Investigations on the thermal and electrical conductivity of polyethylene glycol-based CuO and ZnO nanofluids
01 Oct 2020-Indian Chemical Engineer (Taylor & Francis)-Vol. 62, Iss: 4, pp 402-412
TL;DR: In this article, three different types of nanofluids were evaluated for their stability using dynamic light scattering and particle morphological study using scanning electron microscopy, and the results showed that they were stable in terms of particle morphology.
Abstract: In this experimental work, three different types of nanofluids were evaluated for their stability using dynamic light scattering and particle morphological study using scanning electron microscopy....
Summary (2 min read)
Jump to: [1. Introduction] – [2.1. Materials] – [2.2. Nanofluids Formulation] – [2.3. Scanning Electron Microscopy] – [2.4. Dynamic Light Scattering] – [2.5. Thermal Conductivity and Electrical Conductivity Meter] – [3. Results and Discussion] and [4. Conclusion]
- Nanofluids have shown various interesting properties, and the distinguishing features offer exceptional potential for different industrial applications, such as electronic, transportation, improve recovery in oil and gas well, industrial cooling applications, nuclear systems cooling, etc.
- They used polyethylene glycol (PEG) and sodium dodecyl sulfate (SDS) as dispersing agents.
- The results show that the enhancement in thermal conductivity is due to the concentration of nanoparticles in the base fluids and also the interaction between the particles.
- The experimental measured values of thermal conductivity were compared with different existing models which were accurately fitted with models.
- Stable nanofluids containing CuO and ZnO nanoparticles were prepared through a two-step method.
- CuO and ZnO nanoparticles were used in this study.
- The CuO nanoparticles were supplied by Sigma-Aldrich with a spherical shape, diameter of <50nm and with purity of >97%.
- The ZnO nanoparticles were purchased from Sigma-Aldrich chemicals with a spherical shape, diameter of <50nm and with purity of >97%.
- Deionized water was used as a base fluid along with PEG and PVP.
- The properties of nanofluids used in this work are summarized in Table 1, which shows the dispersant, nanoparticles used and the concentration of particles.
2.2. Nanofluids Formulation
- The base fluid was mixed with a measured quantity of nanoparticles in a beaker covered with aluminum foil to ensure that there is no evaporation during sonification.
- The polymer was thoroughly dispersed using a magnetic stirrer to avoid lump formation and to get a stable nanofluid system with a polymeric base.
- The beaker containing the sample is submerged in the water.
- For this study, ultrasonication (Crest Ultrasonic, 25 KHz, and 450 W) was performed at high frequency of 25 KHz and 450 W for one hour.
- Sonification time of one hour is employed for all suspensions prepared homogeneously as seen by visual observation.
2.3. Scanning Electron Microscopy
- Topography, morphology, and arrangement of agglomerated particles were observed in the dispersed state using SEM.
- Scanning Electron Microscope (SEM) was used for morphological characterization of nanoparticles, and micrographs of ZnO and CuO nanoparticles were obtained.
2.4. Dynamic Light Scattering
- The Brownian diffusivity of particles is measured using DLS and is related to their size.
- The particle size is measured by illuminating the particles with a laser and analyzing the intensity fluctuations in the scattered light.
- The DLS measurements were carried out using 90 PlusTM Nanoparticle Size Analyzer by Brookhaven Instruments.
- Measurements were made at 90° scattering angle and at 25° C. DLS works on the principle that when the sample is illuminated by a laser beam, the fluctuations of the scattered light are detected at a known scattering angle by a detector.
2.5. Thermal Conductivity and Electrical Conductivity Meter
- The thermal conductivities of the nanofluids prepared in this study have been measured using the transition hot wire method with KD2 pro®.
- The unit was calibrated using standard samples.
- The KS-1 sensor applies a very small amount of heat to the needle, which helps to prevent free convection in liquid samples.
- Thirty seconds are allowed for temperature equilibration before heating starts, after which heat is applied for thirty seconds, and measurements are taken over the full time.
- Electrical conductivity was measured using the PC 700 Eutech ® Instrument.
3. Results and Discussion
- Table 1 shows the combinations of CuO and ZnO nanofluids prepared in this work.
- Figure 1(a) shows ZnO nanofluid preparation with 5 wt% of PVP in water.
- This is based on the overall size of the particles and their agglomerating tendency.
- The extent of increase in thermal conductivity depends upon the nature of the base fluid.
