Dr Muhammad Amjad obtained his PhD from the University of Leeds, UK, in 2018, after his BSc in Industrial and Manufacturing Engineering (2009) and MSc in Manufacturing Engineering (2012) from the University of Engineering and Technology (UET) Lahore, Pakistan. His research interests include nanofluids for direct solar absorption, solar desalination, forward osmosis based desalination, solar refrigeration and solar thermal systems.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This study aims to evaluate performance of 30 models (15 selected from literature and 15 newly de... more This study aims to evaluate performance of 30 models (15 selected from literature and 15 newly developed) to estimate diffuse horizontal irradiance (H d) using high-quality measurements for nine stations having different climatic conditions. The models (divided into three categories) are based on extraterrestrial global horizontal irradiance (H o) and measured global horizontal irradiance (H g) using sunshine duration ratio, clearness-index, temperature, relative humidity, and periodicity factor as input parameters. The performance of models was evaluated using statistical parameters; the performance of H g based models (Category-II and Category-III) is better than H o based models (Category-I). The performance of newly developed models in three categories is better than best models selected from the literature, due to higher number of input parameters and higher powers used. The best models in Category-I, Category-II and Category-III have rMBE (rRMSE) ranges from − 0.3 to 0.6% (14 to 20%), − 0.6 to 0.1% (10 to 17%) and − 0.3 to 0.0% (10 to 17%) respectively. The performance of models varies in different zones, and different stations within same zone, due to variations of climatic conditions. The best models have rMBE within ±1% and rRMSE < 20%, and can be used for initial resource assessment of commercial solar PV projects for potential locations.
A number of thermal management devices are used to actuate concentrated electronic appliances in ... more A number of thermal management devices are used to actuate concentrated electronic appliances in an efficient way. A liquid cooling plate acts as a heat sink enclosed by materialized walls. This work aims to carry out design of liquid cooling plates such that the heat diffused by the electronic equipment is removed while their temperatures levels remain within safe limits. The liquid cooling plates expose "cold surfaces" to electronic appliances. The performance of a cooling plate is estimated depending upon heat carrying capacity, associated heat transfer rates and concentrated thermal regions on the plate surface. For this study, the design of liquid cooling plate was done with SOLIDWORKS. Pure water was used as a working fluid in test channels. A comparative analysis of flow distribution, temperature contours, pressure drop and pumping power for different channel configurations was carried out with ANSYS. It was observed that a channel configuration is of key importance in liquid cooling plates. The findings from this study are beneficial for the optimum design of cooling systems for high heat flux applications, i.e., in electronic devices, computer processors and automotive engines.
The burning of fossil fuels in power sectors for energy generating purposes and in agricultural c... more The burning of fossil fuels in power sectors for energy generating purposes and in agricultural country like Pakistan the residues of crops on large area of land are burnt every year that results in continuous addition of CO 2 in environment. CO 2 capture through solid based adsorbents is one of the best valued, echo friendly and technoeconomic processes. The present research involves the development of activated carbons using five different waste biomass materials through single step chemical activation for effective CO 2 adsorption, study of isosteric heat of adsorption and change in these values with a change in level of CO 2 adsorbed. Chemical activation with single-step method was carried out to prepare the adsorbents. The samples were characterized and compared for the textural properties by recording isotherms of nitrogen adsorption at temperature of 77 K while CO 2 adsorption curves at 273 K then at 298 K. SEM was brought into use to investigate morphological characters, surface morphology of activated carbons that confirms the presence of random micro-pores. Nonlinear density functional theory (NDLFT) strengthen the fact that CO 2 adsorption depends upon the volume of pores. Samples have pore volume ranging from 0.11 cm 3 to 0.44 cm 3 , whereas BET surface area values were observed from 439 m 2 /g up to 979 m 2 /g. Among the prepared activated carbons, the sample with date seeds as base material showed the uppermost uptake of 5.8 mmol/g at 273 K. Linear fitting of the curve between CO 2 adsorbed and pore volume at a temperature of 273 K and 298 K with R 2 values greater than 0.9 demonstrate the strong relation between pore volume, temperature and CO 2 adsorbed. Isosteric heat of adsorption (IHA) values were found to be in the assortment of 44 KJ/mol with minimum value of 14.3 KJ/mol that decreases with increase of CO 2 adsorption. High isosteric heat means strong interaction of CO 2 molecules and prepared adsorbents. Obtained results confer base to use waste biomass materials for development of solid based adsorbents and use of these adsorbents in effective carbon capture applications to reduce the carbon footprints in the environment and avoid the waste burning of biomass residues.
