The Unsung Heroes of Indoor Environments

As part of an HVAC system, an Air Handling Unit (AHU) is a device that controls and circulates air. An AHU is primarily designed to draw in outside air, heat or chill it, filter out impurities, and circulate the air inside space to provide a comfortable and healthy indoor atmosphere. AHUs can range in size from tiny, compact units for domestic usage to huge, sophisticated systems for industrial purposes. They are usually found in mechanical rooms or on rooftops.

AHUs are essential for maintaining a comfortable indoor climate and guaranteeing indoor air quality. They contribute to creating a healthier and cozier living or working environment by eliminating stale air, lowering humidity levels, and filtering out toxins.

Components of AHU

AHUs consist of several key components, each playing a vital role in the unit’s overall functionality. Understanding these components helps in appreciating how AHUs work to condition and circulate air.

• Fans: There are two types of fans that are generally there in an AHU – Supply fans and Return fans. The supply fans draw the air inside the duct and push it through the duct line, while the return fans exhaust air out of the conditioned space. These fans complement each other to keep the proper balance and movement of air within the system.
• Filters: Filters are useful for removing particulates and contaminants from the air. They ensure that the air being circulated in the conditioned space is clean, which is vital for maintaining indoor air quality. There are different types of filters, including pre-filters, fine filters, and HEPA filters, each serving a specific purpose.
• Heating and Cooling Coils: The air that passes through the unit is kept at a constant temperature by these coils. In the winter, heating coils are used to warm the air; in the summer, cooling coils are used to cool the air. Usually, a boiler or chiller is linked to these coils.
• Humidifiers and Dehumidifiers: These components control the moisture level in the air, maintaining optimal humidity levels for comfort and health. Humidifiers add moisture to the air when it is too dry, while dehumidifiers remove excess moisture when the air is too humid.
• Mixing Box: This component mixes return air from the conditioned space with fresh outside air. By balancing the mix of fresh and returned air, the mixing box helps optimize indoor air quality and energy efficiency.

• Dampers: To maximize energy efficiency and comfort, dampers control the airflow inside the Air Handling Unit (AHU) and can modify the proportion of return and fresh air. For more exact control, they can be manually or automatically operated.
• Heat Exchangers: Utilizing heat exchangers allows energy from exhaust air to be recovered and transferred to entering fresh air. This enhances the HVAC system’s overall efficiency and lowers energy usage.
• Control Systems: Modern AHUs are equipped with advanced control systems that monitor and regulate various parameters such as temperature, humidity, and airflow. These systems ensure optimal performance and energy efficiency.
• Sound Attenuator: This device’s purpose is to reduce noise from outside air intake and, in the event of a double-flow setup, to reduce noise from the exhaust rejection.

Classification of AHUs

AHUs have different types and can be classified according to certain factors as given hereafter.

Location of the AHU to be placed, such as:

Outdoor/Rooftop AHU: AHUs that are mounted usually on the roof. They are corrosion and water-resistant as they are made with heavy galvanized steel or aluminium sheets.

• Indoor AHU: These are usually found in the fan rooms or even sometimes can be compacted in the ceiling or hung in the ceiling.

Placement of its components throughout the unit. Some of the examples of the same are:

• Horizontal AHU: If all the parts are placed at a horizontal level, it is called a Horizontal Unit. These types need more floor space for installation.
• Vertical AHU: If all the parts are placed in a vertical level, it is known as a Vertical unit. It requires less space and is usually placed in the fan room or the AHU room.
• Modular AHU: These are modular components that can be customized and put together on location. Because of its versatility, modular AHUs can be customized to match the unique needs of various structures. They are frequently employed in sizable commercial and industrial settings where scalability and flexibility are crucial.

Placement of fan concerning the cooling coil. Two major types are:

• Blow-through Unit: This kind of AHU uses a fan to circulate air through filters, a mixing box, and a cooling coil before it enters the ducting network.

• Draw-through Unit – Before the air reaches the ducting network, it is drawn through a cooling coil, a mixing box, and filters by means of a fan. AHUs with draw-through might be horizontal or vertical.

Significance of AHUs

AHUs are significant for several reasons, impacting both the comfort and health of building occupants and the efficiency of the building’s HVAC system.

