HVAC SYSTEMS
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| What is HVAC? |
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HVAC stands for heating, ventilation and air conditioning and refers to the all equipment, distribution system and workstations used either together or individually to provide fresh filtered air, heating, cooling and humidity control in a building.
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A facility can have combinations of heating and cooling means to supply the HVAC system. For heating a facility, a furnace or boiler, heat pump, rooftop unit, new technology such as infrared radiation, or electric heater could be employed. Most usual cooling sources employed includes rooftop units, chillers, heat pumps, air conditioner or some sort of off-peak cooling system.
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| What is the Basic HVAC Design? |
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HVAC systems can differ in design and complication. The following description and diagram represent a simple HVAC system. Alterations can be put in to the basic system to reach the required HVAC operation.
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Air is taken through an outdoor air intake that is usually a louvered opening on the top or side of the building. Atmospheric pressure pushes the air through a damper, which regulates the amount of outdoor air (OA) taken in by the system. At this point, already conditioned return air (RA) from the system can be mixed with the outdoor air to form “mixed air.” The mixed air goes through a pre-filter where larger dust particles, insects, leaves, etc. are caught. A more efficient filter is usually present to address small particles. After the filters, the air enters a centrifugal fan. Once exiting the fan outlet, the air is under positive pressure and being pushed towards coils where the air is either heated or cooled, depending on the temperature of the air and the season. Under the coils lies a drain pan to collect any water condensing on the coils. If a humidifier or dehumidifier is needed it is usually incorporated into the cycle at this point. The air travels through ductwork where it reaches a distribution box and may travel through smaller ducts to supply the terminals, registers or diffusers into the workspace. Once the air reaches its destination, it is returned through an air register (usually through a louvered door that opens into a space above the ceiling tiles) in the form of return air that will become mixed air or exit the building.
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| Compression Heating and Cooling |
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The compression and the expansion of a gaseous fluid is the main natural principle used for transferring heat from the outside to the inside and vice versa (reversible system). |
| Heating: |
The fluid compression rises its temperature and calories can be extracted through an inside heat exchanger (heat pump - room heating).
The fluid is then expanded, and consequently cooled. The cooled fluid can be heated through an outside heat exchanger and compressed again
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| Cooling: |
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The same system can be reversed and used for air cooling.
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Air / Water
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Air / Air
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