tarek Meakhail - Academia.edu (original) (raw)

Papers by tarek Meakhail

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2007

Several experimental and theoretical investigations have been carried out to improve the performa... more Several experimental and theoretical investigations have been carried out to improve the performance of the jet pump through study of the influence of various geometric variables on its overall efficiency. To the best knowledge of the authors, none of these investigations studied the effect of the use of polymer solutions, e.g. carboxy methyl cellulose (CMC), as an agent of drag reduction on the jet pump performance, which is the objective of the present work. The present numerical study is carried out and compared with the previous experimental results explained in Gazzar et al. [1]. A computational fluid dynamics code is used to predict the performance of the jet pump and to shed more light on the mechanism of the mixing process especially if the primary stream is a Newtonian fluid, while the secondary stream is (the polymer solution) assumed to be a non-Newtonian fluid. Discussion and comparison between the experimental and theoretical results are included. The results of this comparison prove the validity of the computational code used, and illustrate the prominent effect of adding drag reduction agents (CMC) on jet pump performance.

The aim of this paper is to study experimentally the forced convective heat transfer behaviour of... more The aim of this paper is to study experimentally the forced convective heat transfer behaviour of Graphene oxide nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the pipe wall. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. GO particles dispersed in pure water are used as the working fluid. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity and viscosity in the turbulent flow. Four volume fractions of 0.05%, 0.10%, 0.15% and 0.20% are tested for GO/water nanofluids. The heat transfer within the flowing nanofluids were measured and compared with the corresponding data for base fluid (pure water). The Reynolds number is ranged from 3000 to 10000. It is found from the study that (i) heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with an increase in the particle volume fraction, (ii) the nanofluids have substantially higher value of Nusselt number than the same liquids without nanoparticles and the Nusselt number of nanofluids increase in accordance with an increase of the Reynolds number, (iii) heat transfer coefficient of nanofluid increase with Reynolds number, (iv) the viscosity, thermal conductivity, and electrical conductivity of Graphene oxide (GO) nanofluid increase in accordance with an increase of the volume fraction.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2008

An ejector is a pumping device that uses a high-speed primary fluid jet to entrain a secondary st... more An ejector is a pumping device that uses a high-speed primary fluid jet to entrain a secondary stream. The pumping action is due to the exchange of momentum between the primary and secondary streams. The air ejectors are widely used in mixing systems and many engineering applications. The purpose of the present work is to study experimentally the effects of using different numbers of nozzles with various geometric variables on the performance of the air ejector. The test rig, which is designed particularly for this study, is constructed so that the overall performance of the air ejector can be measured under various operating conditions. To the best knowledge of the authors, there is no published work concerning the study of all the geometric variables with different numbers of nozzles, showing their effect on the ejector performance. The experimental investigations consist of the performance measurements for 52 ejectors. They are classified into three main groups The following conc...

International Journal of Engineering Sciences and Research Technology, 2016

The aim of this paper is to study experimentally the forced convective heat transfer behaviour of... more The aim of this paper is to study experimentally the forced convective heat transfer behaviour of Graphene oxide nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the pipe wall. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. GO particles dispersed in pure water are used as the working fluid. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity and viscosity in the turbulent flow. Four volume fractions of 0.05%, 0.10%, 0.15% and 0.20% are tested for GO/water nanofluids. The heat transfer within the flowing nanofluids were measured and compared with the corresponding data for base fluid (pure water). The Reynolds number is ranged from 3000 to 10000. It is found from the study that (i) heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with an increase in the particle volume fraction, (ii) the nanoflu...

