434 Flashcards
(25 cards)
The function of an evaporator is to ____ heat (from/to) the _____
remove: material being cooled
The capacity of an evaporator is affected by the
cleanliness of the evaporator
Basic evaporator configurations depend on whether they have one or more tubes and whether or not they have
Extended surface areas
Multiple-circuit evaporators have headers or distributors that direct refrigerant to each coil from ______ expansion valve(s)
One
A comfort cooler ______ the humidity of moist air by cooling the air to a temperature _______ the dew point
reduces, below
Unlike a dry-expansion evaporator, refrigerant in a flooded evaporator enters as ______ liquid and exits as ____ vapor
all, part
In a secondary-refrigeration system, the refrigerant removes heat from the material to be cooled. This refrigerant then transters heat to the ______ refrigerant. In the process the _____ refrigerant boils
secondary, primary
A eutectic solution is a brine in which the concentration of salt is precisely set to achieve the lowest possible
Freezing point
Which evaporator arrangement offers the greatest flexibility?
Two evaporators in parallel, each with its own expansion valve
The basic law(s) of thermodynamics that apply to refrigeration state that
heat flows from a warmer substance to a cooler substance
A cascade refrigeration system has more than one
compressor, evaporator, condenser, and refrigerant
The net refrigeration effect can be increased by _____ the refrigerant
Subcooling
Using a heat exchanger to lower the temperature in the liquid line and raise the temperature in the suction line has the advantage(s) of reducing
the amount of liquid refrigerant entering the compressor
The amount of oil entering an evaporator can be reduced by using a(n)
Oil separator
If the fluid being cooled by an evaporator circulates through the coil rather that moving slowly or not at all, the performance of the evaporator improves because of the
increased temperature difference across the wall of the evaporator
An evaporator can be defrosted by
reversing the flow of refrigerant
To remove rust, scale, and sludge from a shell-and-tube evaporator you should use a(n) ____ as necessary
Brush
A water coil can be winterized by draining out the water and
Leaving the coil dry for the winter
Frost buildup on an evaporator coil is increased by _____ airflow and _____ air
low, humid
Bent fins reduce the cooling capacity of an evaporator, because they _______.
reduce the area exposed to the air
The purpose of the metering device in a refrigeration system is to
control the flow of refrigerant into the evaporator
The operation of an AXV is controlled by the
pressure in the evaporator
In controlling the flow of refrigerant into a flooded evaporator, the float of a high-side float valve is located [at/on] the
high-pressure side of the valve port
If floodback occurs in a system using an AXV, a likely cause is
ice on the spring chamber above the diaphragm
