Browsing by Author "Saidur, R."

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Citation - WoS: 86
Citation - Scopus: 90
A new correlation for predicting the thermal conductivity of nanofluids, using dimensional analysis
(Elsevier Ltd, 2015) S. Hassani; Rahman Saidur; Saad Mekhilef; A. Hepbasli; Mekhilef, Saad; Hassani, Samir; Saidur, R.; Hepbasli, Arif
Abstract Thermal conductivity of nanofluids is a key thermophysical property which depends on concentration and size of nanoparticles temperature and thermophysical properties of the base fluid. Over last decades several works have been done on the thermal conductivity of nanofluids while a number of numerical and theoretical models have been proposed. However most of these models were not able to predict appropriately the thermal conductivity for a variety of nanofluids. In the present paper using the Vaschy-Buckingham theorem new correlations for predicting the thermal conductivity of nanofluids were developed based on the existing experimental data. The new correlation proposed took into account the Brownian motion the variation of volume fraction the temperature and the size distribution of nanoparticles. The expression developed successfully predicts the thermal conductivity of a variety of nanofluids TiO2 Al2O3 Al Cu Fe MWCNTs/EG Al2O3 SiO2/methanol TiO2 Al2O3 CuO MWCNTs/water Al2O3/radiator coolant Al2O3/R141b Al CNTs/Engine Oil and Cu/Therminol 66 and suits the data with a mean and standard deviation of 2.74% 3.63% respectively. The correlation was derived from 196 values of nanofluids thermal conductivity 86% of them are correlated within a mean deviation of ±5% while 98% of them belong to an interval of ±10%. Moreover the proposed correlation has been tested on 284 values of thermal conductivity of different nanofluids and the predicted values have been found in excellent agreement with the experimental ones with a mean deviation of 3%. The mean deviation between the correlated and the tested point found to be 2.94%. The present correlation will be a good tool for engineers in preparing the nanofluid for different applications in heat exchangers and thermal solar collectors. © 2015 Elsevier B.V. All rights reserved.
Citation - WoS: 173
Citation - Scopus: 206
An experimental investigation of heat transfer enhancement of a minichannel heat sink using Al2O3-H2O nanofluid
(Elsevier Ltd, 2014) M. R. Sohel; S. S. Khaleduzzaman; Rahman Saidur; A. Hepbasli; Mohd Faizul Mohd Sabri; Islam Mohammed Mahbubul; Sabri, M.F.M.; Sohel, M.R.; Khaleduzzaman, S.S.; Mahbubul, I.M.; Hepbasli, A.; Saidur, R.
The thermal performances of a minichannel heat sink are experimentally investigated for cooling of electronics using nanofluid coolant instead of pure water. The Al2O3-H2O nanofluid including the volume fraction ranging from 0.10 to 0.25 vol.% was used as a coolant. The effects of different flow rates of the coolant on the overall thermal performances are also investigated. The flow rate was ranged from 0.50 to 1.25 L/min as well as the Reynolds number from 395 to 989. The coolant was passed through a custom made copper minichannel heat sink consisting of the channel height of 0.8 mm and the channel width of 0.5 mm. The experimental results showed the higher improvement of the thermal performances using nanofluid instead of pure distilled water. The heat transfer coefficient was found to be enhanced up to 18% successfully. The nanofluid significantly lowered the heat sink base temperature (about 2.7 °C) while it also showed 15.72% less thermal resistance at 0.25 vol.% and higher Reynolds number compared to the distilled water. © 2014 Elsevier Ltd. All rights reserved. © 2014 Elsevier B.V. All rights reserved.
Citation - WoS: 135
Citation - Scopus: 155
Analyses of entropy generation and pressure drop for a conventional flat plate solar collector using different types of metal oxide nanofluids
(ELSEVIER SCIENCE SA, 2013) M. A. Alim; Z. Abdin; R. Saidur; A. Hepbasli; M. A. Khairul; N. A. Rahim; Abdin, Z.; Alim, M. A.; Khairul, M. A.; Hepbasli, A.; Saidur, R.; Rahim, N. A.
