Quiz about Refrigeration and Thermodynamics sample

Question 1

What is the SI base unit for temperature?

Accepted Answer

Kelvin.

Answer

Fahrenheit.

Answer

Celsius.

Answer

Rankine.

Question 2

What is the derived SI unit of the measurement of the rate of energy flow?

Accepted Answer

Watt.

Answer

Joule.

Answer

Kelvin.

Answer

Newton.

Question 3

What is the same when two bodies are in thermal equilibrium?

Accepted Answer

Their temperature.

Answer

Their energy content.

Answer

Their thermal conductivity.

Answer

Their mass.

Question 4

Which is an absolute temperature scale?

Accepted Answer

Kelvin.

Answer

Fahrenheit.

Answer

Celsius.

Answer

Centigrade.

Question 5

What happens to molecules at absolute zero?

Accepted Answer

They are motionless.

Answer

They vibrate very fast.

Answer

They vibrate very slowly.

Answer

They change state.

Question 6

Which thermodynamic law states that energy cannot be created or destroyed, but only converted?

Accepted Answer

First law.

Answer

Boyle's law.

Answer

Charles' law.

Answer

Second law.

Question 7

Which thermodynamic law describes ice melting in a glass of warm water?

Accepted Answer

Second law.

Answer

Boyle's law.

Answer

First law.

Answer

Charles' law.

Question 8

The heat from the sun travels to Earth by which process or processes?

Accepted Answer

Radiation

Answer

Conduction

Answer

Convection

Answer

Evaporation

Question 9

What is the SI unit for energy?

Accepted Answer

Joule.

Answer

Pascal.

Answer

Watt.

Answer

Kelvin.

Question 10

What are the units for work done over time?

Accepted Answer

Kilowatts.

Answer

Kilojoules per kilogram.

Answer

Kilocalories.

Answer

Kilojoules.

Question 11

What is the result of 6000 J being removed from a product in two minutes?

Accepted Answer

30 W.

Answer

50W.

Answer

3kW.

Answer

12kW.

Question 12

The process when a liquid changes to a vapour is called:

Accepted Answer

Evaporation

Answer

Condensation

Answer

Sublimation

Answer

Freezing

Question 13

Where is sensible heat gained in a refrigeration system, under normal conditions?

Accepted Answer

Suction line.

Answer

Liquid line.

Answer

Hot gas line.

Answer

Discharge line.

Question 14

What is the approximate difference between the values of the specific heat capacity of a solid compared to a liquid?

Accepted Answer

Half.

Answer

Four times.

Answer

A quarter.

Answer

Double.

Question 15

What happens when latent heat is removed from a substance?

Accepted Answer

It causes a change in phase but not in temperature.

Answer

It causes a change in temperature but not in phase.

Answer

The substance becomes subcooled.

Answer

The substance becomes superheated.

Question 16

If 8 kg of water has a heat input of 215 kJ, how much will its temperature rise, given the specific heat capacity of water as 4.2 kJ/kgK?

Accepted Answer

6.4 K

Answer

2.5 K

Answer

10.2 K

Answer

1.2 K

Question 17

What is force divided by area better known as?

Accepted Answer

Pressure.

Answer

Torque.

Answer

Temperature.

Answer

Stress.

Question 18

What is 1 N/m2 equivalent to?

Accepted Answer

1 Pascal.

Answer

1 Torr.

Answer

1 PSI.

Answer

1 Atmosphere.

Question 19

What is a pressure of 10 mm Hg equal to?

Accepted Answer

10 000 microns.

Answer

1 atmosphere.

Answer

1 Pascal.

Answer

1 millibar.

Question 20

What is a common description of a vacuum?

Accepted Answer

B. Any pressure well below normal atmospheric pressure.

Answer

A. A pressure between plus 1.0 bar to minus 1.0 bar.

Answer

A negative absolute pressure.