The convective and conductive heat transfer between the solar collector and working fluids make p... more The convective and conductive heat transfer between the solar collector and working fluids make photothermal performance limited, and result in a higher rate of heat loss from the surface of the conventional absorber to the surroundings. Direct absorption solar collectors (DASC) are a favorable alternative for their improved photothermal performance. In this study, a simulation based on the performance of a nanostructured solar collector has been carried out using TRNSYS. The connective and conductive heat transfer from direct solar collectors were improved by using nanofluids and three different nanostructured materials, CuO, GO, and ZnO, in this study. The analysis determines the outlet temperature of the working fluids that passed through the direct solar collector. The TRNSYS model consists of a direct solar collector and weather model for Lahore city, the simulations were performed for the whole year for 1,440 h. The stability of these nanostructured materials in the water was investigated by using a UV-Vis spectrophotometer. Various performance parameters of direct solar collectors were determined, such as variation in outlet collector temperature and heat transfer rates. The numerical model is validated with experimental results. A maximum outlet temperature of 63°C was observed for GO-based nanofluids. The simulation results show that for the whole year, nanofluids improved the performance of direct solar collectors. Significant improvements in the heat transfer rate of 23.52, 21.11, and 15.09% were observed for the nanofluids based on nanostructures of CuO, ZnO, and GO respectively, as compared to water. These nanostructured energy materials are beneficial in solar-driven applications like solar desalination, solar water, and space heating.
With advancement of nanoscience, "nanofluids" are becoming quite popular among thermal engineers.... more With advancement of nanoscience, "nanofluids" are becoming quite popular among thermal engineers. High thermal conductivity, relatively less settling speed, and higher surface area of nanoparticles are a few key promoting properties. The last two decades have seen dramatic progress towards using nanoparticles in industrial applications. However, the stability and rheological characteristics of prepared nanofluids have serious effects on their transport characteristics, but unfortunately, this has not found proper attention from researchers. In this study, stability and rheological characteristics of ZnO nanoparticles within deionized water, ethylene glycol, and their blends have been extensively tested. Stability was observed using UV-vis spectroscopy, while the viscosity was measured with the help of a rheometer. The data was collected with 0.011-0.044 wt. % loading of nanoparticles, while experiments were conducted within 15-55 o C temperature range. Better stability was recorded when nanofluids were prepared with pure ethylene glycol. Experiments showed that the viscosity increased with particle loading, whereas the effect of surfactants appeared to be insignificant. Research results were used to assess predictions of different viscosity models. Experimental data was overpredicted by Einstein, Brinkman, and Batchelor's models.
Modern manufacturing industries prefer laser drilling processes owing to the adequate controlled ... more Modern manufacturing industries prefer laser drilling processes owing to the adequate controlled drilling in comparison with existing alternatives. The presented experimental study mainly accounts defocusing impact along with other technical parameters and optimization of Nd:YAG millisecond pulsed laser drilling; and finally their influence on the entrance and exit holes profile. The key technical parameters such as pulse frequency, pulse width and assisting gas pressure with respect to different defocused focal plane are explored experimentally for the percussion laser drilling of high grade steel 18CrNi8. Experiment results revealed that increase in defocusing distance has caused an increment in hole entrance diameter; however, with different defocusing distance, the entrance diameter increasing rate keep changing. Different trends of increasing and decreasing diameter at entrance and exit are recorded and investigated with respect to work-piece defocusing positions. The defocusing variation of laser beam has been investigated with the hole profile, changing from straight hole to tapered blind hole. Which leads to conclusive and optimized results for obtaining optimal hole profile (at entrance and exit). The optimum parametric combinations for attaining lower heat treatment effects are also discussed for superior hole quality.
Biomass from the crop residue has huge potential for renewable power generation, but it is still ... more Biomass from the crop residue has huge potential for renewable power generation, but it is still not utilized to its full potential. This study presents a comprehensive methodology to evaluate and forecast the current and future availability of selective crop residue to generate renewable energy. A forecast model incorporating historical trends in the crop yield has been developed in MATLAB and implemented for crop residue based biomass resource assessment of five primary crops (wheat straw, rice husk, rice straw, cotton straw, corn stover, and bagasse) in order to estimate the energy generation potential for Pakistan from 2018 till 2035. It was found that about 40 million tonnes of crop residue was available in Pakistan for power generation in the year 2018 considering a residue removal (availability) factor of 50%. This translates to an estimated potential of about 11,000 MW of electricity generation capacity using crop residue derived biomass for 2018. This capacity is predicted to gradually increase up to 16,000 MW by the year 2035 based on the trends in the growth of crop production since 2001. The suitability of a potential region for the installation of 100 MW biomass-fired power plants was also assessed by calculating crop residue density and an equivalent collection radius (R e) of 50 km (km). Punjab province of Pakistan, being an agricultural province, with relatively better road infrastructure can sustain crop residue based power plants of up to 7000 MW cumulative capacity at various locations. The challenges, such as economic, logistics, regulatory and political barriers, in generating renewable energy from biomass along with their potential solutions were also discussed. The study also provides a baseline for future research to evaluate and forecast the growth in bio-power generation potential of any biomass resource in a region based on crop yield and area of the region.
• HTF flow rate has more significant influence on PCM-water tank than on conventional water tank.... more • HTF flow rate has more significant influence on PCM-water tank than on conventional water tank. • Feasibility analysis to discuss employing PCM-water tank in CHP plants for heat supply. • More thermal energy can be released by PCM-water tank but with lower energy efficiency. • PCM-water tank shows obvious advantages when operating at small flow rate.