International Journal of Applied Energy Systems, 2020

This paper presents three dimensional numerical simulations of parabolic trough collectors (PTC) ... more This paper presents three dimensional numerical simulations of parabolic trough collectors (PTC) based on two low-Reynolds eddy viscosity turbulence models, namely; Launder and Sharma k-epsilon and k-omega SST models. For the simulations, water was used as the Heat Transfer Fluid (HTF) with four different nanoparticles; Al2O3, TiO2, CuO and Cu. Different volume fractions () of the nanoparticles were investigated for various Reynolds (Re) numbers with uniform heat flux. Results showed that the overall performance of the system is more sensitive to changes in the thermal properties of nanofluid than the thermal properties of the HTF. At a volume fraction of 6% and a Re number of 70,000, the Nusselt number (Nu) enhancement of nanofluids TiO2-water, Al2O3-water, CuOwater and Cu-water were found to be 21.5%, 20.2%, 18.11% and 15.7% respectively while the performance evaluation criteria (PEC) were 1.214, 1.2, 1.18 and 1.155 respectively.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2006

The overall efficiency of the jet pump is low compared with most of the other types of pumps. The... more The overall efficiency of the jet pump is low compared with most of the other types of pumps. The majority of previous investigations concentrated on the effect of its geometric ratios on its performance. To the best of the authors’ knowledge, there are no previous investigations on the effect of adding drag reduction agents to the fluid passing on its performance, which is the objective of the present investigation. The mixing process in this case is that of two streams: the primary stream is water (Newtonian fluid), whereas the secondary stream is a solution of certain polymer (considered to be non-Newtonian). Tests are carried out to study the effect of different concentrations of additives (carboxy methyl cellulose (CMC)) on the performance of the jet pump. The experimental results include characteristic curves for different area ratios, with different concentrations of CMC, as well as the wall static pressure distributions along the mixing chamber, diffuser, and outlet pipe. Th...

This study investigates (numerically and experimentally) airflow characteristics in multi-room bu... more This study investigates (numerically and experimentally) airflow characteristics in multi-room building for different ventilation patterns with the same air inlet flow rate. Seven ventilation patterns (full open, pass through, right short circuit, left short circuit, pass through plus right short circuit, pass through plus left short circuit, and (right and left short circuit) are considered to study multi-room airflow characteristics. Also, the effect of door opening percentage on airflow characteristics in multi-room buildings is studied. The results show that although the air flow rate is the same for the seven ventilation patterns the airflow characteristics are quite different for various ventilation patterns. The ventilation pattern has a major effect on the air change. Also, the results indicate that the door opening percentage affected airflow characteristics in multi-room buildings and the model predications are in good agreement with the experiments. Index Term-Airflow; Mu...

This paper reports velocity measurement data in the interaction region between the impeller and v... more This paper reports velocity measurement data in the interaction region between the impeller and vaned diffuser and the results of numerical flow simulation of the whole machine (impeller vaned diffuser and volute) of a single stage centrifugal fan. Two-dimensional instantaneous velocity measurement is done using particle image velocimetry (PIV). Numerical simulation of impeller-diffuser-volute interaction is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady calculation and a rotor-stator simulation model is used for the unsteady calculation using the steady results as an initial guess. The simulation results show that the separated flow regime near the diffuser hub extends to the volute. Comparison between the unsteady computation and those of measurement indicates that the rotor/stator model employed in the simulation predicts essential characteristics of unsteady flow in the centrifugal fan. However, quantitative agreement remains...

The aim of the present study is to investigate the thermal fluid flow transport phenomenon of gra... more The aim of the present study is to investigate the thermal fluid flow transport phenomenon of graphene oxide (GO) nanofluids in the heated horizontal stainless steel circular tube that was subjected to a uniform heat flux at its outer surface. The heat transfer and the pressure drop within flowing base fluid (pure water) were measured and compared with the corresponding data from the correlations. Consideration is given to the effects of volume fraction of the nanoparticle on the thermal conductivity, viscosity, and zeta potential. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. The convective heat transfer performance results show that the dispersed nanoparticles can always enhance the heat transfer coefficient of the base fluid, and the highest enhancement was obtained to be 181 % in the concentration of 0.2 vol.% of GO nanoparticles with Reynolds number 3000. The thermal conductivity enhancement depends strongly on the concentration of GO particles and increases with the increasing loading. It was also shown that the viscosity and pressure drop increase in accordance with an increase of the volume fraction.

