2. CHAPTER 6
Basic Refrigeration Systems

3. Objectives
Explain how phase changes are used in refrigeration systems to transfer heat.
Describe how phase change is possible through pressure change or the addition or removal of heat.
Summarize the four phases of the compression refrigeration cycle.
Lordan A.C.S. Ltd

4. Courtesy of Sporlan Division - Parker Hannifin Corporation; Danfoss
Objectives
Identify the components that divide the low and high sides of a compression refrigeration system.
Understand the purpose of each of the components in a compression refrigeration system.
Courtesy of Sporlan Division - Parker Hannifin Corporation; Danfoss

5. Introduction to Refrigeration
Purpose of refrigeration
Remove heat from space where it is not wanted
Refrigerant acts like a sponge that is used to soak up and move heat
Refrigerant (like a sponge) expands to absorb and compresses to expel
Goodheart-Willcox Publisher

6. Compression Refrigeration Cycle
Refrigerants
Absorb heat inside refrigerated space
Release heat outside
Refrigerant phase changes
Liquid to vapor absorbs heat
Vapor to liquid expels heat
Goodheart-Willcox Publisher

7. High Side and Low Side Effect of pressure Refrigeration system
High pressure = high temperature for heat rejection
Low pressure = low temperature for heat absorption
Refrigeration system
Low side: heat is absorbed into the system
High side: heat is rejected from the system
Compressor divides low side from the high side
Metering device divides high side from low side

8. Compressor Motor-driven device Squeezes vapor into small volume
High temperature
High pressure
Separates low side from high side
Creates high pressure on the high side
Creates low pressure on the low side
Most expensive and crucial part of system
The “heart” of the system

9. Evaporator and Compressor
Low-pressure liquid refrigerant soaks up heat
Liquid becomes low-pressure vapor
Compressor
Draws in low-pressure vapor
Compression results in high-pressure vapor
Intake Stroke
Compression Stroke
Goodheart-Willcox Publisher

10. Condenser and Metering Device
Temperature difference causes release of heat
High-pressure vapor becomes high-pressure liquid
Metering device
Restricts flow of liquid refrigerant
High-pressure liquid becomes low-pressure liquid
Goodheart-Willcox Publisher

11. Reciprocating Compressor
Provides both suction and compression
Operates using a back-and-forth motion
Goodheart-Willcox Publisher

12. Oil Separation Purpose of oil Oil separator
Lubricate compressor’s mechanical parts
Lubricate motor bearings (hermetic systems)
Oil separator
Contains baffles or screens to collect oil
Prevents excess oil from interfering with operation
Placed between compressor exhaust and condenser

13. Oil Separator
Goodheart-Willcox Publisher

14. Condenser Compressor discharges high-pressure, high-temperature vapor
Vapor travels through discharge line to condenser
Condenser changes all vapor into liquid (removing its latent heat)
Condenser subcools the liquid (removing some sensible heat)
Liquid travels through liquid line to metering device

15. Types of Condensers Air-cooled condensers Water-cooled condensers
Forced-air condenser
Natural-convection (static) condenser
Water-cooled condensers
Shell-and-tube
Shell-and-coil
Tube-within-a-tube
Forced-Air Condenser
Goodheart-Willcox Publisher

16. Liquid Receiver Storage tank for liquid refrigerant
Allows charge to be less critical
Holds most of the refrigerant charge for system servicing
Not used in capillary tube systems
Goodheart-Willcox Publisher

17. Liquid Line Carries liquid refrigerant to metering device
Often made of copper
Connected by brazing or flared fittings
Smaller diameter than the suction line
May be in contact with suction line
Subcools liquid line refrigerant
Reduces chance of flash gas in the liquid line
Superheats suction line refrigerant

18. Liquid Line Filter-Drier
Keeps debris from entering metering device
Removes moisture from refrigerant
Moisture might otherwise freeze and cause obstructions
Moisture can form sludge and acid
Emerson Electric Co.

19. Metering Device Controls flow of refrigerant into the evaporator
Reduces liquid refrigerant from high pressure to low pressure
Located between liquid line and evaporator
Other names
Refrigerant control
Refrigerant flow control
Several different types of metering devices

20. Types of Metering Devices
Fixed orifice
Capillary tube
Thermostatic expansion valve (TXV)
Automatic expansion valve (AXV)
Electronic expansion valve (EEV)
Low-side float (LSF)
High-side float (HSF)
Thermostatic Expansion Valve
Danfoss

21. Process of Evaporation
Warm air passes between evaporator fins
Heat is absorbed by liquid refrigerant
Liquid boils into vapor
Temperature of air flowing over evaporator becomes increasingly colder
Cold air cools the conditioned area

22. Evaporators
Lordan A.C.S. Ltd

23. Emerson Climate Technologies
Accumulator
Captures liquid refrigerant in the suction line
Liquid can damage the compressor
Accumulator holds liquid refrigerant
Not required in most small systems
Emerson Climate Technologies

24. Suction Line Carries refrigerant vapor from evaporator to compressor
Carries superheated vapor with minimal flow resistance
Should slope from evaporator down to compressor
Made of copper tubing
Tubing should be insulated to prevent condensation and the absorption of heat in unconditioned spaces
Refrigerant is superheated (above its saturation point)
Superheated but feels cool

25. Suction Line Filter-Drier
Located between suction line and compressor
Designed for low-pressure use
Protects system from acid and contaminants
Often used temporarily
Emerson Electric Co.