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Types of Ventilation

The acceptable air quality has to be maintained by supplying adequate air of specified quality and quantity in the space. The ventilation of the building can be done by natural ventilation by means of windows and skylights or by mechanical ventilation.

Natural ventilation is the ventilation of a building without the aid of fans or other mechanical systems. Historically all buildings were ventilated naturally with the help of windows and skylights. Natural ventilation use the pressure difference or temperature difference to allow the flow of air through the building. Natural ventilation is not very effective as humidity control is not proper, but when used in conjunction with mechanical systems they can save electricity.

Mechanical ventilation is also called forced or induced ventilation and is done by fans and other mechanical means. This means of ventilation is very effective in controlling the humidity and air quality inside an air conditioned space. As it is a positive means of ventilation it can control the odors, contaminants and humidity as well. There are many examples of mechanical ventilation like our kitchens and bathrooms that have exhaust fans.

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Naturally Ventilated Building and Ducts for Mechanical Ventilation

Natural Ventilation

Mechanical Ventilation

Mechanical Ventilation

Mechanical ventilation is a method of forced or induced ventilation by using mechanical air handling systems, commonly called HVAC systems. Mechanical ventilation is more controllable than natural ventilation.

In Mechanical Ventilation blowers, fans, filters, and ducts are used for transporting and removing air from a space. There are two types of fans used for the transmission of air. When the air enters the impellers axially and is discharged radially from the impeller, it is called a centrifugal or radial flow fan. When the air flows parallel to the axis of impeller, it is called an axial flow fan.

Centrifugal Fan: Centrifugal fans are very popular in the duct air conditioning system. The centrifugal fan has an impeller mounted in a volute casing. The fan impeller of the centrifugal fan can have the following profiles:

Radial or straight blades: It is a simple impeller construction. The blades run straight from a central point. These fans provide very high pressure at high speeds of rotation.

Forward Curved Blades: These blades are shallow in depth. These fans are efficient and have less noise.

Backward curved blades: They have to be operated at higher speeds for same pressure. Due to their higher speeds they can be directly coupled to the motors.

Axial Flow Fan: These fans are never used in duct air conditioning system as they cannot develop high pressures, however they can handle large quantities of air. The axial flow fans are of the following types:

Propeller Fan: A propeller fan consist of a propeller in a mounting ring. They are used when the resistance to air movement is small as in the ventilation of bathrooms, and attic spaces.

Tube Axial Fan: It consists of a propeller fan housed in a simple cylinder. These types of fans can be installed in round ducts. The air flow in the tube is spiral on its way out.

Vane Axial Fan: A vane axial fan has a tube axial fan along with guide vanes to stop the spiral movement of air.

Images

Centrifugal Fan

Air Changes Required

ASHRAE standard 62 states that certain amount of fresh air should always be supplied to all the areas of the building or the air conditioned spaces, which is dependent on the activity being done and the number of people present. For example dancing floors and smoking areas will require more air changes than other areas.

The air changes required by various spaces are as follows:

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1) https://new-learn.info/packages/clear/thermal/buildings/active_systems/mv/index.html
2)https://www.youtube.com/watch?v=d9btBXMocsc&t=3s
Advantages of Mechanical Ventilation
~ Good control of the ventilation capasity
( No dependence from the outdoor weather conditions & despite possible noisy environment)
~ Possibility of extracting heat from the exhaust air & to
preheat the fresh air supply (heat recovery)
~ Possibility of preheating and pre-cooling of the air supply
~ Possibility of humidify and dehumidify of the air supply
~ Possibility of cleaning air by an air filter or supplying the air from a relative clean site of the building

Comparison between natural and mechanical ventilation
- natural use environmental condition but mechanical use required in the building
- example natural is direction, speed and wind pressure but example of mechanical is getting enough air quantity and good quality
- natural can control but mechanical can control
- if we use natural we have to provide many opening to air can cooling the building but mechanical not have to get many openning
- the mechanical can organize and control the environment but natural just depend the have the openning
- natural provide the air flow in - out but mechanical can remove direcly the heat and all impurities in the air
-https://youtu.be/d9btBXMocsc

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domestic building overseas

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Best way to cool down your home - fresh air - Whole House Fan - heating and cooling exhaust fan

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MECHANICAL INLET AND NATURAL EXTRACT

1) What is mechanical inlet ?
- Fans, air conditioning, air filter
- Building by using mechanical inlet and the air exit itself by using natural openings provided.

