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Formulation, Stability Analysis And Characterization Of Boric
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ScienceDirect Materials Today: Proceedings 18 (2019) 4334–4340
www.materialstoday.com/proceedings
ICMPC_2019
Formulation, Stability Analysis And Characterization Of Boric Acid Based Engine Oil Nanofluid For Heat Transfer And Tribological Application In Diesel Engines Sangharatna Ramtekea*, Raghuram Maddinenib, H.Chelladuraic abc
PDPM Indian Institute of Information Technology, Design and Manufacturing, Jabalpur (MP) India.
Abstract In the current research work, different concentration of boric acid based engine oil nanofluids has been prepared by using the two-step technique. The distinctive mass concentration of boric acid nanoparticles such as 0.5 wt%, 0.75 wt%, and 1 wt% has been prepared by dispersing in the engine oil 20W40 using magnetic stirrer and ultrasonication bath. The prepared nanofluid has been characterized by using UV-spectroscopy and Thermal Gravimetric Analysis (TGA) for dispersion stability and thermal stability analysis respectively. The boric acid nanoparticles are additionally characterized by using X-ray diffractometer (XRD) for phase, unit cell, and size identification. The scanning electron microscopy (SEM) has been done for its morphology and nanofluid dispersion analysis. The UV spectroscopy analysis reveals that 0.75 wt% boric acid nanofluid shows stable and homogeneous dispersion stability. The TGA analysis shows that thermal stability of 0.75 wt% nanofluid is superior to base oil SAE 20W40 which indicates its utilization in heat transfer applications. The XRD analysis indicates that the nanoparticles are crystalline in nature and belongs to the boric acid phase only with a mean particle size of 49 nm. The SEM analysis shows that boric acid nanoparticles are spherical in nature and show agglomerated nature. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization. Keywords: Boric acid; stability; UV-spectroscopy; TGA; XRD; SEM; Nanofluid.
1. Introduction The term nanoparticles came into existence in the late 20th century and have then become an area with a wide scope of research in the fields almost all fields such as tribology, heat transfer, and drug delivery. Fluids which contain nano-sized particles generally named as nanofluid [1]. Nanofluid was first introduced by Choi [2] in his efforts to enhance the thermal conductivity of fluids. * Corresponding author. E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization.
S. Ramteke et al./ Materials Today: Proceedings 18 (2019) 4334–4340
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The various molecular level mechanisms such as interfacial liquid layering, particle clustering and micro convection induced Brownian motion can be attributed to the higher thermal conductivity of nanofluids [3]. A nanofluid is a solution containing metallic or non-metallic or nanofibers that are less than 100 nm in size in a base liquid [4–8]. Stability of dispersion plays a vital role in the thermal conductivity of nanofluid [9]. Poor stability and dispersion cause agglomeration and sedimentation thus reducing the effects of nanoparticles in the solution. Aggregation also affects the physical properties of the nanofluid such as viscosity, thermal conductivity and pH [3, 10, 11]. Nanofluids can be prepared by using both one step and two-step methods. However, two-step methods are widely used by researchers compared to the one-step method. Two-step methods mainly comprise mechanical agitation, magnetic stirring, and ultrasonication. Dispersants are added thereafter in case of agglomeration even after ultrasonication because of difference in the interface of nanoparticles and base fluids [12]. Characterization tests help in determining the morphological properties and also dispersion stability of nanofluid. The most common characterization tests are Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The microscopy tests are used to determine the morphology, FTIR is used to obtain the infrared spectrum of solid, liquid and gaseous samples whereas XRD is for phase identification of crystalline material. This article presents the formulation of nanofluid by dispersing nanoparticles in a base oil SAE 20W40 by means of magnetic stirring and ultrasonication in the presence of oleic acid acting as a dispersant. The dispersion stability of the nanofluid is investigated by UV-spectroscopy and the thermal stability by TGA analysis. XRD analysis is done to obtain the unit cell measurement and size of nanoparticles and SEM analysis is done to verify the morphology. 2. Experimentation 2.1. Material The material selected for the present study is boric acid nanoparticles. It has excellent tribological properties. The base oil SAE 20W40 were purchased from a commercial supplier. The physical properties of boric acid nanoparticles and base oil are shown in Tables. 1 and 2 respectively. Table 1. Boric acid nanoparticles physical properties Parameters
Characteristics
Purity
99.99 %
Average particle size
≤ 100 nm
True Density
2.32 gm/cm3
Melting point
170.9 deg C
Appearance
White
Table 2. Diesel engine oil 20W40 properties Parameters
Characteristics
Viscosity @ 400C
121 cSt
Viscosity @ 1000C
12-14 cSt
Viscosity Index
118
Pour Point
30 deg C
Flash point
238 deg C
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2.2. Formulation of nanofluid The different mass concentration of nanoparticles was dispersed in the base oil and allowed to stir on the magnetic stirrer for the period of 10 hours at 900 RPM. Adequate quantity of oleic acid has also been added in the nanofluid for proper dispersion of nanoparticles in the base fluid as it acts as a surface modifier. After that, the resulting nanofluid was treated in ultrasonication bath for the period of 1 hour in the temperature range of 30 0C to 40 0C. The stable mixture of nanofluid is shown in Fig. 1. The procedure for the formulation of nanofluid is shown in Fig. 2. An ultrasonic bath is used for obtaining a homogeneous and stable solution of nanoparticles and base oil.
