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This paper presents new experimental data on water flow on stepped chutes with upward inclined steps. The slopes of the chutes are 30°, 45°, and 60° whereas the upward angles of the inclined steps are 10°, 20°, and 30°, respectively. Classifications of flow patterns by empirical correlations are presented. Based on dimensional analysis, the important parameters are analyzed, and the relevant dimensionless parameters are established. The energy loss and outlet velocity are strongly influenced by the Drop number and the slope of the stepped chutes. As the Drop number increases, the energy loss ratio decreases. At identical Drop numbers the energy loss ratio on the more moderate slope is greater than on the steeper. The adverse slope of the inclined steps increases the energy loss ratio and decreases the outlet velocity by less than 10%. To estimate the kinetic energy ratio, an empirical equation is proposed. [ABSTRACT FROM AUTHOR]

In the present study, new experimental data on the performance of a never before seen two-phase ejector refrigeration cycle (TPERC) is presented. In this cycle, a two-phase ejector is used as an expansion device. The TPERC enables the evaporator to operate as in a liquid-recirculation system. The results are compared with those of the conventional refrigeration cycle (CRC). The effects of external parameters, i.e., heat sink and heat source temperatures on the system performance are discussed. The results show that the coefficient of performance of the TPERC is higher than that of the CRC over the whole range of experimental conditions. This is due to a higher refrigerant-side heat transfer coefficient in the evaporator, resulting from the higher refrigerant mass flow rate passing through the evaporator. However, the increase becomes relatively smaller as the heat sink temperature increases. [Copyright &y& Elsevier]

A fluidized bed dryer (FBD) and a combined microwave/fluidized bed dryer (CMFD) are used to dry the fresh ripe peppercorns. The average moisture content vs. elapsed drying time, and drying rate vs. average moisture content are experimentally investigated. It is found that the microwave field from the CMFD can increase the potential of the conventional fluidized bed drying. The drying rates of both dryers are dependent on the inlet air temperature and velocity. For the CMFD, the effects of the air velocity on the drying rate are found to be opposite to our previous results tested with white pepper seeds i.e., the drying rates of the fresh ripe peppercorns decreased with increasing air velocity. By using a CMFD, the drying time required to reach the desired moisture content can be reduced to 80-90% of the drying time required for a FBD at the same drying air temperature and velocity. The color of the product dried by a CMFD is also attractive: it becomes flaming yellow, instead of black as obtained from a FBD. The physical structure of the peppercorn, before and after the drying process is also investigated by a metallurgical macroscope and an image analyzer. Different from drying by a FBD, the external form and matter of the white pepper seed are still maintained, even after passing through the drying process. [ABSTRACT FROM AUTHOR]

This article provides a literature review on solar-powered Stirling engines and low temperature differential Stirling engines technology. A number of research works on the development of Stirling engines, solar-powered Stirling engines, and low temperature differential Stirling engines is discussed. The aim of this review is to find a feasible solution which may lead to a preliminary conceptual design of a workable solar-powered low temperature differential Stirling engine.Results from the study indicate that Stirling engines working with relatively low temperature air are potentially attractive engines of the future, especially solar-powered low temperature differential Stirling engines with vertical, double-acting, gamma-configuration. [Copyright &y& Elsevier]

Focuses on the assumptions that no metastable flow phenomenon and flow in two-phase region is homogeneous have been used exclusively to study the flow characteristics in capillary tubes used as an expansion and controlling device in refrigerating systems. Experimental results indicating that due to the delay of vapourization, the onset of vapourization may not take place at the end of the sub-cooled liquid region; Why two-phase flow in small diameter tubes may be also not entirely homogeneous; How a mathematical model based on conservations of mass, energy and momentum is presented to simulate the refrigerant flow in adiabatic capillary tubes; How the model is validated by comparing with the experimental data reported in literature; What the agreement between experimental and simulation results indicates.

The two-phase flow patterns of HFC-134a with lubricant oil mixtures inside a smooth horizontal tube were experimentally elucidated. Tests were performed in an inside diameter of 7.8 mm having a lubricating oil concentration of 5%. Tests were made of mass fluxes ranging between 150 and 590 kg/m[sup 2] s. The most obvious difference from oil-free cases reported is the presence of froth flow pattern. Apparently, this flow pattern is related to the increase of surface tension and viscosity. With the presence of lubricant oil, the onset of transition from stratified flow region to annular flow regime shifted to a lower value of superficial gas velocity. In addition, the tearing phenomenon of the refrigerant-oil mixtures may be related to its relevant properties such as wettability and surface tension. [ABSTRACT FROM AUTHOR]

By following the recently published paper in Science titled 'Coercive Citation in Academic Publishing', in this paper, we aim to discuss the demand of some journals that request authors to cite recently published papers in that journal to increase the impact factor of that journal. It will be mentioned that some of these demands are not ethical and consequently will diminish the reputation of the journal. [ABSTRACT FROM AUTHOR]

