Saidur Rahman - Profile on Academia.edu (original) (raw)

Papers by Saidur Rahman

An experimental investigation of thermo-physical properties and heat transfer performance of Al2O3-Aviation Turbine Fuel nanofluids

Applied Thermal Engineering, 2011

Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performanc... more Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performance in a potential application of regeneratively cooled semi-cryogenic rocket engine thrust chambers. The volume concentration of Al2O3 nanoparticles is varied between 0 and 1%. To ensure a realistic evaluation, all properties of the nanofluids are experimentally measured rather than resorting to available formulae or empirical correlations. Among the

Numerical Heat Transfer, Part A: Applications, 2012

In the present study, the behaviour of nanofluids is investigated numerically in a lid-driven tri... more In the present study, the behaviour of nanofluids is investigated numerically in a lid-driven triangular enclosure which has a partially heated on bottom side to gain insight into convective recirculation and flow processes induced by a nanofluid. The present model is developed to examine the behaviour of nanofluids taking into account the heater length. Fluid mechanics and conjugate heat transfer, described in terms of continuity, linear momentum and energy equations, were predicted by using the Galerkin finite element method. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Numerical results are obtained for a wide range of parameters such as the Richardson number, and heater length. Copper-water nanofluids is used with Prandtl number, Pr = 6.2. The streamlines, isotherm plots and the variation of the average Nusselt number at the hot surface as well as average fluid temperature in the enclosure is presented and discussed in detailed.

Clean Technologies and Environmental Policy, 2011

To overcome the environmental impact and declining source of fossil fuels, renewable energy sourc... more 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 SiO 2 nanofluid in solar collector could also save 280 MJ more embodied energy, offsetting 170 kg less CO 2 emissions and having a faster payback period of 0.12 years compared to conventional water-based solar collectors.

A review on development of solar drying applications

Renewable and Sustainable Energy Reviews, 2014

ABSTRACT Drying is an essential process in the preservation of agricultural crops and in industri... more ABSTRACT Drying is an essential process in the preservation of agricultural crops and in industries, such as textile production, dairy processing, cement production, clay brick production, tile production, wood and timber processing, wastewater treatment, and biomass treatment. The energy requirement for drying can be supplied from various sources, namely, electricity, fossil fuel, natural gas, wood, bark forest residual, and solar. Although the use of solar radiation for drying has existed since antiquity, it has not yet been widely commercialized, particularly in the industrial sector. Considering the rapid depletion of natural fuel resources and because of the rising fossil fuel cost, solar drying is expected to become indispensable in the future. Moreover, environmental considerations and damages caused by human beings due to increasing consumption of fossil fuel prompt governments and industries to use renewable energies as a clean and sustainable resource, thus, the use of solar energy for drying. The numerous solar drying applications are classified into two main categories, that is, agricultural and industrial. Many benefits could be exploited from solar energy for drying applications. Solar energy enables the industries and agricultural sectors to modify their energy requirement, improve their energy stability, and increase energy sustainability, which lead to improvement in the system efficiency. We review the role of the drying system in industry and agriculture, the energy consumption capacity, and the availability of the required energy for the products to be dried. In addition, the economical, environmental, and political aspects of using solar dryers are discussed. Special attention is given to industrial drying and in finding opportunities to use compatible dryers for a certain industry. In short, we conduct a comprehensive review of the new approach to use solar energy in industrial drying sector.

International Communications in Heat and Mass Transfer, 2014

Homogeneous stable suspensions acquired by dispersing dry Al 2 O 3 and TiO 2 nanoparticles in con... more Homogeneous stable suspensions acquired by dispersing dry Al 2 O 3 and TiO 2 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°C to 80°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 Al 2 O 3 /water and TiO 2 /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.

2011 IEEE Conference on Clean Energy and Technology (CET), 2011

Along with the enhancement of technology and alarming of global warming, various types of technol... more Along with the enhancement of technology and alarming of global warming, various types of technologies are advanced worldwide nowadays to harness the energy from the sun such as solar thermal energy, ocean thermal energy conversion, solar ponds, solar tower and photovoltaic systems to utilize the energy in the majority of domestic applications and industrial sector to a certain extent. Subsequently, gradual increase usage of solar energy requires creating awareness among public to protect the environment in term of green campaign which is one of the hot topics among the Malaysians where there are many organizations organizing green campaign such as Environmental Protection Society Malaysia (EPSM), Malaysia Environment NGOs (MENGO) and Treat Every Environment Special Sdn. Bhd. (TRESS). Therefore, this study examines solar energy production and consumption worldwide by looking at various existing solar technologies to have the understanding of each technology. This article also intends to catch up specifically the social viability of solar energy production and use, with the availability of the resources for the full scale development.