This work experimentally investigated photothermal conversion behavior of Gold/water and MWCNT/wa... more This work experimentally investigated photothermal conversion behavior of Gold/water and MWCNT/water nanofluids at different volumetric concentrations (0.0001-0.004% and 0.0001-0.03%, respectively) in a direct absorption solar collector (DASC). The experiments were conducted for~10 h outdoor on each test day, without interruptions. The results show that the tested nanofluids have excellent photothermal conversion capability even under very low concentrations. Specific absorption rate (SAR) presented an exponential decay with increasing volumetric concentration of nanoparticles in the sample while both the total energy stored by the fluid sample during the heating period and the stored energy ratio (SER) increased with the increase in nanoparticles concentration. The results indicate the existence of an "optimal" volumetric concentration, above which further nanoparticle addition becomes indifferent or infeasible. This optimal nanoparticle volumetric concentration was found to be 0.002% for the gold nanofluid and 0.001% for the MWCNT samples for the setup used in this work. Theoretical-Experimental Yousefi et al. [11] Al 2 O 3 Water Application: FPSC Experimental Yousefi et al. [12] MWCNT Water Application: FPSC Experimental Yousefi et al. [13] MWCNT Water Application: FPSC Experimental Khullar et al. [14] Al Therminol VP1 Application: PSC Experimental He et al. [15] Cu Water Photothermal properties Experimental Jamal-Abad et al. [16] Cu Water Application: FPSC Experimental Liu et al. [17] CuO Water Application: evacuated tubular solar air collector with CPC Experimental He et al. [18] Cu Water Application: FPSC Experimental Hordy et al. [19] MWCNT Water, ethylene glycol, Therminol VP1, propylene glycol Application: solar collector Experimental Bandarra Filho et al. [20] Ag Water Photothermal conversion efficiency Experimental Karami et al. [21] CNT Water Photothermal properties Experimental Zhang et al. [22] Au Water Photothermal conversion efficiency Experimental Gupta et al. [23] AL 2 O 3 Water Application: DASC Experimental Karami et al. [24] CuO Water-ethylene glycol Application: DASC Experimental Sabiha et al. [25] SWCNT Water Application: ETSC Experimental Salavati Meibodi et al. [26] SiO 2 Water-ethylene glycol Application: FPSC Experimental Tong et al. [27] MWCNT Water Application: U tube solar collector Experimental Delfani et al. [28] MWCNT Water-ethylene glycol Application: DASC Experimental Vakili et al. [29] Graphene Water Application: DASC Experimental Verma et al. [30] MgO Water Application: FPSC Experimental Vincely e Natarajan [31] Graphene oxide Water Application: FPSC Experimental Jeon et al. [32] Au Water Application: FPSC Theoretical-Experimental Chen et al. [33] Au Water Application: DASC Experimental Amjad et al. [34] Au Water Photothermal conversion efficiency Experimental Fu et al. [35] Graphene oxide-Au Water Application: Solar vapor generation Experimental Rose et al. [36] Graphene oxide Ethylene Glycol Optical properties Theoretical-Experimental Iranmanesh et al. [37] Graphene Water Application: ETSC Experimental Chen et al. [38] Au Water Photothermal conversion efficiency Theoretical-Experimental Wang et al. [39] Chinese ink Cu, CuO, Carbon Black Water Photothermal conversion efficiency Experimental Mahbubul et al. [40] SWCNT Water Application: ETSC Experimental Duan et al. [41] Au, SiO 2 cores coated with Au nanoshell Water Photothermal conversion efficiency Theoretical Liu et al. [42] Reduced Graphene Oxide Water Application: Solar vapor generation Experimental Amjad et al. [43]
• Osmotic pressure and temperature aspects are combined for the first time in novel FO solar desa... more • Osmotic pressure and temperature aspects are combined for the first time in novel FO solar desalination.
Nanoparticle based direct solar absorption is a promising technology for future solar thermal sys... more Nanoparticle based direct solar absorption is a promising technology for future solar thermal systems. Having so many individual studies on different nanomaterials for solar energy harness, a comprehensive comparison of photothermal conversion characteristics of various nanofluids at the same experimental conditions is much needed. The photothermal conversion performance of six commonly used nanomaterials in direct absorption solar collectors (DASC) was investigated under a focused simulated solar flux. The contribution of sensible heating and latent heat of vaporization of the nanofluids was revealed in context of their photothermal performance. The results show that all the nanofluids have higher solar energy absorption than the base fluid and silver nanofluid turned out to be the best amongst all due its strong plasmonic resonance nature. A 99.7% enhancement in the photothermal conversion efficiency of silver was achieved within the experimental domain. A simulation model was proposed to state the temperature difference between the surface of the nanoparticle and the surrounding fluid under lower solar flux.