Temperature stratification between outgoing hot water and incoming cold water is a key factor in diminishing energy loss during the discharging process and maximizing the useful hot water delivered from the tank or enhancing the thermal efficiency of the heating device during the heating process. In this study, the inlet structure and the obstacle plate were designed and modified based on two main factors, the reduction of inlet water velocity and the stipulation of the water recirculation area, to develop temperature stratification through the computational fluid dynamics method. The simulation model's accuracy was validated against the experimental results. The results showed that using the equalizer as an inlet pipe's auxiliary device was the best approach for decreasing the inlet water velocity, which resulted in enhancing temperature stratification. The discharging efficiency improved from 77.3% for the original tank model to 86.1% for the tank with equalizer IV model, which meant an additional 45 L of useful hot water was gained from the good temperature stratification storage tank. The installation of the obstacle plate for controlling the turbulence zone could not improve temperature stratification significantly, which resulted in an increase in discharging efficiency by only 4% more than the original tank model. [ABSTRACT FROM AUTHOR]

We analytically investigated the electroosmotic flow characteristics of complex viscoelastic liquids within a charged hydrophobic microchannel, considering the pH and salt concentration-dependent surface charge effects in our analysis. We examined the variation of the electric-double layer (EDL) potential field, the surface charge-dependent slip (SCDS) length, the flow field, the viscosity ratio, and both normal and shear stresses in relation to the bulk pH, bulk salt concentration, and Deborah number of the solution. Our current findings indicate that, under strong flow resistance due to increased electrical attraction on counter ions, a highly basic solution with a high EDL potential magnitude results in a significant decrease in the slip length. Neglecting the effect of SCDS leads to an overestimation of flow velocity, with this overprediction being more pronounced for highly basic solutions. This overestimation diminishes as bulk salt concentration increases, particularly when compared to strongly acidic solutions. Furthermore, a noticeable increase in average velocity is observed as the Deborah number rises for highly basic solutions compared to highly acidic ones. This is attributed to the substantial reduction in apparent viscosity caused by the shear-thinning nature of the liquid at higher shear rates, supported by a larger zeta potential modulated strong electrical force for basic solutions. Additionally, we found that the intensity of shear and normal stresses tends to increase with bulk pH, primarily due to the rise in electric body force at higher zeta potential. These results can potentially inform the design and development of a compact, nonmoving electroosmotic pump for transporting biological species with varying physiological properties, such as solution pH. This technology could be applied in subsequent processes involving mixing, separation, flow-focusing for cell sorting, and other related applications. [ABSTRACT FROM AUTHOR]

Conical enclosures rely on the conical cavity and can be used as radiation concentrators. Two circular cross-section baffles were used to improve the heat transfer of this geometry. By changing the rigid fins to porous, it could improve the heat transfer. Al2O3/water nanofluid was also employed to enhance the heat transfer performance of the cavity. For this purpose, numerical analysis of three-dimensional natural convection heat transfer was performed in a conical cavity with two types of fins. The best combination of fins arrangement for the next step was selected using the differential evolutionary optimization method (D.E). In this case study, a new combination of laminar and turbulence methods was employed for the first time to increase the accuracy of the natural convection solution. This combination is based on the laminar solution by suppressing the perturbation parameter in the turbulence method which led to more accurate results. The analysis results showed that a conical cavity with optimized fin geometry can lead to a 23% increase in Nu. The best porosity for the inner fin was calculated 40% in the case of constant porosity. Ascending porosity along the fin, whose increase was more intense near the base and slower near the cone's tip, was the best variable porosity for the inner fin. [ABSTRACT FROM AUTHOR]

The present article deals with the computational fluid dynamics (CFD) investigation of flow and heat transfer of a [C2mim][CH3SO3]/Al2O3 ionanofluid in one conventional tube and two different grooved tubes. The flow is considered to be single-phase and laminar (500 < Re < 2000), and the range of nanoparticle concentration is between 0.05 and 2 %. For properties of the ionanofluid, experimental data available in the literature have been used. The results of relative heat transfer coefficient, pumping power, and field synergy are presented for the three different tubes at various Reynolds numbers and ionanofluid concentrations. It is found that the effect of grooves is more pronounced at low concentrations. Moreover, the heat transfer coefficient and pumping power rise by increasing the concentration. Adding the nanoparticles has a greater impact on the heat transfer at lower Reynolds numbers. The pumping power is intensified by the Re increment. More uniform temperature and velocity distributions are achieved because of the more severe flow mixing induced by the grooves. Both the greatest heat transfer coefficient and the highest pumping power occur for the tube having the spirally corrugated grooves. The results show that the heat transfer varies by changing the geometry. At a volume concentration of 0.05 % and Re = 500, the heat transfer coefficient increases by 15.54 % in the tube with the spirally corrugated grooves compared to the conventional tube. [ABSTRACT FROM AUTHOR]