Fig. 1. Stable and homogeneous mixture of boric acid nanofluid.
Fig. 2. Procedure for nanofluid formulation.
3. Results and discussions 3.1. Dispersion stability analysis using UV-spectroscopy The UV-spectroscopy analysis of boric acid based nanofluid and base oil SAE 20W40 has been done using SHIMADZU UV-1800. The consequences of the spectroscopic analysis as shown in Fig. 3 indicates that base fluid is stable up to the wavelength of 540 nm and gives the absorbance value of 0.15 (a.u) whereas the boric acid based nanofluid shows wavelength shift up to 590 nm and gives stronger absorbance value as compared to the base oil. From Fig. 3 it is also noticed that 0.75 wt% boric acid nanofluid has stronger absorbance value of 0.77 (a.u). Higher the absorbance value, more stable and homogeneous will be the nanofluid. Therefore, 0.75 wt% boric acid nanofluid is homogeneous and more stable.
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Fig. 3. UV-Spectrocopy analysis of different concentration of H3BO3 nanofluid.
3.2. Thermal stability analysis using TGA The thermal stability analysis of boric acid based nanofluid and base oil SAE 20W40 has been conveyed with Mettler Toledo TGA/DSCI Star System. The temperature for the analysis has been ranged from room temperature i.e., 25 0C to 800 0C with a constant heating rate of 10 0C/min. The consequences of TGA analysis has been depicted in Fig. 4. It was seen from the analysis that the thermal stability of boric acid based nanofluid has been enhanced due to the presence of boric acid nanoparticles as compared to base oil. This shows that boric acid nanoparticles are effective for heat transfer applications.
Fig. 4. TGA analysis of 20W40 and 0.75 wt% H3BO3 nanofluid.
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3.3. X-ray diffraction (XRD) of H3BO3 nanopartilces The XRD analysis for H3BO3 nanoparticles is done with Brukers 2nd generation D2 phase x-ray diffractometer with copper Kα radiation of wavelength 1.5406 A. Fig .5 shows the XRD pattern of H3BO3 nanoparticles. Their sample consists of pure H3BO3 nanoparticles which are indicated by the diffracted peaks. Unit cell dimension for each diffracted peak are found to be 5.96, 4.77, 4.59, 4.20, 4.05, 3.17, 2.93, 2.84, 2.64, 2.56, 2.50, 2.24, 2.16, 2.09, 1.59 corresponding to 14.830, 18.580, 19.290, 21.120, 21.890, 28.050, 30.410, 31.450, 33.830, 34.980, 35.860, 40.190, 41.590, 43.100, 57.760 2θ angles. The mean crystallite size is determined by Debye-Scherrer's equation as 49 nm which is given below,
D = kλ / a cos θ
(1)
Where D is the mean size of the crystalline material, k is a shape factor whose value is generally considered as unity, ࣅ is a wavelength and a is the full-width half maxima (FWHM) which can be obtained from diffracted peaks. 3.4. SEM analysis of boric acid nanoparticles and 0.75 wt% nanofluid The SEM analysis of H3BO3 nanoparticles and 0.75 wt% nanofluid is shown in Fig. 6. Fig. 6 (a) and (b) indicate that the morphology of H3BO3 nanoparticles is spherical in nature. The agglomeration of these particles is because of the high surface area to volume ratio. The dispersion of nanoparticles in base oil is uniform and doesn’t shows any agglomeration as shown in Fig. 6 (c).
