OPTIMIZATION OF PERFORMANCE OF WATER-LITHIUM BROMIDE REFRIGERATION SYSTEM BY SECOND LAW ANALYSIS USING MATLAB

Abstract

The main objective of Vapour Absorption Refrigeration system (VAR) is to produce refrigeration effect by
consuming low grade energy (Heat). The basic components of VAR system are Evaporator, Absorber, Generator,
Solution heat exchanger, Expansion valve, Condenser. Since VAR system is heat operated cycle. The temperatures of
generator, condenser, evaporator and absorber plays crucial role on performance of the VAR system. To investigate
variation of temperatures on each component of VAR system water lithium bromide system is designed for 6.18kW of
Refrigeration effect, based on first law analysis and Second law analysis is going to be carried out on each component to
identify irreversibilities. The attempts to enhance COP and decline irreversibilities of VAR system is going to be done by
optimization of temperatures on generator, condenser, absorber by keeping refrigerating load and evaporator
temperature constant and writing entire procedure of thermodynamic analysis in MAT LAB script. The MAT LAB script
runs on user provided inputs of generator, evaporator, absorber and condenser temperatures to find out optimum
temperatures. After finding out all optimum temperatures the program runs over optimized temperatures (or nearer to
optimum temperatures care should be taken to avoid system entering into crystallization zone). And the component in
VAR cycle having most irreversibilities is identified (i.e. condenser). To Decrease exergy destruction associated with the
condenser to avoid entropy generation in condenser an idea is bring forward to utilize waste heat by placing heat engine.
In most of thermal power plants rankine cycle with working fluid as water is used to generate power. Since in condenser
the availability of heat is at low temperature compared to thermal power plants. A fluid which can be easily evaporated
must be used as working fluid. So refrigerant R-134a is taken as working fluid in rankine cycle. It is placed at condenser
to extract some amount of work which is simply rejecting heat at 90ºC to water at 30ºC. So after the performance
evaluation(from MAT LAB) of simple VAR system along with optimized temperatures and organic rankine cycle at
condenser The results shows that New proposed system will be more efficient than simple VAR system.