• A novel heat sink for cooling a Photovoltaic panel has been studied. • Combination of CFD, differential evaluation and sensitivity analysis has been employed. • A new concept of engineered porous media was explored. • Thermal radiation has been considered. • An optimum porosity has been obtained for two type of porous heat sink. Temperature is one of the most important factors of solar photovoltaic panel (PV) efficiency. İncreasing the temperature causes serious damage to the solar panel. In this research, the effect of the new model of the porous fin as rows of connected spheres on surface temperature was investigated. For achieving this target, the rigid fins and this model of porous fin were compared. Thermal radiation was also examined to increase accuracy in the calculations. After validation and grid study, two models of heat sink with distinct vertical layers and two horizontal layers of connected spheres have been investigated to cool down the PV panel. After that, the new concept of porous heat sink was optimized based on sensitivity analysis (SA) and Differential Evolution (DE) optimization algorithm. A combination of numerical modeling and D.E optimization can improve the final efficiency and increase heat transfer. In this study, by considering the porosity range between (0–70%), we try to find the optimal value of porosity. The results show that by using the special form of porosity on the back layer of the P.V panel, the heat transfer can be increased up to 15%. It's also indicated that the optimization process can improve the Nu and reduce calculation cost. This optimization algorithm is 34 times much faster than another optimization process in CFD method. [ABSTRACT FROM AUTHOR]

The article reports on sympathy and emotions in professional network for scientists.

We make an effort in this study to experimentally investigate the flow boiling pressure drop characteristics in a multi-microchannel heat sink. For the multi-microchannel heat sink, 27 parallel microfluidic channels are considered. Microchannels are fabricated on the copper block and have a hydraulic diameter of 421 µm and length of 40 mm. We perform experiments considering the refrigerant, considered the working fluid in this study. A high mass flux (G ∼ 400 kg/m2 s–1200 kg/m2 s) for a range of wall heat flux (q′′ ∼ 10 kW/m2–170 kW/m2) and varying degrees of saturation temperature (Tsat ∼ 13 °C, 18 °C, and 23 °C) are considered for the experiments. We demonstrate the correlative effect of the total pressure drop on the two-phase flow pattern in the channel. By depicting the interplay between the total pressure drop (∆p) and the frictional pressure gradient, we show that the frictional pressure gradient increases with the increasing mass flux while it decreases with the increasing degree of saturation temperature. We show the significant impact of the heat flux and saturation temperature on the frictional pressure gradient. In addition, we develop a new correlation for the pressure drop characteristics taking the interference effect of the frictional pressure drop in the multi-microchannel heat sink. The inferences of this experimental study will have far-ranging consequences for the design of heat exchangers, leading to the optimization of microscale thermal management equipment. [ABSTRACT FROM AUTHOR]

• Geometry of double pass SAH with helical flow path is optimized. • CFD, sensitivity analysis and deferential evaluation optimization are employed. • This work is a continuation of the previous research of the authors. • Thermo-hydraulic performance parameter is increased 16.5% due to optimization. Solar air heaters (SAH) have been widely studied due to their extensive applications in solar energy extraction. This research is in line with the previous study of the authors of this article in which the energy efficiency and heat transfer performance of a double pass solar air heater with helical flow path (HFP) were experimentally and numerically explored in a triangular cross-section channel. Here, the effect of different geometric parameters of this SAH on heat transfer performance is numerically investigated. The optimization procedure was also carried out by the differential evolution (DE). The results of this study were developed by referring to the grid independency and validation of the previous work of the authors. Finally, the effects of triangular section angles and dimensions and the location of the entrance section of each channel were investigated and optimized. The results indicated that optimized geometry resulted in a considerably higher thermo-hydraulic performance as compared with reference geometry for all Reynolds numbers which showed a minimum increment of t 16.5% upon optimization. The inactive vortices produced at the edge of entrance flow passage were reduced in each channel due to optimization which also declined the pressure drop. [ABSTRACT FROM AUTHOR]

Numerous researches to prepare and stabilize graphene-based nanofluids have been developed. [ABSTRACT FROM AUTHOR]

Graphene has attracted much attention from the science world because of its mechanical, thermal, and physical properties. Graphene nanofluid is well known for its easy synthesis, longer suspension stability, higher heat conductivity, lower erosion, corrosion, larger surface area/volume ratio, and lower demand for pumping power. This article is an audit of experimental outcome about the preparation and stability of graphene-based nanofluids. Numerous researches to prepare and stabilize graphene-based nanofluids have been developed, and it is indispensable to create a complete list of the approaches. This research work outlines the advancement on preparation and assessment methods and the techniques to enhance the stability of graphene nanofluids and outlook prospects. [ABSTRACT FROM AUTHOR]

The natural heat convection within a square enclosure filled with water–Al2O3 nanofluid has been studied numerically in the presence of a magnetic field. The effect of heat source geometry attached to the bottom wall on the Nusselt number was investigated by changing its nondimensional width and height, and side walls thickness of the enclosure ranging from 0.1 to 0.5, 0.1 to 0.8 and 0.05 to 0.2, respectively. A regression model has been obtained along with conducting a sensitivity analysis seeking an optimal heat transfer. Results, reveal that Nusselt number increases by enlarging the fin, and reaching a peak point before it declines. Thus, interestingly, the ever-increasing heat transfer by means of fin size does not retain and there is an optimal point wherein the maximum heat transfer occurs. Moreover, the thermal performance of the system largely depends on the fin size rather than the relative side walls thickness. However, its effect intensifies as the fin width increases. Results of optimization show that the maximum heat transfer occurs at W = 0.4615 , H = 0.6467 and L b = 0.2 . [ABSTRACT FROM AUTHOR]

