Kourosh Javaherdeh - Academia.edu (original) (raw)

Papers by Kourosh Javaherdeh

Journal of Thermal Analysis and Calorimetry

In this study, the flow pattern and heat transfer enhancement of a non-Newtonian nanofluid in the... more In this study, the flow pattern and heat transfer enhancement of a non-Newtonian nanofluid in the presence of fins in a corrugated channel were numerically investigated. The fluid flow is in the hydraulically laminar regime, and the channel is under a constant heat flux. A set of case studies are conducted for the flow through the corrugated channel to analyze the effect of the main contributing factors; Reynolds number, the number of corrugation, the height of fin, the arrangement of fins (Cases A, B, and C), and the nanofluid volume fraction, on the flow field and the heat transfer characteristics as well. Comparing the results of the finned cases with different cases (without fins) indicates that implementing fins leads to a considerable change in the flow and temperature fields, resulting in the enhancement of heat transfer. Furthermore, results showed that using two corrugations in the channel provides a better heat transfer rate than other corrugation numbers. The results indicate that increasing the height of fins from 5 to 10 mm, changes the flow pattern and velocity distribution in the vicinity of the fins, and the maximum velocity occurs right on the head of the fins. Moreover, the results show that by increasing the height of fins, the pressure drop increases in the vicinity of fins. The bulk temperature in the vicinity of the corrugations is higher than in other regions, and by increasing the height of fins, the maximum bulk temperature decreases in these regions. Besides, increasing the nanofluid volume fraction and Reynolds number increases the local and mean Nusselt numbers. Moreover, it was found that the maximum value of Num_fin/Num\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{\text{Nu}}_{{{\text{m}}\_{\text{fin}}}} } \mathord{\left/ {\vphantom {{{\text{Nu}}_{{{\text{m}}\_{\text{fin}}}} } {{\text{Nu}}_{{\text{m}}} }}} \right. \kern-\nulldelimiterspace} {{\text{Nu}}_{{\text{m}}} }}$$\end{document}, at the highest Reynolds number (Re = 1000) occurs for case B with a fin height of Z = 7.5 mm. The results show that by optimizing the arrangement of fins, the mean Nusselt number can be improved 25.7 and 49.7%, compared to rectangular channel and smooth channel, respectively.

Journal of Thermal Engineering, 2022

2022ABSTRACTPorous materials are used in thermal devices such as heat exchangers to improvement t... more 2022ABSTRACTPorous materials are used in thermal devices such as heat exchangers to improvement the heat transfer. The heat transfer of a non-Newtonian fluid flow in an annular pipe with porous discs is numerically investigated in this paper. The flow regime in both porous medium and clear region are considered to be turbulent. The effects of power-law index of the non-Newtonian fluid and porous discs pitch variationson the heat transfer rate, friction coefficient are studied and compared to each other for two porous layer thicknesses. Finally, the thermal performance is defined which determines the optimum porous media and non-Newtonian fluid characteristics in the annular pipe.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022

2019 Iranian Conference on Renewable Energy & Distributed Generation (ICREDG), 2019

Dynamic Tidal Power (DTP) is one of the most recent methods of exploiting the energy of tides. Al... more Dynamic Tidal Power (DTP) is one of the most recent methods of exploiting the energy of tides. Although most of the studies regarding this revolutionary method aim at the Yellow and Bohai seas in China, the evaluation of this method in other potential locations in the world is of considerable importance. This study provides preliminary insights and assessments about the use of this method in Faror strait in the Persian Gulf. By using a 3D numerical model of a full-scale domain, the maximum water level difference between the two sides of the DTP dam is found to be about 1.2 meters at the maximum water speed in the strait with a total available power of 760 MW. Furthermore, among the existing technologies for electric generators, a direct-drive permanent magnet synchronous generator has proved to be the best choice for the electric power generation system. Moreover, it has been concluded that power electronic converters are required to make the generated voltage compatible with the grid voltage.

In this paper, the unknown heat flux is estimated with Davidon-Fletcher-Powell (DFP), Broydon–Fle... more In this paper, the unknown heat flux is estimated with Davidon-Fletcher-Powell (DFP), Broydon–Fletcher–Goldfarb–Shanno (BFGS) and Symmetric Rank-one (SR1) version of variable metric method (VMM). The numerical techniques used in this study solved the inverse problems with various boundary and environmental conditions very efficiently. The results shows the sensitivity of measurement errors and different parameter including changes of slope and angle which can be functions of an unknown parameter. Further, the speed of convergence is assessed and the convergence behavior is found. The accuracy of results show that this study is a powerful reference for comparing results obtained based on the three proposed techniques. The solution procedure introduced a general cheap and fast method which can be used for the inverse heat conduction problem in rocket nuzzle and same heat conduction, radiation and convection problems.