• Indoor Air Quality (IAQ): AHUs are essential to preserving good indoor air quality. They contribute to the creation of a healthier environment by removing pollutants and regulating humidity levels. This is especially crucial in places like offices, schools, and hospitals where poor air quality can cause illnesses and lower productivity. A high IAQ is crucial for residents’ health since it lowers the risk of respiratory disorders and other conditions.
• Energy Efficiency: Energy efficiency is a key design feature of modern AHUs. Precise temperature and airflow management is made possible by features like high-efficiency filters, variable speed fans, and sophisticated control systems. This minimizes operational costs in addition to consuming less energy. Energy-efficient AHUs can drastically lower a building’s overall carbon footprint and support sustainable building practices.
• Thermal Comfort: AHUs provide thermal comfort for building occupants through temperature and humidity regulation. This is essential for establishing a comfortable home or workplace, as it has a big influence on occupant happiness and output. Regardless of the outside weather, maintaining a suitable interior climate throughout the year depends on proper thermal comfort.
• Versatility and Customization: AHUs can be tailored to each building’s unique requirements. Air Handler Units (AHUs) can be tailored to meet the specific needs of different types of spaces, be they big industrial facilities or compact residential apartments. Because of their adaptability, they are essential to contemporary HVAC systems since they enable customized solutions that satisfy the particular requirements of various settings.
• Enhanced Control and Monitoring: AHUs provide improved monitoring and control capabilities through the integration of sophisticated control systems. Real-time monitoring and parameter adjustment by building operators ensure peak performance and prompt resolution of any difficulties. The efficiency and dependability of the system are improved by this degree of control.

Challenges and Future Trends

When it comes to modern HVAC systems, AHUs play a crucial role, but they encounter various challenges. It’s vital to address these challenges and stay abreast of upcoming trends to ensure the continuous advancement and enhancement of AHUs.

• Maintenance: Ensuring optimal performance and longevity of AHUs requires regular maintenance. This involves tasks such as cleaning filters, examining coils, and looking out for any indications of wear and tear. However, maintenance can prove to be time-consuming and expensive, particularly in extensive buildings with multiple AHUs. The necessity for skilled technicians and adherence to regular maintenance schedules can contribute to operational expenses.
• Energy Consumption: Even with improvements in energy efficiency, AHUs can remain substantial users of energy. Research is continuously working towards creating even more effective components and control systems. The difficulty is in maintaining a balance between energy efficiency and the requirement for efficient air conditioning and ventilation. Ongoing advancements in energy-efficient technologies and materials are crucial for lowering the energy usage of AHUs.
• Integration with Smart Technologies: The integration of smart building technologies holds the key to the future of AHUs. This encompasses incorporating advanced sensors, AI-powered control systems, and IoT connectivity to enhance performance and efficiency even further. By being able to adjust to changing conditions in real time, smart AHUs optimize air handling processes and minimize energy usage. Additionally, the incorporation of smart technologies allows for predictive maintenance, thereby reducing downtime and enhancing system reliability.
• Environmental Impact: Minimizing the environmental impact of AHUs presents a crucial challenge, which involves decreasing the use of harmful refrigerants, cutting down on energy consumption, and enhancing the recyclability of AHU components. Sustainable design methods and the utilization of eco-friendly materials are imperative in lessening the environmental footprint of AHUs.

• Cost: The installation of AHUs can be quite expensive at first, especially for larger or customized units. It can be a challenge for building owners and operators to find the right balance between cost, performance, and energy efficiency. Although the long-term energy savings can make up for the initial investment, the high upfront cost may deter some projects.
• Technological Advancements: Keeping up with the rapid changes in technology is a constant task. Manufacturers of AHUs need to constantly innovate and update their products in response to new technology if they want to stay competitive. This means making constant investments in R&D and having a strong commitment to staying on the leading edge of technical advancements.

Conclusion

The Air Handling Unit is truly an unsung hero of comfort and a cornerstone of modern HVAC systems. It plays a vital role in maintaining thermal comfort and air quality while balancing energy efficiency. These systems are composed of different components that individually and together play a vital role in meeting the specific requirements.

There are multiple significances as stated but there are also challenges faced such as maintenance, energy consumption, and the need for integration with smart technologies must be addressed to ensure continued improvement and sustainability.

Coming to the future of AHUs, the innovation lies in the merger of advanced technologies that ensure better performance and lowered environmental impact. The technology of AHU will keep on building, becoming more efficient and integrated with smart building systems. Their role in creating comfortable, healthy, and sustainable indoor environments underscores their importance in contemporary building design and operation.

Ankit Kumar is currently working as Senior Floor Plan Designer (Creatives) in Cvent, however, he has been involved in various HVAC projects in the initial years of his career such as being a core team member for Mass Mutual (Singapore) in designing/modelling their entire HVAC to list a few.