Sinusoidal Wavy Channel Research Articles

Heat transfer and flow characteristics in a sinusoidally curved converging-diverging channel

The objective of this work is to present the thermal performance characteristics and to examine the hydrodynamic structure of the fluid which improves the rate of heat transfer in parallel with the penalty of pressure drop by means of the time-averaged streamlines topology, <Ψ>, streamwise velocity distribution, <u>, vorticity concentration, <ω> and turbulent Reynolds stress, u'v'‾/U2 for the sinusoidal wavy channel. A wide range of experiments were performed for Reynolds numbers, Re ranging from 4 × 103 to 1 × 104 in order to determine the heat transfer rate and the friction factor, f with varying the channel height expansion/contraction ratio, M = Hmin/Hmax such as 0.5, 0.35 and 0.28. The results revealed that a significant heat transfer enhancement was achieved with a considerable penalty of pressure drop. The highest thermal performance factor, TPF was obtained as 1.46 for M = 0.5. Numerical simulations were conducted to confirm the experimental results for the same parameters. The Shear Stress Transport k-w (SST k-w) turbulence model was used to perform numerical analyses. After ensuring the consistency of experimental thermal performance results with numerical predictions, the Particle image velocimetry (PIV) system was utilized for investigating the flow physics in the sinusoidally curved converging-diverging channel for all M values at Re = 4 × 103 where the TPF is maximum.

Numerical study on heat transfer behavior of wavy channel supercritical CO2 printed circuit heat exchangers with different amplitude and wavelength parameters

Performance enhancement of printed circuit heat exchanger (PCHE) is of great importance to the thermal efficiency improvement of supercritical CO2 Brayton cycle. In this paper, the heat transfer performance and flow characteristics of a sinusoidal wavy channel PCHE are numerically investigated. The effects of the amplitude and wavelength parameters are discussed under different mass flow conditions with inlet Re = 5210.8−13026.9 on the hot side. It’s found that the increase of amplitude and decrease of wavelength result in larger flow length and heat transfer area of the wavy channel, as well as higher heat transfer rate. The use of wavy channel instead of straight channel enhances heat transfer. Because of the complicated flow fields in the wavy channels affected by thermophysical property changes and centrifugal forces, the shapes and locations of high heat flux zones shift with different configurations. The secondary flow and heat transfer area change both contribute to the change of heat transfer characteristics. The resulting complicated heat transfer performance variation of different configurations are illustrated and discussed. Based on the overall performance evaluation results, the best performance is obtained with an amplitude of 3 mm and a wavelength of 50 mm or 75 mm.

Developing predictive models for analysis the heat transfer in sinusoidal wavy channels

In this work, empirical correlations were proposed to accurately estimate the heat transfer and pressure drop for water flow in sinusoidal wavy channels. The artificial intelligence techniques such as artificial neural network (ANN) and genetic algorithm (GA) were applied to develop the correlations. The experimental data related to the Nusselt number (Nu) and pressure drop (ΔP) in the wavy channels with various geometries were collected for the modeling. The independent variables are Reynolds number (Re) and main geometrical parameters including amplitude ratio (b/H), phase shift (φ), and number of waves (Nw). The results indicate that the ANN is a suitable technique to develop correlations for predicting thermal and flow characteristics in heat exchangers with wavy channels.

Effect of sinusoidal-wavy channel of reformer on power of proton exchange membrane fuel cell

The methanol steam reactor (MSR) combined with proton exchange membrane (PEM) fuel cells is regarded as an optimistic miniature power source. The computational fluid dynamics (CFD) simulations are performed to acquire the reforming performance of the MSR with the sinusoidal-wavy channels. The objective of this CFD study is to examine how the wavelength and amplitude of sinusoidal-wavy channel enhance the hydrogen gain and estimated net power of PEM fuel cell under different wall temperatures. The numerical results are also verified by experimental data. The results exhibit that the sinusoidal-wavy channel obviously enhances the reforming performance and the estimated net power of PEM fuel cell since it produces the blockage and trapping effects on the reacting gas to supply more reforming fuel to the catalyst layer and prolong the reacting residence time for enhancing catalytic reaction. In addition, the estimated PEMFC net power and methanol reformation are improved while the wall temperature rises because the higher wall temperature results in the greater catalytic reaction rate.