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MECHANICAL / FORCED VENTILATION

A building ventilation system that uses powered fans or blowers to provide fresh air to rooms when the natural forces of air pressure and gravity are not enough to circulate air through a building. Mechanical ventilation is used to control indoor air quality, excess humidity, odours, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates specialised ventilation systems can remove excess moisture from the air.

Ceiling fans are commonly seen as ventilation systems as they are usually the most visible mechanical system in a building; however ceiling fans do not provide real ventilation, as there is no introduction of fresh air. Ceiling fans only circulate air within a room for the purpose of reducing the perceived temperature by method of evaporation of perspiration on the skin of the occupants. Also hot air rises therefore; ceiling fans may be used to keep a room warmer in the winter by circulating the warm from the ceiling to the floor.

Picture

Rotary Heat Exchanger

Picture

Ceiling Fan

MAIN METHODS OF FORCED VENTILATION:

PRESSURE SYSTEM: a system which air is blown through the building by a fan or other blower placed at the inlet. The air pressure in the building is slightly greater than that of the outer atmosphere.

Picture

Pressure System

VACUUM SYSTEM: causing an inrush of fresh air. This is done by an exhaust fan placed at the outlet to the vent flue or stack. The air pressure in the building is slightly lower than that of the outer atmosphere.

However a combination of these two methods can be used to create a BALANCED SYSTEM:

Picture

A Balanced Ventilation System

BENEFITS OF BALANCED SYSTEM:

Improved indoor air quality. Balanced ventilation systems supply fresh air to the living and sleeping areas of homes while exhausting stale air at an equal rate from the bathrooms. This proactive approach to ventilation can result in improved indoor air quality.

Improved comfort. Buildings with tight construction and balanced ventilation systems can have fewer drafts and a constant supply of outdoor air resulting in improved comfort.

Improved health. Stale air can cause health problems. It can be responsible for symptoms such as headaches, drowsiness, and respiratory problems. These symptoms are more common in homes with poor ventilation and moisture control. Continuously providing fresh air can result in the improved health and well being of the occupants.

Lower utility bills. Less energy is consumed to operate ventilation systems than to heat and cool excessive amounts of outdoor air that infiltrates leaky homes. Additional savings are captured when these systems are equipped with either a sensible or total heat exchanger. This can result in lower utility bills, making homes less expensive to operate.

Balanced ventilation systems can be equipped with a heat exchanger that recovers most of the heating and cooling energy from the exhaust air.

Mechanical ventilation and natural ventilation have many applications where they are used, but in most modern intelligent design both are used for the best effectiveness and efficiency.

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Cahaya dan pengudarran semula jadi
⁃ tiap-tiap bilik yang direkabentuk bagi maksud kediaman , perniagaan atau lain-lain  kecuali hospital dan sekolah dilengkapkan dengan pengcahayaan dan pengudaraan semula jadi melalui satu atau lebih tingkap iaitu 10% dari luas lantai dan mempunyai kawasan terbuka laluan udara 5% dari luas lantai
⁃ bilik hospital yang menempatkan pesakit-pesakit dengan keluasan tingkap 15% dari keluasan bilik dan 7 1/2 % ruang terbuka bagi pengudaraan
⁃ Bilik sekolah pula dalam 20% pengcahayaan ,10%ruang terbuka
⁃ Bilik - bilik tandas , bilik mandi dan tempat buang air dalam 0.2persegi bagi satu bilik mandi , tandas dan lain lain

Luas minima bilik-bilik dalam bangunan
⁃ luas bilik kediaman = 11 meter persegi , >9.3 meter persegi , >6.5 meter persegi
⁃ lebar bilik kediaman > 2meter
⁃ luas dan lebar dapur : >4.5m, lebar >1.5m

Dimesi minimum tandas , jamban pam dan bilik mandi
⁃ tandas atau jamban pam dengan pasangan jamban duduk  -1.5mx 0.75m
⁃ Bagi jamban pam berpasangan dengan lain-lain  -1.25mc0.75m
⁃ Bilik mandi : luas >2meter persegi , lebar 0.75meter persegi

Tinggi bilik dalam bangunan kediaman , rumah kedai , skolah dan lain-lain
⁃ rumah kediaman : tinggi bilik >2.5m, tinggi dapur> 2.25m, tinggi bilik mandi, jamban ,anjung ,beranda graj dan lain - lain > 2m
⁃ Rumah kedai : tinggi bilik >3m
⁃ Sekolah : tinggi bilik >3m
⁃ Hospiital : tinggi bilik >3m
⁃ Kilang : tinggi bilik >3m

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Natural Ventilation and Human Comfort (Chapter 3)

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EXHAUST VENTILATION SYSTEM

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Ventilation Basics Series #2 - System Types

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- It is essential with this system that the air is heated before it is forced into the building.
- The system may be used for boiler rooms, offices and certain types of factories.
- The air may be heated in a central plant and distributed to the various rooms, or a unit fan convector may be used.

