In this study, the performance of the helical coil heat exchanger is experimentally tested. The r... more In this study, the performance of the helical coil heat exchanger is experimentally tested. The results are statistically analyzed using the response surface methodology (RSM) to optimize the heat exchanger response under various parameters. The helical coil outlet temperature is measured as the heat exchanger response. The considered parameters, affecting the performance, are the inlet temperature and pressure to the helical coil in addition to the water bath temperature surrounding the coil. Also, the mutual interactions between these parameters and their influences on the response of the helical coil are evaluated. This study is carried out in two parts, the first part is devoted to perform the experimental tests, and the second part deals statistically with the modelling and optimization of these results. Design of experiments (DOE) is provided according to the full factorial design method. Three parameters with three levels lead to performing 27 experimental runs. Finally, the ...
This investigation presents a computer simulation of gas-steam turbine combined cycle used in hot... more This investigation presents a computer simulation of gas-steam turbine combined cycle used in hot dry weather countries. Water is injected into compressor inlet air to alleviate the inlet air temperature and in turn improve the gas turbine output power and efficiency. The gas turbine simulation model is used following [1] and a standard Rankine steam cycle is employed in cascade with the gas turbine cycle. The turbine exhaust gases, instead of disposing to the ambient, are used in three heat exchangers arranged in series to provide all the required heat for steam cycle. The heat exchangers are simulated by the effectiveness-NTU method to obtain the off-design performance. The steam properties and the psychometric air properties are evaluated during the simulation by a linked computer code developed by the author. The results show that, the energy recovery in steam turbine produce power as much as one half of gas turbine output power. A combined efficiency in the range of 45% is reac...
The heat transfer, friction factor, and collector efficiency are estimated experimentally for mul... more The heat transfer, friction factor, and collector efficiency are estimated experimentally for multi-walled carbon nanotubes+Fe3O4 hybrid nanofluid flows in a solar flat plate collector under thermosyphon circulation. The combined technique of in-situ growth and chemical coprecipitation was utilized to synthesize the multi-walled carbon nanotubes+Fe3O4 hybrid nanoparticles. The experiments were carried out at volume flow rates from 0.1 to 0.75 L/min and various concentrations from 0.05% to 0.3%. The viscosity and thermal conductivity of the hybrid nanofluids were experimentally measured at different temperatures and concentrations. Due to the improved thermophysical properties of the hybrid nanofluids, the collector achieved better thermal efficiency. Results show that the maximum thermal conductivity and viscosity enhancements are 28.46% and 50.4% at 0.3% volume concentration and 60 °C compared to water data. The Nusselt number, heat transfer coefficient, and friction factor are aug...
This paper investigates the vibration control, stability, and energy transfer of the offshore win... more This paper investigates the vibration control, stability, and energy transfer of the offshore wind turbine tower system with control force and nonlinearity terms. A nonlinear proportional derivative (NPD) controller was connected to the system to reduce a high oscillation amplitude and to transfer the energy in the wind turbine system. Furthermore, the averaging method and Poincaré maps were used with respect to the controlled system to study the stability and bifurcation analysis in the worst resonance cases. The curves of force response and frequency response were plotted before and after the control unit was added to the wind turbine system. In addition, we discuss the performances of the control parameters on the vibration magnitudes. Numerical simulations were carried out with Maple and Matlab algorithms to confirm the analytical results. The results show the effectiveness of the NPD controller in suppressing the nonlinear oscillations of the wind turbine system.
A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is... more A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is given using BACKONE equation of state. The fluids are alkanes, fluorinated alkanes, ethers and fluorinated ethers. The ORC cycles operate between 100 and 30 1C typical for geothermal power plants at pressures mostly limited to 20 bar, but in some cases supercritical pressures are also considered. Thermal efficiencies Z th are presented for cycles of different types. In case of subcritical pressure processes one has to distinguish (1) whether the shape of the saturated vapour line in the T,s-diagram is bell-shaped or overhanging, and (2) whether the vapour entering the turbine is saturated or superheated. Moreover, in case that the vapour leaving the turbine is superheated, an internal heat exchanger (IHE) may be used. The highest Z th-values are obtained for the high boiling substances with overhanging saturated vapour line in subcritical processes with an IHE, e.g., for n-butane Z th ¼ 0.130. On the other hand, a pinch analysis for the heat transfer from the heat carrier with maximum temperature of 120 1C to the working fluid shows that the largest amount of heat can be transferred to a supercritical fluid and the least to a high-boiling subcritical fluid.
