Airconditioning and Ventilation Systems: Module 1, Lessons 1-3

These vocabulary flashcards cover the fundamental terminology, components, and system types of HVAC as presented in the lecture notes, including ASHRAE definitions and engineering classifications.

HVAC

An acronym standing for Heating, Ventilation, and Air Conditioning.

Air Conditioning (ASHRAE Definition)

The process of treating air so as to control simultaneously its temperature, humidity, cleanliness, and distribution to meet the requirements of a conditioned space.

Humidity

The amount of water vapor present in the air.

Atmosphere Composition

Primarily composed of Nitrogen (approximately $78\%$), Oxygen (approximately $21\%$), other gases (approximately $1\%$), and variable water vapor.

Absolute Humidity

The mass of water vapor present in a unit volume of moist air, expressed in $\text{kg/m}^3$ or $\text{g/m}^3$. It indicates actual moisture regardless of temperature.

Relative Humidity

The ratio (expressed as a percentage) of the actual amount of water vapor in the air to the maximum amount the air can hold at the same temperature.

Air Cleanliness

The removal of contaminants such as dust particles, pollen, smoke, microorganisms, and odors using filters or UV disinfection systems.

Ventilation

The process of supplying air to or removing air from a space for the purpose of controlling air contaminant levels, humidity, or temperature.

Compressor

The heart of the air-conditioning system that compresses low-pressure refrigerant vapor into high-pressure, high-temperature refrigerant vapor.

Condenser

The component, usually located outdoors, where heat is rejected from the refrigerant to the surrounding environment.

Expansion Device

A component that controls the flow of refrigerant and reduces its pressure before it enters the evaporator coil.

Evaporator

The component where cooling occurs as cold refrigerant inside the coil absorbs heat from warm indoor air.

Refrigerant

The working fluid that circulates through the system, absorbing heat at the evaporator and releasing it at the condenser.

Air Handling Unit (AHU)

A major component of centralized HVAC systems used to condition and circulate air; it may contain filters, coils, fans, dampers, and mixing boxes.

Fan Coil Unit (FCU)

A smaller air-handling device commonly used in chilled water systems containing a fan and a coil to produce local cooling.

Diffuser

A supply outlet, typically located in the ceiling, that distributes conditioned air into a room in a controlled pattern.

Register

An air terminal device similar to a grille but equipped with a damper for airflow adjustment.

Grille

A louvered or perforated covering for a duct opening, commonly used for return or exhaust air.

Damper

A device used to regulate or stop airflow in ducts or air openings, which can be manually or automatically adjusted.

Thermostat

A control component that senses room temperature and sends signals to start, stop, or adjust system operation.

Chillers

Centrally located machines that utilize the vapor compression loop to chill a continuous stream of water used as a cooling vehicle.

Boilers

Pressure vessels that burn fuel or use electrical resistance to heat water or generate high-pressure steam for heating.

Cooling Towers

Outdoor structures used with water-cooled chillers to reject heat by evaporating a small portion of the condenser water.

Unitary/Local Systems

Self-contained, factory-assembled systems designed to serve a single room or a small group of rooms, such as window AC units.

Variable Refrigerant Flow (VRF)

An engineered multi-split system that modulates the mass flow rate of refrigerant to multiple indoor units for precise temperature zoning.

Packaged Rooftop Unit (RTU)

A factory-assembled, heavy-duty self-contained unit mounted on a roof that connects directly to ductwork to serve large spaces.

All-Air Systems

Systems where the central AHU fully conditions the air and distributes it through ducts; no water or refrigerant pipes enter the occupied spaces.

Constant Air Volume (CAV)

An all-air system that delivers a fixed volumetric flow rate of air and adjusts temperature to match room loads.

Variable Air Volume (VAV)

An all-air system that maintains a constant supply air temperature but varies the volume of air delivered via localized damper boxes.

All-Water Systems

Systems that distribute chilled or hot water to local terminal heat exchangers (like FCUs) within the room, requiring no central air ducts for conditioning.

Air-Water Systems

A hybrid approach where water handles the primary sensible cooling/heating loads and a downsized air system handles ventilation and latent dehumidification.