The energy and exergy characteristics of 3D-pinned heat sink (HS) designs have been computationally compared as the second part of a three-part investigation. Different pin profiles, such as circular, square, triangular, strip and elliptic pins, and without pin HS are conducted with three different types of nanofluids-Al2O3-water, SiO2-water, and CuO-water for laminar forced convection. The concentrations of nanofluids vary from 0 to 5vol% with different Reynolds numbers ranging between 100 and 1000. The finite volume method employing the SIMPLE algorithm for a computational solution is applied to solve the Navier-Stokes and energy equations. Four criterions studies are explained-energy efficiency, exergy loss, and exergy efficiency of HSs with pressure drop. The results showed that the highest energy and exergy efficiencies are nearly 76% and 57%, respectively, for elliptic-pinned HSs using pure water, while about 82% and 62% using 5vol% of SiO2-water nanofluids. Besides, the elliptic-pinned HSs have a favorable reduction in the exergy loss, nearly 17% using 5vol% of SiO2-water nanofluids. Subsequently, the elliptic-pinned HS is recommended to apply with pure water considering the development in pressure drop required. However, the elliptic-pinned HSs could be employed with 5vol% of SiO2-water nanofluids regardless of the development in pressure drop required for thermal energy dissipation applications with more exergy efficiency and reduction of exergy loss.
The hydraulic-thermal characteristics of 3D pinned heat sink designs have been numerically compared as the first part of a three-part investigation. Five different pin geometries (circular, square, triangular, strip, and elliptic pins) and an unpinned heat sink with three types of nanofluids (Al2O3-H2O, SiO2-H2O, and CuO-H2O) are considered for laminar forced convection. The range of Reynolds number is from 100 to 1000, and volume fractions vary between 0% and 5%. The finite volume method is employed to solve the Navier-Stokes and energy equations by employing a SIMPLE algorithm for a computational solution. Three parameters are presented-the Nusselt number, the bottom temperature, and the hydrothermal performance of the heat sink with pressure drop data. The findings indicated that the overall hydrothermal performance of elliptic-pinned (EP) heat sinks produces the most substantial value of 3.10 for pure water. For different nanofluids, the SiO2-water nanofluids with EPs have the most significant hydrothermal performance. Also, this factor is enhanced with an increase in nanofluid concentration up to nearly 3.34 for 5% of SiO2-water. Consequently, applying the elliptic-pinned heat sinks is recommended with pure water for considering an increase in the pressure drop, with 5% of SiO2-water nanofluids, regardless of an enlargement of pressure drop for heat-dissipation applications.
A vehicle radiator is used for cooling down the hot working fluid with airflow passing over its flow passages and fins. The proper design of the radiator is very important due to space and weight limitations in automobiles. In this study, a numerical investigation has been conducted on the improvements, which can be obtained by implementing different porous fins in the radiator channels. The effects of different porous fin configurations with the same porous media volume on the heat transfer rate and pressure drop were investigated. The coefficient of performance values were presented for evaluating the overall performance. The investigated geometries included horizontal, vertical, corrugated, and wavy-corrugated configurations. The results showed that the corrugated pattern had the best thermal performance among these geometries while the horizontal configuration presented the lowest pressure loss, even though the best overall performance belonged to wavy-corrugated configuration. After selecting this configuration, the influence of different porous materials on the radiator performance was studied. Finally, the radiator with the optimum porous media configuration and material was compared to a conventional radiator. It was found that implementing this porous media in the radiator channels improves its overall thermal performance factor up to 237%.
In a recent work Wahed M. Hasona have analyzed the effects of Hall currents and magnetic field through a horizontal and asymmetric channel with peristaltic waves for a synovial nanofluid. The author aim was to extend some previous works. These comments has been prepared from the perspective point of view that the readers of the above mentioned paper may not be aware of the several potentially serious flawed analysis and typographical errors throughout that work. In the next few pages we will focus on some of these mistakes/typos clarifying that the obtained results should be reported as fabricated results that no one can rely upon. For this reason we wrote these comments to elaborate on some of these errors with suggested corrections for these errors to correct the literature and ensure its integrity. We first show that the mathematical formulation for the model used in this paper is not satisfactory. As a result, the obtained analytical and numerical results are inappropriate and do not match with any results for the peristaltic flow models.