A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is... more A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is given using BACKONE equation of state. The fluids are alkanes, fluorinated alkanes, ethers and fluorinated ethers. The ORC cycles operate between 100 and 30 1C typical for geothermal power plants at pressures mostly limited to 20 bar, but in some cases supercritical pressures are also considered. Thermal efficiencies Z th are presented for cycles of different types. In case of subcritical pressure processes one has to distinguish (1) whether the shape of the saturated vapour line in the T,s-diagram is bell-shaped or overhanging, and (2) whether the vapour entering the turbine is saturated or superheated. Moreover, in case that the vapour leaving the turbine is superheated, an internal heat exchanger (IHE) may be used. The highest Z th-values are obtained for the high boiling substances with overhanging saturated vapour line in subcritical processes with an IHE, e.g., for n-butane Z th ¼ 0.130. On the other hand, a pinch analysis for the heat transfer from the heat carrier with maximum temperature of 120 1C to the working fluid shows that the largest amount of heat can be transferred to a supercritical fluid and the least to a high-boiling subcritical fluid.
In the transcritical carbon dioxide vapor compression cycle heat is rejected in a gas cooler at s... more In the transcritical carbon dioxide vapor compression cycle heat is rejected in a gas cooler at supercritical pressure. At supercritical heat rejection the refrigerant temperature and pressure are independent on each other and one of the most important parameters affect on cycle performance is the pressure on the heat rejection side called the high pressure. A theoretical analysis shows the effect of high pressure, superheat, evaporator and gas cooler exit temperature, and gas cooler exit temperature approach on performance of a transcritical carbon dioxide vapor compression cycle was investigated in this study. The study defines an optimal high pressure which gives a maximum coefficient of performance and suggests that the cycle should operate at or near its optimal high pressure in order to keep its maximum coefficient of performance. The high pressure will also affect the cooling capacity and this effect can be used for boosting capacity at high ambient temperatures. The effect of gas cooler exit temperature and compressor inlet temperature on the optimal high pressure also was investigated. The study shows that the optimum high pressure is mainly a function of gas cooler exit temperature and compressor inlet temperature, while the value of the maximum coefficient of performance is dependent on the gas cooler exit and evaporating temperature. The study also indicates that the superheat of the gas at compressor inlet will have a positive effect on the coefficient of performance when operating with high heat rejection pressure at high ambient temperatures with high evaporating temperatures.
The potential use of many common hydrofluorocarbons and hydrocarbons as well as new hydrofluorool... more The potential use of many common hydrofluorocarbons and hydrocarbons as well as new hydrofluoroolefins, i.e. R1234yf and R1234ze(E) working fluids for a combined organic Rankine cycle and vapor compression refrigeration (ORC-VCR) system activated by low-grade thermal energy is evaluated. The basic ORC operates between 80 and 40°C typical for low-grade thermal energy power plants while the basic VCR cycle operates between 5 and 40°C. The system performance is characterized by the overall system coefficient of performance (COP S) and the total mass flow rate of the working fluid for each kW cooling capacity (_ m total). The effects of different working parameters such as the evaporator, condenser, and boiler temperatures on the system performance are examined. The results illustrate that the maximum COP S values are attained using the highest boiling candidates with overhanging T-s diagram, i.e. R245fa and R600, while R600 has the lowest _ m total under the considered operating conditions. Among the proposed candidates, R600 is the best candidate for the ORC-VCR system from the perspectives of environmental issues and system performance. Nevertheless, its flammability should attract enough attention. The maximum COP S using R600 is found to reach up to 0.718 at a condenser temperature of 30°C and the basic values for the remaining parameters.
To enhance the surface of a material with the desired qualities for diverse applications in servi... more To enhance the surface of a material with the desired qualities for diverse applications in service, a variety of thermal and thermo-chemical surface treatment processes are used. Due to the high-velocity impact inherent in the process, high-velocity oxy-fuel (HVOF) spray is now frequently employed in industrial applications for its ability to generate a high-quality coating with appropriate hardness and low oxide content. In this investigation, a high-velocity oxy-fuel (HVOF) thermal spraying process was utilized to coat WC-10Co powders on a 35CrMo steel substrate. A water jet erosion test was also used to examine the substrate and coated samples’ erosion behavior. The erosion rate was systematically investigated using water jet variables such as the angle of impingement, water jet velocity, standoff distance, and erodent discharge. For the development of multiple regression models, experiments were performed utilizing the central composite rotatable design and the response surface...
The focal point of this study was to use the waste foundry sand (WFS) in the remediation of simul... more The focal point of this study was to use the waste foundry sand (WFS) in the remediation of simulated aqueous solution contaminated with ammonia nitrogen through batch and column tests. Recycling this waste is a real application for sustainable principles because it will reduce disposal costs and the required area in the sanitary landfill. Based on the kinetic sorption measurements for ammonia nitrogen onto WFS, the predominant mechanism was the chemisorption because the measurements were well fitted with the pseudo-second-order model. In comparison with the Freundlich model, the sorption isotherm data were well formulated by models of Langmuir and Sips with a maximum adsorption capacity of 1.152 mg/g. The breakthrough curves for a duration of 80 h certified that the two weight ratios (10:90 and 20:80) of WFS:sand were suitable for maintaining the reactivity and conductivity of permeable reactive barrier (PRB) for pollutant under consideration. The results proved that the increasing of WFS and bed depth increased the breakthrough and saturation times with the sorption capacity of the barrier. Also, the appearance of these curves was directly proportional to the inlet concentration of pollutants and the flow rate of contaminated water. Statistical measures specifically Nash-Sutcliffe efficiency and coefficient of determination were proved that the breakthrough curves were well described by Thomas, Belter, and Yan models.