Heat transfer characteristics of sinusoidal wavy channel with secondary corrugations

Present study deals with three-dimensional numerical investigations on flow and heat transfer characteristics of sinusoidal wavy channel with secondary corrugations. Computations are carried out by using commercial software ANSYS Fluent 17.2 by considering different wave amplitudes and number of waves in streamwise as well as spanwise directions for fixed width and height of the channel. Flow and heat transfer characteristics of secondary corrugated channels are compared with channels having spanwise and streamwise corrugations alone. Flow characteristics are explained with the help of streamline plots. Volume weighted-average values of secondary flow intensity have been shown to demonstrate the strength of secondary flow generated in different corrugated channels. Effect of secondary flow on heat transfer characteristics has been explained with the help of field synergy principle.

A numerical study on bubble dynamics in sinusoidal channels

In the present work, we investigate the dynamics of a bubble, rising inside a vertical sinusoidal wavy channel. We carry out a detailed numerical investigation using a dual grid level set method coupled with a finite volume based discretization of the Navier–Stokes equation. A detailed parametric investigation is carried out to identify the fate of the bubble as a function of Reynolds number, Bond number, and the amplitude of the channel wall and represented as a regime map. At a lower Reynolds number (high viscous force), we find negligible wobbling (path instability) in the dynamics of the bubble rise accompanied only with a change in shape of the bubble. However, at a higher Reynolds number, we observe an increase in the wobbling of the bubble due to the lowered viscous effects. Conversely, at a lower Bond number, we predict a stable rise of the bubble due to higher surface tension force. However, with a gradual increase in the Bond number, we predict a periodic oscillation which further tends to instigate the instability in the dynamics. With a further increase in the Bond number, a significant reduction in instability is found unlike a higher Reynolds number with only change in the shape of the bubble. At lower values of Reynolds numbers, Bond numbers, and channel wall amplitudes, the instability is discernible; however, with an increase in the channel wall amplitude, the bubble retains integrity due to higher surface tension force. At a higher Bond number and channel wall amplitude, a multiple breakup in the form of secondary bubbles is observed. We propose a correlation which manifests the average bubble rise velocity and the fluctuating velocity (due to channel waviness) as a function of Reynolds number, Bond number, and channel wall amplitude. Finally, we conclude that the bubble dynamics pertinent to the offset channels with varying amplitudes does not remain the same as that of the symmetric channel.

Thermal-hydraulic performance evaluation of gas-liquid multiphase flows in a vertical sinusoidal wavy channel in the presence/absence of phase change

Turbulent gas-liquid multiphase flows with and without phase change in a vertical wavy channel are addressed. The multiphase flow field is resolved using the volume of fluid method (VOF), and the flow equations are discretized and numerically solved by the well-known finite volume method. As a multiphase system without mass transfer, air/water flow is considered. It is shown that numerical simulation is well capable of predicting the various multiphase flow regimes ranging from slug to bubbly flows inside wavy channels. Moreover, accurate predictions of overall pressure drop are provided by numerical solutions for various air and water flow rates and the phase shift angle between wavy channel walls. Additionally, condensing flows of refrigerant R134a are simulated inside wavy channels. It is found that for almost all the cases considered in the present study, the convective heat transfer coefficient is higher in wavy channels in respect to straight channels. However, a significant pressure drop penalty is observed especially for high mass fluxes across wavy channels. Therefore, the use of the wavy channels for the enhancement of condensing heat transfer is only advisable for low mass fluxes with the phase shift angle of 180°.

Numerical investigation of γ-AlOOH nano-fluid convection performance in a wavy channel considering various shapes of nanoadditives

In this work, a two-phase mixture approach is utilized to examine the influence of nanoadditive shape on the fluid flow and heat transfer aspects of γ-AlOOH nano-fluid flowing through a sinusoidal wavy channel. The γ-AlOOH (boehmite alumina) nanoadditives of various shapes (i.e. cylindrical, brick, blade, and platelet) are dispersed in 50/50 water-ethylene glycol mixture as the base fluid. The influence of the Reynolds number and nanoadditive volume fraction on the Nusselt number, pressure drop, and performance evaluation criterion (PEC) are numerically studied for different nanoadditive shapes. It is revealed that, among the considered nanoadditive shapes, the platelet shape represents the highest heat transfer performance, while the worst performance belongs to the brick shape nanoadditives. In addition, the findings reveal that for all states, enhancing the Reynolds number intensifies the Nusselt number, pressure drop, and PEC of the γ-AlOOH nano-fluid. Moreover, it is found that boosting the nanoadditive fraction leads to an enhancement in the Nusselt number and PEC of the examined nano-fluids. Furthermore, the pressure drop of all the considered nano-fluids enhances with augmenting the Reynolds number.

