Experimental study on stability and rheological behaviour of hybrid Al2O3-TiO2 Therminol-55 nanofluids for concentrating solar collectors

Experimental study on thermal conductivity of mono and hybrid Al 2 O 3 –TiO 2 nanofluids for concentrating solar collectors

“…As shown in Figure 11, increase in energy levels signifies the substantial part of temperature in enhancing the thermal conductivity of hybrid nanofluid. As reported in previous work, 66 Al 2 O 3 -TiO 2 Therminol-55 hybrid nanofluids possess zeta potential values (ξ) vary from 34.43 mV to 68.5 mV which conforms their stability. Due to the enhanced stability at solid-liquid interface, a crystal-like structure is developed in the liquid surrounding the nanoparticle in a way it can be considered to be a part of nanoparticle.…”

“…Further, it was established that the synergetic effect of Al 2 O 3 and TiO 2 in Therminol‐55 enhances the photothermal conversion. Also, the viscosity changes are minimum at higher temperatures which further strengthens its candidature for use in solar collectors 66 . As discussed in previous sections, with the aim to assess the feasibility of hybrid nanofluids such as one proposed in our previous studies, 65,66 it is essential to study the effect of design variable such as concentration and operating variable such as temperature on the physical and thermal properties of the HNF, of which thermal conductivity is of prime importance.…”

“…This leads to absence of nanoparticles in several areas of suspension and decrease in thermal conductivity is observed. In our previous works, 65,66 it was found that high-concentration TiO 2 nanofluid samples possess less stability which alters the thermal conductivity. The observed thermal conductivity of HNF is maximum among all the three which is due to the collusive result of TiO 2 and Al 2 O 3 nanoparticles.…”

“…The zeta potential vales were much higher immediately after preparation which gradually reduced over a period. 66 The zeta potential values on the 7th day of preparation are shown in Figure 5.…”

“…Also, the viscosity changes are minimum at higher temperatures which further strengthens its candidature for use in solar collectors. 66 As discussed in previous sections, with the aim to assess the feasibility of hybrid nanofluids such as one proposed in our previous studies, 65,66 it is essential to study the effect of design variable such as concentration and operating variable such as temperature on the physical and thermal properties of the HNF, of which thermal conductivity is of prime importance. In this study, an extensive testing protocol has been established and implemented to examine the enhancement of thermal conductivity of Al 2 O 3 -TH-55 NF, TiO 2 -TH-55 NF, and their Al 2 O 3 -TiO 2 -TH-55 HNF.…”