The evaluation of groundwater quality in the Dammam formation, Faddak farm, Karbala Governorate, ... more The evaluation of groundwater quality in the Dammam formation, Faddak farm, Karbala Governorate, Iraq proved that the sulfate (SO42−) concentrations have high values; so, this water is not suitable for livestock, poultry and irrigation purposes. For reclamation of this water, manufacturing of new sorbent for permeable reactive barrier was required through precipitation of Mg and Fe hydroxides nanoparticles on the activated carbon (AC) surface with best Mg/Fe molar ratio of 7.5/2.5. Mixture of 50% coated AC and 50% scrap iron was applied to eliminate SO42− from contaminated water with efficiency of 59% and maximum capacity of adsorption equals to 9.5 mg/g for a time period of 1 h, sorbent dosage 40 g/L, and initial pH = 5 at 50 mg/L initial SO42− concentration and 200 rpm shaking speed. Characterization analyses certified that the plantation of Mg and Fe nanoparticles onto AC was achieved. Continuous tests showed that the longevity of composite sorbent is increased with thicker bed a...
Lightweight composite materials have recently been recognized as appropriate materials have been ... more Lightweight composite materials have recently been recognized as appropriate materials have been adopted in many industrial applications because of their versatility. The present research recognizes the inclusion of ceramics such as Gr and B4C in manufacturing AMMCs through stir casting. Prepared composites were tested for hardness and wear behaviour. The tests’ findings revealed that the reinforced matrix was harder (60%) than the un-reinforced alloy because of the increased ceramic phase. The rising content of B4C and Gr particles led to continuous improvements in wear resistance. The microstructure and worn surface were observed through SEM (Scanning electron microscope) and revealed the formation of mechanically mixed layers of both B4C and Gr, which served as the effective insulation surface and protected the test sample surface from the steel disc. With the rise in the content of B4C and Gr, the weight loss declined, and significant wear resistance was achieved at 15 wt.% B4C ...
In this article, the performance and working fluid selection for an organic Rankine cycle-vapor c... more In this article, the performance and working fluid selection for an organic Rankine cycle-vapor compression refrigeration (ORC–VCR) integrated system activated by renewable energy is investigated. The performance of the system is described by the system coefficient of performance (COPS), and the refrigerant mass flow rate per kilowatt refrigeration capacity (m˙total). Twenty-three pure substances are proposed as working fluids for the integrated system. The basic integrated system performance is assessed and compared using the proposed working fluids. The basic VCR cycle works between 35 and 0 °C, while the basic ORC works between 35 and 100 °C. The impacts of different operating parameters such as the evaporator, the boiler, and the condenser temperatures on the ORC–VCR system performance are also examined. The results show that the cyclopentane accomplished the highest system performance under all investigated operating conditions. Accordingly, among the examined 23 working fluids...
Purpose The aim of this paper is to evaluate the effect of surface treatment on slurry erosion be... more Purpose The aim of this paper is to evaluate the effect of surface treatment on slurry erosion behavior of AISI 5,117 steel using artificial neural network (ANN) technique. Design/methodology/approach The slurry erosion wear behavior of electroless nickel-phosphorus (Ni-P) coated, carburized and untreated AISI 5,117 alloy steel was investigated experimentally and theoretically using ANN technique based on error back propagation learning algorithm. Findings From the obtained results, it can be concluded that the proposed AAN model can be successfully used for evaluating slurry erosion behavior of the Ni-P coated, carburized and untreated AISI 5,117 steel for wide range of operating conditions and Ni-P coating and carburizing improve the slurry erosion resistance of AISI 5,117 steel; however, the coating is more efficient. Originality/value Slurry erosion is a serious problem for the performance, reliability and service life of engineering components used in many industrial applicatio...
The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat u... more The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat using 18 organic working fluids is presented. Several parameters, such as the net power output, exergy efficiency, expander size parameter (SP), and heat exchanger requirement of evaporator and the condenser, were used to evaluate the performance of this recovery cycle and screen the working fluids. The results reveal that in most cases, raising the expander inlet temperature is helpful to improve the net power output and the exergy efficiency. However, the effect of the expander inlet pressure on those parameters is related to the expander inlet temperature and working fluid used. Either lower expander inlet temperature and pressure, or higher expander inlet temperature and pressure, generally makes the net power output more. Lower expander inlet temperature results in larger total heat transfer requirement and expander size. According to the screening criteria of both the higher output and the lower investment, the following working fluids for the supercritical ORC system are recommended: R152a and R143a.