Fig. 5. X-ray diffraction pattern for H3BO3 nanoparticles.
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Fig. 6. SEM images of H3BO3 nanoparticles (a) At low amplification (b) At high amplification (c) 0.75 wt% H3BO3 nanofluid.
4. Conclusion In the present study, different concentration of boric acid nanofluid has been prepared and characterized by UVspectroscopy and TGA for dispersion and thermal stability analysis, respectively. The 0.75 wt% boric acid nanofluid found to be more stable and well dispersed by UV-spectroscopy analysis. The thermal stability of 0.75 wt% boric acid nanofluid is found to be superior to base oil 20W40 which indicates its suitability for heat transfer and tribological application in diesel engines. XRD analysis indicates good crystalline and pure nature of boric acid nanoparticles. The average particles size is found to be 49 nm by Scherrer’s equation. The morphology of boric acid nanoparticles by SEM indicates that the nanoparticles are spherical in shape and found well dispersed in a base fluid. Acknowledgements The authors would like to thank St.Alloysius College, Jabalpur for providing facilities for XRD and UVspectroscopy analysis also Indian Institute of Technology, Indore for TGA analysis. References [1] [2] [3] [4] [5] [6] [7]
Sidik, Nor Azwadi Che, Syahrullail Samion, Javad Ghaderian, and Muhammad Noor Afiq Witri Muhammad Yazid. "Recent progress on the application of nanofluids in minimum quantity lubrication machining: A review." International Journal of Heat and Mass Transfer 108 (2017): 79-89.S.U.S. Choi, Enhancing thermal conductivity of fluids with nanoparticles, ASME Fed 231 (1995) 99–105. Suganthi, K. S., and K. S. Rajan. "Metal oxide nanofluids: Review of formulation, thermo-physical properties, mechanisms, and heat transfer performance." Renewable and Sustainable Energy Reviews 76 (2017): 226-255. Sidik, NA Che, and O. Adnan Alawi. "Computational investigations on heat transfer enhancement using nanorefrigerants." J. Adv. Res. Des. 1, no. 1 (2014): 35-41. Azwadi, CS Nor, I. M. Adamu, and M. M. Jamil. "Preparation methods and thermal performance of hybrid nanofluids." J. Adv. Rev. Sci. Res. 24, no. 1 (2016): 13-23. Soleimani, Soheil, M. Sheikholeslami, D. D. Ganji, and M. Gorji-Bandpay. "Natural convection heat transfer in a nanofluid filled semi-annulus enclosure." International Communications in Heat and Mass Transfer 39, no. 4 (2012): 565-574. Mohammed, H. A., O. A. Alawi, and NA Che Sidik. "Mixed convective nanofluids flow in a channel having forward-facing step with baffle." J. Adv. Res. Appl. Mech. 24 (2016): 1-21. Zainal, S., C. Tan, C. Sian, and T. Siang. "ANSYS simulation for Ag/HEG hybrid nanofluid in turbulent circular pipe." J. Adv. Res. Appl. Mech. 23, no. 1 (2016): 20-35.
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[8]
Zawrah, M. F., R. M. Khattab, L. G. Girgis, H. El Daidamony, and Rehab E. Abdel Aziz. "Stability and electrical conductivity of water-base Al2O3 nanofluids for different applications." HBRC Journal 12, no. 3 (2016): 227-234. [9] Hong, K. S., Tae-Keun Hong, and Ho-Soon Yang. "Thermal conductivity of Fe nanofluids depending on the cluster size of nanoparticles." Applied Physics Letters 88, no. 3 (2006): 031901. [10] Wang, Xian-ju, Xinfang Li, and Shuo Yang. "Influence of pH and SDBS on the stability and thermal conductivity of nanofluids." Energy & Fuels 23, no. 5 (2009): 2684-2689. [11] Zawrah, M.F., Khattab, R.M., Girgis, L.G., El Daidamony, H. and Aziz, R.E.A., 2016. Stability and electrical conductivity of waterbase Al2O3 nanofluids for different applications. HBRC Journal, 12(3), pp.227-234. [12] Laad, Meena, and Vijay Kumar S. Jatti. "Titanium oxide nanoparticles as additives in engine oil." Journal of King Saud UniversityEngineering Sciences 30, no. 2 (2018): 116-122. [13] Tripathi, Anand Kumar, and Ravikrishnan Vinu. "Characterization of thermal stability of synthetic and semi-synthetic engine oils." Lubricants 3, no. 1 (2015): 54-79.
