Effect of surfactant on thermo-physical properties and spray cooling heat transfer performance of Cu-Zn-Al LDH nanofluid

The focus of the present study is to investigate the effect of surfactant addition on thermo-physical properties, stability, and heat transfer performance of Cu-Zn-Al LDH nanofluid. For this purpose, both an anionic (Sodium dodecyl Sulfate (SDS), concentration: 200-800 ppm) and a non-ionic surfactant (Tween 20, concentration: 28-70 ppm) have been used at different concentrations with Cu-Zn-Al LDH nanofluid at a fixed concentration. Among both the surfactants, SDS displayed better compatibility and thermo-physical properties when combined with Cu-Zn-Al LDH nanofluid compared to LDH-Tween 20 combination. The addition of both the surfactants into the nanofluid suspension has led to reduced surface tension and viscosity value which is highly desired for better wettability and improved contact between the coolant and the hot surface. The maximum increment in thermal conductivity value was attained in the case of Cu-Zn-Al LDH at 600 ppm SDS concentration which is 20.9% higher than the water. In terms of stability analysis, the highest zeta potential value of - 52.7 mV was also observed for Cu-Zn-Al LDH at 800 ppm SDS loading. The highest cooling rate of 174.8 degrees C/s was attained by CuZn-Al LDH-SDS (600 ppm) nanofluid which is 30.7% higher than what had been achieved by water based cooling. However, the use of Tween 20 in LDH nanofluid has displayed detrimental impact on poor thermal conductivity, zeta potential, and heat transfer results for the LDH nanofluid.