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

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Presentation on theme: "Student CD for Commercial Refrigeration for A/C Technicians Chapter 1 Refrigeration Principles."— Presentation transcript:

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

2 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

3 Copyright 2006 Thomson Delmar Learning 3 Common Space & Product Temperatures Air Conditioning = 75° High temperature refrigeration = 55° Medium temperature refrigeration = 35° Low temperature refrigeration = -10° Extra low temperature refrigeration = -25°

4 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

5 Copyright 2006 Thomson Delmar Learning o 125 o 115 o 50 o 40 o RETURN AIR 75 o AMBIENT AIR 95 o 278 psig 69 psig Simple A/C System 105 o 40 o 175 o 60 o

6 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

7 Copyright 2006 Thomson Delmar Learning o 125 o 115 o 35 o 25 o RETURN AIR 35 o AMBIENT AIR 95 o 278 psig 49 psig Simple Medium Temperature Refrigeration System 105 o 25 o 175 o 45 o

8 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 System with fixed metering device

9 Copyright 2006 Thomson Delmar Learning 9 AMBIENT AIR 95 o Standard A/C System R-22 RETURN AIR 75 o 40º 69 psig 278 psig 115º 50º EVAPORATOR CONDENSER 125º 175º 60º

10 Copyright 2006 Thomson Delmar Learning 10 AMBIENT AIR 95 o Standard A/C System R-22 RETURN AIR 75 o 40º 69 psig 278 psig 115º 50º EVAPORATOR CONDENSER 125º 175º Condensing Starts Sub-Cooled Liquid Fully Condensed Liquid Super Heated Vapor Evaporation Starts Coil Superheat 10° 60º Total Superheat 20° Fully Evaporated

11 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

12 Copyright 2006 Thomson Delmar Learning 12 AMBIENT AIR 95 o Typical Walk-In Refrigerator (R22) BOX TEMPERATURE 35  25º 50 psig 280 psig 115º 35º EVAPORATOR CONDENSER 125º 175º 45º TEV

13 Copyright 2006 Thomson Delmar Learning 13 AMBIENT AIR 95 o Typical Walk-In Refrigerator (R22) BOX TEMPERATURE 35  25º 50 psig 280 psig 115º 35º EVAPORATOR CONDENSER 125º 175º 45º TEV Condensing Starts Sub-Cooled Liquid Fully Condensed Liquid Super Heated Vapor Evaporation Starts Coil Superheat 10° Total Superheat 20° Fully Evaporated

14 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

15 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

16 Copyright 2006 Thomson Delmar Learning 16 Basic Components and Piping Compressor Metering Device Condenser Discharge Line Liquid Line Suction Line Evaporator

17 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

18 Copyright 2006 Thomson Delmar Learning 18 Basic Components Low Side High Side “Baseball Diamond” Compressor Metering Device Condenser Evaporator Discharge Line Suction Line Liquid Line

19 Copyright 2006 Thomson Delmar Learning 19


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