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Note for Refrigeration and Air Conditioning - RAC by Dr. Santosh Kumar Nayak

  • Refrigeration and Air Conditioning - RAC
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The main focus of this lecture are:  Importance of selection of suitable refrigerant in a refrigeration system.  Classification of refrigerants.  Refrigerant selection criteria based on thermodynamic, thermophysical, environmental and economic properties.  Designation of refrigerants using numbering system.  Comparison between different refrigerants. 2 SKNAYAK

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At the end of lecture, student should able to:  Know the importance of refrigerant selection.  Differentiate between primary and secondary refrigerants.  Know the various criteria used in selecting refrigerants.  Know the important thermodynamic and environmental properties influencing refrigerant selection.  Write the chemical formula of a refrigerant from its number.  Comparison of different refrigerants and suggest replacements for CFCs and HCFCs. 3 SKNAYAK

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What is Refrigerant?  Refrigerant is the fluid used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure.  Most refrigerants undergo phase changes during heat absorption (evaporation) and heat releasing (condensation).  The thermodynamic efficiency of a refrigeration system depends mainly on its operating temperatures.  However, important practical issues such as the system design, size, initial and operating costs, safety, reliability, and serviceability etc. depend very much on the type of refrigerant selected for a given application.  Due to several environmental issues such as ozone layer depletion, global warming and their relation to the various refrigerants used, the selection of suitable refrigerant has become one of the most important issues in recent times. 4 SKNAYAK

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Continue….  Replacement of an existing refrigerant by a completely new refrigerant, for whatever reason, is an expensive proposition as it may call for several changes in the design and manufacturing of refrigeration systems.  Hence it is very important to understand the issues related to the selection and use of refrigerants. In principle, any fluid can be used as a refrigerant.  Air used in an air cycle refrigeration system can also be considered as a refrigerant.  However, in this lecture the attention is mainly focused on those fluids that can be used as refrigerants in vapor compression refrigeration systems only. 5 SKNAYAK

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