VAPOUR COMPRESSION CYCLE

VAPOUR COMPRESSION CYCLE 

Introduction

The  vapour   compression   cycle   is  the  mostly   widely   used   method   of refrigeration in the modern  application.  Your household  refrigerator,  water cooler, deep  freezer, air-conditioner etc, all run on vapour compression cycle. The cycle is called   as   vapour   compression   cycle,   because   the   vapours   of   refrigerant   are compressed in the compressor of the system to develop the cooling effect.

Working

Here are the various process of vapour compression cycle (refer the figure).

1)  Compression:  The vapours of refrigerants enter the compressor and get compressed to high pressure and high temperature. During this process the entropy   of  the  refrigerant  ideally  remains  constant  and  it  leaves  in super heated state.

           

        2)  Condensation:  The  superheated  refrigerant  then  enters  the  condenser where  it  is cooled  either  by air or water  due to which  its temperature reduces, but  pressure  remains constant  and it gets converted  into liquid state.

             3) Expansion:  The  liquid  refrigerant  then  enters  the  expansion  valve  or throttling valve or capillary tube when sudden expansion of  the refrigerant occurs,   due  to  which  its  temperature  and  pressure  falls  down.  The refrigerant leaves expansion valve or capillary tube in partially liquid state and partially in gaseous state.

             4) Evaporation   or  cooling:  The  partially  liquid  and  partially  gaseous refrigerant  at  very  low  temperature  enters  the  evaporator  where  the substance to be cooled is kept. It is here where the refrigeration effect is produced.  The  refrigerants  absorbs  the  heat  from the  substance to be cooled and gets converted into vapour state.

                                       Fig : Simple VCR System

 Advantages

» Capable  of  large  refrigerating  loads  at  lower  initial purchase and operating cost.

» Very efficient

» Very compact system for small to very large heat loads.

» Cycle can be reversed for heat pump operation.

 Disadvantages

» Parts can wear out.

» Noise

» Potential refrigerant leaks.

» Operates in limited orientation.