CASE-STUDY-OF-LIQUID-SUCTION-HEAT-EXCHANGER-IN.pptx

CASE STUDY OF LIQUID SUCTION HEAT EXCHANGER IN MECHANICAL REFRIGERATION SYSTEM USING ALTERNATIVE REFRIGERANTS.

1. CASE STUDY OF LIQUID SUCTION HEAT EXCHANGER IN MECHANICAL REFRIGERATION SYSTEM USING ALTERNATIVE REFRIGERANTS. PRESENTED BY : coordinated by : Samir Ghorasainee K eshav A charya Sampanna Dhakal Teaching Assistant Sanam Sapkota P urwanchal Campus, Sanchita Sapkota Dharan

2. Mechanical R efrigeration System Mechanical refrigeration, often referred to as refrigeration or air conditioning, is a process by which heat is removed from a location using a human-made heat exchange system . As the refrigerant circulates through the system, it is alternately compressed and expanded, changing its state from a liquid to a vapor.

3. Components of Refrigeration Cycle Evaporator : It absorbs heat from refrigerating space. Compressor : It increases the pressure and temperature of refrigerant through compression. Condenser : It releases the heat into surrounding. Expansion Valve : It decreases the pressure of the refrigerant.

4. Modification of the System Many studies have been done to modify and enhance the performance and energy consumption of the mechanical refrigeration system. Using heat exchanger in the mechanical refrigeration system is one of the effective technique that can be used to improve the energy performance of the system . A LSHX is a counterflow heat exchanger in which the warm refrigerant liquid from the condenser exchanges heat with the cool refrigerant vapor from the evaporator.

5. Modification of the System Refrigerant type can also influence the system performance, so it is a big challenge to obtain matching between the system modification and refrigerant type. The performances of the alternative refrigerants R600a , R134a and R22 while using liquid suction heat exchanger are studied. R600a R22 R134a

6. Model Development The liquid-suction heat exchanger is installed across the suction and liquid lines.

7. Model Development The Liquid Suction Heat Exchanger allows: Subcooling for the condensed refrigerant. R educing the flash gas in the liquid line to ensure maximum capacity for the thermostatic expansion valve. Superheating liquid of refrigerant which is located in the suction line. Prevention of liquid refrigerant entering the reciprocating compressor.

8. Thermodynamics Analysis of Subcooling Fig: P-h diagram of Subcooling Fig: T-s diagram of Subcooling

9. Thermodynamics Analysis of Subcooling Subcooling reduces the flash gas in the liquid line to ensure maximum capacity for the thermostatic expansion valve, which eventually increases the refrigeration effect. It increases the amount of heat rejection from the condenser. It also increases the enthalpy of refrigerant entering the evaporator from 4 to 4’ , which increases the refrigeration effect. The work to be done in the Compressor remains unchanged. Since subcooling increases the refrigeration effect without changing the compressor input, COP of the system can be increased significantly .

10. Thermodynamics Analysis of Subcooling Increases Refrigeration effect Doesn’t change the work input More refrigeration with same work input

11. Thermodynamic Analysis for Superheating Superheating saves compressor from damage by preventing refrigerant liquid droplets that may be flown with the gas from entering the suction line. If superheating of refrigerant takes place due to heat transfer with the refrigerated space then it is called as useful superheating as it increases the refrigeration effect. On the other hand, it is possible for the refrigerant vapor to become superheated by exchanging heat with the surroundings as it flows through the connecting pipelines, which is called as useless superheating .

12. Thermodynamic Analysis for Superheating Fig: P-h diagram of superheating Fig: T-s diagram of superheating

13. Thermodynamic Analysis for Superheating Superheating increases the refrigeration effect of the system. It also increases the work to be supplied to the compressor. Thus, although increasing the refrigeration effect of the system it may or may not increase the COP. The change in COP depends upon the refrigerant used.

14. Results & Conclusion Multiple simulations were run for wide range of conditions. Refrigerants R600a, R134a and R22 were used in the system. Two systems : Non-Modified and Modified with LSHX were examined. All the results were obtained through E ngineering Equation Solver .

15. Effects of Subcooling The liquid-suction heat exchanger improves the sub-cooling for three types of refrigerants; R22, R134a and R600a. However, higher value of the sub-cool temperature was achieved by R600a . Fig : Effect of Liquid-Suction Heat Exchanger on Superheating at Different Condenser Pressure and Different Refrigerants

16. Effects of Superheating The LSHX effectively increased the superheat temperature in the suction line. The f igure also shows that the higher value of the super heat temperature was achieved by R600a and achieved better performance. Fig : Effect of Liquid-Suction Heat Exchanger on Superheating at Different Condenser Pressure and Different Refrigerants

17. Comparison between non-modified and modified system Non-Modified System Modified system The following comparison shows the refrigerant effect at different Condenser pressure and different refrigerants :

18. Comparison between non-modified and modified system Non-Modified System R600a achieved highest value of refrigerant effect Refrigerant Effect : about 250kJ/kg when the condenser pressure was 350 kPa Modified System R600a achieved highest value of refrigerant effect Refrigeration Effect : about 350 kJ/kg when the condenser pressure was 350 kPa

19. Comparison of COP

20. Result & Conclusion The Figure shows that the highest value of COP was achieved by the modified system using R134a. Which is about 7% and 12% higher than that of R600a and R22 respectively. The COP can be improved and enhanced up to 20% based on the refrigerant type and operating conditions while using LSHX. The R600a is good replacement for other refrigerants but it has lower COP compared with R134a due to its thermodynamic properties .

21. Acknowledgement We thank Raid Ahmed Mahmood , School of Mechanical and Electrical Engineering, University of Southern Queensland, Australia for the research.

22. We thank you all for your time and coordination.