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In the present research, dual-nozzle swirl generator was installed at the blocked end of the straight tube to inject flow tangential to the wall of the pipe with various injection inclinations compared to the longitudinal axis. This causes a swirl flow inside the pipe. Altering some decisive variables, including injection angle, side of nozzle cross-section, pipe diameter, and flow rate, caused to attain various cases with unique hydraulic-geometrical characteristics. Classes ‘A…-D50-N…-M…’ and ‘A…-D20-N…-M…’ bear the main characteristics of the cases embodied in their sub-classes. Entropy generation (St), Nu*, NE, Heat Transfer Improvement (HTI) index and ${\eta}_{w-s}$ were used as effective tools for the basement of the system based on the irreversibility concept. The results showed that all of the cases of class ‘A…-D50-N…-M…’ cause lower frictional-contributed and higher thermal-contributed entropy generation compared to the class ‘A…-D20-N…-M…’. The highest values of the HTI index are 1.5 and 1.763 obtained by ‘A30-D20-N5-M0.4’ and ‘A90-D20-N6.25-M0.1’, respectively.

In this numerical study, an attempt has been made to improve the thermal performance of the flat-plate solar collector (FPSC) by inducing the swirl flow inside the tube by the considered nozzles. To this end, the effect of the number of circumferential nozzles and their inclination angles was taken into the account. The considered number of nozzles was "single", ''dual'', ''triple'', and ''quad''. For each of the said cases, the inclination angle of nozzles was taken 30°, 45°, 60°, and 90° (A30, A45, A60, A90). Moreover, the mass flow rate of single-nozzle pipe was considered 0.2 kg/s, 1 kg/s, and 2 kg/s. To analyze all of the cases under identical conditions, the said mass flow rates were distributed equally among all of the nozzles (for ''dual'', ''triple'', and ''quad''). All of the characteristics were defined in a form of "A…-D…-N…-M…'' where ''A…'', "D…", "N…", and "M…" stand for angle of injection, diameter of pipe, nozzle cross-section edge, and mass flow rate, respectively. Numerical simulation (3-dimensional) of the system was performed by Finite Volume Method (FVM). The turbulence nature of flow was simulated by the k-omega SST (shear stress transport) turbulent model. Results showed that the "single-nozzle'' swirl generator had the highest thermal performance factor (TPF) so that for all cases its values were greater than unit. Mass flow rate growth increases Nu, heat extraction rate, and kinetic energy rate (KER) while drops friction factor and outlet temperature. Increment of injection angle increases outlet temperature and friction factor and reduces KER. The maximum and minimum values of TPF are 4.19 and 0.44 which belong to "single; A30-D50-N12.5-M0.2" and "quad; A90-D50-N12.5-M0.5", respectively.

Hydrogen is a clean energy and has many applications in petroleum refining, glass purification, pharmaceuticals, semiconductors, aerospace applications and cooling generators. Therefore, it is very important to store it in various ways. One of the new and cheap methods to store hydrogen is storing in the brine groundwater. In this method, the hydrogen gas is injected into the brine, in which storing capacity has a direct relationship with the pressure, temperature and salt concentration of the saltwater. In the present study, an artificial neural network (ANN) was used to estimate and optimize the hydrogen solubility (HS) in the saltwater with conventional best algorithms such as the feedback propagation, genetic algorithm (GA) and radial basis function. The optimization is implemented based on available experimental data bank based on the variation of the pressure, working temperature and salt concentration. The results and assessments of different optimization ANN algorithm show that the GA has the most usable and accurate estimation and prediction for HS in the saltwater. Also, the amounts of the relevancy coefficient (${R}_c$) that correspond to the sensitivity of HS on the input parameters demonstrate that the salt concentration and pressure have the minimum and maximum ${R}_c$, respectively. That is, the least and most effect on the output values.

