Effect Of Prandtl Number Research Articles

Numerical study of MHD effective Prandtl number boundary layer flow of γ Al2O3 nanofluids past a melting surface

This research article numerically studies the influences of an effective Prandtl number along with magnetic field on the melting heat transport characteristics of Ethylene glycol/Water with gamma Al2O3 nanoparticles over a stretching sheet. To analyse the impacts of effective Prandtl number, the non-dimensional melting heat transfer boundary conditions are derived for the first time with and without effective Prandtl number. A non-linear form of thermal radiation is used. The experimental based thermo-physical properties of gamma Al2O3 nanofluids are considered. The electric conductivities of Al2O3, water and ethylene glycol are used to calculate of effective electric conductivity to study the magnetic field effects. Mathematical models are developed and solved by numerical technique based on the Iterative Power Series (IPS) method with shooting strategy. The numerical outcomes are discussed through plots and tables.

MHD free convection flow of power-law nanofluid film along an inclined surface with viscous dissipation and joule heating

Purpose The purpose of this study is to present the magnetohydrodynamic (MHD) flow and heat transfer in an accelerating film of a non-Newtonian pseudo-plastic nanofluid along an inclined surface with viscous dissipation and Joule heating. Design/methodology/approach An incompressible and inelastic fluid is assumed to obey the Ostwald-de-Waele power law model and the action of viscous stresses is confined to the developing momentum boundary layer adjacent to the solid surface. Viscous dissipation and Joule heating on the flow of electrically conducting film in the presence of uniform transverse magnetic field is considered for the Carboxyl Methyl Cellulose (CMC) water-based nanofluid. The fluid is the CMC-water-based with concentration (0.1-0.4 per cent) containing three types of nano-solid particles Cu, Al2O3 and TiO2. The modeled boundary layer conservation equations are transformed to dimensionless, coupled and highly non-linear system of differential equations, and then solved numerically by means of a local non-similarity approach with shooting technique. To validate the numerical results, a comparison of the present results is made with the earlier published results and is found to be in good agreement. Findings The effects of magnetic parameter, Prandtl number, Eckert number and Biot numbers on the velocity and temperature fields are presented graphically and discussed for various values of thermo-physical parameters. It has been found that magnetic field decelerates the fluid velocity for both cases of Newtonian nanofluid and pseudo-plastic nanofluid because of the generated drag-like Lorentz force. This is of great benefit in magnetic materials processing operations, utilizing static transverse uniform magnetic field, as it allows a strong regulation of the flow field. Research limitations/implications The numerical study is valid for two-dimensional, steady, laminar film flow of Ostwald-de-Waele power law non-Newtonian nanofluid along an inclined plate. A uniform transverse magnetic field of strength B0 is applied perpendicular to the wall. Assume that the base fluid and the nano-solid particles are in thermal equilibrium with no slip effects. The interaction of magnetic field with nanofluid has several potential implications and may be used to deal with the problems such as cooling nuclear reactors by liquid sodium and inducting the flow meter which depends on the potential difference in the fluid along the direction perpendicular to the motion and to the magnetic field. Practical implications The study has significant applications in magnetic field control of materials processing systems. Originality/value The results of the present study may be attentiveness to the engineers and applied mathematicians who are interested in hydrodynamics and heat transfer enhancement associated with film flows.

Numerical investigations on serpentine channel for supercritical CO2 recuperator

The Printed Circuit Heat Exchanger (PCHE) in supercritical carbon dioxide (S-CO2) Brayton cycle has a significant effect on the efficiency, compactness and stability of system. To improve the performance of PCHE with serpentine channel, the present work numerically investigated the mechanism of convective heat transfer of S-CO2 in serpentine channel under turbulent condition with inlet Re = 9500–30000, and explored the effects of geometrical parameters on the thermohydraulic performance. The secondary flow motion and the effect of Prandtl number were investigated, and the curvature diameter (D), the camber (C) and the cross-sectional shape were compared and discussed. It was found that high Prandtl number enhances the heat transfer performance significantly near the pseudocritical point, and the secondary flow improves the field synergy and enhances the convective heat transfer in serpentine channel. With smaller curvature diameter or larger camber, the serpentine channel has better overall performance and smaller entransy dissipation-based thermal resistance at relatively low Reynold number, while the thermohydraulic performance becomes worse in the case of relatively high Reynold number due to the considerable flow resistance. Among the numerous cross-sectional shapes, the circle has the best heat transfer performance and the vertical ellipse has the least flow friction.

