Mechanical Engineering Unit 11 To 20 When Drawing Diagram Operating System How Placement The Metering Device Line Determined

233)

When drawing a PH diagram of an operating system, how is placement of the metering device

line determined?

A)

The metering device line starts where the condenser line crosses the temperature of the

liquid line and then drops straight down until it crosses the compressor line.

B)

The metering device line starts where the condenser line crosses the temperature of the

liquid line and then goes straight across until it crosses the compressor line.

C)

The metering device line starts where the compressor line crosses the temperature of the

liquid line and then drops straight down until it crosses the condenser line.

D)

The metering device line starts where the condenser line crosses the temperature of the

liquid line and then drops straight down until it crosses the evaporator line.

Answer:

D

Explanation:

A)

B)

C)

D)

234)

All of the liquid refrigerant has vaporized by:

A)

The beginning of the condenser.

B)

The end of the condenser.

C)

The end of the evaporator.

D)

The beginning of the evaporator.

Answer:

C

Explanation:

A)

B)

C)

D)

235)

Zeotropic refrigerant blends condense and evaporate at:

A)

A single pressure.

B)

A single temperature.

C)

Multiple pressures.

D)

Multiple temperatures.

Answer:

D

Explanation:

A)

B)

C)

D)

236)

Adiabatic expansion means:

A)

Expanding through the use of centrifugal force.

B)

Expanding by adding heat.

C)

Expanding without adding heat.

D)

Expanding by applying a strong magnetic field to a polarized substance.

Answer:

C

Explanation:

A)

B)

C)

D)

61

237)

Vertical lines going from top to bottom are referred to as which of the following?

A)

Constant quality

B)

Saturation curve

C)

Enthalpy

D)

Pressure line

Answer:

C

Explanation:

A)

B)

C)

D)

238)

What happens to the temperature of the refrigerant as you move to the right or left along a

constant temperature line inside the saturation curve?

A)

The temperature increases as you move to the right.

B)

The temperature increases as you move to the left.

C)

The enthalpy diagram does not show temperature.

D)

The temperature remains the same.

Answer:

D

Explanation:

A)

B)

C)

D)

239)

The heat of compression can be determined using:

A)

The enthalpy difference from the beginning to the end of the metering device line.

B)

The enthalpy difference from the beginning to the end of the condenser line.

C)

The enthalpy difference from the beginning to the end of the evaporator line.

D)

The enthalpy difference from the beginning to the end of the compressor line.

Answer:

D

Explanation:

A)

B)

C)

D)

240)

What happens to the pressure as you move up or down along a constant enthalpy line?

A)

The pressure remains the same.

B)

The pressure is not related to vertical movement along the constant enthalpy line.

C)

The pressure decreases as you move down.

D)

The pressure decreases as you move up.

Answer:

C

Explanation:

A)

B)

C)

D)

62

241)

When the refrigerant passes through the metering device, some of it starts to flash from a liquid to

a gas because:

A)

The pressure has dropped to the saturation point.

B)

A large amount of heat is added to the refrigerant in the metering device.

C)

The pressure has increased above the saturation point.

D)

Of the turbulators located near the end of the metering device.

Answer:

A

Explanation:

A)

B)

C)

D)

242)

Where on the enthalpy diagram is refrigerant saturated?

A)

On and inside the saturation curve

B)

Everything to the right of the saturated line of demarcation

C)

Everywhere on the chart is saturated because the enthalpy diagram is specifically for

saturated refrigerant

D)

There are no areas of saturation because the enthalpy chart is for gases.

Answer:

A

Explanation:

A)

B)

C)

D)

243)

What happens to the temperature of the refrigerant as you move to the right or left along a

constant temperature line outside the saturation curve?

A)

The temperature decreases as you move to the right.

B)

The temperature remains the same.

C)

The temperature decreases as you move to the left.

D)

The enthalpy diagram does not show temperature.

Answer:

B

Explanation:

A)

B)

C)

D)

63

244)

A refrigerant’s enthalpy is:

A)

Mathematically derived from the refrigerant’s pressure and temperature.

