refrigeration

The CSA B52 code requires that pressure limiting devices shall be provided on all systems operating above atmospheric pressure, except on a factory sealed system containing less than _____ of group A1 refrigerant: 9 kg 7 kg 10 kg 5 kg 3 kg

10 kg

A pressure relief device on a refrigeration system shall have sufficient capacity to prevent the pressure in the pressure vessel from rising more than _____ above the setting of the pressure relief device. 10% 15% 103 kPa 25% 50%

10%

The amount of heat absorbed by water when it evaporates at atmospheric pressure is: 99.63 kJ/kg 335 kJ/kg 417.46 kJ/kg 2257 kJ/kg 2675.5 kJ/kg

2257 kJ/kg

direct expansion type evaporator that has more than one refrigerant circuit requires __________ to provide even refrigerant flow in each circuit. A stop valve An expansion valve A distributor A purge valve A thermal regulator

A distributor

The net refrigerating effect of a refrigerant is the amount of heat: Discharged by the condenser. Absorbed by the refrigerant in the evaporator. Absorbed by the refrigerant in the condenser. Discharged by the refrigerant in the evaporator. Absorbed by the evaporator.

Absorbed by the refrigerant in the evaporator

A stationary crankshaft seal used on refrigeration compressors, which consists of a metallic bellows soldered at one end to a ring, and which presses against a shoulder on the shaft is called a: Packing gland seal Diaphragm seal Bellows seal Rotating Mechanical seal Set screw

Bellows seal

A refrigeration compressor's oil pressure failure switch uses a _________ element as part of its operating mechanism. Fluid expansion Bimetallic Thermostatic Humidity activated Volumetric

Bimetallic

All refrigeration evaporators: Require regular defrosting. Are part of the high side of the system. Are located between the expansion valve and the king valve. Are flooded with refrigerant. Boil liquid refrigerant at low pressure and low temperature.

Boil liquid refrigerant at low pressure and low temperature.

(4-113-1.04) The saturation temperature of a refrigerant is the same as its: Boiling point Freezing point Flash point Fire point Auto ignition temperature

Boiling point

Which of the following is NOT considered a rotary refrigeration compressor design? Screw Sliding vane Helical rotor Centrifugal Stationary single-blade

Centrifugal

(4-113-2.01) The function of the condenser in a refrigeration system is to: Lower the temperature of the liquid refrigerant. Change high pressure refrigerant vapour to liquid. Pressurize low pressure refrigerant vapour. Vent off vaporized refrigerant. Lower the liquid refrigerant pressure.

Change high pressure refrigerant vapour to liquid.

If the first column of a refrigeration table lists the saturation temperature of a refrigerant, which column will most likely list the saturation pressure? Column 1 Column 2 Column 3 Column 4 Column 5

Column 2

Which of the following is not a component of the low pressure side of a compression refrigeration system? Compressor discharge piping The evaporator The downstream side of the expansion valve Compressor inlet The suction line

Compressor discharge piping

Refrigerant condensers: Are always water cooled. Cool the gas refrigerant discharged from the compressor. Are usually 2-stage designs. Remove sensible heat only from the refrigerant. Transfer less heat per unit time than the evaporators installed on the same system.

Cool the gas refrigerant discharged from the compressor.

hich of the following is not a physical property of refrigerants: Toxicity Odour Leakage tendency Corrosiveness Miscibility

Corrosiveness

Refrigerant compressors: Must have intercoolers. Could be centrifugal type. Use automotive-style suction and discharge valves. Have more cooling fins than air compressors. Discharge directly into the evaporator.

Could be centrifugal type.

An emergency discharge system is installed on a refrigeration system to prevent serious conditions, such as: Over-charging Toxic refrigerant leaks Excessive non-condensable gases Dangerously high system pressures Compressor breakdown

Dangerously high system pressures

The property which has to be known for the calculation of the size of control valves and piping etc. is: Specific gravity Enthalpy Refrigerating effect Density Boiling point

Density

A negative factor of Hermetic Type refrigeration compressors is: They are too large to be used in any application except large industrial plants. The drive motor tends to overheat. Shaft sealing is difficult. Field servicing is not possible. It is difficult to replace the shaft coupling.

Field servicing is not possible.

(4-114-1.03) R-134a is non-toxic and non-flammable. Which of the following groups does it belong to? Group A2 Group B4 Group A1 Group A3 Group B2

Group A1

One function of vibration absorbers is to: Lower noise levels. Allow the load on the system to increase dramatically without straining the components in the system. Increase longevity of the system. Insulate piping and make the system more efficient. Align piping.

Lower noise levels.

