Air conditioning is the process of conditioning of indoor air to maintain its temperature, humidity, velocity and cleanliness inside the room or desired location at a desired level for human comfort or any industrial process. Air handler or air handling unit (AHU) is one of the most essential and major parts of an air conditioning system. AHU is a large metal box that consists of a blower, heating or cooling elements, filter racks or chambers, sound attenuators and dampers. AHU is basically used to condition indoor air with their heating, cooling, humidification and de-humidification functions in a HVAC system.

Basic Components of an Air Handling Unit

An air handling unit consists of few important components. Those are as follows:

Casing

Casing is the insulated enclose of an AHU which keeps all the system components of an AHU safe inside and prevent the heat gain or loss from it. A schematic diagram of a typical air handling unit is shown in Fig. 1.

Duct

Two types of ducts are used in an AHU. These are the supply air duct and return air duct. The cool and conditioned air is supplied to desired locations from the AHU by the supply air duct, while the hot air from the room is again returned back to the air handling unit through return air duct. There is one main supply duct that is then divided into various small ducts those lead to all the rooms that are to be maintained at a specific condition. Similarly, the return ducts from all the rooms also end into one main duct. Insulating materials are used to cover those ducts to prevent the heat gain or loss from these ducts and the ducts are designed in such a fashion that the distribution should be equal to all the rooms and wastage should be minimal.

The Mixing Chamber

In this section, the fresh air from the environment is mixed with return air from the room. This is done to minimize energy consumption by taking advantage of the heating/cooling ability of the return air. In this system, fresh air is only required to supply the air change rate needed for comfort.

Damper openings are generally controlled manually or by servo motor. But the main issue is to allow air to circulate freely and facilitates installation in closed ducts. Thus, dampers are designed to allow synchronous control. The three-way mixing chamber has been designed for similar purposes. However, this system includes a fan for return air. The desired portion of return air is given back to the system and the remainder can be exhausted.

Filters

Filter is one of the very important components in an air handling unit. Filters are basically used to remove particles and contaminants of various sizes from the air. These air filters are usually placed at initial stage of an AHU to keep the downstream components clean.Generally, filters are placed in two or more successive stages with a coarse grade filter in front of a fine grade filter. Sometimes, final filtration medium is also there for further cleaning of the air.

Different types of air filters are used in an AHU and their performances are listed in table 1. The type of air filter being used is very much dependent on the application of the system.

Air filters may also be classified according to their applications such as:

  • Panel Filter

These types of filters are flat and rectangular in shape and provide a low efficiency filtration. The high velocity filters are arranged vertically whereas the low velocity filters are arranged in V shape. Typical air velocity through these types of filters ranges between 2-3 m/s.

  • HEPA Filter

HEPA Filters are very efficient and is able to achieve efficiency up to 99.97%. These filters are efficient in removing minute particles and airborne bacteria from the air. It is usually used in clean room applications such as semiconductor production floor, operation theaters and places undergoing critical processes.

  • Electrostatic Filter

Electrostatic Filter is used to remove particles from the air by using highly charged electrodes that ionized the air. Bag Filter is able to remove dust particles and is thrown away after use. Roll Filter is used for high velocity filtration where the used part is rolled up automatically or manually.

Fig 2: A Heating Unit                                      Figure 3: A Cooling unit

Cooling / Heating Arrangements

Temperature control is one of the major factors in an air handling unit. The perfect temperature for human comfort generally varied between 18°C – 23°C. So, for human comfort this temperature must be maintained by an AHU. Therefore, a cooling or heating or arrangement for both purposes is provided with the AHU. Heating and cooling is, generally, done by either direct type heat exchangers or indirect heat exchangers. Direct type heat exchanger includes burning of gaseous fuel in the air stream for heating or evaporator for cooling purpose. Electrical heater or heat pump can also be used to serve the purpose. While, in indirect heat exchangers hot water or steam or chilled water in pipe line can be used. These pipe lines are manufactured from copper and fins are provided which is made from copper or aluminum. Typical heating and cooling units have been shown in figure 2 and figure 3 respectively.