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Example Of Exhaust Ventilation System

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Processing of mechanical inlet toward a natural extracts

video link
https://youtu.be/UmWWZdJR1hQ

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Natural inlet and mechanical inlet

- inlet by natural ventilation and outlet by using mechanical extract system
- air moves towards the fan ( ekzos fan)  and displaced with fresh outside air
-ex:bathrooms, laboratory, kitchen, industrial building
-non domestic building is suitable for mechanical exhaust system
-prevent egress of contaminants
-combustion products cant be under high pressure - back drought (explosive)

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Group 6(C)
BAHAGIAN III (1)
-Jika pengudaraan secara mekanikal telah dicadangkan, dan pecahayaan semulajadi dari sebuah bangunan atau ruang yang mempunyai pengudaraan semulajadi, boleh diketepikan mengikut budi bahasa pihak berkuasa tempatan.

BAHAGIAN III (2)
-sesuatu permohonan yang mempunyai pengudaraan mekanikal dan ingin bertukar ke pengudaraan semulajadi  kerana perlu melakukam beber Syarat

BAHAGIAN III (3)
-Jika sesuatu bangunan itu ingin ditukarkan dari penggunaan udara semula jadi kepada pengudaraan mekanikal maka akan terpakainya peruntukkan jadual ketiga undang-undang kecil.

BAHAGIAN III (4)
-jika sesebuah tandas itu menggunakan pengudaraan secara mekanikal dan disenggara mengikut kehendak-kehendak jadual ketiga maka undang-undang melibatkan pengudaraan semula jadi dan pencahayaaan semula jadi tidak akan terpakai

Group 6(C)
BAHAGIAN III (1)
-Jika pengudaraan secara mekanikal telah dicadangkan, dan pecahayaan semulajadi dari sebuah bangunan atau ruang yang mempunyai pengudaraan semulajadi, boleh diketepikan mengikut budi bahasa pihak berkuasa tempatan.

BAHAGIAN III (2)
-sesuatu permohonan yang mempunyai pengudaraan mekanikal dan ingin bertukar ke pengudaraan semulajadi  kerana perlu melakukam beber Syarat

BAHAGIAN III (3)
-Jika sesuatu bangunan itu ingin ditukarkan dari penggunaan udara semula jadi kepada pengudaraan mekanikal maka akan terpakainya peruntukkan jadual ketiga undang-undang kecil.

BAHAGIAN III (4)
-jika sesebuah tandas itu menggunakan pengudaraan secara mekanikal dan disenggara mengikut kehendak-kehendak jadual ketiga maka undang-undang melibatkan pengudaraan semula jadi dan pencahayaaan semula jadi tidak akan terpakai

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MECHANICAL VENTILATION

1)What is mechanical ventilation
a)Provide by using mechanical
Example : Fans,aircond and blowers
blowers image(https://images.app.goo.gl/1pUKPd9afEuiLzjH9)

b)It is a man-made device that actively for pull fresh air in and push old air out
-Assist in the filtration and circulation of the air
c)Used to control indoor air quality
d)Excess : Humidity, odors and contaminants
-Controlled via dilution (pencairan) or replacement with outside air
-Humid climate (iklim lembab) much energy is required to
remove excess moisture from air
e)These type of systems are commonly installed in :-
-Bathrooms
-On or near the ceilings
Purpose-To remove moist air when showering
f)Mechanical ventilation system also installed above stovetops to :-
-Remove water vapor
-Cooking smells
-Exhaust the by-product of combustion for gas stoves
https://images.app.goo.gl/uvhMkLfJ9zj1qxhu7)
i)They are also installed in attics (loteng)
Purpose-To increase the amount of air exchange with the                            outside
-Reducing moisture buildup and mitigating the                                chances of mold

h)Ceiling fans and table/floor fans circulate air within a room
Purpose -Reducing the perceived temperature
-Ceiling fans do not provide ventilation as the                                 introduction of outside air

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Ventilation Basics Series #2 - System Types

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Group 5
Axial flow fans

-Axial flow fans are generally used in mines, tunnels, underground transportation, and industrial facilities for air conditioning and ventilation purposes.
-The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan.
-The propellers used in Axial Flow Fans are typically made of plastic, fabricated steel, cast aluminum or stainless steel.
-An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the number and shape of the blades. Fans have many applications including in wind tunnels and cooling towers. Design parameters include power, flow rate, pressure rise and efficiency.