At the microfluidic scale, the utilization of helically coiled channels (HCCs), also known as a spiral channel, for two-phase flow offers numerous advantages in various applications. Existing articles mainly focus on the macro-scale transport, examining secondary flows induced in curved channels. The increasing demand, however, for innovative miniature equipment for thermal energy management emphasizes the importance of comprehending gas–liquid micro-scale flow in curved channels. Unfortunately, despite a vast body of literature on this paradigm, there is still a lack of systematic investigations into the underlying facets of two-phase micro-scale transport in HCCs. To address this gap, our study conducted experiments on adiabatic two-phase air–water flow inside an up-flow helical micro-scale tube. The tube had a hydraulic diameter of 0.87 mm, a coil diameter of 50 mm, and a helical pitch of 20 mm. The primary aim was to explore the impact of centrifugal force on flow pattern, void fraction, and frictional pressure drop characteristics. Additionally, we carefully examined the phase separation phenomenon influenced by the secondary flows induced by the curved channel. In particular, we compared the gas-core flow pattern (either throat-annular flow or annular flow), void fraction, and frictional pressure drop obtained from our experiments on the helical tube with corresponding results based on straight micro-scale channel configurations for an Eötvös number of approximately 0.01. In summary, this study delves deep into the crucial aspects of two-phase micro-scale transport in HCCs, contributing to a better understanding of these systems for future advancements in micro-channel applications. [ABSTRACT FROM AUTHOR]

Inelastic non-Newtonian fluids are imbibed in a non-uniform conical-shaped microfluidic channel, discussed quantitatively using a theoretical model. We consider the Ostwald–de Waele power-law model to describe the rheology of the inelastic non-Newtonian fluids. Consistent with the reduced order model, the theoretical framework developed here accounts for the coupled effects of fluid rheology, flow configuration, and surface wettability to describe the transient progression of the filling length in the capillary under varied cases. Considering the simultaneously intervening interactions resulting due to rheological effect, geometrical modulation, and surface wetting condition during the imbibition phenomenon, we demonstrate the temporal advancement of the filling phase fluid length in the non-uniform capillary for a set of involving parameters pertinent to this analysis. Non-uniformity in the capillary cross-section gives rise to an alteration in the viscous force acting at the fluid–fluid–solid interface, which in turn, leads to a control over the temporal progression of fluid length, retaining a balance between the capillary and viscous forces. From the predicted relation between filing length and time of filling, we identify three distinct regimes of filling and establish the befitting scaling laws describing the imbibition phenomenon in the respective regimes. • Imbibition of inelastic non-Newtonian fluids in a conical-shaped microcapillary. • The Ostwald–de Waele power-law model describes the rheology of non-Newtonian fluids. • Temporal advancement of the filling length in the capillary is demonstrated. • Three distinct regimes of filling are identified for the imbibition phenomenon. [ABSTRACT FROM AUTHOR]

With a focus on biochemical applications and utilizing relevant physical properties, the current study numerically analyzes the impact of electroosmotic vortex and fluid rheology on the chemical reaction characteristics of species. This is achieved by installing integrated positively charged patches on the extended region of the microreactor with three inlets for injecting the reactants and generating the electroosmotic vortex. In order to produce species "C" in the extended region of the microreactor, it is presumed that reactant species "A" is injected through the upper and lower inlets and reactant species "B" is injected via the intermediate inlet. To solve the associated transport equations with appropriate boundary conditions, a thorough theoretical framework is developed. The results show that the ability of the reactant species to react is boosted when vortices form in the microreactor, increasing the convective mixing strength for reactant species. Furthermore, the fluid rheology significantly affects the reaction characteristics, which is a noteworthy finding. For fluids exhibiting a higher shear-thinning nature, the average concentration of the produced species follows an increasing–decreasing trend with the Carreau number. Additionally, it becomes apparent that the influence of the Damkohler number on the average generated species concentration is negligible at lower Carreau numbers, but it increases with the Damkohler number at higher Carreau numbers. The study also reveals that both rheological and chemical parameters have a substantial impact on the flow rate of product species. Overall, the findings of this investigation provide valuable insights for the development of technologically advanced electroosmotic microreactor capable of effectively generating the intended product species. [ABSTRACT FROM AUTHOR]

Corrigendum to "Geometry optimization of double pass solar air heater with helical flow path" [Sol. [Extracted from the article]

In this paper, a three-dimensional multiphase model of the polymer exchange membrane (PEM) fuel cell is simulated to study the effect of assembly pressure on the contact resistance between the gas diffusion layer (GDL) and bipolar plate (BP) interface. The results reveal that the increase of assembly pressure is associated with a decrease in the contact resistance between the GDL and BP interface, which results in reaching an ideal fuel cell performance. The performance improves until the assembly pressure of 4.5 MPa and it slightly drops with a clamping pressure of 5.5 MPa in the ohmic loss region of the polarization curve. Additionally, the variation of the electrical field in a cross-section of the channel length shows that the intrusion of GDL into the flow channel increases with increasing assembly pressure; consequently, the maximum electrical current will increase. The cell temperature rises at higher assembly pressure when considering the thermal contact resistance. This increase is higher on the cathode side because of the existence of the reaction heat source. Additionally, it is found that the distribution of electrical potential and oxygen concentration is more uniform at higher clamping pressure. This results in the development of the PEM fuel cell life cycle. • 3D Multiphase modeling of PEM fuel cell considering the thermal and electrical contact resistance. • Improve the overall performance of PEM fuel cell by increasing assembly pressure. • Increasing the temperature of PEM fuel cell by decreasing the electrical and thermal contact resistance. • Obtaining a suitable range of assembly pressure for ideal performance. [ABSTRACT FROM AUTHOR]