The numerical model of the pipes of a flat plate solar collector (FPSC) with several nozzles has been investigated in the present study. Indeed, the effect of the number of nozzles of the swirl generator on the entropic characteristics has been evaluated. The nozzles were applied for improving the performance of FPSC. For evaluating the proposed system based on the entropy concept, the effect of injection angle and mass flow rate has been considered. The selected injection angles were 30°, 45°, 60°, and 90°. Also, the total mass flow rates entered from all of the nozzles were 0.2 kg/s, 1 kg/s, and 2 kg/s. The effect of said variables on frictional and thermal entropy generations was analyzed; then, the overall energetic-entropic performance of the system was predicted using several dimensionless parameters including NE, NS, Nu ∗ , and heat transfer improvement (HTI). Moreover, Witte-Shamsundar efficiency ( η W − S ) was applied to pinpoint the efficiency of the system. The highest value of HTI and η W − S was 1.7 and 0.9 that achieved by “single-nozzle; A90-D50-N12.5-M0.2” and “quad-nozzle; A30-D50-N12.5-M2,” respectively.

In the present numerical study the ring-shape depressions were created on the wall of spiral pipe that can be employed as a heat exchanger in the solar ponds. Unlike available literature that focused on the optimization of solar ponds through its nature recognition, present study tried to propose an efficient passive method for maximizing heat extraction. This is a simple and cost-efficient technique for enhancing the overall performance of salinity-gradient solar ponds through augmentation of turbulence inside the modified piping system and yielding higher heat extraction accordingly. Indeed, the introduced practical technique not only prevents the increment of size and volume of the piping system but also makes it needless to use additional supplementary equipment like turbulator or even air injectors. Moreover, this is a good way to prevent fouling inside piping system which bears huge costs. 3D numerical simulation was done based on Finite Volume Method (FVM) and turbulent flow simulated by RNG k-epsilon model. Due to the steady-state nature of this problem pressure–velocity coupling algorithm was adopted. The effect of several decisive parameters including Dean, Pr (fluid type and inlet temperature), groove distance, and groove depth on Nu, f, j-factor, and TPF was studied. Interestingly, it was turned out that the values of thermal performance factor (TPF) for all cases were above 1 which shows the justifiability of made modifications. For all flow rates water has the highest Nu and the lowest friction factor compared to Theminol-55 and Ethylene-glycol. Groove pitch of 20 mm makes the highest values of Nu so that 168, 195, and 216 were the maximum obtained Nu for cases with groove depth of 0.7 mm, 1 mm, and 1.3 mm, respectively (working fluid was water and Dean = 1615). Said statement is true for f where its maximum values were 0.1, 0.14, and 0.2, respectively, for cases with groove depth of 0.7 mm, 1 mm, and 1.3 mm (working fluid was water and Dean = 269). The highest Nu of Therminol-55, Ethylene-glycol, and water were 100, 114, and 216, respectively for groove pitch of 20 mm.

Development of numerical code for evaluating the solidification of water has been scrutinized in this work. The container has two circular and sinusoidal cold walls at bottom and top surfaces. Galerkin-based code has been employed to model this phenomenon. To elevate the conductivity of phase change material (PCM), alumina particles with nanosized were utilized with incorporating different shapes. The conductivity of nanoencapsulated phase change material (NEPCM) is a function of concentration and shapes of nanoparticles. The freezing process is mainly dominated by conduction and selecting curved shaped and adding nanoparticles can affect this mechanism. Verification test reveals the good accommodation and applying adaptive grids leads to higher accuracy. As shape coefficient increases, the period of process declines around 10.65% owing to stronger conduction. Also, mixing water with alumina nanopowders with blade shape causes decrement in needed time around 32.51%. Besides, outputs reveal that utilizing blade shape of powders has more effect on required time than that of cylindrical shape.

This work contains simulation of solidification within a container with new structure. The assumption of neglecting velocity term for solidification formulation leads to the reduction of number equation for such 2D modeling to two equations and FEM was selected for this purpose. This model involves adaptive grid that incorporates the implicit approach for transient terms. The water that incorporates various sizes of nanopowders leads to creating new material and for predicting the properties, the formulation based on homogeneous mixing has been utilized. Adding nanoparticles leads to a reduction of the required time around 26.52% and 12.25% when [Formula: see text] and 50 nm while its effect for [Formula: see text] nm is 41.19%. As the size of the particles augments upto 40 nanometer, the required time declines around 19.96% while augmenting upto 50 nanometer leads to augment of time of around 49.2%.

