431 Flashcards
refrigeration is the process of __ the air in a defined space
lowering temperature of
the temperature of a material decreases if the material ___ and nothing else happens that would have the opposite effect
contacts a cooler material
the two kinds of air conditioning are
comfort and process
one of the physical states of matter is
gas
you can cause matter to change its physical state by
adding or removing heat
thermal energy that is directly related to the temperature of a material is called ___ heat
sensible
a temperature of 45 degrees is about the same as ___ Celsius
7
heat can be transferred from one place to another by the process of
conduction
the latent heat of vaporization of a substance is the amount of heat the substance absorbs as it
evaporates
a refrigeration system has been turned off for several days. it contains both liquid refrigerant and vapor. suddenly a line containing the refrigerant breaks. what happens inside the systems
the liquid refrigerant boils
from the compressor refrigerant flows to the
condenser
the graph below is the pressure temperature chart for a refrigerant. point ___ represents a condition of superheating
1
compared to a dry bulb expansion evaporator a flooded evaporator of the same size
is more efficient
the purpose of a cooling medium is to
remove heat from compressed refrigerant vapor
an automatic expansion valve is a metering device that maintains a constant pressure in the
evaporator
the properties of air that are important in psychometrics include
enthalpy
in a sling psychrometer the wet bulb temperature is usually lower than the dry bulb. if the difference is very small you know that the air is quite
humid
air that is saturated is air that is at the
dewpoint temperature
relative humidity changes if the ___ changes but the specific humidity does not
dry bulb temperature
to calculate the enthalpy of a sample of air you must include
latent heat of the water vapor
in order to remove the moisture that enters a refrigeration system during repair you must evacuate the system by using a ___ to make all the moisture vaporize
vacuum pump
one useful method of detecting leaks in a refrigeration system involves using an __ leak
electronic
relative humidity can be measured directly with an
hygrometer
which of the fallowing is a correct match between an electrical value and the instrument used to measure it
resistance; ohmmeter
in the list below identify the line that correctly matches on of the classes of work area hazard to an example of that class of hazard
chemical; container of refrigerant