Analysis of energy, exergy and energy savings of a fire tube boiler

2011 IEEE Conference on Clean Energy and Technology (CET), 2011

Abstract Energy efficiency improvement as well as energy savings is the major concern in most of ... more Abstract Energy efficiency improvement as well as energy savings is the major concern in most of the development countries all over the world. In this study, the useful concept of energy and exergy utilization is analyzed to investigate the energy and exergy efficiency, energy and exergy losses and energy savings of boilers. The energy and exergy efficiencies of a combustion chamber and stream production chamber of the boiler have been analyzed as well. The exergy efficiency of the combustion chamber is found to be 49.6%. The ...

Renewable and Sustainable Energy Reviews, 2013

Nanotechnology is an enabling technology that provides an extensive range of resources to resolve... more Nanotechnology is an enabling technology that provides an extensive range of resources to resolve the energy-related problems, as the developing components and appliances are smaller than 100 nm they provide the new ways to catch, store and exchange energy. Every day, the sun shines a huge amount of energy which is generated through a process of nuclear fusion. Even the sun radiates more energy in one second than people have practiced since the beginning of time. It has been noted that the technical potential of solar energy all over the world is many times larger than the current total primary energy demanded. In this study, the solar harvesting technology with the help of nano-materials has been thoroughly studied. The different types of modern solar collecting technologies that use the nanomaterials effectively and successfully have been discussed. Among a number of devices, the solar collector, the fuel cell, photocatalysis and solar photovoltaic have used the nanomaterials to increase the efficiency. It is found that by using nanomaterials the incident radiation can be increased by 9 times while the efficiency of the solar collector is 10% higher compared to that of a conventional flat plate solar collector. The generation ways solar cell technologies have been also discussed here. At the end of this article, few challenges in using nanotechnology are also addressed in detail.

An overview of energy savings measures for cement industries

Renewable and Sustainable Energy Reviews, 2013

ABSTRACT Due the advances in the industrial processes, in which the cement industry is a major co... more ABSTRACT Due the advances in the industrial processes, in which the cement industry is a major contributor, energy consumption and greenhouse gas emission has increased significantly. This paper reviews previous studies on energy saving, carbon dioxide emission reductions and the various technologies used to improve the energy efficiency in the cement industry. Energy efficiency measures for raw materials preparation, clinker production, products and feedstock changes, general energy efficiency measures, and finish grinding have been surveyed. It was found that the largest recorded amounts of thermal energy savings, electrical energy savings and emission reductions to date are 3.4 GJ/t, 35 kW h/t and 212.54 kgCO(2)/t, respectively.

Renewable and Sustainable Energy Reviews, 2011

Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat tr... more Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanofluids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications.

Renewable and Sustainable Energy Reviews, 2011

To overcome the negative impacts on the environment and other problems associated with fossil fue... more To overcome the negative impacts on the environment and other problems associated with fossil fuels have forced many countries to inquire into and change to environmental friendly alternatives that are renewable to sustain the increasing energy demand. Solar energy is one of the best renewable energy sources with least negative impacts on the environment. Different countries have formulated solar energy policies to reducing dependence on fossil fuel and increasing domestic energy production by solar energy. This paper discusses a review about the different solar energy policies implemented on the different countries of the world. According to the 2010 BP Statistical Energy Survey, the world cumulative installed solar energy capacity was 22928.9 MW in 2009, a change of 46.9% compared to 2008. Also this paper discussed the existing successful solar energy policies of few selected countries. Based on literatures, it has been found that FIT, RPS and incentives are the most beneficial energy policies implemented by many countries around the world. These policies provide significant motivation and interest for the development and use of renewable energy technologies. Also the status of solar energy policy for Malaysia is investigated and compared with that of the successful countries in the world.

