Performance improvement of vapor compression refrigeration cycle using mixture of R134a and Al2O3 nanoparticles Eed A. Abdel-Hadi1, Sherif H. Taher1, Hany E. Abdelrahman1, Hanaa M. Ahmed1, Said A. Mustafa1  1 Faculty of Engineering-Shobra, Benha University, Cairo, Egypt. Dynamic Light scattering Results and discussion ABSTRACT Dynamic light scattering of the prepared nano fluids was studied to investigate the stability and the distribution of the nanoparticles with in the used oil. Particles distribution was determined from the Brownian motion of suspended particles. Thermal systems like refrigerators and air conditioners consume large amount of electric power, thus several ways of developing energy efficient refrigeration and air conditioning systems with nature friendly refrigerants need to be explored. The rapid advances in nanotechnology have led to emerge a new generation heat transfer fluids called Nano fluid in which addition of nanoparticles to base fluids changes their boiling characteristics. In the present work, the effect of using AL2O3 ∕ Polyol Ester (POE) Nano fluid, on the performance of vapor compression refrigeration cycle with R-143a refrigerant is experimentally investigated. The evaporating heat transfer coefficient has been measured at different mass fractions of Al2O3 ∕ oil ranging from 0.025% to 0.125%, and with nanoparticle of 50 nm particle size. Measurements were performed for heat flux ranged from 53 to 88 kW/m2, and an experimental test rig is designed and constructed here for this purpose. The experimental results indicate that R-134a and Polyol Ester (POE) oil with AL2O3 nanoparticles increase the evaporating heat transfer coefficient. Furthermore, light scattering analysis for the prepared nano fluids was also performed, and Zeta potential values reflect the distribution and the stability of the nanoparticles within the used oil. The particle size is about 50 nm Zeta Potential (z) = 61 which shows that the stability and the distribution of the Nanoparticles within the oil are excellent. Dynamic light scattering spectroscopy CONCLUSIONS The experimental test rig The experimental test rig consists of compressor, fan, cooled condenser, expansion device, and an evaporator. Capillary tube is used as an expansion device. The Evaporator is loaded with water. Service ports are provided at the inlet compressor for charging the refrigerant. The prepared nano fluid was injected into compressor of the system. Every time the system was allowed to stabilize for 15 min. The evaporating heat transfer coefficient has been measured for each mass fraction, and the data obtained were plotted . Preparation of Al2O3∕polyol ester Nano fluid Expermental studies have been conducted to evaluate the performance parameters of vapor compression system with lubricant including nano-particles .the conclusions driived out of the present study are i)the convection heat transfer coefficient increased ii) the R134a refrigerant and POE oil mixture with nanoparticles worked normally iii) the coefficient of performance increases and power consumption decreases Preparation of Al2O3∕POE Nano fluid was prepared by mixing an appropriate amount of Al2O3 nanoparticle with an appropriate amount of POE using magnetic stirrer for 5 minutes, followed by sonication using ultra sonic and room temperature, and for two hours to prevent any clustering of particles in the mixture, and to obtain proper homogenization. Three different samples with different mass fractions of Al2O3 ∕ oil ranging from 0.025% to 0.125%, and with nanoparticle of 50 nm particle size have been prepared. a) Pure oil b) Oil with AL2O3 Nano –particle material after preperation c) AL2O3 Nano –particle material after 1 week