The ability of a refrigerant to be dissolved into oil and vice versa is called: Moisture reaction Solubility Density Leakage tendency Miscibility

Miscibility

The safety control that uses a current transformer with a resistor in the motor circuit is known as: High motor temperature cut-out Low oil sump temperature cut-out Motor overload protection Low pressure cut-out High oil temperature cut-out

Motor overload protection

The emergency discharge line of a refrigeration system: Is located only on the condenser. Must have a manually-operated emergency discharge valve outside the building. Is required on all sizes of refrigeration systems. Is connected to the liquid space of the receiver. Must be painted bright yellow.

Must have a manually-operated emergency discharge valve outside the building.

An evaporator that can easily be cleaned and defrosted manually without interrupting the cooling process is which type of evaporator? Bare finned evaporator Finned evaporator Plate surface evaporator Shell and tube evaporator None of the above

Plate surface evaporator

(4-120-1.01) Which of the following pipe joints are permitted for high pressure 31.75 mm or smaller steel piping? Silver brazed Screwed Soldered Flared Glued

Screwed

In a refrigeration system controlled by a high pressure float valve, insufficient refrigerant charge will cause: Automatic system shut down. A boost in the compressor Liquid carry-over to the compressor. Starving of the evaporator and reduced cooling capacity. The compressor to run continuously.

Starving of the evaporator and reduced cooling capacity.

Which of the following is an example of a loss of latent heat? Steam condenses Water evaporates Ice melts Refrigerant evaporates Air is cooled

Steam condenses

A compression refrigeration system can be divided into two parts; a high pressure section carrying the head pressure and a low pressure section carrying the _____ pressure: Discharge Back Hot Return Suction

Suction

A chemical dot placed under the lens of a sight glass that is exposed to liquid refrigerant monitors: Liquid flow Refrigerant levels The presence of moisture in the refrigerant Loss of refrigerant Oil in the refrigerant

The presence of moisture in the refrigerant

The standard refrigeration cycle is used to compare refrigerants and machines operating under comparable conditions. These standard conditions are: 1030 kPa and atmospheric pressure 30°C condensing and -15°C evaporating 30 kPa and atmospheric pressure -30°C condensing and 15°C evaporating 30 kPa and atmospheric temperature

30°C condensing and -15°C evaporating

According to CSA B52 code, refrigerant discharge from a pressure relief device to the atmosphere shall not be less _____ from any window, ventilation opening or exit in any building. 4 m 4.6 m 6.5 m 7.6 m 10 m

7.6 m

With regard to the high pressure side, the maximum setting for a pressure limiting device on a refrigeration system shall not exceed the pressure relief device setpoint by: 100% 75% 90% 80% 50%

90%

R-22 refrigerant is: Not miscible with oil. Mostly used in packing plants. Corrosive on copper. Corrosive on aluminum. A heat transferring medium.

A heat transferring medium.

With regard to a refrigeration system pressurestat, which of the following statements is false? The control is connected to the suction line of the compressor. The control consists of a switch actuated through a linkage arrangement connected to a bellows or diaphragm. A pressurestat can be used in conjunction with an automatic expansion valve. When the pressure drops to the minimum allowable the switch acts opposite to a thermostat and opens. A pressurestat cannot be used with a capillary tube.

A pressurestat can be used in conjunction with an automatic expansion valve.

The pressure ratio of a refrigeration compressor can be calculated by dividing the: Discharge gage pressure by the inlet gage pressure. Swept volume of a cylinder by its clearance volume. Absolute inlet pressure by the absolute discharge pressure. Absolute discharge pressure by the absolute inlet pressure, and then multiplying by the number of cylinders. Absolute discharge pressure by the absolute inlet pressure.

Absolute discharge pressure by the absolute inlet pressure.

The net refrigerating effect of a refrigerant is the amount of heat: Discharged by the condenser. Absorbed by the refrigerant in the evaporator. Absorbed by the refrigerant in the condenser. Discharged by the refrigerant in the evaporator. Absorbed by the evaporator.

Absorbed by the refrigerant in the evaporator.

Which of the following statements about the evaporator bypass dampers in a refrigeration system is true? They decrease the resistance to the passage of air when they close. When the face damper is closed, the quantity of air passing over the evaporator coils is at a maximum. The quantity of air passing through the duct depends on the damper position. Multi-speed blowers cannot be used in combination with face and bypass dampers. Actuators are required to provide damper movement.

Actuators are required to provide damper movement.

Which of the following correctly describes the heat transfer that takes place in a simple ice-box? There is a net loss of heat from the system, as the air cools. Air gives up sensible heat; ice does not gain any heat. Air gives up sensible heat; ice gains sensible heat. Air gives up sensible heat; ice gains latent heat of fusion. Air gives up latent heat; ice gains latent heat of condensation.

