Oscillatory Reynolds Number Research Articles

Effect of geometrical parameters on fluid mixing in novel mesoscale oscillatory helical baffled designs

The effect of geometrical parameters, including helical pitch and wire diameter, on the fluid mixing inside a novel mesoscale helical baffled design of an oscillatory baffled reactor (OBR) was for the first time experimentally investigated at a net flow rate of 1.72 ml/min (net flow Reynolds numbers Re n of 7.2). The results show that the influence of helical wire diameter on the fluid mixing was negligible at Strouhal numbers above 0.2. However, the degree of plug flow increased 2-fold at oscillatory Reynolds numbers beyond 300 and Strouhal number below 0.2 when the wire diameter increased. The fluid mixing was found to be a function of the ratio of oscillation amplitude to helical pitch. The results showed that plug flow behaviour can be achieved when the ratio of oscillation amplitude to helical pitch was in a range of 0.2–0.6.

Time periodic electroosmotic flow of the generalized Maxwell fluids between two micro-parallel plates

Analytical solutions are presented using method of separation of variables for the time periodic EOF flow of linear viscoelastic fluids between micro-parallel plates. The linear viscoelastic fluids used here are described by the general Maxwell model. The solution involves analytically solving the linearized Poisson–Boltzmann equation, together with the Cauchy momentum equation and the general Maxwell constitutive equation. By numerical computations, the influences of the electrokinetic width K denoting the characteristic scale of half channel width to Debye length, the periodic EOF electric oscillating Reynolds number Re and normalized relaxation time λ 1 ω on velocity profiles and volumetric flow rates are presented. Results show that for prescribed electrokinetic width K, lower oscillating Reynolds number Re and shorter relaxation time λ 1 ω reduces the plug-like EOF velocity profile of Newtonian fluids. For given Reynolds number Re and electrokinetic width K, longer relaxation time λ 1 ω leads to rapid oscillating EOF velocity profiles with increased amplitude. With the increase of the K, the velocity variations are restricted to a very narrow region close to the EDL for small relaxation time. However, with the increase of the relaxation time, the elasticity of the fluid becomes conspicuous and the velocity variations can be expanded to the whole flow field. As far as volume flow rates are concerned, for given electrodynamic width K, larger oscillating Reynolds number Re results in a smaller volume flow rates. For prescribed oscillating Reynolds number Re, with the changes of relaxation time λ 1 ω, volume flow rates will produce some peaks no matter how the electrodynamic width K varies. Moreover, the time periodic evolution of the velocity profiles provides a detail insight of the flow characteristic of this flow configuration.

Response of force behaviors of a spherical particle to an oscillating flow

Combined multi-direct forcing technique and the immersed boundary method is applied to investigate the response of force behaviors of a fixed spherical particle to an oscillating flow. The influences of the inlet oscillating flow at a mean Reynolds number of 300 with six different oscillating frequencies and three oscillating amplitudes are investigated. Three different zones with different behaviors are identified and the specific behaviors of the drag and the lift coefficients are analyzed. The averaged drag coefficient and the maximum lift force exerted on the particle increase with the increment of the oscillating Reynolds number or the oscillating amplitude. When the frequency of the inlet flow is equal to the natural vortex shedding frequency, the average drag coefficient reaches the maximum value. A linear relation between the gradient of the maximum lift coefficient and the frequency as well as the amplitude of the inlet oscillating flow is observed in certain regime.

Time periodic electro-osmotic flow through a microannulus

Flow behavior of time periodic electro-osmosis in a cylindrical microannulus is investigated based on a linearized Poisson–Boltzmann equation and Navier–Stokes equation. An analytical solution of electro-osmotic flow (EOF) velocity distribution as functions of radial distance, periodic time and relevant parameters is derived. By numerical computations, the influences of the electrokinetic width K denoting the characteristic scale of the microannulus to Debye length, the wall zeta potential ratio β denoting the inner cylinder to the outer cylinder, the ratio α denoting of the annular inner radius to outer radius and the periodical EOF electric oscillating Reynolds number Re on velocity profiles are presented. Results show that when electric oscillating Reynolds number is low and the electrokinetic width K is large, the electro-osmotic velocity amplitude shows a square pluglike profile. When the Reynolds number is high, the driving effect of the electric force decreases immediately away from the two cylindrical walls. The parameter β affects the dimension and direction of the EOF velocity profiles within the electric double layer near the two cylindrical walls in a microannulus. Two limiting cases are discussed, i.e., the time periodical EOF approximately in parallel plate microchannel and circular microtube. These results are agreed qualitatively with those obtained by previously related researches. Furthermore, the instantaneous EOF velocity profiles within a period of a time cycle for different applied electric frequency f, electrokinetic width K, and zeta potential ratio β are illustrated.

