WSEAS Transactions on
Heat and Mass Transfer
Print ISSN: 1790-5044
Volume 9, 2014
Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of WSEAS Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.
Volume 9, 2014
Title of the Paper: Comparison between RANS and LES Approaches to the Simulation of Natural Convection in a Differentially Heated Square Cavity
Authors: Matteo Pachera, Pierfrancesco Brunello, Marco Raciti Castelli
Abstract: The capabilities of Fire Dynamics Simulator (FDS), a LES code for fire dynamics assessment, to correctly predict also a buoyancy driven flow in a small square cavity are discussed and compared with the results of a well established CFD solver (Ansys Fluent). In both cases, numerical predictions are compared with a detailed experimental benchmark available in the literature, where the flow field in a 0.75 m high, 0.75 m wide and 1.5 m deep cavity was extensively measured. Both the hot wall of the cavity and the cold one were isothermal (respectively at 50 C and 10 C), giving a Rayleigh number of 1:58 109. A quite remarkable agreement between numerical and experimental data is obtained using Ansys Fluent, while new values of the coefficients for natural convection in FDS are hereby proposed, allowing a significant improvement of the capabilities of the code to reproduce the experimental heat transfer.
Keywords: CFD; natural convection; buoyancy driven flow; FDS; Ansys Fluent.
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #23, pp. 261-269
Title of the Paper: Evaluating Severity of Impact Damage in CFRP by Determining Thermal Effusivity and Diffusivity
Authors: V. P. Vavilov, A. O. Chulkov, D. A. Derusova
Abstract: The goal of this study is the analysis of some candidate defect characterization parameters in application to the detection of impact damage in carbon fiber reinforced polymers. It is shown that quantitative evaluation of 'defectivity' aimed to further estimation of material strength, or lifetime, should be done by determining material thermal properties. Experimental results obtained are related to active thermal nondestructive testing of aviation panels with impact damage. The efficiency of some image processing algorithms, such as principal component analysis, Fourier and wavelet transform, has been evaluated. It has been found that the result of image sequence processing should be an image of diffusivity in a two-sided procedure and image of effusivity in a one-sided procedure.
Keywords: thermal nondestructive testing, heat conduction, effusivity, diffusivity, image processing
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #22, pp. 251-260
Title of the Paper: Mathematical Models for the Prediction of Heat Flux from Fire Balls
Authors: Mária Skřínská, Jan Skřínský, Vilém Sluka, Josef Senčík, Stanislav Malý, Guillaume Tetu
Abstract: The aim of this article is to summarize two mathematical models for the prediction of heat flux from Fire Ball in the context of the flammable substances safety aspects. The contribution deals with possible scenarios of accidents associated with transport and storage facilities. The study presents the results of determination of hazardous zone in the event of two various chemicals of release. For calculations, the BLEVE static model, BLEVE dynamic models included in the program EFFECTS 9.0.8. were used and results obtained were compared with the modified Netherlands Organization for Applied Scientific Research model developed by authors and programmed in NetBeans 7.4 for this study. This model can make a contribution towards solving the problems facing the flammable alternative fuels. Scenarios modeled within this study represent a possible approach to the preliminary assessment of risk that should be verified by more detailed CFD modeling. These scenarios can also be used for a quick estimation of areas endangered by an incident or accident. The results of modeling of the hazardous zones contribute to a reduction in risk of major accidents associated with these potential alternative energy sources and with the environmental safety.
Keywords: Accident, Effect modeling, Fire Ball, Heat Flux, Liquid Flammable Gas, Safety
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #21, pp. 243-250
Title of the Paper: Quantitative IR Thermography for Continuous Flow Microwave Heating
Authors: Gennaro Cuccurullo, Laura Giordano, Giacomo Viccione
Abstract: The work here presented proposes an enhanced procedure to describe bulk temperature profiles in pipe flow subjected to microwaves, by means of on-line infrared temperature readouts. Such procedure is intended to overcome the well-known difficulties connected with temperature readings while microwave heating takes place. In facts, temperatures are usually measured onto few points by means of fiberoptic probes, which are often not reasonable for properly controlling the process at hand, as the electromagnetic distribution inside the cavity yields highly uneven spatial distribution of the temperature field. This study proves that looking inside the microwave oven through a metallic grid can be successfully realized, provided proper preliminary calibration procedures are in place. In order to assess whether the resulting temperature readouts are reasonable, experimental bulk temperature related to two temperature levels and two flow rates, are compared with numerical results obtained by running a 3D FEM model, developed by the authors. Experimental and numerical results were found in quite satisfying agreement.