- Figure 6 and Table 3 shows the information on the electrical conductivities of prepared nanofluids and percentage enhancement of the electrical conductivities of these nanofluids over the base fluid, respectively.
- Water-based nanofluids have been formulated, characterized and investigated for thermal and electrical conductivities by dispersing CuO and ZnO nanoparticles, and prepared by a twostep method using PVP as a dispersant.
- The morphology characterization of nanoparticle was performed by using scanning electron microscopy.
- The enhancements in thermal conductivity and electrical conductivity were measured at different concentrations.
- ZnO+PVP+water system shows greater enhancement compared to the other two systems.
- This study has demonstrated the feasibility of formulating stable nanofluids of CuO and ZnO in PEG and provided with the information on thermal and electrical properties of these nanofluid systems, which is not available in the literature.
Did you find this useful? Give us your feedback
Investigations on the Thermal and Electrical Conductivity of Polyethylene
Glycol-based CuO and ZnO Nanofluids
Gas Hydrate and Flow Assurance Laboratory, Department of Ocean Engineering, Indian
Institute of Technology Madras, Chennai- 600036, Tamilnadu, India
Department of Petroleum Engineering, AMET University, kanathur, Chennai 603112
School of Engineering, University of Aberdeen, UK
Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai- 600036,
Jitendra S. Sangwai
In this experimental work, three different types of nanofluids were evaluated for their
stability using dynamic light scattering (DLS) and particle morphological study using scanning
electron microscopy (SEM). The nanofluids used in this study are zinc oxide (ZnO) nanoparticle
in water and 5 wt% polyvinylpyrrolidone (PVP) as a dispersant, and ZnO with polyethylene glycol
(PEG 600) and CuO with PEG 600 with 5wt% PVP at different concentration of 0.1, 0.3 and
0.5wt %. Thermal and electrical conductivities were determined by KD-2 Pro
and PC 700
. The result shows better enhancement in the thermal and electrical conductivity in the
ZnO+PVP+Water system, followed by the CuO+PVP+PEG and ZnO+PEG systems. The highest
percentage enhancement in thermal conductivity found to be 35.5 % of ZnO+ PVP+water systems.
The thermal conductivity results were compared with a theoretical model and show good
agreement with results predicted by the model. The proposed model of Nan et al. (1997) is based
on a hypothesis regarding the physical mechanism in heat transfer for nanofluids. This study is
expected to form the basis for the development of nanoﬂuid-based technologies with PEG as the
primary additive in the upstream oil and gas industry especially in gas hydrates and drilling
Keywords: Electrical conductivity; Nanofluids; Stability; Thermal conductivity; Nan’s model.
Nanofluids have shown various interesting properties, and the distinguishing features offer
exceptional potential for different industrial applications, such as electronic, transportation,
improve recovery in oil and gas well, industrial cooling applications, nuclear systems cooling, etc.
Nanofluids are essentially two-phase systems, viz., solid phase in the liquid phase. Several
industries are in need of a cooling medium to improve the heat transfer performance, and of new
technology to overcome persistent challenges. A solid has a higher thermal conductivity than a
liquid, and hence, to increase the thermal conductivity, nanosized particles suspended in a base
fluid, known as ‘nanofluids’, are used. Nanoparticles have good electrical, magnetic and optical
properties. Accordingly, the mechanism for thermal conductivity enhancement is believed to be
the responsible parameter for enhancing heat transfer in engineering applications. However, the
research on the electrical properties of the nanofluid is very rare. The factors responsible for
enhancing heat transfer of nanofluids are the types of nanoparticle, particle size, aggregation,
Brownian motion of the particles and temperature of the nanofluids. Various mechanisms and
models, based on various assumptions, have been recently developed for explaining the unusually
high thermal conductivity of nanofluids [1-3]. Two significant requirements for measuring the
thermal conductivity are preparation of a homogeneous mixture and long-term stability which can
withsatand the initial equilibrium conditions until measurement. The electrical conductivity of a
suspension depends on the background electrolyte, particle size, charge, and volume fraction [4-
6]. Choi and his group  were the first to report that the suspended particles in the base fluid can
significantly enhance the heat transfer and give rise to improvement in the heat exchange systems.
