HVAC SYSTEMS
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| Production of Heat and Cold by Absorption |
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The absorption unit is based on phisico-chemical ability of a fluid to absorb and evaporate another fluid according the thermodynamic conditions. The global effect results in a heat transfer from the indoor space to the outdoor space, or vice versa (reversible system). |
The absorption systems can be single-effect or double-effect systems for a higher efficiency.
The energy required for operating the system is provided by a burner (usually a gas burner).
Typically, for one energy unit consumed by the burner, 3 to 4 energy units can be transferred from the outside to the inside or vice versa.
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| Single-Effect Absorption |
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Double-Effect Absorption
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| Function, Design Fundamentals of HVAC Systems |
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HVAC systems are of great importance to architectural design efforts for four main reasons. First, these systems often require substantial floor space and/or building volume for equipment and distribution elements that must be accommodated during the design process. Second, HVAC systems constitute a major budget item for numerous common building types. Third, the success or failure of thermal comfort efforts is usually directly related to the success or failure of a building’s HVAC systems (when passive systems are not used) -- even though the HVAC systems should be viewed as part of the larger architectural system. Last, but not least, maintaining appropriate thermal conditions through HVAC system operation is a major driver of building energy consumption. Figure 2 provides a breakdown of energy uses for typical residences and commercial buildings in both hot and cold climates. |
| Function: |
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HVAC system offers sufficient indoor air quality by: conditioning the air in the occupied areas of a building with the intention of providing the comfort to its occupants; diluting and removing contaminants from indoor air through ventilation; and providing proper building pressurization.
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| Design: |
While there are many different HVAC system designs and operational approaches to achieving proper system functionality, and every building is unique in its design and operation, HVAC systems generally share a few basic design elements (figure 1):
• Outside air intake
• Air handling unit—a system of fans, heating and cooling coils, air-flow control dampers, air filters, etc.
• Air distribution system
• Air exhaust system.17
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Function Of Sample HVAC System
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In general, outside (“supply”) air is drawn into a building’s HVAC system through the air intake by the air handling unit (AHU). Once in the system, supply air is filtered to remove particulate matter (mold, allergens, dust), heated or cooled, and then circulated throughout the building via the air distribution system, which is typically a system of supply ducts and registers.
In many buildings, the air distribution system also includes a return air system so that conditioned supply air is returned to the AHU (“return air”) where it is mixed with supply air, re-filtered, re-conditioned, and re-circulated throughout the building.
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