Keywords: Fiberoptic probes, Infrared thermography, Infrared image processing, Microwave heating of liquids, Maxwell’s equations, Numerical modelling, Experimental validation, FEM, CFD, Comsol multiphysics
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #20, pp. 234-242
Title of the Paper: Heat Production and Distribution Control System Based on Holonic Concept
Authors: Vasek Lubomir, Dolinay Viliam, Sysala Tomas
Abstract: This article shows the idea of the application of holonic concept for distributed control systems in district heating systems. Application of the holonic concepts appear to be appropriate for requirements of modern heating networks, referred as smart heat grids, which require quality control and communication infrastructure. District heating network can be divided into the autonomous elements and consequently it is possible to define tasks and relationships between them. To build and successfully manage such systems bring many benefits in comparison with centralized approaches. The first task of this research is to analyze the behavior of each heating network element in detail and define hierarchies and mutual bindings. The preparation of this holonic application has already been started for the key elements of the distribution network. The analysis focuses on physical properties and operational data of individual heat exchanger stations and their binding on other system elements.
Keywords: District heating, distributed control systems, heat distribution and consumption, holarchy, holon, Smart Thermal grid
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #19, pp. 226-233
Title of the Paper: Influence of Properties of Liquidand Substrate on Evaporation of the Sessile Drop
Authors: Oleg V. Nagornov, Nikolay V. Starostin
Abstract: The evaporation of sessile drop investigated as quasi-state-process with mutual influence of temperature and vapor concentration taken into account. Problem was solved numerically, using mathematical model based on finite element method (FEM). The model was tested by comparison its results with experimental ones. The geometry of the droplet leads to nonuniform surface temperature distribution inducing Marangoni thermal flows. We investigated influence of substrate geometry and relative thermal conductivities of substrate and liquid on surface temperature distribution.
Keywords: finite elements method, heat transfer, mathematical modeling
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #18, pp. 221-225
Title of the Paper: Updating the Modern Techniques of Radiative Heat Transfer Calculation within Fuel Furnaces and Boilers
Authors: Boris Soroka, Vladimir Zgurskyi
Abstract: Various methods of radiative heat transfer calculations are tested, verified and compared for some applied examples concerning the thermal processes within the working space of boilers and furnaces: of discrete ordinates (DOM) differential approach, of multiple reflections, of similarity with the models of computer graphics, zone method, CFD modeling, stochastic tests with Monte Carlo (MC) procedures. The opportunities and accuracy of MC calculations have been estimated for combustion chambers in 0 (zero), 1-, 2- and 3D statement. The appropriate radiation models for combustion products have been considered with special attention paid to the model of emissivity of selective (non-grey) gases computed as weighted sum of grey gases (WSGG) mostly compatible with the MC approach. Due provision the detailed and accurate information on temperature profiles within the volume zones both the thermal state and pollutants formation (particularly of NO) within the combustion chambers could be predicted being fairly coincided with measured data.
Keywords: boiler, combustion chamber, environmental pollution, industrial furnace, model of emissivity (absorptivity), Monte-Carlo (MC) technique, NOx formation, radiative heat transfer, weighted sum of grey gases (WSGG) modelб ray (beam) trajectory
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #17, pp. 205-220
Title of the Paper: Syngas Cleaning by Wet Scrubber
Authors: Marek Balas, Martin Lisy, Jiri Kubicek, Jiri Pospisil
Abstract: This work deals with syngas wet scrubbing and tar properties. Wet scrubbers are a technologies that helps clean the pollutants in the gas so that the gas may be used in combustion engines. Gas has been generated from biomass in the atmospheric fluid gasifier and has high temperature (500-800 °C). Research focuses mostly on tar elimination and dust removal.
Keywords: biomass, gasification, gas cleaning, wet scrubber, tar reduction
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #16, pp. 195-204
Title of the Paper: On a Scale Invariant Model of Statistical Mechanics and Invariant Forms of Conservation Equations
Authors: Siavash H. Sohrab
Keywords: Conservation equations, Heat mechanics, Shock waves, Statistical mechanics, TOE.