Solar multiple (SM) and thermal storage capacity are two key design parameters for revealing the ... more Solar multiple (SM) and thermal storage capacity are two key design parameters for revealing the performance of direct steam generation (DSG) solar power tower plant. In the case of settled land area, SM and thermal storage capacity can be optimized to obtain the minimum levelized cost of electricity (LCOE) by adjusting the power generation output. Taking the dual-receiver DSG solar power tower plant with a given size of solar field equivalent electricity of 100 MW e in Sevilla as a reference case, the minimum LCOE is 21.77 ¢/kWh e with an SM of 1.7 and a thermal storage capacity of 3 h. Besides Sevilla, two other sites are also introduced to discuss the influence of annual DNI. When compared with the case of Sevilla, the minimum LCOE and optimal SM of the San Jose site change just slightly, while the minimum LCOE of the Bishop site decreases by 32.8% and the optimal SM is reduced to 1.3. The influence of the size of solar field equivalent electricity is studied as well. The minimum LCOE decreases with the size of solar field, while the optimal SM and thermal storage capacity still remain unchanged. In addition, the sensitivity of different investment in subsystem is investigated. In terms of optimal SM and thermal storage capacity, they can decrease with the cost of thermal storage system but increase with the cost of power generation unit.
• Novel experiment was performed for nanofluids at a focused solar flux of 280 Suns. • Strong sur... more • Novel experiment was performed for nanofluids at a focused solar flux of 280 Suns. • Strong surface evaporation was enabled while the bulk fluid was still subcooled. • A new integration method was used to calculate photothermal conversion efficiency. • Gold nanofluid (0.04 w%) increased photothermal conversion efficiency by 95%. • No nanoparticle was entrained with steam even under vigorous boiling.
Seeding nanoparticles in molten salts has been shown recently as a promising way to improve their... more Seeding nanoparticles in molten salts has been shown recently as a promising way to improve their thermo-physical properties. The prospect of such technology is of interest to both academic and industrial sectors in order to enhance the specific heat capacity of molten salt. The latter is used in concentrated solar power plants as both heat transfer fluid and sensible storage. This work explores the feasibility of producing and dispersing nanoparticles with a novel one pot synthesis method. Using such a method, CuO nanoparticles were produced in situ via the decomposition of copper sulphate pentahydrate in a KNO 3-NaNO 3 binary salt. Analyses of the results suggested preferential disposition of atoms around produced nanoparticles in the molten salt. Thermal characterization of the produced nano-salt suspension indicated the dependence of the specific heat enhancement on particle morphology and distribution within the salts.
The off-design performance of a dual heat source power unit (solar + coal) is studied. A whole-sy... more The off-design performance of a dual heat source power unit (solar + coal) is studied. A whole-system model is established and two integration schemes are studied. Coal consumption can be reduced by >9 Â 10 4 ton/yr for a 660 MW power generation unit. Annual solar efficiency can vary from 17.7 to 20.4% depending on the integration scheme. Increasing heat storage volume decreases discharging efficiency.
This work investigated experimentally the photothermal conversion efficiency (PTE) of gold nanofl... more This work investigated experimentally the photothermal conversion efficiency (PTE) of gold nanofluids in a cylindrical tube under natural solar irradiation conditions, which was also compared with a developed 3-D numerical model. The PTE of gold nanofluids was found to be much higher than that of pure water, and increased non-linearly with the nanoparticle concentration, reaching 76.0% at a concentration of 5.8 ppm. Significant non-uniform temperature distribution was identified both experimentally and numerically, and a large uncertainty can be produced in the PTE calculation by using only one-point temperature measurement. A mathematical model was also established to calculate the solar absorption efficiency without knowing the temperature field within the nanofluids, which can be used to predict the theoretical PTE for nanofluids based on their optical properties only.
Nanoparticle morphology is expected to play a significant role in the stability, aggregation beha... more Nanoparticle morphology is expected to play a significant role in the stability, aggregation behavior, and ultimate fate of engineered nanomaterials in natural aquatic environments. The aggregation kinetics of ellipsoidal and spherical titanium dioxide (TiO 2) nanoparticles (NPs) under different surfactant loadings, pH values, and ionic strengths were investigated in this study. The stability results revealed that alteration of surface charge was the stability determining factor. Among five different surfactants investigated, sodium citrate and Suwannee river fulvic acid (SRFA) were the most effective stabilizers. It was observed that both types of NPs were more stable in monovalent salts (NaCl and NaNO 3) as compared with divalent salts (Ca(NO 3) 2 and CaCl 2). The aggregation of spherical TiO 2 NPs demonstrated a strong dependency on the ionic strength regardless of the presence of mono or divalent salts; while the ellipsoids exhibited a lower dependency on the ionic strength but was more stable. This work acts as a benchmark study toward understanding the ultimate fate of stabilized NPs in natural environments that are rich in Ca(CO 3) 2 , NaNO 3 , NaCl, and CaCl 2 along with natural organic matters.
