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In this study, turbulent flow and heat transfer of water in a solar collector equipped with corrugated booster reflectors to apply in cooling photovoltaic cells (PV) are investigated. 3D simulation is done using by the control volume method and SIMPLEC algorithm. The optimization was carried out by comparison of different parameters to reach the optimal situation with the maximum efficiencies of energy and exergy. It is established that in the case of corrugated booster reflectors, the temperature of outlet fluid and efficiencies of energy and exergy are more. In general, while the trend of variation of exergy efficacy with impressive parameters is increasing, using the mixers precipitate the efficacy increment. Furthermore, for the case that the trend of variation of exergy efficacy with altering these parameters is reducing, the reducing trend gets slow. Finally, it is realized that using corrugated booster reflectors have a significant effect on collector efficacy, and the highest exergy efficacy was obtained for the 50° corrugations. At Re = 6800, the maximum Nusselt number achieves and it is about 6.03. Finally, using an artificial neural network, the output parameters were navigated with acceptable accuracy. For 76.6% of the data points, the margin of deviation (MOD) was

Aero-thermal optimization on multi-rows of film cooling over a flat plate has been performed to optimize the inclination angles. Hence three cylindrical holes with injection angles of ?, ?, and ? have been considered. The cooling hole has a 3 mm diameter and an inclined angle between 25-35?. Numerical simulations were performed at a fixed density ratio of 1.25 and blowing ratio of 0.5. The control-volume method with a SIMPLEC algorithm has been used to solve the steady-state RANS equations with SST k-? turbulent model. The injection angles of the holes are selected as the design variables to perform the optimization of three rows of film cooling. In order to evaluate the performance of holes arrangement, two objective functions are defined based on aerodynamic losses and adiabatic film cooling effectiveness. The curve fitting method is used to find the optimal point of objective functions. The optimizations have been performed using the genetic algorithm method. Results of the present study show that the best performance of three rows of cooling holes was achieved in inclined angles 25.45, 32.85, and 33.1.

The aim of this paper is to achieve a smaller and cheaper heat exchanger with similar performance. To fulfill this demand, ANSYS-Fluent software and Aspen-HYSYS software are employed. The second goal is to study the effects of using oil-based nanofluids in a refinery heat exchanger. To fulfill this demand, two different nanofluids (MgO-SAE10 and ZnO-SAE10) are studied using two-phase approaches. And the third objective of this paper is to compare the results which are obtained from the singe- and multi-phase approaches. The governing equations have been solved according to the Eulerian–Eulerian single-fluid Two-Phase Model, with presumptuous that the coupling between phases is strong, and nanoparticles carefully follow the suspension flow. The FVM, SIMPLEC algorithm and k–e turbulence model are applied. The thermal–hydraulic performance evaluation criteria, THPEC, and q″ have major roles. In the second step, the authors try to achieve an efficient model which not only has the THPEC > 1, but also has the maximum value of q″. According to the results, usage of nanofluid and turbulators can enhance thermal–hydraulic performances of heat exchanger significantly (between 84.78 and 105.31% for heat exchanger 1 and between 86.84% and 107.68% for heat exchanger 2). Furthermore, it is concluded that by employing nanofluid and turbulators the costs of manufacturing the refinery heat exchangers are sharply reduced.

In the current study, the turbulent forced convection heat transfer of Fe3O4/-CNT/water hybrid nanofluid (HNF) in a heat exchanger (HE) equipped with blade-shape turbulators is studied. The 3D governing equations have been solved numerically with SIMPLEC algorithm and solution domain by employing the control volume method (CVM). The impact of Reynolds number (Re), volume concentration of Fe3O4 nanoparticles (φM) and CNTs (φCNT) and blade-rod diameter (dr) on the performance features of HE are evaluated. The results showed that the PEC of HNF augments with the augmentation of Re and φM, while with intensifying dr, the PEC first rises and then declines. The outcomes showed that the highest PEC occurs at Re = 9000, φM = 0.9%, φCNT = 1.35% and dr = 15mm.

The behavior and characteristics of the wake produced behind an elliptic cylinder at 0° angle of attack, in the presence of trip wires, are investigated experimentally and numerically. For this purpose, an aluminum cylinder model with an elliptic cross section and a length of 390 mm, major diameter of 42.4 mm and minor diameter of 21.2 mm was tested in the test section of a wind tunnel. Realizable k–e turbulence model was used for the numerical analysis and SIMPLEC algorithm was employed for pressure–velocity coupling. Reynolds numbers corresponding to the major diameter of the cylinder were 38,550 and 64,250 for air velocities of 15 m/s and 25 m/s, respectively. Turbulence trip wires of .5 mm diameter were installed symmetrically on the elliptic cylinder at angles of 23.7° and 40.9° relative to the stagnation point. The drag coefficient for the smooth elliptic cylinder was about .6 at both Reynolds numbers. Results showed a drag coefficient reduction of 75% in the best possible case. It was also concluded that a turbulence promoter wire has a significant effect on flow characteristics and reduction in the drag coefficient, and that it strongly depends on the location where the trip wire is installed on the model.