Energy and Environmental Effects of Shell and Tube Heat Exchanger by Using Nanofluid as a Coolant†

JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2014

ABSTRACT The mixture of nanoparticles in a uid can improve the h of the uid. In this paper, the h... more ABSTRACT The mixture of nanoparticles in a uid can improve the h of the uid. In this paper, the h of water, Al-water, Al2O3-water, Fe3O4-water and TiO2-water nano uids with 0.04 volume fraction of nanoparticles have been analytically calculated for a shell and tube heat exchanger. Moreover, the energy e ectiveness and environmental e ects have also been calculated for the above nano uids. It is found that, the h of the above nano uids were approximately 17, 14, 13, and 10% higher compared to pure water, respectively. Furthermore, energy e ectiveness also improved by 31, 35, 41, and 37%, respectively. If all sectors could use nano uids in their heat exchanger systems, then signi cant amounts of heat emission could be reduced all over the world. Therefore, nano uid can be used as a coolant to improve the performance of the heat exchanger system.

International Journal of Heat and Mass Transfer, 2014

Nanorefrigerants are potential nanofluid that can improve the performance of refrigeration and ai... more Nanorefrigerants are potential nanofluid that can improve the performance of refrigeration and airconditioning system. Rheological properties of these fluids need to analyze before practical implementation as they influence the flow characteristics. In the present work, the rheological behavior (relation of shear stress and viscosity with shear rate) of Al 2 O 3 /R141b nanorefrigerant for 0.05-0.15 volume concentrations with the temperature ranging from 4 to 16°C was studied. From this experiment, it is found that, the nanorefrigerant showed non-Newtonian and shear thickening behavior. However, at high shear rates, the trend was found to be quite close to Newtonian behavior. Moreover, viscosity increases with the increase of shear rates and volume concentrations, however, decreases with the increase of temperature.

International Journal of Heat and Mass Transfer, 2013

Thermosyphons are widely used in thermal engineering applications such as cooling of electronics ... more Thermosyphons are widely used in thermal engineering applications such as cooling of electronics and waste heat recovery thanks to their passive cooling ability. Performance of thermosyphons could be improved by various methods like changing the transport properties and heat transfer characteristics of the working fluid. Nanofluid, referring to a colloidal suspension of a base fluid and nanosized (1-100 nm) solid particles, is an option to achieve this target. Combining the heat exchange nature of thermosyphons and distinct thermal characteristics of nanofluids can open up new horizons in the field of heat transfer. Current study concentrates on the thermal performance of a two-phase closed thermosyphon filled with two nanofluids using water as the base fluid mixed with Al 2 O 3 and TiSiO 4 nanoparticles. Nanofluids were prepared in different volumetric concentrations (0.01%, 0.02%, 0.05% and 0.075%). Different heat loads (40 W, 70 W, 120 W, 180 W and 210 W) were applied to the evaporator section. Results demonstrate that both nanofluids improve the performance through reduction in thermal resistance by 65% (at 0.05 vol.% for Al 2 O 3) and 57% (at 0.075 vol.% for TiSiO 4). Other improvements were also found in forms of increase in heat transfer coefficient and decrease in evaporator wall temperature.

International Journal of Heat and Mass Transfer, 2012

As conventional energy sources like fossil fuels are getting rare, cost of energy production has ... more As conventional energy sources like fossil fuels are getting rare, cost of energy production has become higher as well as the concern of environmental pollution by burning of fossil fuels among the developed and developing nations. Solar energy is the most vastly available energy and very effective in terms of energy conversion. The most common solar thermal collector used is the black surface as radiant absorber but the thermal energy efficiency is low. In this study, the effect of nanofluid has been analyzed by using as working fluid for direct solar collector. The extinction coefficient of water based aluminum nanofluid has been investigated and evaluated by varying nanoparticle size and volume fraction. The particle size has minimal influence on the optical properties of nanofluid. On the other hand, the extinction coefficient is linearly proportionate to volume fraction. The improvement is promising within 1.0% volume fraction and the nanofluid is almost opaque to light wave.