Effect of Chemical Reaction on Maxwell Nanofluid Slip Flow over a Stretching Sheet

Abstract The main focus of the present study is to analyze the effect of chemical reaction and nonlinear thermal radiation on Maxwell fluid suspended with nanoparticles through a porous medium along horizontal stretching sheet. The governing partial differential equations of the defined problem are reduced into a set of nonlinear ordinary differential equations using adequate similarity transformations. Obtained set of similarity equations are then solved with the help of efficient numerical method fourth fifth order Runge-Kutta-Fehlberg method. The effects of different flow pertinent parameters on the flow fields like velocity, temperature, and concentration are shown in the form of graphs and tables. The detailed analysis of the problem is carried out based on the plotted graphs and tables. It is observed that an increase in the radiation parameter, temperature ratio parameter, Brownian motion parameter and thermophoretic parameter lead to increase in the thermal boundary layer thickness but quite opposite phenomenon can be seen for the effect of Prandtl number.

The influence of the chemical composition representation according to the number of species during mixing in high-pressure turbulent flows

Mixing of several species in high-pressure (high-$p$) turbulent flows is investigated to understand the influence of the number of species on the flow characteristics. Direct numerical simulations are conducted in the temporal mixing layer configuration at approximately the same value of the momentum ratio for all realizations. The simulations are performed with mixtures of two, three, five and seven species to address various compositions at fixed number of species, at three values of initial vorticity-thickness-based Reynolds number, $Re_{0}$, and two values of the free-stream pressure, $p_{0}$, which is supercritical for each species except water. The major species are C7H16, O2 and N2, and the minor species are CO, CO2, H2 and H2O. The extensive database thus obtained allows the study of the influence not only of $Re_{0}$ and $p_{0}$, but also of the initial density ratio and of the initial density difference between streams, $\unicode[STIX]{x0394}\unicode[STIX]{x1D70C}$. The results show that the layer growth is practically insensitive to all of the above parameters; however, global vortical aspects increase with $Re_{0},p_{0}$ and the number of species; nevertheless, at the same $Re_{0},p_{0}$ and density ratio, vorticity aspects are not influenced by the number of species. Species mixing produces strong density gradients which increase with $p_{0}$ and otherwise scale with $\unicode[STIX]{x0394}\unicode[STIX]{x1D70C}$ but, when scaled by $\unicode[STIX]{x0394}\unicode[STIX]{x1D70C}$, are not affected by the number of species. Generalized Korteweg-type equations are developed for a multi-species mixture, and a priori estimates based on the largest density gradient show that the Korteweg stresses, which account for the influence of the density gradient, have negligible contribution in the momentum equation. The species-specific effective Schmidt number, $Sc_{\unicode[STIX]{x1D6FC},\mathit{eff}}$, is computed and it is found that negative values occur for all minor species – particularly for H2 – thus indicating uphill diffusion, while the major species experience only regular diffusion. The probability density function (p.d.f.) of $Sc_{\unicode[STIX]{x1D6FC},\mathit{eff}}$ shows strong variation with $p_{0}$ but weak dependence on the number of species; however, the p.d.f. substantially varies with the identity of the species. In contrast, the p.d.f. of the effective Prandtl number indicates dependence on both $p_{0}$ and the number of species. Similar to $Sc_{\unicode[STIX]{x1D6FC},\mathit{eff}}$, the species-specific effective Lewis-number p.d.f. depends on the species, and for all species the mean is smaller than unity, thus invalidating one of the most popular assumptions in combustion modelling. Simplifying the mixture composition by reducing the number of minor species does not affect the crucial species–temperature relationship of the major species that, for accuracy, must be retained in combustion simulations, but this relationship is affected for the minor species and in regions of uphill diffusion, indicating that the reduction is nonlinear in nature.

Thermodynamic Analysis of Entropy Generation Minimization in Thermally Dissipating Flow Over a Thin Needle Moving in a Parallel Free Stream of Two Newtonian Fluids.

