Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

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2 Refrigerants It is important to consider the likely operating pressures in both the suction and discharge sides of the system. Ideally, a refrigerant is chosen that will have an evaporating pressure above atmospheric pressure under normal operating conditions, so as to avoid air and moisture being drawn into the system in the event of a leak. Thus, a refrigerant should be chosen with a normal boiling point (NBP) that is lower than the anticipated evaporating temperature. A selected refrigerant should also have a condensing pressure that does not exceed the pressure that the system components are designed for, as this can have safety implications. The capacity and COP are mainly dictated by the design and control of the system itself (compressor, heat exchangers, piping, etc), although the properties of the refrigerant play a part in this. The COP can be affected by the compression ratio (which is dictated by the saturation pressure-temperature characteristic), heat exchanger performance and pressure losses around the system, which are all influenced by latent heat, density, viscosity, thermal conductivity, specific heat. For a given evaporating and condensing temperature, the cooling (or heating) capacity of a system is strongly influenced by the latent heat and density of the gas entering the compressor. For conventional systems, a fairly high critical temperature is preferred (at least 20K above the condensing temperature), unless the system is specially designed for operation near or above the critical temperature, such as with R744 systems. 36
2 Refrigerants Safety characteristics CHAPITRE 2 PAGE 06 According to various international and national safety standards, refrigerants may be allocated one of six safety classifications Refrigerant are classified in terms of two general safety criteria: toxicity and flammability. according to its toxicity and flammability. This classification consists of two alpha-numeric characters (e.g. A2); the capital letter Toxicity: Both acute (short-term) and chronic (long-term) toxicity corresponds to toxicity and the digit to flammability. The toxicity are considered as they affect human safety during handling and classification is determined by a refrigerants’ TLV-TWA, such that servicing with refrigerants, and for occupants in refrigerated or air it may be lower toxicity “A” or higher toxicity “B”. There are no conditioned spaces. The acute-toxicity exposure limit (ATEL) is refrigerants that are non-toxic. the maximum recommended refrigerant concentration intended to reduce the risks of acute toxicity hazards to humans in the event of a refrigerant release. For chronic toxicity, the threshold limit value- The flammability classification may be no flame propagation “1”, lower flammability “2” or higher flammability “3”. time weighted average (TLV-TWA) is the time -weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all These classifications are shown in this table: workers may be repeatedly exposed, day after day, without adverse effect. LOWER TOXITY HIGHER TOXITY Flammability: Refrigerant flammability can A3 affect the safety of people and property mainly during handling and servicing activities, A2 and it influences the design of equipment. The flammability of a refrigerant is judged A1 according to the lower flammability limit (LFL), which is the lowest concentration of the refrigerant mixed in air, required for it to be able to be ignited. Flammability is also considered according to the refrigerants’ heat of combustion (HOC), which is the amount of energy released when it burns. B3 B2 B1 HIGHER FLAMMABILITY LOWER FLAMMABILITY NO - FLAME PROPAGATION Safety Classifications according to ISO 817, EN 378 and ASHRAE 34 standards 37
Page 1 and 2: Manual for Refrigeration Servicing
Page 3 and 4: Introduction When to use the manual
Page 5 and 6: Introduction The Factors affecting
Page 7 and 8: Introduction How to assess conditio
Page 9 and 10: Introduction Characteristics of Sel
Page 11 and 12: Introduction Another form of refere
Page 13 and 14: Introduction Choose your chapter Th
Page 15 and 16: 1 Environmental impact of refrigera
Page 17 and 18: 1 Environmental Impact The ozone la
Page 19 and 20: 1 Environmental Impact RADIATION FR
Page 21 and 22: 1 Environmental Impact The ozone la
Page 23 and 24: 1 Environmental Impact Effects of o
Page 25 and 26: 1 Environmental Impact The greenhou
Page 27 and 28: 1 Environmental Impact Timeline act
Page 29 and 30: 1 Environmental Impact Alternative
Page 31 and 32: 1 Environmental Impact The way forw
Page 33 and 34: 2 Refrigerants 2.1. Section objecti
Page 35: 2 Refrigerants Chemical properties
Page 39 and 40: 2 Refrigerants Types of refrigerant
Page 41 and 42: 2 Refrigerants Those with ozone dep
Page 43 and 44: 2 Refrigerants Those with zero ozon
Page 45 and 46: 2 Refrigerants Carbon dioxide (CO2,
Page 47 and 48: 2 Refrigerants Azeotropic Blends An
Page 49 and 50: 2 Refrigerants Using Refrigerant Bl
Page 51 and 52: 2 Refrigerants Lubricants Today, al
Page 53 and 54: 2 Refrigerants Refrigerants and app
Page 55 and 56: 2 Refrigerants Properties of most c
Page 57 and 58: 3 Refrigerants Content Management M
Page 59 and 60: 3 Refrigerant Management The majori
Page 61 and 62: 3 Refrigerant Management Handling o
Page 63 and 64: 3 Refrigerant Management Recovery c
Page 65 and 66: 3 Refrigerant Management Refrigeran
Page 67 and 68: 3 Refrigerant Management Refrigeran
Page 69 and 70: 3 Refrigerant Management Open Refri
Page 71 and 72: 3 Refrigerant Management CHAPITRE 3
Page 73 and 74: 3 Refrigerant Management Recycling
Page 75 and 76: 3 Refrigerant Management equipment
Page 79 and 80: 3 Refrigerant Management PAGE 22 Ex
Page 83 and 84: 3 Refrigerant Management Further re
Page 85 and 86: Summary This section will provide t
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4 Servicing Practices Moisture Mois
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4 Servicing Practices Non-condensab
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4 Servicing Practices Evacuation A
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4 Servicing Practices 7 - For large
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4 Servicing Practices Pressure unit
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CHAPITRE 4 4PAGE 10 LEAK DETECTION
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4 Servicing Practices Detection met
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4 Servicing Practices CHAPITRE 4 PA
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4 Servicing Practices Volumetric ch
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4 Servicing Practices Electronic ch
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4 Servicing Practices Why charge re
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5 Retrofitting Content General retr
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5 Retrofitting • Upon evaluation
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5 Retrofitting General retrofitting
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5 Retrofitting procedures that you
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5 Retrofitting MVAC retrofitting pr
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5 Retrofitting Although, in general
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5 Retrofitting Further reading UNEP
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6 Summary 6.1. Overview of refriger
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6 Safe Refrigerant Handling Oxygen
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6 Safe Refrigerant Handling The com
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6 Safe Refrigerant Handling • Nev
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6 Safe Refrigerant Handling Safe ha
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6 Safe Refrigerant Handling leak de
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6 Safe Refrigerant Handling • Lea
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6 Safe Refrigerant Handling Storage
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6 Safe Refrigerant Handling Recomme
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6 Safe Refrigerant Handling 3 - Sho
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Glossary Glossary Absolute pressure
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Glossary Fossil fuels Carbon-based
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Glossary hole in late 1985, governm
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Glossary Sealed system A refrigerat
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Acknowledgements Acknowledgements I
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Copyright Copyright © United Natio
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