In this thesis, three supermarket refrigeration systems are evaluated; two trans-critical DX CO2 systems and one R404A/CO2 cascade system. Field measurements of energy consumption, temperatures, pressures, and compressor motor frequency are made using the computer programs IWMAC and LDS. Calculations are performed using the program Refprop and performance data from the compressor manufacturer. The cooling capacity and coefficient of performance (COP) are calculated and the analysis is made for a period of four months during the summer, June-September 2010, for all systems. The results show that the cascade system has a significantly lower value of COP than the trans-critical CO2 systems. This is due to the unusual design and control of the cascade system. The COP also drops because of the extra temperature levels and pumps present in this system. The use of floating condensation and the fact that no pumps are required for refrigerant circulation is beneficial for the trans-critical systems, resulting in higher COP. The operation of the heat recovery systems is investigated and the results suggest some differences in operation between the two trans-critical systems. The influence of system parasites like pumps and fans on system performance is also investigated for the three systems.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-60884 |
| Date | January 2011 |
| Creators | Kullheim, Johan |
| Publisher | KTH, Energiteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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