This article is devoted to study sustainability of entropy generation in an incompressible thermal flow of Newtonian fluids over a thin needle that is moving in a parallel stream. Two types of Newtonian fluids (water and air) are considered in this work. The energy dissipation term is included in the energy equation. Here, it is presumed that u∞ (the free stream velocity) is in the positive axial direction (x-axis) and the motion of the thin needle is in the opposite or similar direction as the free stream velocity. The reduced self-similar governing equations are solved numerically with the aid of the shooting technique with the fourth-order-Runge-Kutta method. Using similarity transformations, it is possible to obtain the expression for dimensionless form of the volumetric entropy generation rate and the Bejan number. The effects of Prandtl number, Eckert number and dimensionless temperature parameter are discussed graphically in details for water and air taken as Newtonian fluids.

Numerical computations on flow and heat transfer of Casson fluid due to oscillatory moving surface

A numerical study of unsteady hydromagnetic flow of Casson liquid passed through the oscillatory moving surface is presented. The interaction of radiation term is reported in the energy equation. The flow is generated by the rapid move?ment of elastic surface that stretched back and forth periodically. The number of variables is reduced by introducing dimensionless variables. An implicit technique developed on finite difference algorithm is implemented to the system of PDE. The impact of various parameters like Casson liquid parameter, the oscillation frequency and stretching rate ratio, Hartmann number and effective Prandtl number are shown through various graphs. The observation indicates that the amplitude of the velocity declines by enhancing Casson liquid parameter, oscillation frequency and stretching rate ratio and Hartmann number. The temperature declines by increasing Casson fluid parameter and effective Prandtl number. The results also indicate that the time-series of local Nusselt number increases by enhancing effective Prandtl number.

The Effect of Prandtl Number on Thermal Flow of Natural Convection in Horizontal Vessel with Free Surface

The Effect of Prandtl Number on Thermal Flow of Natural Convection in Horizontal Vessel with Free Surface

DNS Study on Effect of Prandtl Number for Turbulent Boundary Layer with various External Forces

DNS Study on Effect of Prandtl Number for Turbulent Boundary Layer with various External Forces

Numerical Assessment of Prandtl Number Effect on Transient Heat Flux Distribution Imposed on Nuclear Reactor Pressure Vessel by Application of PECM in a Volumetrically Heated Molten Pool

Short Retraction Notice There are some errors in the discussion and conclusion part. This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. Aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

Effective Prandtl Aspects on Bio-Convective Thermally Developed Magnetized Tangent Hyperbolic Nanoliquid With Gyrotactic Microorganisms and Second Order Velocity Slip

The current article depicts the impact of the effective Prandtl number on thermally developed flow of magnetized tangent hyperbolic fluid containing nanoparticles over a porous surface with shear rate viscosity. Zero normal mass flux condition for nano particles is used with second order slip features. In order to prop the suspended nanoparticles by associate effect of buoyancy force and magnetic field is implemented. Bio-convective effect with Nield boundaries due to gyrotactic motile microorganisms is the concerned factor of current communication. The implemented appropriate transformation function is used to transform the system of self-determining partial differential equations (PDEs) into the sets of non-linear ordinary differential equations (ODEs). These transmuted expression computed numerically by bvp4c function on MATLAB using mathematical scheme shooting technique. Furthermore, the interesting phenomena of controlling parameters, is inspected on velocity profile, temperature distribution, concentration profile of nano particles and motile microorganisms by using graphical and numerical techniques. The first order and the second order slip parameters decay the momentum boundry layer, and boosted up the velocity profile as enhance in the value of mixed convection parameter. It is deduced that the Peclet number and the bio-convection Lewis number results delay in the density of the motile microorganism. For the efficient of the thermal field, the bioconvection is induced by the gyrotactic microorganisms to stabilized the nanoparticles.

Hydrothermal analysis of Non-Newtonian second grade fluid flow on radiative stretching cylinder with Soret and Dufour effects

The present paper examines the analytical approach of a second grade fluid flow along a stretching cylinder and the Soret and Dufour effects is also investigated on the problem. The flow is subjected to thermal radiation. A system of non-linear equations has been extracted using the mathematical modeling of a second grade fluid flow in a cylindrical coordinate system. Homotopy analysis method (HAM) was implemented to solve this problem which an excellent agreement between this method and the numerical approach was observed in the results. The effect of the following physical parameters on the velocity, temperature and concentration profiles has been investigated in this paper; viscoelastic parameter (We), curvature parameter γ, Dufour parameter (Du), Soret parameter (Sr), temperature exponent (n), effective Prandtl number Preff and Schmidt number (Sc), etc. moreover, the drag coefficient on surface along with heat and mass transfer rate are also investigated and presented in various tables. For instance, it is predicted that Simultaneous variations of Du and Sr has an inverse relation for heat and mass transfer rate. In this case increasing Du and decreasing Sr would cause a decrease in heat transfer rate along with an increase in mass transfer rate.