This study provides analysis of a cooled Ranque-Hilsch vortex tube (RHVT) with various specifications. It shows how cooling influences energy conversion inside the RHVT and improves performance of the device in separation of hot gas from the cold stream within the fluid by presenting the temperature detachment (the temperature diminution of cold air (Delta T-c = T-i - T-c), isentropic efficiency (eta(is)), and coefficient of performance (COP) of divergent, convergent, and straight VTs. Two key parameters including hot tube length and number of nozzles for cooling and insulated cases are investigated to find out how the performance of the VT is affected by different geometry configurations under cooling conditions. These influences were researched for straight, convergent, and divergent VT separators under different flow characteristics. The optimum geometrical conditions for the cooling cases were identified. Results are indicative of positive influence of cooling for energy separation inside a VT. The quantities of Delta T-c, eta(is), and COP for the cooled RHVT are greater than uncooled RHVT for various types of VTs. Cooling the VTs leads to an increase of 12.5% in Delta T-c, 14.4% in eta(is), and 15.1% in COP when the base case was an uncooled VT.
This study addresses the thermo-diffusion and the diffusion-thermo phenomena in a semi-infinite absorbent channel whose walls are contracting/expanding, with heat source/sink effects. The governing partial differential equations with suitable boundary conditions are transformed to a system of dimensionless ordinary differential equations. An analytic solution of the problem has been found using a technique called homotopy analysis method (HAM). HAM gives consistently valid answers to the problem over an extensive variety of parameters and also provides better accuracy. To validate the analytical results, a comparison has been presented with a numerical solution calculated by using the parallel shooting method. The effects of dimensionless parameters, that is, deformation parameter, Reynolds number, Soret and Dufour numbers, and heat source/sink parameter on the expressions of velocity, temperature, and concentration profiles are analyzed graphically to understand the physics of the deformable channel. It has been noted that the velocity across the channel is higher for the expanding channel, as compared to that for the contracting channel. Also the Soret and Dufour number increases the temperature of the fluid, and decreases the concentration. The temperature profile has an increasing behavior in the case of heat source, and a decreasing behavior in the case of heat sink.
This paper experimentally investigates the conductive heat transfer of samples with different materials and coatings. A range of graphene oxide nanoparticle concentration has been employed. Results demonstrate that utilizing nanoparticles leads to enhancement of conductive heat transfer by 10.07% and 8.01% for EK2 and ST14 samples, respectively. The aforementioned nanoparticles also reduce coating thickness and yield an enhanced quality of the surface, in terms of mechanical properties. The convective and radiative methods of heat transfer have been ignored in this study.
In this study, the problem of heat transfer in the steady two-dimensional flow of an incompressible viscous magnetohydrodynamics nanofluid from a sink or source between two shrinkable or stretchable plates under the effect of thermal radiation has been studied. The governing differential equations have been solved numerically using a collocation method based on the barycentric rational basis functions. This method employs the derivative operational matrix of the barycentric rational bases and the weights that were introduced by Floater and Hormann. The influence of some embedding parameters, such as the solid volume fraction phi, the Reynolds number Re, the Hartmann number Ha, the Prandtl number Pr, the radiation parameter N, the stretching-shrinking parameter, C, and the angle of the channel alpha on the temperature distribution and velocity profile has been illustrated by graphs and tables. Numerical results reveal the efficiency and high accuracy of the proposed scheme compared to the previously existing solutions. Furthermore, the implementation of the proposed method is fast and the run time is short.
In the present study, the magnetohydrodynamic characteristics of an electrically conducting nanofluid flowing past an inclined stretching sheet have been studied numerically. The governing partial differential equations were transformed to nonlinear ordinary differential equations (ODEs) via suitable similarity variables. The wall suction/injection as well as Navier's first-order slip has been considered for velocity, temperature, and concentration at the wall. The ODEs were solved in a finite difference framework via a computer program written in Engineering Equation Solver platform. The effect of different parameters on the velocity, temperature, and concentration field has also been presented. Multiple slip flow finds its application in many practical fields such as microelectromechanical systems, nanoelectromechanical systems, flow of micro-organisms, rarefied gas flow, to name a few.