The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a two-dimensional rectangular channel with triangular and semicircular vortex generators with three different heights of 1, 2 and 3 mm. For numerically modeling this study, SIMPLEC algorithm was used. Therefore, initially, the geometry of channel and the grid points were generated, and then for solving the mathematical equations via finite volume method, ANSYS Fluent was used. The results indicate that with an increase in Reynolds number and volume fraction (φ) of nanoparticles, the average Nusselt number increases. Also, with an increase in the φ, the pressure loss in the channel increases. About the geometrical shape of the vortex generators, results indicate that with using the semicircular vortex generator, average Nusselt number is higher compared to that of triangular vortex generator. Also, by investigating the performance evaluation criteria of thermal–hydraulic, which is a criterion for comparing the positive effect of the Nusselt number increase with the negative effect of pressure drop, results indicate that this criterion is higher for the semicircular vortex generator.

In this research, laminar flow and heat transfer of two-phase water/Ag nanofluid with 0–6% volume fraction of nanoparticles at Re = 150–700 in a curved geometry are simulated using finite volume method. Studied geometry is an elliptical curved minichannel with curvature angle of 180o. Forced and natural flow of two-phase nanofluid is simulated at Gr = 15,000, 35,000 and 75,000. For estimation of nanofluid flow behavior, two-phase mixture method is used. The second-order discretization and SIMPLEC algorithm are used for solving governing equations. The results indicate that, the increase of volume fraction of nanoparticles leads to the enhancement of the temperature of central line of flow. The increase of Grashof number (Gr ~ 75,000) has a great effect on reduction of dimensionless temperature in central line of flow. Creation of thermal boundary layer at Re = 500 and after the angle of 30o becomes significant. In low Grashof numbers (Gr ~ 15,000), due to the great effects of temperature gradients close to wall, these regions have significant entropy generation.

In this paper, the numerical solution of non-Newtonian two-phase fluid-flow through a channel with a cavity was studied. Carreau-Yasuda non-Newtonian model which represents well the dependence of stress on shear rate was used and the effect of n index of the model and the effect of input Reynolds on the attribution of flow were considered. Governing equations were discretized using the finite volume method on staggered grid and the form of allocating flow parameters on staggered grid is based on marker and cell method. The QUICK scheme is employed for the convection terms in the momentum equations, also the convection term is discretized by using the hybrid upwind-central scheme. In order to increase the accuracy of making discrete, second order Van Leer accuracy method was used. For mixed solution of velocity-pressure field SIMPLEC algorithm was used and for pressure correction equation iteratively line-by-line TDMA solution procedure and the strongly implicit procedure was used. As the results show, by increasing Reynolds number, the time of sweeping the non-Newtonian fluid inside the cavity decreases, the velocity of Newtonian fluid increases and the pressure decreases. In the second section, by increasing n index, the velocity increases and the volume fraction of non-Newtonian fluid after cavity increases and by increasing velocity, the pressure decreases. Also changes in the velocity, pressure and volume fraction of fluids inside the channel and cavity are more sensible to changing the Reynolds number instead of changing n index.

In this study, the convective mode heat transfer phenomena of bi-phase elasticoviscous (non-Newtonian) nanofluid is quantified by forcefully flowing it through a specially designed microchannel test section. The test section, which is rectangularly cross-sectioned and annexed internally with cylindrical needle ribs is numerically investigated by considering the walls to be maintained at a constant temperature, and to be susceptible to a magnetizing force field. The governing system-state equations are numerically deciphered using control volume procedure and SIMPLEC algorithm. With the Reynolds number (Re) varying in the turbulent range from 3000 to 11,000, the system-state equations are solved using the Eulerian–Eulerian monofluid Two-Phase Model (TPM). For the purpose of achieving an apt geometry based on the best thermo-hydraulic behavior, an optimization study must be mandatory. The geometry of the cylindrical rib consists of h (10 × 10−3, 15 × 10−3, 20 × 10−3), p (1.0, 1.5), and d (8 × 10−3, 10 × 10−3, 12 × 10−3), which, respectively, defines the height, pitch, and diameter of the obstacles, with the dimensions placed within the braces being quantified in mm. The results demonstrated that the magnetic field leads to an enhanced amount of average Nusselt number (Nuav) in contrast with the occurrence at B = 0.0. This is due to the that the magnetic field pushes nanoparticles towards the bottom wall. It was found that B = 0.5 T has the maximum heat transfer compared with the other magnetic fields. The channel with h = 15 μm height leads to the maximum value of Nuav at all studied Re for constant values of d and h. The channel with p = 1.5 μm results in the maximum value of Nuav at all studied Re for constant values of d and h. The microchannel with d = 8 μm, p = 1.5 μm, and h = 15 μm in the presence of the magnetic field with B = 0.5 T is the best geometry in the present work.