Integral properties of temperature variance production in a turbulent channel flow with passive scalar transport

This paper investigates the integral properties of the mean temperature dissipation α(∂Θ/∂y)2 and the temperature variance production Pθ=Rvθ(∂Θ/∂y) in fully developed turbulent channel flow, and in particular the effects of Prandtl number Pr=ν/α and Reynolds number Reτ=δuτ/ν (and/or Peclet number Peτ=ReτPr). Here Θ is the mean temperature and Rvθ is the wall-normal turbulent heat flux. y is the wall-normal direction and δ is the channel half-height. ν and α are the fluid viscosity and thermal diffusivity, respectively. uτ is the friction velocity. The main findings of the present work include: (1) Identities are derived from the mean thermal energy equation for the global integral of the mean temperature dissipation and temperature variance production for four heating conditions: constant heat source (CHS), constant wall heat flux (CHF), constant temperature difference (CTD), and constant wall temperature (CTD). Identities for the CHS and CHF conditions are consistent with those derived by Pirozzoli et al. (2016) and Abe and Antonia (2017). The identities are verified using publicly available direct numerical simulation (DNS) data under three heating conditions CHS, CHF, and CTD. (2) The global integral of the mean temperature dissipation is found to depend strongly on the fluid Prandtl number, but it is largely independent of the Reynolds number of the flow. In inner-scaling, this global integral can be approximated as(1/Pr)∫0δ+(∂Θ+/∂y+)2dy+≈9.13Pr1-n where Θ+=Θ/θτ is the inner-scaled mean temperature and θτ is the friction temperature. y+=yuτ/ν is the inner-scaled wall-normal distance. n≈1/2 for Pr≲1 and n≈1/3 for Pr≳1. The strong dependence of (1/Pr)∫0δ+(∂Θ+/∂y+)2dy+ on the Prandtl number is directly rooted in the molecular thermal diffusion sub-layer. (3) The global integral of temperature variance production is found to strongly depend on both Prandtl number and Reynolds number. (3.1) At sufficiently high Reynolds number and Peclet number, the integral of temperature variance production is found to exhibit a logarithmic-like layer similar to that of the mean temperature profile. (3.2) The effect of Prandtl number is mainly caused by the molecular thermal diffusion sub-layer and buffer layer. (3.3) Between the peak wall-normal turbulent heat flux Rvθ location, ymt, and the channel centerline, δ, the integral of temperature variance production increases with Peclet number in a logarithmic-like fashion. (3.4) At low Prandtl number Pr≲1, the integral of temperature variance production is found to be equally partitioned around ymt.

Numerical investigation of flow and combined natural-forced convection from an isothermal square cylinder in cross flow

Unsteady flow and heat transfer from a horizontal isothermal square cylinder is studied numerically using a three-dimensional computational model to investigate the influence of buoyancy on the forced flow and heat transfer characteristics. The numerical model is based on a horizontal square cylinder subjected to laminar fluid flow in an unconfined channel. The governing equations in 3D form are solved using a fractional step method based on the finite difference discretization in addition to a Crank–Nicholson scheme employed to the convective and the viscous terms. Two working fluids–air (Pr = 0.7) and water (Pr = 7)–are considered, and the flow and heat transfer simulations were carried out for the Reynolds and Richardson numbers in the intervals 55 ≤ Re ≤ 250 and 0 ≤ Ri ≤ 2, respectively. The flow characteristics such as time-averaged drag/lift, rms drag/rms lift coefficients as well as Strouhal number were computed. The heat transfer from the cylinder is assessed by mean Nusselt number (and rms Nusselt number) over the total heated cylinder walls. As the buoyancy increases, the mass and the velocity of the fluid flowing underneath the cylinder increases. The fluid is injected into the near wake region with an upward motion which significantly alters the flow field in the downstream as well as upstream regions. The effects of Reynolds, Richardson and Prandtl numbers on the flow field and temperature distributions are discussed in detail. It is shown that the flow and heat transfer characteristics are influenced more for air than water. To fill the void in the literature, useful empirical correlations of practical importance are derived for pure forced and pure natural as well as mixed convection. The mixed convection correlations, in terms of the ratio of pure forced convection, are also developed, and their implications are discussed.