International Journal of Thermal Sciences, 2022

This paper focuses on evaluating the effects of flow rate and temperature changes of hot and cold... more This paper focuses on evaluating the effects of flow rate and temperature changes of hot and cold fluid flows in multistream multi-fluid plate-fin heat exchangers with a single-component two-phase flow in the middle heat exchanger. This three-fluid heat exchanger included three layers with offset strip and wavy fin configurations. In the adjacent heat exchanger with offset strip fins, hot and cold fluids were flowing, while the middle heat exchanger with wavy fins contained a single-component two-phase flow (condensed vapor). The Nusselt number, friction factor, the thermal performance factor, and the heat transfer surface contribution of the middle heat exchanger with each of the adjacent heat exchangers, were obtained using the measured experimental data. The results indicate that the two-phase Reynolds number was between 500 and 1800, and the vapor quality varied in the range of 0.17-0.56. Also, the heat transfer surface contribution of the adjacent cold and hot fluids was between 0.18 and 0.5. The two-phase flow in the wavy channel has a wavy and stratified pattern. The examinations showed that raising the Reynolds number of hot and cold fluids, respectively, led to maximum 13.8 % and 9.5 % of reduction in the vapor quality, 8.8 % and 9 % of increase in the two-phase Nusselt number, and 18 % and 12 % of reduction in the average value of friction factor. The domain change in the two-phase vapor quality, the twophase fluid heat transfer surface contribution, and the flow pattern determination parameters including the dimensionless mass parameter and the Lockhart-Martinelli parameter was 33.67 %, 80.81 %, 32.72 %, and 19.09 %, respectively. As the Reynolds number of the cold fluid was changed, the variation domain of these parameters was higher compared to when the Reynolds number of the hot fluid was altered. Increasing the dimensionless temperature of the hot and cold raised the vapor quality by 12-16 %. The experimental results revealed that by decreasing the temperature of adjacent fluids and increasing their Reynolds number, the thermal performance factor of the two-phase flow was increased.

Scientia Iranica, 2019

In the present study, a novel Trombe wall-assisted desiccant wheel system is modeled, in which th... more In the present study, a novel Trombe wall-assisted desiccant wheel system is modeled, in which the trombe wall is divided into three equal parts and provides the heat required for regeneration of the desiccant wheel. Separate mathematical models have been proposed for di erent components of the system such as desiccant wheel and Trombe wall. The mathematical models of di erent parts have been assembled. E ects of the geometrical parameters of the Trombe wall on the regeneration temperature of the desiccant wheel have been investigated based on the integrated model. The results of the present study for some special cases have been compared with results available in open literature. The optimal surface area of the Trombe wall has been extracted according to the parameters of the desiccant wheel. Results show that the solar energy received by the Trombe wall is 600-740 W/m 2 (1 May-15 August) in the warm and humid climate of Gilan (Iran), the temperature of the wall surface is obtained 77-86 C, and the outlet temperature of regeneration air stream from Trombe wall is obtained 60-70 C; however, the output humidity of the desiccant wheel is reduced from 23 gw/kga to 10-12 gw/kga in the studied region (Gilan, Iran).

Physica A: Statistical Mechanics and its Applications, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Mechanical Science and Technology, 2017

The forced convection steady heat transfer under laminar flow regime in a horizontal annular tube... more The forced convection steady heat transfer under laminar flow regime in a horizontal annular tube was experimentally investigated in this paper using a non-newtonian, pseudo-plastic nanofluid with an aqueous carboxymethyl cellulose (CMC-0.2 % wt) as the base fluid, and copper oxide (CuO) nanoparticles in 0.5 % wt, 1.0 % wt and 1.5 % volume fractions and Reynolds number from 460 to 1280 and different range of heat flux. The mean and local heat transfer coefficients of the nanofluid were recorded higher than the base fluid at all the applied Reynolds numbers. For instance, at Re = 460, for the nanofluid of 0.5 % vol. concentration, heat transfer coefficient was improved by 14.7 % compared to the base fluid, and by increasing nanofluid concentration to two/three times, heat transfer was improved by 4.4 % and 5.2 %, respectively. The maximum mean heat transfer coefficient was observed for the 1.5 % nanofluid at Re = 1280.