Answer

When no pressure is being exerted

Question 21

What is the resulting volume if 0.08 m3 of a gas at 300 K and a pressure of 700 kN/m2 is increased to 500 K and a pressure of 500 kN/m2?

Accepted Answer

0.133 m3.

Answer

0.057 m3.

Answer

0.187 m3.

Answer

0.428 m3.

Question 22

What causes flash gas in the line after a partially blocked filter drier?

Accepted Answer

The reduction in pressure.

Answer

The heat of compression.

Answer

The increase in pressure

Answer

The removal of heat

Question 23

What must be present for the pressure temperature relationship to be correct?

Accepted Answer

Saturated liquid and vapour.

Answer

Superheated vapour.

Answer

Subcooled liquid.

Answer

Subcooled vapour and superheated liquid.

Question 24

What effect does subcooled liquid have on system performance?

Accepted Answer

Increased cooling capacity.

Answer

Increased discharge temperature.

Answer

Decreased discharge temperature.

Answer

Decreased motor current.

Question 25

What is a function of the compressor?

Accepted Answer

To increase the pressure in the evaporator.

Answer

To maintain the pressure in the evaporator.

Answer

To reduce the pressure in the liquid line.

Answer

To increase the pressure in the suction line.

Question 26

What is the source of the total heat rejected by the condenser?

Accepted Answer

The compressor work done, suction line superheat and liquid line sub-cooling.

Answer

Only the heat absorbed in the evaporator.

Answer

Ambient air temperature only.

Answer

The refrigerant mass flow rate only.

Question 27

What happens to the system refrigerant during compression?

Accepted Answer

The temperature and enthalpy increase, the entropy remains constant.

Answer

The pressure, temperature and entropy increase.

Answer

The enthalpy and temperature increase, the entropy decreases.

Answer

The enthalpy and pressure decrease, and the entropy remains constant.

Question 28

What is the benefit of having superheated vapour at the compressor inlet?

Accepted Answer

It ensures that no liquid enters the compressor.

Answer

It ensures the compressor oil is free flowing.

Answer

It prevents frost formation on the compressor body.

Answer

It evaporates condensate around the compressor.

Question 29

Which points shown on the PH chart identify the refrigerant flow through the expansion device?

Accepted Answer

D to F.

Answer

C to D.

Answer

D to E.

Answer

C to F.

Question 30

What does sub-cooled liquid reduce when it enters the expansion device?

Accepted Answer

Flash gas.

Answer

Refrigeration effect.

Answer

Evaporating pressure.

Answer

Compressor work done.

Question 31

What is the most likely reason for the PH plot of a cooling system, shown as ABCD on the chart, to change to AEFG?

Accepted Answer

High ambient temperature.

Answer

High suction superheat.

Answer

Heavy cooling load.

Answer

Increase in crankcase temperature.

Question 32

What would cause the cycle shown as ABCD on the PH chart to change to cycle EFGH?

Accepted Answer

Worn suction and discharge reed valves.

Answer

Low ambient air temperature.

Answer

Failed condenser fan.

Answer

High cooling load.

Question 33

What would cause the cycle shown as ABCD on the PH chart to change to the cycle shown as EFGH?

Accepted Answer

Evaporator fan failure.

Answer

High ambient temperature.

Answer

Condenser fan failure.

Answer

Excessive suction line superheat.

Question 34

What happens to moist air when it passes through the indoor unit of an air conditioning system?

Accepted Answer

The air is cooled and some of the moisture vapour condenses.

Answer

As air is cooled, moisture vapour stays at the same temperature.

Answer

As the air temperature falls, the moisture content stays the same.

Answer

The combined air and moisture vapour begin to condense.

Question 35

When measuring an air sample using wet and dry bulb thermometers, what indicates that the air is at maximum humidity?

Accepted Answer

The wet and dry bulb temperatures are the same.

Answer

The wet and dry bulb temperatures are slightly different.

Answer

The dry bulb temperature is much lower than the wet bulb temperature.