PurposeAlthough many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices.Design/methodology/approachPresent numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10−6is considered for saving computer memory usage and the time for the numerical solving procedure.FindingsIn constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent.Research limitations/implicationsThe numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it.Practical implicationsThe authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices.Originality/valueThis manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.

Purpose This study aims to numerically investigate the heat transfer and laminar forced and two-phase flow of Water/Cu nanofluid in a rectangular microchannel with oblique ribs with angle of attacks equal to 0-45°. This simulation was conducted in the range of Reynolds numbers of 5-120 in volume fractions of 0, 2 and 4 per cent of solid nanoparticles in three-dimensional space. Design/methodology/approach This study investigates the effect of the changes of angle of attack of rectangular rib on heat transfer and hydrodynamics of two-phase flow. This study was done in three-dimensional space and simulation was done with finite volume method. SIMPLEC algorithm and second-order discretization of equations were used to increase the accuracy of results. The usage of nanofluid, application of rips with different angles of attacks and using the two-phase mixture method is the distinction of this paper compared with other studies. Findings The results of this research revealed that the changing angle of attack of ribs is an effective factor in heat transfer enhancement. On the other hand, the existence of rib on the internal surfaces of a microchannel increases friction coefficient. By increasing the volume fraction of nanoparticles, due to the augmentation of fluid density and viscosity, the pressure drop increases significantly. For all of the angle of attacks studied in this paper, the maximum rate of performance evaluation criterion has been obtained in Reynolds number of 30 and the minimum amount of performance evaluation criterion was been obtained in Reynolds numbers of 5 and 120. Originality/value Many studies have been done in the field of heat transfer in ribbed microchannel. In this paper, the laminar flow in the ribbed microchannel Water/Cu nanofluid in a rectangular microchannel by using two-phase mixture method is numerically investigated with different volume fractions (0-4 per cent), Reynolds numbers (5-120) and angle of attacks of rectangular rib in the indented microchannel (0-45°).

A numerical investigation has been taken up to assess the efficacy of a design innovation for rectangular microchannel heat sink by applying the concepts of maximization of thermal performance (TP) and minimization of entropy generation (EG). The channel is conceived as a serial arrangement of modifying units, each with a rib symmetrically located between trapezoidal cavities (TRC) on opposite side walls. Based on SIMPLEC algorithm for the flow along with conduction through the bounding walls and the internal ribs, a three dimensional laminar-flow conjugate heat-transfer study has been carried out between Reynolds number (Re) of 140 and 600 following a validation against a representative numerical and experimental study. A comparison among the predictions of constant fluid property model and models incorporating their realistic variations with temperature has shown the cooling to be dominated by convection, of course more strongly at higher Re. Substantially higher thermal conductivity of copper than that of silicon have revealed moderate increase in bulk fluid temperature and even lower increase of substrate temperature. Four different rib structures have been considered that are rectangular (RR), backward triangular (BTR), forward triangular (FTR) and diamond (DR). The predictions against Re indicated the best TP with diamond rib combination (TRC-DR) and the highest EG with backward triangular rib combination (TRC-BTR). A notable contribution of this work is establishing the concept of minimization of EG under the constraint of given pumping power to be equivalent to the concept of maximization of TP. The effects of parametric variations of relative width and length of cavity and relative width and pitch of rib have been investigated and the highest TP has been predicted around Re of 328.

In order to explore the internal wind field flow characteristics of T4-72 type centrifugal fan, the three-dimensional model was established based on PRO/E software. Combined with computational fluid Dynamics Software Fluent 6.3, the standard model and SIMPLEC algorithm were used to simulate the wind field inside the fan. Analysis of the flow characteristics, velocity distributed and pressure distributed of the internal fluid model of the T4-72 centrifugal fan, combined with the theoretical formula to obtain the full pressure, power and efficiency performance parameters of the fan. The centrifugal fan performance curve is drawn. While compared with the experimental data, it is found that the internal flow disturbance is strong when the fan is running under low load condition and high load condition, which affects the performance of the fan and reduces the life of the fan. The numerical simulation results are consistent with the experimental results. The overall performance parameters of the fan are in good agreement, verifying the reliability of the simulation results; when the fan works between 1 - 1.4 times the rated flow rate, it can obtain a more stable flow field while maintaining higher efficiency, which provides a new idea for the optimization of the subsequent fan.