Melting and solidification characteristics of a double-pipe latent heat storage system with sinusoidal wavy channels embedded in a porous medium

The aim of this investigation is to explore the combined effects of porous medium and surface waviness on the melting and solidification of PCM inside a vertical double-pipe latent heat storage (LHTES) system. The results are compared with the cases of smooth channels and pure PCM. In the system, water is passed through the inner tube while composite PCM is placed in the annulus side. Different effective parameters including wavelength and wave amplitude of the sinusoidal wavy channels, porosity and pore size of the porous structure, Reynolds number and inlet temperature of water are examined to find the optimum geometric as well as operating conditions in both melting/solidification processes. The results show that utilizing both the high conductive porous structure and wavy channel reduces the melting/solidification times significantly. For the best case, the melting and solidification times of PCM reduce by 91.4% and 96.7%, respectively, compared with the smooth channels pure PCM system. The average rate of transferred heat for the wavy channel composite PCM are 10.4 and 18.9 times that for the smooth channel pure PCM case. Comparing with the pure PCM system, the presence of copper foam reduces the effect of channel waviness significantly for both melting/solidification processes.

Experimental optimization of geometrical parameters on heat transfer and pressure drop inside sinusoidal wavy channels

The response surface methodology (RSM) is firstly employed to investigate the geometric and flow parameters on heat transfer, pressure drop and thermal performance of sinusoidal wavy channels with different phase shifts. The investigated flow and geometric parameters are axial Reynolds number 1106<Rea<2530, wave’s amplitude ratio 0.2<b/H<0.6, phase shift 0∘<φ<180∘ and number of waves 5<Nw<15, respectively. The experiments are carried out by using face central composite design (FCCD). The geometric parameters are optimized and general correlations for pressure drop and Nusselt number inside sinusoidal channels are presented. The influence of each parameter on the heat transfer and pressure drop of sinusoidal wavy channel is also investigated. It is found that the heat transfer to pressure drop ratio is maximum for b/H=0.54, Nw=11, φ/π=0 and the corresponding value of η is 1.21. This optimization gives a lot of freedom to engineers to choose the optimal geometric parameters of plate heat exchangers.

Heat transfer and entropy generation of the nanofluid flow inside sinusoidal wavy channels

Corrugating channel walls is a way to enhance heat transfer in heat exchangers. In the current investigation, the entropy generation minimization approach has been employed to optimize heat transfer and fluid flow within a wavy channel. A numerical method has been built to compute entropy generation rate in a sinusoidal wavy-wall channel with copper-water (Cu-water) nanofluid flow. The governing equations have been discretized using finite volume method for a two-dimensional steady flow. The effects of geometrical and flow parameters, including nanoparticles volume fraction (0.01 < ϕ < 0.05), Richardson number (0.1 < Ri < 10), wave amplitude ratio (0.1 < α < 0.3) and wave length ratio (1 < λ < 3), have been investigated. Results reveal that increasing nanoparticle volume fraction within investigated Richardson number will increase Nusselt number. In addition, the maximum entropy generation rate declines as Richarson number increases. The optimal wave amplitude ratio (corresponding to lowest entropy generation), for wave length ratios of λ = 1 and λ = 2, found to be α = 0.2. Also, for wave length ratio of λ = 3, the minimum entropy generation approximately occurs at α = 0.1.

