9.3 Air Handling Units Explained

Key Concepts

1. Definition and Structure

Air handling units (AHUs) are mechanical systems that control and circulate air as part of a heating, ventilating, and air conditioning (HVAC) system. They typically consist of a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers.

2. Components

The main components of an air handling unit include:

• Blower: A fan or blower that moves air through the system.
• Heating Elements: Coils or elements that heat the air, such as electric heating coils or hot water coils.
• Cooling Elements: Coils that cool the air, typically using refrigerant or chilled water.
• Filters: Devices that remove dust and other contaminants from the air.
• Dampers: Adjustable plates that control the flow of air.
• Sound Attenuators: Devices that reduce noise generated by the blower and other components.

3. Operation

The operation of an air handling unit involves the following steps:

1. Air Intake: Air is drawn into the unit through filters to remove contaminants.
2. Heating/Cooling: The air is either heated or cooled as it passes through the respective elements.
3. Air Distribution: The treated air is then distributed through the building via ductwork.
4. Exhaust and Return: Some air is exhausted to the outside, while some is returned to the unit for recirculation.

4. Types of Air Handling Units

There are several types of air handling units, including:

• Packaged Units: All components are housed in a single cabinet, suitable for small to medium-sized buildings.
• Modular Units: Components are separate but designed to work together, offering flexibility in installation and maintenance.
• Custom Units: Tailored to specific building requirements, often used in large commercial or industrial applications.

Examples and Analogies

Definition and Structure

Think of an air handling unit as a kitchen appliance that prepares and distributes food. The blower is like the mixer that blends ingredients, the heating elements are like the oven that cooks the food, and the filters are like sieves that remove unwanted particles.

Components

Consider the blower as the heart of the system, pumping air throughout the building. The heating and cooling elements are like the thermostat that adjusts the temperature, and the filters are like the immune system that protects the building from pollutants.

Operation

Imagine the air handling unit as a conveyor belt in a factory. Air enters the unit, gets processed (heated or cooled), and then moves on to be distributed to different parts of the building, just like products on a conveyor belt.

Types of Air Handling Units

Think of packaged units as a ready-to-eat meal, modular units as a DIY kit, and custom units as a tailor-made suit. Each type serves a different purpose and is suited to different needs.

Insightful Content

Understanding the structure and operation of air handling units is crucial for anyone working in HVAC. By mastering the principles of air circulation and the design features of AHUs, you can ensure the efficient and effective operation of these systems. The ability to visualize the air handling process and relate it to everyday objects can make complex concepts easier to grasp and apply in real-world scenarios.