Viruses can be transmitted in indoor environments. Important factors in Indoor Air Quality (IAQ) are air velocity, relative humidity, temperature, and airflow pattern and Computational fluid dynamics (CFD) can use for IAQ assessment. The objective of this study is to CFD simulation in the living room to the prediction of the air pattern and air velocity. A computational fluid dynamic model was applied for airflow pattern and air velocity simulation. For simulation, GAMBIT, FLUENT, and CFD post software were used as preprocessing, processing, and post-processing, respectively. CFD validation was carried out by comparing the computed data with the experimental measurements. The final mesh number was set to 1,416,884 elementary cells and SIMPLEC algorithm was used for pressure-velocity coupling. PERSTO, and QUIK schemes have been used for the pressure terms, and the other variables, respectively. Simulations were carried out in ACH equals 3, 6 and 8 in four lateral walls. The maximum error and root mean square error from the air velocity were 14% and 0.10, respectively. Terminal settling velocity and relaxation time were equal to 0.302 ×10− 2 m/s and 0.0308 ×10− 2 s for 10 µm diameter particles, respectively. The stopping distance was 0.0089m and 0.011m for breathing and talking, respectively. The maximum of mean air velocity is in scenario 4 with ACH = 8 that mean air velocity is equal to 0.31 in 1.1m height, respectively. The results of this study showed that avoiding family gatherings is necessary for exposure control and suitable airflow and pattern can be improving indoor air conditions.

A double-diffusive mixed convection within low-turbulent regime in a ventilated cavities filled with an air-CO2 mixture and heated from below has been numerically investigated. The lower wall was sustained at a uniform temperature and CO2-concentration. The vertical and upper walls were kept at external temperature and CO2-concentration. To analyze the behavior of flow, the ventilation effectiveness for temperature distribution and removal of CO2-contaminant, four configurations were dealt. These differ from each other by the location of the mixture inlet and outlet gaps. Likewise, three CO2-concentrations were considered (103, 2x103 and 3x103 ppm) to investigate the influence of the CO2-diffusion on the ventilation effectiveness. The numerical simulations were performed by considering closed Reynolds averaged-Navier-Stokes (RANS) equations using the Re-Normalization Group k-e model. The governing equations' set was then solved using the finite volume method, in which the pressure-velocity coupling was handled using the SIMPLEC algorithm. Validation of the numerical model was achieved by comparing our results with available experimental data. The obtained results indicate that the CO2-diffusion effect on the air movement and the ventilation effectiveness for temperature distribution can be neglected in the present study. However, the CO2-diffusion remains a key parameter in terms of indoor air quality index. Also, it was found that one of the studied configurations provides a better ventilation effectiveness to remove heat and CO2-contaminant, and insures a homogeneous temperature and CO2-concentration in the occupied zone. The three other configurations maintain an acceptable level of heat and can be used in temperate climate to ensure good indoor air quality.

Convective heat transfer using nanofluids play an important role in thermal applications such as heat exchangers, automotive industries, and power generation. In this work, a numerical analysis is conducted to examine the heat transfer of nanofluid in three-dimensional differentially heated cavity. The finite volume method-based SIMPLEC algorithm is used to solve the system of the mass, momentum, and energy transfer governing equations. The left and the right vertical side walls of the cube are maintained at constant temperatures T C and T H , respectively. The remaining walls of the cube are insulated. Effective thermal conductivity and viscosity of the nanofluid are determined using Brinkman and Maxwell models, respectively. Studies are carried out for three types of nanoparticles and volume fractions of nanoparticles ( 0 – 5 % ). The effects of two binary liquid mixtures as a base fluid (propylene glycol-water and ethylene glycol-water) are also examined. Results show an enhancement of 13 % for Al2O3-EG in comparison to pure ethylene glycol in the case of Ra = 10 3 . In addition, heat transfer enhancement was increased with the rise of nanoparticle volume fractions.

A numerical analysis was performed to study free convection in a stationary laminar regime in a partially heated cube filled with ionanofluid. To numerically solve the dimensionless equations, we applied the finite volume method using the SIMPLEC algorithm for pressure correction. All walls are adiabatic, except for the left and right side walls which are partially heated differently. At the end of this simulation, several results are given in the form of current lines, isotherms, and variations in the Nusselt number. These results are obtained by analyzing the effect of a set of factors such as Rayleigh number, particle volume fraction, cold and source position on the dynamic and thermal fields, and heat transfer. It has been shown that the percentage of nanoparticles and high Rayleigh numbers significantly increase heat transfer by ionanofluid. Two comparisons have been made, between ionic fluid and ionanofluid at isotherms and streamlines, and between nanofluid and ionanofluid at Nusselt number, which show the advantage of using ionanofluid in heat transfer.

This paper presents a fractional step time stepping scheme for low-Mach number compressible flow. The advantage of the proposed scheme compared to the iterative SIMPLEC is significant saving in computation effort while preserving secondorder accuracy. The proposed scheme and a transient SIMPLEC algorithm are verified and validated using a 2D convective isentropic vortex to qualitatively evaluate their convergence properties. Both schemes are stable at convective Co number equal one, and acoustic CFL greater than one. The L2 error norms of both schemes show second order accuracy, but the proposed scheme uses significantly less computation effort. Next, the aerodynamics of flow past a SAE 20 Notchback Model is predicted using the proposed scheme. Results of the SAE Model show good grid convergence, and good agreement in surface pressure coefficients with experimental measurement.

