Air Conditioning and Refrigeration Terms Flashcards

Flashcards defining key air conditioning, refrigeration, and HVAC technical terms based on the provided exam transcript.

Dry Bulb Temperature

The actual temperature of air measured by an ordinary thermometer, or the temperature of a gas or mixture of gases indicated by an accurate thermometer after correction for radiation.

Sensible Cooling

A process that involves cooling without changing the humidity ratio of the air, where the final temperature cannot be below the initial dew point temperature.

Direct Expansion

The term used to describe an evaporator with an expansion device other than a low-side float type.

Temperature-Humidity Index

The actual temperature and humidity of an air sample compared to air at standard conditions.

Evaporative Humidifier

A humidifier that provides moisture on a media surface through which air is forced, allowing the air to pick up moisture from the media as a vapor.

Wet-Bulb Temperature

A temperature measurement used to evaluate humidity in the air, obtained with a wet thermometer bulb to record the evaporation rate as an airstream passes over it.

Back Pressure

The pressure on the low-pressure side of a refrigeration system, also known as suction pressure

Accumulator

A storage tank located in the suction line of a compressor that allows small amounts of liquid refrigerant to boil away before entering the compressor.

Absorption air-conditioning chiller

A system using a salt substance, water, and heat to provide cooling for an air conditioning system.

Air Friction Chart

A chart used to determine proper round duct sizes.

Film Factor

The relationship between the medium giving up heat and the heat exchange surface (evaporator), related to the velocity of the medium passing over the evaporator.

Draft

Any localized feeling of coolness or warmth of any portion of the body due to both air movement and air temperature, with humidity considered constant.

Chiller Purge

A system that removes air or noncondensables from a low-pressure chiller.

Flash Gas

The pressure drop in an expansion device when some of the liquid passing through the valve changes quickly to a gas and cools the remaining liquid to the corresponding temperature.

Foaming

A term used to describe oil when it has liquid refrigerant boiling out of it.

Comfort Zone

An area on a psychrometric chart which shows conditions of temperature, humidity, and sometimes air movement in which most people feel comfortable.

Vapor Barrier

A thin film used in construction to keep moisture from migrating through building materials.

Vapor Lock

A condition where vapor is trapped in a liquid line and impedes liquid flow.

Adiabatic Saturation

A cooling process effective in hot, dry climates where a cooler, humid condition is produced and preferred over hot, dry conditions.

Grille

An air distribution component commonly used in high sidewall locations, featuring vertical and horizontal vanes.

Smart Recovery

The start-up of a building HVAC system earlier at reduced capacity to record a low demand metering for the billing period.

Register

A terminal device on an air-distribution system that directs air and includes a damper to adjust airflow.

Slinger ring

A ring attached to the blade tips of a condenser fan that throws condensate onto the condenser coil to evaporate it.

Receiver Drier

A component in a refrigeration system used for storing and drying refrigerant.

Purge

To remove or release fluid or noncondensable gases from a system.

Chill Factor

A factor or number combining temperature, humidity, and wind velocity used to compare relative conditions to a known condition.

Humidifier

A device used to add moisture to the air.

Thermostat

Sensors and devices that monitor and control the output of an HVAC system.

Hunting

The continuous opening and closing throttling of a valve that is searching for its set point.

Infiltration

Air that leaks into a structure through cracks, windows, doors, or other openings due to lower pressure inside the structure than outside.

Approach Temperature

The difference in temperature between the refrigerant and the leaving water in a chilled water system.

Pookie

An HVAC slang term for duct sealant.

Temperature Difference (TD)

The difference between the inlet temperature and outlet temperature of a heat exchanger (e.g., an evaporator with $75\,^\circ\text{F}$ air in and $55\,^\circ\text{F}$ air out has a $20\,^\circ\text{F}$ TD).

Evaporative Cooling

Cooling provided by drawing fresh air through water-soaked fiber mounted in a frame, cooling the air by evaporation to a temperature close to the wet-bulb temperature.

Temperature Swing

The temperature difference between the low and high temperatures of a controlled space.

Modulating Flow

Controlling fluid or air flow continuously between maximum flow and no flow.

Load Matching

The practice of continuously matching the capacity of the refrigeration or air-conditioning system with the heat load put on the evaporators.

Liquid Line

The tubing or piping extending from the condenser to the expansion device.

Latent Heat

Heat energy absorbed or rejected when a substance changes state without any change in temperature.

Hermetic System

An enclosed refrigeration system where the motor and compressor are sealed within the same system alongside the refrigerant.

Metering Device

The component located between the high-pressure liquid line and the evaporator that feeds liquid refrigerant into the evaporator.

Spread

The angle of divergence, both horizontal and vertical, of an airstream after it leaves an outlet.

Effective Temperature

Different combinations of temperature and humidity that provide the same comfort level.

Duct

A sealed channel used to convey air to and from the point of utilization in an HVAC system.

Diffuser

The terminal or end device in an air-distribution system that directs air in a specific direction using louvers.

Dew Point

The exact temperature at which moisture begins to form.

Chilled Water System

An air-conditioning system that circulates refrigerated water to pick up heat from the area to be cooled.

Atomizing Humidifier

A type of humidifier that discharges tiny water droplets into the air, which evaporate rapidly into the duct airstream or directly into the conditioned space.

Cooling Tower Approach

The temperature difference between the water leaving the cooling tower and the wet-bulb temperature of the entering air.

Drop

The vertical distance the air moves after it leaves an outlet and reaches the end of the blow.