This study numerically examines the elliptical winglets (EW) on the overall performance of fin-and-tube heat exchanger. The major geometrical parameters characterizing the EW has been investigated thoroughly, including the winglet location, attack angle and the trailing angle of the elliptical winglets with two different winglet lengths which are 1.0 mm and 1.5 mm. The numerical results indicate that the elliptical winglets with the 30° attack angle, 0 mm horizontal distance, 6 mm vertical distance and 120° trailing angle of both winglet lengths shows the highest performance. The heat transfer coefficients and pressure drops obtained by both winglet sizes are larger than that of the plain fin by about 13% and 35%, respectively. In term of the performance efficiency index, the 1.5 mm winglet length indicates about 1.8–2.9% improvement relative to plain fin geometry and the efficiency index of 1.0 mm winglet length is comparable with that of the plain fin. [ABSTRACT FROM AUTHOR]

This paper presents a new way to hyper-optimise a flat plate solar collector using a combination of regenerated point clouds, constructal theory, and physics-informed machine learning (PIML). The behaviour of the flat plate solar collector is studied as solar radiation and ambient temperature change, using both precise numerical simulation and PIML. The novel hyper-optimisation method integrates these two approaches to improve the performance of the solar collector. In this method, the volume of fluid and solid structure of the flat plate solar collector (FPSC) is transformed into point clouds based on constructal theory. The point clouds are then regenerated into a continuous and uniform 3D geometry using optimised parameters. To put the modified version of the flat plate solar collector (FPSC) into practice, a computational method is used to generate a training data set for machine learning, specifically for neural networks. After thoroughly verifying the computational results, the PIM is trained using the generated training data set. This study marked the first time that a regular computational method is replaced with PIML output to reduce the computational cost of prediction. In the second layer of calculation, a deep neural network is used to make predictions based on the outputs generated by PIML. Seven independent parameters are used to predict heat transfer and efficiency over time, including time, heat flux, mass flow rate, inlet temperature, number of pairs and clusters, and volume fraction of nanofluid, while 16 hidden layers and 63 learnable neurons are engaged in this prediction layer. The geometry matrix is redefined by constructal theory principles in a series of iteration loops to generate the first flat plate solar collector based on constructal theory (CTFPSC). The results indicated that the hyper-optimisation method could reduce calculation costs by 18.31% compared with the regular computational method. In addition, the results reveal that maximum outlet temperatures are possible when Nc > 3 and Np> 5. [ABSTRACT FROM AUTHOR]

The fin and tube heat exchanger with a semi-dimple pair is numerically studied in terms of the air side’s thermal performance. The investigated parameters consist of the diameter, attack angle and the placed location of the semi-dimple. The results show that the 30° attack angle, 5.5 mm vertical distance and 7.5 mm horizontal distance can perform the highest j/f ratio or “goodness parameter” of every semi-dimple’s diameter. Additionally, the thermal performance of the fin with a semi-dimple pair is also compared with that of the fin with existing semi-dimples and the plain fin within the Reynolds number ranging from 813 to 4019. Obviously, the existing semi-dimple exhibits the highest heat transfer coefficient and pressure drop. However, the semi-dimples’ pair demonstrates a goodness factor of 33–37% greater than the existing semi-dimples and 15–20% greater than the plain fin, approximately. [ABSTRACT FROM AUTHOR]

Flow pattern, heat transfer, and pressure drop data for different flow orientations was presented in this study. The data was obtained based on flow boiling experiments with R-134a flow through a 1 mm diameter channel which was aligned in different orientations, i.e. horizontal flow, vertical upward flow, and vertical downward flow. A constant surface heat flux condition was performed under a saturation pressure of 8 bar, a heat flux range of 1–60 kW/m 2 , and a mass flux range of 250–820 kg/m 2 s. The experimental results showed the importance of the change in the flow direction. The shape of the gas slug during horizontal flow did not look the same as in the vertical orientations. Heat transfer coefficient and pressure drop became increased when the refrigerant flowed in the vertical downward direction. The experimental data was also compared with the existing prediction methods. [ABSTRACT FROM AUTHOR]

New experimental data on plate heat exchanger performance including the heat transfer coefficient, pressure drop, and thermal performance factor under different chevron angles, surface roughness, and working conditions are presented. Plate surface roughness ranging between 0.95 μm and 2.75 μm with chevron angles of 30° and 60° are used. The experiments are performed at Reynolds numbers ranging between 1200 and 3500, a hot water temperature of 40 °C, and a cold water temperature of 25 °C. The experimental results show that the heat transfer coefficient and pressure drop increase when the chevron angle is decreased and the surface roughness and Reynolds number are increased. Under the testing conditions, the average thermal performance factors are 1.09 and 1.02 for 30° and 60° chevron angles, respectively. The optimum thermal performance of a plate heat exchanger is obtained at a 30° chevron angle, the highest surface roughness, and the lowest Reynolds number. A correlation of Nusselt number and friction factor for different surface roughness and chevron angles are also proposed for practical applications. [ABSTRACT FROM AUTHOR]