In this paper, a three-dimensional numerical analysis was employed to investigate the flow and thermal fields over a leading edge of AGTB-B1 high-pressure turbine blade. The effect of different parameters on the film cooling was studied. The computational methodology includes the use of a structured, non-uniform hexahedral grid consisting of the main flow channel, the coolant delivery tube and the feeding plenum. The SIMPLEC algorithm was implemented for pressure–velocity coupling. Computations were carried out for the following range of film cooling parameters: lateral position of sister holes 3, 3.5 and 4.75 mm; lateral angle of sister holes of − 8°, 0° and 8°; blowing ratio of 0.7, 1.1 and 1.5; and diameter of injection hole of 2, 2.5 and 3. Adiabatic effectiveness was used as a criterion to judge the performance of film cooling. The results show a good agreement compared with previous experimental and numerical data. Finally, the GMDH-type neural network was successfully employed for modeling and presenting a correlation for film cooling effectiveness as a function of effective parameters.

In this chapter, the influences of variable magnetic field on the heat transfer of ferrofluid within a T-junction were investigated. The ferrofluid inside T-junction is assumed single phase and laminar and constant heat flux is applied on the wall while three wires are chosen as a source of nonuniform magnetic field. The finite volume method with the SIMPLEC algorithm is applied to simulate the effects of nonuniform magnetic field on the thermal and friction factor of ferrofluid.

To solve the blockage and fouling issues of sewage heat exchangers in sewage source heat pump, a novel de-foulant hydrocyclone with ejection device was proposed and studied with FLUENT software. The pressure and velocity fields were coupled by the SIMPLEC algorithm, whereas the Reynolds Stress Model was used to predict the 3-D strong swirling turbulent flow due to its anisotropic nature. The Discrete Phase Model was employed to study the particle motion. Results showed that, compared with the variable underflow-pipe diameter, adjusting the ejection velocity could significantly enhance the separation performance by achieving the low split ratio without the risk of blocking the underflow pipe. Unlike the effects of conventional ejectors, the increasing ejection velocity increased the back pressure of the underflow and hence decreased the split ratio. Specifically, if the ejection velocity was higher than a certain value (e.g., 2.0 m/s in this paper), all the 3-D strong swirling turbulent flows in hydrocyclones would be flushed out through the vortex finder by the ejected fluid. In addition, the range of the optimum ejection velocity did exist (e.g., 1.5–2.0 m/s in this paper). In general, the increasing ejection velocity increased the pressure and velocity in hydrocyclones.

Some improvements for SIMPLE algorithm have been proposed in the present paper. After the discretized momentum equations are solved implicitly, an extra explicit prediction for velocity will be adopted to eliminate iterative errors introduced in previous implicit prediction step. As for consistent approximation, the velocity-correction formula is amended so that the corrected velocity and corrected pressure are better to satisfy the momentum equations without relaxation and the continuity equation. Moreover, the velocity relaxation factor α is also introduced to velocity-correction formula for obtaining the appropriate velocity correction. In the SIMPLEPC algorithm, letters “P” and “C” appended to SIMPLE represent extra prediction and consistent approximation, respectively. The numerical experiments show that SIMPLEPC can always converge with less time and similar robustness compared to the SIMPLEC algorithm. When the time step multiplier (E) is less than 4 (the corresponding velocity relaxation factor α is less than 0.8), the time consumption ratio (TCR) is approximately less than 0.8. The performance of SIMPLEPC is better than SIMPLEC especially with low time step multiplier.

In this research, the effects of non-uniform magnetic field on the heat transfer of ferrofluid inside a T-junction are investigated. The finite volume method with the SIMPLEC algorithm is applied to simulate the effects of non-uniform magnetic field on the thermal and friction factor of ferrofluid. The ferrofluid inside T-junction is assumed single phase and laminar and constant heat flux is applied on the wall while three wires are chosen as a source of non-uniform magnetic field. This study focused on main effects of magnetic field on the flow feature and temperature distribution in the vicinity of magnetic source. Comprehensive parametric studies are performed to investigate the influence of various factors such as intensity of magnetic field and Reynolds number on the heat transfer. Obtained results show that average heat transfer of ferrofluid rises more than 64% when magnetic field is applied. In addition, the local heat transfer increases more than 200% in vicinity of the first magnetic field.

Jet impingement cooling of vertical moving plate is widely employed in the energy and metallurgical industries. To improve heat transfer and the cooling of these plates in a vertical channel, an innovative stepwise jet cooling design model was proposed in the present study. To investigate the heat transfer enhancement mechanism of this multiple jet cooling, mixed convection in a three-dimensional model of a soaking zone and a jet impingement cooling tower was simulated using the commercial program ANSYS CFX. Navier–Stokes equations, which were solved using the SIMPLEC algorithm, enclosed by an RNG k-e two-equation turbulence model were employed to calculate the fluid flow and heat transfer. Based on observations of the airflow velocity vector and temperature distribution, the critical equilibrium state for buoyancy and the inertia force was found to occur at a combined Reynolds number of 1.40 × 107. Based on this double-enhancement effect and the effect of different nozzle heights, a multiple stepped jet impingement cooling design that jet velocity decreased with its height increasing was applied to a vertical alloying furnace. The Nusselt number for stepwise jet cooling in the vertical alloying furnace was 111–118% higher than that for constant jet cooling. Therefore, the stepped jet cooling model offers greater energy conservation than does constant velocity when the total jet flow mass is held constant.

