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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 °C/s was attained by Cu-Zn-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.

The current study comprises of the synthesis and characterization of Zn-Al layered double hydroxide (LDH) nanofluid for use as a potential coolant in the steel industry. Coprecipitation method was used in the preparation of Zn-Al LDH nanoparticles by using the nitrate salts of Zn, Al and Na, in the ratio of 2:1:2. The nanofluids were characterized based on their particle size, stability, surface tension, thermal conductivity and viscosity. TEM analysis revealed that the nanoparticles were needle-shaped with an average particle size of 45.61 nm and aspect ratio of 7.3. Different concentrations of the nanofluid, from 40 ppm to 240 ppm, were used to analyze the effect of particle concentration on the enhancement in thermal conductivity and viscosity. Stability analysis of the nanofluid exhibited good results, even without any stabilizer. An optimum cooling rate of 125 °C/s was obtained for a nanofluid concentration of 160 ppm, which is 1.29 times when compared to water.

Synthesis of pristine Cu–Al layered double hydroxide (LDH) nanofluid via one step method and study of its thermal properties are the core essence of the current work. Nitrate salts of Cu, Al and Na were mixed in a particular molar ratio at constant pH to produce desired Cu–Al LDH. Different dispersion techniques were utilized to uniformly disperse Cu-Al LDH in water to obtain Cu–Al LDH nanofluids. Broadly used characterization techniques were implemented to identify and characterize pristine Cu–Al LDH nanoparticle. These techniques were used to determine crystallite size, composition, morphology and characteristics vibration of interlayer anion present in the nanoparticle. The nanofluids were characterized for particle size, cluster size, surface tension and thermal conductivity. Particle size analysis was carried out to confirm the formation of nanofluid. Dynamic light scattering (DLS) method had been employed to measure the clustering tendency of nanofluid. Effect of nanofluid loading on thermal conductivity was studied in depth. Influence of particle size, shape and composition on thermal conductivity of nanofluid had also been selected as an essential topic of investigation. Zeta potential and visual phase separation study were carried out to measure the stability of concerned nanofluid.