Yu et al.  studied the thermal conductivity of copper oxide (CuO) nanofluids with ethylene
glycol and polyvinylpyrrolidone (PVP) as dispersants. The results showed about 46%
enhancement in the thermal conductivity in about 0.5 vol% of particle concentration at 50
demonstrated that the temperature and Brownian motion of nanoparticles play an important role
in the thermal conductivity enhancement. Mehrali et al.  showed that by using graphene
nanoplatelets, a stable nanofluid with distilled water could be prepared without surfactant by
ultrasonic probe dispersion technique. The researchers showed about a 28% enhancement in
thermal conductivity and demonstrated that the stability of nanofluids found to be enhanced due
to ultrasonication. These nanofluids can act as an advanced heat transfer fluid in a medium
temperature applications in solar and heat exchangers. Xie et al.  conducted studies using
different nanoparticles, such as silicon carbide (SiC), zinc oxide (ZnO), carbon nanotubes (CNT)
and aluminum oxide (Al
) with base fluids, such as deionized water, glycerol, ethylene glycol
and the mixture of water and ethylene glycol. The results showed that the thermal conductivity
enhancement has been influenced by the volume fraction of the particle and due to temperature.
Fedele et al.  studied CuO, titanium oxide (TiO
) and single-walled carbon nanohorns
(SWCNHs) with water as a base fluid. They used polyethylene glycol (PEG) and sodium dodecyl
sulfate (SDS) as dispersing agents. They investigated three dispersion techniques, such as
sonification, high-pressure homogenization and ball milling for the formation of nanofluids. The
high-pressure homogenization method was found to yield better stability of the nanofluids.
Kole and Dey  prepared stable ZnO-ethylene glycol nanofluids by prolonged
sonification of >62 hours and showed that extended time for sonification gives better
fragmentation and dispersion of the particles. In their studies, they considered both temperature
and nanoparticle concentration for thermal conductivity enhancement. The results showed that
approximately 40% of thermal conductivity enhancement is achieved at 30
C and with 3.75vol%
of ZnO. Suganthi et al.  investigated a colloidal dispersion of ZnO-propylene glycol. Thermal
conductivity was measured in the temperature range of 10-60
C and for various aggregate sizes.
The researchers observed that the thermal conductivity enhancement depends on temperature and
that higher enhancement is possible at a lower temperature. The result shows that the temperature
and aggregation of particles are major factors in the formation of a solvation layer on the ZnO
nanoparticle surfaces. Jeong et al.  showed that for ZnO nanoparticles, the thermal
conductivity and viscosity enhancement depend on the particle shape. The researchers used
spherical and rectangular particles with concentration range of 0.05 to 5 vol%. The results show
about 12% and 18% enhancement in thermal conductivity, respectively, for spherical and
rectangular particles at 5vol%. Moattar and Cegincara  used PEG to prepare stable nanofluids
of ZnO which was later characterized using dynamic light scattering. They observed the effect of
ZnO nanoparticles concentration and temperature on the volumetric and transport properties of the
aqueous solution of PEG but did not report information on enhancement in the thermal and
electrical property. Ponmani et al.  studied experimentally the thermal and electrical
conductivity of ZnO and CuO nanofluids in xanthan gum. They observed an approximately 25 and
50 % enhancement in thermal and electrical conductivity, respectively. White et al. 
investigated the electrical conductivity of propylene glycol-based ZnO nanofluids. The result
showed that a higher volume fraction of the particle gives better enhancement in electrical
conductivity. They observed that for about 7 % volume fraction of nanoparticles, electrical
conductivity showed up to 100-fold increase over the base fluid. Kim et al.  prepared stable
nanofluids using aluminum oxide, zinc oxide and titanium oxide nanoparticles with water and
ethylene glycol as a base. They showed that the enhancement in the thermal conductivity increases
linearly in lesser size of the particles when suspended in the base fluids. Khedkar et al. 
investigated the thermal conductivity of CuO nanofluids in monoethylene glycol and water. The
results show that the enhancement in thermal conductivity is due to the concentration of
TL;DR: In this article, ZnO nanoparticles were synthesized by using Zinc acetate (ZnC4H6O4) and Sodium Hydroxide (NaOH) as the raw materials.