An extensive program has been made to study the effect of many geometric variables under differen... more An extensive program has been made to study the effect of many geometric variables under different operating conditions on the performance of the jet pump at the National Water Research. This paper presents results of Computational Fluid Dynamic (CFD) analysis and experimental investigation of a water jet pump. The effect of driving pressure as well as the nozzle spacing has been investigated experimentally and numerically. Computational fluid dynamics (CFD) modeling studies were undertaken to understand the hydrodynamic characteristics with reference to the jet pump geometry. The CFD model also provides a basis for quantifying the effects of operating conditions on the pump performance. In this paper, the performance measurements are carried out for four driving pressures 1, 1.5,2, and 2.5 bar, also four values of nozzle spacing to throat diameter ratio are used, they are X= 0, 0.5, 0.75 and 1. The results show that the important findings of velocity profile and pressure distributi...

JES. Journal of Engineering Sciences

Regenerative pumps are turbomachines that achieve lower mass fluxes but higher-pressure differenc... more Regenerative pumps are turbomachines that achieve lower mass fluxes but higher-pressure differences than comparable pumps at the same circumferential velocity. The construction of these machines is very simple and inexpensive. On the other hand their efficiency does not exceed 45 % and they are noisy. To improve efficiency and reduce noise generation, a detailed knowledge of the unsteady flow in the machine is essential. In this work, we present unsteady flow characteristics of a typical regenerative pump based on numerical results obtained by using CFX-Tascflow code. The numerical results show highly unsteady pressure fluctuations around the stripper near both inlet and outlet ports. The lower pressure predicted near the inlet port indicates that the machine is prone to suffer cavitation problems. The amplitude of pressure fluctuation near the inlet is much higher than the outlet.

JES. Journal of Engineering Sciences

This paper presents the results of experimental investigation and Computational Fluid Dynamic (CF... more This paper presents the results of experimental investigation and Computational Fluid Dynamic (CFD) analysis of an air-air subsonic ejector. The CFD modeling is used to investigate the effect of mixing chamber length and area ratio (ratio of nozzle area to mixing chamber area) on the performance of the experimentally tested ejector. For short mixing chamber to diameter ratio MC=1.76 it is found that the separation region in the annular part occurs along the whole length of mixing chamber and extends to 60 percent of the diffuser length and the flow reattaches at an axial distance to diameter ratio X/D= 5. Increasing the mixing chamber length to MC=4.76, 6.76, 9.76 and 14.76, reduces the area of separation and the reattaching flow begins at an average value of axial distance X/D= 3.25. Increasing the MC to a value more than 6.76 has no meaning in the mixing process as it increases the friction losses in the mixing chamber. Increasing the area ratio from AR 1 =0.057 to AR 2 =0.171, the massive recirculation zone in the mixing chamber is reduced by about 50 percent and the pressure ratio increased by 21 percent with increasing the efficiency by 22 percent. Finally, the numerical performance curve agrees well with the experimental one.

International Conference on Aerospace Sciences and Aviation Technology

International Journal of Energy and Power Engineering

Various parameters affect the pump performance. The impeller outlet diameter, the blade angle, th... more Various parameters affect the pump performance. The impeller outlet diameter, the blade angle, the blade number and casing are the most critical. In this study, experimental and numerical investigations are carried out for two impellers different in diameter with the same casing. Numerical simulation of the whole machine (impeller, vaneless diffuser and volute) is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady state calculations and the rotor/stator model is used for the unsteady one. The model pump has a design rotation speed 2800 rpm and two impellers with 7 blades (70 mm and 105 mm outer diameters). For each pump, the performance measurements are measured and CFD analyses are carried out for different flow rates for steady and unsteady calculations. Finally, a comparison between the CFD and performance measurement is fairly good.

