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Describe the construction of the tube-within-a-tube condensers .

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The tube-within-a-tube is manufactured by slipping one pipe inside another and sealing the ends in such a manner that the outer tube becomes one container and the inner tube becomes another container. The two pipes are then formed into a coil to save space .

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.


A) 1°F
B) 5°F
C) 10°F
D) 15°F

E) B) and D)
F) All of the above

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If the spring pressure of a water regulating valve is increased, the system head pressure will also increase.

A) True
B) False

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Hard starting may also occur in a low ambient condition, causing low head pressures .

A) True
B) False

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The heat in the vicinity of the ____________________ gas has a tendency to cause any minerals in the water to deposit onto the tube surface.

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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

E) None of the above
F) A) and B)

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A

In a water-cooled condenser, a regulating valve is used to control the ____.


A) refrigerant flow through the pressure reducing device
B) refrigerant head pressure
C) suction pressure
D) water temperature

E) C) and D)
F) None of the above

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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 ?


A) 15°F
B) 30°F
C) 100°F
D) 130°F

E) B) and D)
F) A) and C)

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When the evaporative condenser is used in cold climates, freeze protection must be provided in winter .

A) True
B) False

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The refrigerant in a condenser in a refrigeration system ____.


A) absorbs heat
B) rejects heat
C) changes to a vapor
D) is under lower pressure than the evaporator

E) A) and B)
F) All of the above

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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.
C) Dampers.
D) All of the above.

E) A) and B)
F) A) and C)

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High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn can starve evaporators .

A) True
B) False

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In a recirculating water system condenser, the leaving water temperature is normally ____________________°F lower than the condensing temperature of the refrigerant .

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A water regulating valve helps to maintain a system's head pressure by modulating the flow of refrigerant through the condenser.

A) True
B) False

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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.

E) C) and D)
F) B) and D)

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In order for a flooded condenser type head pressure control system to operate, a device called a(n) ____________________ holds the extra refrigerant in warmer weather when the condenser doesn't need to be flooded .

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The water circuit in shell-and-coil and tube-within-a-tube coil condensers must be cleaned ____.


A) by removing the end caps
B) with a brush
C) chemically
D) by air pressure

E) C) and D)
F) B) and C)

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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 ?


A) The outlet water temperature will be lower than expected.
B) The system head pressure will rise.
C) The water regulating valve will close.
D) Both a and b are correct.

E) A) and B)
F) None of the above

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Low suction pressures, iced coils, short cycling, and inefficient cooling, can also result from low head pressures .

A) True
B) False

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True

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

E) B) and C)
F) A) and D)

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