In the present study, the turbulent flow of water/Al2O3 nanofluid in a tubular heat exchanger with two twisted-tape inserts has been numerically investigated in the three-dimensional coordinate. This numerical simulation has been done by using FVM, and all of the equations have been discretized by second-order upwind method. For coupling velocity–pressure equations, SIMPLEC algorithm has been used. The investigated parameters of the present study are Reynolds numbers at the range of 10,000–30,000, the effect of twist ratio of twisted-tape inserts from 2.5 to 4, co-swirl flow and counter-swirl flow of two twisted-tapes inside the tube and volume fractions of nanofluid from 1 to 4%. The results of this research revealed that, by decreasing the twist ratio, the counter-swirl flow twisted-tape and the enhancement of volume fraction of Al2O3 nanoparticles in the base fluid, the amount of average Nusselt number increases. In twist ratios of 3.25 and 2.5, the maximum amounts of performance evaluation criterion (PEC) are 1.6 and 1.55, respectively. Also, the amount of PEC improvement in counter-swirl flow state is considerably more than co-swirl flow state. Therefore, the maximum enhancements of PEC improvement in three twist ratios of 4, 3.25 and 2.5 are, respectively, 40.8, 47 and 51% and the maximum enhancements in three mentioned ratios are 26.5, 28.3 and 30.6%, respectively.

In order to solve the problem that the inner surface of heterosexual surface parts is difficult to be machined, a solid-liquid two-phase abrasive flow machining method is proposed. The standard model and the pressure-coupled SIMPLEC algorithm are used. The dynamic characteristics of the dynamic pressure, turbulent kinetic energy and turbulence intensity of the polygonal spiral surface flow channel were obtained by numerical analysis of the solid-liquid two-phase abrasive grain polished polygonal spiral curved pipe under different outlet pressure conditions. The numerical simulation results show that the grinding effect is inversely proportional to the outlet pressure. We can achieve better polishing effect by appropriately reducing the outlet pressure.

The current study reports both experimental and numerical studies on flow and heat transfer characteristics of straight and wavy miniature heat sinks (MHSs). Effects of different interruptions of pin-fin and concentrations of Al2O3/water nanofluids (0, 0.1, and 0.4 wt.%) are investigated. For the experimental part, three pin-fin interruptions and nanoparticle concentrations are considered and tested for Reynolds number ranged from 100 to 900. For the numerical part, a conjugate simulation is carried out using the finite volume approach and SIMPLEC algorithm. A comparison is conceded between the integral and the interrupted MHSs. The results are presented in terms of base temperature, heat transfer coefficient, Nusselt number, pressure drop, pumping power, and performance factor. It is found that the interrupted MHSs have better hydrothermal performance and more uniform temperature distribution. Also, the application of Al2O3/water nanofluids improves the overall hydrothermal performance of straight and the wavy MHSs. The maximum performance factors of 2.65 and 2.46 are obtained, respectively, for the 0.4 wt.% nanofluid flow in the straight and wavy MHSs with interrupted-staggered arrangement of pin-fins. Based on the current evaluation, it can be concluded that the pin-fin interruption and nanofluid flow have considerable effects on the performance of straight and wavy MHSs.

The classic method of modelling drying processes using the transfer coefficients can be replaced by a method of solving Reynolds-Averaged Navier-Stokes equations applicable to the drying medium. This specifically applies to superheated steam (SS) as the drying medium, where the mass transfer coefficient cannot be defined by heat transfer analogy. In this study, the heat and mass transfer phenomena of SS drying of distillers’ spent grain (DSG) pellets were numerically studied using a commercial Computational Fluid Dynamics (CFD) package by combining the drying models related to the moist cylinder with the model describing the external flow of SS. A three-dimensional (3D) model of the DSG pellet and the drying chamber was created. The governing differential equations for mass and energy balance of the pellet and steam-flow around it were solved using the finite volume method and SIMPLEC algorithm within the CFD package (ANSYS CFX). The validation of the numerical model with experimental observations showed a good agreement with a mean relative percentage error less than or equal to 10%. The obtained mathematical model could serve as a basic tool for optimization and design of large-scale SS dryers for DSG.