Journal of Energy and Power Engineering

A multi-heat pipe is a device for heat transmission. It is composed of a heating section, a cooli... more A multi-heat pipe is a device for heat transmission. It is composed of a heating section, a cooling section and an adiabatic section. The heating and cooling sections are the same and both are connected by four circular parallel tubes. This experimental study is performed to investigate heat transfer performance of a multi-heat pipe in the vertical orientation using pure water and GO (graphene oxide)/water nanofluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.1%, 0.15%, and 0.2% volume concentrations. The thermal performance has been investigated with varying heat flux in the range of 10-30 W and 100% fill charge ratio. Wall temperature, thermal resistance, and heat transfer coefficient of the heat pipe are measured and compared with those for the heat pipe using pure water. The experimental results show that the evaporator wall temperature with GO nanofluid is lower than that of the base fluid. Also, the heat pipe that charged with nanofluids showed lower thermal resistance compared with pure water. Heat transfer enhancement is caused by suspended nanoparticles and is pronounced with the increase in particle volume fraction.

World Journal of Nano Science and Engineering

This experimental study is performed to investigate heat transfer performance of a multi-heat pip... more This experimental study is performed to investigate heat transfer performance of a multi-heat pipe cooling device in the condition of different filling ratios (40%, 60%, 80% and 100%) and different constant heat fluxes (10-30 W). Here, pure water (distilled water) and graphene oxide (GO)/water nanofluids are employed respectively as working fluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.10%, 0.15%, and 0.20% volume concentrations. Multi-heat pipe is fabricated from copper; the heating and cooling sections are the same size and both are connected by four circular parallel tubes. Temperature fields and thermal resistance are measured for different filling ratio, heat fluxes and volume concentrations. The results indicated that the thermal performance of heat pipe increased with increasing the concentration of GO nanoparticles in the base fluid, while the maximum heat transfer enhancement was observed at 0.20% volume concentration. GO/ water nanofluids showed lower thermal resistance compared to pure water; the optimal thermal resistance was obtained at 100% filling charge ratio with 0.20% volume concentration. Studies were also demonstrated that heat transfer coefficient of the heat pipe significantly increases with increasing the input heat flux and GO nanoparticles concentration.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2011

The slurry jet pump with scouring nozzle system can be used in dredging of sites, which are diffi... more The slurry jet pump with scouring nozzle system can be used in dredging of sites, which are difficult to access or need handling of equipments that are used for the intake of pumping stations under bridges and concrete water channels. This system is suitable for sand, silt, sludge, mud, and other organic materials. The aim of this study is to investigate the performance of water and slurry jet pumps. The effects of the pump-operating conditions and geometries on its performance were investigated. The experimental rig was constructed in such a way that the driving nozzle diameter can be changed. In this study, three different diameters of driving nozzles, 10, 12.7, and 16 mm, have been used with one mixing chamber of 25.4 mm diameter (i.e. three different area ratios of R = 0.155, 0.25, and 0.4). Also, the effect of driving pressure has been investigated. The results show that increasing the area ratio decreases the maximum mass flow ratio. The results of computational fluid dynamics...

37th AIAA Thermophysics Conference, 2004

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2005

ABSTRACT Owing to their low specific speed, regenerative pumps allow high heads with small flow r... more ABSTRACT Owing to their low specific speed, regenerative pumps allow high heads with small flow rates and have performance curves with very stable features. This kind of pump is also smaller and simpler to construct than the other equivalent volumetric pumps, although it has fairly low efficiency. Over the past few years, regenerative pumps have been subject to more interest in various industrial applications. Previous mathematical models do not describe the flow characteristics very well as they are based on simplified assumptions. An improved model is proposed in this paper for the pump performance. The model can handle one inlet angle and two exit angles for the impeller blades and it can be used for the design of twisted blades that would increase the pump head and efficiency. A new feature of the pump characteristics based on the proposed model is discussed. It is shown that the proposed model yield results that are in good agreements with the experimental results. The new model also shows that the side-blade exit angle has a major effect on the performance of regenerative pump, which has not been accounted for in the previous theory.

