432 Flashcards
if you increase the pressure of a liquid its ___ temperature will ___ meaning that it will boil at a higher temperature
saturation; increase
at a temperature of -30 degrees the enthalpy of the saturated liquid refrigerant is 3.5 btu/lb the enthalpy of evaporation is 87.4 btu/lb what is the enthalpy of the saturated vapor
90.9
in the following diagram of a refrigeration cycle the line between points ___ represents the amount of subcooling
2 & 3
a system must provide 8 tons of refrigeration what horsepower is needed for this system
10.3 hp
liquid refrigerant can be subcooled by transferring heat either to the atmosphere in the condenser or to the __ in the suction line heat exchanger
refrigerant vapor
an ideal refrigerant has which of the following characteristics
nonflammable
in the ASHRAE standard designations of refrigerants the
letter R is being replaced by the letters identifying the chemical structure
temperature glide occurs only in ___ refrigerants
blended
ASHRAE classifies refrigerants according to how hazardous they are. the most hazardous refrigerant are rated
B3
when handling out and storing refrigerants you must protect yourself by
avoiding any open flame
the ozone layer in the earths atmosphere is important because it
absorbs ultraviolet radiation from the sun
CFCs contribute to the greenhouse effect by
absorbing infrared radiation
in order to minimize the release of CFCs in to the atmosphere refrigeration service technicians must
recycle refrigerants on site if possible
a recycled refrigerant may be placed in
the system from which it was removed
during the installation of a new system the chance of future refrigeration leaks can be reduced by
installing a muffler in the compressor discharge line
to reduce the depletion of the ozone layer the US government has implemented laws requiring the
testing and certification of all technicians whose work can cause the release of harmful refrigerants
the EPAs final rule concerning the handling of refrigerants and refrigerant equipment requires
certifying the equipment used in recycling and reclaiming refrigerants
the compressor for an active recovery system is part of the ___ the compressor for a passive recovery system is part of the ___
recovery equipment; system being serviced
technicians who work on residential air conditioning systems must have at least ___ certification
Type II
which of the following documents is required by the EPA
certification activity report
which of the following is a contaminant that can be removed by a filter drier
acid
an absorption type desiccant holds water by means of an ___ action but an adsorption type desiccant holds water by means of an ___ action
chemical; mechanical
if you mount a filter drier in a vertical suction line the inlet should be located at the top so that ___ cannot become trapped inside
oil
when selecting a filter drier you need to base your selection in part on the
minimum particle size it can trap
when installing a filter drier in a refrigeration system you should
wear safety goggles
you can pinpoint leaks in a new refrigeration system by charging the system with __ and using a ___
nitrogen; soap solution
when preparing to use a gauge manifold in servicing a pressurized refrigeration system you connect its high side charging hose to the
compressor discharge service valve
to check the charge in a refrigeration system you can look at the ___ in the liquid line. if the charge is low you will probably see ___
sight glass; bubbles
in using the deep vacuum method of dehydrating a refrigeration system you lower the pressure to about ___ microns or less. with the vacuum pump turned off a gradual rise in pressure tells you the system is ___
1000; not dry
you can tell whether you have charged a refrigeration system with the correct amount of refrigerant by checking the
weight of the refrigerant used
the miscibility of a refrigerant oil is its ability to
mix with the refrigerants
oil that becomes mixed with the refrigerant in a system can cause which of the following problems
clogged desiccant
an oil separator is located between the __ and __ in order to keep oil out of the condenser and evaporator
compressor; condenser
moisture in a refrigeration system causes a variety of problems including
blockage in cold parts of the system
before you check the oil level in the sight glass on a refrigeration compressor you should stop the compressor for at least ___ . the compressor should be ___ while you check the oil level
ten minutes; stopped