In order to solve the problem that the aperture of the small hole part is too small and the irregular shape of the surface is difficult to be processed. A solid - liquid two - phase abrasive grain polishing method is proposed. Based on the standard model and SIMPLEC algorithm, the numerical simulation of the surface of the micro – holes were carried out under different inlet speed conditions. The change of the turbulence kinetic energy, dynamic pressure and turbulence intensity of the micro – holes flow channel with the inlet velocity is discussed. The quality control law of the inlet velocity on the sol-id-liquid two-phase abrasive flow polishing. In order to verify the accuracy of the numerical analysis, the necessary solid-liquid two-phase flow polishing test was carried out with the micro-hole parts. The surface roughness of the inner surface of the micro-holes before and after polishing was tested. The results show that the surface roughness is reduced from 1.702 before polishing to 0.303 after polishing. The solid - liquid two - phase abrasive flow machining can effectively improve the surface quality of micro – holes.

In this paper, forced convection heat transfer nanofluid flow inside the receiver tube of solar parabolic trough collector is numerically simulated. Computational Fluid Dynamics (CFD) simulations are carried out to study the influence of using nanofluid as heat transfer fluid on thermal efficiency of the solar system. The three-dimensional steady, turbulent flow and heat transfer governing equations are solved using Finite Volume Method (FVM) with the SIMPLEC algorithm. The results show that the numerical simulation are in good agreement with the experimental data. Also, the effect of various nanoparticle volume fraction on thermal and hydrodynamic characteristics of the solar parabolic collector is discussed in details. The results indicate that, using of nanofluid instead of base fluid as a working fluid leads to enhanced heat transfer performance. Furthermore, the results reveal that by increasing of the nanoparticle volume fraction, the average Nusselt number increases.

Purpose The purpose of the current research is to study the turbulent flow through microchannels having a micropost in aligned and staggered arrangements. Design/methodology/approach Numerical calculations are performed on the basis of the finite volume approach, which is based on the SIMPLEC algorithm. In this work, the slip velocity, flow velocity distribution and friction factor for the two micropost patterns are examined at friction Reynolds numbers of Reτ = 395 and 590, relative module widths of Wm = 0.1 and 1 and cavity fraction range of Fc = 0.1 to 0.9. Findings Results reveal that for the two micropost patterns, as the friction Reynolds number, relative module width or cavity fraction increases, the slip velocity increases and friction factor decreases. It is found that the aligned micropost configuration leads to higher slip velocity and lower friction factor. Numerical findings indicate that the existence of the continuous cavity surface along the flow direction could be a significant criterion to realize if the velocity distribution deviates from that of the smooth channel. It is also shown that the turbulent flows are capable of producing more drag reduction than the laminar ones. Originality/value Previous studies have shown that microchannels consisting of a micropost pattern in aligned and staggered arrangements could be viewed as a promising alternative in the microscale flows for the heat removal purposes. Therefore, understanding the fluid flow through microchannels consisting of these configurations (which is a prerequisite to better understand thermal performance of such microchannels) is a significant issue, which is the subject of the present work.

This paper investigates numerically the characteristics of subcooled flow boiling of a magnetic nanofluid (refrigerant-113 and 4 vol% Fe3O4) in a vertical annulus, which is exposed to a nonuniform transverse magnetic field generated by the quadrupole magnet. A control volume technique and SIMPLEC algorithm have been used for discretizing the governing equations and pressure-velocity coupling, respectively. The two-fluid model has been used to simulate subcooled flow boiling of the refrigerant-113. The results indicate that subcooled flow boiling characteristics change not only by using nanofluid as the working fluid, but also by applying the nonuniform transverse magnetic field. In the presence of the aforementioned magnetic field due to the Kelvin force, the fluid attracted to the outer wall. This leads to higher bubble detachment frequency so that the heat pumping is increased and the void fraction on the heated wall is decreased. Thus, the critical heat flux as one of the most important parameters in boiling processes will be increased.

In this work, we modify the viscoelastic solver available in the OpenFOAM ® toolbox (Favero et al., 2010), in order to improve its stability for differential-type constitutive equations. The Oldroyd-B constitutive equation is solved using the log-conformation approach and the high-resolution schemes used to discretize the convective terms are handled with a component-wise and deferred correction approach. The pressure-velocity coupling is ensured using the SIMPLEC algorithm, and a new stress-velocity coupling term is also introduced. We demonstrate that the new solver is second-order accurate, both in space and time, by assessing the performance in problems with known analytical solution and using Richardson's extrapolation. The solver is further tested on the 4:1 planar contraction benchmark problem using an Oldroyd-B fluid ( β = 1/9) at low Reynolds number flow conditions ( Re = 0.01), considering a wide range of Deborah numbers, 0 ≤ De ≤ 12. A good agreement with reference works is observed at low De, as well as with an in-house viscoelastic flow solver. At higher De , the vortex dynamics is essentially controlled by the singularity region in the re-entrant corner of the contraction, revealing a significant dependence of the numerical results on the mesh resolution. The corner vortex dynamics is also analyzed, from the flow startup at several De , providing new accurate data on the transient behavior of this problem. In summary, this work provides a robust open-source solver for viscoelastic flows, as well as new data on an old problem, which has still open questions and challenges.

