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REFRIGERATION

SYSTEMS

Refrigeration System

Course: Electric Drive & UtilizationUnit: Refrigeration and Air ConditioningB.Tech Electrical Engg. 6

th

Sem

Refrigeration

The term refrigeration may be defined asthe process of removing heat from asubstance under controlled conditions.It also includes the process of reducingheat & maintaining the temp. of a bodybelow the general temp. of itssurroundings.

Contd….

In other words the refrigeration means acontinued extraction of heat from a bodywhose temp is already below the temp. ofits surroundings.

Refrigeration Cycle

In refrigeration system the heat is beinggenerally pumped from low level to higherone & rejected at that temp.This rejection of heat from low level tohigher level of temp. can only beperformed with the help of external workaccording to second law ofthermodynamics.

Contd….

The total amount of heat being rejected tothe outside body consist of two parts:-- the heat extracted from the body to becooled .- the heat equivalent to the mechanicalwork required for extracting it.

Contd….

A refrigerator is a reverse heat engine runin the reverse direction by means ofexternal aid.Every type of refrigeration system used forproducing cold must have the followingfour basic units:-

Contd….

• Low temp. thermal sink to which the heat

is rejected for cooling the space.

• Means of extracting the heat energy from

the sink, raising its level of temp. beforedelivering it to heat receiver.

• A receiver is a storage to which the heat is

transferred from the high temp., highpressure refrigerant.

Refrigeration Systems

• Vapour compression refrigeration system• Vapour absorption refrigeration system• Thermo electric refrigeration system

Vapour Compression Refrigeration• This is the most important system from the

point of commercial & domestic utility &most practical form of refrigeration.

• The working fluid refrigerant used in this

refrigeration system readily evaporates &condenses or changes alternativelybetween the vapour & liquid phaseswithout leaving the refrigerating plant

Contd….

-^

This system of refrigeration thus act as latentheat pump since its pump its latent heat from thecold body or brine & rejects it or deliver it to theexternal hot body or the cooling medium.

-^

According to the law of thermodynamics , thiscan be done only on the expenditure of energywhich is supplied to the system in the form ofelectrical energy driving the compressor.

Contd….

• Each cycle of operation consists of the

four fundamental changes of state orprocesses:- 

Expansion 

Vaporisation 

Compression 

Condensation

Components of VapourCompression Systems