Unit 1 hvac and refrig

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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.


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