Since the Gas Diffusion Layer (GDL) clearance and the residence time of produced water in gas channels remarkably affect the proper operation of proton exchange membrane (PEM) Fuel Cells, the water management in this part plays a key role. To this end, the present study aims to introduce novel and optimized gas channels through geometrical modifications that act efficiently in terms of GDL clearance and liquid residence time. For this purpose, the VOF (Volume of Fluid) model was employed to numerically simulate two-phase flow by means of a finite volume method. Several decisive parameters including superficial gas velocity, channel surface wettability, and channel cross-section geometry were considered to find their effects on the liquid removal behavior. The liquid removal performance was analyzed by two-phase pressure drop, area coverage ratio (ACR), and liquid removal time. Results have been compared with previous works done on the conventional rectangular channels. Interestingly, it was found out that for the analyzed segment of the gas flow channels, the channel with triangle cross-section has superior performance in reducing ACR by 64% for inlet superficial air velocity of 0.5 m s and 8–24.45% reduction for higher velocities (1, 1.5 and 2.5 m s ). Also, the transition from slug flow to film flow also stable two-phase pressure drop were only seen in this type of channel. The ranking of channels based on their residence time merit is as: hexagon > pentagon > rectangular > triangle. Increment of the contact angle of hydrophilic walls causes fluctuations in the two-phase pressure drop and decreases liquid water residence time. For triangle channel, surface with a contact angle of ∼ 120 ° and for the hexagon and pentagon channels 85–120° is suggested for the best fuel cell performance.

In the current work, we investigated the concentration of Ni and Pb in different organs of Phragmites australis to evaluate its potential application as a phytoremediator to remove these two metals from contaminated water and sediment in Lake Burullus (a Ramsar site in Egypt). Above- and below-ground biomass of P. australis, water and sediment were sampled monthly for 1 year at six sites of Lake Burullus (three sites represent each of the northern and southern parts of the lake) using six randomly distributed quadrats (each of 0.5 × 0.5 m) at each sampling site. Significant variation was detected for Ni and Pb concentrations in the sediments and waters between the northern and southern sites of the lake. The biomass of P. australis in the southern sites was greater than that in the northern sites; in addition, the above-ground biomass was higher than the below-ground biomass. The above-ground organs accumulated higher concentrations of Ni and Pb than the below-ground organs. The Ni and Pb standing stocks data indicated that the organs of P. australis extracted higher amounts of Ni and Pb per its area from the southern rather than the northern sites. In the current study, the Ni and Pb above-ground standing stocks increased from the early growing season (February) and reached its peak during August and then decreased. The highest monthly Ni and Pb standing stock (18.2 and 18.4 g m− 2, respectively) was recorded in the above-ground organs of plants in the southern sites in August. The bioaccumulation factor of Ni was 157.6 and 153.4 in the northern and southern sites, respectively, whereas that of Pb was 175.3 and 158.3. The translocation factor of Ni and Pb from the below- to above-ground organs was generally > 1. Thus, this reed species is a potential candidate for Ni and Pb phytoextraction. Based on our results, P. australis could be used for the extraction of Ni and Pb to reduce the pollution in Lake Burullus, if the above-ground biomass is harvested at its maximum value in August, as was the case regarding the maximum standing stock of Ni and Pb.