Humidifier / Dehumidifiers

Another very important parameter while designing an air handling unit is humidity. A humidity comfort level in the range of 45% – 55% relative humidity (RH) should be maintained. The humidity of the air sometimes goes very low causing discomfort to the occupants during the peak season of winter or the vice versa during summer. That makes the manufacturers to think about the necessity of humidifier in air conditioning system. Figure 4 shows a pictorial view of a humidifier. The humidity of the air can be increased or decreased according to the requirement using the humidifiers or de-humidifiers. Various types of humidifier are commonly used in an AHU. Those are:

  • Spray Type

Spray type humidifier has a header and spray nozzles that spray water with a pressure of 15 psi or more.

  • Steam Pan Type

Steam Pan Type humidifier has a pan and a heating coil to heat up the water of the pan. The evaporation of water caused by the heating will increase the humidity level of the surrounding air.

  • Steam Grid Type

Steam Grid type humidifier has tiny holes on the pipe to distribute the steam that flows through it. In this case, the water that is heated up to produce the steam to be supplied to the grid is conditioned to prevent odor being discharged to the room.

Fig 4: Humidifier

Fans

Another very important component in an air handling unit is fan or blower. The hot return air from the room is first sucked and then blows it over the cooling coil where the hot air is cooled and then that is sent to the room to be conditioned. This is done by the fan or blower arrangements in an AHU. In general, two types of arrangement of fan are there in an AHU: draw though arrangement and blow through arrangement. The return air is sucked through the filter, the cooling coil and humidifier in the draw through arrangement. While passing through the filters, humidifier and cooling coil, the air gets conditioned and then it is sent to the required location. But, in case of the blow through arrangement the fan absorbs the return air and blows it over the air filter and the cooling coil. The air then flows to the rooms to be air conditioned. The draw through arrangement is used more commonly due to its compactness. The fans that are used in AHU are basically of centrifugal types. Figure 5 shows the pictorial view of fan unit used in an air handling unit.

Fig 5: Fan unit

Difference between Air Handling Unit and Fan Coil Unit

Though both air handling unit (AHU) and fan coil unit (FCU) serves the same basic function of cooling in a HVAC system, there are few differences between those two units. Those are:

  • AHU is generally bigger system than a FCU.
    • AHU is more complex than FCU.
    • AHU is generally used in bigger establishments
    • AHU systems needs ducting whereas, FCU does not need any duct work.
    • AHU system takes outside air into the system whereas, FCU just recycles air.
    • AHU is used for filtering, heating or cooling and humidification or dehumidification of air while FCU just cools or heats air.
    • AHU is less noisy than FCU.

Fig 6: Grills and Registers

Air Distribution System

After transmitting conditioned supply air from the air handling unit to the room, it has to be distributed to the conditioned space. So, it is very important to design the air distribution system properly. It is found that sometimes the efficiency of an air distribution system becomes low in the range of 60 – 75% due to the poor design. There is a scope of improving the efficiency upto 80% or more with proper installation of distribution system. Proper designing and installation of the air distribution system can save money up to 50 – 200$ per year. Moreover, efficient distribution system also reduces the equipment size.

Types of Air Distribution Devices

Different types of air distribution devices are being used in HVAC systems recently. These are:

  • Grilles and Registers

Grilles are the outlets for supply air or inlets for return air whereas, registers are the grille with a volume control damper. Figure 6 shows the front view of a supply air grille with horizontal and vertical vanes that are basically used for deflecting airflow. Grilles have a comparatively lower entrainment ratio, greater drop, longer throw and higher air velocities in the occupied zone compared to slot and ceiling diffusers. The performance of the grilles are specified in terms of core size or core area, volumetric flow rate of air, effective air velocity, total pressure drop, throw and noise levels. They can be mounted either on the sidewalls or in the ceiling.

  • Ceiling Diffusers

A ceiling diffuser consists of concentric rings or inner cones made up of vanes arranged in fixed directions. Ceiling diffusers can be round, square or rectangular in shape. Square and rectangular ceiling diffuser has been shown in figure 7. A square diffuser is the most commonly used diffuser for supplying air. The supply air is discharged through the concentric air passages in all directions. The adjustable inner cones or the deflecting vanes are provided to change the air distribution pattern. These types of diffusers are normally mounted at the center of the conditioned space and those can provide large entrainment ratio and shorter throw for conditioned spaces with low head space.

  • Slot Diffusers

Slot diffusers are made up of plenum box with single or multiple slots and air deflecting vanes. These types of diffusers are mounted on either side of walls or in the ceiling. Linear slot diffusers are mounted on the sidewalls of the conditioned room. These are used for supplying both supply air and return air. These diffusers are particularly suitable for large open-spaces as long as 30 meters in length that require flexibility to suit changing occupant distribution. Figure 8 shows the photograph of conditioned space with linear slot diffusers mounted on the ceiling.

