Unit 22 Quiz #2
An evaporative condenser uses _____ and ______ as the transfer medium for system heat.
ANSWER : Air, Water
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 ANSWER :B
In a water-cooled condenser, the leaving water temperature is normally _____°F, lower than the condensing temperature of the refrigerant.
ANSWER : 10 Degrees
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
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.
The low form of plant life that grows in condenser water is _____.
ANSWER : Algae
A water regulating valve helps to maintain a system's head pressure by modulating the flow of refrigerant through the condenser.
ANSWER : FALSE
High head pressures from low ambient can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators.
ANSWER : FALSE
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
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
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.
Evaporative condensers operate more efficiently in climates where the wet bulb temperature is a great deal lower than the dry bulb temperature.
ANSWER : True
Hard starting may also occur in a low ambient condition causing low head pressures.
ANSWER : True
If the spring pressure of a water regulating valve is increased, the system head pressure will also increase.
ANSWER : True
Low suction pressures, iced coils, short- cycling, and inefficient cooling can also result from low head pressures.
ANSWER : True
One large problem designer's face when designing air-cooled refrigeration and air conditioning equipment is a changing ambient from the changing seasons.
ANSWER : True
The desired water flow through a condenser connected to a recirculating water system is 3 gallons per minute, per ton of air conditioning.
ANSWER : True
Describe the term "counter-flow" when used to describe the flow through a tube-in-tube condenser.
ANSWER : Two fluids flowing in opposite directions.
Define "heat reclaim."
ANSWER : Using heat from a condenser for purposes such as space & domestic water heating.
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
If an air-cooled condenser's fan motor stops running, the head pressure will ______and the amount of sub-cooling will ___.
ANSWER ; Increase, Decrease
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 ANSWER : B
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 ANSWER : D
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. ANSWER : D
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. ANSWER :B
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 ANSWER : B
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 ANSWER :C
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 ANSWER : B
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 ANSWER : A
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 ANSWER : D
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 ANSWER : B
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 ANSWER : C
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 ANSWER : D
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 ANSWER : A
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 ANSWER : A
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 ANSWER : D
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 ANSWER : B
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 ANSWER : B
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 ANSWER : A
