40 terms

Unit 22 Quiz #2

Unit 22 quiz on Condensers #2
When a system with a water-cooled
condenser cycles off, the water regulating valve should
a. remain open during the off cycle
b. close, since the head pressure is lower
c. open all the way to remove any residual heat
d. re-calibrate itself to maintain the new lower head pressure
A normally operating water-cooled
condenser is operating with a 10° differential between water in and water out. If the amount of 85°F water going through the condenser is reduced, which of the following is a possible temperature of the water leaving the condenser?
a. 75°F
b. 0°F
c. 95°F
d. 105°F
If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much sub-cooling is the condenser operating
a. 30°F
b. 15°F
c. 100°F
d. 130°F
Which of the following condensers is
the most efficient?
a. forced draft air-cooled
b. induced draft air-cooled
c. water-cooled parallel flow
d. water-cooled counter flow
An air-cooled condenser that is
operating in a climate that has four distinct seasons must ____.
a. have some type of head pressure control
b. use a water regulating valve
c. have a multi-circuit evaporator
d. operate with zero degrees of sub-cooling
What can be used to maintain the head
pressure of a system with a water-cooled condenser?
a. fan cycling
b. dampers or louvers
c. water regulating valve
d. all of the above
Which of the following can be used to
maintain the head pressure of a system with an air-cooled condenser?
a. fan cycling
b. condenser flooding valve
c. dampers or louvers
d. all of the above
The shell and tube condenser is
cleaned ____.
a. with a brush after removing the end caps
b. only with chemicals
c. with compressed air
d. with a vacuum cleaner
If the water-flow is reduced, the
temperature difference across a condenser will ____.
a. increase
b. decrease
c. remain the same
d. correspond to the evaporator saturation temperature
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.
a. less than
b. greater than
c. the same as
d. slightly lower than
A water regulating valve helps to
maintain a system's head pressure by modulating the flow of refrigerant through the condenser.
Evaporative condensers operate more
efficiently in climates where the wet bulb temperature is a great deal lower than the dry bulb temperature.
The desired water flow through a
condenser connected to a recirculating water system is 3 gallons per minute, per ton of air conditioning.
If the spring pressure of a water
regulating valve is increased, the system head pressure will also
One large problem designer's face
when designing air-cooled refrigeration and air conditioning equipment is a changing ambient from the changing seasons.
High head pressures from low ambient
can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators.
Low suction pressures, iced coils, short-
cycling, and inefficient cooling can also result from low head pressures.
Hard starting may also occur in a low
ambient condition causing low head pressures.
If an air-cooled condenser's fan motor
stops running, the head pressure will
______and the amount of sub-cooling will ___.
ANSWER ; Increase,
An evaporative condenser uses _____ and ______ as the transfer medium for system heat.
The low form of plant life that grows in
condenser water is _____.
ANSWER : Algae
In a water-cooled condenser, the
leaving water temperature is normally _____°F, lower than the condensing temperature of the refrigerant.
ANSWER : 10 Degrees
In order for a flooded condenser type
head pressure control system to operate, a device called a _____ has to be added to the system because of the extra refrigerant.
ANSWER : Receiver
What is the condenser saturation
temperature if there is 20°F of sub-cooling and the outlet
temperature of the refrigerant is 90°F?
ANSWER : 110 degrees
In a tube-in-tube condenser, the
refrigerant flows in the outer tube and the water flows in the inner tube. Why?
ANSWER : Heat transfer
Describe the term "counter-flow" when
used to describe the flow through a tube-in-tube condenser.
ANSWER : Two fluids flowing in opposite directions.
What is meant by the term "blow down"?
ANSWER : A system in a cooling tower whereby some of the circulating water is bled off & replaced with fresh water to dilute the sediment in the sump.
Define "desuperheat."
ANSWER : Removing heat from the superheated hot refrigerant gas down to the condensing temperature
Define "sub-cooling."
ANSWER : The temperature of a liquid when it is cooled below its condensing temperature.
What would the symptom be if an
air-cooled condenser had two fans and one stopped running?
ANSWER :When a condenser has more than 1 fan,1 fan can be put in the lead & the other fan can be cycled off & on by Temperature.This helps prevent pressure swings
Define "heat reclaim."
ANSWER : Using heat from a condenser for purposes such as space & domestic water heating.
A normally operating water-cooled
condenser is operating with a 10° 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?
a. The outlet water flow will increase
b. The system head pressure will rise.
c. The water regulating valve will close.
d. Both a and b are correct.
Which of the following would allow a
system to operate more efficiently?
a. condenser that had refrigerant leaving with 10° of sub-cooling

b. condenser that had refrigerant leaving with 15° of sub-cooling
c. condenser that had refrigerant leaving as 100% vapor
d. condenser that had refrigerant leaving with 10°F of superheat
The refrigerant in a condenser in a
refrigeration system ____.
a. absorbs heat
b. gives up heat
c. changes to a vapor
d. is under lower pressure than the evaporator
The condenser in a refrigeration system
a. desuperheats the vapor from the compressor
b. condenses the vapor from the compressor
c. subcools the liquid refrigerant before it leaves the condenser
d. all of the above
Mineral deposits in the water portion of
a water-cooled condenser act as ____.
a. a conductor of heat
b. an insulator
c. a cleaning solution
d. They have no effect on the operation of the condenser.
The water circuit in shell and coil and
coil-type tube-in-a-tube condensers must be cleaned ____.
a. by removing the end caps
b. with a brush
c. chemically
d. by air pressure
In a water-cooled condenser, a
regulating valve is used to control the ____.
a. refrigerant flow through the pressure reducing device
b. refrigerant condensing temperature
c.suction pressure
d. water temperature
Control of the head pressure in an
air-cooled condenser is done by ____.
a. cycling the condenser fan
b. controlling dampers in the airstream through
the condenser
c. flooding the condenser with refrigerant
d. all of the above
Condensing temperatures in an
air-cooled condensing unit can be reduced by ____.
a. increasing the condensing surface area
b. increasing the cfm through the condenser
c. decreasing the temperature of the air entering the condenser
d. all of the above