Industrial Refrigeration

Question 1

How do most refrigeration systems produce cold?

Answer 1

The vapour compression cycle.

Question 2

What is energy?

Answer 2

It is the capacity to do work, and can exist as potential energy, or as kinetic energy.

Question 3

Explain energy conversion

Answer 3

In a refrigeration cycle, electrical energy is brought in, which is converted to mechanical energy through a motor then produces heat energy as it is running.

Question 4

When one form of energy disappears, what happens?

Answer 4

Another form of energy appears. Energy can not be created or destroyed.

Question 5

What is latent heat of vaporization?

Answer 5

The quantity of heat required to completely vaporize 1kg of a liquid. The reverse process is called latent heat of condensation.

Question 6

How does a pressure increase change the boiling point of a liquid?

Answer 6

As the pressure increases, a higher temperature is required.

Question 7

Compressing a vapour does what ?

Answer 7

It increases its pressure, and temperature.

Question 8

What are the boiling points of propane, and ammonia?

Answer 8

Propane boils at -42°C Ammonia boils at -33°C At atmospheric pressure.

Question 9

What components are on the high pressure side and low pressure side?

Answer 9

The low pressure side starts from the outlet of the metering device and continues as the refrigerant flows to the inlet of the compressor through the evaporator. high-pressure side starts on the inlet of the compressor through the condenser and back to the inlet of the metering device.

Question 10

What is the vapour compression cycle?

Answer 10

• Evaporator
• Compression,
• Condenser,
• Metering device (expansion chamber)

Question 11

What is superheating

Answer 11

The addition of heat to a vapour, which elevates the temperature higher than the boiling point

Question 12

What is sub cooling?

Answer 12

The removal of heat from a saturated liquid.

Question 13

What must be available for a liquid to vaporize?

Answer 13

Heat.

Question 14

What is the compressors function?

Answer 14

It is a vapour pump, and is the prime mover of the refrigerant

Question 15

What is the condensers primary function?

Answer 15

To reject the heat from the circuit.

Question 16

What are the three (3) types of condensers?

Answer 16

• Air cooled
• Water cooled
• Evaporative condenser.

Question 17

Out of the three (3) condensers which is the most effective?

Answer 17

Water Cooled Condencer.

Question 18

What are the two types of water cooled condensers?

Answer 18

• Waste Water System
• Recirculated System.

NOTE: If a recirculated system is used, a cooling tower must be used.

Question 19

What is an evaporative condenser?

Answer 19

Much like a cooling tower., it uses both water and air to cool the refrigerant.

Question 20

What is the metering device?

Answer 20

It is used as a pressure reducer. They are basically an adjustable flow restrictor.

Question 21

What are the different types evaporators?

Answer 21

• Frosting Or Non Frosting,
• Liquid Type Or Air Type.

NOTE: These are decided by what they cool (air or liquid)

Question 22

What is the designation for copper piping used for refrigeration system

Answer 22

ACR tubing, and it is sized by the ID.

Question 23

What systems cannot use copper tubing?

Answer 23

Ammonia and propane systems

Question 24

What are the typical applications for ammonia and propane systems

Answer 24

• Propane is used in natural gas processes.

* Ammonia is used in larger buildings.

Question 25

If liquid ammonia is splashed on your skin or clothing, what is the procedure?

Answer 25

Do not remove clothing, but try to hold it away from your skin. Gradually flush area with cool water slowly get it warmer.

Question 26

What is moisture in a refrigeration system?

Answer 26

It is a contaminant. It will freeze inside the system.

Question 27

What lubricates the compressor?

Answer 27

There is a small amount of oil that is in the refrigeration circuit.

Question 28

Where are oil separator always used?

Answer 28

Always in ammonia systems, because oil and ammonia are not mixable.

Question 29

What is the primary function of a chilled water circuit?

Answer 29

They are used on larger air conditioning systems.

Question 30

What is a centrifugal compressor vulnerable to in a chilled water circuit?

Answer 30

It is vulnerable to surging.

Question 31

What refrigerant is used typically in a chilled water circuit?

Answer 31

R-22 or R-134a

Question 32

What is a liquid over feed system?

Answer 32

It is where more refrigerant is pumped into the system than is needed. At the exit over the evaporator, some of the refrigerant is still a liquid.

Question 33

If some of the refrigerant is still a liquid after the evaporator, where does it go?

Answer 33

It flows into a low pressure, or low side receiver. | Because you can not have fluids flow into the compressor.

Question 34

What is the benefit of the liquid over feed system?

Answer 34

It ensures all heat transfer is latent transfer, it reacts quickly to high demand changes, it is easily modified, putting more evaporators in the circuit, or removing them quickly.

Question 35

How is defrosting of the evaporators done in a liquid over feed system?

Answer 35

Sometimes they use electric heaters, ,but because plenty of hot vapours are available they sometimes use those hot vapours or Hot Gas.

Question 36

Describe a flooded refrigeration system

Answer 36

It is the type that is used in hockey arenas. It has two separate systems, one for the refrigerant and one for the brine

Question 37

Why do they call it a flooded refrigeration system?

Answer 37

Because the brine is completely immersed or flooded in the refrigerant. It uses a shell and tube system for the two solutions.

Question 38

What must a flooded refrigeration system have to prevent fluids from entering the compressor?

Answer 38

They must have a surge tank.

Question 39

What is the primary system and what is the secondary system of a flooded refrigeration system?

Answer 39

* Primary System-Ammonia | * Secondary System-Brine

Question 40

What are two safety systems or features to keep public safe using this system?

Answer 40

The brine tank is vented so if any ammonia gets in there, it will go out the vent. If there is a fire, a button can be pushed to vent the pressurized ammonia out the top of the building, from the sealed ammonia compressor room

Question 41

What is an absorption refrigeration circuit also known as?

Answer 41

Lithium bromide system

Question 42

Where are absorption circuits used?

Answer 42

They were used in high volumes buildings such as hospitals. They are seldom used now

Question 43

How many separate circuits are in a absorption circuit?

Answer 43

* Chilled water circuit * Cooling tower circuit * Refrigerant water circuit

Question 44

Where is the compressor in an absorption refrigeration circuit?

Answer 44

"There is no compressor" NOTE: Heat energy is used instead. The lithium bromide absorbs the moisture, and when it becomes saturated, it goes through a steam generator to charge it again

Question 45

Why is the absorption method tough to maintain?

Answer 45

Because the entire absorption system must be kept gas tight.

Question 46

What must a flooded refrigeration system have to prevent fluids from entering the compressor?

Answer 46

They must have a surge tank.