chapter 01 - refrigeration principles.ppt

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Student CD for Commercial Refrigeration for A/C Technicians Chapter 1 Refrigeration Principles

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Page 1: Chapter 01 - Refrigeration Principles.ppt

Student CD for Commercial Refrigeration for A/C Technicians

Chapter 1

Refrigeration Principles

Page 2: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 2

Chapter 1 Overview

• Temperature ranges of refrigeration• Refrigeration cycle• Relate refrigeration to air conditioning• Relationship between a refrigerant’s pressure

and its temperature• Newer refrigerants used in commercial

refrigeration systems• Relationship between the 4 basic components

of a refrigeration system

Page 3: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 3

Common Space & Product Temperatures

• Air Conditioning = 24° C

• High temperature refrigeration = 12°C

• Medium temperature refrigeration = 2°C

• Low temperature refrigeration = -23°C

• Extra low temperature refrigeration = -32°C

Page 4: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 4

• A compressor + two tanks + metering device is used to illustrate a simple A/C system:

– High pressure stays the same, but . . . • Refrigerant:

1. Temperatures drop as discharge gas cools

2. Condenses as heat is rejected

3. Sub-cools before entering the TEV

– Low pressure stays the same, but . . . • Refrigerant:

1. Temperatures rise as liquid vaporizes and absorbs heat in the evaporator

2. Then the vapor superheats after all refrigerant has evaporated

Simple A/C System

Page 5: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 5

165o

125o

125o

115o

50o

40o

RETURN AIR 75oAMBIENT AIR 95o278psig

69psig

Simple A/C System

105o 40o

40o

175o 60o

Page 6: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 6

• Compare the previous A/C system illustration to the following refrigeration system:– Are the high side pressures and temperatures of

both systems different? Why or why not?– Are the low side pressures and temperatures of

the two systems different? Why or why not?

Simple Medium Temperature Refrigeration System

Page 7: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 7

165o

125o

125o

115o

35o

25o

RETURN AIR 35oAMBIENT AIR 95o278psig

49psig

Simple Medium Temperature Refrigeration System

105o 25o

25o

175o 45o

Page 8: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 8

The following slide is an example of what happens to refrigerant in an A/C system:

• Compressor discharges hot gas

• Gas condenses to liquid, releasing heat

• Metering device lowers pressure

• Refrigerant vaporizes, absorbing heat

• Returns to the compressor

“Standard” A/C Systemwith fixed metering device

Page 9: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 9

AMBIENT AIR 95o

Standard A/C System R-22

RETURN AIR 75o

40º

40º

69psig

278psig

115º

50º

EVAPORATOR

CONDENSER

125º

125º

175º60º

Page 10: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 10

AMBIENT AIR 95o

Standard A/C System R-22

RETURN AIR 75o

40º

40º

69psig

278psig

115º

50º

EVAPORATOR

CONDENSER

125º

125º

175º

Condensing Starts

Sub-Cooled Liquid

Fully Condensed Liquid

Super Heated Vapor

Evaporation Starts

Coil Superheat 10°

60º

Total Superheat 20°

Fully Evaporated

Page 11: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 11

Commercial Refrigeration System with a TEV metering device

Comparing A/C to Refrigeration systems:

• Same ambient, same high side pressures and temperatures

• Lower space temperature, low side pressures and temperatures are lower than those on the A/C system

Page 12: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 12

AMBIENT AIR 95o

Typical Walk-In Refrigerator (R22)

BOX TEMPERATURE 35

25º

25º

50psig

280psig

115º

35º

EVAPORATOR

CONDENSER

125º

125º

175º45º

TEV

Page 13: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 13

AMBIENT AIR 95o

Typical Walk-In Refrigerator (R22)

BOX TEMPERATURE 35

25º

25º

50psig

280psig

115º

35º

EVAPORATOR

CONDENSER

125º

125º

175º45º

TEV

Condensing Starts

Sub-Cooled Liquid

Fully Condensed Liquid

Super Heated Vapor

Evaporation Starts

Coil Superheat 10°

Total Superheat 20°

Fully Evaporated

Page 14: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 14

Current refrigerants used in most new refrigeration systems

• Walk-in refrigerators – R22 and R404A• Walk- in freezers – R404A• Reach-in refrigerators – R22, R404A, 134a• Reach-in freezers – R404A• Note: after 2010, manufacturers will not be

allowed to produce equipment with R22• Note: R404A must be charged in a liquid

state

Page 15: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 15

The Four Basic Components of a Refrigeration System

1. Metering device• Lowers the refrigerant temperature below the space

temperature

2. Evaporator• Absorbs heat as refrigerant evaporates

3. Compressor• Increases the refrigerant temperature above the

ambient temperature

4. Condenser• Rejects heat from the refrigerant as vapor condenses

Page 16: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 16

Basic Components and Piping

Compressor

Metering Device

Condenser

Discharge Line

Liquid Line

Suction Line

Evaporator

Page 17: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 17

Refrigeration System“Baseball Diamond”

• The 4 components can be illustrated in the shape of a baseball diamond

• Half the system is high pressure

• Half the system is low pressure

Page 18: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 18

Basic Components

Low Side High S

ide

“Baseball Diamond”

Compressor

Metering Device

CondenserEvaporator

Disch

arge

LineSuction Line

Liquid Line

Page 19: Chapter 01 - Refrigeration Principles.ppt

Copyright 2006 Thomson Delmar Learning 19