This paper theoretically analyzes entropy generation heat transfer enhancement capabilities and pressure drop of an absorbing medium with suspended nanoparticles (Al2O3 CuO SiO2 TiO2 dispersed in water) inside a flat plate solar collector. Steady laminar axial flow of a nanofluid is considered. These nanofluids considered have different nanoparticles volume fractions and volume flow rates in the range of 1-4% and 1-4 L/min respectively. Based on the analytical results the CuO nanofluid could reduce the entropy generation by 4.34% and enhance the heat transfer coefficient by 22.15% theoretically compared to water as an absorbing fluid. It also has a small penalty in the pumping power by 1.58%. (C) 2013 Elsevier B.V. All rights reserved.
Citation - WoS: 139
Citation - Scopus: 160
Effect of nanoparticle shape on the heat transfer and thermodynamic performance of a shell and tube heat exchanger
(PERGAMON-ELSEVIER SCIENCE LTD, 2013) M. M. Elias; M. Miqdad; I. M. Mahbubul; R. Saidur; M. Kamalisarvestani; M. R. Sohel; Arif Hepbasli; N. A. Rahim; M. A. Amalina; Kamalisarvestani, M.; Sohel, M. R.; Mahbubul, I. M.; Elias, M. M.; Amalina, M. A.; Saidur, R.; Miqdad, M.
Nanofluid is a heat transfer fluid that can improve the performance of heat exchanger systems. Different parameters such as particle size shape and volume concentration affect the performance of these systems. The objective of this paper is to study the effect of different nanoparticle shapes (such as cylindrical bricks blades platelets and spherical) on the performance of a shell and tube heat exchanger operating with nanofluid analytically. Boehmite alumina (gamma-AlOOH) nanoparticles of different shapes were dispersed in a mixture of water/ethylene glycol as the nanofluid. The thermodynamic performance of the shell and tube heat exchanger that is used in a waste heat recovery system was analysed in terms of heat transfer rate and entropy generation. Established correlations were used to measure the thermal conductivity heat transfer coefficient and rate and entropy generation of nanofluid. The results show an increase in both the heat transfer and thermodynamic performance of the system. However among the five nanoparticle shapes cylindrical shape exhibited better heat transfer characteristics and heat transfer rate. On the other hand entropy generation for nanofluids containing cylindrical shaped nanoparticles was higher in comparison with the other nanoparticle shapes. However the increased percentage of entropy was below 1%. Therefore this greater entropy generation could be deemed negligible and cylindrical shaped nanoparticles are recommended to be utilized in heat exchanger systems working with nanofluids. (c) 2013 Elsevier Ltd. All rights reserved.
Citation - WoS: 127
Citation - Scopus: 145
Energy and exergy efficiency of a flat plate solar collector using pH treated Al2O3 nanofluid
(ELSEVIER SCI LTD, 2016) Z. Said; R. Saidur; M. A. Sabiha; A. Hepbasli; N. A. Rahim; Said, Z.; Sabiha, M. A.; Saidur, R.; Hepbasli, A.; Rahim, N. A.
Application of nanofluid to increase the thermal efficiency of a traditional solar collector is getting tremendous attention among the scientific community. Al2O3-water nanofluid as a working fluid and its effect on the energy and exergy efficiencies of a flat plate solar collector was examined experimentally. Volume fraction used for this study was 0.1% and 0.3% while the size of the nanoparticles was similar to 13 nm. Experiments were carried out using a stable nanofluid which was obtained by controlling the pH of the solution over a period of 30 days. The mass flow rates of the nanofluid varied from 0.5 to 1.5 kg/min. Energy and exergy efficiencies of a flat plate solar collector using water and nanofluids as working fluids were matched. The results revealed that nanofluids increased the energy efficiency by 83.5% for 0.3% v/v and 1.5 kg/min whereas the exergy efficiency was enhanced by up to 20.3% for 0.1% v/v and 1 kg/min. Thermal efficiency of the system was found to be more than 50% compared to the existing system available in the literature. New findings on the stability and exergy analysis of the solar collector system operated with a pH controlled nanofluid are reported. (C) 2015 Elsevier Ltd. All rights reserved.