Investigation on Instability of Rayleigh-Benard Convection Using Lattice Boltzmann Method with a Modified Boundary Condition

In this study, the effects of Prandtl number on the primary and secondary instability of the Rayleigh-Benard convection problem has been investigated using the lattice Boltzmann method. Two different cases as Pr=5.8 and 0.7 representing the fluid in liquid and gas conditions are examined. A body forces scheme of the lattice Boltzmann method was presented. Two types of boundary conditions in the presence of body forces are analyzed by the moment method and applied to a Poiseuille flow. Characteristic velocity was set in such a way that the compressibility effects are negligible. The calculations show that the increment of Prandtl number from 0.7 to 5.8 causes to create a secondary instability and onset of the oscillation in the flow field. Results show that at Pr=5.8, when the Rayleigh number is increased, a periodic solution appeared at Ra=48,000. It is observed that the dimensionless frequency ratio for Ra= 105 with Pr=5.8 is around 0.0065. The maximum Nusselt number for Ra = 105 with Pr=5.8 are estimated to be 5.4942.

Effective Prandtl Number Model Influences on the $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ γ Al 2 O 3 – $${\hbox {H}}_2 {\hbox {O}}$$ H 2 O and $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ γ Al 2 O 3 – $${\hbox {C}}_2 {\hbox {H}}_6 {\hbox {O}}_2 $$ C 2 H 6 O 2 Nanofluids Spray Along a Stretching Cylinder

The flow of common fluids (water, oils and ethylene glycol etc.) is diluted by adding different small particles of metals, and their oxides are more powerful to reduce the scientific issues related to quicker heat transfer. According to this indication, we have contemplated finite film of $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {H}}_2 {\hbox {O}}$$ and $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {C}}_2 {\hbox {H}}_6 {\hbox {O}}_2 $$ nanoliquid sprayed on an extending cylinder. In this scenario, uniform magnetic field $$B_0$$ and constant reference temperature are employed on the stream of thin film nanofluid. The impact of effective Prandtl number, viscosity and thermal conductivity is derived from the experimental data (Sheikhzadeh et al. in J Appl Fluid Mech 10:209–219, 2017; Lee et al. in J Heat transf 121:280–289, 1992; Wang et al. in J Thermo Phys Heat Transf 13:474–480, 1999; Hamilton and Crosser in Ind Eng Chem Fundam 1:187–191, 1962; Maiga et al. in Super Lattices Microstruct 35:543–55, 2004; Hayat et al. in J Mol Liq. https://doi.org/10.1016/j.molliq.2018.06.029 , 2018). The model problem is excellently converted into a set of proper self-comparable forms with the assistance of possible transformations. Analytical results of velocity and thermal profile are computed using homotopy analysis method for both $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {H}}_2 {\hbox {O}}$$ and $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {C}}_2 {\hbox {H}}_6 {\hbox {O}}_2 $$ nanoliquid. Furthermore, during coating analysis, rate of spray, pressure distribution, skin friction coefficient (surface drag force) $$C_{\mathrm{f}} $$ and Nusselt number (the rate of heat transfer) Nu for both nanofluids are also intended. The impact of additional ingrained quantities like magnetic parameter M, volume fraction of nanoparticles $$\varphi $$ , Grashof number Gr, fluid thickness parameter $$\beta $$ , Prandtl number Pr and Reynolds number Re is portrayed numerically and graphically for both alumina particles. The key observation indicates that the temperature of $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {C}}_2 {\hbox {H}}_6 {\hbox {O}}_2$$ nanoliquid leading on $$\gamma {\hbox {Al}}_2 {\hbox {O}}_3$$ – $${\hbox {H}}_2 {\hbox {O}}$$ nanoliquid during the study. Due to greater viscosity and thermal conductivity, $${\hbox {C}}_2 {\hbox {H}}_6 {\hbox {O}}_2$$ -based nanofluid is observed as upgraded common base fluid assimilated to $${\hbox {H}}_2$$ O.