Deep-hole drilling is a relatively complex drilling production process due to the high-hole diame... more Deep-hole drilling is a relatively complex drilling production process due to the high-hole diameter to length ratio which makes the tool shaft prone to vibration and results typically in low-quality holes from geometry and surface finish viewpoints. This study is aimed at investigating deep-hole drilling process for AISI D2 material taking into account different process input parameters. The hole quality is studied and improved using a response surfacebased design of an experiment technique which resulted in a better hole quality.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This study aims to evaluate performance of 30 models (15 selected from literature and 15 newly de... more This study aims to evaluate performance of 30 models (15 selected from literature and 15 newly developed) to estimate diffuse horizontal irradiance (H d) using high-quality measurements for nine stations having different climatic conditions. The models (divided into three categories) are based on extraterrestrial global horizontal irradiance (H o) and measured global horizontal irradiance (H g) using sunshine duration ratio, clearness-index, temperature, relative humidity, and periodicity factor as input parameters. The performance of models was evaluated using statistical parameters; the performance of H g based models (Category-II and Category-III) is better than H o based models (Category-I). The performance of newly developed models in three categories is better than best models selected from the literature, due to higher number of input parameters and higher powers used. The best models in Category-I, Category-II and Category-III have rMBE (rRMSE) ranges from − 0.3 to 0.6% (14 to 20%), − 0.6 to 0.1% (10 to 17%) and − 0.3 to 0.0% (10 to 17%) respectively. The performance of models varies in different zones, and different stations within same zone, due to variations of climatic conditions. The best models have rMBE within ±1% and rRMSE < 20%, and can be used for initial resource assessment of commercial solar PV projects for potential locations.
A number of thermal management devices are used to actuate concentrated electronic appliances in ... more A number of thermal management devices are used to actuate concentrated electronic appliances in an efficient way. A liquid cooling plate acts as a heat sink enclosed by materialized walls. This work aims to carry out design of liquid cooling plates such that the heat diffused by the electronic equipment is removed while their temperatures levels remain within safe limits. The liquid cooling plates expose "cold surfaces" to electronic appliances. The performance of a cooling plate is estimated depending upon heat carrying capacity, associated heat transfer rates and concentrated thermal regions on the plate surface. For this study, the design of liquid cooling plate was done with SOLIDWORKS. Pure water was used as a working fluid in test channels. A comparative analysis of flow distribution, temperature contours, pressure drop and pumping power for different channel configurations was carried out with ANSYS. It was observed that a channel configuration is of key importance in liquid cooling plates. The findings from this study are beneficial for the optimum design of cooling systems for high heat flux applications, i.e., in electronic devices, computer processors and automotive engines.
The burning of fossil fuels in power sectors for energy generating purposes and in agricultural c... more The burning of fossil fuels in power sectors for energy generating purposes and in agricultural country like Pakistan the residues of crops on large area of land are burnt every year that results in continuous addition of CO 2 in environment. CO 2 capture through solid based adsorbents is one of the best valued, echo friendly and technoeconomic processes. The present research involves the development of activated carbons using five different waste biomass materials through single step chemical activation for effective CO 2 adsorption, study of isosteric heat of adsorption and change in these values with a change in level of CO 2 adsorbed. Chemical activation with single-step method was carried out to prepare the adsorbents. The samples were characterized and compared for the textural properties by recording isotherms of nitrogen adsorption at temperature of 77 K while CO 2 adsorption curves at 273 K then at 298 K. SEM was brought into use to investigate morphological characters, surface morphology of activated carbons that confirms the presence of random micro-pores. Nonlinear density functional theory (NDLFT) strengthen the fact that CO 2 adsorption depends upon the volume of pores. Samples have pore volume ranging from 0.11 cm 3 to 0.44 cm 3 , whereas BET surface area values were observed from 439 m 2 /g up to 979 m 2 /g. Among the prepared activated carbons, the sample with date seeds as base material showed the uppermost uptake of 5.8 mmol/g at 273 K. Linear fitting of the curve between CO 2 adsorbed and pore volume at a temperature of 273 K and 298 K with R 2 values greater than 0.9 demonstrate the strong relation between pore volume, temperature and CO 2 adsorbed. Isosteric heat of adsorption (IHA) values were found to be in the assortment of 44 KJ/mol with minimum value of 14.3 KJ/mol that decreases with increase of CO 2 adsorption. High isosteric heat means strong interaction of CO 2 molecules and prepared adsorbents. Obtained results confer base to use waste biomass materials for development of solid based adsorbents and use of these adsorbents in effective carbon capture applications to reduce the carbon footprints in the environment and avoid the waste burning of biomass residues.
The convective and conductive heat transfer between the solar collector and working fluids make p... more The convective and conductive heat transfer between the solar collector and working fluids make photothermal performance limited, and result in a higher rate of heat loss from the surface of the conventional absorber to the surroundings. Direct absorption solar collectors (DASC) are a favorable alternative for their improved photothermal performance. In this study, a simulation based on the performance of a nanostructured solar collector has been carried out using TRNSYS. The connective and conductive heat transfer from direct solar collectors were improved by using nanofluids and three different nanostructured materials, CuO, GO, and ZnO, in this study. The analysis determines the outlet temperature of the working fluids that passed through the direct solar collector. The TRNSYS model consists of a direct solar collector and weather model for Lahore city, the simulations were performed for the whole year for 1,440 h. The stability of these nanostructured materials in the water was investigated by using a UV-Vis spectrophotometer. Various performance parameters of direct solar collectors were determined, such as variation in outlet collector temperature and heat transfer rates. The numerical model is validated with experimental results. A maximum outlet temperature of 63°C was observed for GO-based nanofluids. The simulation results show that for the whole year, nanofluids improved the performance of direct solar collectors. Significant improvements in the heat transfer rate of 23.52, 21.11, and 15.09% were observed for the nanofluids based on nanostructures of CuO, ZnO, and GO respectively, as compared to water. These nanostructured energy materials are beneficial in solar-driven applications like solar desalination, solar water, and space heating.