Heat and Mass Transfer, 2018

In present paper the effects of using typical twisted tape (TT) and V-cut twisted tape (VTT) on N... more In present paper the effects of using typical twisted tape (TT) and V-cut twisted tape (VTT) on Nusselt number (Nu), friction factor (f) and thermal performance factor (η) inside corrugated tube in the turbulent flow are experimentally investigated despite the fact that the wall is under uniform heat flux. The experiments are conducted by twisted tapes with different twist ratio (y = 4.5, 6.07), depth and width ratios ranging (0.285-0.5) and Reynolds number varied from 5300 to 25,700 and water was as a working fluid. The obtained results show that the Nusselt number for corrugated tube that equipped with twisted tapes increases with increasing Reynolds number and is remarkable at high Reynolds Number while the friction factor is low. Moreover, the thermal performance factor for fluid increases with increasing Reynolds number and also the thermal performance factor for all states of VTT are higher than of TT. The new empirical correlations for Nusselt number, friction factor and thermal performance factor are predicted and compared with experimental data.

International Journal of Modern Physics C, 2017

The aim of this paper is investigating the forced convection heat transfer in a channel with tran... more The aim of this paper is investigating the forced convection heat transfer in a channel with transverse rectangular cavities using the lattice Boltzmann method (LBM) which is not available in the literature yet. The effects of the Reynolds number (100–400), cavity aspect ratio ([Formula: see text], 0.5, 1.0), distance of cavities from each other ([Formula: see text]) in fixed depth of cavity ([Formula: see text]) on the velocity and temperature profiles are studied. Moreover, the flow patterns such as deflection and re-circulation zone inside the cavities are obtained. The local and averaged Nusselt numbers on the channel walls are achieved. The results show that the channel with cavities achieves heat transfer enhancements relative to the smooth channel. For the constant cavity aspect ratio, the maximum value of averaged Nusselt number in the channel is obtained in the case of [Formula: see text]. Heat transfer to the working fluids increases significantly by increasing the aspect ...

Journal of Thermal Science and Engineering Applications, 2017

The effects of geometrical arrangement on the heat transfer and pressure drop characteristics in ... more The effects of geometrical arrangement on the heat transfer and pressure drop characteristics in compact louvered fin-and-tube heat exchangers were studied experimentally and numerically along with ε−NTU method. Different geometrical parameters including louver angle, louver pitch, louver number, the nonlouvered inlet and exit fin length, and redirection of fluid flow are considered to determine their effects on the flow field. The study is performed for different louver angles varying from θL=12 to 60 deg, and optimal heat transfer rate is obtained at louver angle of θL=28deg. Also, it is found that increasing the louver number, NL, on the fin surface enhances the heat transfer performance. It is shown that the average Nusselt number is increased as the louver pitch is decreased and its optimum value is obtained at Lp=0.9 mm. However, comparing to the effect of louver number, the louver pitch has a small effect on the performance of the heat exchanger. Additionally, the optimum val...

Case Studies in Thermal Engineering, 2014

It is aimed to study forced convection heat transfer for non-Newtonian power-law fluids in a para... more It is aimed to study forced convection heat transfer for non-Newtonian power-law fluids in a parallel-plate channel with transverse rectangular cavities numerically. A finite volume based computation was performed using power-law discretization scheme and SIMPLE algorithm. The flow is assumed to be two-dimensional, incompressible, laminar and steady. Complex flow patterns such as deflection and re-circulation caused by the variation of cross-section area along the stream wise direction have been studied. Also, temperature distribution influenced by these perturbations has been discussed. In particular, the effects of Reynolds number ð50 r Re r 350Þ, power law index ð0:5 r n r 2Þ and aspect ratio of channel cavities (A.R¼0.25, 0.5) on heat transfer characteristics have been explored for channels of single and double cavity configuration. In all examined cases, varying levels of heat transfer enhancement were observed. The constant wall temperature condition has been applied.

Volume 6A: Energy, 2016

This paper presents a mathematical model for the thermo-economic evaluation of an Organic Rankine... more This paper presents a mathematical model for the thermo-economic evaluation of an Organic Rankine Cycle (ORC), which recovers exhaust gases from an internal combustion engine (ICE) based cogeneration plant, currently in operation in Turin, Italy. The model is based on a complete set of experimental data of the plant, for both nominal and partial load operation conditions. The main components of the ORC plant have been modelled and a thermo-economic analysis has been carried out for each component. The aim of the paper is to perform a thermo-economic analysis of the system through the Theory of Exergetic Cost, in order to provide a complete diagnosis of the plant, by quantifying the performances of the whole system and its sub-systems, and by determining the monetary costs and the exergetic costs. The model can represent a useful decision-making tool for the optimal design of similar plants.