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #15, pp. 169-194
Title of the Paper: Theoretical Studies of CO2 Hydrates Formation and Dissociation in Cold Aquifers using RetrasoCodeBright Simulator
Authors: Khaled Jemai, Bjørn Kvamme, Mohammad Taghi Vafaei
Abstract: Hydrates of CO2 and water can form during aquifer storage if the reservoir has regions where conditions of pressure and temperature are inside the hydrate forming conditions. A very common assumption is that formed hydrate will be stable and will block the flow in all directions in regions where hydrate is formed, and as a consequence hydrate could seal incomplete sealing of clay or shale. In some limits this could be practically true but in general hydrates formed in sediment cannot be thermodynamically stable. Even if the hydrate is inside stability region of pressure and temperature, the hydrate may be unstable with respect to the different component concentrations (and corresponding chemical potentials) in the different phases. In this work we present a first order Taylor expansion for thermodynamic properties outside of equilibrium and apply classical nucleation theory to estimate kinetic rates for hydrate formation kinetics and similar rates in cases of under saturation. Results are applied in model studies of hydrate formation and dissociation in a model reservoir. We compare between two kinetic approaches: the first one is based on the effect of super saturation (or under saturation) in the classical nucleation theory of hydrate growth or dissociation. The second one is based on the model of Kim and Bishnoi. Unlike other reservoir simulators we apply a reactive transport reservoir simulator, RetrasoCodeBright (RCB), which considers hydrate phase transitions as “pseudo reactions”. CO2 hydrate is added to the simulator as a pseudo-mineral component and the reservoir simulator was improved to implement non-equilibrium thermodynamic calculations.
Keywords: Gas hydrate, RCB, CO2 storage, Phase transitions dynamics
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #14, pp. 150-168
Title of the Paper: Explicit and Implicit Solutions of First Order Algorithms Applied to the Euler Equations in Three-Dimensions
Authors: Edisson Sávio de Góes Maciel
Abstract: In the present work, the Roe, the Steger and Warming, the Van Leer, the Chakravarthy and Osher, the Harten, the Frink, Parikh and Pirzadeh, the Liou and Steffen Jr. and the Radespiel and Kroll schemes are implemented, on a finite volume context and using an upwind structured spatial discretization, to solve the Euler equations in the three-dimensional space. The Roe, the Harten, the Chakravarthy and Osher and the Frink, Parikh and Pirzadeh schemes are flux difference splitting ones, whereas the others schemes are flux vector splitting ones. All eight schemes are first order accurate in space and their explicit and implicit versions are implemented in three-dimensions. The explicit time integration uses a Runge-Kutta, a time splitting or an Euler method. The former is second order accurate in time, whereas the others are first order accurate in time. In the implicit case, an ADI approximate factorization is employed, which is first order accurate in time. The physical problems of the supersonic flow along a ramp, in the implicit case, and the “cold gas” hypersonic flows around a blunt body and along an air inlet, in the explicit case, are solved. The results have demonstrated that the Liou and Steffen Jr. scheme is the most conservative algorithm among the studied ones, whereas the Van Leer scheme is the most accurate.
Keywords: Flux difference splitting algorithms, Flux vector splitting algorithms, Structured schemes, Euler equations, Three-Dimensions, Supersonic and hypersonic flows
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #13, pp. 121-149
Title of the Paper: Transient Heat Transfer with Partial Boiling in System with Double Wall and Double Fins
Authors: Tabita Bobinska, Margarita Buike, Andris Buikis, Hyung Hee Cho
Abstract: In this paper we present a transient model of transient heat conduction in a 2D system with double wall and double fins. Here we consider third type linear boundary conditions and a boiling condition. Conservative averaging and finite difference methods are applied to the given problem to construct numerical solution of the given problem.