With advancement of nanoscience, "nanofluids" are becoming quite popular among thermal engineers.... more With advancement of nanoscience, "nanofluids" are becoming quite popular among thermal engineers. High thermal conductivity, relatively less settling speed, and higher surface area of nanoparticles are a few key promoting properties. The last two decades have seen dramatic progress towards using nanoparticles in industrial applications. However, the stability and rheological characteristics of prepared nanofluids have serious effects on their transport characteristics, but unfortunately, this has not found proper attention from researchers. In this study, stability and rheological characteristics of ZnO nanoparticles within deionized water, ethylene glycol, and their blends have been extensively tested. Stability was observed using UV-vis spectroscopy, while the viscosity was measured with the help of a rheometer. The data was collected with 0.011-0.044 wt. % loading of nanoparticles, while experiments were conducted within 15-55 o C temperature range. Better stability was recorded when nanofluids were prepared with pure ethylene glycol. Experiments showed that the viscosity increased with particle loading, whereas the effect of surfactants appeared to be insignificant. Research results were used to assess predictions of different viscosity models. Experimental data was overpredicted by Einstein, Brinkman, and Batchelor's models.
Modern manufacturing industries prefer laser drilling processes owing to the adequate controlled ... more Modern manufacturing industries prefer laser drilling processes owing to the adequate controlled drilling in comparison with existing alternatives. The presented experimental study mainly accounts defocusing impact along with other technical parameters and optimization of Nd:YAG millisecond pulsed laser drilling; and finally their influence on the entrance and exit holes profile. The key technical parameters such as pulse frequency, pulse width and assisting gas pressure with respect to different defocused focal plane are explored experimentally for the percussion laser drilling of high grade steel 18CrNi8. Experiment results revealed that increase in defocusing distance has caused an increment in hole entrance diameter; however, with different defocusing distance, the entrance diameter increasing rate keep changing. Different trends of increasing and decreasing diameter at entrance and exit are recorded and investigated with respect to work-piece defocusing positions. The defocusing variation of laser beam has been investigated with the hole profile, changing from straight hole to tapered blind hole. Which leads to conclusive and optimized results for obtaining optimal hole profile (at entrance and exit). The optimum parametric combinations for attaining lower heat treatment effects are also discussed for superior hole quality.
Biomass from the crop residue has huge potential for renewable power generation, but it is still ... more Biomass from the crop residue has huge potential for renewable power generation, but it is still not utilized to its full potential. This study presents a comprehensive methodology to evaluate and forecast the current and future availability of selective crop residue to generate renewable energy. A forecast model incorporating historical trends in the crop yield has been developed in MATLAB and implemented for crop residue based biomass resource assessment of five primary crops (wheat straw, rice husk, rice straw, cotton straw, corn stover, and bagasse) in order to estimate the energy generation potential for Pakistan from 2018 till 2035. It was found that about 40 million tonnes of crop residue was available in Pakistan for power generation in the year 2018 considering a residue removal (availability) factor of 50%. This translates to an estimated potential of about 11,000 MW of electricity generation capacity using crop residue derived biomass for 2018. This capacity is predicted to gradually increase up to 16,000 MW by the year 2035 based on the trends in the growth of crop production since 2001. The suitability of a potential region for the installation of 100 MW biomass-fired power plants was also assessed by calculating crop residue density and an equivalent collection radius (R e) of 50 km (km). Punjab province of Pakistan, being an agricultural province, with relatively better road infrastructure can sustain crop residue based power plants of up to 7000 MW cumulative capacity at various locations. The challenges, such as economic, logistics, regulatory and political barriers, in generating renewable energy from biomass along with their potential solutions were also discussed. The study also provides a baseline for future research to evaluate and forecast the growth in bio-power generation potential of any biomass resource in a region based on crop yield and area of the region.
• HTF flow rate has more significant influence on PCM-water tank than on conventional water tank.... more • HTF flow rate has more significant influence on PCM-water tank than on conventional water tank. • Feasibility analysis to discuss employing PCM-water tank in CHP plants for heat supply. • More thermal energy can be released by PCM-water tank but with lower energy efficiency. • PCM-water tank shows obvious advantages when operating at small flow rate.