Bifurcation analysis in a vortex flow generated by an oscillatory magnetic obstacle

A numerical simulation and a theoretical model of the two-dimensional flow produced by the harmonic oscillation of a localized magnetic field (magnetic obstacle) in a quiescent viscous, electrically conducting fluid are presented. Nonuniform Lorentz forces produced by induced currents interacting with the oscillating magnetic field create periodic laminar flow patterns that can be characterized by three parameters: the oscillation Reynolds number, Reomega, the Hartmann number, Ha, and the dimensionless amplitude of the magnetic obstacle oscillation, D. The analysis is restricted to oscillations of small amplitude and Ha=100. The resulting flow patterns are described and interpreted in terms of position and evolution of the critical points of the instantaneous streamlines. It is found that in most of the cycle, the flow is dominated by a pair of counter rotating vortices that switch their direction of rotation twice per cycle. The transformation of the flow field present in the first part of the cycle into the pattern displayed in the second half occurs via the generation of hyperbolic and elliptic critical points. The numerical solution of the flow indicates that for low frequencies (v.e. Reomega=1), two elliptic and two hyperbolic points are generated, while for high frequencies (v.e. Reomega=100), a more complex topology involving four elliptic and two hyperbolic points appear. The bifurcation map for critical points of the instantaneous streamline is obtained numerically and a theoretical model based on a local analysis that predicts most of the qualitative properties calculated numerically is proposed.

Development and evaluation of novel designs of continuous mesoscale oscillatory baffled reactors

Oscillatory baffled reactors (OBRs) are a form of plug flow reactor, ideal for performing long reactions in continuous mode, as the mixing is independent of net flow rate leading to more compact and practical designs. Mesoscale OBRs are currently being developed for laboratory-scale processes. The systems are designed to scale-up to industrial scale directly, or to be used as small-scale production platforms in their own right. Three different meso-reactor baffle designs (integral baffles, helical baffles and axial circular baffles (or “central”) baffles) were developed. These designs were chosen, as they are easily fabricated at “mesoscales” (here typically ∼5 mm diameter) and can be operated at low flow rates (μl/min to ml/min), whereas conventional designs of OBRs cannot. It was found that an increase in the net flow Reynolds number increased the optimum range of oscillatory Reynolds numbers over which plug flow can be achieved. The oscillation conditions had little effect on the residence time distribution behaviour at net flow Reynolds numbers above 25. These designs are effective and robust in scaled-down production of high added value products and decreasing the reagents required.

Average Crossflow Velocity in Laminar Flow Systems with Periodic Finned Surfaces

AbstractExperimental and CFD studies of the enhanced average crossflow velocity in a laminar flow system were performed. The experiments were carried out using working fluid with a kinematic viscosity of 1.8·10–6 m2/s. A steady flow Reynolds number in the laminar range of 0 < Re < 400 and oscillation Reynolds number in the range 0 < Reosc < 1000 were studied. The range of oscillation amplitude and frequency were 0.2 mm < A < 1.0 mm and 5 Hz < f < 90 Hz respectively. Three experimental configurations were studied, i.e., oscillating finned surface in a fluid at rest, which is similar to a batch configuration, steady finned flow and oscillating finned flow configurations. The acquired images were analyzed using particle image velocimetry (PIV) software. The study is also supported by CFD simulations using the software suit CFX 11.0 from ANSYS GmbH, Germany. The results of the flow visualization and PIV analyses reveal the formation of periodic vortices and increased transverse transport. The maximum enhancement of the average crossflow velocity was obtained at κ = 3. The oscillation parameters and shape of the fins have a significant influence on the flow patterns and the crossflow effects. A triangular finned geometry gives better performance considering the enhanced average crossflow velocity. In general, efficient fluid mixing is possible due to the complex flow structures generated.