Abstract The utilization of electronic expansion valves (EEVs) in refrigeration and air condition... more Abstract The utilization of electronic expansion valves (EEVs) in refrigeration and air conditioning systems is increased for energy saving and comfort environmental. However, experimental data and refrigerant mass flow models through EEVs are very limited in open literature. In this study, a new technique using artificial neural network (ANN) is applied to depict the mass flow rates of R22 and its alternatives R407C and R410A flowing through EEVs based on the error back propagation learning algorithm. Two strategies are followed; the first is to construct individual ANN models for each refrigerant, and the second is to construct a generalized ANN model for the three investigated refrigerants. The experimental results from open literature are used to construct the ANN models. The ANN models results showed a good agreement with the corresponding experimental data. For individual models, the relative deviations for R22, R407C, and R410A are within ±0.7%, ±1.1%, and ±0.006%, respectively. While for generalized model, the relative deviations are within ±2.5%. Also the generalized model was tested out of its construction range in a predictive mode and it was found to be a reliable tool to estimate the refrigerants mass flow rates.
The present work is represented by the derivation of mathematical model and solving the model ana... more The present work is represented by the derivation of mathematical model and solving the model analytically using the method of separation of variables to describe the migration of the contaminant metal ions through a column packed with bed of permeable reactive barrier (PRB). The validity of the solution can be evaluated through the simulation of cadmium and chromium ions using scrap iron and/or aluminum by-products in the form of wastes that if not utilized to treat waste by waste can impose further burden over the ecosystem. Breakthrough curves proved that the increase of metal ions velocity will decrease the capturing of the ions; therefore, the distribution coefficient and the retardation factor also decrease. Furthermore, the increase of barrier depth will increase the longevity of PRB because this will delay the migration of contaminant. A mathematical model has acceptable ability in the representation of experimental measurements with Nash-Sutcliff efficiency coefficients greater than 0.98. The longevity of the PRB was estimated for the field scale to be 210 and 250 d to produce contaminant effluent beyond 100 cm barrier matrix within the environmental permissible concentrations. Although groundwater velocity is highly variable, a proposed velocity of 0.25 cm/min which is assumed to be analogous to the groundwater velocity has revealed prolonged longevity of 7.02 y for the capture of chromium.
The effect of viscosity on the wear particles produced by vibratory cavitation erosion tests on A... more The effect of viscosity on the wear particles produced by vibratory cavitation erosion tests on Al-99.92 in distilled water and glycerol-water solutions was analyzed. Scanning electron microscope images of wear particles during incubation period were obtained. The surface topography examination revealed that the erosion particles were formed by fatigue. The particles removed from glycerol-water solutions differ from that formed in distilled water, where fatigue striations formed on the particle surface for glycerol-water solutions and not formed for distilled water. Therefore, the stress produced by cavitation bubbles decreases with increase of viscosity.
Purpose This paper aims to investigate the performance and working fluids screening for an ejecto... more Purpose This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are proposed as refrigerants for the ERC to determine the most appropriate one. Design/methodology/approach The ejector performance is characterized by the ejector area ratio (EAR) and entrainment ratio (ω), while the cycle performance is described by the coefficient of performance (COP). The influences of many working parameters like the evaporator, condenser and generator temperatures on the ejector and cycle performances are investigated for all candidates as well. Findings The results indicate that the best ejector and cycle performances are attained with the highest critical temperature dry refrigerant, i.e. R601 under all studied working conditions. From the perspective of energy efficiency and environmental issues, R601 can be con...
In this study, the performance of an integrated desiccant air conditioning system (IDACS) activat... more In this study, the performance of an integrated desiccant air conditioning system (IDACS) activated by solar energy is evaluated by back propagation artificial neural network (BP-ANN). The IDACS consists of a liquid desiccant dehumidification cycle combined with a vapor compression refrigeration cycle. The integrated system performance is assessed utilizing the system coefficient of performance (COP), outlet dry air temperature (T da-out), and specific moisture removal (SMR). The training of the BP-ANN is accomplished utilizing experimental results previously published. The results of the BP-ANN model revealed the high accuracy in predicting system performance parameters compared with experimental values. The BP-ANN model has shown relative errors in the trained mode for COP, T da-out , and SMR within ±0.005%, ±0.006%, and ±0.05%, respectively. On the other side, the BP-ANN model is inspected in the predictive mode as well. The relative errors of the model for COP, T da-out , and SMR in the predictive mode are within ±0.006%, ±0.006%, and ±0.004%, respectively. The influences of some selected parameters, namely regeneration temperature, desiccant solution temperature in the condenser and evaporator, and strong solution concentration on the system performance are examined and discussed as well.