ScienceDirect Materials Today: Proceedings 18 (2019) 4334–4340
www.materialstoday.com/proceedings
ICMPC_2019
Formulation, Stability Analysis And Characterization Of Boric Acid Based Engine Oil Nanofluid For Heat Transfer And Tribological Application In Diesel Engines Sangharatna Ramtekea*, Raghuram Maddinenib, H.Chelladuraic abc
PDPM Indian Institute of Information Technology, Design and Manufacturing, Jabalpur (MP) India.
Abstract In the current research work, different concentration of boric acid based engine oil nanofluids has been prepared by using the two-step technique. The distinctive mass concentration of boric acid nanoparticles such as 0.5 wt%, 0.75 wt%, and 1 wt% has been prepared by dispersing in the engine oil 20W40 using magnetic stirrer and ultrasonication bath. The prepared nanofluid has been characterized by using UV-spectroscopy and Thermal Gravimetric Analysis (TGA) for dispersion stability and thermal stability analysis respectively. The boric acid nanoparticles are additionally characterized by using X-ray diffractometer (XRD) for phase, unit cell, and size identification. The scanning electron microscopy (SEM) has been done for its morphology and nanofluid dispersion analysis. The UV spectroscopy analysis reveals that 0.75 wt% boric acid nanofluid shows stable and homogeneous dispersion stability. The TGA analysis shows that thermal stability of 0.75 wt% nanofluid is superior to base oil SAE 20W40 which indicates its utilization in heat transfer applications. The XRD analysis indicates that the nanoparticles are crystalline in nature and belongs to the boric acid phase only with a mean particle size of 49 nm. The SEM analysis shows that boric acid nanoparticles are spherical in nature and show agglomerated nature. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization. Keywords: Boric acid; stability; UV-spectroscopy; TGA; XRD; SEM; Nanofluid.
1. Introduction The term nanoparticles came into existence in the late 20th century and have then become an area with a wide scope of research in the fields almost all fields such as tribology, heat transfer, and drug delivery. Fluids which contain nano-sized particles generally named as nanofluid [1]. Nanofluid was first introduced by Choi [2] in his efforts to enhance the thermal conductivity of fluids. * Corresponding author. E-mail address: [email protected]
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization.
S. Ramteke et al./ Materials Today: Proceedings 18 (2019) 4334–4340
4335
The various molecular level mechanisms such as interfacial liquid layering, particle clustering and micro convection induced Brownian motion can be attributed to the higher thermal conductivity of nanofluids [3]. A nanofluid is a solution containing metallic or non-metallic or nanofibers that are less than 100 nm in size in a base liquid [4–8]. Stability of dispersion plays a vital role in the thermal conductivity of nanofluid [9]. Poor stability and dispersion cause agglomeration and sedimentation thus reducing the effects of nanoparticles in the solution. Aggregation also affects the physical properties of the nanofluid such as viscosity, thermal conductivity and pH [3, 10, 11]. Nanofluids can be prepared by using both one step and two-step methods. However, two-step methods are widely used by researchers compared to the one-step method. Two-step methods mainly comprise mechanical agitation, magnetic stirring, and ultrasonication. Dispersants are added thereafter in case of agglomeration even after ultrasonication because of difference in the interface of nanoparticles and base fluids [12]. Characterization tests help in determining the morphological properties and also dispersion stability of nanofluid. The most common characterization tests are Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The microscopy tests are used to determine the morphology, FTIR is used to obtain the infrared spectrum of solid, liquid and gaseous samples whereas XRD is for phase identification of crystalline material. This article presents the formulation of nanofluid by dispersing nanoparticles in a base oil SAE 20W40 by means of magnetic stirring and ultrasonication in the presence of oleic acid acting as a dispersant. The dispersion stability of the nanofluid is investigated by UV-spectroscopy and the thermal stability by TGA analysis. XRD analysis is done to obtain the unit cell measurement and size of nanoparticles and SEM analysis is done to verify the morphology. 2. Experimentation 2.1. Material The material selected for the present study is boric acid nanoparticles. It has excellent tribological properties. The base oil SAE 20W40 were purchased from a commercial supplier. The physical properties of boric acid nanoparticles and base oil are shown in Tables. 1 and 2 respectively. Table 1. Boric acid nanoparticles physical properties Parameters
Characteristics
Purity
99.99 %
Average particle size
≤ 100 nm
True Density
2.32 gm/cm3
Melting point
170.9 deg C
Appearance
White
Table 2. Diesel engine oil 20W40 properties Parameters
Characteristics
Viscosity @ 400C
121 cSt
Viscosity @ 1000C
12-14 cSt
Viscosity Index
118
Pour Point
30 deg C
Flash point
238 deg C
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2.2. Formulation of nanofluid The different mass concentration of nanoparticles was dispersed in the base oil and allowed to stir on the magnetic stirrer for the period of 10 hours at 900 RPM. Adequate quantity of oleic acid has also been added in the nanofluid for proper dispersion of nanoparticles in the base fluid as it acts as a surface modifier. After that, the resulting nanofluid was treated in ultrasonication bath for the period of 1 hour in the temperature range of 30 0C to 40 0C. The stable mixture of nanofluid is shown in Fig. 1. The procedure for the formulation of nanofluid is shown in Fig. 2. An ultrasonic bath is used for obtaining a homogeneous and stable solution of nanoparticles and base oil.