The Production of Polyhydroxyalkanoates Using an Oscillatory Baffled Bioreactor

Biopolymers are biodegradable polymers made from renewable resources. They can be made from plants or by microorganisms. Pseudomonas putida is one such microorganism. Under nutrient limitation and carbon excess it produces polyhydroxyalkanoates (PHA), which are linear polyesters, to store carbon as energy resource. PHAs are biodegradable and are used in the production of bioplastics.The production of biopolymers from microorganisms is currently not cost effective, because of expensive substrates, low yields and complex downstream processing. Therefore, intensification of PHA production to achieve higher yields in smaller, more efficient equipment at lower capital costs would be an advantage.Oscillatory baffled reactors (OBRs) are a form of plug flow reactor that can be used for long residence time reactions, as the plug flow is not dependent on achievement of a certain net flow velocity in the reactor, leading to much more compact designs. Fermentations, such as the production of PHA by P. putida, show characteristically long residence times. Therefore, they could be intensified in an OBR. Since one major advantage of the OBR is its highly uniform, controllable mixing, which can be used to enhance gas-to-liquid mass transfer, it should be suitable for biological reactions. Fed-batch or continuous fermentation is a second advantage, as it should minimize substrate and product inhibition. Lower, more uniform shear rates than in a stirred tank reactor would be an additional advantage for processing shear-sensitive cells. Previous research has shown that the OBR can provide higher biomass concentrations and greater gas-liquid mass transfer than conventional fermenters. In this work, the production of PHA by P. putida KT2442 was studied. The parameters investigated here were agitation rate and temperature. It was demonstrated that PHA can be produced in the OBR. The fermentation temperature and agitation rate resulting in the highest OD and PHA yield in this parameter space were determined as 30 ± 1°C and an oscillatory Reynolds number (Reo) of 300, respectively. It was also demonstrated that using an OBR can lead to higher OD (10.8 vs 7.26) and dry cell weight (3.75 g/L vs 2.4 g/L) than in a comparable conventional stirred tank reactor.

Droplet combustion in presence of airstream oscillation: Mechanisms of enhancement and hysteresis of burning rate in microgravity at elevated pressure

The enhancement and hysteresis behavior of the burning rate of single droplet combustion in the presence of airstream oscillation observed in previously performed microgravity experiments at elevated pressure up to 1.0 MPa were numerically investigated. Excellent agreement with the experimental results was obtained and the mechanisms of these phenomena were examined based on precise numerical data on instantaneous droplet diameter variations corresponding to the unsteady airstream velocity, flow fields around the droplet, and flame movement during combustion. Results show that, depending on the oscillation Reynolds number, which is a function of pressure, flow amplitude and droplet diameter, there are three mechanisms involved in the enhancement of burning rate. In the cases of low oscillation Reynolds numbers, a diffusion-time-delay has a significant effect on the flame front movement and thus, on heat from the flame to the droplet. In the cases of high oscillation Reynolds numbers, a vortex generated outside the droplet flame promotes the motion of the flame, especially in the wake region, and thus enhancing the droplet burning rate. In addition to these two mechanisms, the forced convection during the acceleration period of the flow oscillation causes overshooting of the droplet burning rate due to instantaneous imbalances of the airflow momentum with the Stefan flow. These three mechanisms explain the predominant role of the highest velocity of the oscillatory airstream in determination of the mean burning rate constant and droplet lifetime. Results also show that the hysteresis behavior of the burning rate is a consequence of the different responses of the flame to the deceleration period compared with the responses to the acceleration period under the existence of those three mechanisms.

Experimental Investigation of the Effects of Fluid Properties and Geometry on Forced Convection in Finned Ducts With Flow Pulsation

An experimental study was conducted on the effects of flow pulsation on the convective heat transfer coefficients in a flat channel with series of regular spaced fins. Glycerol-water mixtures with dynamic viscosities in the range of 0.001–0.01 kg/ms were used as working fluids. The device contains fins fixed to the insulated wall opposite to the flat and smooth heat transfer surface to avoid any heat transfer enhancement by conduction of the fins. Pulsation amplitude xo=0.37 mm and pulsation frequencies f in the range of 10 Hz<f<47 Hz were applied, and a steady-flow Reynolds number in the laminar range of 10<Re<1100 was studied. The heat transfer coefficient was found to increase with increasing Prandtl number Pr at a constant oscillation Reynolds number Reosc. The effect of the dh/L ratio was found to be insignificant for the system with series of fins and flow pulsation due to proper fluid mixing in contrast to a steady finned flow. A decrease in heat transfer intensification was obtained at very low and high flow rates. The heat transfer was concluded to be dynamically controlled by the oscillation.