International Journal of Computer Mathematics, 2007

In this paper we give an algorithm to generate all distributions of distinguishable objects to bi... more In this paper we give an algorithm to generate all distributions of distinguishable objects to bins without repetition. Our algorithm generates each distribution in constant time. To the best of our knowledge, our algorithm is the first algorithm which generates each solution in O(1) time in ordinary sense. As a byproduct of our algorithm, we get a new algorithm to enumerate all multiset partitions when the number of partitions is fixed and the partitions are numbered. In this case, our algorithm generates each multiset partition in constant time (in ordinary sense). Finally, we extend our algorithm for the case when the bins have priorities associated with them. Overall space complexity of our algorithm is O(km), where there are m bins and the objects fall into k different classes.

Effect of particle concentration, temperature and surfactant on surface tension of nanofluids

International Communications in Heat and Mass Transfer, 2013

ABSTRACT Heat transfer performance with nanofluids depends on the thermo physical properties of t... more ABSTRACT Heat transfer performance with nanofluids depends on the thermo physical properties of the suspension. Surface tension is an important property for heat transfer calculation. In this paper, various parameters that effect on the surface tension of nanofluids such as nanofluid preparation method, effect of volume fraction, temperature, and surfactants on nanofluids have been studied. Additionally, precise assessments on the theoretical correlations related to the surface tension of nanofluids have also been included. Based on the existing experimental results, surface tension augments respectively with volume fraction intensification. Surface tension of nanofluids decreases accordingly with the increase of temperature and surfactant concentration. Nevertheless, there have been some contradictory results on the effect of volume fraction and surfactant on surface tension of nanofluids.

A numerical study on the effect of a heated hollow cylinder on mixed convection in a ventilated cavity

International Communications in Heat and Mass Transfer, 2010

The present work is aimed to study mixed convection heat transfer characteristics within a ventil... more The present work is aimed to study mixed convection heat transfer characteristics within a ventilated square cavity having a heated hollow cylinder. The heated hollow cylinder is placed at the center of the cavity. In addition, the wall of the cavity is assumed to be adiabatic. Flows are imposed through the inlet at the bottom of the left wall and

Radiative properties of nanofluids

International Communications in Heat and Mass Transfer, 2013

ABSTRACT Compared to thermal conductivity and convection studies with nanofluids; the optical and... more ABSTRACT Compared to thermal conductivity and convection studies with nanofluids; the optical and radiative properties of nanofluids have received much less interest. However, very recently, the number of studies on radiative heat transfer in nanofluids has been increasing. This is due to the fact that, in general, a composite nanofluid has different properties than those found in either the base fluid or the particles. At high temperatures, knowledge of the resultant radiative properties becomes increasingly significant. The concept of using direct absorbing nanofluid (suspension formed by mixing nanoparticles and a liquid) recently been shown numerically and experimentally to be an efficient method for harvesting solar thermal energy. Nanofluid is a product of emerging field of nanotechnology, where nanoparticles (1–100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.). Nanofluids as an innovative class of heat transfer fluids represent a rapidly emerging research field where nano-science and thermal engineering coexist. Nanofluids are considered to be a two-phase system, comprised of a solid and a liquid phase. Compared to the base fluids like water or oil, nanofluids feature enhanced thermo-physical properties such as thermal diffusivity, viscosity, thermal conductivity, convective heat transfer coefficients, and optical properties. They offer unprecedented potential in many applications. Recent development in solar thermal collectors is the use of nanofluids to absorb the light directly. There is much current work going on the use of nanoparticles in several applications. With thousands of papers published every year, a comprehensive literature survey is impossible, and only selected representative publications are cited in this paper, particularly as they concern fundamental scientific insights on the fundamental optical properties of nanofluids.

Environmental Progress & Sustainable Energy, 2012

According to the source paper written in 2006, the Malaysian food industrial sector accounted for... more According to the source paper written in 2006, the Malaysian food industrial sector accounted for about 14% of the total manufacturing energy consumption. As energy costs rapidly increase, alternative energy sources and efficiency improvements become essential to energy planning, cost savings, resource optimization, and environmental protection in these industries. This article focuses on the energy savings, economic benefits, and emission reduction that can be obtained by applying various energy saving options. This study shows that significant power can be saved annually by utilizing energy efficient motors. The cost savings, payback period, and reduction in CO 2 emissions are estimated for different motor loads. It is shown that sizeable amounts of energy can be saved using VSD, waste heat recovery, new efficiency lamps (T-5), and repairing leakages. 2012 Ameri