Journal of Thermophysics and Heat Transfer, 2006

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2007

Several experimental and theoretical investigations have been carried out to improve the performa... more Several experimental and theoretical investigations have been carried out to improve the performance of the jet pump through study of the influence of various geometric variables on its overall efficiency. To the best knowledge of the authors, none of these investigations studied the effect of the use of polymer solutions, e.g. carboxy methyl cellulose (CMC), as an agent of drag reduction on the jet pump performance, which is the objective of the present work. The present numerical study is carried out and compared with the previous experimental results explained in Gazzar et al. [1]. A computational fluid dynamics code is used to predict the performance of the jet pump and to shed more light on the mechanism of the mixing process especially if the primary stream is a Newtonian fluid, while the secondary stream is (the polymer solution) assumed to be a non-Newtonian fluid. Discussion and comparison between the experimental and theoretical results are included. The results of this comparison prove the validity of the computational code used, and illustrate the prominent effect of adding drag reduction agents (CMC) on jet pump performance.

The aim of this paper is to study experimentally the forced convective heat transfer behaviour of... more The aim of this paper is to study experimentally the forced convective heat transfer behaviour of Graphene oxide nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the pipe wall. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. GO particles dispersed in pure water are used as the working fluid. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity and viscosity in the turbulent flow. Four volume fractions of 0.05%, 0.10%, 0.15% and 0.20% are tested for GO/water nanofluids. The heat transfer within the flowing nanofluids were measured and compared with the corresponding data for base fluid (pure water). The Reynolds number is ranged from 3000 to 10000. It is found from the study that (i) heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with an increase in the particle volume fraction, (ii) the nanofluids have substantially higher value of Nusselt number than the same liquids without nanoparticles and the Nusselt number of nanofluids increase in accordance with an increase of the Reynolds number, (iii) heat transfer coefficient of nanofluid increase with Reynolds number, (iv) the viscosity, thermal conductivity, and electrical conductivity of Graphene oxide (GO) nanofluid increase in accordance with an increase of the volume fraction.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2008

An ejector is a pumping device that uses a high-speed primary fluid jet to entrain a secondary st... more An ejector is a pumping device that uses a high-speed primary fluid jet to entrain a secondary stream. The pumping action is due to the exchange of momentum between the primary and secondary streams. The air ejectors are widely used in mixing systems and many engineering applications. The purpose of the present work is to study experimentally the effects of using different numbers of nozzles with various geometric variables on the performance of the air ejector. The test rig, which is designed particularly for this study, is constructed so that the overall performance of the air ejector can be measured under various operating conditions. To the best knowledge of the authors, there is no published work concerning the study of all the geometric variables with different numbers of nozzles, showing their effect on the ejector performance. The experimental investigations consist of the performance measurements for 52 ejectors. They are classified into three main groups The following conc...

International Journal of Engineering Sciences and Research Technology, 2016

The aim of this paper is to study experimentally the forced convective heat transfer behaviour of... more The aim of this paper is to study experimentally the forced convective heat transfer behaviour of Graphene oxide nanofluids inside a horizontal circular tube subject to a constant and uniform heat flux at the pipe wall. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. GO particles dispersed in pure water are used as the working fluid. Consideration is given to the effect of the inclusion of nanoparticles on heat transfer enhancement, thermal conductivity and viscosity in the turbulent flow. Four volume fractions of 0.05%, 0.10%, 0.15% and 0.20% are tested for GO/water nanofluids. The heat transfer within the flowing nanofluids were measured and compared with the corresponding data for base fluid (pure water). The Reynolds number is ranged from 3000 to 10000. It is found from the study that (i) heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with an increase in the particle volume fraction, (ii) the nanoflu...