Fig 7: Ceiling Diffuser

Fig 8: Slot Diffuser

Types of Air Distribution Systems

Two types of air distribution system are commonly used for maintaining the room conditions. Those are:

  • Constant Volume

Constant-volume systems are operated at a constant airflow rate and only the temperature varies to maintain the zone set point. Constant-volume units can be used in single-zone or multi zone applications. This type of system can use single duct or dual duct for the distribution of air. A single-duct system provides ventilation and cooling to the conditioned space. If heating is required then a heating unit is provided in the terminal unit or a separate system for heating may be introduced. A dual-duct system can distribute both hot and cold air by using a single fan to move air through both cooling and heating coils in the air handler. The supply air can be distributed by separate duct to the desired locations depending on the zone requirements. Another constant-volume system is the multi zone unit. The multi zone unit supplies air to several zones from a centrally located air-handling unit. Individual zone requirements are met by mixing cold and warm air through dampers in the air handler. The conditioned air is then distributed to the zones via single ducts.

  • Variable Air Volume (VAV)

A variable air volume (VAV) can vary the air flow at a constant temperature. In a VAV system one supply duct distributes supply air at a constant temperature. As the supply air temperature is constant, the air flow rate must vary to meet the rising and falling heat gains or losses within the thermal zone served. This type of system has many advantages over constant volume system. In this system, the supply air flow rate can be varied. The precise control of temperature, reduced compressor wear can be achieved in this system. This system consumes less power to run the system fans and makes less noise compared to constant volume system.

If you want to share thoughts or feedback then please leave a comment below.

RELATED ARTICLESMORE FROM AUTHOR

91 COMMENTS

  3. I’m impressed, I must say. Seldom do I come across a blog that’s both
    equally educative and amusing, and let me tell you, you’ve hit the nail
    on the head. The issue is something too few folks are speaking
    intelligently about. I’m very happy that I came
    across this during my hunt for something concerning this.

    Here is my blog post animals

  6. Have you ever considered publishing an ebook or guest authoring on other websites? I have a blog based upon on the same subjects you discuss and would really like to have you share some stories/information. I know my readers would value your work. If you’re even remotely interested, feel free to send me an e mail.

  11. Hi there exceptional website! Does running a blog such as this take a great deal of work? I have absolutely no knowledge of computer programming but I had been hoping to start my own blog soon. Anyhow, if you have any recommendations or tips for new blog owners please share. I know this is off subject however I simply had to ask. Thank you!

  12. My coder is trying to persuade me to move to .net from PHP. I have always disliked the idea because of the expenses. But he’s tryiong none the less. I’ve been using WordPress on a number of websites for about a year and am nervous about switching to another platform. I have heard good things about blogengine.net. Is there a way I can transfer all my wordpress content into it? Any kind of help would be greatly appreciated!

  13. You are so cool! I do not think I have read anything like this before. So good to discover someone with some original thoughts on this topic. Really.. thank you for starting this up. This site is something that is required on the internet, someone with a bit of originality!

  19. Magnificent goods from you, man. I’ve understand your stuff previous to and you are just extremely great. I really like what you have acquired here, certainly like what you are stating and the way in which you say it. You make it enjoyable and you still take care of to keep it smart. I can not wait to read far more from you. This is actually a wonderful web site.

  22. You really make it seem really easy with your presentation however I in finding this matter to be actually something that I think I would never understand. It seems too complicated and very huge for me. I’m having a look forward for your subsequent submit, I’ll try to get the grasp of it!

  24. Today, I went to the beach with my kids. I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed the shell to her ear and screamed. There was a hermit crab inside and it pinched her ear. She never wants to go back! LoL I know this is completely off topic but I had to tell someone!

  26. What i don’t realize is in truth how you are not really a lot more neatly-appreciated than you may be now. You’re so intelligent. You know thus considerably with regards to this matter, produced me individually consider it from numerous numerous angles. Its like women and men aren’t interested unless it’s something to accomplish with Girl gaga! Your individual stuffs nice. At all times take care of it up!

  33. Good day! I know this is kind of off topic but I was wondering which blog platform are you using for this site? I’m getting sick and tired of WordPress because I’ve had issues with hackers and I’m looking at options for another platform. I would be awesome if you could point me in the direction of a good platform.

