Role of thermo-physical properties of refrigerant on the thermal performance of a refrigeration system / Sa'adah Ahmad @ Ahmad Sowi

Sa'adah, Ahmad @ Ahmad Sowi (2013) Role of thermo-physical properties of refrigerant on the thermal performance of a refrigeration system / Sa'adah Ahmad @ Ahmad Sowi. Masters thesis, University of Malaya.

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Abstract

The role of thermo properties of pure refrigerant and nanorefrigerant on refrigeration system performance are discussed in the report. The thermo-properties have, in fact, a very important part in designing the most optimum refrigeration system. R134a refrigerant is used in many refrigeration system including domestic refrigerators. Even though R134a refrigerant is widely used in refrigeration system, the research on finding another alternative refrigerant is widely conducted since the global warming potential of R134a is relatively high. Since then, there is rapid development of nanorefrigerant in exchange to the pure refrigerant. The addition of nanoparticles to the refrigerant give significant effect to the themo-performance of the refrigeration system, as it gives improvement in thermo-physical properties and heat transfer properties of the refrigerant. The nanorefrigerant that is used for this study is Al₂O₃/R-134a nanorefrigerant. The relationship between COP (coefficient of performance) and thermal properties of refrigerant R134a and Al₂O₃/R-134a nanorefrigerant are presented in this report. The correlations for each properties are obtained by combining some of the correlations from literature with basic thermodynamic approaches and assumptions. COP correlations are presented in four different equations according to its thermo-properties. COP correlations in term of viscosity is obtained by combining the dimensionless COP correlation from Klein et al. (2000) with Hagen–Poiseuille equation. COP correlations in terms of specific heat and thermal conductivity are obtained by substituting the derived equation from Wen and Ho (2005) into COP equation. COP correlations in terms of density is obtained by combining correlation from Payne and Neal (1995) and Bukac (2004). The Al₂O₃ particles concentration is fixed with 5 vol.% in order to simplify the calculations. Addition of nanoparticles to the refrigerant shows significant effect to the COP as the COP value for Al2O3/R-134a refrigerant is higher than that of R134a refrigerant. From the study, it is concluded that COP of the refrigerant increases with increasing thermal conductivity, specific heat and density, and decreases with increasing viscosity. Therefore, it is proved that research on relationship between thermo-properties and COP is important in order to produce a refrigeration system than can operate at optimum operation (better cooling effect and higher system performance).

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