Air gives up sensible heat; ice gains latent heat of fusion.

A liquid trap located in the suction line before a refrigeration compressor, which evaporates liquid refrigerant and returns it to the compressor as a gas, is called: An oil separator A strainer-drier A distributor An accumulator A stop valve

An accumulator

The accessory that maintains efficient heat transfer by collecting oil that coats the tubes of the condenser is called: Strainer A strainer-drier An oil scrubber A filter An oil separator

An oil separator

Ammonia refrigerants: Have high sensible heat capacity. Mix well with oil. Are very expensive. Are well suited for industrial refrigeration. Are ideally suited to copper piping system.

Are well suited for industrial refrigeration.

The ideal refrigerant should: Have a low latent heat capacity. Have a high boiling point. Have high condensing pressure. Be environmentally friendly. Be easily detected because of its strong odour.

Be environmentally friendly.

The temperature in the evaporator: Depends on pressure in the receiver. Will decrease when the compressor stops. Depends on pressure in the evaporator. Depends on the ambient temperature. Is controlled by the charging valve.

Depends on pressure in the evaporator.

Which of the following is NOT a form of refrigeration evaporator construction? Bare tube Plate surface Shell and tube Finned tube Double-tube

Double-tube

With regard to economizers installed on packaged air-conditioning chillers, which of the following statements is false? Economizers control the flow of liquid refrigerant from the evaporator to the condenser. Liquid refrigerant levels in each chamber are controlled by float operated, valves. The upper float chamber is connected to the bottom of the condenser. The economizer float chamber is connected via the motor to the second stage inlet of the compressor. It is composed of two chambers.

Economizers control the flow of liquid refrigerant from the evaporator to the condenser.

Choose the true statement. The economiser of a packaged water chiller, used for air conditioning, does NOT: Have an intercooling effect on the compressor. Reduce the power required for compression of the refrigerant. Reduce the flash vapour in the evaporator. Increase the refrigerating capacity of a system. Eliminate liquid carryover to the compressor.

Eliminate liquid carryover to the compressor

The refrigerating effect of a refrigerant is: Equal to its latent heat of vaporization. Greater than its latent heat of vaporization. Less than its latent heat of vaporization. Equal to its specific heat capacity. Less than its net-refrigerating effect.

Equal to its latent heat of vaporization.

In a refrigeration system, the liquid refrigerant is changed to a gas in the: Condenser Charging drum Receiver Compressor Evaporator

Evaporator

Moisture in a refrigeration system will not cause: The formation of ice inside the refrigeration system. Acid formation inside the refrigeration system. Corrosion inside the refrigeration system. The deterioration of the motor insulation of a hermetic compressor. Excessive high-side pressures.

Excessive high-side pressures.

The refrigeration evaporator that increases heat exchange by crimping several thin metal plates to single-wall tubes is a: Plate surface evaporator Bare tube evaporator Shell and tube evaporator Finned tube evaporator Double tube

Finned tube evaporator

The refrigeration compressor's operating control that uses a bimetal element is a: Fluid expansion actuating control Pressurestat Humidistatv,Temperature actuated control" Flow switch

Flow switch

In actual systems there will be a gradual pressure drop through each side of the system due to: Entropy. Friction in the evaporator, condenser, and piping. Fractionation of refrigerants. Coefficients of expansion of system components. Bernoulli's principle.

Friction in the evaporator, condenser, and piping.

(4-118-2.01) In many cases, the evaporator pressure of a refrigeration system must not fall below a certain level, in order to prevent: Frosting of coils Evaporator valve lock Tubing collapse Overheating of the evaporator Overheating of the compressor

Frosting of coils

(4-114-1.01) Which of the following characteristics is common in all of the group B refrigerants? High toxicity High flammability Non-toxic but highly flammable Low Toxicity Low flammability

High toxicity

A method of controlling the capacity of reciprocating refrigeration compressors, whereby the discharge of high-pressure refrigerant is re-introduced to the suction side of the compressor, is called: Compressor unloading Cylinder throttling Suction throttling Hot gas bypass Cylinder unloading

Hot gas bypass

An operating control, which consists of a hygroscopic element made of material similar to multiple strands of human hair, is called a: Humidistat Thermostat Fluid expansion regulator Pressurestat Bimetal element

Humidistat

In a refrigeration system, which of the following is NOT a cause of poor condenser performance? Waterside scale accumulation. Oil film accumulation on the inside of the condenser. Accumulations of non-condensable gases in the condenser. Inadequate coolant circulation. Inadequate refrigerant charge.

