ACR 132 Final

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If the wet-bulb and dry-bulb temperature are both 80^F, what is the humidity?

100%

What is the relative humidity if the dry bulb temperature is 100^F and the wetbulb temperature is 65^F?

13%

If the dry-bulb temperature is 93^F and the wet bulb temperature is 60^F, what is the specific volume of the air

14.0 ft3/lb

pure water boils at a temperature of 212'F at which of the following standard conditions ?

14.967 PSI

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

15^F

if 22 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 24 lb. 12 oz. before any is added, what will be the supply cylinder weight after the system has been charged?

23 lb 6 oz (NOT an answer choice, write in)

if 30 oz. of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 26 lb. 4 oz. before any is added. what will the supply cylinder weigh after the system has been charged?

24 lb 6 oz

If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?

25 psig

A ton of refrigeration is equal to

288,000 Btu/24 hr

The standard atmospheric pressure at sea level is _____

29.92" Hg

One watt of electrical energy is equal to

3.413 Btu

A typical evaporator operating temperature in an air-conditioning system is

40^ F

What is the dew-point temperature if the wet-bulb temperature is 65^F and the dry-bulb temperature is 100^F?

40^F

The density of water is

62.3 lb/ft3

The factory charge in a split system, using R-22, shows 6 lb. 8 oz. in the outdoor condensing unit and 2 oz. in the evaporator. The 3/8" liquid line contains 0.48 oz. per foot and the 7/8" suction line contains 0.10 oz. per foot. The refrigerant lines are 30' long. What is the correct refrigerant charge for this system?

7 lb 11 oz

A typical superheat for an evaporator operating under normal conditions would be

8 to 12^F

Reciprocating compressors have _____

A piston and a cylinder

When charging a refrigeration system with a near-azeotropic mixture, what must be done to prevent liquid from entering the system?

Charge as a liquid through the low side using a restrictor

The _____ are used to change the vapor to a liquid and the liquid form back into a vapor the refrigeration cycle.

Condenser and evaporator

As heat is applied to a closed container containing a gas, the pressure inside the container will decrease

FALSE

Both sensible heat and latent heat transfers can be read with a thermometer.

FALSE

If a cylinder of R-22 is moved from a 100^F truck body into an 80^F shop, the quantity of liquid refrigerant in the cylinder will remain the same.

FALSE

Temperature difference does not affect heat transfer rate

FALSE

The all-aluminum coil has a higher heat transfer rate than the standard copper tube-aluminum fin coil.

FALSE

The only location where the refrigerant vapor is superheated is in the evaporator

FALSE

Vapor is more dense than liquid and as the liquid refrgerant boils, it has a tendency to sink.

FALSE

On a package air conditioning system, which refrigerant lines must be field installed?

NO lines need to be installed

Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure?

R-502

A dirty condenser coil can lead to

Reduced efficiency

A manufacturer's charging chart may be used when available to determining the correct charge for a system.

TRUE

An expansion valve is the pressure reducing device that controls the flow of liquid refrigerant into the evaporator.

TRUE

Equipment will perform at it's best efficiency when running at full load.

TRUE

Heat is a form of energy because of the motion of molecules

TRUE

If a residential split air conditioning system has a compressor equipped with a start capacitor and relay, it is probably using a thermostatic expansion valve as a metering device.

TRUE

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

TRUE

One good feature of an electronic charging scale is that it counts upward as refrigerant is removed, to tell the technician how much refrigerant was used.

TRUE

The refrigeration evaporator is a component that absorbs head from the conditioned space into the refrigeration system

TRUE

To check the performance of a dry-type evaporator, the service technician would first make sure the refrigerant coil is operating with enough liquid inside.

TRUE

What happens when room temperature soda is poured into a glass of ice?

The ice melts because it is absorbing heat from the soda.

