Therminol Research Articles

Optical absorption property and photo-thermal conversion performance of Ag@Al2O3 plasmonic nanofluids with Al2O3 nano-shell fabricated by atomic layer deposition

In this paper, Ag@Al2O3 nanoparticles (NPs) were prepared through the atomic layer deposition (ALD) technique with Al2O3 nano-layers serving as anti-corrosion encapsulants. Then, the core-shell structured nano-composites were dispersed into Therminol 66 (TH66) to form oil-based plasmonic nanofluids with mass concentrations varied from 0 to 0.04 wt%. The suspension stability, optical absorption properties and photo-thermal conversion performance of oil-based nanofluids were experimentally tested and evaluated. Besides, the finite difference time domain method was used to simulate the optical absorption of Ag@Al2O3 NPs with different core-shell sizes and volume concentrations. Results demonstrated that the optical absorption capability of oil-based plasmonic nanofluids was enhanced with increasing the nanomaterial concentration. At the approximate optimum concentration of 0.04 wt%, the temperature of plasmonic nanofluid could be increased up to 90.5 °C after an irradiation time of 45 min at the solar intensity of 920 W/m2. The deposition of Al2O3 layer can enhance the optical absorption by intensifying and broadening the absorbance spectras of Ag NPs accompanied by red-shift due to the localized surface plasmon resonance (LSPR) effect. This study provides a promising option to produce plasmonic Ag@Al2O3 nano-composites at large scale for applications in solar thermal energy harvesting.

Improving heat transfer of stabilised thermal oil-based tin nanofluids using biosurfactant and molecular layer deposition

The development of advanced heat transfer fluids (HTF) with enhanced heat transfer properties has been identified as a key target to increase the efficiency of industrial processes. In this work, heat transfer performance improvements of a novel nanofluid, consisting of metallic nanoparticles dispersed in a commercial thermal oil, were investigated. Nanofluids combining tin nanoparticles (1 mass %) with Therminol 66 (TH66) were synthesised using the two step-method and experimentally analysed. The effectiveness of biosurfactant addition and nanoparticle polyethylene terephthalate (PET) nanocoating for high temperature nanofluid stabilisation were independently investigated. The PET nanoscale coatings were grown by molecular layer deposition, which has been used for the first time in this field. The thermal conductivity, dynamic viscosity and specific heat capacity of the stable, oil-based nanofluids were characterised at high temperatures, and the results were compared and in good agreement with models found in the relevant literature. Finally, the heat transfer performance of the nanofluids with respect to their base fluids was evaluated, employing empirical values for the thermophysical properties of the involved materials. In this way, increments of the heat transfer coefficients up to 9.3% at 140 °C, relevant to industrial applications were obtained.

Use of metallic nanoparticles to improve the thermophysical properties of organic heat transfer fluids used in concentrated solar power

One of the approaches to enhance the efficiency, and consequently, reduce costs to produce electricity from concentrated solar power (CSP) is by the development of advanced high temperature heat transfer fluids (HTFs). Incorporation of metallic nanoparticles into conventional heat transfer fluids could significantly improve the thermal transport properties of the HTFs. This study reports on the synthesis and investigation of copper nanoparticles synthesized in-house and dispersed in two synthetic HTFs Therminol 59 (TH59) and Therminol 66 (TH66). Liquid phase reduction of a copper salt was used to produce copper nanoparticles. Suspensions with various copper nanoparticle loadings (0.5–2vol.%) were prepared. Characterizations such as the thermal conductivity, dynamic viscosity, mass specific heat capacity, and fluid stability were performed on the suspensions. Thermal conductivity enhancements over the base fluids were as high as approximately 20% at a 2vol.% particle loading. These enhancements in the thermal conductivity are higher than the predictions based on the Effective Medium Theory (EMT). Dynamic viscosity measurements showed that if good dispersion of nanoparticles is achieved, the composite fluids behave in a Newtonian manner and the dynamic viscosity increases over the base fluid are minor at temperatures 125°C and above. Stability of the suspensions with time was also investigated. Based on the measured properties of the suspensions, a figure of merit for heat transfer was calculated to evaluate the viability of the suspensions.

Nanofluids with encapsulated tin nanoparticles for advanced heat transfer and thermal energy storage

SUMMARY Novel high-temperature heat transfer fluids (HTFs) with incorporated phase change nanomaterials were synthesized and tested for heat transfer and thermal energy storage. The advanced thermal properties were achieved by preparing a nanofluid consisting of core/shell silica encapsulated tin (Sn/SiO2) nanoparticles dispersed in a synthetic HTF Therminol 66 (TH66) at loadings up to 5 vol%. Tin nanoparticles were synthesized by modified polyole reduction method followed by sol–gel silica encapsulation process. The measured increase in thermal conductivity of the nanofluid (~13% at 5 vol%) was in agreement with Maxwell's effective medium theory. Latent heat of phase change during melting of Sn core added ~11% increase to the volumetric thermal energy storage of the nanofluid when cycled in between 100°C and 270°C. The value could be further improved if thermal cycling is conducted in a narrower temperature range. The experimental results demonstrated dual functionality of the engineered nanofluids as desired for Concentrated Solar Power systems. Viscosity and stability of the nanofluids as well as thermal stability of core/shell nanomaterials) were investigated in a wide temperature range to obtain a perspective on any additional pumping power requirements for the nanofluid over the base fluid. Copyright © 2013 John Wiley & Sons, Ltd.

Instant Hot Water Generation System for Domestic Utility in Rural Areas

Hot water is required for bathing and cleaning of utensils in the morning and evening hours in Indian homes. People in rural areas use fossil fuels, cooking gas and rarely electricity for hot water production. Present day solar collectors cannot help in instant hot water generation. A system involving a parabolic trough, an evacuated tube and Therminol D-12 oil is developed and studied for instant hot water generation. The developed system works satisfactorily during low incident solar radiation. Experiments on the developed new system show that Therminol D-12 helps to generate hot water at a temperature of 60°C within 10 minutes of time with low solar radiation.

Kinetics of 4-acetoxybenzoic acid synthesis

High-temperature polymers have found a wide range of uses in recent decades. 4-Acetoxybenzoic acid (PABA) is used as a monomer for the polymerization of one such thermotropic polymer. Information on polycondensation of already prepared PABA is available in the literature. However, information in the literature concerning the kinetics of PABA synthesis by acetylation of 4-hydroxybenzoic acid (PHBA) using acetic anhydride is limited. The reaction between PHBA and acetic anhydride in a carrier solvent, Therminol-66 (T-66), was investigated. Aspects of the global reaction mechanism and the dependence of the reaction rate on acetic anhydride concentration were determined. Nuclear Magnetic Resonance (NMR) spectrometry and gravimetric analysis were used to analyze the samples collected from a 3 l batch reactor. The specific rate constant and the activation energy of the reaction were determined and a rate equation for the reaction suggested.