Vortex formation in a cavity with oscillating walls

The vortex formation in a two-dimensional Cartesian cavity, which their vertical walls move simultaneously with an oscillatory velocity and the horizontal walls are fixed pistons, is studied numerically. The governing equations were solved with a finite element method combined with an operator splitting scheme. We analyzed the behavior of vortical structures occurring inside a cavity with an aspect ratio of height-to-width of 1.5 for three different displacement amplitudes of the vertical oscillatory walls (amplitude/width=Y=0.2, 0.4, and 0.8) and Reynolds numbers based on the cavity width of 50, 500, and 1000. Two vortex formation mechanisms are identified: (a) the shear, oscillatory motion of the moving boundaries coupled with the fixed walls that provide a translational symmetry-breaking effect and (b) the sharp changes in the flow motion when the flow meets the corners of the cavity. The vortex cores were identified using the Jeong–Hussain criterion and it is found that the area occupied by the cores decreases as the Reynolds number increases and increases as Y increases. All flows studied are cyclic symmetric and for low Y and Re values they are also symmetric with respect to the vertical axis dividing the cavity in two sides. In asymmetric flows, the unbalance between the vortices on each side of the midvertical line generates a vortex that occupies the central part of the cavity. The breakdown of the axial symmetry was studied for a fixed value of the oscillation amplitude, Y=0.8, taking Re as the bifurcation parameter. The results indicate that the symmetry is broken through a supercritical pitchfork bifurcation.

Viscoelastic Effects on the Entropy Production in Oscillatory Flow between Parallel Plates with Convective Cooling

The heat transfer problem of a zero-mean oscillatory flow of a Maxwell fluid between infinite parallel plates with boundary conditions of the third kind is considered. With these conditions, the amount of heat entering or leaving the system depends on the external temperature as well as on the convective heat transfer coefficient. The local and global time-averaged entropy production are computed, and the consequences of convective cooling of the plates are also assessed. It is found that the global entropy production is a minimum for certain suitable combination of the physical parameters. For a discrete set of values of the oscillatory Reynolds number, the extracted heat from one of the plates shows maxima.

Experimental study of oscillatory motion of particles and bubbles with applications to Coriolis flow meters

The present experimental study is designed to measure the motion of a spherical particle in a noninertial reference frame when the environment oscillates horizontally at a prescribed frequency and amplitude. Measurements are compared with theoretical equations of motion, for example, Basset [A Treatise on Hydrodynamics (Deighton Hall, London, 1888), Vol. 2], over wide ranges of density ratio (ρf/ρp), inverse Stokes number (δ), and amplitude ratio (Ap/Af), the three most critical nondimensional parameters. The experimental configuration consists of a bubble or solid sphere rising or falling in a bubble column while vibration occurs in the horizontal direction. Motion is measured with a high speed video camera and contemporary image and signal processing techniques are used to evaluate the data. The setup closely resembles multiphase flow in a Coriolis flow meter, a device which measures mass flow rate and density by oscillating two tubes at resonance. Accurate predictions of the motion of the sphere may lead to estimates of measurement errors due to entrained gas or solid particles. Excellent agreement for amplitude and phase shift is found between theory and experiment over the full range of testing, which is defined by small oscillatory Reynolds numbers (Re<2.5), finite Strouhal numbers (5<St<45), widely varying density ratios (0.1<ρf/ρp<700), inverse Stokes numbers (0.5<δ<3.5), and amplitude ratios (0.6<Ap/Af<1.7).

Method of moments for laminar dispersion in an oscillatory flow through curved channels with absorbing walls

