Browsing by Author "Said, Z."

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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: 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.