B)

An index of environmental compatibility.

C)

The total amount of heat in the refrigerant.

D)

A purely theoretical concept that has never been demonstrated.

Answer:

C

Explanation:

A)

B)

C)

D)

245)

All refrigerants with a three–digit number starting with the number 4 are:

A)

Refrigerant effects.

B)

Compounds.

C)

Refrigerant blends.

D)

Zeotropic blends.

Answer:

D

Explanation:

A)

B)

C)

D)

246)

How is entropy defined in refrigeration?

A)

Entropy is the total amount of heat in the refrigerant.

B)

Entropy is the ratio of heat content to absolute temperature.

C)

Entropy is the amount of heat remaining after subtracting the heat of compression from the

enthalpy.

D)

Entropy is the ratio of absolute pressure to absolute temperature.

Answer:

B

Explanation:

A)

B)

C)

D)

247)

What pressure units are used on the enthalpy diagram?

A)

Bars

B)

Psia

C)

Pascals

D)

Psig

Answer:

B

Explanation:

A)

B)

C)

D)

64

248)

Where can information regarding first aid be found in the SDS?

A)

Section 1

B)

Section 2

C)

Section 3

D)

Section 4

Answer:

D

Explanation:

A)

B)

C)

D)

249)

Asphyxiation may occur from breathing in refrigerant, as it is heavier than air and will:

A)

Release nitrogen into the room.

B)

Settle at the ceiling.

C)

Displace air in the room.

D)

Create carbon monoxide fumes.

Answer:

C

Explanation:

A)

B)

C)

D)

250)

A refrigerant sensor that changes conductivity when exposed to refrigerant is:

A)

Diffusion infrared.

B)

Infrared nondispersive (NDIR).

C)

Photoacoustic infrared (PIR).

D)

Ceramic metal oxide semiconductor (CMOS).

Answer:

D

Explanation:

A)

B)

C)

D)

251)

To avoid releasing large quantities of refrigerant inside a mechanical room, ANSI/ASHRAE

Standard 15–2010 specifies that rupture disks:

A)

Should be controlled through a hand valve.

B)

Should be replaced with solid brass plugs.

C)

Should only be used on equipment located outside.

D)

Should be piped outside the building.

Answer:

D

Explanation:

A)

B)

C)

D)

65

252)

How often must refillable refrigerant cylinders be recertified?

A)

Every 10 years

B)

Every 20 years

C)

Every 5 years

D)

They only require certification when they are manufactured.

Answer:

C

Explanation:

A)

B)

C)

D)

253)

After someone has inhaled a large quantity of refrigerant:

A)

Administer the Heimlich maneuver to dislodge the refrigerant.

B)

Take them outside to fresh air.

C)

Lay them down ion the room and keep them comfortable.

D)

Hit them hard on the back several times to drive out the refrigerant.

Answer:

B

Explanation:

A)

B)

C)

D)

254)

The most common hazard encountered when installing and removing refrigeration gauges is:

A)

Electrocution.

B)

Chemical poisoning.

C)

Frostbite.

D)

Asphyxiation.

Answer:

C

Explanation:

A)

B)

C)

D)

255)

Ground–up aluminum can react violently with which of the following?

A)

HFC

B)

Oxygen

C)

CFC

D)

CFC and HFC

Answer:

A

Explanation:

A)

B)

C)

D)

66

256)

Airflow pattern must be taken into account so that the refrigerant sensor is:

A)

Mounted downstream from the potential leak source.

B)

Mounted on the ceiling by the potential leak source.

C)

Mounted near the door by the potential leak source.

D)

Mounted upstream from the potential leak source.

Answer:

A

Explanation:

A)

B)

C)

D)

257)

How can infrared light be used to detect refrigerant?

A)

Infrared sensors change resistance in the presence of refrigerant.

B)

Infrared sensors interact with oxygen at different rates depending on the refrigerant

exposure.

C)

Refrigerant turns the infrared light blue.

D)

Most gases absorb infrared light at a characteristic frequency.

Answer:

D

Explanation:

A)

B)

C)

D)

258)

When should a technician read the SDS for a particular refrigerant?