A three-dimensional Darcy Forchheimer mixed convective flow of a couple stress hybrid nanofluid flow through a vertical plate by means of the double diffusion Cattaneo–Christov model is presented in this study. The influence of high-order velocity slip flow, as well as a passive and active control, is also considered. The motive of the research is to develop a computational model, using cobalt ferrite (CoFe2O4) and copper (Cu) nanoparticles (NPs) in the carrier fluid water, to magnify the energy and mass communication rate and boost the efficiency and performance of thermal energy conduction for a variety of commercial and biological purposes. The proposed model becomes more significant, with an additional effect of non-Fick's mass flux and Fourier's heat model to report the energy and mass passage rate. The results are obtained through the computational strategy parametric continuation method. The figures are plotted to reveal the physical sketch of the obtained solution, while the statistical assessment has been evaluated through tables. It has been observed that the dispersion of Cu and CoFe2O4 NPs to the base fluid significantly enhances the velocity and thermal conductivity of water, which is the most remarkable property of these NPs from the industrial point of view.

Precise knowledge of the soil organic carbon (SOC) stocks under various land uses is needed to meet the Kyoto Protocol and for the sustainability of natural resources. The purpose of the present st...

The current study aims at forming new prediction models to be employed in the approximating the possible uptake of a range of 10 heavy metals (HMs) (Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn) by Hordeum vulgare tissues including roots, shoots and grains following its growth in soil amended with sewage sludge (SS) using conditions employed in greenhouses. The present study determined an insignificant difference between the actual and predicted quantities of the HMs in the three tissues using t values. The majority of the predicted quantities of the HMs were acceptable with the exception of Cd in the shoots, Cu in grains and Pb in roots. Consequently, it is possible to use these models in assessing the cultivation of barley plants in soil amended with SS in a safe way, while simultaneously monitoring any potential risks to the health of humans.

The present study was conducted to investigate the potential of the emergent macrophytes Phragmites australis to remediate nutrients and restore an eutrophic wetland (Lake Burullus, Egypt). The plant was sampled monthly for one year from 6 sites distributed equally along the northern and southern parts of this lake. Monthly significant variation in all investigated sediment and water nutrients for the northern and southern sites was recorded. The biomass of P. australis in the southern sites was greater than that of the northern sites; in addition, the above-ground biomass was greater than the below-ground biomass. The above-ground biomass increased from February until it reached its maximum during August and then decreased again. Likewise, the highest nutrient concentrations in the different tissues were recorded at the beginning of the growing season during winter and early spring and then gradually decreased with increasing plant biomass. Moreover, the nutrient content (g/m2) increased from the early growing season (February) and reached its peak during April–August and then decreased. Based on our results, P. australis could be used for the extraction of nutrients to reduce the eutrophication in Lake Burullus, if the above-ground biomass is harvested at its maximum value in August, as was the case regarding the maximum content of most nutrients.

At present time, rock mechanics is considered an important science during the phase of design and implementation of any project in Civil and Mining Engineering (highway, bridges, tunnels, dams, and so on.) especially when we speak about interaction between the project and the rock masses by choosing the appropriate foundation. In addition, rock masses slopes stability is a real problem and represents an important concern in Assyr Province in order to avoid rock fall process on the main roads and buildings. Therefore, due to the characteristics of this province, where various mountainous terrain in which various metamorphic and igneous rocks can be investigated. For this reason, it is necessary to explore, inspect, investigate and understand the natural stresses within these rock masses taking into a consideration the third dimension. Moreover, we assumed that the rock masses considered as isotropic medium in the first time. In the second phase, it considered as anisotropic medium introducing the thickness of each layer in the model. In another hand, based on literature review, several methods of measuring natural stresses in rock masses have been used, including the over-coring method with CSIRO cell involved in this research to estimate the natural stresses using 3D Finite Element modeling. In this sense, the state of stresses within the rock masses depends on the characteristics of CSIRO cell and the dimension of the over-coring hole. Furthermore, in order to achieve the 3D modeling the characteristics of the rock masses mentioned before introduced in the model using "Surfrac" program written in Pascal and FORTRAN, coupled with "Abaqus" software to simulate the stresses matrix in the model. As a result, the main findings of this research is summarized in three points: the first, dealing with the CSIRO cell itself where the direction of the gauge is important during the measurement of stresses, in fact, the perpendicular gauges work better than the parallel to the hole axis. The second one, it is evident from the model that the direction of hole must be perpendicular to the dip direction of the rock layers allows to give better results compared to others. The third one, the selection of the measurement site requires involving the regional stresses of the study area according to geological investigation. Finally, it is interesting to carry out geophysical exploration in the study area to understand the local tectonic movement of rock masses. Moreover, detailed map can be highlighted the main fractures and faults network and overlap it with the most important projects deployed in Assyr province for maintenance and monitoring.