Keywords: Double wall with double fins, L-type domain, temperature fields, non-stationary heat conduction, initial-boundary value problem, conservative averaging method, difference scheme
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #12, pp. 111-120
Title of the Paper: Evaluation of Mass Transport Properties of the Advanced Medical-Interesting Porous Solids
Authors: Karel Soukup, Vladimír Hejtmánek, Olga Šolcová
Abstract: Investigation has been focused on detailed determination of the mass transport properties of novel biomaterials with unique properties for clinical applications consisted of the polymeric electrospun membranes (chitosan and polyurethane) and bone-like hydroxyapatite. Transport characteristics were determined both in the gaseous and the liquid systems by combination of Graham’s diffusion cell and an inverse liquid chromatography technique. The optimum transport parameters for chitosan and polyurethane nanofibrous membranes were found as follows: <r>ψ = 61.5 nm, ψ =0.130 and <r>ψ = 61.2 nm, ψ = 0.165, respectively. Furthermore, based on comparison of the transport parameters with textural characteristics was concluded that the most significance role in the mass transport process play a fraction of pores with radii between 370 and 470 nm. Effective diffusion coefficients (5.92×10-17 and 6.54×10-17 cm2/s) for two polystyrene samples with different molecular weight (1000 and 100,000, respectively) in cyclohexane were determined from the responses of a chromatographic column packed with the bone-like hydroxyapatite.
Keywords: Biocompatible material; Electrospun nanofibrous membrane; Chitosan; Polyurethane; Bone-like hydroxyapatite; Graham’s diffusion cell; Inverse liquid chromatography; Transport characteristics
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #11, pp. 102-110
Title of the Paper: Parametric Study of Single Effect Combined Absorption-Ejector Cooling System
Authors: Azher M. Abed, K. Sopian, M. A. Alghoul, Ali Najah Al-.Shamani, Mohdhafidz Ruslan, Sohif Mat
Abstract: In this study, a thermodynamic study based on heat transfer characteristics of the ammonia /water solar combined ejector–absorption refrigeration systemis performed. The influences of the generator temperature ,heat recovery ratio, solution circulation ratio, areinvestigated in order to gauge the least amount of heat transfer area that is needed for a given heat duty and the coefficient of performance (COP). The results showed that the increases in the heat recovery ratio of the solution heat exchanger improved the coefficient of performance. It is also found that the lower solution circulation ratio is better for both the coefficient of performance (COP) and the heat transfer area .It is evident that the COP improves with increases heat transfer area of the system at fixed operation condition. The total heat transfer area required is7.764 "m" ^"2" at generator temperature is 100 ℃ to reach the COP nearly 0.6148 for system cooling capacity of 5 kW.
Keywords: Heat transfer characteristics,performance, absorption cycles
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #10, pp. 95-101
Title of the Paper: Mixed Convection Flow of Chemically Reacting Couple Stress Fluid in an Annulus with Soret and Dufour Effects
Authors: K. Kaladhar, D. Srinivasacharya
Abstract: In this paper, mixed convection flow of couple stress fluid in circular annulus is studied. First order chemical reaction, Soret and Dufour effects are taken into consideration. The governing partial differential equations are transformed into a system of ordinary differential equations and solved by Homotopy Analysis Method (HAM). The effects of Soret number, Dufour number, chemical reaction parameter and couple stress parameter on the dimensionless velocity, temperature and concentration are analyzed graphically.
Keywords: Mixed convection, Couple stress fluid, Soret and Dufour effects, Chemical reaction, HAM
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #9, pp. 84-94
Title of the Paper: Solute Transfers Modeling In Layered Porous Media Using Differential Quadrature Method (DQ)
Authors: Meysam Ghamari Adyan, Abbas Ghaheri
Abstract: Solute or contaminant transport in porous media can be described by Advection – diffusion equations. In this research, the differential quadrature method (DQM) is employed to solve ADE in solute transport in a double-layered porous medium. This method is applied to two examples with different boundary conditions and the results are compared with analytical solutions. Also, the effect of various parameters on interface conditions are discussed in all examples. Using DQM, provides relatively exact results, while the needed mesh size is much smaller than the traditional approaches which reduces computational time and needed computer storage capacity. Another advantage of this numerical method is that applying the boundary and initial conditions can be performed easier than the other numerical methods.