Citation - WoS: 106
Citation - Scopus: 122
Energy- economic- and environmental analysis of a flat-plate solar collector operated with SiO2 nanofluid
(SPRINGER, 2015) M. Faizal; R. Saidur; S. Mekhilef; Arif Hepbasli; I. M. Mahbubul; Mekhilef, S.; Mahbubul, I. M.; Saidur, R.; Hepbasli, A.; Faizal, M.
To overcome the environmental impact and declining source of fossil fuels renewable energy sources need to meet the increasing demand of energy. Solar thermal energy is clean and infinite suitable to be a good replacement for fossil fuel. However the current solar technology is still expensive and low in efficiency. One of the effective ways of increasing the efficiency of solar collector is to utilize high thermal conductivity fluid known as nanofluid. This research analyzes the impact on the performance fluid flow heat transfer economic and environment of a flat-plate solar thermal collector by using silicon dioxide nanofluid as absorbing medium. The analysis is based on different volume flow rates and varying nanoparticles volume fractions. The study has indicated that nanofluids containing small amount of nanoparticles have higher heat transfer coefficient and also higher energy and exergy efficiency than base fluids. The measured viscosity of nanofluids is higher than water but it gives negligible effect on pressure drop and pumping power. Using SiO2 nanofluid in solar collector could also save 280 MJ more embodied energy offsetting 170 kg less CO2 emissions and having a faster payback period of 0.12 years compared to conventional water-based solar collectors.
Citation - WoS: 28
Citation - Scopus: 33
Experimental investigation of the relation between yield stress and ultrasonication period of nanofluid
(Elsevier Ltd, 2016) Islam Mohammed Mahbubul; Rahman Saidur; A. Hepbasli; Muhammad Afifi Amalina; Amalina, M. A.; Mahbubul, I. M.; Saidur, R.; Hepbasli, A.
Nanofluids are the mixtures of solid nanoparticles in liquid. Like most other fluids nanofluids could behave as yield stress fluids which require a certain amount of stress to flow. This flow characteristic may depend on the preparation of nanofluids. This paper investigates the effect of the ultrasonication periods (used during the nanofluid preparation) on the yield stress. The Al2O3 nanoparticle with 0.5 vol.% of solid concentration was added to the distilled water using an ultrasonic horn and applied for different durations from 0 to 5 h. The microstructures of the nanoparticles were observed by transmission electron microscopy. The flow characteristics as the shear stresses at different shear rates (12.23-305.75 s-1) were observed for various temperatures from 10 to 50 °C. The yield stress the flow behavior index and the consistency index were studied using the Herschel-Bulkley rheological model. From this study non-Newtonian flow characteristic was observed. The yield stress decreased with increasing the fluid temperature. At the start of the ultrasonication the yield stress decreased rapidly, however for further ultrasonication it decreased slowly. © 2015 Elsevier B.V. All rights reserved.
Citation - WoS: 20
Citation - Scopus: 24
Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles
(Springer Verlag service@springer.de, 2018) M. M. Elias; Rahman Saidur; Rached Ben Mansour; A. Hepbasli; Nasrudin Abd Rahim; Jesbains Kaur; Ben-Mansour, R.; Hepbasli, A.; Saidur, R.; Jesbains, K.; Elias, M. M.; Rahim, N. A.
Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration the maximum heat transfer coefficient the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14% 7.8% and 15.4% respectively in comparison with the base fluid. Consequently when the volume concentration or Reynolds number increases the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle. © 2018 Elsevier B.V. All rights reserved.
Citation - WoS: 149
Citation - Scopus: 168
Heat transfer performance and exergy analyses of a corrugated plate heat exchanger using metal oxide nanofluids
(Elsevier Ltd, 2014) M. A. Khairul; Mohammad A. Alim; Islam Mohammed Mahbubul; Rahman Saidur; A. Hepbasli; Altab Hossain; Khairul, M.A.; Alim, M.A.; Mahbubul, I.M.; Hossain, A.; Hepbasli, A.; Saidur, R.