In this study, the performance of the helical coil heat exchanger is experimentally tested. The r... more In this study, the performance of the helical coil heat exchanger is experimentally tested. The results are statistically analyzed using the response surface methodology (RSM) to optimize the heat exchanger response under various parameters. The helical coil outlet temperature is measured as the heat exchanger response. The considered parameters, affecting the performance, are the inlet temperature and pressure to the helical coil in addition to the water bath temperature surrounding the coil. Also, the mutual interactions between these parameters and their influences on the response of the helical coil are evaluated. This study is carried out in two parts, the first part is devoted to perform the experimental tests, and the second part deals statistically with the modelling and optimization of these results. Design of experiments (DOE) is provided according to the full factorial design method. Three parameters with three levels lead to performing 27 experimental runs. Finally, the ...
This investigation presents a computer simulation of gas-steam turbine combined cycle used in hot... more This investigation presents a computer simulation of gas-steam turbine combined cycle used in hot dry weather countries. Water is injected into compressor inlet air to alleviate the inlet air temperature and in turn improve the gas turbine output power and efficiency. The gas turbine simulation model is used following [1] and a standard Rankine steam cycle is employed in cascade with the gas turbine cycle. The turbine exhaust gases, instead of disposing to the ambient, are used in three heat exchangers arranged in series to provide all the required heat for steam cycle. The heat exchangers are simulated by the effectiveness-NTU method to obtain the off-design performance. The steam properties and the psychometric air properties are evaluated during the simulation by a linked computer code developed by the author. The results show that, the energy recovery in steam turbine produce power as much as one half of gas turbine output power. A combined efficiency in the range of 45% is reac...
The heat transfer, friction factor, and collector efficiency are estimated experimentally for mul... more The heat transfer, friction factor, and collector efficiency are estimated experimentally for multi-walled carbon nanotubes+Fe3O4 hybrid nanofluid flows in a solar flat plate collector under thermosyphon circulation. The combined technique of in-situ growth and chemical coprecipitation was utilized to synthesize the multi-walled carbon nanotubes+Fe3O4 hybrid nanoparticles. The experiments were carried out at volume flow rates from 0.1 to 0.75 L/min and various concentrations from 0.05% to 0.3%. The viscosity and thermal conductivity of the hybrid nanofluids were experimentally measured at different temperatures and concentrations. Due to the improved thermophysical properties of the hybrid nanofluids, the collector achieved better thermal efficiency. Results show that the maximum thermal conductivity and viscosity enhancements are 28.46% and 50.4% at 0.3% volume concentration and 60 °C compared to water data. The Nusselt number, heat transfer coefficient, and friction factor are aug...
This paper investigates the vibration control, stability, and energy transfer of the offshore win... more This paper investigates the vibration control, stability, and energy transfer of the offshore wind turbine tower system with control force and nonlinearity terms. A nonlinear proportional derivative (NPD) controller was connected to the system to reduce a high oscillation amplitude and to transfer the energy in the wind turbine system. Furthermore, the averaging method and Poincaré maps were used with respect to the controlled system to study the stability and bifurcation analysis in the worst resonance cases. The curves of force response and frequency response were plotted before and after the control unit was added to the wind turbine system. In addition, we discuss the performances of the control parameters on the vibration magnitudes. Numerical simulations were carried out with Maple and Matlab algorithms to confirm the analytical results. The results show the effectiveness of the NPD controller in suppressing the nonlinear oscillations of the wind turbine system.
A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is... more A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is given using BACKONE equation of state. The fluids are alkanes, fluorinated alkanes, ethers and fluorinated ethers. The ORC cycles operate between 100 and 30 1C typical for geothermal power plants at pressures mostly limited to 20 bar, but in some cases supercritical pressures are also considered. Thermal efficiencies Z th are presented for cycles of different types. In case of subcritical pressure processes one has to distinguish (1) whether the shape of the saturated vapour line in the T,s-diagram is bell-shaped or overhanging, and (2) whether the vapour entering the turbine is saturated or superheated. Moreover, in case that the vapour leaving the turbine is superheated, an internal heat exchanger (IHE) may be used. The highest Z th-values are obtained for the high boiling substances with overhanging saturated vapour line in subcritical processes with an IHE, e.g., for n-butane Z th ¼ 0.130. On the other hand, a pinch analysis for the heat transfer from the heat carrier with maximum temperature of 120 1C to the working fluid shows that the largest amount of heat can be transferred to a supercritical fluid and the least to a high-boiling subcritical fluid.