Keywords: Solute transfer, porous media, DQ method, numerical method, analytical solution
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #8, pp. 74-83
Title of the Paper: Viscous Dissipation Effects on Unsteady Natural Convective Flow Past an Infinite Vertical Plate with Uniform Heat and Mass Flux
Authors: P. Loganathan, C. Sivapoornapriya
Abstract: Viscous dissipation effects on the unsteady natural convective flow over an infinite vertical plate embedded in a porous medium subject to uniform heat and mass flux is investigated. A variable suction velocity is assumed to be normal to the plate. The governing unsteady, non-linear, coupled partial differential equations are reduced to ordinary differential equations by the method of perturbation. The effects of Prandtl number, Schmidt number, permeability parameter, thermal Grashof number, mass Grashof number, Eckert number on velocity, temperature and concentration are analyzed graphically. It is observed that the fluid velocity increases with an increase in porous medium parameter. An increase in viscous dissipation effects leads to an increase in fluid velocity and temperature. An increase in the combined effects of Prandtl number and Eckert number decelerates the fluid temperature. The fluids considered for the study are hydrogen, helium, oxygen, water vapor, carbon dioxide and ethyl benzene.
Keywords: Viscous dissipation, natural convection, heat flux, mass flux, perturbation, porous medium
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #7, pp. 63-73
Title of the Paper: Performances of Heat Pump Systems as Users of Renewable Energy for Building Heating/cooling
Authors: Ioan Sarbu, Daniel Dan, Calin Sebarchievici
Abstract: The heat pumps are alternative heating/cooling systems more energy efficiency and unless pollutant in comparison with classical systems (liquid or gas fuel boiler). A large number of heat pump systems have been used in residential and commercial buildings throughout the world due to the attractive advantages of high energy and environmental performances. This paper presents the economic, energy and environmental performance criteria which show the opportunity to implement a heat pump in a heating/cooling system. A computational model of annual energy consumption for an air-to-water heat pump based on the degreeday method and the bin method implemented in a computer program is developed. In addition, from a case study a comparative economical analysis of heating solutions for a building is performed and the energy and economic advantages of building heating solution with a water-to-water heat pump are reported. Finally, the renewable energy sources contribution from heat pump sales in EU is shown.
Keywords: Renewable energy, Heating-cooling, Heat pumps, Performance indices, Annual energy consumption, Energyeconomical analysis
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #6, pp.51-62
Title of the Paper: Investigation of Turbulence Characteristics of Burning Process of the Solid Fuel in BKZ 420 Combustion Chamber
Authors: A. S. Askarova, A. Bekmukhamet, S. A. Bolegenova, M. T. Beketayeva, Yu. V. Maximov, Sh. S. Ospanova, Z. K. Gabitova
Abstract: In this paper the results obtained by the numerical method of modelling of Ekibastuz coal burning in BKZ-420 combustion chamber of Kazakhstan Power Plant. There are devoted to the numerical simulation of combustion processes in the furnace boiler BKZ-420. Boiler’s steam generating capacity equal 420 T/h. Boiler (Fig.2) has six vertical pulverized coal burners arranged in two levels with three burners on the front wall of the boiler. High ash, low-grade coal from Ekibastuz burned in the furnace. Its ash content is 40 %, volatile – 24 %, humidity – 5 %, highest calorific value is 16 750 kJ/kg. Milling dispersity of coal was equal to R90 = 15 %. It this research was shown that the most intense burning is observed in the central part of the chamber where the flow temperature reaches about 980 °C and it is seen the temperature reaches a peak in the cross sections of the location of the burners. There combustion reaction occurs more intensively.
Keywords: BKZ-420, combustion, Ekibastuz coal, heat and mass transfer, modeling, pulverized coal, turbulence, two–phase, flow
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #5, pp.39-50
Title of the Paper: Past, Present and Future Perspectives of Refrigerants in Air-Conditioning, Refrigeration and Heat Pump Applications
Authors: Ioan Sârbu, Emilian Stefan Valea
Abstract: The paper presents a study of refrigerants and some issues relating to their environmental impacts in HVAC&R equipment. They are treated aspects of the environmental pollution through the working fluids of the air-conditioning, refrigeration and heat pump systems, and a new strategy in using refrigerants in accordance with the international legislation is described. Additionally, this study presents the refrigerant development throughout the history and discusses the selection of refrigerants adapted to each utilisation based on the thermodynamic and -physical properties. Influence of those properties, which is of the utmost significance on the vapour-compression process efficiency and design are also presented. Finally, a comparative analysis of the total equivalent warming impact (TEWI) for possible substitutes of refrigerant R22 used in various air-conditioning, heat pump and refrigeration systems is performed.