Background The problem of multicollinearity in multiple linear regression models arises when the predictor variables are correlated among each other. The variance of the ordinary least squared estimator become unstable in such situation. In order to mitigate the problem of multicollinearity, Liu regression is widely used as a biased method of estimation with shrinkage parameter ‘d’. The optimal value of shrinkage parameter plays a vital role in bias-variance trade-off. Limitation Several estimators are available in literature for the estimation of shrinkage parameter. But the existing estimators do not perform well in terms of smaller mean squared error when the problem of multicollinearity is high or severe. Methodology In this paper, some new estimators for the shrinkage parameter are proposed. The proposed estimators are the class of estimators that are based on quantile of the regression coefficients. The performance of the new estimators is compared with the existing estimators through Monte Carlo simulation. Mean squared error and mean absolute error is considered as evaluation criteria of the estimators. Tobacco dataset is used as an application to illustrate the benefits of the new estimators and support the simulation results. Findings The new estimators outperform the existing estimators in most of the considered scenarios including high and severe cases of multicollinearity. 95% mean prediction interval of all the estimators is also computed for the Tobacco data. The new estimators give the best mean prediction interval among all other estimators. The implications of the findings We recommend the use of new estimators to practitioners when the problem of high to severe multicollinearity exists among the predictor variables.

In the present study, the natural convection flow of water with Nano-encapsulated phase change material (NPCM) was simulated inside an insulated chamber, which a pair of pipes were considered as a heater and cooler sources with the boundary condition of uniform temperature. The NPCM's core was made of n-nonadecane with melting temperature of 30.44°C. This core has ability to change the liquid-solid phase to transfer heat between the heater and the cooler sources. Current simulation was steady state and was solved by SIMPLE algorithm based on FVM to investigate the effects of Rayleigh number, volume fraction and location of phase change zone on the convective heat transfer coefficient. Observations showed that, phase change of NPCM occurs at low Rayleigh numbers but had no effect on the convective heat transfer coefficient, but it was directly related to the thermal conductivity of mixture. Moreover, adding volume fraction of NPCM 0.02 into water increased the convective heat transfer coefficient by 10.43%, 19.1% and 18.3% compared to pure water for Rayleigh numbers 102,104,and106, respectively.

The current study aims at forming new prediction models to be employed in the approximating the possible uptake of a range of 10 heavy metals (HMs) (Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn) by

Single helical tube has been widely investigated in both smooth wall and corrugated wall structures. However, for the first time, this paper proposes and works on a helical tube-in-tube heat exchanger in which both inner tube and outer tube are corrugated (see graphical abstract for possible interesting configurations). The idea of the fabrication process of such heat exchanger will be the first challenge; and that is why the first part of this research explains what steps are required to fabricate the mentioned heat exchanger with affordable and available industrial techniques. When both inner tube and outer tube are corrugated, the relative position of the corrugations on both tubes provides different configurations (see case “c” and “d” in the graphical abstract) with completely different behaviors. In the second step, the numerical simulation of the mentioned heat exchanger is validated with the experimental results. At the third part of the paper, a comprehensive simulation is performed to analyze the mentioned heat exchanger from thermal, frictional and exergetic viewpoints. The results show that the corrugating of the outer tube in addition to the inner tube significantly boosts the thermal capacity of the heat exchanger without any further weight, area or size of the heat exchanger (case “d” provides 125% higher Nu number compared to the case “a”). Besides, the mentioned relative position of the corrugations plays a significant role so that the obtained Nu number of case “d” is 35% higher than that of case “c” (the difference of these cases is only the relative position of the corrugations). The reason of all these phenomenon and other remarkable findings are reported in this paper.