Thermal performance optimization of a sinusoidal wavy channel with different phase shifts using artificial bee colony algorithm

In this article, heat transfer optimization of forced convection in a wavy channel with different phase shifts between the upper and lower wavy walls is represented. The flow is laminar in the range of (200 ≤ Re ≤ 800) and a uniform temperature of 350 K is considered in the wavy sections. The governing mass, momentum and energy equations are solved using the finite volume method. Different design parameters such as the channel height (h = 10, 15 and 20 mm), the amplitude of the wavy wall (A = 1.5, 2, 2.5 and 3 mm) and the phase shift of the upper wavy wall $$ (0^\circ \le \gamma \le 360^\circ ) $$ are investigated. For optimization process, a recent method, named artificial bee colony (ABC) algorithm, is applied and compared with two other meta-heuristic algorithms, called particle swarm optimization (PSO) and differential evolution (DE). An “in house” code is developed which simultaneously uses the meta-heuristic algorithms and the computational fluid dynamics solver. The results indicate that ABC algorithm has higher accuracy and faster convergence rate than PSO and DE. The parameter considered for optimizing the average Nusselt number as the objective function was the phase shift. But, for optimizing the thermal performance factor, selected parameters were the wavy wall amplitude and the phase shift. The results showed that the maximum average Nusselt number is attained at $$ \gamma = 250.2 $$ , A = 3 mm, h = 10 mm and Re = 800, in which the heat transfer rate has 96.6% enhancement rather than the parallel-plate channel. Also, it is found that $$ \gamma = 283.3 $$ , A = 2.65 mm, h = 10 mm and Re = 800 are the optimized solutions to obtain the maximum thermal performance factor.

Electro-Magnetohydrodynamic Oscillatory Flow of a Dielectric Fluid Through a Porous Medium with Heat Transfer: Brinkman Model

The objective of the present study is to investigate the effect of electro-magnetic field and heat transfer on the oscillatory flow of a dielectric fluid through a Darcy’s Brinkman model in a symmetric flexible sinusoidal wavy channel. The equations which govern the Electro-Magneto hydro dynamic of oscillatory flow for a dielectric fluid are made non-dimensional and coordinate transformation is employed to convert the irregular boundary to a regular boundary. The obtained system of equations is solved analytically by using the regular perturbation method with a small amplitude ratio. Approximate solution for the mean axial velocity, the mean electric potential, the mean temperature, and the mean pressure gradient is obtained. Further, the effect of pertinent parameters is demonstrated and discussed. The phenomena of reflux (the mean flow reversal) are discussed. It is found that the critical reflux pressure is greater for a fluid without an electric field. Also, the increase of magnetic field decreases the flow rate which is helpful to control the blood flow during the surgeries.

Combined effects of corrugated walls and porous inserts on performance improvement in a heat exchanger channel

In this paper, a numerical study is performed to investigate the combined effects of corrugated walls and porous inserts on heat transfer enhancement and thermal-hydraulic performance in a channel. Accordingly, a sinusoidal wavy wall channel partially filled with a porous material placed at its core is considered. The Darcy-Brinkman-Forchheimehr model is considered to study the flow in porous region and finite volume method (FVM) with SIMPLE algorithm are applied to solve the governing equations. It was found that the amplitude of the wavy wall has a considerable effect on average Nusselt number especially at small Darcy numbers. For example, at Re = 300, δ=0.3, α=0.2 and Da=10−2 the average Nusselt number of wavy channel increases about 12% in comparison with the straight one, while it improves about 38% at Da=10−4. Moreover, there is an optimum value of Darcy number corresponding to maximum performance evaluation criteria (PEC). At δ=0.3 and Re=300, for straight channel and wavy channel with α=0.1 the optimum value of Darcy number occurs at Da=10−3, while for α=0.2 and 0.3 the Da=10−4 leads to the maximum PEC.

Numerical modelling of fluid flow and heat transfer in a corrugated channel for heat exchanger applications

In this paper, the heat transfer and flow characteristics for various sinusoidal wavy channels models with different spacing ratio ε = s/2A and waviness parameter γ = 2A/L are numerically investigated using the Finite Element Method (FEM) based Comsol Multiphysics software (vers.5.2). The channel length Lx and wavelength (corrugation pitch) L are maintained constant during simulations. The channel dimensions modified are the width s (at values of 1.5, 2, 2.5 and 3 mm) and the amplitude A (at values of 0.4, 0.65, 0.8 and 1 mm). Results show that corrugated channel models with increased s values at A = 0.65 mm are affected in terms of thermal boundary layer thickness and local Nusselt number amplitude along the lower channel wall. By raising A values with s = 2 mm, the local pressure drop and friction coefficient are clearly influenced also.