A)

On the way to the hospital

B)

In the event of an emergency

C)

After being exposed to the refrigerant

D)

Before using the refrigerant

Answer:

D

Explanation:

A)

B)

C)

D)

259)

External safety valves are sealed by whom?

A)

The technician

B)

The seller

C)

The manufacturer

D)

The customer

Answer:

C

Explanation:

A)

B)

C)

D)

67

260)

Which pressure relief device works primarily by temperature?

A)

Pressure relief valve

B)

Fusible plug

C)

Rupture disk

Answer:

B

Explanation:

A)

B)

C)

261)

If an open flame is near a type 3 rating, the refrigerant:

A)

Will condense.

B)

Will slowly burn.

C)

Will support combustion.

D)

Will not ignite at all.

Answer:

C

Explanation:

A)

B)

C)

D)

262)

To avoid breathing in spilled materials, you should immediately use which of the following?

A)

Face shield

B)

The SCBA mask

C)

HEPA mask

D)

Surgical mask

Answer:

B

Explanation:

A)

B)

C)

D)

263)

Which type of pressure relief device can reseat when the pressure returns to normal?

A)

Fusible plug

B)

Rupture disk

C)

Pressure relief valve

Answer:

C

Explanation:

A)

B)

C)

264)

Optional components found on the low side of a refrigeration system include:

A)

Suction line filter, accumulator, and evaporator pressure regulator.

B)

Discharge line muffler, oil separator, liquid receiver, and liquid line filter–drier.

C)

Suction to liquid heat exchanger, economizer, and oil level regulator.

D)

All optional components can be used on the low side of the system.

Answer:

A

Explanation:

A)

B)

C)

D)

68

265)

The ________ is a device for absorbing heat into the refrigeration system.

A)

evaporator

B)

compressor

C)

condenser

D)

coil

Answer:

A

Explanation:

A)

B)

C)

D)

266)

The heat rejected by the condenser:

A)

Equals the heat added by the compressor.

B)

Equals the heat absorbed by the evaporator plus the heat added by the compressor.

C)

Has no relationship to either the evaporator or compressor.

D)

Equals the heat absorbed by the evaporator.

Answer:

B

Explanation:

A)

B)

C)

D)

267)

How can scaling be reduced in water towers?

A)

There is a small amount of water saved from the cooling tower sump.

B)

There is a small amount of water added once a day to the cooling tower.

C)

There is a small amount of water added constantly to the cooling tower.

D)

There is a small amount of water drained off the cooling tower sump.

Answer:

D

Explanation:

A)

B)

C)

D)

268)

Which type of condenser generally operates with a lower discharge pressure?

A)

Forced–draft air–cooled condensers

B)

Water–cooled condensers

C)

Natural–draft air–cooled condensers

D)

The discharge pressure is not affected by the type of condenser used.

Answer:

B

Explanation:

A)

B)

C)

D)

69

269)

Why do some commercial buildings need air conditioning in the winter?

A)

Commercial buildings often have large internal heat loads from people, lights, and

machines.

B)

The complexity of control systems for commercial buildings often causes a system to cool a

building even when cooling is not needed.

C)

Lower temperatures reduce the spread of bacteria.

D)

Commercial buildings are maintained at lower temperatures to improve productivity.

Answer:

A

Explanation:

A)

B)

C)

D)

270)

Why do water and refrigerant flow in opposite directions in tube–in–tube condensers?

A)

To decrease pressure

B)

To decrease efficiency

C)

To increase efficiency

D)

To increase pressure

Answer:

C

Explanation:

A)

B)

C)

D)

271)

Why are wastewater systems no longer allowed in some areas of the country?

A)

There are concerns about possible health issues of using sewage water to cool condensers.

B)

Solids found in waste water can clog up the condensers.

C)

Water resources are becoming increasingly scarce.

D)

Heating the wastewater interferes with the sewage treatment.

Answer:

C

Explanation:

A)

B)

C)

D)

272)

What is the difference between the compressor operating temperatures in an air–cooled condenser

and a water–cooled condenser?

