Shivani S. Chawhan

Bio: Shivani S. Chawhan is an academic researcher from Rashtrasant Tukadoji Maharaj Nagpur University. The author has contributed to research in topics: Nanofluid & Thermal conductivity. The author has an hindex of 4, co-authored 5 publications receiving 49 citations.

Sonochemical preparation of rGO-SnO2 nanocomposite and its nanofluids: Characterization, thermal conductivity, rheological and convective heat transfer investigation

Abstract: In the present study, rGO-SnO2 nanocomposite of different rGO:SnO2 ratio (1:7, 1:8 and 1:10 on mass basis) was synthesized using ultrasonic assisted method. The nanofluid prepared with the use of the rGO-SnO2 nanocomposite dispersed in water was investigated at lab-scale for its application for convective heat transfer using a heat exchanger consisting of a straight tube. The successful formation of the rGO-SnO2 nanocomposite particles was proved through UV/vis spectrophotometry, XRD, Raman spectroscopy and TEM analysis. Further, rGO-SnO2 nanocomposite based nanofluids were prepared using distilled water as the basefluid, varying its volumetric concentration (0.01 to 0.1%). The rGO-SnO2 nanocomposite based nanofluid with 0.07 vol.% concentration (1:7 ratio) exhibited 102.97% enhancement in thermal conductivity at 40℃. Further, rheology of the prepared nanofluids was studied at various concentrations and temperatures. It has been found that the prepared nanofluid exhibits non-Newtonian rheological behaviour. The obtained experimental data were tested with the available viscosity models to find the one that predicts the experimental to an acceptable degree. The influence of volume percent of rGO-SnO2 nanocomposite and Reynolds number over the heat transfer coefficient presented by nanofluid was investigated and was found to be increasing with an increase in the volume % of rGO-SnO2 nanocomposite in it and also with rise in Reynolds number. A 0.01 vol. % rGO-SnO2 nanocomposite based nanofluid with 1:7 rGO-SnO2 mass ratio showed 3671.19 W/m2K heat transfer coefficient at a Reynolds number of 7510 at the exit of the test section. Various other equations and analogies were tested so as to find the one that satisfactorily predicts the experimental Nusselt number.

Synthesis, characterization and heat transfer study of reduced graphene oxide-Al2O3 nanocomposite based nanofluids: Investigation on thermal conductivity and rheology

Abstract: Investigation of thermophysical properties of reduced graphene oxide-Al2O3 (rGO-Al2O3) nanocomposite based nanofluid along with convective heat transfer study and associated pressure drop has been done in the present work. Formation of the rGO-Al2O3 nanocomposite was confirmed with the help of various characterization techniques like UV/Vis, XRD, FTIR, Raman spectroscopy, TEM, Elemental mapping and XPS analysis. Thermal conductivity at different temperatures of various volume % (0.01−0.1%) of the prepared rGO-Al2O3 nanofluid was measured by dispersing and ultrasonicating the nanocomposite in deionized water. Thermal conductivity increased with increase in temperature as well as concentration of the rGO-Al2O3 nanofluid. These nanofluids exhibited non-Newtonian behavior as found from their rheological study. Different viscosity models also were employed to predict the viscosity at a range of applied shear rate (0-2000 s−1). Convective heat transfer study at a wall condition of constant heat flux was done at different concentration and Reynolds number of the rGO-Al2O3 nanofluid. Maximum value of heat transfer coefficient of 5461.602 W/m2℃ was achieved at the exit of test section by using 0.05 vol.% rGO-Al2O3 nanofluid flowing at Reynolds number of 7510.

Intensified Thermal Conductivity and Convective Heat Transfer of Ultrasonically Prepared CuO-Polyaniline Nanocomposite Based Nanofluids in Helical Coil Heat Exchanger

Abstract: In this study, investigation of convective heat transfer enhancement with the use of CuO–Polyaniline (CuO–PANI) nanocomposite basednanofluid inside vertical helically coiled tube heat exchanger was carried out experimentally. In these experiments, the effects of different parameters such as Reynolds number and volume % of CuO–PANI nanocomposite in nanofluid on the heat transfer coefficient of base fluid have been studied. In order to study the effect of CuO–PANI nanocomposite based nanofluid on heat transfer, CuO nanoparticles loaded in PANI were synthesized in the presence of ultrasound assisted environment at different loading concentration of CuO nanoparticles (1, 3 and 5 wt.%). Then the nanofluids were prepared at different concentrations of CuO–PANI nanocomposite using water as a base fluid. The 1 wt.% CuO–PANI nanocomposite was selected for the heat transfer study for nanofluid concentration in the range of 0.05 to 0.3 volume % and Reynolds number range of was 1080 to 2160 (±5). Around 37 % enhancement in the heat transfer coefficient was observed for 0.2 volume % of 1 wt.% CuO–PANI nanocomposite in the base fluid. In addition, significant enhancement in the heat transfer coefficient was observed with an increase in the Reynolds number and percentage loading of CuO nanoparticle in Polyaniline (PANI).