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Group 5

"Mechanical" or "forced" ventilation

Apa itu propeller fans?

Kipas adalah sejenis kipas yang menghantar kuasa dengan menukar gerakan berputar ke teras.  Perbezaan tekanan dihasilkan antara permukaan hadapan dan belakang bilah berbentuk airfoil, dan cecair (seperti udara atau air) dipercepat oleh perbezaan tekanan.  Dinamik propeller, seperti pesawat sayap pesawat, dapat dimodelkan oleh prinsip Bernoulli dan hukum ketiga Newton.  Kebanyakan kipas marin adalah kipas skru dengan pisau helical berputar di sekitar paksi mendatar atau pendorong aci kipas.

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https://www.youtube.com/watch?v=d9btBXMocsc
Group 6
Mechanical or Forced ventilation :
Ruang terbuka:
1.Bagi setiap bangunan haruslah mempunyai ruang terbuka dengan mengikut dimensi atau ukuran yang telah ditetapkan oleh pihak berkuasa iaitu PBT.
2.manakala ruang terbuka tidak boleh diubah sewenangnya tanpa mengikut spesifikasi undang undang didalam UBBL. Sebarang perubahan Hendaklah Mendapatkan kelulusan Dari PBT. Pihak berkuasa akan mengeluarkan notis sekiranya Pemilik bangunan melanggar SPESIFIKASI UBBL.
3.untuk kawasan keliling bangunan yang bersempadan dengan jalan dan lorong belakang pula Setiap bangunan perlu menyediakan kawasan lapang tidak kurang dari 1/3 dari kawasan binaan. Jika dari bangunan sebelah tidak kurang dari 3000mm.  Sebagai contoh, setiap bangunan perlu ada setback yang ditetapkan oleh pihak berkuasa untuk kepentingan circulation seperti pejalan kaki, kenderaan, dan laluan services.

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Group 5

“MECHANICAL” OR “FORCED” VENTILATION

What is a centrifugal fans used for?
-to increase the volume of the air stream, which in turn moves them against the resistance caused by ducts, dampers and other components.

What is the benefits of centrifugal fans?
-First-rate energy efficiency
-Enhanced durability
-Ability to restrict overloading
-Easy to maintain
-High versatility
-Multiple sizes

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Group 6(C)
BAHAGIAN III (1)
-Jika pengudaraan secara mekanikal telah dicadangkan, dan pecahayaan semulajadi dari sebuah bangunan atau ruang yang mempunyai pengudaraan semulajadi, boleh diketepikan mengikut budi bahasa pihak berkuasa tempatan.

BAHAGIAN III (2)
-sesuatu permohonan yang mempunyai pengudaraan mekanikal dan ingin bertukar ke pengudaraan semulajadi  kerana perlu melakukam beber Syarat

BAHAGIAN III (3)
-Jika sesuatu bangunan itu ingin ditukarkan dari penggunaan udara semula jadi kepada pengudaraan mekanikal maka akan terpakainya peruntukkan jadual ketiga undang-undang kecil.

BAHAGIAN III (4)
-jika sesebuah tandas itu menggunakan pengudaraan secara mekanikal dan disenggara mengikut kehendak-kehendak jadual ketiga maka undang-undang melibatkan pengudaraan semula jadi dan pencahayaaan semula jadi tidak akan terpakai

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Mechanical Inlet And Extract

The air flow in and out from the building usually by using combination of fans and air conditioning.

A good mechanical ventilation method but costly

Suitable use for conference room, restaurant, shopping complex and etc.

By using this method, air velocity, humidity and air temperature factors will monitor and suit to any activities inside the building in order to achieve a good thermal comfort .

·        System selection depends on three main factors including the building configuration, the climate conditions, and the owner desire [2].

·        The design engineer is responsible for considering various systems and recommending more than one system to meet the goal and satisfy the owner of a building.

·         Some criteria can be considered such as climate change (e.g., temperature, humidity, and space pressure), building capacity, spatial requirements, cost such as capital cost, operating cost, and maintenance cost, life cycle analysis, and reliability and flexibility.

·        These constraints include the available capacity according to standards

Ø  building configuration

Ø   available space

Ø  construction budget

Ø  the available utility source

Ø  heating and cooling building    loads

https://www.youtube.com/watch?v=Z_2tM7KA5rQ

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Mechanical or forced ventilation

Axial flow fans

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Centrifugal fan

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LET'S SHARE YOUR KNOWLEDGE ON MECHANICAL VENTILATION!!

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LET'S SHARE YOUR KNOWLEDGE ON MECHANICAL VENTILATION!!