Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006301
R. Ben‐Mansour, K. Suara, K. Youcef-Toumi
The accuracy of a leak detection method depends greatly on the flow and leak parameters in a given pipeline. This paper gives some insight into the flow characteristics around simulated small leaks. The present computational fluid dynamics (CFD) studies have indicated clear distinctive features in fluid pressure and fluid acceleration that can be used for the early detection of small leaks (<1% of the total flow) in water distribution pipelines. The present CFD simulations based on a steady state standard Ðo − e turbulent flow model are carried out for different pressure lines in 4 in. (100 m) ID pipe. Based on these simulations, it has been found out that the pressure gradients in the vicinity of the leaks are quite large, hence a leak detection method based on pressure gradient measurement is proposed. In addition, these simulations have shown remarkable gradients in the axial flow acceleration along the centerline of the pipe. These discovered flow features can offer another leak detection method based on the use of accelerometers.
{"title":"DETERMINATION OF IMPORTANT FLOW CHARACTERISTICS FOR LEAK DETECTION IN WATER PIPELINES-NETWORKS","authors":"R. Ben‐Mansour, K. Suara, K. Youcef-Toumi","doi":"10.1615/COMPUTTHERMALSCIEN.2013006301","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006301","url":null,"abstract":"The accuracy of a leak detection method depends greatly on the flow and leak parameters in a given pipeline. This paper gives some insight into the flow characteristics around simulated small leaks. The present computational fluid dynamics (CFD) studies have indicated clear distinctive features in fluid pressure and fluid acceleration that can be used for the early detection of small leaks (<1% of the total flow) in water distribution pipelines. The present CFD simulations based on a steady state standard Ðo − e turbulent flow model are carried out for different pressure lines in 4 in. (100 m) ID pipe. Based on these simulations, it has been found out that the pressure gradients in the vicinity of the leaks are quite large, hence a leak detection method based on pressure gradient measurement is proposed. In addition, these simulations have shown remarkable gradients in the axial flow acceleration along the centerline of the pipe. These discovered flow features can offer another leak detection method based on the use of accelerometers.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013008157
L. Dombrovsky, J. Randrianalisoa, W. Lipiński, V. Timchenko
A promising approach to the treatment of superficial human cancer is laser induced hyperthermia. A correct choice of the parameters used for the treatment planning should be based on modeling of both radiative transfer and transient heating of human tissues which will allow to predict the thermal conversions in the tumor. In this paper, we focus on the radiative transfer modeling which should be as simple as possible to be implemented in the combined heat transfer model. In general, the well-known P1 approximation is known to be sufficiently accurate in calculations of the absorbed radiation power distribution. At the same time, the error of this approximation may increase in the case of external irradiation, and thus needs to be examined by the comparison with the direct Monte Carlo simulation. The computational study with realistic geometrical and optical parameters of the problem undertaken in this work showed that the P1 approximation considerably underestimates the intense absorption near the body surface in comparison with the direct Monte Carlo solution. At the same time, it has been shown that a 1-D solution for radiative transfer can be used as a valid approach due to intense scattering of radiation by tissues. As a result, the modified two-flux approximation is recommended as a component of the multidimensional combined heat transfer model for soft thermal treatment of superficial tumors. NOMENCLATURE a particle radius D radiation diffusion coefficient fv volume fraction of gold nanoshells G irradiation J diffuse component of radiation intensity m complex index of refraction, n i n index of refraction N ray number Q efficiency factor of absorption or scattering r radial coordinate r radius-vector R Fresnel’s reflectivity, random numbers V volume W absorbed radiation power z axial coordinate Greek symbols absorption coefficient extinction coefficient γ coefficient in boundary condition scattering coefficient index of absorption direction cosine scattering asymmetry factor scattering albedo unit vector of direction Subscripts and superscripts a absorbed ray traced rays s scattered t human tissue tr transport wavelength
