Hvac eccellance Flashcards
Heat that causes a change in the temperature of a substance is called
Sensible heat
Heat added to a substance without a rise in temperature (ex: liquid refrigerant to gas) this process is called
Latent heat of vaporization
Heat added to a refrigerant in a vapor state after the evaporation process is called
Super heat
A scroll compressor moves refrigerant by the means of
Involutes spiral
The movement of heat by the way of fluid (or air) is called
Convection
The movement of heat through a solid object is called
Conduction
The standard unit for measuring for measuring the quantity of heat in a substance is
The british thermal unit (btu)
A refrigerant gives heat when
It condenses
Why must refrigerant in the suction line be slightly warmer than the saturation temperature
To prevent liquid slugging of the compressor
The state of the refrigerant in the suction line should be
Low pressure/low temperature vapor
The state of the refrigerant entering the condenser is
Low pressure/low temperature vapor
What is the function of the evaporator
Transfers heat from the refrigerated space to the refrigerant
Which of the following is not a thermodynamic property of refrigerant
Flammability
The sequential order of steps in the evaporator compressor are
Compression
Condensation
Expansion
Vaporization
If a 30lb cylinder if reclaim R-410a refrigerant has been stored overnight at 70F, the pressure in the cylinder should be
201 psig
Fan airflow pressure are usually measured in
Inches of water column (WC)
Zero psia (pound per square inch absolute) is
Pressure which cannot be further reduced
Zero psig (pound per square inch gauges) is
Same as atmospheric pressure
The temperature at which a moisture will start to condense from the air is called
Dew point
A compound pressure gauges measure
Pressure and vacuum
A mechanical shaft seal is necessary on a
Hermetic rotatory compressor
Liquid slugging is
Liquid refrigerant in the compressor clearance space
The clearance space in a reciprocating compressor has an effect on
Compressor capacity
Which of the following types of air conditioning compressors is most energy efficient
Scroll
Which of the following represent the right order for the function of a condenser
De-superheats
Condenses
Sub-cools
Refrigerant R-134a vapor enters the condenser at 124 psig, 100F it leaves as liquid from the condenser subcools 20F and the pressure will be approximately
87psig