International Journal of Applied Energy Systems, 2020

This paper presents three dimensional numerical simulations of parabolic trough collectors (PTC) ... more This paper presents three dimensional numerical simulations of parabolic trough collectors (PTC) based on two low-Reynolds eddy viscosity turbulence models, namely; Launder and Sharma k-epsilon and k-omega SST models. For the simulations, water was used as the Heat Transfer Fluid (HTF) with four different nanoparticles; Al2O3, TiO2, CuO and Cu. Different volume fractions () of the nanoparticles were investigated for various Reynolds (Re) numbers with uniform heat flux. Results showed that the overall performance of the system is more sensitive to changes in the thermal properties of nanofluid than the thermal properties of the HTF. At a volume fraction of 6% and a Re number of 70,000, the Nusselt number (Nu) enhancement of nanofluids TiO2-water, Al2O3-water, CuOwater and Cu-water were found to be 21.5%, 20.2%, 18.11% and 15.7% respectively while the performance evaluation criteria (PEC) were 1.214, 1.2, 1.18 and 1.155 respectively.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2006

The overall efficiency of the jet pump is low compared with most of the other types of pumps. The... more The overall efficiency of the jet pump is low compared with most of the other types of pumps. The majority of previous investigations concentrated on the effect of its geometric ratios on its performance. To the best of the authors’ knowledge, there are no previous investigations on the effect of adding drag reduction agents to the fluid passing on its performance, which is the objective of the present investigation. The mixing process in this case is that of two streams: the primary stream is water (Newtonian fluid), whereas the secondary stream is a solution of certain polymer (considered to be non-Newtonian). Tests are carried out to study the effect of different concentrations of additives (carboxy methyl cellulose (CMC)) on the performance of the jet pump. The experimental results include characteristic curves for different area ratios, with different concentrations of CMC, as well as the wall static pressure distributions along the mixing chamber, diffuser, and outlet pipe. Th...

This study investigates (numerically and experimentally) airflow characteristics in multi-room bu... more This study investigates (numerically and experimentally) airflow characteristics in multi-room building for different ventilation patterns with the same air inlet flow rate. Seven ventilation patterns (full open, pass through, right short circuit, left short circuit, pass through plus right short circuit, pass through plus left short circuit, and (right and left short circuit) are considered to study multi-room airflow characteristics. Also, the effect of door opening percentage on airflow characteristics in multi-room buildings is studied. The results show that although the air flow rate is the same for the seven ventilation patterns the airflow characteristics are quite different for various ventilation patterns. The ventilation pattern has a major effect on the air change. Also, the results indicate that the door opening percentage affected airflow characteristics in multi-room buildings and the model predications are in good agreement with the experiments. Index Term-Airflow; Mu...

This paper reports velocity measurement data in the interaction region between the impeller and v... more This paper reports velocity measurement data in the interaction region between the impeller and vaned diffuser and the results of numerical flow simulation of the whole machine (impeller vaned diffuser and volute) of a single stage centrifugal fan. Two-dimensional instantaneous velocity measurement is done using particle image velocimetry (PIV). Numerical simulation of impeller-diffuser-volute interaction is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady calculation and a rotor-stator simulation model is used for the unsteady calculation using the steady results as an initial guess. The simulation results show that the separated flow regime near the diffuser hub extends to the volute. Comparison between the unsteady computation and those of measurement indicates that the rotor/stator model employed in the simulation predicts essential characteristics of unsteady flow in the centrifugal fan. However, quantitative agreement remains...

The aim of the present study is to investigate the thermal fluid flow transport phenomenon of gra... more The aim of the present study is to investigate the thermal fluid flow transport phenomenon of graphene oxide (GO) nanofluids in the heated horizontal stainless steel circular tube that was subjected to a uniform heat flux at its outer surface. The heat transfer and the pressure drop within flowing base fluid (pure water) were measured and compared with the corresponding data from the correlations. Consideration is given to the effects of volume fraction of the nanoparticle on the thermal conductivity, viscosity, and zeta potential. Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method. The convective heat transfer performance results show that the dispersed nanoparticles can always enhance the heat transfer coefficient of the base fluid, and the highest enhancement was obtained to be 181 % in the concentration of 0.2 vol.% of GO nanoparticles with Reynolds number 3000. The thermal conductivity enhancement depends strongly on the concentration of GO particles and increases with the increasing loading. It was also shown that the viscosity and pressure drop increase in accordance with an increase of the volume fraction.