Inadequate refrigerant charge.

In refrigeration systems, the most common methods used to control the capacity of a reciprocating compressor are: Cylinder bypass and hot gas bypass Intermittent operation and continuous operation Cylinder unloaders and variable speed drives Suction throttling and variable inlet vanes Cylinder unloaders and cylinder bypass

Intermittent operation and continuous operation

The amount of heat absorbed by a refrigerant in the evaporator is equal to its: Latent heat of evaporation. Latent heat of fusion. Latent heat of vaporization minus the heat required to flash the liquid due to the pressure drop. Latent heat of vaporization plus the heat required to flash the liquid due to the pressure drop. Specific heat.

Latent heat of vaporization minus the heat required to flash the liquid due to the pressure drop.

Group "A" refrigerants are: Non-flammable Low-flammable Low-toxic Low-toxic and flammable High-toxic and flammable

Low-toxic

With regard to refrigeration systems, large-capacity air-cooled condensers are found mainly: On roof tops. In indoor mechanical rooms, with ductwork supplying cooling air. In locations where water is plentiful. Where they are protected from the environment. In systems where the high-side pressure does not exceed 103 kPa.

On roof tops.

A controlled amount of high temperature, high pressure liquid refrigerant: Passes through the regulating valve to the evaporator. Passes through the regulating valve to the liquid receiver. Passes through the compressor to the condenser. Evaporates in the evaporator, leaving mostly refrigerant liquid at the evaporator outlet. Occurs in isoenthalpic systems.

Passes through the regulating valve to the evaporator.

Which of the following statements about strainers is false? Strainers prevent foreign particles from damaging compressor valves. Piping must be disconnected to clean the strainer. Hermetic type compressors are equipped with a built-in suction strainer. Strainers typically consist of a fine mesh screen basket. The strainer is installed in the suction line.

Piping must be disconnected to clean the strainer.

In a closed vessel, the boiling point of a liquid can be raised by: Raising the liquid level in the vessel. Lowering the pressure in the vessel. Raising the pressure in the vessel. Lowering the liquid level in the vessel. Raising the temperature in the vessel.

Raising the pressure in the vessel.

The three main classifications of refrigeration compressors are: Scroll, rotary, and positive displacement. Axial, centrifugal, and positive displacement. Centrifugal, dynamic, and positive displacement. Reciprocating, rotary, and centrifugal. Rotary, reciprocating, and lobe.

Reciprocating, rotary, and centrifugal.

The rate at which a refrigeration system will remove heat from the refrigerated medium is defined as: Coefficient of Performance Net cooling coefficient Refrigeration capacity Compression Ratio Differential efficiency

Refrigeration capacity

The expansion valve in a refrigeration system: Expands the liquid to the receiver. Relieves high pressure in the receiver. Regulates the liquid refrigerant flow to the evaporator. Is used to charge the refrigeration system. Isolates the compressor from the condenser.

Regulates the liquid refrigerant flow to the evaporator.

The safety head of a refrigeration compressor is designed to: Unload over-loaded cylinders. Be installed on a hermetic compressor. Relieve pressure due to liquid in the cylinder. Prevent explosion damage. Operate in place of a safety relief valve.

Relieve pressure due to liquid in the cylinder

Which of the following is NOT a function of the refrigeration compressor? Raises the pressure of the refrigerant. Raises the temperature of the refrigerant. Maintains a low pressure in the evaporator. Circulates refrigerant through the system. Removes energy from the vapour.

Removes energy from the vapour.

(4-113-1.02) Heat that causes an increase in temperature, is called _____ heat: Conductive Radiant Sensible Latent Convective

Sensible

The refrigeration condenser design that requires the tubes to be cleaned with acid and then neutralized, is the: Shell and tube condenser Shell and coil condenser Air-cooled condenser Evaporative condensers Baffle condensers

Shell and coil condenser

The oil-pressure failure switches of a mechanical refrigeration system: Keep the compressor oil pressure at a level where the oil will not freeze. Prevent compressor start-up if the oil heater fails. Separate refrigerant dissolved in the oil from the lubricant. Shut down the compressor when the oil pressure drops below the minimum required value. Keep the oil from freezing at low pressure.

Shut down the compressor when the oil pressure drops below the minimum required value.

(4-113-1.08) Refrigerants will evaporate when the: Pressure is increased. Temperature is increased to saturation temperature. They are diluted. Temperature is reduced below saturation temperature. Heat is removed from them.

Temperature is increased to saturation temperature.

