MỚI
Cỡ chữ
bảng tính08. ACR-104 UNIT 22 EOU TEST
Total câu hỏi: 32
Worksheet time: 31mins
The refrigerant in a condenser in a refrigeration system ____.
absorbs heat
rejects heat
changes to a vapor
is under lower pressure than the evaporator
The condenser in a refrigeration system ____.
desuperheats the vapor from the compressor
condenses the vapor from the compressor
subcools the liquid refrigerant before it leaves the condenser
All of the above.
A normally operating water-cooled condenser is operating with a 10°F differential between water in and water out. If scale forms on the water tubes and the entering water is 85°F, which of the following is possible?
The outlet water temperature will be lower than expected.
The system head pressure will rise.
The water regulating valve will close.
Both a and b are correct.
Mineral deposits on the water side of a water-cooled condenser act as a(n) ____.
conductor of heat
insulator
cleaning solution
They have no effect on the operation of the condenser.
In a water-cooled condenser with dirty condenser tubes, the temperature difference between the refrigerant and the leaving water will be ____ when the tubes are clean.
less than
greater than
the same as
slightly lower than
The water circuit in shell-and-coil and tube-within-a-tube coil condensers must be cleaned ____.
by removing the end caps
with a brush
chemically
by air pressure
The shell-and-tube condenser is cleaned ____.
with a brush after removing the end caps
only with chemicals
with compressed air
with a vacuum cleaner
In a water-cooled condenser, a regulating valve is used to control the ____.
refrigerant flow through the pressure reducing device
refrigerant head pressure
suction pressure
water temperature
What can be used to maintain the head pressure of a system with a water-cooled condenser?
Fan cycling.
Dampers or louvers.
Water regulating valve.
All of the above.
The typical design temperature for the water entering a recirculating water system condenser is 85°F, and most systems have a ____ rise across the condenser.
1°F
5°F
10°F
15°F
If an R-12 refrigeration system has its air-cooled condensing unit on a roof with an ambient air temperature of 100°F and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating?
15°F
30°F
100°F
130°F
An air-cooled condenser that is operating in a climate that has four distinct seasons must ____.
have some type of head pressure control
use a water regulating valve
have a multi-circuit evaporator
operate with zero degrees of subcooling
Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?
Fan cycling.
Condenser flooding.
A water regulating valve helps to maintain a system's head pressure by modulating the flow of refrigerant through the condenser.
True
False
The desired water flow through a condenser connected to a recirculating water system is approximately 3 gallons per minute per ton of refrigeration.
True
False
When the evaporative condenser is used in cold climates, freeze protection must be provided in winter.
True
False
If the spring pressure of a water regulating valve is increased, the system head pressure will also increase.
True
False
One big problem designers face when designing air-cooled refrigeration and air-conditioning equipment is the changing ambient of the changing seasons.
True
False
High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn can starve evaporators.
True
False
Low suction pressures, iced coils, short cycling, and inefficient cooling, can also result from low head pressures.
True
False
Hard starting may also occur in a low ambient condition, causing low head pressures.
True
False
The heat in the vicinity of the gas has a tendency to cause any minerals in the water to deposit onto the tube surface.
In a recirculating water system condenser, the leaving water temperature is normally °F lower than the condensing temperature of the refrigerant.
An evaporative condenser uses air and ______ to desuperheat, condense, and subcool the refrigerant.
If an air-cooled condenser's fan motor stops running, the head pressure will .
In order for a flooded condenser type head pressure control system to operate, a device called a holds the extra refrigerant in warmer weather when the condenser doesn’t need to be flooded.
In a tube-within-a-tube condenser, the refrigerant flows in the outer tube and the water flows in the inner tube because:
it allows better heat exchange efficiency.
it prevents the refrigerant from freezing.
it reduces the pressure drop in the system.
it minimizes the risk of water contamination.
What is the construction of the tube-within-a-tube condensers?
A single tube with multiple layers
Two concentric tubes, one inside the other
A series of parallel tubes
A spiral tube design
What is the condenser saturation temperature if there is 20°F of subcooling and the outlet temperature of the refrigerant is 90°F?
70°F
80°F
110°F
100°F
What does "desuperheat" mean?
To increase the temperature of a vapor
To decrease the temperature of a vapor
To convert liquid to vapor
To maintain the temperature of a vapor
What is the definition of "subcooling"?
The process of cooling a liquid below its boiling point without it becoming a gas.
The process of heating a liquid above its boiling point without it becoming a gas.
The process of cooling a gas below its condensation point without it becoming a liquid.
The process of heating a gas above its condensation point without it becoming a liquid.
What would the symptom be if an air-cooled condenser had two fans and one stopped running?
increased head pressure
Increased cooling efficiency
No change in cooling efficiency
decreased head pressure
