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Heating Ventilation and Air Conditioning Full Course - HVAC Course (Part 55)


 In this part of Full HVAC Course, We will learn about Air Distribution in HVAC..

Air Distribution in HVAC

Air distribution principles in HVAC systems are an important part of HVAC design and an understanding of this system makes efficient use of available energy and cost efficient use of HVAC systems.

Air flow in HVAC systems provides heating and cooling comfort through a sequence of changes in air temperature and pressure.

The proper design of the air distribution network is critical to the efficiency of HVAC systems.

Many types of air distribution systems exist, but common ones include convection, convection with diffusion and damping, forced air, forced air, ambient air, and an air handler or a building’s own air source.

The proper layout of the air distribution network is critical to the efficiency of HVAC systems and can be found in most design plans.

Each type of system requires the placement of various types of components, such as inlet systems, control systems, return air systems, and chimneys or ducts.

Air diffusing is when cold air is circulated from an outside source into a building, typically air conditioning equipment, causing the air to warm up.

Air diffusion is often used for heating systems when it is added to a primary air conditioning system, but this is not required in most cases.

In this type of system, the air is forced through a diffuser or into a volume of air that is already warmed.

The air then passes through an inlet system, where it can be recirculated back into the building.

Air diffusers generally take the form of a series of conical sections that diffuses air into a colder volume.

These forms are generally large and require more surface area than other types of air distribution, such as convection.

Air diffusers must be sized correctly to distribute the right amount of heat to a specific space without trapping heat, as they will be affected by an air space.

The smallest air diffusers can have a useful heating effect at room temperature, while larger diffusers are recommended for air conditioning purposes.

Common applications of air diffusers include: central heating and cooling systems, some bathrooms, aquariums, industrial applications and single-family homes.

Convection is similar to diffusion in terms of function, but is used to circulate warm air into a cooler space, requiring a smaller surface area.

Convection occurs when warm air rises due to a difference in temperature between the areas of the convection.

The air first flows into an inlet system, where the air is warmed and then recirculated.

Convection air blowers are mounted on external doors or windows, which guide the air to a smaller internal area.
Convection is found in most indoor HVAC systems and typically has a very strong heat transfer rate.

Convection air systems are most commonly used for cooking, air conditioning, and individual room heating and cooling.

However, a large part of convection systems’ usefulness is due to the heat transfer rate they are able to achieve.

The smaller the volume of air, the higher the heat transfer rate of convection.

One of the few variables in convection air systems is that it is often less effective at eliminating humidity than diffusion air.

Both diffusion and convection air systems have limitations in that they cannot be heated (if used with a condensing system), nor chilled.

Air distribution systems are most often installed on the outside of buildings.

These systems are typically arranged into zones, which prevent unwanted air loss into the external environment.

The outside zone is the largest zone and usually corresponds to a main air source, such as a large chimney, or a set of chimneys.

An air handler is typically used in this zone to direct air in the direction of an individual room.

Zone 1 is the first zone air distribution.

This zone consists of a plenum which the air passes through before being recirculated, and often directed into the ceiling rafters.

Zone 2, usually the smallest, is the smallest of the zone distribution systems.

This zone can be used to introduce fresh, cool air to rooms, similar to a convection system.

However, this air enters the room through a circulation fan or some other mechanism, instead of being pulled in from outside by an inlet.

This zone should only be used if it has large windows.

Zone 3 is the first zone that requires an HVAC system.

This zone is the air handler’s objective.

This zone is often the first air handler to provide air to an entire building.

The flow from this zone into the second zone is often referred to as chiller.

The movement of air through the floor, ceiling and walls of a room allows for a more constant temperature inside.

This zone consists of an air handler which serves to pull cool air in from outside, to control indoor air temperature.

The cool air usually comes in at a high pressure and is drawn into the system through a ductwork that branches out in every direction from the HVAC system.

The air in the ductwork moves through a series of converters that change the temperature.

After passing through the converters, it moves through an interior unit to warm the air before being sent to the rooms.

The temperature of the incoming cool air is regulated by an outdoor unit and the compressors in the system.

This zone usually incorporates ductwork, with service air, and a heat recovery unit.

This zone also contains the outdoor unit, which provides a source of warm air that is pulled into the system through the ductwork.

With the outside unit, the system is shut off and the temperature within the system is held constant.

If a building has a central air conditioning unit, the temperature inside is usually maintained by the outside unit.

This zone usually has air return ducts and sometimes air conditioning condensers.

This zone is often associated with exterior air handlers, or air blowers.

This zone can also include ductwork, and possibly heat recovery units.

This zone usually has a heat recovery unit, and will be responsible for a building’s heat pump system if it includes one.

A typical system has a heating element and a condensing coil inside the condensing coil.

The heating element causes the gas to expand and is heated by the unit.

This zone consists of one or more ductwork that extend to both sides of the building, into the attic and under the roof.

This zone typically has the heat recovery units.

Often this zone is called the "top of the building".

This zone can be part of a chiller, but it is not normally a chillers.

The term "zone" refers to the type of floor or room which is served by the ductwork.

Most of the distribution zones are built around floors, and commonly in the house or the equivalent, the zone is provided with an electrical cord going to the main electrical panel.

The electric bill is normally also sent to the central HVAC system.

The zone can be served from many sources.

Typically an air handler or chillers serve this zone, or air conditioning.

Other zone heating systems, or space heaters also serve this zone.

Inverters can serve this zone.

In a typical system, the cooling, heating, and/or ventilation of air is accomplished using a single (or a few) ducts.

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Heat Load Calculation Guide 1

Heat Load Calculation Guide 2

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How to Calculate External Static Pressure (ESP) with worked Example

How to Calculate Area of Sand Trap Louver with worked Example and detailed steps

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