The potential of water power is spread throughout Indonesia. The velocity of river flows in Indonesia is relatively low with an average of 0.6 m/s. With a low water velocity, a vertical axis turbine is used for better efficiency values and maximized blade’s lift by using twisting. In this study using vertical axis helical turbines with overlapping variations. Helical savonius turbine with a 45o twist and 3 blades are designed to improve turbine performance. This study compares the horizontal axis helical savonius river current with variations in the overlap ratio of 0.1, 0.2, 0.3, and 0.4. Validation of turbine design was done by simulation using fluent software to determine numerical analysis and best performance. The simulation was performed on ANSYS 19.2 with standard k-epsilon modeling and SIMPLEC algorithm. From the simulation results obtained overlap ratio 0.1 had the most maximal turbine performance compared to other overlap variations due to the greatest pressure and velocity difference and the greatest coefficient of torque value.

International Transaction Journal of Engineering, Management, & Applied Sciences & Technologies, 10, 7, 903-911

The fractional step method is an efficient time advancement scheme for problems involving transient incompressible flow. The method is desirable over traditional SIMPLE-like algorithms for its non-iterative nature. This paper presents a technique that extends the fractional step method to low-Mach number compressible flow problems. The proposed pressure-velocity coupling and a transient SIMPLEC algorithm are validated and verified for a 1D acoustic wave propagation and a convective isentropic vortex to qualitatively evaluate their convergence properties. Next, both algorithms are used to predict aerodynamic and aeroacoustic behaviour of flow past a wall-mounted side mirror. The proposed scheme is stable at acoustic CFL number greater than one, and at convective Co number equal one. The L2 error norms of both schemes exhibit second order accuracy as grids are refined, while the new scheme requires significantly less computation effort for an equal error. The new fractional step method consumes only 20% to 35% of the computation effort that is required by the transient SIMPLEC algorithm for the same error, and is easily scalable to a greater number of CPU processors.

The mixed convection of a Cu–water nanofluid in a skewed cavity which is slightly inclined from the horizontal is investigated. A co-ordinate transformation is used to transform the physical domain into the computational domain in an orthogonal co-ordinate system. A control volume method over a staggered grid arrangement is used to discretize the governing equations. The discretized equations are solved through a pressure-correction based SIMPLEC algorithm. Based on this algorithm a Fortran 95 computer code is developed, which has been executed in the IBM Power 7 server. The effects of relevant parameters such as, Richardson number ( 0.1 ⩽ Ri ⩽ 5 ) , Reynolds number ( 100 ⩽ Re ⩽ 1000 ) , nanoparticle volume fraction ( 0 ⩽ ϕ ⩽ 0.2 ) on the mixed convection of nanofluid is studied by considering acute to obtuse skew angle and inclination angle between −30° to 30°. We made a comparative study between several models for effective thermal conductivity and viscosity of a nanofluid. The entropy generation as well as the Bejan number is evaluated to illustrate the thermodynamic optimization of the mixed convection. Our results show that the flow and thermal fields within a skewed enclosure are sensible to the angle of inclination. The addition of nanoparticles produce an enhancement in the heat transfer but reduce the effect of buoyancy. The impact of the inclination angle on the heat transfer and entropy generation is analyzed for the considered range of the skew angle to determine the optimum heat transfer characteristics.

Ignition and combustion of an infinite linear array of gaseous fuel pockets in a stagnant oxidizing environment under the microgravity condition is studied by a numerical approach. The combustion process is considered isobaric and the fluid motion is induced by density gradients due to the heat and mass transfer processes. A simple finite chemical reaction mechanism and the ideal gas equation of state are considered. The thermophysical properties, except density, are assumed constant. The Finite Volume Method is used with a hybrid non-staggered grid in a generalized system of coordinates. The SIMPLEC algorithm solves the modified pressure–velocity coupling. The Damkohler number effects on flame dynamics and on the fuel consumption are analyzed. Three stages in the burning processes: the induction time, the flame propagation and the diffusive burning are identified. The merging processes of the fuel pockets and of the flames are depicted.

With the gradual increase of the thermal power unit capacity, the inlet steam parameters and flow of the turbine also increase gradually, which causes considerable secondary flow loss. Therefore, studying the causes and distribution of secondary flow loss within the level is of great significance to effectively improve the stage internal efficiency of turbine. Take high-pressure stage moving blade of a turbine as the research object, and adopt the k-ωSST model, the SIMPLEC algorithm to numerically simulate the formation and development process of leakage vortex between the tip clearance of the positive bending twisted blade and its effect on the secondary flow of cascade passage. Results show that relative to the conventional twisted blade, the scope of influence of leakage vortex which the steam flow formed near the suction surface of positive bending twisted blade and the disturbance to passage mainstream become smaller, and the increase of tip clearance has weakened the „C“ type pressure gradient of suction surface of the positive bending twisted blade, increased the thickness of the boundary layer at both ends of blades and the loss of the blade end.