The unsteady dispersion of a solute, when the fluid is driven through a curved channel with absorbing walls by an imposed pulsatile pressure gradient, is studied using the method of moments. The study examines the effect of oscillatory Reynolds number, amplitude/frequency of the pressure pulsation and boundary absorption on the longitudinal dispersion. The methodology involves a set of unsteady integral moment equations obtained by applying the Aris-Barton method of moments on the convective-diffusion equation for a curved channel. Central moments are obtained from the moment equations which are solved by a finite-difference implicit scheme. The effect of curvature and boundary absorption on the effective dispersion coefficient from the initial to the stationary stage of the oscillatory flow is studied. Amplitude of the effective dispersion coefficient is found to increase with curvature and decrease with frequency of the pressure pulsation. For large Peclet number and Schmidt number, the amplitude of the dispersion coefficient can be 1.6 times that in a straight channel at large times. Also, for large times, the amplitude of the dispersion coefficient is twice the amplitude of the dispersion coefficient as α, the frequency parameter changes from 0.5 to 1.0. The axial distributions of mean concentration are determined from the first four central moments by using the Hermite polynomial representation. The effect of curvature is to delay the stationary state and also the approach to normality of the concentration distribution. The study has importance in understanding the spreading of pollutants in tidal basins and natural current fields.

Analysis of unsteady forces in ordered arrays of monodisperse spheres

(Received 19 July 2004 and in revised form 12 October 2005) Time-dependent flows of a Newtonian fluid through periodic arrays of spheres were simulated using the lattice-Boltzmann scheme. By applying a constant body force per unit mass to the fluid, a steady background fluid flow through the array of stationary spheres was first established. Subsequently, a small-amplitude perturbation to the body force, which varied periodically in time, was added and the long-time behaviour of the unsteady flow fields and the forces on the particles were determined. From the simulations, the pressure and friction (shear) forces acting on the particles were determined for a range of conditions. Results on simple cubic lattices are presented. Computations spanned a range of particle volume fractions (0.1 <φ< 0.4), background flow Reynolds numbers (0.25 Rep 60, where Rep =2 auf /ν )a nd oscillatory flow Reynolds numbers (0.9 Reω 420 with Reω =2 a 2 ω/ν). Here uf is the superficial velocity of the fluid through the bed, a is the particle radius, ν is the kinematic viscosity of the fluid, and ω is the oscillation frequency. In the limit of Reω → 0 the quasi-steady-state drag force was obtained. At low Rep this force approached the steady-state drag force, while its increase with Rep was stronger than the steady-state drag force, similar to that for isolated spheres given by Mei et al. (J. Fluid Mech., vol. 233, 1991, p. 613). The unsteady force was decomposed into pressure and friction components. The phase angles of these components in the limit Reω →∞ indicate that the virtual mass force contributes to the unsteady pressure force while the history force contributes to the friction force. The remainder of the unsteady friction and pressure forces is attributed to unsteady drag force. The apparent virtual mass coefficient was found to vary from ∼0.5 at high Reω, which is the well-known limit for isolated spheres in inviscid flows, to ∼1. 0a t low Reω. This change is clearly a consequence of viscous effects. The Reω at which the transition between these limits occurs increases with φ. The history force exhibits a strong decay towards lower values of Reω in accordance with the results of Mei et al. (1991) for isolated spheres; however, the Reω value at which this decay sets in increases appreciably with φ .T hisφ-dependence is associated with the limited separation between the particles available for the Stokes boundary layer. It was found that the unsteady drag coefficient β � varies with Reω .A t lowRep ,t he drag coefficient initially decreases with increasing Reω, passes through a minimum and then increases strongly. With increasing Reω the relative contribution of pressure and friction forces to the unsteady drag force changes.

Intensification of inter-phase mass transfer: the combined effect of oscillatory motion and turbulence promoters

This paper presents the results of an investigation into the combined effect of using oscillatory motion and turbulence promoters on the intensification of transfer rate at solid liquid interface. The mass transfer coefficient at oscillating vertical surfaces equipped with rectangular transverse strips was measured for a wide range of oscillatory conditions and promoters configurations using the limiting current technique. It was found that using oscillatory motion it is possible to achieve significant transfer augmentation with relatively small height and low density promoters that could be as low as 1 mm, and 0.04 mm−1, respectively, making it possible to mitigate the adverse effect of the high frictional resistance and power consumption associated with using turbulence promoters for transfer enhancement under non-oscillatory conditions. The results obtained for the average mass transfer coefficient at oscillatory surfaces with turbulent promoters were well correlated in terms of the oscillatory Reynolds number, the Strouhal number, and the ratio of the promoters spacing to its height.

