An air handling unit (“AHU”) is a standard piece of equipment that you’ll see in large and small industrial or commercial spaces. They are responsible for providing fresh air to different areas of the building.
Being the heart of the larger HVAC system (heating, ventilating, and air conditioning), the AHU manages ventilation by collecting outdoor air and room air (air already present in the building), filtering the air, adjusting the temperature and humidity, and then distributing a comfortable and refreshing supply of air-conditioning through ductwork inside the rooms of the building.
Function of an Air Handling Unit
The AHU is designed for spaces like hotel dining halls, function rooms, restaurants, and conference or convention centres that have restricted natural ventilation due to their high volume of simultaneous visitors.
It is also a good solution for locations with strict hygiene regulations, like manufacturing facilities, clean rooms, medical operating rooms, and laboratories. AHUs can also be utilised to ventilate spaces that, for instance, have underfloor heating or radiators for air conditioning.
Application of an Air Handling Unit
AHU can be set up on a rooftop, basement or alongside the outside of a building wall. It produces cooled or heated air and sends it to the rooms for cooling/heating. In contrast to regular industrial air conditioners, AHU are commonly custom made according to each individual’s or building’s requirements.
AHU can be custom designed by means of internally mounting a filter, humidifier and different parts to regulate temperature, humidity, air flow and air cleanliness.
Components of an AHU
Air intake
The component where outside air is pulled in, cleaned and distributed throughout the rooms. They can also pull indoor air that has been "recycled."
Filter
The air filtration equipment used will have a higher or lesser retention of particles, viruses, bacteria, odours, and other air contaminants based on the requirements for air purity. The filter will need to be changed on a regular basis.
Blower or fan
This electromechanical mechanism drives the air out of the AHU and into the ducts, where it is distributed throughout the rooms.
Heat exchangers
Heat exchangers are components that allow the temperature to be transferred between two fluids, in this case air and coolant, across a solid barrier.
Cooling coil
Air going through this module is cooled by the cooling coil. Water droplets may be produced during this process, and the built-in droplet separator allows them to be collected in a condensate tray.
Silencer
These are coatings that significantly lower the installation's noise level.
Plenums
Plenums are placed at void areas where the air flow is homogenized.
Types Of Air Handling Units
1. Horizontal and vertical units
Vertical units typically require less floor area.
2. Draw-through and blow-through units
The AHU is either a blow-through or draw-through mechanism depending on where the fan is located. The later AHU is the more commonly found.
3. Outdoor air (makeup air) or mixing units
While mixing units (as the name suggests) can utilise both recirculating air and outside air, makeup air units use only outdoor air.
4. Single-zone and multi-zone units
For dual-duct systems, a multi-zone AHU is more frequently employed
5. Rooftop and indoor units
There are specific AHU made for usage outside. They resist corrosion and are typically positioned on the roof. However, the majority of AHU are indoor units.
6. Custom-built and field-built units
Standard units are lower in cost and quicker to deliver. More versatility is available with custom-built AHU, which may also be made to be the most energy-efficient option.
Purpose of an Air Handling Unit
An AHU’s main objective is to increase energy effectiveness. Picking up discarded heat and reprocessing it through the AHU is done in conjunction with heat exchanger cooler units and specialised "run around" coils.
This feature lowers the demand placed on the heating coils and manages energy consumption.
Indoor and outside air are mixed during the cooling process to reduce the extreme hot/cold contrast when the air reaches the cooling coil and enable the unit to produce cool air with the least amount of energy.
What is the difference between an AHU and HVAC system?
Aspect | HVAC System | Air Handling Unit (AHU) |
|---|---|---|
Definition | A system responsible for heating, ventilation, and air conditioning in a building. | A part of the HVAC system that conditions and distributes air. |
Primary Function | Provides heating, cooling, and ventilation. | Handles and conditions air for optimal indoor air quality. |
Components | Boilers, air conditioning units, ducts, moisture vents. | Filters, fans, heating/cooling components, energy recovery systems, and dehumidifiers. |
Size | Typically large, requires dedicated space. | Can be large but compact depending on the system. |
Air Treatment | Controls temperature and humidity via various systems. | Primarily focuses on conditioning air, including filtration and dehumidification. |
Energy Efficiency | May include energy-efficient components but depends on the system. | Often integrates energy recovery systems to reduce energy consumption. |
Function in the System | The overarching system that includes multiple air and temperature control elements. | A subsystem within HVAC dedicated to improving indoor air quality and controlling airflow. |
Air Filtration | May or may not have filtration depending on the system. | Uses filters to remove pollutants from the air. |
Dehumidification | May include dehumidifiers as part of the system. | Includes dehumidifiers to control humidity levels. |
The Working Mechanism of AHUs
An Air Handling Unit (AHU) operates as the heart of a heating, ventilation, and air conditioning (HVAC) system. Its primary function is to regulate and circulate air within a building.