A)

A water–cooled condenser operates 25°F above an air–cooled condenser.

B)

A water–cooled condenser operates 25°F below an air–cooled condenser.

C)

A water–cooled condenser operates 15°F above an air–cooled condenser.

D)

A water–cooled condenser operates 15°F below an air–cooled condenser.

Answer:

D

Explanation:

A)

B)

C)

D)

70

273)

Which type of condenser is on the back of a non–frostfree refrigerator?

A)

An induced–draft air–cooled condenser

B)

A packaged air–cooled condenser

C)

A natural–draft air–cooled condenser

D)

A forced–draft air–cooled condenser

Answer:

C

Explanation:

A)

B)

C)

D)

274)

If the water entering a water–cooled condenser is 80°F, what would the leaving water temperature

be?

A)

110°F

B)

80°F

C)

100°F

D)

90°F

Answer:

D

Explanation:

A)

B)

C)

D)

275)

If the temperature of the refrigerant in a water–cooled system is 95°F, what is the temperature of

the leaving water?

A)

110°F

B)

105°F

C)

85°F

D)

80°F

Answer:

C

Explanation:

A)

B)

C)

D)

276)

The three types of air–cooled condenser coil construction found on residential air–conditioning

units today include:

A)

Iron, aluminum, and steel.

B)

Tube–and–fin, spine–fin, and microchannel.

C)

Flat plate, bare tube, and tube–and–fin.

D)

Wired, wireless, and adaptive.

Answer:

B

Explanation:

A)

B)

C)

D)

71

277)

To increase superheat on a thermostatic expansion valve, the adjusting stem should be:

A)

Removed

B)

Back–seated

C)

Turned clockwise

D)

Turned counterclockwise

Answer:

C

Explanation:

A)

B)

C)

D)

278)

Which type of metering device used on flooded evaporators opens to admit more liquid

refrigerant into the evaporator when the liquid level in the evaporator drops?

A)

Automatic expansion valve

B)

High–side float

C)

Low–side float

D)

Electronic expansion valve

Answer:

C

Explanation:

A)

B)

C)

D)

279)

Valves that open and close rapidly under the control of electronic circuits are:

A)

Pulse–modulated valves.

B)

Step motor valves.

C)

Electronic expansion valves.

D)

Cross–charged expansion valves.

Answer:

A

Explanation:

A)

B)

C)

D)

280)

To increase the evaporator pressure, the adjustment on top of an automatic expansion valve

should be:

A)

Turned clockwise.

B)

Turned off.

C)

Turned on.

D)

Turned counterclockwise.

Answer:

A

Explanation:

A)

B)

C)

D)

72

281)

Capillary tube metering devices are commonly used today in:

A)

Low–pressure chillers.

B)

Window units.

C)

Large split system air–conditioning systems.

D)

Commercial refrigeration rack systems.

Answer:

B

Explanation:

A)

B)

C)

D)

282)

When the heat load on the evaporator increases, the automatic expansion valve:

A)

Opens to feed more refrigerant.

B)

Sends a signal to the electronic control board indicating the change.

C)

Closes to keep the pressure from increasing.

D)

Does nothing because AEVs are not modulating devices.

Answer:

C

Explanation:

A)

B)

C)

D)

283)

Which of the following is a rarely used metering device that can be used in applications where the

load is constant and an operator is present to make manual adjustments?

A)

Fixed valves

B)

Hand–operated expansion valves

C)

Modulating metering devices

D)

Fixed metering devices

Answer:

B

Explanation:

A)

B)

C)

D)

284)

How can moisture in the refrigeration system affect the metering device?

A)

Water will improve the thermal contact of the expansion valve bulb.

B)

Water will not affect metering device operation.

C)

Water in the system improves operation of the metering device through hydronic cooling.

D)

Water can freeze up at the metering device, causing a restriction.

Answer:

D

Explanation:

A)

B)

C)

D)

73

285)

Which type of metering device is able to respond to changes in system operations?