International Journal of Hydrogen Energy, 2016

In the context of attempts to improve the performance of Proton Exchange Membrane (PEM) fuel cell... more In the context of attempts to improve the performance of Proton Exchange Membrane (PEM) fuel cells with a heterogeneous porous gas diffusion layer (GDL) consisting of carbon paper, we investigated whether-and to which degree-pulsating the pressure in a single waveform cathode channel affects the flow field in the channel and the performance of the fuel cell. In this 2-D study, the GDL was modeled by a stochastic arrangement of circular solid obstacles the macroscopic transport properties of which, such as permeability and tortuosity, were numerically simulated and found to compare favorably with experimental data. The focus of this paper is on the effects of varying amplitude and frequency of the pressure pulsations on cell performance. The results obtained show that a pulsating pressure enhances the convective species transport to the reaction sites and thereby increases cell performance. We found that in a waveform channel a pulsatile pressure with an amplitude as high as 0.7 times the pressure drop over the cathode channel improves the fuel cell performance by around 7%, while the effect of pulsation frequency on output power is marginally small only.

Http Www Theses Fr, 1996

Nous nous proposons d'effectuer une etude numerique et experimentale du refroidissement avec ... more Nous nous proposons d'effectuer une etude numerique et experimentale du refroidissement avec changement de phase, en regime instationnaire. Nous determinons les lois de l'ecoulement et du transfert de chaleur, pour des fluides non-newtoniens thermodependants a seuil. Ces fluides s'ecoulent dans une conduite cylindrique horizontale, refroidie a la paroi par l'ecoulement externe tel que coefficient d'echange convectif soit uniforme. Nous nous interessons aux fluides viscoplastiques dont le comportement peut etre modelise par la loi de Herschel-Bulkley. D'un point de vue numerique, nous avons utilise deux formulations ([omega]-[psi]) et (u-v-p) pour resoudre les equations gouvernant le probleme. La similarite des resultats obtenus nous a permis de privilegier la formulation (u-v-p). De plus, nous avons mis en evidence l'incidence de divers parametres sur la structure du champ dynamique et sur le transfert de chaleur. Sur le plan experimental, nous avons utilise une boucle d'essais fonctionnant en circuit ferme, Au cours de nos essais nous avons mesure divers parametres tels que: debits, temperatures et epaisseur du depot solide. Pour obtenir une caracterisation rheologique precise de notre produit, nous avons utilise un rheometre a contrainte imposee. Notre recherche nous a permis de mettre en evidence l'influence du coefficient d'echange externe (h[infini]), de la temperature du fluide refrigerant (T[infini]), de la temperature d'entree du fluide de travail (Te) du debit (Q), du parametre de thermodependance (bk ) sur les champs thermique et dynamique et d'etablir des correlatons pour le coefficient de frottement et le nombre de Nusselt.

Energy Engineering Management, Mar 15, 2012

International Journal of Engineering, 2013

In the current work, the mesh free Smoothed Particle Hydrodynamics (SPH) method, was employed to ... more In the current work, the mesh free Smoothed Particle Hydrodynamics (SPH) method, was employed to numerically investigate the transient flow of a viscoplastic material. Using this method, large deformation of the sample and its free surface boundary were captured without the cumbersome process of the grid generation. This three-step SPH scheme employs an explicit predictor-corrector technique and the incompressibility characteristic of the material was guaranteed by solving a pressure Poisson equation. The Papanastasiou constitutive model was also utilized in the simulations to study the compression of the sample under both constant load and constant velocity conditions. The no-slip boundary condition was satisfied by projecting the velocity of the viscoplastic material on the wall particles. In order to validate the fidelity of this numerical method during the compression of the samples, the resultant load at constant velocity as well as the height change of the sample for a constant load were computed and compared with other published results. The results indicated that this method could be employed as a reliable technique to simulate such highly deformable viscoplastic deformation of the materials.

Heat and Mass Transfer, 2014

based on the maximum heat transfer enhancement per pressure loss. Greek symbols μ Dynamic viscosi... more based on the maximum heat transfer enhancement per pressure loss. Greek symbols μ Dynamic viscosity (kg/ms) ρ Density (kg/m 3) ϕ Volume fraction η Efficiency index Subscripts Avg Average value I Input F Base fluid M Bulk Nf Nanofluid

Heat Transfer Research, 2014