{"title":"SIMPLIFIED APPROACHES TO RADIATIVE TRANSFER SIMULATIONS IN LASER-INDUCED HYPERTHERMIA OF SUPERFICIAL TUMORS","authors":"L. Dombrovsky, J. Randrianalisoa, W. Lipiński, V. Timchenko","doi":"10.1615/COMPUTTHERMALSCIEN.2013008157","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013008157","url":null,"abstract":"A promising approach to the treatment of superficial human cancer is laser induced hyperthermia. A correct choice of the parameters used for the treatment planning should be based on modeling of both radiative transfer and transient heating of human tissues which will allow to predict the thermal conversions in the tumor. In this paper, we focus on the radiative transfer modeling which should be as simple as possible to be implemented in the combined heat transfer model. In general, the well-known P1 approximation is known to be sufficiently accurate in calculations of the absorbed radiation power distribution. At the same time, the error of this approximation may increase in the case of external irradiation, and thus needs to be examined by the comparison with the direct Monte Carlo simulation. The computational study with realistic geometrical and optical parameters of the problem undertaken in this work showed that the P1 approximation considerably underestimates the intense absorption near the body surface in comparison with the direct Monte Carlo solution. At the same time, it has been shown that a 1-D solution for radiative transfer can be used as a valid approach due to intense scattering of radiation by tissues. As a result, the modified two-flux approximation is recommended as a component of the multidimensional combined heat transfer model for soft thermal treatment of superficial tumors. NOMENCLATURE a particle radius D radiation diffusion coefficient fv volume fraction of gold nanoshells G irradiation J diffuse component of radiation intensity m complex index of refraction, n i n index of refraction N ray number Q efficiency factor of absorption or scattering r radial coordinate r radius-vector R Fresnel’s reflectivity, random numbers V volume W absorbed radiation power z axial coordinate Greek symbols absorption coefficient extinction coefficient γ coefficient in boundary condition scattering coefficient index of absorption direction cosine scattering asymmetry factor scattering albedo unit vector of direction Subscripts and superscripts a absorbed ray traced rays s scattered t human tissue tr transport wavelength","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006321
Xiaogang Yang, Yiyi Wu, Xiaobing Huang, V. Barrioz, G. Kartopu, S. Monir, S. Irvine
Metalorganic Chemical Vapour Deposition (MOCVD) is an attractive method for depositing thin films of cadm ium telluride (CdTe) and other group II-VI compound materials. It has been known that the growth rate of CdTe thin film is sen sitive to the substrate temperature and the reactant partial pres sures, indicating that the deposition process is kinetical ly controlled and affected by many conditions. In the deposition process, heterogeneous reactions play an important role in f ilm formation and the process is further complicated by the coupling of gas and surface reactions via desorptio n of the reactive intermediates. A detailed understanding of the deposition mechanism and kinetics will be crucial f or the design, optimization and scale-up of II-VI MOCVD reactors. This paper presents the results of CFD modelling of the deposition process in an inline MOCVD reactor, taki ng into account the heat transfer and mass transport of the chemical species. The numerical simulations have been conducted using the CFD code, ANSYS FLUENT. The influence of the process controlling parameters such as total flow rate, rea ctor pressure and substrate temperature on the deposition behavio ur has been assessed. In the present study, dimethylcadmium (DMCd) and diisopropyltelluride (DiPTe) have been used as prec ursors while H 2 is acting as the carrier gas and N 2 as the flushing gas. The capabilities of using the developed CFD models for revealing the deposition mechanisms in MOCVD have been demonstrated. The simulations have been conducted in both mass transport and kinetics regimes at the temperat ure range of 355-455 ° to match the experimental conditions.
{"title":"NUMERICAL SIMULATION OF THE DEPOSITION PROCESS AND THE EPITAXIAL GROWTH OF CADMIUM TELLURIDE THIN FILM IN A MOCVD REACTOR","authors":"Xiaogang Yang, Yiyi Wu, Xiaobing Huang, V. Barrioz, G. Kartopu, S. Monir, S. Irvine","doi":"10.1615/COMPUTTHERMALSCIEN.2013006321","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006321","url":null,"abstract":"Metalorganic Chemical Vapour Deposition (MOCVD) is an attractive method for depositing thin films of cadm ium telluride (CdTe) and other group II-VI compound materials. It has been known that the growth rate of CdTe thin film is sen sitive to the substrate temperature and the reactant partial pres sures, indicating that the deposition process is kinetical ly controlled and affected by many conditions. In the deposition process, heterogeneous reactions play an important role in f ilm formation and the process is further complicated by the coupling of gas and surface reactions via desorptio n of the reactive intermediates. A detailed understanding of the deposition mechanism and kinetics will be crucial f or the design, optimization and scale-up of II-VI MOCVD reactors. This paper presents the results of CFD modelling of the deposition process in an inline MOCVD reactor, taki ng into account the heat transfer and mass transport of the chemical species. The numerical simulations have been conducted using the CFD code, ANSYS FLUENT. The influence of the process controlling parameters such as total flow rate, rea ctor pressure and substrate temperature on the deposition behavio ur has been assessed. In the present study, dimethylcadmium (DMCd) and diisopropyltelluride (DiPTe) have been used as prec ursors while H 2 is acting as the carrier gas and N 2 as the flushing gas. The capabilities of using the developed CFD models for revealing the deposition mechanisms in MOCVD have been demonstrated. The simulations have been conducted in both mass transport and kinetics regimes at the temperat ure range of 355-455 ° to match the experimental conditions.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006227