An extensive program has been made to study the effect of many geometric variables under differen... more An extensive program has been made to study the effect of many geometric variables under different operating conditions on the performance of the jet pump at the National Water Research. This paper presents results of Computational Fluid Dynamic (CFD) analysis and experimental investigation of a water jet pump. The effect of driving pressure as well as the nozzle spacing has been investigated experimentally and numerically. Computational fluid dynamics (CFD) modeling studies were undertaken to understand the hydrodynamic characteristics with reference to the jet pump geometry. The CFD model also provides a basis for quantifying the effects of operating conditions on the pump performance. In this paper, the performance measurements are carried out for four driving pressures 1, 1.5,2, and 2.5 bar, also four values of nozzle spacing to throat diameter ratio are used, they are X= 0, 0.5, 0.75 and 1. The results show that the important findings of velocity profile and pressure distributi...

JES. Journal of Engineering Sciences

Regenerative pumps are turbomachines that achieve lower mass fluxes but higher-pressure differenc... more Regenerative pumps are turbomachines that achieve lower mass fluxes but higher-pressure differences than comparable pumps at the same circumferential velocity. The construction of these machines is very simple and inexpensive. On the other hand their efficiency does not exceed 45 % and they are noisy. To improve efficiency and reduce noise generation, a detailed knowledge of the unsteady flow in the machine is essential. In this work, we present unsteady flow characteristics of a typical regenerative pump based on numerical results obtained by using CFX-Tascflow code. The numerical results show highly unsteady pressure fluctuations around the stripper near both inlet and outlet ports. The lower pressure predicted near the inlet port indicates that the machine is prone to suffer cavitation problems. The amplitude of pressure fluctuation near the inlet is much higher than the outlet.

JES. Journal of Engineering Sciences

This paper presents the results of experimental investigation and Computational Fluid Dynamic (CF... more This paper presents the results of experimental investigation and Computational Fluid Dynamic (CFD) analysis of an air-air subsonic ejector. The CFD modeling is used to investigate the effect of mixing chamber length and area ratio (ratio of nozzle area to mixing chamber area) on the performance of the experimentally tested ejector. For short mixing chamber to diameter ratio MC=1.76 it is found that the separation region in the annular part occurs along the whole length of mixing chamber and extends to 60 percent of the diffuser length and the flow reattaches at an axial distance to diameter ratio X/D= 5. Increasing the mixing chamber length to MC=4.76, 6.76, 9.76 and 14.76, reduces the area of separation and the reattaching flow begins at an average value of axial distance X/D= 3.25. Increasing the MC to a value more than 6.76 has no meaning in the mixing process as it increases the friction losses in the mixing chamber. Increasing the area ratio from AR 1 =0.057 to AR 2 =0.171, the massive recirculation zone in the mixing chamber is reduced by about 50 percent and the pressure ratio increased by 21 percent with increasing the efficiency by 22 percent. Finally, the numerical performance curve agrees well with the experimental one.

International Conference on Aerospace Sciences and Aviation Technology

International Journal of Energy and Power Engineering

Various parameters affect the pump performance. The impeller outlet diameter, the blade angle, th... more Various parameters affect the pump performance. The impeller outlet diameter, the blade angle, the blade number and casing are the most critical. In this study, experimental and numerical investigations are carried out for two impellers different in diameter with the same casing. Numerical simulation of the whole machine (impeller, vaneless diffuser and volute) is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady state calculations and the rotor/stator model is used for the unsteady one. The model pump has a design rotation speed 2800 rpm and two impellers with 7 blades (70 mm and 105 mm outer diameters). For each pump, the performance measurements are measured and CFD analyses are carried out for different flow rates for steady and unsteady calculations. Finally, a comparison between the CFD and performance measurement is fairly good.