A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is... more A thermodynamic screening of 31 pure component working fluids for organic Rankine cycles (ORC) is given using BACKONE equation of state. The fluids are alkanes, fluorinated alkanes, ethers and fluorinated ethers. The ORC cycles operate between 100 and 30 1C typical for geothermal power plants at pressures mostly limited to 20 bar, but in some cases supercritical pressures are also considered. Thermal efficiencies Z th are presented for cycles of different types. In case of subcritical pressure processes one has to distinguish (1) whether the shape of the saturated vapour line in the T,s-diagram is bell-shaped or overhanging, and (2) whether the vapour entering the turbine is saturated or superheated. Moreover, in case that the vapour leaving the turbine is superheated, an internal heat exchanger (IHE) may be used. The highest Z th-values are obtained for the high boiling substances with overhanging saturated vapour line in subcritical processes with an IHE, e.g., for n-butane Z th ¼ 0.130. On the other hand, a pinch analysis for the heat transfer from the heat carrier with maximum temperature of 120 1C to the working fluid shows that the largest amount of heat can be transferred to a supercritical fluid and the least to a high-boiling subcritical fluid.
In the transcritical carbon dioxide vapor compression cycle heat is rejected in a gas cooler at s... more In the transcritical carbon dioxide vapor compression cycle heat is rejected in a gas cooler at supercritical pressure. At supercritical heat rejection the refrigerant temperature and pressure are independent on each other and one of the most important parameters affect on cycle performance is the pressure on the heat rejection side called the high pressure. A theoretical analysis shows the effect of high pressure, superheat, evaporator and gas cooler exit temperature, and gas cooler exit temperature approach on performance of a transcritical carbon dioxide vapor compression cycle was investigated in this study. The study defines an optimal high pressure which gives a maximum coefficient of performance and suggests that the cycle should operate at or near its optimal high pressure in order to keep its maximum coefficient of performance. The high pressure will also affect the cooling capacity and this effect can be used for boosting capacity at high ambient temperatures. The effect of gas cooler exit temperature and compressor inlet temperature on the optimal high pressure also was investigated. The study shows that the optimum high pressure is mainly a function of gas cooler exit temperature and compressor inlet temperature, while the value of the maximum coefficient of performance is dependent on the gas cooler exit and evaporating temperature. The study also indicates that the superheat of the gas at compressor inlet will have a positive effect on the coefficient of performance when operating with high heat rejection pressure at high ambient temperatures with high evaporating temperatures.
The potential use of many common hydrofluorocarbons and hydrocarbons as well as new hydrofluorool... more The potential use of many common hydrofluorocarbons and hydrocarbons as well as new hydrofluoroolefins, i.e. R1234yf and R1234ze(E) working fluids for a combined organic Rankine cycle and vapor compression refrigeration (ORC-VCR) system activated by low-grade thermal energy is evaluated. The basic ORC operates between 80 and 40°C typical for low-grade thermal energy power plants while the basic VCR cycle operates between 5 and 40°C. The system performance is characterized by the overall system coefficient of performance (COP S) and the total mass flow rate of the working fluid for each kW cooling capacity (_ m total). The effects of different working parameters such as the evaporator, condenser, and boiler temperatures on the system performance are examined. The results illustrate that the maximum COP S values are attained using the highest boiling candidates with overhanging T-s diagram, i.e. R245fa and R600, while R600 has the lowest _ m total under the considered operating conditions. Among the proposed candidates, R600 is the best candidate for the ORC-VCR system from the perspectives of environmental issues and system performance. Nevertheless, its flammability should attract enough attention. The maximum COP S using R600 is found to reach up to 0.718 at a condenser temperature of 30°C and the basic values for the remaining parameters.
To enhance the surface of a material with the desired qualities for diverse applications in servi... more To enhance the surface of a material with the desired qualities for diverse applications in service, a variety of thermal and thermo-chemical surface treatment processes are used. Due to the high-velocity impact inherent in the process, high-velocity oxy-fuel (HVOF) spray is now frequently employed in industrial applications for its ability to generate a high-quality coating with appropriate hardness and low oxide content. In this investigation, a high-velocity oxy-fuel (HVOF) thermal spraying process was utilized to coat WC-10Co powders on a 35CrMo steel substrate. A water jet erosion test was also used to examine the substrate and coated samples’ erosion behavior. The erosion rate was systematically investigated using water jet variables such as the angle of impingement, water jet velocity, standoff distance, and erodent discharge. For the development of multiple regression models, experiments were performed utilizing the central composite rotatable design and the response surface...
The focal point of this study was to use the waste foundry sand (WFS) in the remediation of simul... more The focal point of this study was to use the waste foundry sand (WFS) in the remediation of simulated aqueous solution contaminated with ammonia nitrogen through batch and column tests. Recycling this waste is a real application for sustainable principles because it will reduce disposal costs and the required area in the sanitary landfill. Based on the kinetic sorption measurements for ammonia nitrogen onto WFS, the predominant mechanism was the chemisorption because the measurements were well fitted with the pseudo-second-order model. In comparison with the Freundlich model, the sorption isotherm data were well formulated by models of Langmuir and Sips with a maximum adsorption capacity of 1.152 mg/g. The breakthrough curves for a duration of 80 h certified that the two weight ratios (10:90 and 20:80) of WFS:sand were suitable for maintaining the reactivity and conductivity of permeable reactive barrier (PRB) for pollutant under consideration. The results proved that the increasing of WFS and bed depth increased the breakthrough and saturation times with the sorption capacity of the barrier. Also, the appearance of these curves was directly proportional to the inlet concentration of pollutants and the flow rate of contaminated water. Statistical measures specifically Nash-Sutcliffe efficiency and coefficient of determination were proved that the breakthrough curves were well described by Thomas, Belter, and Yan models.