In this paper, a solar air heater (SAH) with phase change material (PCM)-based energy storage is investigated. Paraffin was placed underneath the absorber plate as the PCM. A transient two-dimensional laminar model was used in the Ansys Fluent 17 software to study the effects of different parameters on the performance of the SAH, such as the air mass flow rate, the amount of paraffin, and the thermal conductivity of the paraffin. The performance of the SAH was optimized by considering two objectives simultaneously: thermal energy efficiency and maximum nocturnal temperature difference between the inlet and the outlet of the SAH. To validate the numerical model, a SAH with a 2-cm paraffin layer and the same dimensions as the numerical model was built and tested. The results of the simulation showed good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This study examined the pool boiling heat transfer of distilled water on a copper heating surface with passive rotating blades installed above the heating surface. The rotating blades were made from copper material, with a diameter of 30 mm, a core of 5 mm, a length of 50 mm, and a blade angle of 90°. The number of blades in this experiment varied between 2, 3, and 4. The study examined the effects of a varying number of blades and the distance between the heating surface and rotating blades (L SB ) on the pool boiling heat transfer coefficient. The experimental results show that, when compared under the same conditions, the rotor with four blades yielded a higher heat transfer coefficient than those with two and three blades. This is because the added blades increased the area that received strike force from the bubbles. As a result, the rotating blades created more disturbance of the working fluid over the heating surface. Furthermore, when compared with the same number of blades, the L SB of 5 mm yielded a higher heat transfer coefficient than the L SB of 15 or 25 mm. This is because the increased L SB provided less chance for the bubbles to strike the rotating blades. Hence, the rotating blades did not create a disturbance of the working fluid over the heating surface. [ABSTRACT FROM AUTHOR]

DNA (deoxyribonucleic acid) possesses the ability to alter its conformation in response to stresses. In the case that DNA is mistakenly structured or packed, it can lead to diseases or deformities. Additionally, stretching and compressing of DNA can be useful for some applications. Thus the investigation of the DNA elasticity and stability is necessary. We propose to study the mechanics of a DNA molecule under mechanical stress within the framework of Kirchhoff's rod model. The problem is solved by perturbation method to find equilibrium configurations of DNA at different modes that can be excited. The results show that DNA overwinds under tension of 31 pN, and it begins to unwind beyond 31 pN which is in good agreement with the previous literature. It also suggests that the helical structure is stable under compression less than 367 pN, above that it is unstable. Moreover, the critical values of torsion, modes, the number of turns, and forces leading to the instability are reported. This analytical study could be a groundwork providing better understandings on DNA's deformation and relevant biological processes, and critical parameters affecting to the instability with engineering implications in designing a DNA-based functional nanodevice. [ABSTRACT FROM AUTHOR]

Freshwater supply is declining in the context of climate change, pollution, and soil salinization, calling for sustainable methods to produce drinking water. For instance, salt water can be converted into pure water by steam generation. Interfacial solar steam generation involves photoabsorbers consisting of a photothermal material with broad solar absorption and a porous substrate with a thermal insulating character. Nonetheless, scaling up of classical devices for interfacial solar steam generation is actually limited by cost, biofilm formation, salt fouling, complicated fabrication processes, and toxicity. Alternatively, wood-based devices are cheap, biodegradable, abundant, and display high fluxes of evaporation compared with other nonbiodegradable photoabsorbers. Here we review the design and applications of wood-based solar steam generation devices, with focus on wood structure and properties, different types of devices, and factors controlling the evaporative performance. [ABSTRACT FROM AUTHOR]

The entropy generation analysis in a viscous dissipative flow of a Newtonian fluid through a hyper-porous microchannel formed between two heated parallel plates is conferred. Employing an analytical method, which is consistent with the perturbation analysis, the transport equations governing the thermo-hydrodynamics are studied. The effects of nonlinear Forchheimer drag and conjugate heat transfer on the thermal transport characteristics of heat are considered, while the thermal boundary conditions of third kind have been employed at the outer boundaries of channel for the conjugate heat transfer analysis. The explicit alterations are made in the thermal transport of heat in the system as attributable to the effect of dissipative heat generated due to the non-linear effect Forchheimer drag, Darcy frictional effect and the viscous shearing stress in the flow field. To account these effects, the explicit variation of Forchhiemer constant, Darcy number, porosity, thickness and conductivity of upper wall and Biot number of upper wall are carried out to shows the changes in the available energy of the system. Also, it is shown that the effect of non-linear drag mainly stemming from the presence of complex porous structure in the flow field and its interaction with the conjugate transport of heat alters the heat transfer rate in the system non-trivially, which, in turn, gives rise to the entropy generation in the system. The individual contribution of two different effects viz., the heat transfer and viscous dissipation on the system entropy generation rate for different cases are studied. It is believed that the implications of the present analysis may have direct bearing on the design of micro devices/systems typically used in electronic cooling, micro-heat pipes. [ABSTRACT FROM AUTHOR]

