High power consumption of air conditioners and refrigerators is a big problem. Accordingly, many directions for
achieving energy efficient air conditioning and refrigeration systems with environmentally friendly refrigerants
need to be explored to face the depletion energy resources. Vapor compression refrigeration system is one of the
many refrigeration cycles and is the most widespread method for refrigeration, air conditioning and heat pump.
On the other hand, the rapid progress in technology of nanoparticles have led to combine a novel 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 CuO-POE and Al2O3-POE nanolubricant on the flow
boiling heat transfer coefficient (HTC) of R404a refrigerant is experimentally investigated. The experiments have
been carried out at different nanoparticles concentration ranged from 0.20 vol.% to 0.70 vol.% for Al2O3 and from
0.05 vol.% to 0.25 vol.% for CuO, with nanoparticles size of 50-60 nm and at heat flux ranged from 10 to 12
kW/m2. The results showe enhancement in flow boiling heat transfer coefficient (HTC) of R404a with using
Al2O3-POE and CuO-POE nanolubricant. It is found that flow boiling HTC increases with increasing the heat flux
for the tested range. Also, it is noticed that the flow boiling HTC increases with increasing the nanoparticles
concentration in POE oil up to 0.60% by volume for Al2O3 and 0.2 vol.% for CuO then deteriorates.