Unit 1 hvac and refrig
Comfort is typically attained at a normal cooling and heating temperatures with a relative humidity of about ___
50%
2. At what temperature does the body feel comfortable?
72°F
Air in buildings must be ___ to provide occupant comfort.
circulated continuously
Total comfort systems always include gently circulating air that is ___ and ___
clean and fresh
High humidity levels indicates?
damp air that contains a significant amount of moisture
Fresh air intake fans are used to draw fresh outdoor air into a building to ?
dilute contaminants in the indoor air.
Low humidity level indicates ?
dry air that contains little moisture
Supply air ___ and ___ are used to distribute air to building spaces
duct work and registers
return air __ and ___ are used to move air from building spaces back to the fan.
ductwork and grills
Humidity level is controlled by ?
humidifiers and dehumidifiers.
Heating and air conditioning equipment is used to?
maintain the temperature in building spaces.
Air-conditioners use either the ___ refrigeration process or ___ refrigeration process
mechanical compression or the absorption
What system has a high-pressure side that discharges heated air and a low-pressure side that discharges cooled air.
mechanical compression refrigeration system
Heating, ventilating, and air conditioning (HVAC) systems are designed to provide comfort using?
mechanical, pneumatic, electrical, electronic, and chemical components and equipment.
Air circulation is important because it helps cool the body by causing __ to ___
perspiration to evaporate
Probably the most important factor influencing indoor air quality is the presence of ___
pollutant sources
Return air ductwork and grills are ___ and ___ for efficient their collection
sized and located
Supply air ductwork is ___ and ___ for efficient air distribution
sized and located
When air is improperly circulated?.
temperature stratification occurs
Define Relative humidity
the amount of moisture in air compared to the amount of moisture the air would hold at the same temperature when the air is saturated, or full of moisture.
Define indoor air quality (IAQ)
the condition of indoor air as it relates to contaminant levels and air properties that affect the health and comfort of building occupants
Define condensation
the formation of liquid as moisture or other vapor cools below its dewpoint
Define Air circulation
the movement of air through distribution systems and building spaces.
Define ventilation
the process of reducing air pollution by introducing a enough fresh outdoor air into a building to dilute indoor pollutants.
Define Air filtration
the process of removing particles and contaminants, such as gas and orders, from the air that circulates through air distribution systems
Define Dewpoint
the temperature below which moisture begins to condense
A ___ is the amount of heat required to melt one ton of ice (2000lbs) over 24hrs.
ton of cooling
Air conditioning equipment is rated in BTU per hour or ___
tons of cooling
___ in building spaces is provided by warm air from healing equipment or cool air from air conditioning equipment.
Temperature control
Define physiological function
The natural physical and chemical function of an organism
Define sick-building syndrome
an illness that can be traced to a building space but not to a specific cause.
define building-related illness
an illness that is traced to a building space and attributed to a definite cause.
___ in buildings must be clean and include both return air that is recirculated and fresh air that is used for ventilation
Circulated air
The amount of moisture, or water vapor, in the air.
Humidity
___ affects comfort because it determines how slowly or rapidly perspiration evaporates from the body.
Humidity
the process of removing particles and contaminants, such as gases and odors, from air that circulates through air distribution systems is called
Air filtration
the speed air moves from one point to another through ductwork, the register, or a grill and is measured in feet per minute (fpm)
Air velocity
1 ton of cooling equals?
12,000 BTUs per hour or 288,000 BTUs per 24 hours (12,000x24= 288,000)
One ton of cooling equals?
12000 btu/hr or 288000 btu/24 hr
For maximum comfort, temperature control equipment is typically set to maintain air temperatures in buildings within ___ or ___ of the temperature necessary for comfort
1°F or 2°F
Air velocity of __ in building spaces is considered ideal for comfort.
40 feet per minute (fpm)
When the air temperature varies above ___ or below ___, the party begins to feel uncomfortable you warm or uncomfortably cool
76°F or 68°F
What is the mechanical compression refrigeration process
A compressor increases the pressure and temperature of a refrigerant so the refrigerant can reject heat to the condensing medium.
What system produces the refrigeration effect when one chemical is absorbed by another and heat is then removed.
Absorption refrigeration systems
___ removes the heat gained into the space in hot weather, providing a cooler more comfortable indoor space.
Air conditioning equipment
What is the absorption refrigeration process
And absorbent controls the pressure and temperature of a refrigerant
___ is the quantity of heat required to change the temperature of 1 pound of water 1°F
British thermal unit (btu)
air conditioning equipment is rated in?
Btu per hour or ton of cooling
The condition that occurs when a person can sense a difference between themselves and the surrounding air
Discomfort
What are the four strategies to control pollutants?
Elimination, source control, dilution, and preventive maintenance
HVAC system ___ and ___ are selected based on Ability to control the temperature in buildings
Equipment and components
HVAC system components include?
Fans, compressors, valves, dampers, actuators, fuels , refrigerant, and controls.
___ and ___ systems to remove moisture from the air as the air is cold by the evaporator.
HVAC and refrigeration
___ supplies the proper amount of heat and cool weather to offset heat loss from a building.
Heating equipment
___ lowers the evaporation rate
Higher relative humidity
Three primary reasons for poor indoor air quality (IAQ) in building spaces
Indoor air pollution sources; poorly designed, maintain, or operated ventilation systems; and using the building in a way that was not anticipated or poorly planned for when the building was designed or renovated
the condition of indoor air as it relates to contaminant levels and air properties that affect the health and comfort of building occupants is called?
Indoor air quality (IAQ)
___ raises the evaporator rate.
Lower relative humidity
Humidity is always ___ in air
Present
Describe the five factors that affect comfort?
Proper temperature, humidity , circulation, filtration, and ventilation
air that is not circulating, typically contains an excess of impurities such as carbon dioxide, and lacks sufficient levels of oxygen required to provide comfort.
Stagnant air
Define ton of cooling?
The amount of heat required to melt one ton of ice.
Define comfort?
The condition that occurs when a person cannot sense a difference between themselves and the surrounding air.
Define evaporation
The process that occurs when a liquid changes to a vapor by absorbing heat.
Define British thermal unit (btu)
The quantity of heat required to change the temperature of 1 lb of water 1°f
Define temperature Stratification
The variation of air temperature in the building space that occurs when warm air rises to the ceiling and cold air drops to the floor. Also causes discomfort
What is AshRae 62
Ventilation for acceptable indoor air quality, is a standard that specifies ventilation rates based on chemical, physical, and biological contaminants.
Define humidifier
a device that adds moisture to air, causing water to evaporate into the air.
Define dehumidifier
a device that removes moisture from air by causing the moisture to condense or be trapped.
Define makeup air
air that is used to replace air that is discharged as exhaust.