I. Gherasim, N. Galanis, C. T. Nguyen
{"title":"NUMERICAL STUDY OF NANOFLUID FLOW AND HEAT TRANSFER IN A PLATE HEAT EXCHANGER","authors":"I. Gherasim, N. Galanis, C. T. Nguyen","doi":"10.1615/COMPUTTHERMALSCIEN.2013006227","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006227","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006032
D. Srinivasacharya, C. RamReddy
{"title":"MIXED CONVECTION HEAT AND MASS TRANSFER IN A DOUBLY STRATIFIED MICROPOLAR FLUID","authors":"D. Srinivasacharya, C. RamReddy","doi":"10.1615/COMPUTTHERMALSCIEN.2013006032","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006032","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013004094
Ann Lee, G. Yeoh, V. Timchenko, J. Reizes
{"title":"EFFECT OF VARIABLE PROPERTIES ON HEAT TRANSFER IN A MICRO-CHANNEL WITH A SYNTHETIC JET","authors":"Ann Lee, G. Yeoh, V. Timchenko, J. Reizes","doi":"10.1615/COMPUTTHERMALSCIEN.2013004094","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013004094","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013005954
A. Yuen, G. Yeoh
{"title":"NUMERICAL SIMULATION OF AN ENCLOSURE FIRE IN A LARGE TEST HALL","authors":"A. Yuen, G. Yeoh","doi":"10.1615/COMPUTTHERMALSCIEN.2013005954","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013005954","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006557
Vinicius Malatesta, L. Souza, J. T. Liu
{"title":"INFLUENCE OF GOERTLER VORTICES SPANWISE WAVELENGTH ON HEAT TRANSFER RATES","authors":"Vinicius Malatesta, L. Souza, J. T. Liu","doi":"10.1615/COMPUTTHERMALSCIEN.2013006557","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006557","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2013006349
A. Çağlar, C. Yamali
A coupled heat and mass transfer analysis of the adsorbent bed of a thermal wave adsorption cooling cycle is performed. The adsorbent bed is modeled two dimensionally. Governing equations for energy, mass and momentum transfers are solved by Comsol Multiphysics simultaneously. Variations of temperature, pressure, adsorption capacity, equilibrium adsorption capacity and mass transfer coefficient for a finless tube adsorbent bed are presented with multicolored plots. Desorption process is simulated in the model. Results show that the adsorbent bed reaches the maximum cycle temperature uniformly after 5000s. Uniform pressure assumption can be used in the bed due to small pressure gradient during the process. Adsorption capacity decreases from 26.1% to 8.89% in 5000s. Temperature front progresses along the bed creating a thermal wave. The thermal wave length is needed to be short to enhance the bed effectiveness regenerating more heat between the beds of the thermal wave cycle. It can be concluded that a parametric study is recommended for a future work in order to investigate the effects of design and operational parameters on the dependent variables and thermal wave length.
{"title":"Analysis of heat and mass transfer in the adsorbent bed of a thermal wave adsorption cooling cycle","authors":"A. Çağlar, C. Yamali","doi":"10.1615/COMPUTTHERMALSCIEN.2013006349","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2013006349","url":null,"abstract":"A coupled heat and mass transfer analysis of the adsorbent bed of a thermal wave adsorption cooling cycle is performed. The adsorbent bed is modeled two dimensionally. Governing equations for energy, mass and momentum transfers are solved by Comsol Multiphysics simultaneously. Variations of temperature, pressure, adsorption capacity, equilibrium adsorption capacity and mass transfer coefficient for a finless tube adsorbent bed are presented with multicolored plots. Desorption process is simulated in the model. Results show that the adsorbent bed reaches the maximum cycle temperature uniformly after 5000s. Uniform pressure assumption can be used in the bed due to small pressure gradient during the process. Adsorption capacity decreases from 26.1% to 8.89% in 5000s. Temperature front progresses along the bed creating a thermal wave. The thermal wave length is needed to be short to enhance the bed effectiveness regenerating more heat between the beds of the thermal wave cycle. It can be concluded that a parametric study is recommended for a future work in order to investigate the effects of design and operational parameters on the dependent variables and thermal wave length.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67419897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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