The process begins with air intake, either from outside the building (fresh air) or from within (return air). This air is then filtered to remove contaminants and impurities, ensuring a clean air supply.
The filtered air passes through heating or cooling coils, where it is conditioned to the desired temperature. A fan within the AHU circulates the air, distributing it through a system of ducts to various parts of the building.
Depending on the design, the AHU may also include humidifiers or dehumidifiers to regulate air moisture levels. Finally, the conditioned air is delivered into the building spaces, ensuring a comfortable and healthy environment.
Detailed Explanations of Each Component and Their Roles
Housing
The outer casing of the AHU protects internal components from external elements and noise.
Filter Section
Filters remove dust, pollen, and other airborne particles from the incoming air. Different types of filters, such as HEPA or activated carbon filters, are used depending on the application.
Heating and Cooling Coils
These coils adjust the air temperature. Heating coils are often powered by hot water, steam, or electricity, while cooling coils use chilled water or refrigerants.
Fan Section
The fan, either a centrifugal or axial type, ensures proper air circulation throughout the building.
Humidifiers/Dehumidifiers
These components regulate air moisture levels, ensuring optimal indoor humidity.
Dampers
Dampers control airflow by opening or closing pathways within the AHU, facilitating energy efficiency and proper ventilation.
Mixing Box
This section blends fresh air with return air to balance energy efficiency and indoor air quality.
Control Systems
Modern AHUs include advanced control systems to monitor and adjust temperature, humidity, and airflow automatically.
Advantages and Disadvantages of Different Types of AHUs
Advantages
Packaged AHUs
Compact and easy to install; ideal for small spaces and modular applications.
Custom AHUs
Highly versatile and customizable for specific needs; suitable for large-scale industrial or commercial applications.
Rooftop AHUs
Save indoor space and are easy to access for maintenance; particularly useful in urban areas.
Disadvantages
Packaged AHUs
Limited capacity and less flexibility for modifications.
Custom AHUs
Higher upfront costs and longer lead times due to customization.
Rooftop AHUs
Exposure to environmental elements may require additional weatherproofing and maintenance.
Real-World Applications of Air Handling Unit and Case Studies
Commercial Buildings
AHUs maintain consistent indoor temperatures and air quality in office spaces, contributing to employee comfort and productivity.
Case Study: A corporate office in New York City upgraded to energy-efficient AHUs, reducing energy costs by 20% while improving air quality.
Healthcare Facilities
AHUs ensure sterile and controlled environments in hospitals by regulating temperature, humidity, and air cleanliness.
Case Study: A hospital in Singapore implemented HEPA-filtered AHUs in its surgical suites, significantly lowering infection rates.
Industrial Plants
AHUs are used in manufacturing to regulate air temperature and humidity, ensuring optimal conditions for production processes.
Case Study: An electronics manufacturing facility in Germany installed customized AHUs to maintain precise humidity levels, improving product quality and reducing defects.
Educational Institutions
Schools and universities utilize AHUs to create comfortable learning environments, particularly in regions with extreme weather.
Case Study: A university in Australia installed rooftop AHUs, achieving efficient cooling in lecture halls and reducing their carbon footprint.
By understanding and incorporating these aspects, you can create a comprehensive and informative article that adds value to your readers and outshines competitors.
All in All
One great thing about AHU is the ability to install many AHUs at one exterior site. Outdoor commercial air conditioning units are typically mounted on rooftops or along the exterior walls of buildings, but internal units must be installed separately in each room.
Additionally, it costs money and takes time to maintain each indoor unit that is installed in a room. AHUs, in contrast, can be erected collectively in a single outside site, allowing maintenance to be carried out there.
AHUs are not without flaws. The building as a whole won't have air conditioning if the AHU breaks down. In order to offer backup, it is important to build multiple AHU.
Find out more about Air Handling Units (AHU) from us! Feel free to get in touch with our friendly consultants and know more about us.
Air Handling Units manufactured and assembled by TCW Group
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