This work experimentally investigated photothermal conversion behavior of Gold/water and MWCNT/wa... more This work experimentally investigated photothermal conversion behavior of Gold/water and MWCNT/water nanofluids at different volumetric concentrations (0.0001-0.004% and 0.0001-0.03%, respectively) in a direct absorption solar collector (DASC). The experiments were conducted for~10 h outdoor on each test day, without interruptions. The results show that the tested nanofluids have excellent photothermal conversion capability even under very low concentrations. Specific absorption rate (SAR) presented an exponential decay with increasing volumetric concentration of nanoparticles in the sample while both the total energy stored by the fluid sample during the heating period and the stored energy ratio (SER) increased with the increase in nanoparticles concentration. The results indicate the existence of an "optimal" volumetric concentration, above which further nanoparticle addition becomes indifferent or infeasible. This optimal nanoparticle volumetric concentration was found to be 0.002% for the gold nanofluid and 0.001% for the MWCNT samples for the setup used in this work. Theoretical-Experimental Yousefi et al. [11] Al 2 O 3 Water Application: FPSC Experimental Yousefi et al. [12] MWCNT Water Application: FPSC Experimental Yousefi et al. [13] MWCNT Water Application: FPSC Experimental Khullar et al. [14] Al Therminol VP1 Application: PSC Experimental He et al. [15] Cu Water Photothermal properties Experimental Jamal-Abad et al. [16] Cu Water Application: FPSC Experimental Liu et al. [17] CuO Water Application: evacuated tubular solar air collector with CPC Experimental He et al. [18] Cu Water Application: FPSC Experimental Hordy et al. [19] MWCNT Water, ethylene glycol, Therminol VP1, propylene glycol Application: solar collector Experimental Bandarra Filho et al. [20] Ag Water Photothermal conversion efficiency Experimental Karami et al. [21] CNT Water Photothermal properties Experimental Zhang et al. [22] Au Water Photothermal conversion efficiency Experimental Gupta et al. [23] AL 2 O 3 Water Application: DASC Experimental Karami et al. [24] CuO Water-ethylene glycol Application: DASC Experimental Sabiha et al. [25] SWCNT Water Application: ETSC Experimental Salavati Meibodi et al. [26] SiO 2 Water-ethylene glycol Application: FPSC Experimental Tong et al. [27] MWCNT Water Application: U tube solar collector Experimental Delfani et al. [28] MWCNT Water-ethylene glycol Application: DASC Experimental Vakili et al. [29] Graphene Water Application: DASC Experimental Verma et al. [30] MgO Water Application: FPSC Experimental Vincely e Natarajan [31] Graphene oxide Water Application: FPSC Experimental Jeon et al. [32] Au Water Application: FPSC Theoretical-Experimental Chen et al. [33] Au Water Application: DASC Experimental Amjad et al. [34] Au Water Photothermal conversion efficiency Experimental Fu et al. [35] Graphene oxide-Au Water Application: Solar vapor generation Experimental Rose et al. [36] Graphene oxide Ethylene Glycol Optical properties Theoretical-Experimental Iranmanesh et al. [37] Graphene Water Application: ETSC Experimental Chen et al. [38] Au Water Photothermal conversion efficiency Theoretical-Experimental Wang et al. [39] Chinese ink Cu, CuO, Carbon Black Water Photothermal conversion efficiency Experimental Mahbubul et al. [40] SWCNT Water Application: ETSC Experimental Duan et al. [41] Au, SiO 2 cores coated with Au nanoshell Water Photothermal conversion efficiency Theoretical Liu et al. [42] Reduced Graphene Oxide Water Application: Solar vapor generation Experimental Amjad et al. [43]
• Osmotic pressure and temperature aspects are combined for the first time in novel FO solar desa... more • Osmotic pressure and temperature aspects are combined for the first time in novel FO solar desalination.
Nanoparticle based direct solar absorption is a promising technology for future solar thermal sys... more Nanoparticle based direct solar absorption is a promising technology for future solar thermal systems. Having so many individual studies on different nanomaterials for solar energy harness, a comprehensive comparison of photothermal conversion characteristics of various nanofluids at the same experimental conditions is much needed. The photothermal conversion performance of six commonly used nanomaterials in direct absorption solar collectors (DASC) was investigated under a focused simulated solar flux. The contribution of sensible heating and latent heat of vaporization of the nanofluids was revealed in context of their photothermal performance. The results show that all the nanofluids have higher solar energy absorption than the base fluid and silver nanofluid turned out to be the best amongst all due its strong plasmonic resonance nature. A 99.7% enhancement in the photothermal conversion efficiency of silver was achieved within the experimental domain. A simulation model was proposed to state the temperature difference between the surface of the nanoparticle and the surrounding fluid under lower solar flux.
Solar multiple (SM) and thermal storage capacity are two key design parameters for revealing the ... more Solar multiple (SM) and thermal storage capacity are two key design parameters for revealing the performance of direct steam generation (DSG) solar power tower plant. In the case of settled land area, SM and thermal storage capacity can be optimized to obtain the minimum levelized cost of electricity (LCOE) by adjusting the power generation output. Taking the dual-receiver DSG solar power tower plant with a given size of solar field equivalent electricity of 100 MW e in Sevilla as a reference case, the minimum LCOE is 21.77 ¢/kWh e with an SM of 1.7 and a thermal storage capacity of 3 h. Besides Sevilla, two other sites are also introduced to discuss the influence of annual DNI. When compared with the case of Sevilla, the minimum LCOE and optimal SM of the San Jose site change just slightly, while the minimum LCOE of the Bishop site decreases by 32.8% and the optimal SM is reduced to 1.3. The influence of the size of solar field equivalent electricity is studied as well. The minimum LCOE decreases with the size of solar field, while the optimal SM and thermal storage capacity still remain unchanged. In addition, the sensitivity of different investment in subsystem is investigated. In terms of optimal SM and thermal storage capacity, they can decrease with the cost of thermal storage system but increase with the cost of power generation unit.