The evaluation of groundwater quality in the Dammam formation, Faddak farm, Karbala Governorate, ... more The evaluation of groundwater quality in the Dammam formation, Faddak farm, Karbala Governorate, Iraq proved that the sulfate (SO42−) concentrations have high values; so, this water is not suitable for livestock, poultry and irrigation purposes. For reclamation of this water, manufacturing of new sorbent for permeable reactive barrier was required through precipitation of Mg and Fe hydroxides nanoparticles on the activated carbon (AC) surface with best Mg/Fe molar ratio of 7.5/2.5. Mixture of 50% coated AC and 50% scrap iron was applied to eliminate SO42− from contaminated water with efficiency of 59% and maximum capacity of adsorption equals to 9.5 mg/g for a time period of 1 h, sorbent dosage 40 g/L, and initial pH = 5 at 50 mg/L initial SO42− concentration and 200 rpm shaking speed. Characterization analyses certified that the plantation of Mg and Fe nanoparticles onto AC was achieved. Continuous tests showed that the longevity of composite sorbent is increased with thicker bed a...
Lightweight composite materials have recently been recognized as appropriate materials have been ... more Lightweight composite materials have recently been recognized as appropriate materials have been adopted in many industrial applications because of their versatility. The present research recognizes the inclusion of ceramics such as Gr and B4C in manufacturing AMMCs through stir casting. Prepared composites were tested for hardness and wear behaviour. The tests’ findings revealed that the reinforced matrix was harder (60%) than the un-reinforced alloy because of the increased ceramic phase. The rising content of B4C and Gr particles led to continuous improvements in wear resistance. The microstructure and worn surface were observed through SEM (Scanning electron microscope) and revealed the formation of mechanically mixed layers of both B4C and Gr, which served as the effective insulation surface and protected the test sample surface from the steel disc. With the rise in the content of B4C and Gr, the weight loss declined, and significant wear resistance was achieved at 15 wt.% B4C ...
In this article, the performance and working fluid selection for an organic Rankine cycle-vapor c... more In this article, the performance and working fluid selection for an organic Rankine cycle-vapor compression refrigeration (ORC–VCR) integrated system activated by renewable energy is investigated. The performance of the system is described by the system coefficient of performance (COPS), and the refrigerant mass flow rate per kilowatt refrigeration capacity (m˙total). Twenty-three pure substances are proposed as working fluids for the integrated system. The basic integrated system performance is assessed and compared using the proposed working fluids. The basic VCR cycle works between 35 and 0 °C, while the basic ORC works between 35 and 100 °C. The impacts of different operating parameters such as the evaporator, the boiler, and the condenser temperatures on the ORC–VCR system performance are also examined. The results show that the cyclopentane accomplished the highest system performance under all investigated operating conditions. Accordingly, among the examined 23 working fluids...
Purpose The aim of this paper is to evaluate the effect of surface treatment on slurry erosion be... more Purpose The aim of this paper is to evaluate the effect of surface treatment on slurry erosion behavior of AISI 5,117 steel using artificial neural network (ANN) technique. Design/methodology/approach The slurry erosion wear behavior of electroless nickel-phosphorus (Ni-P) coated, carburized and untreated AISI 5,117 alloy steel was investigated experimentally and theoretically using ANN technique based on error back propagation learning algorithm. Findings From the obtained results, it can be concluded that the proposed AAN model can be successfully used for evaluating slurry erosion behavior of the Ni-P coated, carburized and untreated AISI 5,117 steel for wide range of operating conditions and Ni-P coating and carburizing improve the slurry erosion resistance of AISI 5,117 steel; however, the coating is more efficient. Originality/value Slurry erosion is a serious problem for the performance, reliability and service life of engineering components used in many industrial applicatio...
The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat u... more The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat using 18 organic working fluids is presented. Several parameters, such as the net power output, exergy efficiency, expander size parameter (SP), and heat exchanger requirement of evaporator and the condenser, were used to evaluate the performance of this recovery cycle and screen the working fluids. The results reveal that in most cases, raising the expander inlet temperature is helpful to improve the net power output and the exergy efficiency. However, the effect of the expander inlet pressure on those parameters is related to the expander inlet temperature and working fluid used. Either lower expander inlet temperature and pressure, or higher expander inlet temperature and pressure, generally makes the net power output more. Lower expander inlet temperature results in larger total heat transfer requirement and expander size. According to the screening criteria of both the higher output and the lower investment, the following working fluids for the supercritical ORC system are recommended: R152a and R143a.