  34. 3 Pin Connectors
    Фланец приварной воротниковый ГОСТ
    Wire Connector Block
    Фланец пластинчатый gost -33259
    Cable Terminal
    Waterproof Cable Connector
    Глухой фланец из нержавеющей стали 150 фунтов
    http://www.jofu.tw
    Глухие фланцы из нержавеющей стали
    グランドラグジュアリー
    Фланец из нержавеющей стали
    Types Of Connectors

  35. Please let me know if you’re looking for a article writer for your site. You have some really great articles and I believe I would be a good asset. If you ever want to take some of the load off, I’d absolutely love to write some material for your blog in exchange for a link back to mine. Please shoot me an email if interested. Regards!

  52. What you published made a ton of sense. However, what about this? what if you added a little information? I am not saying your information is not solid., however suppose you added a headline to maybe grab people’s attention? I mean %BLOG_TITLE% is kinda plain. You should look at Yahoo’s home page and watch how they create article titles to get viewers to click. You might add a related video or a related pic or two to grab people excited about what you’ve got to say. In my opinion, it might make your website a little bit more interesting.

  57. First of all I would like to say terrific blog! I had a quick question which I’d like to ask if you do not mind. I was curious to find out how you center yourself and clear your mind before writing. I’ve had a tough time clearing my thoughts in getting my ideas out there. I truly do enjoy writing but it just seems like the first 10 to 15 minutes are generally wasted simply just trying to figure out how to begin. Any suggestions or tips? Appreciate it!

  60. Wonderful items from you, man. I’ve understand your stuff previous to and you’re simply too wonderful. I really like what you have received right here, certainly like what you are stating and the way in which wherein you are saying it. You’re making it entertaining and you still care for to stay it smart. I cant wait to read far more from you. That is really a great website.

  64. オシャレ感抜群のバッグ選び
    Wheel Straps For Towing
    alma mm louis vuitton
    ブランドバッグ
    Endless Sling Rigging
    Ratchet Tie Down Straps
    Садовый Насос
    lv iphone cases
    louis vuitton ipad 2
    使いやすさとデザイン
    artsy gm louis vuitton
    louis vuitton used handbags
    Polyester Strapping Tools
    Borosilicate Glass Pepper Mill Ceramic Grinder
    http://www.heraconcept.gr
    Интеллектуальный Преобразователем Частоты Насос
    おしゃれの深み
    大人のオシャレ感
    4 Inch Heavy Duty Ratchet Tie Down
    Помпа
    Поверхностный Насос

  70. Hey I am so delighted I found your site, I really found you by accident, while I was researching on Askjeeve for something else, Regardless I am here now and would just like to say many thanks for a fantastic post and a all round enjoyable blog (I also love the theme/design), I don’t have time to look over it all at the moment but I have saved it and also added your RSS feeds, so when I have time I will be back to read much more, Please do keep up the awesome work.

  72. Cast Iron Enamel Round Casserole
    ブランドバッグ
    Cast Iron Enamel Shallow Round Casserole
    louis vuitton shopping
    white louis vuitton
    Night Light
    バッグとカジュアルデート
    Suspender
    louis vuitton purses cheap
    louis vuitton bags sale
    men louis vuitton shoes
    Luggage Cart Small Size
    Mens Orange Neckties
    Commercial Electric Water Boiler
    Under Cabinet Led Light Fixtures
    pawilony.biz.pl
    トレンド感満載のアイテム
    LED dimmable cabinet light
    人気アイテムをチェック
    Cast Iron Enamel Oval Casserole
    バッグのアクティブライフスタイル

  76. http://www.okinogu.or.jp
    トレンド感抜群のコーディネート
    louis vuitton bookbag
    Clear Plastic Film Roll
    louis vuitton dog carrier
    Food Packaging Bags
    Baits Packaging Pouch
    Aluminum Foil Bag
    Циркуляционный Насос
    Коммерческая Центрифуга
    Трубопроводный Насос
    louis vuitton pattern
    人気ブランドを手に入れよう
    Plastic Bags For Packaging Food
    人気ブランド特集
    louis vuitton galliera pm
    Солнечный Насос
    トレンドバッグ特集男子会
    ファッション好きと語り合いたい
    louis vuitton luggage set
    Двойной Всасывающий Насос

  87. I truly love your site.. Pleasant colors & theme. Did you make this web site yourself? Please reply back as I’m looking to create my own personal site and would love to know where you got this from or just what the theme is called. Kudos!

