HVAC Flashcards
_____ the simultaneous control of the temperature, humidity, motion and purity of the air in a confined space.
air-conditioning
What are the 4 functions or elements of air-conditioning?
- cooling and de-humidifying of air
- heating or humidifying of air
- cleaning of air or filtration
- circulation of air
What are the 4 air-conditioning standards?
- cooling and de-humidifying
- heating and humidifying
- air motion
- air supply
______ for summer cooling, temperatures of 68 deg to 74 deg F and 50% relative humidity are a frequent design average.
cooling and de-humidifying
For summer cooling, temperature of __ to ____ deg F and 50% relative humidity.
68 to 74
_____ for winter cooling, temperatures of 70 deg to 75 deg F and relative humidity of 30% to 35% are found most satisfactory.
heating and humidifying
For winter cooling, temperatures of ____ to ____ deg F and relative humidity of 30% to 35%.
70 to 75
_____ air velocity should average 4.57 to 7.6 meters per min measured 36” above the floor.
air motion
For air supply, a 5 cuft to 7-1/2 cuft of air per minute per person (5-71/2 cuft/min/pers). In rooms where ______
smoking is not allowed
For air supply, a 25 cuft to 40 cuft of air per minute per person allowed in rooms where _____.
smoking is permitted
What are the 4 methods of cooling and de-humidifying?
- passing the air through a spray of cold water
- passing the air through coils containing cold water
- passing the air through coils containing the refrigerant itself; in this case the coils are called “direct expansion” coils
- passing the air through a combination of sprays and coils
_____ is a gas at normal temperature and pressure. It is first subjected to high pressure in a compressor which raises its boiling point and temperature.
Freon
____ is a refrigerant used for cooling.
Freon
______ is based upon the alternate liquefying and evaporating of a volatile liquid with a low boiling point usually Freon 12 (Dichlorodiflouromethane) or Freon 11 (Trichloromonoflouromethane) during which processes it respectively gives off and takes in heat.
mechanical refrigeration
What are the 6 desirable properties of Freon?
- high heat of vaporization
- moderate pressure change for low to high temperature range
- non-toxic
- incombustible
- non-explosive
- non-corrosive
What are the 3 types of air-conditioning systems?
- central systems
- split type air conditioning system
- window type air conditioning system
What are the 3 parts of the refrigeration plant?
- compressors
- condensers
- evaporators
What are the 2 types of compressors?
- piston type or reciprocating compressors
- centrifugal compressors
_____ for tonnages up to 100 tons
piston type ot reciprocating compressors
_____ are quieter, have fewer vibration problems, require less maintenance and with better operating control.
centrifugal compressors
What are the 2 types of condensers?
- air-cooled condensers
- water- cooled condensers
_____ are used in unit and packaged-type air- conditioners up to 3 tons refrigeration.
air-cooled condensers
What are the 3 types of water-cooled condensers?
- double-piped condensers
- shell and tube condensers
- evaporative condenser
What are the 2 types of evaporators?
- shell and tube heat exchanger
- direct expansion coils (coils containing the refrigerant itself)
_____ is similar in operation to the shell and tube condenser.
shell and tube heat exchanger
____the refrigerant is expanded into a shell enclosing the tube through which the water flows.
shell and tube heat exchanger
______ may either be installed in the spray chamber so that the water sprayed into the air comes into contact with the cooling coils or the air itself comes into direct contact with the cooling coils, as in the window type unit.
direct expansion coils
What are the 2 cooling and de-humidifying equipments?
- water sprays
- cooling coils
What are the 2 heating and humidifying equipments?
- tempering coils
- water heaters
____ contains steam and are used to heating the air ie., preheaters and reheaters.
tempering coils
_____ is used for heating the water which will be used in the spray chamber to add heat and humidity to the air.
water heaters
What are the 4 types of filters?
- dry filters
- viscous filters
- water filters
- eliminator plates
_____ consist of wire frames enclosing felt, cotton or sponge through which the air is screened.
dry filters
_____ consist of metal deflecting plates or screens coated with viscous oil.
viscous filters
_____ consist of corrugated galvanized iron sheets placed 1-1/8” apart which deflect the air flow about 30 deg catching the wet dust on the surfaces.
eliminator plates
What are the 3 air distribution equipment?
- ducts
- fans
- air outlets
_____ are usually of galvanized sheet metal, or aluminum sheets, usually rectangular in section, depending on the aspect ratio*, although circular ducts are also used for high velocity systems.
ducts
Aspect Ratio of the long side to short side; not to exceed 5:1 although ______ is preferred.
4 or 3:1
What are the 2 types of fans?
- centrifugal fans (radial fans)
- propeller or axial fans
____ are intended for moving air at comparatively high pressures and are commonly used in duct systems.
centrifugal fans (radial fans)
_____ are commonly used for wall exhausts
propeller or axial fans
_____ are madde for two locations: wall and ceiling.
air outlets