Journal of Energy and Power Engineering

A multi-heat pipe is a device for heat transmission. It is composed of a heating section, a cooli... more A multi-heat pipe is a device for heat transmission. It is composed of a heating section, a cooling section and an adiabatic section. The heating and cooling sections are the same and both are connected by four circular parallel tubes. This experimental study is performed to investigate heat transfer performance of a multi-heat pipe in the vertical orientation using pure water and GO (graphene oxide)/water nanofluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.1%, 0.15%, and 0.2% volume concentrations. The thermal performance has been investigated with varying heat flux in the range of 10-30 W and 100% fill charge ratio. Wall temperature, thermal resistance, and heat transfer coefficient of the heat pipe are measured and compared with those for the heat pipe using pure water. The experimental results show that the evaporator wall temperature with GO nanofluid is lower than that of the base fluid. Also, the heat pipe that charged with nanofluids showed lower thermal resistance compared with pure water. Heat transfer enhancement is caused by suspended nanoparticles and is pronounced with the increase in particle volume fraction.

World Journal of Nano Science and Engineering

This experimental study is performed to investigate heat transfer performance of a multi-heat pip... more This experimental study is performed to investigate heat transfer performance of a multi-heat pipe cooling device in the condition of different filling ratios (40%, 60%, 80% and 100%) and different constant heat fluxes (10-30 W). Here, pure water (distilled water) and graphene oxide (GO)/water nanofluids are employed respectively as working fluid. GO/water nanofluids were synthesized by the modified Hummers method with 0.05%, 0.10%, 0.15%, and 0.20% volume concentrations. Multi-heat pipe is fabricated from copper; the heating and cooling sections are the same size and both are connected by four circular parallel tubes. Temperature fields and thermal resistance are measured for different filling ratio, heat fluxes and volume concentrations. The results indicated that the thermal performance of heat pipe increased with increasing the concentration of GO nanoparticles in the base fluid, while the maximum heat transfer enhancement was observed at 0.20% volume concentration. GO/ water nanofluids showed lower thermal resistance compared to pure water; the optimal thermal resistance was obtained at 100% filling charge ratio with 0.20% volume concentration. Studies were also demonstrated that heat transfer coefficient of the heat pipe significantly increases with increasing the input heat flux and GO nanoparticles concentration.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2011

The slurry jet pump with scouring nozzle system can be used in dredging of sites, which are diffi... more The slurry jet pump with scouring nozzle system can be used in dredging of sites, which are difficult to access or need handling of equipments that are used for the intake of pumping stations under bridges and concrete water channels. This system is suitable for sand, silt, sludge, mud, and other organic materials. The aim of this study is to investigate the performance of water and slurry jet pumps. The effects of the pump-operating conditions and geometries on its performance were investigated. The experimental rig was constructed in such a way that the driving nozzle diameter can be changed. In this study, three different diameters of driving nozzles, 10, 12.7, and 16 mm, have been used with one mixing chamber of 25.4 mm diameter (i.e. three different area ratios of R = 0.155, 0.25, and 0.4). Also, the effect of driving pressure has been investigated. The results show that increasing the area ratio decreases the maximum mass flow ratio. The results of computational fluid dynamics...

37th AIAA Thermophysics Conference, 2004

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2005

ABSTRACT Owing to their low specific speed, regenerative pumps allow high heads with small flow r... more ABSTRACT Owing to their low specific speed, regenerative pumps allow high heads with small flow rates and have performance curves with very stable features. This kind of pump is also smaller and simpler to construct than the other equivalent volumetric pumps, although it has fairly low efficiency. Over the past few years, regenerative pumps have been subject to more interest in various industrial applications. Previous mathematical models do not describe the flow characteristics very well as they are based on simplified assumptions. An improved model is proposed in this paper for the pump performance. The model can handle one inlet angle and two exit angles for the impeller blades and it can be used for the design of twisted blades that would increase the pump head and efficiency. A new feature of the pump characteristics based on the proposed model is discussed. It is shown that the proposed model yield results that are in good agreements with the experimental results. The new model also shows that the side-blade exit angle has a major effect on the performance of regenerative pump, which has not been accounted for in the previous theory.

Journal of Thermophysics and Heat Transfer, 2006