• Novel experiment was performed for nanofluids at a focused solar flux of 280 Suns. • Strong sur... more • Novel experiment was performed for nanofluids at a focused solar flux of 280 Suns. • Strong surface evaporation was enabled while the bulk fluid was still subcooled. • A new integration method was used to calculate photothermal conversion efficiency. • Gold nanofluid (0.04 w%) increased photothermal conversion efficiency by 95%. • No nanoparticle was entrained with steam even under vigorous boiling.
Seeding nanoparticles in molten salts has been shown recently as a promising way to improve their... more Seeding nanoparticles in molten salts has been shown recently as a promising way to improve their thermo-physical properties. The prospect of such technology is of interest to both academic and industrial sectors in order to enhance the specific heat capacity of molten salt. The latter is used in concentrated solar power plants as both heat transfer fluid and sensible storage. This work explores the feasibility of producing and dispersing nanoparticles with a novel one pot synthesis method. Using such a method, CuO nanoparticles were produced in situ via the decomposition of copper sulphate pentahydrate in a KNO 3-NaNO 3 binary salt. Analyses of the results suggested preferential disposition of atoms around produced nanoparticles in the molten salt. Thermal characterization of the produced nano-salt suspension indicated the dependence of the specific heat enhancement on particle morphology and distribution within the salts.
The off-design performance of a dual heat source power unit (solar + coal) is studied. A whole-sy... more The off-design performance of a dual heat source power unit (solar + coal) is studied. A whole-system model is established and two integration schemes are studied. Coal consumption can be reduced by >9 Â 10 4 ton/yr for a 660 MW power generation unit. Annual solar efficiency can vary from 17.7 to 20.4% depending on the integration scheme. Increasing heat storage volume decreases discharging efficiency.
This work investigated experimentally the photothermal conversion efficiency (PTE) of gold nanofl... more This work investigated experimentally the photothermal conversion efficiency (PTE) of gold nanofluids in a cylindrical tube under natural solar irradiation conditions, which was also compared with a developed 3-D numerical model. The PTE of gold nanofluids was found to be much higher than that of pure water, and increased non-linearly with the nanoparticle concentration, reaching 76.0% at a concentration of 5.8 ppm. Significant non-uniform temperature distribution was identified both experimentally and numerically, and a large uncertainty can be produced in the PTE calculation by using only one-point temperature measurement. A mathematical model was also established to calculate the solar absorption efficiency without knowing the temperature field within the nanofluids, which can be used to predict the theoretical PTE for nanofluids based on their optical properties only.
Nanoparticle morphology is expected to play a significant role in the stability, aggregation beha... more Nanoparticle morphology is expected to play a significant role in the stability, aggregation behavior, and ultimate fate of engineered nanomaterials in natural aquatic environments. The aggregation kinetics of ellipsoidal and spherical titanium dioxide (TiO 2) nanoparticles (NPs) under different surfactant loadings, pH values, and ionic strengths were investigated in this study. The stability results revealed that alteration of surface charge was the stability determining factor. Among five different surfactants investigated, sodium citrate and Suwannee river fulvic acid (SRFA) were the most effective stabilizers. It was observed that both types of NPs were more stable in monovalent salts (NaCl and NaNO 3) as compared with divalent salts (Ca(NO 3) 2 and CaCl 2). The aggregation of spherical TiO 2 NPs demonstrated a strong dependency on the ionic strength regardless of the presence of mono or divalent salts; while the ellipsoids exhibited a lower dependency on the ionic strength but was more stable. This work acts as a benchmark study toward understanding the ultimate fate of stabilized NPs in natural environments that are rich in Ca(CO 3) 2 , NaNO 3 , NaCl, and CaCl 2 along with natural organic matters.
Deep-hole drilling is a relatively complex drilling production process due to the high-hole diame... more Deep-hole drilling is a relatively complex drilling production process due to the high-hole diameter to length ratio which makes the tool shaft prone to vibration and results typically in low-quality holes from geometry and surface finish viewpoints. This study is aimed at investigating deep-hole drilling process for AISI D2 material taking into account different process input parameters. The hole quality is studied and improved using a response surfacebased design of an experiment technique which resulted in a better hole quality.
In this study, waste cooking oil (WCO) was used as a feedstock for biodiesel production, where th... more In this study, waste cooking oil (WCO) was used as a feedstock for biodiesel production, where the pretreatment of WCO was performed using mineral acids to reduce the acid value. The response surface methodology (RSM) was used to create an interaction for different operating parameters that affect biodiesel yield. The optimised biodiesel yield was 93% at a reaction temperature of 57.50 °C, catalyst concentration 0.25 w/w, methanol to oil ratio 8.50:1, reaction stirring speed 600 rpm, and a reaction time of 3 h. Physicochemical properties, including lower heating value, density, viscosity, cloud point, and flash point of biodiesel blends, were determined using American Society for Testing and Materials (ASTM) standards. Biodiesel blends B10, B20, B30, B40, and B50 were tested on a compression ignition engine. Engine performance parameters, including brake torque (BT), brake power (BP), brake thermal efficiency (BTE), and brake specific fuel consumption (BSFC) were determined using bi...
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