An experimental investigation of thermo-physical properties and heat transfer performance of Al2O3-Aviation Turbine Fuel nanofluids

Applied Thermal Engineering, 2011

Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performanc... more Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performance in a potential application of regeneratively cooled semi-cryogenic rocket engine thrust chambers. The volume concentration of Al2O3 nanoparticles is varied between 0 and 1%. To ensure a realistic evaluation, all properties of the nanofluids are experimentally measured rather than resorting to available formulae or empirical correlations. Among the

Numerical Heat Transfer, Part A: Applications, 2012

In the present study, the behaviour of nanofluids is investigated numerically in a lid-driven tri... more In the present study, the behaviour of nanofluids is investigated numerically in a lid-driven triangular enclosure which has a partially heated on bottom side to gain insight into convective recirculation and flow processes induced by a nanofluid. The present model is developed to examine the behaviour of nanofluids taking into account the heater length. Fluid mechanics and conjugate heat transfer, described in terms of continuity, linear momentum and energy equations, were predicted by using the Galerkin finite element method. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Numerical results are obtained for a wide range of parameters such as the Richardson number, and heater length. Copper-water nanofluids is used with Prandtl number, Pr = 6.2. The streamlines, isotherm plots and the variation of the average Nusselt number at the hot surface as well as average fluid temperature in the enclosure is presented and discussed in detailed.

Clean Technologies and Environmental Policy, 2011

To overcome the environmental impact and declining source of fossil fuels, renewable energy sourc... more 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 SiO 2 nanofluid in solar collector could also save 280 MJ more embodied energy, offsetting 170 kg less CO 2 emissions and having a faster payback period of 0.12 years compared to conventional water-based solar collectors.

A review on development of solar drying applications

Renewable and Sustainable Energy Reviews, 2014

ABSTRACT Drying is an essential process in the preservation of agricultural crops and in industri... more ABSTRACT Drying is an essential process in the preservation of agricultural crops and in industries, such as textile production, dairy processing, cement production, clay brick production, tile production, wood and timber processing, wastewater treatment, and biomass treatment. The energy requirement for drying can be supplied from various sources, namely, electricity, fossil fuel, natural gas, wood, bark forest residual, and solar. Although the use of solar radiation for drying has existed since antiquity, it has not yet been widely commercialized, particularly in the industrial sector. Considering the rapid depletion of natural fuel resources and because of the rising fossil fuel cost, solar drying is expected to become indispensable in the future. Moreover, environmental considerations and damages caused by human beings due to increasing consumption of fossil fuel prompt governments and industries to use renewable energies as a clean and sustainable resource, thus, the use of solar energy for drying. The numerous solar drying applications are classified into two main categories, that is, agricultural and industrial. Many benefits could be exploited from solar energy for drying applications. Solar energy enables the industries and agricultural sectors to modify their energy requirement, improve their energy stability, and increase energy sustainability, which lead to improvement in the system efficiency. We review the role of the drying system in industry and agriculture, the energy consumption capacity, and the availability of the required energy for the products to be dried. In addition, the economical, environmental, and political aspects of using solar dryers are discussed. Special attention is given to industrial drying and in finding opportunities to use compatible dryers for a certain industry. In short, we conduct a comprehensive review of the new approach to use solar energy in industrial drying sector.

International Communications in Heat and Mass Transfer, 2014

Homogeneous stable suspensions acquired by dispersing dry Al 2 O 3 and TiO 2 nanoparticles in con... more Homogeneous stable suspensions acquired by dispersing dry Al 2 O 3 and TiO 2 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°C to 80°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 Al 2 O 3 /water and TiO 2 /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.

2011 IEEE Conference on Clean Energy and Technology (CET), 2011

Along with the enhancement of technology and alarming of global warming, various types of technol... more Along with the enhancement of technology and alarming of global warming, various types of technologies are advanced worldwide nowadays to harness the energy from the sun such as solar thermal energy, ocean thermal energy conversion, solar ponds, solar tower and photovoltaic systems to utilize the energy in the majority of domestic applications and industrial sector to a certain extent. Subsequently, gradual increase usage of solar energy requires creating awareness among public to protect the environment in term of green campaign which is one of the hot topics among the Malaysians where there are many organizations organizing green campaign such as Environmental Protection Society Malaysia (EPSM), Malaysia Environment NGOs (MENGO) and Treat Every Environment Special Sdn. Bhd. (TRESS). Therefore, this study examines solar energy production and consumption worldwide by looking at various existing solar technologies to have the understanding of each technology. This article also intends to catch up specifically the social viability of solar energy production and use, with the availability of the resources for the full scale development.