A)

Modulating metering devices

B)

Fixed metering devices

C)

Fixed valves

D)

Hand–operated expansion valves

Answer:

A

Explanation:

A)

B)

C)

D)

286)

The system capacity of an air conditioner with a fixed metering device:

A)

Decreases when the indoor wet bulb temperature rises.

B)

Increases when the indoor wet bulb temperature rises.

C)

Is at its maximum when the indoor and outdoor temperatures are the same.

D)

Is fixed regardless of the indoor wet bulb temperature.

Answer:

A

Explanation:

A)

B)

C)

D)

287)

In an air conditioner with a fixed metering device, a decrease in the outdoor ambient causes:

A)

Increased system capacity.

B)

Increased system superheat.

C)

No appreciable change in either system capacity or superheat.

D)

Decreased system superheat.

Answer:

B

Explanation:

A)

B)

C)

D)

288)

Automatic expansion valves are similar in operating concept to:

A)

Pressure regulators.

B)

Electronic expansion valves.

C)

Fixed restrictions.

D)

Manual valves.

Answer:

A

Explanation:

A)

B)

C)

D)

74

289)

Which of the following problems can be caused by restrictions in the capillary tubes?

A)

High suction pressure

B)

Low suction pressure

C)

Low suction line temperature

D)

Low box temperature

Answer:

B

Explanation:

A)

B)

C)

D)

290)

Why is it dangerous to drill out orifices in metering devices?

A)

The metal is too hard to drill through.

B)

The orifices are conical in shape.

C)

The metal is too soft to drill through.

D)

The orifices are rectangular in shape.

Answer:

B

Explanation:

A)

B)

C)

D)

291)

Compared to air–conditioning evaporator coils, commercial refrigeration coils have:

A)

Materials that are less brittle at low temperatures.

B)

More fins per inch.

C)

Fewer fins per inch.

D)

About the same number of fins per inch.

Answer:

C

Explanation:

A)

B)

C)

D)

292)

Which of the following is a type of sports arena that uses flooded evaporators?

A)

Ice rink

B)

Basketball court

C)

Baseball field

D)

Soccer field

Answer:

A

Explanation:

A)

B)

C)

D)

75

293)

Commercial refrigeration equipment for dry storage typically uses:

A)

High–temperature evaporators.

B)

Medium–temperature evaporators.

C)

Low–temperature evaporators.

D)

Ultra–low–temperature evaporators.

Answer:

A

Explanation:

A)

B)

C)

D)

294)

What does it mean for a condenser and evaporator coil to be an “AHRI Match”?

A)

AHRI has tested the components and certified that they work correctly together.

B)

AHRI manufactured the components.

C)

AHRI was paid to advertize those particular components.

D)

Both components were made by the same manufacturer.

Answer:

A

Explanation:

A)

B)

C)

D)

295)

In what circumstances would bare–pipe evaporators most likely be used?

A)

Low–temperature refrigeration storage

B)

Heat pump indoor coils

C)

Air–conditioning coils

D)

Medium–temperature walk–in cooler evaporators

Answer:

A

Explanation:

A)

B)

C)

D)

296)

To prevent liquid slugs from leaving the evaporator and entering the compressor, direct

expansion evaporators:

A)

Are typically fed at the top with suction gas leaving at the bottom.

B)

Are typically fed at the top and bottom with suction gas leaving in the middle.

C)

Are typically fed at the bottom with suction gas leaving at the top.

D)

Are typically fed in the middle with suction gas leaving at the top and bottom.

Answer:

C

Explanation:

A)

B)

C)

D)

76

297)

Why might there be a negative pressure on the condensate outlet in a coil operating at a positive

static pressure?

A)

The algae collecting in the drain pan creates a negative pressure.

B)

A positive static pressure is really negative compared to atmospheric pressure.

C)

The draining water creates an internal pressure in the drain line.

D)

The air velocity can create a negative pressure.

Answer:

D

Explanation:

A)

B)

C)

D)

298)

Water–cooling evaporator constructions include:

A)

Tube–in–tube, shell–and–coil, and shell–and–tube.

B)

Smooth tube, twisted tube, and rifled tube.