Entropy generation analysis of hybrid nanofluid in a two pass multiport minichannel heat exchanger coupled with a thermoelectric cooler is experimentally investigated. Alumina (Al 2 O 3 , 50 nm), graphene (5 nm) and the hybrid of these two in equal portions with 0.1% volume concentrations is separately dispersed in to the base fluid and tested. The hydraulic diameter and aspect ratio of the channel are 1.184 mm and 0.689 respectively. The heat flux is varied from 6250 W/m 2 to 25,000 W/m 2 and the flow regime is considered to be laminar with the Reynolds number varying from 200 to 1000. The results showed an enhancement of 17.32% in cooling capacity and coefficient of performance (COP) with the use of pure graphene–water nanofluid when compared with that of the other tested combinations of nanofluids. Total entropy generation decreased from 0.0361 W/K to 0.0184 W/K with increase in Reynolds number from 200 to 1000 for the maximum applied heat flux of 25,000 W/m 2 . Similarly an enhancement of 88.62% in the convective heat transfer coefficient and a reduction of 4.7 °C in the device temperature are achieved when pure graphene–water nanofluid is used as the coolant. Among the tested nanofluids, graphene–water nanofluid shows better performance in terms of heat transfer, thermodynamic and exergic analysis. [ABSTRACT FROM AUTHOR]

Some researchers, even professors in universities, sometimes do unethical actions unintentionally due to lack of a mentor in their academic life. In this opinion piece, we aim to show that journals and publishers can play the role of a mentor for authors of scientific articles, especially young M.Sc. and Ph.D. students, to teach them the ethics in research and publishing. In this way, both journals and researchers will benefit from such a plan. [ABSTRACT FROM AUTHOR]

Data sets of internal resistances and open-circuit voltage of a particular battery are needed in ANSYS Fluent program to predict the heat generation accurately. However, one set of available data, called Chen's original, does not cover all types and shapes of batteries. Therefore, this research was intended to study the effects of shapes and polarization chemistries on heat generation in Li-ion batteries. Two kinds of material chemistries (nickel manganese cobalt oxide, NMC, and lithium iron phosphate, LFP) and three forms (cylindrical, pouch, and prismatic) were studied and validated with the experiment. Internal resistance was unique to each cell battery. Differences in shapes affected the magnitude of internal resistance, affecting the amount of heat generation. Pouch and prismatic cells had lower internal resistance than cylindrical cells. This may be the result of the forming pattern, in which the anode, cathode, and separator are rolled up, making electrons difficult to move. In contrast, the pouch and prismatic cells are formed as sandwich layers, resulting in electrons moving easily and lowering the internal resistance. The shapes and chemistries did not impact the entropy change. All batteries displayed exothermic behavior during a lower SOC that gradually became endothermic behavior at around 0.4 SOC onwards. [ABSTRACT FROM AUTHOR]

The heat transfer performance of a closed-loop pulsating heat pipe (CLPHP) having 2.2 mm inner diameter is experimentally studied at different filling ratios (40%, 50%, 60% and 70%) in a heat load range of 50–300 W using distilled water as the PHP fluid in vertical orientation with evaporator at the bottom. This experimental study validate that the optimum charging ratio is 50% for CLPHP while 40% filling ratio is good at lower heat inputs. Optimum filling ratio gives an average reduction of 26.0% and 14.8% in thermal resistance compared to 70% and 60% fill ratios. The heat transfer performance of the CLPHP is also studied at various volume fractions of graphene–water nanofluid using 50% filling ratio. This study shows that the optimum volume fraction for this CLPHP is 0.045%. The volume fraction of 0.045% gives an average reduction of 27.3% in thermal resistance for all heat inputs and a maximum temperature reduction of 24 °C for the evaporator wall temperature at 275 W heat input. When optimum values of filling ratio and volume fraction are used, CLPHP gives the best heat transfer performance. A correlation is also developed for CLPHP by considering the influential parameters. [ABSTRACT FROM AUTHOR]

The thermal management system of batteries plays a significant role in the operation of electric vehicles (EVs). The purpose of this study is to survey various parameters enhancing the performance of a heat pipe-based battery thermal management system (HP-BTMS) for cooling the lithium-ion batteries (LIBs), including the ambient temperature, coolant temperature, coolant flow rate, heat generation rate, start-up time, inclination angle of the heat pipe, and length of the condenser/evaporator section. This review provides knowledge on the HP-BTMS that can guarantee achievement of the optimum performance of an EV LIB at a high charge/discharge rate. [ABSTRACT FROM AUTHOR]

Comments on a study which discussed flow regimes and energy loss on chutes with upward inclined steps. Correlation between distance and flume lengths used in the study; Problem associated with the detection of the stagnation point in the research; Examination of the association between flow regimes and upward inclined steps.