Answer

The wet bulb temperature is much lower than the dry bulb temperature.

Question 36

How is a wet bulb thermometer kept moist?

Accepted Answer

By a wick tube connected to a reservoir.

Answer

By gravity feed of water from a reservoir.

Answer

By a pumped cold water spray.

Answer

By immersion in a water reservoir.

Question 37

Which describes the process path on the psychrometric chart from point 1 to point 4?

Accepted Answer

Cooling and dehumidification.

Answer

Cooling and humidification.

Answer

Heating and humidification.

Answer

Heating and dehumidification.

Question 38

The moisture removed can be found by using which points on the psychrometric chart?

Accepted Answer

6 minus 7.

Answer

1 minus 2.

Answer

3 minus 4.

Answer

4 minus 5.

Question 39

What feature is available from a standard wall mounted split AC system?

Accepted Answer

Control of air volume.

Answer

Re-humidification of supply air.

Answer

Preheating of fresh air.

Answer

Simultaneous heating and cooling.

Question 40

What is the effect of reducing the evaporator saturation temperature?

Accepted Answer

Air moisture content reduced.

Answer

Increased air moisture content.

Answer

Air moisture content unchanged.

Answer

Increase in air moisture density.

Question 41

What defines the total heat output of a heat pump system?

Accepted Answer

AE + BA.

Answer

DE + BA.

Answer

BC + DE.

Answer

AE + BC.

Question 42

What describes the term 'temperature difference' for a ground source heat pump?

Accepted Answer

It is the difference between the ground and collector coil temperatures.

Answer

It is the difference between the evaporator and collector coil temperatures.

Answer

It is the difference between the condenser and evaporator temperatures.

Question 43

What is the difference between the heat outputs of a gas boiler, with an efficiency of 80%, compared to a heat pump with an EER of 4.0?

Accepted Answer

The heat pump gives off 4.0 times as much heat/kW input.

Answer

The heat pump gives off 1.6 times as much heat/kW input.

Answer

The heat pump gives off twice as much heat/kW input.

Answer

The heat pump gives off 5.0 times as much heat/kW input.

Question 44

What occurs when refrigerant vapour flows around a short radius bend?

Accepted Answer

Pressure decreases.

Answer

Temperature increases.

Answer

Vibration decreases.

Answer

Vapour density increases.

Question 45

What is the result of high pressure drop in the liquid line of an RAC system?

Accepted Answer

Reduced cooling capacity.

Answer

Oil return rate will increase.

Answer

Condensing pressure will reduce.

Answer

Mass flow rate will increase.

Question 46

What is the impact of installing undersized pipework?

Accepted Answer

A decrease in cooling capacity.

Answer

An increase in mass flow rate.

Answer

A decrease in flash gas formation.

Answer

An increase in refrigeration effect.

Question 47

What ensures oil returns to the compressor under full load conditions?

Accepted Answer

Pipes are sized for correct velocity.

Answer

Use of mineral oil in the compressor.

Answer

Pipes are sized to give minimum pressure drop.

Answer

A miscible oil is used in the compressor.

Question 48

What effect will a reduction in refrigerant velocity have on system performance?

Accepted Answer

Decreased oil return to compressor.

Answer

Increased oil return to the compressor.

Answer

Decreased discharge temperature.

Answer

Increased discharge temperature.

Question 49

Where is aluminium commonly found in a domestic refrigerator?

Accepted Answer

Evaporator.

Answer

Condenser.

Answer

Discharge line.

Answer

Condensate drain.

Question 50

What materials should be used with ammonia systems?

Accepted Answer

Steel.

Answer

Copper.

Answer

Bronze.

Answer

Brass.

Question 51

What is zinc coating used for?

Accepted Answer

To provide corrosion protection.

Answer

To allow for flux free brazing.

Answer

It increases heat transfer rate.

Answer

As a primer for UV resistant paint.

Refrigeration and Thermodynamics sample

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