The free convection of Cu-water nanofluid is simulated and investigated inside a square heat exchanger chamber in the presence of MHD magnetic field. The Buongiorno model with the effects of Brownian and thermophoresis motion is considered to nanoparticles distribution inside the chamber. The geometry consists of a square chamber with two cylinders on the right and left sides as heater and cooler in order to create the buoyancy force, respectively. These cylinders represent hot and cold pipes, and the walls of the chamber are heat and mass insulation. the FVM with SIMPLE algorithm are used for velocity and pressure coupling. In current two-phase simulation, the effects of Rayleigh number, Hartmann number, inclination angle of chamber and volume fraction on streamline contours, isothermal lines, Lorentz force lines, nanoparticle distribution and Nusselt number are investigated. By modeling the motion of nanoparticles and evaluating it, a nanoparticle transport zone was observed. The diffusion effects of thermophoresis were significant in this zone. The nanoparticles were thrown from the hot cylinder to the cold cylinder. The application of a magnetic field enlarged the nanoparticle transport zone. However, increasing the Rayleigh number and decreasing the inclination angle of the enclosure caused the nanoparticles to disperse evenly.

Ground source heat pump, due to high coefficient of performance (COP) and use of low-temperature thermal energy source, is one of the best technologies to use renewable energy resources. In this work, at first, a geothermal heat pump for heating with an economizer is simulated, and then the effects of the variations in different parameters such as evaporator pressure, condensation pressure, and intermediate pressure on heat pump and total COP and exergy efficiency are analyzed. Initially, the thermodynamic simulation of the system is performed for different working fluids (R134a, R-12, R152a, R1234yf, and R1234ze(E)) in the EES software programming environment. The COP and exergy efficiency are calculated for different working fluids and obtained optimal values. The best overall coefficient of performance of the system is related to fluid R134a with a value of 3.663 and the best overall exergy efficiency of the system is related to fluid R1234ze(E) with a value of 0.5517. The lowest PCEU value is for fluid R152a with 0.01247$ per kilowatt. It can be concluded that by reducing the evaporator pressure of the cycle, the cost of producing an energy unit will be cheaper and by reducing the middle pressure of the cycle, the cost of producing an energy unit will be more expensive.

Through the present investigation, the thermal and power output of novel-shaped solar panels are evaluated. For the cooling of the mentioned forms, forced air flow was utilized. Three novel shapes, of Pyramid, Hexagonal, and Conical which had the equal lateral surface were considered. For the simulation, an open source CFD software was utilized. The lateral surfaces were put under identical amount of heat flux. Air as the coolant fluid was injected with constant inlet temperature from the trapdoors at the bottom of different shaped structures. Three different values of heat flux and air injection rate were evaluated for each shape. The outcomes presented that the conical shaped solar panel exhibits better thermal performance than other geometries. Furthermore, conical form finds the least temperature that was about 10.5 ?C less than that of the pyramidshaped panel. Furthermore, it was revealed that the corners of pyramid and hexagonal-shaped solar panels have higher temperature. Also, it was found that the efficiency of conical shaped panel was up to 8.4% more than that of pyramid-shaped panel.

In this research, entropic analysis of a double helical tube heat exchanger including circular depressions on both inner tube and outer tube is provided. Experimentally validated 3D numerical simulation is employed to reach the aim of this study. Entropic characteristics of four cases are investigated and reported. In case “a” both inner tube and outer tube are smooth. In case “b”, circular depressions are created on only inner tube while in case “c” both tubes contain circular depression. Case “d” is the same as case “c” while the depression arrangement is different from case “c”. Dimensionless entropy generation and dimensionless Nu number are used to evaluate the proposed designs based on the first and second laws of thermodynamics. Moreover, heat transfer improvement (HTI) factor is adopted to consider the impacts of said two parameters simultaneously. Results demonstrate that, although creating circular depressions on both tubes significantly improves the heat transfer characteristics of the heat exchanger, it increases the entropy generation level of heat exchanger as well. Case “d” in which the location of any circular depression of the outer tube is placed between any two continuous depressions of the inner tube, gives the highest thermal performance and also entropy generation.