HVAC Fundamentals Quiz

Erasmus Mundus International Joint Master Degree Program (SMACCS)

• SMACCS is an Erasmus Mundus International Joint Master Degree.
• The program is jointly offered by Universidad del País Vasco, International Hellenic University, Heriot-Watt University, and UMONS.

HVAC II: Air Conditioning Systems

• This section covers high performance HVAC systems and focuses on air conditioning systems.
• Key personnel include PhD Álvaro Campos Celador, PhD Iker González Pino, and PhD Pello Larrinaga Alonso, all from the Department of Energetic Engineering at the University of the Basque Country.
• The course material is part of a Master's program in Smart Cities and Communities.

HVAC II: Air Conditioning Systems - Table of Contents

• 1. Introduction to air conditioning systems
• 2. Air Handling Units (AHU)
• 3. Air distribution systems
• 4. Terminal units for air conditioning systems
• 5. Condensing loops
• 6. Control of air conditioning systems

1. Introduction to air conditioning systems

• Air systems provide complete sensible and latent cooling, heating, and (de)humidification capacity in the air supply.
• Heating can be done by the same airstream or a separate heater.
• Two basic mechanisms for varying energy removed/supplied by the supply air:
  • Changing the supply air temperature (Constant Air Volume - CAV).
  • Changing the amount of supply air (Variable Air Volume - VAV).
• Initial considerations for all-air systems include considering loads that affect temperature differences, fan inefficiencies, and duct heat gain/loss.
• Humidity control in a space can also affect air quantity.
• Air temperature versus air quantity:
  • Designers have considerable flexibility in selecting supply air temperature and corresponding air quantity.
  • The relationship between temperature and air volume is approximately linear and inverse. Typical design is to deliver air as low as 13°C to achieve 24°C indoor temperature with modest latent heat loads and low air moisture.
  • Lower supply air temperatures might be required for spaces with considerable latent loads.
• Cold-air systems use a supply temperature as low as 7°C (smaller ducts and fans).
• Initial costs of lower airflow and temperature need to be weighed against possible distribution, condensation, air movement problems, and reduced odor/contaminant removal.
• Advantages of cold-air systems are lower humidity and reduced fan energy consumption.
• Understanding that all-air systems operate in multi-zone buildings, control is needed to adjust for different zones/conditions (exterior vs. interior, orientation of building).

2. Air Handling Units (AHU)

• AHU are used in large installations to maintain air conditions (temperature, humidity, air quality) within predefined ranges.
• AUH comprise a series of elements to process air before delivering it to designated condition zones.
• AHUs do not generate thermal energy but receive it from heating or cooling systems.
• AHU sections are: fans, cooling/heating coils, filters, humidity sections, mixing sections, and recovery systems.

3. Air distribution systems

• Ductwork should deliver heated or cooled air directly and efficiently to each condition area, with minimal noise and cost-effective design.
• Ductwork sizing may be done manually or using available software.
• Building structure and design features may require compromises in space for ductwork installation.
• Duct systems may use high-velocity components or a lower-velocity design, each with considerations and trade-offs.
• Variable flow in variable-flow systems may vary from design flow.
• In many applications, the space between ceilings and slabs is used as a return plenum.
• All-air systems have two categories:
  • Single-duct systems: Coils are in series in a common distribution system; there can be capacity-variable mechanism used for these systems.
  • Dual-duct systems: Coils may be in parallel or series-parallel and contain both cold and warm channels to modify the temperature to the needed condition.

4. Terminal units for air conditioning systems

• Air terminal units (ATUs) are placed between the primary air distribution system and the conditioned space.
• Two types:
  • Passive: Deliver and extract air without occupant discomfort and drafts.
  • Active (boxes): Control air quantity and temperature to maintain desired space conditions.
• In low velocity systems, air enters from the ductwork through grilles or diffusers (adjustable flow).
• In medium or high velocity systems, terminal units control air volume, reducing duct pressure.

5. Condensing loops

• Condensing loops are used in large buildings with limited space or high volume/roof ratios.
• They provide heat exchange in buildings.
• Systems may use air-cooling or water-cooling systems for heat rejection.
• The water-cooling systems can be either recirculating or once-through systems.
• Recirculation allows lower water usage in cooling.
• Cooling towers are a part of the recirculating systems.
• The performance of the cooling tower is related to the dry-bulb and wet-bulb temperature of the air.

6. Control of air conditioning systems

• Air distribution system controls should be automatic and simple.
• The use of thermostats, outdoor air, and return air dampers is used to manage the temperature based on the space conditions.
• Controls can involve different strategies/types of controls (e.g., DDC).
• Different types of controls are available dependent on the type of HVAC system:
  • Constant volume reheat
  • Variable airflow.
• Proper selection of dampers (outdoor, return, relief) is essential.

Test your knowledge on HVAC systems with this quiz. Explore key concepts including air handling units, energy mechanisms, and air distribution systems. Perfect for students and professionals alike in the HVAC field.