Oscillatory Stokes flow in a cylindrical container

We study the three-dimensional viscous incompressible flow generated in a cylindrical container, of radius R , by the sinusoidally oscillatory motion of the top lid, of frequency Ω . This study generalises the one in Shankar [1997a. Three-dimensional eddy structure in a cylindrical container, J. Fluid Mech. 342, 97–118] where inertial effects were not included. For sufficiently small velocities, the motion will be governed by the linearised Navier–Stokes equation. The solution is constructed as a sum of vector eigenfunctions that satisfy the no-slip conditions on the lateral wall. The eigenvalues are found as the roots of the relation, 4 k 2 J m - 1 ( α ) J m ( k ) J m + 1 ( α ) + k α J m ( α ) ( J m - 1 ( k ) - J m + 1 ( k ) ) ( J m - 1 ( α ) - J m + 1 ( α ) ) - 4 m 2 J m ( k ) J m 2 ( α ) = 0 where m and k are the azimuthal and vertical mode numbers and α = k 2 - i Re with Re being the oscillatory Reynolds number Ω R 2 / ν . J m is the Bessel function of the first kind of order m . For the flow generated by the sinusoidal motion of the lid, only the first non-axisymmetric mode m = 1 is excited. Roots of the above equation with m = 1 are calculated and the coefficients in the finite sum representations for the velocity fields are determined so as to satisfy the no-slip conditions on the top and bottom lids in a least squares sense. Detailed studies for a cylinder depth of 1 and an Re of 10 are made and these reveal interesting streamline patterns that include heteroclinic cycle type structures at the top lid (apart from the usual one at the bottom), saddle and closed stagnation lines, especially when the lid reverses its direction of motion.

An investigation of the effect of viscosity on mixing in an oscillatory baffled column using digital particle image velocimetry and computational fluid dynamics simulation

Abstract In this paper, we examine the effect of viscosity on the performance of the oscillatory baffled column (OBC) using the digital particle image velocimetry (DPIV) technique and computational fluid dynamics (CFD) codes. A selection of Newtonian (1–210 cP) and shear thinning fluids is investigated. The effects of viscosity on mixing are carefully observed by analysing flow patterns generated by both the DPIV and CFD methods. A ratio of the plane-averaged axial over the radial velocity is defined to quantify such the viscosity effects. For the given geometry the velocity ratio approaches to 2 very quickly at increased oscillatory Reynolds numbers, regardless of the Newtonian and non-Newtonian fluids used. An empirical critical ratio of 3.5 is identified, below which the system mixes sufficiently. This would act as the guide for industrial applications where a viscous fluid is mixed in an aqueous solution in the OBC.

348 管路型円すいディフューザの脈動流れ特性 : 広がり角度や振動数の影響(G05-6 流体機械(1),G05 流体工学)

Pulsating turbulent flow in conical diffusers having total divergence angles of 12, 16 and 24°were investigated experimentally. Distributions of the pressure and axial velocity and the power loss were obtained for the pulsating flows at the Womersley numbers α of 10 to 40, the mean Reynolds numbers of Reta =15000〜30000 and the oscillatory Reynolds number of Reos =10000. The power loss of the pulsating flow in the diffusers is larger than that of the steady flow and is highly dependent on the flow rate ratio. A discussion, furthermore, is given for the influences of the divergence angle and the Womersley number on the time-dependent profiles of the phase-averaged velocity and the turbulence intensity.

Effect of oscillatory motion on heat transfer at vertical flat surfaces

The effect of oscillations on heat transfer at vertical surfaces is investigated and a model is developed that predicted both the transient and time average heat transfer rates. The transient behavior of the heat transfer indicates the presence of an oscillatory component superimposed on a larger steady one that does not reach zero during flow reversal. This was explained in terms of the interaction between a “quasi-steady oscillatory” mechanism near the leading edge, and a “pseudo-steady diffusive” far from it. The analysis further revealed that the time average heat transfer rate can be adequately estimated using a mixed “forced-natural” convections correlation, with the forced convection component estimated based on the time average oscillatory Reynolds number Re v = awL/ ν. The agreement between the model predictions and the experimental measurements makes it applicable for predicting heat transfer characteristics and velocity fluctuations near heated vertical surfaces in presence of oscillatory motion. The model is also applicable for predicting heat transfer rates under conditions where oscillatory motion is used to achieve specificity in temperature control without affecting process residence time, such as in biomedical and biochemical applications. The modest heat transfer enhancement (<2) due to oscillatory motion is attributed to the small convective term in the energy equation, which is consistent with previous investigations where increasing the axial temperature gradient in presence of oscillatory motion was shown to achieve much higher heat transfer enhancement.