  91. dynamic balancing

    Dynamic Balancing: The Key to Smooth Operations
    Dynamic balancing is a critical process essential for the effective functioning of various rotating machinery. It serves to address both static and dynamic imbalances that can cause vibrations, ultimately leading to inefficiency and damage. The importance of dynamic balancing cannot be overstated, particularly in industries where heavy machinery operates continuously, such as in crushers, fans, mulchers, centrifuges, turbines, and more.

    Understanding Dynamic vs. Static Balance
    The distinction between static and dynamic balance is crucial in comprehending the complexities of rotor balancing. Static balance pertains to situations where the rotor is stationary. In static imbalance, the rotor’s center of gravity is offset from its axis of rotation. This imbalance leads to a force that consistently attempts to reposition the rotor to align the heavier side downward. Static balancing works to eliminate the uneven mass distribution in a plane—typically for narrow, disk-shaped rotors—allowing them to operate without undue wear or vibration.
    In contrast, dynamic balance comes into play when the rotor is rotating. Dynamic imbalance involves mass displacements occurring in different planes, which generate both forces and moments that result in vibrations during operation. Unlike static imbalance, the forces in dynamic imbalance interact across multiple planes, which prevents simple adjustments from solving the issue. For effective dynamic balancing, specialized equipment like vibration analyzers and devices designed for multi-plane balancing become necessary.

    The Process of Dynamic Shaft Balancing
    To achieve dynamic balancing of shafts, the use of portable instruments like the Balanset-1A balancing device is paramount. This powerful tool allows for dynamic balancing in two planes, making it versatile and practical for various types of rotors. The balancing process begins with initial vibration measurements taken while the rotor is mounted and spinning. These measurements provide the baseline data needed for subsequent adjustments.
    Upon establishing the baseline, calibration weights are applied strategically on the rotor to observe changes in vibration. The carefully monitored data allows operators to determine the effect of the added weight on balance. Adjustments are recorded, and results are analyzed to identify the optimal locations for corrective weights that will rectify the imbalance. The angle and mass of the corrective weights are calculated meticulously, which leads to installing them in the determined locations.
    Following the installation of corrective weights, the rotor undergoes a re-evaluation. The final measurements are compared to the initial data to ascertain the effectiveness of the corrective steps. A successful dynamic balancing process will depict significantly reduced vibration levels, signifying a harmonious operation.

    Benefits of Dynamic Balancing
    The advantages of dynamic balancing cannot be ignored. Proper balancing of rotors ensures smoother operations, leading to enhanced efficiency and longevity of machines. By addressing imbalances proactively, companies can minimize incidents of wear and tear, reducing the need for repairs and downtime in production processes.
    Moreover, dynamic balancing has a direct impact on safety measures in the workplace. Vibration-related failures can lead to severe accidents. By applying dynamic balancing techniques, businesses foster a safer operating environment, consequently enhancing their overall operational flow.

    The Dynamic Balancer – Balanset-1A
    The Balanset-1A is at the forefront of dynamic balancing technology. This portable balancer and vibration analyzer combines precision, versatility, and efficiency, making it indispensable for engineers and maintenance personnel who aim to ensure optimal performance of rotating equipment. The device is equipped with two channels, specifically designed to cater to complicated balancing needs across a broad spectrum of applications.
    Whether it’s a fan, turbine, or auger, the Balanset-1A adapts efficiently, providing vital data that guides the balancing process. The era of traditional balancing methods has evolved significantly with this advanced technology, allowing for more accurate and rapid assessments of rotor stability.

    Conclusion: Emphasizing Dynamic Balancing
    Dynamic balancing represents a vital aspect of maintaining the operational integrity of rotating machinery. Its process addresses both static and dynamic imbalances, ensuring that machines like crushers, fans, and turbines perform efficiently without excessive vibrations. By implementing dynamic balancing techniques, businesses can safeguard their investment, enhance safety, improve productivity, and prolong the lifespan of critical equipment.
    For anyone involved in the maintenance of rotating machinery, understanding and applying the principles of dynamic balancing is essential not just for immediate performance but also for long-term operational success. The investment in dynamic balancing tools, such as the Balanset-1A, will undoubtedly pay dividends in the quest for mechanical excellence.

LEAVE A REPLY

Please enter your comment!
Please enter your name here