Investigation on thermophysical properties, convective heat transfer and performance evaluation of ultrasonically synthesized Ag-doped TiO2 hybrid nanoparticles based highly stable nanofluid in a minichannel

Abstract: Ag-doped TiO2 hybrid nanoparticles have been synthesized by ultrasonic-assisted method for nanofluid application for heat transfer in minichannel heat exchanger at constant wall temperature condition. Prepared nanoparticles were dispersed in water by ultrasonication to form an extremely stable nanofluid. Thermal conductivity of the nanofluid was found to be 1.84 W/mK at 45 ℃ for nanofluid concentration of 0.25 vol%. The overall heat transfer coefficient increased from 1211.71 to 2727.38 W/m2K as the nanofluid concentration increased form 0.01 vol% to 0.1 vol% at Reynolds number of 3480 ± 3. A new correlation for Nusselt number has been proposed. The pressure drop and friction factor of the nanofluids were also advantageously lesser than that of water. The overall performance of the Ag-doped TiO2 hybrid nanoparticles based nanofluid was assessed by comparing the heat transfer with the pumping power and by determining the entropy generation and thus the Bejan number.

Synthesis and Characterization of Nanofluids: Thermal Conductivity, Electrical Conductivity and Particle Size Distribution

Abstract: A new type of fluid, called nanofluid, has found numerous applications in engineering sector due to its outstanding properties. These are known as suspensions of nano-sized particles in fluids called basefluids. The suspension of these nanoparticles in the basefluid shows significant influence on its physical properties. In view of this, in the present book chapter, the properties of the nanofluid like its thermal conductivity, electrical conductivity and so on have been discussed and the notable studies carried out in the past have been summarized. Several factors that are responsible for the alteration of the properties of nanofluids at varying degrees are identified and discussed in this chapter. Further, these properties contribute to the distinctive applications of nanofluids in various engineering fields, which are reviewed and discussed in this chapter.

Heat transfer enhancement by using nanofluids in forced convection flows

Abstract: The problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water-γAl 2 O 3 and Ethylene Glycol-γAl 2 O 3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol -γAl 2 O 3 nanofluid appears to offer a better heat transfer enhancement than water- γ/Al 2 O 3 ; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered

Highly efficient thermal conductivity of polydimethylsiloxane composites via introducing “Line-Plane”-like hetero-structured fillers

Abstract: Graphite oxide (GO) and cetyltrimethylammonium bromide (CTAB) modified multi-walled carbon nanotubes (m-MWCNTs) are utilized to fabricate “Line-Plane”-like hetero-structured thermally conductive [email protected] fillers by electrostatic self-assembly, which are then introduced into polydimethylsiloxane (PDMS) to fabricate thermally conductive [email protected]/PDMS composites. When the mass ratio of GO to m-MWCNTs is 2:1, [email protected] fillers have optimal morphologies and thermal conductivity contribution. When the mass fraction of [email protected] is 20 wt%, the thermal conductivity coefficient (λ) of [email protected]/PDMS composites reaches 2.10 W/(m·K), 950% higher than that of pure PDMS (0.20 W/(m·K)), which is also superior to the λ of MWCNTs/PDMS (0.68 W/(m·K)), GO/PDMS (1.59 W/(m·K)) and (GO/MWCNTs)/PDMS (1.28 W/(m·K)) composites with the same amount of single or hybrid thermally conductive fillers. Meantime, the [email protected]/PDMS composites also present good thermal conduction stability (average λ after 15 heating-cooling cycles in the temperature of 21 to 100°C is 2.14 W/(m·K)) and thermal stability (heat resistance index is 249.3°C).

Performance evaluation of nanofluids in solar thermal and solar photovoltaic systems: A comprehensive review

Abstract: Nanofluids, due to their superior thermal properties, have immense applications in heat transfer process. In view of this, nanofluids, as working fluids in solar thermal systems, have gained importance. This review emphasizes the properties of nanofluids for solar thermal applications as well as typical nanomaterials and analyses experimental and numerical investigations on solar thermal systems utilizing nanofluids along with typical experimental setups and calculation methods used for determination of the performance of nanofluids in the same. The effect of nanoparticles concentration, flowrate, ambient temperature, solar intensity and inlet temperature on the solar thermal system performance utilizing nanofluids is also discussed. Further, challenges occurring during application of nanofluids in solar thermal systems are specified along with recommendations for scaling up of nanofluid-based solar thermal systems.

A Review on Graphene Derivatives-Based Nanofluids: Investigation on Properties and Heat Transfer Characteristics

Abstract: The fact that some of solid materials with suitable phases possess higher thermal conductivity than liquids gave rise to their utilization in heat transfer processes. Fluids that contain nanopartic...

Performance evaluation of nanofluids in solar thermal and solar photovoltaic systems: A comprehensive review

Abstract: Nanofluids, due to their superior thermal properties, have immense applications in heat transfer process. In view of this, nanofluids, as working fluids in solar thermal systems, have gained importance. This review emphasizes the properties of nanofluids for solar thermal applications as well as typical nanomaterials and analyses experimental and numerical investigations on solar thermal systems utilizing nanofluids along with typical experimental setups and calculation methods used for determination of the performance of nanofluids in the same. The effect of nanoparticles concentration, flowrate, ambient temperature, solar intensity and inlet temperature on the solar thermal system performance utilizing nanofluids is also discussed. Further, challenges occurring during application of nanofluids in solar thermal systems are specified along with recommendations for scaling up of nanofluid-based solar thermal systems. • Superior thermal and optical properties of nanofluids aid in solar applications. • Nanofluids are applicable in solar collectors, PVT systems and solar stills. • Numerical and experimental investigations prove enhanced performance of nanofluids. • Challenges and recommendations for nanofluid application in solar systems are specified.