Analysis of energy, exergy and energy savings of a fire tube boiler

2011 IEEE Conference on Clean Energy and Technology (CET), 2011

Abstract Energy efficiency improvement as well as energy savings is the major concern in most of ... more Abstract Energy efficiency improvement as well as energy savings is the major concern in most of the development countries all over the world. In this study, the useful concept of energy and exergy utilization is analyzed to investigate the energy and exergy efficiency, energy and exergy losses and energy savings of boilers. The energy and exergy efficiencies of a combustion chamber and stream production chamber of the boiler have been analyzed as well. The exergy efficiency of the combustion chamber is found to be 49.6%. The ...

Renewable and Sustainable Energy Reviews, 2013

Nanotechnology is an enabling technology that provides an extensive range of resources to resolve... more Nanotechnology is an enabling technology that provides an extensive range of resources to resolve the energy-related problems, as the developing components and appliances are smaller than 100 nm they provide the new ways to catch, store and exchange energy. Every day, the sun shines a huge amount of energy which is generated through a process of nuclear fusion. Even the sun radiates more energy in one second than people have practiced since the beginning of time. It has been noted that the technical potential of solar energy all over the world is many times larger than the current total primary energy demanded. In this study, the solar harvesting technology with the help of nano-materials has been thoroughly studied. The different types of modern solar collecting technologies that use the nanomaterials effectively and successfully have been discussed. Among a number of devices, the solar collector, the fuel cell, photocatalysis and solar photovoltaic have used the nanomaterials to increase the efficiency. It is found that by using nanomaterials the incident radiation can be increased by 9 times while the efficiency of the solar collector is 10% higher compared to that of a conventional flat plate solar collector. The generation ways solar cell technologies have been also discussed here. At the end of this article, few challenges in using nanotechnology are also addressed in detail.

An overview of energy savings measures for cement industries

Renewable and Sustainable Energy Reviews, 2013

ABSTRACT Due the advances in the industrial processes, in which the cement industry is a major co... more ABSTRACT Due the advances in the industrial processes, in which the cement industry is a major contributor, energy consumption and greenhouse gas emission has increased significantly. This paper reviews previous studies on energy saving, carbon dioxide emission reductions and the various technologies used to improve the energy efficiency in the cement industry. Energy efficiency measures for raw materials preparation, clinker production, products and feedstock changes, general energy efficiency measures, and finish grinding have been surveyed. It was found that the largest recorded amounts of thermal energy savings, electrical energy savings and emission reductions to date are 3.4 GJ/t, 35 kW h/t and 212.54 kgCO(2)/t, respectively.

Renewable and Sustainable Energy Reviews, 2011

Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat tr... more Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanofluids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications.

Renewable and Sustainable Energy Reviews, 2011

To overcome the negative impacts on the environment and other problems associated with fossil fue... more To overcome the negative impacts on the environment and other problems associated with fossil fuels have forced many countries to inquire into and change to environmental friendly alternatives that are renewable to sustain the increasing energy demand. Solar energy is one of the best renewable energy sources with least negative impacts on the environment. Different countries have formulated solar energy policies to reducing dependence on fossil fuel and increasing domestic energy production by solar energy. This paper discusses a review about the different solar energy policies implemented on the different countries of the world. According to the 2010 BP Statistical Energy Survey, the world cumulative installed solar energy capacity was 22928.9 MW in 2009, a change of 46.9% compared to 2008. Also this paper discussed the existing successful solar energy policies of few selected countries. Based on literatures, it has been found that FIT, RPS and incentives are the most beneficial energy policies implemented by many countries around the world. These policies provide significant motivation and interest for the development and use of renewable energy technologies. Also the status of solar energy policy for Malaysia is investigated and compared with that of the successful countries in the world.