Effect of Prandtl number on thermo-fluidic transport characteristics for mixed convection past a sphere

In this paper, we numerically investigate the influence of Prandtl number on the thermo-fluidic transport characteristics for steady laminar mixed convection from a sphere in an assisting flow configuration. The stream function-vorticity formulation with a higher order finite difference compact scheme in spherical polar coordinates has been used to solve the governing transport equation of motion and thermal energy. The fluid flow and heat transfer characteristics are presented in terms of streamline and isotherm contours in close proximity to the sphere together with local Nusselt number along the sphere surface and average Nusselt number for the Reynolds number in the range 5 ≤ Re ≤ 200, Richardson number in the range 0 ≤ Ri ≤ 1.5 and Prandtl number ranging from 0.72 to 40. Critical Richardson number has been identified for different values of Reynolds number and Prandtl number, signifying the strength of the force of streamwise acceleration due to the buoyancy and externally imposed flow field relative to the combined viscous resistance and pressure force, for which the flow separation phenomenon occurring in the downstream region of the sphere gets suppressed. It reveals that for lower values of Reynolds number, the average Nusselt number monotonically increases with Richardson number for any particular value of Prandtl number. At higher values of Reynolds number, contrasting features have been observed. For lower values of Prandtl number, the average Nusselt number increases monotonically with Richardson number, while for higher values of Prandtl number the variation is non-monotonous.

Numerical Simulation of Oscillatory MHD Natural Convection in Cylindrical Annulus: Prandtl Number Effect

The oscillatory natural convection between two concentric cylinders is numerically investigated. The effect of Prandtl number on flow and heat transfer characteristics with considering the magnetic field effects is investigated. For different values of physical parameters, critical Rayleigh numbers are determined. For buoyancy term, the Boussinesq approximation is used, and the numerical solutions are obtained using the finite volume method. For this kind of Prandtl number, the flow and heat transfer characteristics are unique and independent of the Prandtl number. Stability diagram (RaCr-Pr) highlights the dependence of RaCr via Prandtl numbers and various Hartmann number. The importance of this modeling is its practical application for stabilizing or weakening the convective effects in the design of magnetic systems.

3D flow of Carreau polymer fluid over variable thickness sheet in a suspension of microorganisms with Cattaneo-Christov heat flux

Numerical study of three dimensional Carreau liquid flow with heat and mass transport features over a variable thickness sheet filled with microorganisms is analyzed. We considered the non-uniform heat sink or source and multiple slip effects. The governing non-linear partially differential expressions are developed into ordinary differential systems by using variable transformations. These expressions are solved numerically by using Runge-Kutta fourth order method connected with shooting methodology. A Parametric study is implemented to demonstrate the effects of Hartmann number, Prandtl number, Weissenberg number, Peclet number, chemical reaction and heat sink/source parameters on liquid velocity, temperature and concentration profiles. The quantities of physical interest are described within the boundary layer. From this analysis, we found that the magnetic parameter decrease the local Sherwood and local Nusselt numbers for both and cases. The constraint of chemical reaction enhances the mass transfer rate and decelerates the density of motile mass transfer rate. The space dependent and temperature dependent heat source/sink suppress the local Nusselt number.

Effect of fin types and Prandtl number on performance of plate-fin heat exchanger: Experimental and numerical assessment

An experimental investigation is performed using liquid R113 to study the thermohydraulic characteristics of plate-fin heat exchanger with plain, serrated and perforated fins. Meanwhile, three performance evaluation criteria j/f, j/f1/2 and j/f1/3 are used to qualitative compare their comprehensive performance. Further, to study the effects of heating condition and Prandtl number on heat transfer, a numerical model of serrated fins is carried out. The fin channels with a uniform heat flux at bottom end or at both bottom and upper ends are studied as two types of heating conditions, namely, single-fold and two-fold modes. Besides, using air (Pr = 0.744), R113 (Pr = 9.02) and ethylene glycol (Pr = 51.65) aqueous solution as working media, the Prandtl number effect is discussed. The results reveal that the comprehensive performance of serrated fins is the best. Colburn factor j of single-fold mode is lower than that of two-fold mode. The Colburn factor j decreases as the Prandtl number increases in laminar flow and it is independent of Prandtl number in turbulent flow. A modified Colburn factor j based on the Manglik & Bergles correlation is proposed as functions of (Pr/Prair)−0.04827 in laminar flow. The conclusions provide the guidance on the design of plate fin heat exchanger.