With regard to the condenser in a refrigeration system, which of the following statements is true? In the condenser, heat transfers from the cooling medium to the refrigerant. The condensing temperature of the refrigerant vapour is 15°-20°C higher than the temperature of the cooling medium. The condensing temperature of the refrigerant will be lower if the pressure of the refrigerant is increased. The condenser transfers latent heat from the cooling medium and adds it as sensible heat to the refrigerant. The refrigerant absorbs latent heat of condensation from the cooling medium.

The condensing temperature of the refrigerant vapour is 15°-20°C higher than the temperature of the cooling medium.

The amount of water used in the evaporative condenser of a refrigeration plant is only a small percentage of that used in a water condenser of the same capacity, because: Evaporating condensers also use air to cool the refrigerant. The evaporating condensers spray refrigerated water onto condensing coil. The cooling water evaporates, removing far more heat per kilogram of system coolant. Of water conservation methods. Of the scarcity of water in locations that use evaporative condensers.

The cooling water evaporates, removing far more heat per kilogram of system coolant

For a Helical Rotor Design rotary refrigeration compressor, which of the following statements is true? The compressor consists of three opposing grooved rotors. The driving rotor has less helical lobes than the driven rotor has flutes. The vapour is drawn in via the closed space between the driving rotor and the casing. The cylinders around the rotor screws must be considerably larger in diameter than the screws. The compressor is reversible, to allow it to be used in heat pump applications.

The driving rotor has less helical lobes than the driven rotor has flutes.

A refrigeration system circulates warm brine back to a chiller. Which of the following statements about this system is true? The condenser in the system is located in direct contact with the material being refrigerated. The evaporator in the system is located in direct contact with the material being refrigerated. The brine or water is the refrigerant. The evaporator cools the brine. The system is a direct refrigeration system.

The evaporator cools the brine.

(4-115-4.04) Which of the following is not an advantage of a factory assembled, packaged refrigeration unit? Components are designed to match each other. The final installation must be according to code. The unit is equipped with all the required auxiliary equipment. Space requirements are minimized. The unit is factory tested in operation.

The final installation must be according to code.

What will the effect be if insufficient liquid refrigerant is admitted to the evaporator by a thermostatic expansion valve? Insufficient force will be generated against the diaphragm and spring to open the expansion valve. The heat in the vapour leaving the evaporator causes the pressure in the thermal element to increase opening the expansion valve. The room temperature will decrease closing the expansion valve. The thermal element reaches an equilibrium leaving the expansion valve in the same position. The expansion valve will fail to respond.

The heat in the vapour leaving the evaporator causes the pressure in the thermal element to increase opening the expansion valve

Dry and flooded evaporators differ principally in what respect? The dry evaporator is designed to cool gases only. The heat transfer surfaces of a flooded evaporator are kept covered with liquid refrigerant. Flooded systems primarily use B1 and B2 refrigerants. Dry evaporators use low-side floats, whereas flooded evaporators use high-side floats. The drift eliminators in a dry evaporator are considerably smaller.

The heat transfer surfaces of a flooded evaporator are kept covered with liquid refrigerant.

In the evaporator of a refrigeration system: The refrigerant rejects heat to the cooling tower. The refrigerant absorbs heat from the compressor cooling system. The refrigerant absorbs heat from the surrounding medium. The surrounding medium evaporates. The refrigerant is condensed.

The refrigerant absorbs heat from the surrounding medium.

The thermostatic expansion valve operates on the principle of balancing: The volumetric expansion of a fluid against a return spring. Evaporator temperature against a return spring. Condenser pressure against a return spring. Condenser temperature against a return spring. Evaporator pressure against a return spring.

The volumetric expansion of a fluid against a return spring.

The most widely used refrigerant metering device, which consists of a pressure-sensitive bellows or diaphragm connected to a temperature sensing bulb, is a/an: Thermostatic expansion valve Automatic expansion valve Capillary tube Equalizer Constant pressure valve

Thermostatic expansion valve

With regard to their application in refrigeration systems, which of the following statements about flow switches is false? They are used on chilled water systems. They are used as shutdowns or permissives when flow is insufficient. They are operated by the force exerted on a flexible vane immersed in the fluid flowing in the line. They can only be used to regulate liquid flow, not air flow. They can be used to close flow indicator circuits.

They can only be used to regulate liquid flow, not air flow.

Which of the following statements about double tube refrigeration condensers is true? They consist of two separate tubes side by side. They are easy to clean. Water flows in the inner tube in the opposite direction of the flow of refrigerant. They have the highest efficiency of the water-cooled condensers. They have a large cooling capacity combined with a small size.

Water flows in the inner tube in the opposite direction of the flow of refrigerant.