C)

Inline, opposed, and offset.

D)

Water tube, fire tube, and refrigerant tube.

Answer:

A

Explanation:

A)

B)

C)

D)

299)

Heat flows from the product into the evaporator because:

A)

The evaporator is at a lower pressure than the product.

B)

The refrigerant in the evaporator has fewer BTU/lb than the product.

C)

The evaporator is at a lower temperature than the product.

D)

The refrigerant in the evaporator has a lower specific heat than the product.

Answer:

C

Explanation:

A)

B)

C)

D)

300)

What is the purpose of epoxy coating on evaporator coils?

A)

To provide better heat transfer

B)

To provide corrosion resistance

C)

To improve airflow efficiency

D)

To prevent water condensation on the evaporator coil

Answer:

B

Explanation:

A)

B)

C)

D)

77

301)

Small domestic refrigerators and freezers use:

A)

Plate evaporators.

B)

Tube–in–tube evaporators.

C)

Flooded evaporators.

D)

A–coils.

Answer:

A

Explanation:

A)

B)

C)

D)

302)

The tight bond between the refrigerant tube and the fins on tube–and–fin coils is made by:

A)

Machining the fins and tubing out of a single piece of solid metal.

B)

Expanding the tubing into the fins.

C)

Soldering the fins to the tubing.

D)

Glueing the fins to the tubing.

Answer:

B

Explanation:

A)

B)

C)

D)

303)

Zeotropes are mixtures of two or more refrigerants:

A)

That do not separate when changing state.

B)

That separate when changing state.

C)

That are electromagnetically bonded to form a new refrigerant.

D)

That are chemically bonded to form a new refrigerant.

Answer:

B

Explanation:

A)

B)

C)

D)

304)

Which oil was designed to be used in the same place where mineral oil is used?

A)

Glycol–based oil

B)

Mineral oil

C)

Alkyl benzene

D)

Polyol ester

Answer:

C

Explanation:

A)

B)

C)

D)

78

305)

HFCs are comprised of hydrogen, fluorine, and:

A)

Chromium.

B)

Copper.

C)

Chlorine.

D)

Carbon.

Answer:

D

Explanation:

A)

B)

C)

D)

306)

Which of the following refrigerant safety designations indicate the refrigerant is somewhat

flammable?

A)

B1

B)

A1

C)

A2

D)

B3

Answer:

C

Explanation:

A)

B)

C)

D)

307)

The chemical components of CFC refrigerants are:

A)

Carbon, Freon, and chlorine.

B)

Chlorine, fluorine, and carbon.

C)

Chlorine, Freon, and chromium.

D)

Carbon, frankincense, and Clorox.

Answer:

B

Explanation:

A)

B)

C)

D)

308)

In the refrigerant safety rating B1, what does the 1 signify?

A)

Low flammability

B)

Nonflammable

C)

High pressure

D)

High flammability

Answer:

B

Explanation:

A)

B)

C)

D)

79

309)

The major safety concern with R–410A compared to most other common refrigerants is that:

A)

R–410A operates at much higher pressures.

B)

R–410A is toxic.

C)

R–410A is flammable.

D)

R–410A is chemically unstable.

Answer:

A

Explanation:

A)

B)

C)

D)

310)

Which of the following refrigerant safety designations indicate the refrigerant is highly

flammable?

A)

A2

B)

A1

C)

B1

D)

B3

Answer:

D

Explanation:

A)

B)

C)

D)

311)

The presence of noncondensables in a refrigerant recovery cylinder can be detected by:

A)

Comparing the cylinder pressure and temperature to a PT chart.

B)

Testing to see if the gas on top of the cylinder will burn.

C)

Checking the acidity of the refrigerant with litmus paper.

D)

Comparing the actual cylinder weight to the cylinder water capacity.

Answer:

A

Explanation:

A)

B)

C)

D)

312)

The chemical family that is the basic building block for most modern refrigerants is:

A)

Purons.

B)

Alcohols.

C)

Freons.

D)

Hydrocarbons.

Answer:

D

Explanation:

A)

B)

C)

D)

80