HVAC Quiz Chapter 21,22,23, and 24
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?
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 subcooling is the condenser operating?
15°F
The household refrigerator fresh-food compartment typically ranges from ____.
28 to 40°F
A typical evaporator operating temperature in an air-conditioning system is ____.
40°F
High-temperature refrigeration applications will normally provide box temperatures of ____.
47 to 60°F
A typical superheat for an evaporator operating under normal conditions would be ____.
8 to 12°F
High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators
False
The hermetic reciprocating compressor motor is essentially made of the same materials as an open type compressor motor.
False
The scroll compressor is one type of reciprocating compressor.
False
____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant.
Superheat
If a thermostatic expansion valve's thermal bulb came loose from the suction line at the outlet of the evaporator, which of the following could result?
The bulb pressure would increase and the thermostatic expansion valve would open. Liquid refrigerant would flow back to the compressor. The superheat in the evaporator would decrease
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?
The outlet water temperature will be lower than expected. The system head pressure will rise.
A bolted together motor-compressor assembly is sometimes referred to as a semi-hermetic type.
True
A stamped plate evaporator usually does not use a fan to move air across it.
True
Because a scroll compressor's has fewer moving parts, it operates much quieter than other compressor designs and technologies.
True
If the spring pressure of a water regulating valve is increased, the system head pressure will also increase.
True
SEER is calculated based on the total amount of cooling (in BTU's) the system will provide over the entire season, divided by the total number Watt-Hours it will consume.
True
The rotary screw compressor uses an open motor instead of the hermetic design.
True
The shell of a hermetic type reciprocating compressor is generally considered to be on the low pressure side of the system.
True
Mineral deposits in the water portion of a water-cooled condenser act as ____.
an insulator
The ____ of the liquid refrigerant determines the coil operating temperature.
boiling temperature
Liquid entering the compression chamber of a reciprocating compressor can lead to ____.
both a and b
The purpose of an externally equalized thermostatic expansion valve is to ____.
compensate for excessive evaporator pressure drop
Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?
condenser flooding valve fan cycling dampers or louvers
If the application requires a coil design to operate below freezing, there must be provision for ____.
defrost
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
The ____ in a refrigeration system is responsible for absorbing heat into the system from whatever medium is to be cooled.
evaporator
The boiling temperature and its relationship to the system exist in the ____.
evaporator
A thermostatic expansion valve controls refrigerant flow to the evaporator based on ____.
evaporator suction line superheat
Balanced port TXVs are used to ____.
feed refrigerant at a normal rate with low condenser entering air temperatures
Evaporators that are operated full of liquid and are equipped with a device to keep the liquid refrigerant from passing to the compressor are known as ____.
flooded evaporators
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.
greater than
The cross liquid charge bulb at the TXV contains fluid that ____.
has different characteristics from the system fluid
An air-cooled condenser that is operating in a climate that has four distinct seasons must ____.
have some type of head pressure control
A refrigeration system designed for the storage of flowers or candy is considered a ____ type.
high temperature
When the load on the evaporator increases, the TXV ____.
increases the flow of refrigerant
Condensing temperatures in an air-cooled condensing unit can be reduced by ____.
increasing the condensing surface area increasing the cfm through the condenser decreasing the temperature of the air entering the condenser
The screw compressor is used primarily in ____.
large industrial refrigeration and air-conditioning systems
The primary function of an expansion device is to ____
lower the boiling point of the refrigerant far enough below the temperature of the load to get the needed heat transfer rate produce a reduction in the pressure on the liquid refrigerant regulate the flow of refrigerant into the evaporator
The household refrigerator fresh-food compartment is a good example of ____ refrigeration.
medium-temperature
The TXV sensing bulb is mounted ____.
on the suction line between the evaporator and the compressor
The process of removing heat from a place where it is not wanted and transferring that heat to a place where it makes little or no difference is known as ____.
refrigeration
The purpose of a capillary tube is to ____.
regulate the refrigerant flow into the evaporator lower the pressure of the liquid refrigerant lower the boiling point of the refrigerant
The refrigerant in a condenser in a refrigeration system ____.
rejects heat
Rotary compressors are used primarily in ____.
small commercial refrigeration units
Most of the heat energy in the suction vapor entering the compressor is ____.
superheated from the evaporator
The temperature of the compressed gas leaving the compressor can best be described as ____.
very warm
The clearance volume of a compressor cylinder is the ____.
volume of the space between the bottom of the valve plate and the top of the piston at the top of the stroke
What can be used to maintain the head pressure of a system with a water-cooled condenser?
water regulating valve
The shell-and-tube condenser is cleaned ____.
with a brush after removing the end caps