In this study, a two-fluid Eulerian-Eulerian model has been carried out applying the kinetic theory of granular flow (KTGF) to study the hydrodynamics and heat transfer behavior of a fluidized bed reactor simultaneously. The effects of different gas-solid flow regimes on the operating conditions and heat transfer rate between the hot air and two types of low and high-density inert particles are investigated in a fluidized bed dryer. Different gas-solid flow regimes for wood and glass particles of groups A, B, and D of Geldart's classification are simulated to introduce the most optimal flow regime in terms of heat transfer rate and operating costs. The compromise between the heating rate, the height required for the reactor, and the ratio of the final mass to the initial mass of solid particles, which specifies the need for a cyclone separator showed that the bubbling regime of Geldart B powder for low-density particles and the turbulent regime of Geldart D powder or bubbling regime of Geldart B powder for high-density particles are the optimal operating conditions and flow regimes. Furthermore, it was concluded that the convective heat transfer is the dominant mechanism, which increases with increasing the air velocity and decreasing the particle diameter in each group.
In this paper, the distribution of C and Cr in the microsegregation of Fe-1C-1.42Cr-bearing steel was measured by experimental and numerical simulation methods. Melting points of the low-melting zones were calculated with the Thermo-Calc system; and then the verifications were made by heat treatment experiments and the temperature and time required for the bulk carbide dissolution process of bearing steel were tested. Bulk carbides could be dissolved by soaking for 60 minutes above 1260 degrees C.
The heat transfer phenomena inside a horizontal channel with an open trapezoidal enclosure subjected to a heat source of different lengths was investigated numerically in the present work. The heat source is considered as a local heating element of varying length, which is embedded at the bottom wall of the enclosure and maintained at a constant temperature. The air flow enters the channel horizontally at a constant cold temperature and a fixed velocity. The other walls of the enclosure and the channel are kept thermally insulated. The flow is assumed laminar, incompressible, and two-dimensional, whereas the fluid is considered Newtonian. The results are presented in the form of the contours of velocity, isotherms, and Nusselt numbers profiles for various values of the dimensionless heat source lengths (0.16 <= epsilon <= 1). while, both Prandtl and Reynolds numbers are kept constant at (Pr = 0.71) and (Re = 100), respectively. The results indicated that the distribution of the isotherms depends significantly on the length of the heat source. Also, it was noted that both the local and the average Nusselt numbers increase as the local heat source length increases. Moreover, the maximum temperature is located near the heat source location.
The present study has been conducted to acquire the solutions for the flow problem of an incompressible nanofluid past a permeable inclined plate implanted in a porous medium. In this study, double-diffusivity, Brownian motion, and thermophoresis as well as passive control nanoparticles have been studied. We employ Lie group transformation on the ruling equations to extract nonlinear ordinary differential equations and solve them numerically using the fourth-order Runge-Kutta method and shooting approach. The supremacy of affined parameters on temperature and velocity distributions has been exposed by means of tables and graphs. This investigation suggests that both fluid velocity and nanoparticle concentration are enhanced by the modified Dufour parameter and the thermophoresis parameter. The assistance of the Lewis number intensifies the heat transport for suction.
Magnetohydrodynamic (MHD) flow of micropolar fluid by including the thermal radiation and convective condition on a shrinking surface in the presence of mass suction effects has been investigated. The momentum, angular momentum and energy equations, and the solutions of these equations are valid for whole Navier stokes, and microrotational and energy equations have been solved exactly. We obtain the solution in the form of an incomplete γ function for the energy equation. The results reveal that dual solutions exist for certain domains of different physical parameters. Furthermore, high suction produces the high effect of drag force, and as a result, coefficient of skin friction increases in the first solution. Stability analysis has been performed and determined that the first solution is more stable.
Magnetoconvection in a rotating fluid due to thermal and compositional buoyancy with anisotropic diffusivities is investigated by both linear and weakly nonlinear analyses. By linear stability analysis, the threshold values of physical parameters give conditions for the occurrence of various types of bifurcations. By using multiple scale analysis, the nonlinear two-dimensional amplitude equation is derived and occurrence of secondary instabilities is investigated. Nusselt number is used to study heat transport. Furthermore, the effect of stratification anisotropy is to enhance heat transport. The system of coupled amplitude equations is also derived.
