more energy when we are taking an intelligent operation and or by a step control.

Additionally, this paper provides a maximum exhaust rate (㎥/h) per square meter depending on the types of facility

based on calculations by design over 10 years through various types of building using correlation equation and

experiences for a consideration on intelligent smokes evacuation and ventilation in normal.

NOMENCLATURE

Fnominal = Nominal thrust

qv = Volume of jet fan [㎥/s]

ρ = Air density, [1.2kg/㎥]

ν = Outlet velocity of jet fan [m/s]

REFERENCES

Yi, S.H. 1990. A case study on the the ventilaton system of underground car parking structure. Korean Journal of Air Conditioning and Refrigeration Engineering Vol. 19, No. 2, pp. 99-113.

Yi, S.H. 1998. Ductless ventilation system for an underground car parking lots. Korean Journal of Air Conditioning and Refrigeration Engineering Vol. 27, No. 3, pp. 273-283.

Yi, S.H. 2001. Fanroomless ventilation syatem for an underground car parking lots. SAREK 2001 Summer Annual Conference Vol. 2, pp. 719-724.

Yi, S.H. 2005. Fanroomless ventilation system for an underground parking lots. Indoor Air 2005 pp. 3265-3270. Yi, S.H. 2014. IT combined ventilation system for an underground car parking lots. Korean Institute of Architectural Sustainable

Environment and Building Systems Vol. 8, No. 1, pp. 42-50. Yi, S.H. 2017. Smoke evacuation and ventilation syatem for an underground parking lots. Korean Journal of Air Conditioning

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