Fig. 1. Stable and homogeneous mixture of boric acid nanofluid.
Fig. 2. Procedure for nanofluid formulation.
3. Results and discussions 3.1. Dispersion stability analysis using UV-spectroscopy The UV-spectroscopy analysis of boric acid based nanofluid and base oil SAE 20W40 has been done using SHIMADZU UV-1800. The consequences of the spectroscopic analysis as shown in Fig. 3 indicates that base fluid is stable up to the wavelength of 540 nm and gives the absorbance value of 0.15 (a.u) whereas the boric acid based nanofluid shows wavelength shift up to 590 nm and gives stronger absorbance value as compared to the base oil. From Fig. 3 it is also noticed that 0.75 wt% boric acid nanofluid has stronger absorbance value of 0.77 (a.u). Higher the absorbance value, more stable and homogeneous will be the nanofluid. Therefore, 0.75 wt% boric acid nanofluid is homogeneous and more stable.
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Fig. 3. UV-Spectrocopy analysis of different concentration of H3BO3 nanofluid.
3.2. Thermal stability analysis using TGA The thermal stability analysis of boric acid based nanofluid and base oil SAE 20W40 has been conveyed with Mettler Toledo TGA/DSCI Star System. The temperature for the analysis has been ranged from room temperature i.e., 25 0C to 800 0C with a constant heating rate of 10 0C/min. The consequences of TGA analysis has been depicted in Fig. 4. It was seen from the analysis that the thermal stability of boric acid based nanofluid has been enhanced due to the presence of boric acid nanoparticles as compared to base oil. This shows that boric acid nanoparticles are effective for heat transfer applications.
Fig. 4. TGA analysis of 20W40 and 0.75 wt% H3BO3 nanofluid.
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3.3. X-ray diffraction (XRD) of H3BO3 nanopartilces The XRD analysis for H3BO3 nanoparticles is done with Brukers 2nd generation D2 phase x-ray diffractometer with copper Kα radiation of wavelength 1.5406 A. Fig .5 shows the XRD pattern of H3BO3 nanoparticles. Their sample consists of pure H3BO3 nanoparticles which are indicated by the diffracted peaks. Unit cell dimension for each diffracted peak are found to be 5.96, 4.77, 4.59, 4.20, 4.05, 3.17, 2.93, 2.84, 2.64, 2.56, 2.50, 2.24, 2.16, 2.09, 1.59 corresponding to 14.830, 18.580, 19.290, 21.120, 21.890, 28.050, 30.410, 31.450, 33.830, 34.980, 35.860, 40.190, 41.590, 43.100, 57.760 2θ angles. The mean crystallite size is determined by Debye-Scherrer's equation as 49 nm which is given below,
D = kλ / a cos θ
(1)
Where D is the mean size of the crystalline material, k is a shape factor whose value is generally considered as unity, ࣅ is a wavelength and a is the full-width half maxima (FWHM) which can be obtained from diffracted peaks. 3.4. SEM analysis of boric acid nanoparticles and 0.75 wt% nanofluid The SEM analysis of H3BO3 nanoparticles and 0.75 wt% nanofluid is shown in Fig. 6. Fig. 6 (a) and (b) indicate that the morphology of H3BO3 nanoparticles is spherical in nature. The agglomeration of these particles is because of the high surface area to volume ratio. The dispersion of nanoparticles in base oil is uniform and doesn’t shows any agglomeration as shown in Fig. 6 (c).
Fig. 5. X-ray diffraction pattern for H3BO3 nanoparticles.
