Experimental study on critical heat flux enhancement and stability of nanofluid containing copper oxide and polypyrrole nanocomposite

• CHF and stability of Polypyrrole (PPy), CuO and CuO-PPy nanofluids were evaluated. • CuO-PPy nanofluid provides higher CHF compared to other nanofluids. • Effect of nanoparticles ratios of synthesized nanocomposite on CHF was investigated. • CHF of the base fluid (deionized water) on the nanoparticle coated heater was measured. In this study, an experimental investigation on stability and critical heat flux (CHF) of three different nanofluids was carried out. Polypyrrole (PPy) and CuO nanoparticles and composites of CuO-PPy (in two methods) were synthesized and characterized by XRD, FTIR, FE-SEM and TEM techniques. Zeta potential analysis showed that the highest and lowest stability belongs to CuO-PPy-α/DW and CuO/DW nanofluids, respectively. For investigating how concentration affects the CHF, the nanofluids were synthesized at 0.01–0.09 wt% of nanoparticles in deionized water . The highest CHF, with an increase of 189 % compared to DW, is related to CuO-PPy- α nanofluid at 0.05 wt%. After passing this optimal concentration, the CHF decreased with concentration. SEM images of wire heater showed that thickness and roughness of the surface in the CuO-PPy-α case is more than other samples. The greater CHF value can be due to more nucleation sites and separate channels for water and air flow. Effect of mass ratio of nanoparticles in the synthesized nanocomposite on CHF has been investigated in three different ratios of CuO to PPy of 50:50, 25:75 and 75:25. The highest CHF belongs to CuO-PPy (50:50), which is 10 % and 13 % more than the nanocomposites of (25:75) and (75:25), respectively.