Energy and Environmental Effects of Shell and Tube Heat Exchanger by Using Nanofluid as a Coolant†

JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2014

ABSTRACT The mixture of nanoparticles in a uid can improve the h of the uid. In this paper, the h... more ABSTRACT The mixture of nanoparticles in a uid can improve the h of the uid. In this paper, the h of water, Al-water, Al2O3-water, Fe3O4-water and TiO2-water nano uids with 0.04 volume fraction of nanoparticles have been analytically calculated for a shell and tube heat exchanger. Moreover, the energy e ectiveness and environmental e ects have also been calculated for the above nano uids. It is found that, the h of the above nano uids were approximately 17, 14, 13, and 10% higher compared to pure water, respectively. Furthermore, energy e ectiveness also improved by 31, 35, 41, and 37%, respectively. If all sectors could use nano uids in their heat exchanger systems, then signi cant amounts of heat emission could be reduced all over the world. Therefore, nano uid can be used as a coolant to improve the performance of the heat exchanger system.

International Journal of Heat and Mass Transfer, 2014

Nanorefrigerants are potential nanofluid that can improve the performance of refrigeration and ai... more Nanorefrigerants are potential nanofluid that can improve the performance of refrigeration and airconditioning system. Rheological properties of these fluids need to analyze before practical implementation as they influence the flow characteristics. In the present work, the rheological behavior (relation of shear stress and viscosity with shear rate) of Al 2 O 3 /R141b nanorefrigerant for 0.05-0.15 volume concentrations with the temperature ranging from 4 to 16°C was studied. From this experiment, it is found that, the nanorefrigerant showed non-Newtonian and shear thickening behavior. However, at high shear rates, the trend was found to be quite close to Newtonian behavior. Moreover, viscosity increases with the increase of shear rates and volume concentrations, however, decreases with the increase of temperature.

International Journal of Heat and Mass Transfer, 2013

Thermosyphons are widely used in thermal engineering applications such as cooling of electronics ... more Thermosyphons are widely used in thermal engineering applications such as cooling of electronics and waste heat recovery thanks to their passive cooling ability. Performance of thermosyphons could be improved by various methods like changing the transport properties and heat transfer characteristics of the working fluid. Nanofluid, referring to a colloidal suspension of a base fluid and nanosized (1-100 nm) solid particles, is an option to achieve this target. Combining the heat exchange nature of thermosyphons and distinct thermal characteristics of nanofluids can open up new horizons in the field of heat transfer. Current study concentrates on the thermal performance of a two-phase closed thermosyphon filled with two nanofluids using water as the base fluid mixed with Al 2 O 3 and TiSiO 4 nanoparticles. Nanofluids were prepared in different volumetric concentrations (0.01%, 0.02%, 0.05% and 0.075%). Different heat loads (40 W, 70 W, 120 W, 180 W and 210 W) were applied to the evaporator section. Results demonstrate that both nanofluids improve the performance through reduction in thermal resistance by 65% (at 0.05 vol.% for Al 2 O 3) and 57% (at 0.075 vol.% for TiSiO 4). Other improvements were also found in forms of increase in heat transfer coefficient and decrease in evaporator wall temperature.

International Journal of Heat and Mass Transfer, 2012

As conventional energy sources like fossil fuels are getting rare, cost of energy production has ... more As conventional energy sources like fossil fuels are getting rare, cost of energy production has become higher as well as the concern of environmental pollution by burning of fossil fuels among the developed and developing nations. Solar energy is the most vastly available energy and very effective in terms of energy conversion. The most common solar thermal collector used is the black surface as radiant absorber but the thermal energy efficiency is low. In this study, the effect of nanofluid has been analyzed by using as working fluid for direct solar collector. The extinction coefficient of water based aluminum nanofluid has been investigated and evaluated by varying nanoparticle size and volume fraction. The particle size has minimal influence on the optical properties of nanofluid. On the other hand, the extinction coefficient is linearly proportionate to volume fraction. The improvement is promising within 1.0% volume fraction and the nanofluid is almost opaque to light wave.