Keywords: Pollution, environmental protection, cooling, refrigerants, ecological substitutes
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #4, pp.27-38
Title of the Paper: Adaptation of the Method Of Lines (MOL) to the MATLAB Code for the Analysis of the Stefan Problem
Authors: Antonio Campo, Ulises Lacoa
Abstract: This paper describes the application of the potent Method Of Lines (MOL) to the classical one-dimensional Stefan problem. The mathematical model of the Stefan problem experiences unique features, such as structural changes in the ordinary differential equation that describes the solid-liquid interface of a half-space region. To overcome these obstacles, MOL was implemented with the ordinary differential equation solver of the MATLAB code, using the unique event location property. The feasibility of MOL for treating the Stefan problem was validated upon comparing the obtained semi-numerical results against the exact analytical results available in the archival literature. Using a wide variety of Stefan numbers for engineering applications, it was realized that the Method Of Lines (MOL) coupled with the event location property tracked the temperature-time history and the moving liquid-solid interface in the half-space region admirably.
Keywords: Stefan problem, Moving solid-liquid boundary, Method Of Lines (MOL), MATLAB code, Event location property
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #3, pp.19-26
Title of the Paper: Entropy Generation Analysis of Transient Heat Conduction in a Solid Slab with Fixed Temperature Boundary Conditions
Authors: Sompop Jarungthammachote
Abstract: Analysis of entropy generation rate for transient heat conduction, taking place in homogeneous solid slab with fixed temperature boundary conditions, is presented. The initial condition is defined as a constant temperature. The exact solution is solved and used to analyze the local and total entropy generation rates. Two cases, heating and cooling processes, are considered in this study. It is found that the local entropy generation rate dramatically changes at small time and slowly approaches the local entropy generation rate of steady state case. The location of minimum local entropy generation rate can be found in the slab for both heating and cooling cases. For the total entropy generation rate, it shows very high value at small time. This is due to high temperature gradient. It, then, sharply reduces and converges to the total entropy generation rate of steady state case. However, the minimum total entropy generation rate is found for heating case, while it cannot be detected for cooling case. The minimum total entropy generation rate, found in heating case, is observed that it is lower than that of steady state case. The boundary conditions clearly express the effect on the local and total entropy generation rates for transient heat conduction. However, the effect of initial condition on the entropy generation rates can be neglected, especially at large time.
Keywords: Entropy Generation Rate, Second Law Analysis, Transient Heat Conduction, Steady State Heat Conduction, Boundary Condition of the First Type, Exact Solution
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #2, pp.9-18
Title of the Paper: Numerical Study and Analysis of Inertance-Type Pulse Tube Refrigerator
Authors: Sachindra Kumar Rout, Balaji Kumar Choudhury, Ranjit Kumar Sahoo, Sunil Kumar Sarangi
Abstract: This research article illustrates a numerical study of single stage coaxial as well as inline Inertance-Type Pulse Tube Refrigerator (ITPTR), which performance is mostly depending upon a regenerator. Regenerator is the significant component of a pulse tube refrigerator which has a great importance of producing cooling effect. In this present work a computational fluid dynamic (CFD) solution approach has been chosen for numerical purpose. The detail analysis of cool down behaviour, heat transfer at the cold end and pressure variation inside the whole system has been carried out by using the computational fluid dynamic software package FLUENT. A number of cases have been solved by changing the porosity of the regenerator from 0.5 to 0.9 and rest of parameter are remains unchanged. The operating frequency for all case is 34 Hz, pulse tube diameter 5mm and length is 125mm not changed for all cases. The result shows that porosity value of 0.6 produce a better cooling effect on the cold end of pulse tube refrigerator. The variation of pressure inside the pulse tube refrigerator during the process also analysed. To get an optimum parameter experimentally is a very tedious job for iterance tube pulse tube refrigerator. So the CFD approach gives a better solution which is the main purpose of the present work.
Keywords: Pulse tube, Refrigerator, ITPTR, Regenerator, Porosity
WSEAS Transactions on Heat and Mass Transfer, ISSN / E-ISSN: 1790-5044 / 2224-3461, Volume 9, 2014, Art. #1, pp.1-8