Evaluation of Thermophysical Properties of Menthol-Based Deep Eutectic Solvent as a Thermal Fluid: Forced Convection and Numerical Studies

Abstract

Concentrated solar power (CSP) is one of the emerging renewable energy technology, where sunlight is concentrated from a large area and is stored in a collector filled with heat-transfer fluid (HTF). The current work reports the synthesis of novel HTF based on menthol-based deep eutectic solvents (DESs). DES consisting of a hydrogen bond acceptor, namely, dl-menthol and a hydrogen bond donor (oleyl alcohol), has been prepared and explored to evaluate its effectiveness as a thermal fluid. The thermal properties, namely, viscosity, density, thermal conductivity (TC), and heat capacity, are measured and compared with both conventional and commercial solvents within the temperature range T = 298.15–353.15 K. The density of DES was found to decrease with increase in temperature, while the rheological measurements suggest a Newtonian fluid with its shear viscosity decreasing exponentially with increasing temperature. The TC of the DES was found to be ∼0.161 W/m K, which decreases linearly with temperature, while a contrary was observed for heat capacity. Further, the performance of these solvents has been evaluated in a forced convective heat-transfer configuration under laminar flow conditions with N Re = 105, 155, and 260. The convective heat-transfer experiments demonstrated the fact that the thermal entrance length of the DES is very large because of its high viscosity and low TC. The convective heat-transfer data, namely, heat-transfer coefficient and Nusselt number, were compared with the in-house AnuPravaha CFD simulator under laminar conditions. From the obtained thermophysical properties, it is confirmed that the synthesized DES can be used as a next-generation heat storage media in the CSP plant.

Comprehensive Assessment on the Use of Boron Nitride-Based Nanofluids Comprising Eutectic Mixtures of Diphenyl Ether and Menthol for Enhanced Thermal Media

“…The DESs or the base fluids used in our study, that is, diphenyl ether + dl -menthol and dl -menthol + oleyl alcohol, will be abbreviated as DES-1 and DES-2, respectively, hereafter. DES-2 as HTF was already reported by the authors without the addition of nanoparticles . The current work includes the computation of the eutectic point of probable DES-1, synthesis of DESs and NDEESs, and their thermophysical characterization.…”

“…Thermophysical properties of phosphonium salt-based DESs and NDDES were also evaluated and have been reported previously . In a recent work, menthol-based DES’s performance was analyzed by measuring basic thermophysical properties and its convective heat transfer coefficient . The experimental findings were further validated by computational fluid dynamics studies.…”

Deep Eutectic Solvents in Solar Energy Technologies

“…For these reasons, P. Dehury et al have published several works investigating different DESs as potential heat transfer fluids in the last three years [ 89 , 90 , 91 , 92 ]. In 2018, they started from the study of a dl -menthol/oleic acid 1:1 DES and, in order to improve the performance, also added different concentrations of nano-Al 2 O 3 (70-nm diameter) to obtain 4 different nanoparticle-dispersed DESs (NDDESs) (0.001, 0.005, 0.0075, 0.01 volume fractions) [ 89 ].…”

“…In a subsequent work in 2019, Dehury studied a similar DES, a dl -menthol/oleyl alcohol 1:1 mixture [ 91 ]. In this case, no nanoparticles were added, and the pure DES was studied, comparing it with the commercially available thermal fluid Therminol VP1 (a combination of diphenyl ether and biphenyl) and the previously published data of the IL N -butyl- N , N , N -trimetylammoniumbis(trifluormethylsulfonyl)imide ([N 4111 ][TF 2 N]) [ 94 ].…”

Deep eutectic solvents (DESs): A short overview of the thermophysical properties and current use as base fluid for heat transfer nanofluids

“…According to the literature review, there are a few theoretical studies in the field of DES-based nanofluids. However, many reports have focused on the analysis of the DES behavior and its characteristics, which are constantly updated [99,[104][105][106][107][108][109][110][111][129][130][131][132][133][134][135][136][137].…”