International Journal of Computer Mathematics, 2007

In this paper we give an algorithm to generate all distributions of distinguishable objects to bi... more In this paper we give an algorithm to generate all distributions of distinguishable objects to bins without repetition. Our algorithm generates each distribution in constant time. To the best of our knowledge, our algorithm is the first algorithm which generates each solution in O(1) time in ordinary sense. As a byproduct of our algorithm, we get a new algorithm to enumerate all multiset partitions when the number of partitions is fixed and the partitions are numbered. In this case, our algorithm generates each multiset partition in constant time (in ordinary sense). Finally, we extend our algorithm for the case when the bins have priorities associated with them. Overall space complexity of our algorithm is O(km), where there are m bins and the objects fall into k different classes.

Effect of particle concentration, temperature and surfactant on surface tension of nanofluids

International Communications in Heat and Mass Transfer, 2013

ABSTRACT Heat transfer performance with nanofluids depends on the thermo physical properties of t... more ABSTRACT Heat transfer performance with nanofluids depends on the thermo physical properties of the suspension. Surface tension is an important property for heat transfer calculation. In this paper, various parameters that effect on the surface tension of nanofluids such as nanofluid preparation method, effect of volume fraction, temperature, and surfactants on nanofluids have been studied. Additionally, precise assessments on the theoretical correlations related to the surface tension of nanofluids have also been included. Based on the existing experimental results, surface tension augments respectively with volume fraction intensification. Surface tension of nanofluids decreases accordingly with the increase of temperature and surfactant concentration. Nevertheless, there have been some contradictory results on the effect of volume fraction and surfactant on surface tension of nanofluids.

A numerical study on the effect of a heated hollow cylinder on mixed convection in a ventilated cavity

International Communications in Heat and Mass Transfer, 2010

The present work is aimed to study mixed convection heat transfer characteristics within a ventil... more The present work is aimed to study mixed convection heat transfer characteristics within a ventilated square cavity having a heated hollow cylinder. The heated hollow cylinder is placed at the center of the cavity. In addition, the wall of the cavity is assumed to be adiabatic. Flows are imposed through the inlet at the bottom of the left wall and

Radiative properties of nanofluids

International Communications in Heat and Mass Transfer, 2013

ABSTRACT Compared to thermal conductivity and convection studies with nanofluids; the optical and... more ABSTRACT Compared to thermal conductivity and convection studies with nanofluids; the optical and radiative properties of nanofluids have received much less interest. However, very recently, the number of studies on radiative heat transfer in nanofluids has been increasing. This is due to the fact that, in general, a composite nanofluid has different properties than those found in either the base fluid or the particles. At high temperatures, knowledge of the resultant radiative properties becomes increasingly significant. The concept of using direct absorbing nanofluid (suspension formed by mixing nanoparticles and a liquid) recently been shown numerically and experimentally to be an efficient method for harvesting solar thermal energy. Nanofluid is a product of emerging field of nanotechnology, where nanoparticles (1–100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.). Nanofluids as an innovative class of heat transfer fluids represent a rapidly emerging research field where nano-science and thermal engineering coexist. Nanofluids are considered to be a two-phase system, comprised of a solid and a liquid phase. Compared to the base fluids like water or oil, nanofluids feature enhanced thermo-physical properties such as thermal diffusivity, viscosity, thermal conductivity, convective heat transfer coefficients, and optical properties. They offer unprecedented potential in many applications. Recent development in solar thermal collectors is the use of nanofluids to absorb the light directly. There is much current work going on the use of nanoparticles in several applications. With thousands of papers published every year, a comprehensive literature survey is impossible, and only selected representative publications are cited in this paper, particularly as they concern fundamental scientific insights on the fundamental optical properties of nanofluids.

Environmental Progress & Sustainable Energy, 2012

According to the source paper written in 2006, the Malaysian food industrial sector accounted for... more According to the source paper written in 2006, the Malaysian food industrial sector accounted for about 14% of the total manufacturing energy consumption. As energy costs rapidly increase, alternative energy sources and efficiency improvements become essential to energy planning, cost savings, resource optimization, and environmental protection in these industries. This article focuses on the energy savings, economic benefits, and emission reduction that can be obtained by applying various energy saving options. This study shows that significant power can be saved annually by utilizing energy efficient motors. The cost savings, payback period, and reduction in CO 2 emissions are estimated for different motor loads. It is shown that sizeable amounts of energy can be saved using VSD, waste heat recovery, new efficiency lamps (T-5), and repairing leakages. 2012 Ameri