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Fig. 6. SEM images of H3BO3 nanoparticles (a) At low amplification (b) At high amplification (c) 0.75 wt% H3BO3 nanofluid.
4. Conclusion In the present study, different concentration of boric acid nanofluid has been prepared and characterized by UVspectroscopy and TGA for dispersion and thermal stability analysis, respectively. The 0.75 wt% boric acid nanofluid found to be more stable and well dispersed by UV-spectroscopy analysis. The thermal stability of 0.75 wt% boric acid nanofluid is found to be superior to base oil 20W40 which indicates its suitability for heat transfer and tribological application in diesel engines. XRD analysis indicates good crystalline and pure nature of boric acid nanoparticles. The average particles size is found to be 49 nm by Scherrer’s equation. The morphology of boric acid nanoparticles by SEM indicates that the nanoparticles are spherical in shape and found well dispersed in a base fluid. Acknowledgements The authors would like to thank St.Alloysius College, Jabalpur for providing facilities for XRD and UVspectroscopy analysis also Indian Institute of Technology, Indore for TGA analysis. References [1] [2] [3] [4] [5] [6] [7]
Sidik, Nor Azwadi Che, Syahrullail Samion, Javad Ghaderian, and Muhammad Noor Afiq Witri Muhammad Yazid. "Recent progress on the application of nanofluids in minimum quantity lubrication machining: A review." International Journal of Heat and Mass Transfer 108 (2017): 79-89.S.U.S. Choi, Enhancing thermal conductivity of fluids with nanoparticles, ASME Fed 231 (1995) 99–105. Suganthi, K. S., and K. S. Rajan. "Metal oxide nanofluids: Review of formulation, thermo-physical properties, mechanisms, and heat transfer performance." Renewable and Sustainable Energy Reviews 76 (2017): 226-255. Sidik, NA Che, and O. Adnan Alawi. "Computational investigations on heat transfer enhancement using nanorefrigerants." J. Adv. Res. Des. 1, no. 1 (2014): 35-41. Azwadi, CS Nor, I. M. Adamu, and M. M. Jamil. "Preparation methods and thermal performance of hybrid nanofluids." J. Adv. Rev. Sci. Res. 24, no. 1 (2016): 13-23. Soleimani, Soheil, M. Sheikholeslami, D. D. Ganji, and M. Gorji-Bandpay. "Natural convection heat transfer in a nanofluid filled semi-annulus enclosure." International Communications in Heat and Mass Transfer 39, no. 4 (2012): 565-574. Mohammed, H. A., O. A. Alawi, and NA Che Sidik. "Mixed convective nanofluids flow in a channel having forward-facing step with baffle." J. Adv. Res. Appl. Mech. 24 (2016): 1-21. Zainal, S., C. Tan, C. Sian, and T. Siang. "ANSYS simulation for Ag/HEG hybrid nanofluid in turbulent circular pipe." J. Adv. Res. Appl. Mech. 23, no. 1 (2016): 20-35.
4340
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[8]
Zawrah, M. F., R. M. Khattab, L. G. Girgis, H. El Daidamony, and Rehab E. Abdel Aziz. "Stability and electrical conductivity of water-base Al2O3 nanofluids for different applications." HBRC Journal 12, no. 3 (2016): 227-234. [9] Hong, K. S., Tae-Keun Hong, and Ho-Soon Yang. "Thermal conductivity of Fe nanofluids depending on the cluster size of nanoparticles." Applied Physics Letters 88, no. 3 (2006): 031901. [10] Wang, Xian-ju, Xinfang Li, and Shuo Yang. "Influence of pH and SDBS on the stability and thermal conductivity of nanofluids." Energy & Fuels 23, no. 5 (2009): 2684-2689. [11] Zawrah, M.F., Khattab, R.M., Girgis, L.G., El Daidamony, H. and Aziz, R.E.A., 2016. Stability and electrical conductivity of waterbase Al2O3 nanofluids for different applications. HBRC Journal, 12(3), pp.227-234. [12] Laad, Meena, and Vijay Kumar S. Jatti. "Titanium oxide nanoparticles as additives in engine oil." Journal of King Saud UniversityEngineering Sciences 30, no. 2 (2018): 116-122. [13] Tripathi, Anand Kumar, and Ravikrishnan Vinu. "Characterization of thermal stability of synthetic and semi-synthetic engine oils." Lubricants 3, no. 1 (2015): 54-79.