Abstract: Present research work highlighted the synthesis of ZnO Nanoparticles by sonochemical method and its positive effects on enhancement of heat transfer while used as water based nanofluids in a circular tube heat exchanger. ZnO nanoparticles were synthesized by using Zinc acetate (ZnC4H6O4) and Sodium Hydroxide (NaOH) as the raw materials. Proper formation of ZnO nanoparticles were confirmed by XRD, FTIR, FESEM, EDX mapping and UV–vis spectrum characterizations. ZnO nanoparticles were been dispersed in distilled water by uisng high probe sonication and its concentration was varied (0.1%, 0.075%, 0.05% and 0.025%) to study its effect on convective heat transfer (Nusselt number) with the variation of Reynolds number in single tube circular heat exchanger. Positive enhancement in thermal conductivity was observed with the addition of ZnO nanoparticles in the base fluid and studied its performance at 50 °C heat transfer surface temperature and 30 °C bulk temperature of the nanofluids. About 49% increase in Nusselt numbers was observed at 0.1% wt. concentration of ZnO-water based flowing Nano fluid. At the highest Reynolds number (Examined), there was about 50% heat transfer enhancement noticed at 0.1% concentration of ZnO nanofluid. While all other weight % concentrations also showed enhanced heat trasnfer properties as compare to base fluid. The ZnO with distilled water nanofluids gives encourging results for heat trnasfer improvments.
TL;DR: In this paper , a complex experimental study involving PEG 400 enhanced with three kinds of nanoparticles, i.e., Al 2 O 3 , ZnO and MWCNT, was conducted taking into account both the temperature effect on the thermal conductivity, as well as the nanoparticle loading in the base fluid.
Abstract: Polyethylene glycol is intensively studied as the base for new enhanced materials, while PEG 400 enhanced with nanoparticles may be seen as a new heat transfer fluid and its development is on its way. A number of reports were acknowledged in the recent literature, even if this research is ongoing and new hypothesis have to be further tested. This paper deals with a complex experimental study involving PEG 400 enhanced with three kinds of nanoparticles, i.e. Al 2 O 3 , ZnO and MWCNT. A first observation was in regard to a possible synergy between nanoparticle type and base fluid, yet this hypothesis requires to be further proved. The experimental was conducted taking into account both the temperature effect on the thermal conductivity, as well as the nanoparticle loading in the base fluid. Concluding, nanoparticles addition to a base fluid undoubtedly boosts its thermal conductivity, mechanisms being analogous to those demonstrated for all nanofluids. In regard to heating performance, it was perceived that upper nanoparticles concentration changes the heating comportment of the PEG 400. • PEG 400 and PEG 400 based nanofluids thermal conductivity is investigated. • PEG 400 and its nanofluids have no increase in thermal conductivity with temperature. • PEG 400 nanofluids thermal conductivity upsurge with nanoparticle loading. • Relationships based on experimental outcomes were suggested. • Regression for thermal conductivity assessment was inserted.
TL;DR: In this paper, the efficiency of low salinity water injection (LSWI) can be improved with the advent of nanotechnology with the help of nanofluorine nanophotonics.
Abstract: Low salinity water injection (LSWI) has gained popularity recently as a potential enhanced oil recovery (EOR) method. The efficiency of LSWI can be improved with the advent of nanotechnology. Nanof...
TL;DR: Nanofluids are promising heat transfer fluids, which possess superior heat transfer properties compared with those of conventional fluids such as water, ethylene glycol, and engine oil.
Abstract: Nanofluids are promising heat transfer fluids, which possess superior heat transfer properties compared with those of conventional fluids such as water, ethylene glycol, and engine oil. Nanofluids ...
TL;DR: In this paper , the experimental forced convective heat transfer coefficient (HTC) of nanorods (NRs) zinc oxide-ethylene glycol nanofluids (ZnO-EG NFs) in laminar flow was presented.
Abstract: This paper presents the experimental forced convective heat transfer coefficient (HTC) of nanorods (NRs) zinc oxide–ethylene glycol nanofluids (ZnO–EG NFs) in laminar flow. First, ZnO NRs were synthesized using a hydrothermal method that uses zinc acetate dihydrate [Zn(CH3COO)2·2H2O] as a precursor, sodium hydroxide as a reducing agent, and polyvinylpyrrolidone (PVP) as a surfactant. The hydrothermal reaction was performed at 170 °C for 6 h in a Teflon-lined stainless-steel tube autoclave. The sample’s X-ray diffraction (XRD) pattern confirmed the formation of the hexagonal wurtzite phase of ZnO, and transmission electron microscopy (TEM) analysis revealed the NRs of the products with an average aspect ratio (length/diameter) of 2.25. Then, 0.1, 0.2, and 0.3 vol% of ZnO–EG NFs were prepared by adding the required ZnO NRs to 100 mL of EG. After that, time-lapse sedimentation observation, zeta potential (ζ), and ultraviolet-visible (UV–vis) spectroscopy was used to assess the stability of the NFs. Furthermore, the viscosity (μ) and density (ρ) of NFs were measured experimentally as a function of vol% from ambient temperature to 60 °C. Finally, the HTC of NFs was evaluated utilizing a vertical shell and tube heat transfer apparatus and a computer-based data recorder to quantify the forced convective HTC of NFs in laminar flow at Reynolds numbers (Re) of 400, 500, and 600. The obtained results indicate that adding only small amounts of ZnO NRs to EG can significantly increase the HTC, encouraging industrial and other heat management applications.