An analysis has been implemented to study the influences of nonconstant viscosity and magnetohydrodynamics on pseudoplastic nanofluid through a porous medium. Ohmic dissipation, chemical reaction, and heat generation are taken into consideration. The current problem is debated under the molds of tiny or zero Re and delta approximation. Two models of nonconstant viscosity are deliberated. Model (I)-all parameters are nondimensional and have been measured as constants inside the flow. Model (II)-all these stated nondimensional parameters have been considered to differ with the temperature. Comparison among the solutions achieved by utilizing numerical results and multi-step differential transform method (Ms-DTM) is displayed in excellent agreement. Attention is dedicated to beta, eta-, and Nb parameters. The governing equations for each case have been explained by an easy and highly perfect series established seminumerical Ms-DTM utilizing Mathematica 11, which uses mathematical software package. Nanofluids are active for drug carrying and drug delivery systems because of the Nb control with the velocity of fluid.
The main aim of the current paper is to investigate the mass and heat transportation of a Casson nanomaterial generated by the inclination of the surface. The magnetic field effect along with suction or injection are considered. The working nanomaterial is taken into consideration based on the concept of the Buongiorno nanofluid theory, which explores the thermal efficiencies of liquid flows under movement of Brownian and thermophoretic phenomena. The emergent system of differential expressions is converted to dimensionless form with the help of the appropriate transformations. This system is numerically executed by the implementation of Keller–Box and Newton’s schemes. A good agreement of results can be found with the previous data in a limiting approach. The behavior of the physical quantities under concern, including energy exchange, Sherwood number, and wall shear stress are portrayed through graphs and in tabular form. The Nusselt number and Sherwood number are found to diminish against the altered magnitudes of Brownian motion and the inclination parameter. Moreover, the velocity profile decreases with the growth of the inclination effect. In the same vein, the buoyancy force and solutal buoyancy effects show a direct relation with the velocity field. The outcomes have promising technological uses in liquid‐based systems related to stretchable constituents.
The model of double-diffusive convection in a porous medium layer was analyzed using the Brinkman model and concentration based on an internal heat source. Linear instability analysis of the model was performed. Particularly, we analyzed the effect of slip boundary conditions on the instability of the system. We analyzed when the instability started and computed the critical Rayleigh number as a function of the slip coefficient.
The flow of hybrid nanoparticles with significant physical parameters with different base fluids in the presence of Biot number, velocity slip, and MHD effects has not been explored so far, particularly for a circular cylinder. Therefore, the current report is presented to offer a numerical solution for hybrid nanoparticles with base fluids (water and ethylene glycerol) via a circular cylinder. The physical situation is interpreted in terms of partial differential equations and is converted into ordinary differential equations after applying the similarity transformation. The results are presented in both tabular and graphical forms. The impact of physical parameters on velocity distribution is examined through graphs. The comparative results of hybrid nanoparticles for distinct base fluids as ethylene glycol and water are proposed and the hybrid nanoparticles with base fluid water seems to be greater than that of the hybrid nanoparticles with base fluid EG. The temperature profile of hybrid nanoparticles is found to be a decreasing function with growth in velocity slip parameter gamma but an opposite trend is noted in case of nanoparticles phi 2. The skin friction and Nusselt number augmented for the increase in magnetic field, velocity slip, and nanoparticle while it shows a decreasing trend toward thermal slip parameter. For the both cases, improvement in Biot number helps enhance the heat transfer constantly.
The present study investigates a unit for making use of freshwater in a kiln in a practical manner. At first, in this unit, the saline wastewater flowing out of the MED unit in Mobin Petrochemical Complex enters a gravitational bed and is subjected to preliminary treatment. In the next stage, the same saline wastewater enters the first pretreatment reactor for undergoing a coagulation procedure; then, it enters a second biological reactor for undergoing both coagulation and biological treatment. Afterwards, the output current of the biological reactor enters a solar pond for the separation of the dissolved salt in the wastewater, for which, it enters an antiseptic system that uses ultraviolet (UV) for treatment. Finally, the saline wastewater is transformed into a soft treated current. In the present study, the performance of a solar condensation unit installed on the path of the output wastewater of the UV antiseptic unit has been examined. In this study, the thermal output, conduction output, and freshwater production output have been altogether subjected to practical evaluation. The results offered herein are indicative of the relative error rates equal to about 7.2% and 4.9% for thermal output of day and night, respectively. Moreover, the conduction efficiency relative errors have been about 7% and 5.6% for day and night, respectively. In addition, on average, the relative cumulative error of the thermal energy storage substrate's output was about 3.5% per day over a month.