Heat exchangers have been widely used for efficient heat transfer from one medium to another. Nanofluids are potential coolants which can afford excellent thermal performance in heat exchangers. This study examined the effects of water and CuO/water nanofluids (as coolants) on heat transfer coefficient heat transfer rate frictional loss pressure drop pumping power and exergy destruction in the corrugated plate heat exchanger. The heat transfer coefficient of CuO/water nanofluids increased about 18.50 to 27.20%with the enhancement of nanoparticles volume concentration from 0.50 to 1.50% compared to water. Moreover improvement in heat transfer rate was observed for nanofluids. On the other hand exergy loss was reduced by 24% employing nanofluids as a heat transfermediumwith comparing to conventional fluid. Besides 34% higher exergetic heat transfer effectiveness was found for 1.5 vol.% of nanoparticles. It has a small penalty in the pumping power. Hence the plate heat exchanger performance can be improved by adapting the working fluid with CuO/water nanofluids. © 2013 Elsevier Ltd. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 69
Citation - Scopus: 86
New thermophysical properties of water based TiO2 nanofluid-The hysteresis phenomenon revisited
(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Z. Said; R. Saidur; A. Hepbasli; N. A. Rahim; Said, Z.; Saidur, R.; Hepbasli, A.; Rahim, N.A.
Homogeneous stable suspensions acquired by dispersing dry Al2O3 and TiO2 nanoparticles in controlled pH solution and distilled water respectively were prepared and investigated in this study. First of all the mean nanoparticle diameters were studied by dynamic light scattering (DLS) technique and the nanofluid stability was analyzed by zeta potential measurements. The nano-crystalline structures were characterized by scanning electron microscope and transmission electron microscope. The rheological behavior was determined for both nanofluids at nanoparticle volume concentrations up to 0.3%. The effect of temperature for the heating and cooling phases was analyzed from 25 degrees C to 80 degrees C. Furthermore the influence of temperature pressure drop pumping power zeta potential size and densities were analyzed for fresh prepared samples as well as for samples used in a flat plate solar collector over a period of 30 days. The thermal conductivity enhancement of the two nanofluids demonstrated a nonlinear relationship with respect to temperature and volume fraction with increases in the volume fraction and temperature. All resulted in an increase in the measured enhancement. Existence of a critical temperature was observed beyond which the particle suspension properties altered drastically which in turn triggered a hysteresis phenomenon. The hysteresis phenomenon on viscosity measurement which is believed to be the first observed for Al2O3/water and TiO2/water-based nanofluids has raised serious concerns about the use of nanofluids for heat transfer enhancement. The pressure drop and pumping power of the nanofluid flows are found to be very close to those of the base liquid for low volume concentration. It may be concluded that nanofluids can be utilized as a working medium with a negligible effect of enhanced viscosity and/or density. Our findings provide a view on the thermo physical properties of nanofluids that is compared with that in the literature and new findings (such as viscosity hysteresis phenomenon and pumping power) have been presented which are not available in literature as yet. (C) 2014 Elsevier Ltd. All rights reserved.
Citation - WoS: 200
Citation - Scopus: 245
Performance enhancement of a Flat Plate Solar collector using Titanium dioxide nanofluid and Polyethylene Glycol dispersant
(Elsevier Ltd, 2015) Zafar Said; M. A. Sabiha; Rahman Saidur; A. Hepbasli; Nasrudin Abd Rahim; Saad Mekhilef; Thomas Arthur Ward; Said, Z.; Sabiha, M.A.; Hepbasli, A.; Rahim, N.A.; Mekhilef, S.; Ward, T.A.; Saidur, R.
The use of TiO2-water nanofluid as a working fluid for enhancing the performance of a flat plate solar collector has been studied. The volume fraction of the nanoparticles was 0.1% and 0.3% respectively while the mass flow rates of the nanofluid varied from 0.5 to 1.5 kg/min respectively. Thermo-physical properties and reduced sedimentation for TiO2-nanofluid was obtained using PEG 400 dispersant. The results reveal the impact and importance of each of these parameters. Energy efficiency increased by 76.6% for 0.1% volume fraction and 0.5 kg/min flow rate whereas the highest exergy efficiency achieved was 16.9% for 0.1% volume fraction and 0.5 kg/min flow rate. Results showed that the pressure drop and pumping power of TiO2 nanofluid was very close to the base fluid for the studied volume fractions. © 2021 Elsevier B.V. All rights reserved.