Analysis of Entropy Generation in Flow of Methanol-Based Nanofluid in a Sinusoidal Wavy Channel

The entropy generation due to heat transfer and fluid friction in mixed convective peristaltic flow of methanol-Al2O3 nano fluid is examined. Maxwell’s thermal conductivity model is used in analysis. Velocity and temperature profiles are utilized in the computation of the entropy generation number. The effects of involved physical parameters on velocity, temperature, entropy generation number, and Bejan number are discussed and explained graphically.

Numerical investigation of nanofluid turbulent flow in a wavy channel with different wavelengths, amplitudes &amp; phase lag

Two dimensional incompressible turbulent nanofluid flow in a sinusoidal wavy channel is numerically investigated. Finite volume method and Rhie and Chow interpolation in a collocated grid arrangement are used for solving governing equations. The effects of the volume fraction of nanoparticles, Reynolds number, phase lag, frequency and amplitude of the wavy walls on the heat transfer rate are studied. The present work showed good agreement with existing experimental and numerical results. Increasing the frequency and amplitude of the wave and nanoparticles volume fraction has great effect on heat transfer rate.

Heat transfer optimization of two phase modeling of nanofluid in a sinusoidal wavy channel using Artificial Bee Colony technique

The present study represents the heat transfer optimization of two-dimensional incompressible laminar flow of Al2O3-water nanofluids in a duct with uniform temperature corrugated walls. A two phase model is applied to investigate different governing parameters, namely: Reynolds number (100 ≤ Re ≤ 1000), nonofluids volume fraction (0% ≤ ϕ ≤ 5%) and amplitude of the wavy wall (0 ≤ α ≤ 0.04 m). For optimization process, a recent spot-lighted method, called Artificial Bee Colony (ABC) algorithm, is applied, and the results are shown to be in a good accuracy in comparison with another well-known heuristic method, i.e. particle swarm optimization (PSO). The results indicate that the effect of utilizing nanoparticles and increasing Reynolds number is more intensified on growing the average Nusselt number than variations of the amplitude of the wavy wall. To prevent the worst possible heat transfer, the specific amplitude which leads to a minimum average Nusselt number is detected. The effect of using nanoparticles on thermal-hydraulic performance factor (j/f) is presented which considers both heat transfer and hydrodynamics aspects. The results showed that volume fraction has a direct and the wavy wall's amplitude has a converse effect on the thermal-hydraulic performance factor. Furthermore, an optimum value for Reynolds number is found to maximize the thermal-hydraulic performance factor.

The effects of wavy-wall phase shift on thermal-hydraulic performance of Al2O3–water nanofluid flow in sinusoidal-wavy channel

In this paper, laminar forced convection flow of Al2O3–water nanofluid in sinusoidal-wavy channel is numerically studied. The two-dimensional governing equations of continuity, momentum and energy equations in body-fitted coordinates are solved using finite volume method. The sinusoidal-wavy channel with four different phase shifts of 0°, 45°, 90° and 180° are considered in this study. The results of numerical solution are obtained for Reynolds number and nanoparticle volume fractions ranges of 100–800 and 0–5%, respectively. The effect of phase shift, nanoparticle volume fraction and Reynolds number on the streamline and temperature contours, local Nusselt number, local skin friction coefficient, average Nusselt number, non-dimensional pressure drop and thermalhydraulic performance factor have been presented and analyzed. Results indicate that the optimal performance is achieved by 0° phase shift channel over the ranges of Reynolds number and nanoparticles volume fractions.

The Effects of Wavy Plate Phase Shift on Flow and Heat Transfer Characteristics in Corrugated Channel

The heat transfer and flow characteristics in corrugated sinusoidal wavy channels for different phase shift between the upper and lower wavy plates with the same equivalent diameter have been numerically investigated. The computations are performed on uniform wall temperature for air (Pr=0.696) over a range of Reynolds number(Re), 2000≤Re≤10000. The effects of phase shift and Re on flow and heat transfer are discussed. The relative thermalhydraulic performance enhancement is evaluated. Simulation results show that the corrugated channels have a significant heat transfer enhancement accompanied by increased pressure loss penalty, and the effect of phase shift on the flow and heat transfer is more pronounced in higher Re region than in lower Re region. For all channels the goodness factor G decreases with the increasing Re, and the G value is beyond 1 with the exception of the channel of 180°phase shift channel. The optimal performance is achieved on 0° phase shift channel in lower Re region.