Thermal systems such as refrigerators and air conditioners consume large amount of electric power, thus several ways of developing energy efficient refrigeration and air conditioning systems with environmentally friendly refrigerants need to be investigated. On the other hand, the rapid advances in nanotechnology have led to emerge a new generation of heat transfer fluids called nanofluids in which addition of nanoparticles to base fluids changes their heat transfer characteristics. In the present study, the effect of using aluminum oxide (AL2O3) ∕ Polyol Ester oil (POE) nanofluids on the flow boiling heat transfer coefficient of R134a refrigerant was experimentally investigated. The experiments have been performed at different nanoparticles concentration ranged from 0.025 wt.% to 0.125 wt.%, with nanoparticles size of 50-60 nm, and at heat flux ranged from 53 to 88 kWm-2. The experimental results indicated that the addition of POE oil and AL2O3 nanoparticles to the base fluid (R-134a) increases the flow boiling heat transfer coefficient. Furthermore, the stability of the prepared nanofluid samples was investigated by both Ultraviolet-Visible (UV-Vis.) spectrophotometer and dynamic light scattering analysis. The high value of Zeta Potential reflected the good stability of the nanofluid which achieved from the effect of sonication of the nanoparticles within the base oil. |