Temperature can be thought of as ______

a description of the level of heat

Charging a refrigeration system refers to____

adding refrigerant to a system

Comfort can be described as the gentle balance between _____.

air cleanliness, air movement, temperature, and humidity

A vapor material exerts a pressure or force

all directions

Condensing temperature in an air-cooled condensing unit can be reduced by

all of the above

Ice melts in iceboxes because

all of the above

The primary function of an expansion device is to

all of the above

The purpose of a capillary tube is to

all of the above

Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?

all of the above

a graduated cylinder charging device is a device that _____

all of the above

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?

all of the above are correct

High temperature refrigeration is that produced by ____

an air-conditioning system

Infiltration is the term used when referring to the air entering a structure

around doors and windows

The _____ of the liquid refrigerant determins the coil operating temperature.

boiling temperature

Liquid entering the compression chamber of a reciprocating compressor can lead to ____.

both a and b

When charging a system with vapor refrigerant from a refrigerant cylinder, the cylinder will become ______

cold

The purpose of an externally equalized thermostatic expansion valve is to___.

compensate for the excessive evaporator pressure drop

A popular material combination used in air conditioning evaporators and condensers is

copper tube-aluminum fin

If the temperature remains constant and the volume that a gas occupies increases, the pressure will

decrease

If the application requires a coil design to operate below freezing, there must be provision for

defrost

In rotary type motor-compressor assemblies, the motor is cooled by _____.

discharge gas from the compressor

A direct expansion-type evaporator is also called a

dry-type evaporator

.Of the heat produced in the human body, which is by perspiration?

evaporation

The ____ in a refrigeration system is responsible for absorbing head 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

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

high efficiency condensers

have more surface area than standard condensers

The total heat content of infiltrated air of the same dry-bulb temperature may vary from one part of the country to another because of difference in _____.

humidity

If a critically charged refrigeration system is over charged, which of the following is a likely result?

increased operating pressures

When the load on the evaporator increases, the TXV

increases the flow of refrigerant

On a split air conditioning system with a remote condensing unit, which refrigerant lines must be field installed?

liquid and suction

Refrigerant in liquid form is normally put into the system through the _____

liquid line

When a refrigerant enters the compressor, it is a _____ and when it leaves the compressor is is a ____

low pressure low temperature superheated vapor, high pressure high temperature superheated vapor

The package air-conditioning system is ____ than the split system because it is completely factory assembled and charge with refrigerant.

more efficient

The TXV sensing bulb is mounted _____

on the suction line between the evaporator and the compressor

A fresh air intake is necessary to keep the indoor air from becoming

oxygen starved and stagnant

PSIG indicates

pounds per square inch absolute gauge

A Bourdon tube is often found in a(n)

pressure gauge

The compressor in a refrigeration system_____

pumps the refrigerant throughout the system

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

refrigerant condensing temperature

The process of removing heat from a place where it is not wanted and transferring that head to a place where it makes little or no difference is known as ____

refrigeration

The refrigerant in a condenser in a refrigeration system ____.

rejects heat

The condenser ____

rejects the heat from the refrigerant

Rotary compressors are used primarily in ____.

residential air conditioning

The dry-bulb temperature is the

sensible heat level of the air

Fractionation occurs when

some of a blended refrigerant evaporates or condenses before the rest of the blend

In reciprocating and scroll type motor-compressor assemblies, the motor is cooled by

suction gas returning to the compressor

Refrigerant in vapor form is normally put into the system through the _____

suction line

_____ is the best method of checking to see when a refrigerant coil has a proper level of refrigerant

superheat

Most of the heat energy in the suction vapor entering the compressor is

superheated from the evaporator

The wet-bulb temperature

takes into account the moisture content of the air

The dew-point temperature is the _____

temperature at which moisture begins to condense out of the air.

The ___ relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling the cooling system's temperatures.

temperature/pressure

The wet-bulb depression is

the difference between the dry and wet bulb temperatures

Refrigeration can be described as ____

the process of removing heat from a place where it is not wanted to a place where it makes little or no difference

As the temperature of a material increases, the molecules in the material _____

travel faster

when charging liquid refrigerant from a single valve supply cylinder, the cylinder is placed

upside down

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

If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____.

will increase


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