Preparing and defining of thermal properties of new type hybrid nanofluids are essential to understand the fluidity mechanism of hybrid nanofluids and select suitable nanofluids in terms of application. This research aims to provide an alternative fluid for different applications and complete the new type of nanofluid necessity in the literature that has been reported by different research groups. In this current investigation, water-based ZnO–SiO2 hybrid nanofluid is prepared by using the two-step method, and thermal conductivity and dynamic viscosity values are experimentally specified. ZnO–SiO2 hybrid nanofluid has 0.5%, 0.75%, and 1% with 50% ZnO-50% SiO2; 33.3% ZnO-66.6% SiO2, and 66.6% ZnO-33.3% SiO2 nanoparticle mixtures. Thermal conductivity and dynamic viscosity are experimentally measured from 20 to 60 °C. Maximum thermal conductivity rising is 2.26%, and it is obtained for 1% ZnO0.66–SiO20.33 at 50 °C. Maximum dynamic viscosity increment is measured as 1.36 times of base fluid for 1% ZnO0.33–SiO20.66 at 50 °C. Changes in thermal properties are reasonable to use ZnO–SiO2 hybrid nanofluid in different thermal applications to increase system heat transfer rate and efficiency and reduce pressure drop and power consumption. Finally, two different regression equations are developed to predict the thermal conductivity and dynamic viscosity, respectively. [ABSTRACT FROM AUTHOR]

The performance of thermoelectric cooling of electronic devices with nanofluid in a multiport minichannel heat exchanger is experimentally investigated. The Bismuth Telluride (BiTe 3 ) thermoelectric cooler (TEC) with a Δ T max of 67 °C is used to extract heat from the electronic devices, which is a power transistor. The power transistor in the circuit board usually operates with the electric power ranging from 20 W to 400 W which is considered as the input power to the TEC. The aluminum oxide (Al 2 O 3 )–water nanofluid with volume concentrations of 0.1% and 0.2% is used as the coolant to remove the heat from the hot side of the TEC. The Reynolds number is varied from 200 to 1000. The result showed 40% enhancement in the coefficient of performance (COP) of thermoelectric module for 0.2% of nanoparticle volume concentration. A 9.15% decrement in thermoelectric temperature difference between the hot and cold side has also been observed for nanofluids (0.2 vol.%), which enhanced the module cooling capacity. The enhancement in local Nusselt number is found to be 23.92% for 0.2% of nanoparticles volume concentration when compared with that of water at a Reynolds number of 1000 and at 400 W power input. The migration of nanoparticles due to temperature difference (thermophoresis) from the wall of the minichannel to the center is attributed to be the reason for the higher local Nusselt number at the entrance region. The thermal effectiveness of the cooling system increases with increase in volume concentration which makes the nanofluids as a promising coolant for electronic cooling applications. [ABSTRACT FROM AUTHOR]

The calcination temperature was studied for optimum processing conditions for preparing (NdEuGd) BaCuO (NEG-123) and (NdEuGd)BaCuO (NEG-211) powders with good quality and fine size. This study used commercially available raw powders of NdO, EuO, GdO, BaO, and CuO in a purity of 99.9 % with 3-5- μm particle size. These raw powders were carefully weighed to have the compositions of NEG-123 and NEG-211 and pressed into pellets 25 g in weight. The samples were placed in a box furnace under ambient atmosphere and heated to temperatures of 820, 840, 860, and 880 C at a rate of 100 C/h, held there for 24 h, followed by cooling at 100 C/h. X-ray diffraction analyses showed that almost all the samples are single phase except NEG-123 processed at 820 C. The average particle size of NEG-123 powders increased with increasing processing temperatures, while that of NEG-211 remained in the same range below 5 μm irrespective of the treatment temperature. Since the particle size of NEG-123 powders was around 10 mm, one need to refine the particle size below 5 μm with a technique like mechanical grinding for the production of high J NEG-Ba-Cu-O bulk super conductors. NEG-211 powders will be suitable for such a use in the present form. The homemade powders were used to fabricate NEG-Ba-Cu-O bulk by cold top seeding melt growth with MgO seed following by oxygen annealing treatment. The characterization of bulk demonstrated critical temperature at 65 K with maximum critical current density of 70,000 kA/cm at 10 K with H//c-axis. [ABSTRACT FROM AUTHOR]

In the present study, the effect of volume concentration (0.05, 0.1 and 0.15 %) and temperature (10-90 °C) on viscosity and surface tension of graphene-water nanofluid has been experimentally measured. The sodium dodecyl benzene sulfonate is used as the surfactant for stable suspension of graphene. The results showed that the viscosity of graphene-water nanofluid increases with an increase in the volume concentration of nanoparticles and decreases with an increase in temperature. An average enhancement of 47.12 % in viscosity has been noted for 0.15 % volume concentration of graphene at 50 °C. The enhancement of the viscosity of the nanofluid at higher volume concentration is due to the higher shear rate. In contrast, the surface tension of the graphene-water nanofluid decreases with an increase in both volume concentration and temperature. A decrement of 18.7 % in surface tension has been noted for the same volume concentration and temperature. The surface tension reduction in nanofluid at higher volume concentrations is due to the adsorption of nanoparticles at the liquid-gas interface because of hydrophobic nature of graphene; and at higher temperatures, is due to the weakening of molecular attractions between fluid molecules and nanoparticles. The viscosity and surface tension showed stronger dependency on volume concentration than temperature. Based on the calculated effectiveness of graphene-water nanofluids, it is suggested that the graphene-water nanofluid is preferable as the better coolant for the real-time heat transfer applications. [ABSTRACT FROM AUTHOR]