TL;DR: In this article, the authors investigated the increase of thermal conductivity with temperature for nano fluids with water as base fluid and particles of Al 2 O 3 or CuO as suspension material.
Abstract: Usual heat transfer fluids with suspended ultra fine particles of nanometer size are named as nanofluids, which have opened a new dimension in heat transfer processes. The recent investigations confirm the potential of nanofluids in enhancing heat transfer required for present age technology. The present investigation goes detailed into investigating the increase of thermal conductivity with temperature for nano fluids with water as base fluid and particles of Al 2 O 3 or CuO as suspension material. A temperature oscillation technique is utilized for the measurement of thermal diffusivity and thermal conductivity is calculated from it
"Investigations on the thermal and e..." refers background in this paper
TL;DR: In this article, a methodology is introduced for predicting the effective thermal conductivity of arbitrary particulate composites with interfacial thermal resistance in terms of an effective medium approach combined with the essential concept of Kapitza thermal contact resistance.
Abstract: A methodology is introduced for predicting the effective thermal conductivity of arbitrary particulate composites with interfacial thermal resistance in terms of an effective medium approach combined with the essential concept of Kapitza thermal contact resistance. Results of the present model are compared to existing models and available experimental results. The proposed approach rediscovers the existing theoretical results for simple limiting cases. The comparisons between the predicted and experimental results of particulate diamond reinforced ZnS matrix and cordierite matrix composites and the particulate SiC reinforced Al matrix composite show good agreement. Numerical calculations of these different sets of composites show very interesting predictions concerning the effects of the particle shape and size and the interfacial thermal resistance.
"Investigations on the thermal and e..." refers methods in this paper
TL;DR: In this paper, the Brownian motion of nanoparticles at the molecular and nanoscale level is a key mechanism governing the thermal behavior of nanoparticle-fluid suspensions (nanofluids).
Abstract: We have found that the Brownian motion of nanoparticles at the molecular and nanoscale level is a key mechanism governing the thermal behavior of nanoparticle–fluid suspensions (“nanofluids”). We have devised a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we have discovered a fundamental difference between solid/solid composites and solid/liquid suspensions in size-dependent conductivity. This understanding could lead to design of nanoengineered next-generation coolants with industrial and biomedical applications in high-heat-flux cooling.
"Investigations on the thermal and e..." refers background in this paper
TL;DR: Through an order-of-magnitude analysis of various possible mechanisms, convection caused by the Brownian movement of these nanoparticles is primarily responsible for the enhancement in k of these colloidal nanofluids.
Abstract: Researchers have been perplexed for the past five years with the unusually high thermal conductivity (k) of nanoparticle-laden colloidal solutions (nanofluids). Although various mechanisms and models have been proposed in the literature to explain the high k of these nanofluids, no concrete conclusions have been reached. Through an order-of-magnitude analysis of various possible mechanisms, we show that convection caused by the Brownian movement of these nanoparticles is primarily responsible for the enhancement in k of these colloidal nanofluids.
"Investigations on the thermal and e..." refers background in this paper
TL;DR: A moving particle model developed from the Stokes-Einstein formula explains the temperature effect and predictions from the combined model agree with the experimentally observed values of conductivity enhancement of nanofluids.
Abstract: A comprehensive model has been proposed to account for the large enhancement of thermal conductivity in nanofluids and its strong temperature dependence, which the classical Maxwellian theory has been unable to explain. The dependence of thermal conductivity on particle size, concentration, and temperature has been taken care of simultaneously in our treatment. While the geometrical effect of an increase in surface area with a decrease in particle size, rationalized using a stationary particle model, accounts for the conductivity enhancement, a moving particle model developed from the Stokes-Einstein formula explains the temperature effect. Predictions from the combined model agree with the experimentally observed values of conductivity enhancement of nanofluids.