Abstract The utilization of electronic expansion valves (EEVs) in refrigeration and air condition... more Abstract The utilization of electronic expansion valves (EEVs) in refrigeration and air conditioning systems is increased for energy saving and comfort environmental. However, experimental data and refrigerant mass flow models through EEVs are very limited in open literature. In this study, a new technique using artificial neural network (ANN) is applied to depict the mass flow rates of R22 and its alternatives R407C and R410A flowing through EEVs based on the error back propagation learning algorithm. Two strategies are followed; the first is to construct individual ANN models for each refrigerant, and the second is to construct a generalized ANN model for the three investigated refrigerants. The experimental results from open literature are used to construct the ANN models. The ANN models results showed a good agreement with the corresponding experimental data. For individual models, the relative deviations for R22, R407C, and R410A are within ±0.7%, ±1.1%, and ±0.006%, respectively. While for generalized model, the relative deviations are within ±2.5%. Also the generalized model was tested out of its construction range in a predictive mode and it was found to be a reliable tool to estimate the refrigerants mass flow rates.
The present work is represented by the derivation of mathematical model and solving the model ana... more The present work is represented by the derivation of mathematical model and solving the model analytically using the method of separation of variables to describe the migration of the contaminant metal ions through a column packed with bed of permeable reactive barrier (PRB). The validity of the solution can be evaluated through the simulation of cadmium and chromium ions using scrap iron and/or aluminum by-products in the form of wastes that if not utilized to treat waste by waste can impose further burden over the ecosystem. Breakthrough curves proved that the increase of metal ions velocity will decrease the capturing of the ions; therefore, the distribution coefficient and the retardation factor also decrease. Furthermore, the increase of barrier depth will increase the longevity of PRB because this will delay the migration of contaminant. A mathematical model has acceptable ability in the representation of experimental measurements with Nash-Sutcliff efficiency coefficients greater than 0.98. The longevity of the PRB was estimated for the field scale to be 210 and 250 d to produce contaminant effluent beyond 100 cm barrier matrix within the environmental permissible concentrations. Although groundwater velocity is highly variable, a proposed velocity of 0.25 cm/min which is assumed to be analogous to the groundwater velocity has revealed prolonged longevity of 7.02 y for the capture of chromium.
The effect of viscosity on the wear particles produced by vibratory cavitation erosion tests on A... more The effect of viscosity on the wear particles produced by vibratory cavitation erosion tests on Al-99.92 in distilled water and glycerol-water solutions was analyzed. Scanning electron microscope images of wear particles during incubation period were obtained. The surface topography examination revealed that the erosion particles were formed by fatigue. The particles removed from glycerol-water solutions differ from that formed in distilled water, where fatigue striations formed on the particle surface for glycerol-water solutions and not formed for distilled water. Therefore, the stress produced by cavitation bubbles decreases with increase of viscosity.
Purpose This paper aims to investigate the performance and working fluids screening for an ejecto... more Purpose This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are proposed as refrigerants for the ERC to determine the most appropriate one. Design/methodology/approach The ejector performance is characterized by the ejector area ratio (EAR) and entrainment ratio (ω), while the cycle performance is described by the coefficient of performance (COP). The influences of many working parameters like the evaporator, condenser and generator temperatures on the ejector and cycle performances are investigated for all candidates as well. Findings The results indicate that the best ejector and cycle performances are attained with the highest critical temperature dry refrigerant, i.e. R601 under all studied working conditions. From the perspective of energy efficiency and environmental issues, R601 can be con...
In this study, the performance of an integrated desiccant air conditioning system (IDACS) activat... more In this study, the performance of an integrated desiccant air conditioning system (IDACS) activated by solar energy is evaluated by back propagation artificial neural network (BP-ANN). The IDACS consists of a liquid desiccant dehumidification cycle combined with a vapor compression refrigeration cycle. The integrated system performance is assessed utilizing the system coefficient of performance (COP), outlet dry air temperature (T da-out), and specific moisture removal (SMR). The training of the BP-ANN is accomplished utilizing experimental results previously published. The results of the BP-ANN model revealed the high accuracy in predicting system performance parameters compared with experimental values. The BP-ANN model has shown relative errors in the trained mode for COP, T da-out , and SMR within ±0.005%, ±0.006%, and ±0.05%, respectively. On the other side, the BP-ANN model is inspected in the predictive mode as well. The relative errors of the model for COP, T da-out , and SMR in the predictive mode are within ±0.006%, ±0.006%, and ±0.004%, respectively. The influences of some selected parameters, namely regeneration temperature, desiccant solution temperature in the condenser and evaporator, and strong solution concentration on the system performance are examined and discussed as well.
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Papers by Bahaa Saleh