Pub Date : 2011-12-01DOI: 10.1615/COMPUTTHERMALSCIEN.2011003213
K. Higashi, H. Mamori, K. Fukagata
The possibility of simultaneous control for skin-friction drag reduction and heat transfer augmentation by a traveling wave-like blowing/suction is explored for a laminar channel flow. In addition to the constant temperature difference condition, uniform heat generation is considered for the temperature field so that the boundary condition similar to that for the velocity field holds. Friction drag reduction and heat transfer augmentation are simultaneously achieved when the wave travels in the upstream direction. The global phases of streamwise velocity and temperature fluctuations are found to oppose each other, which eventually leads to dissimilarity between the friction drag and heat transfer. Direct numerical simulation (DNS) confirms that this dissimilar control effect can also be obtained in a turbulent channel flow.
{"title":"SIMULTANEOUS CONTROL OF FRICTION DRAG REDUCTION AND HEAT TRANSFER AUGMENTATION BY TRAVELING WAVE-LIKE BLOWING/SUCTION","authors":"K. Higashi, H. Mamori, K. Fukagata","doi":"10.1615/COMPUTTHERMALSCIEN.2011003213","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011003213","url":null,"abstract":"The possibility of simultaneous control for skin-friction drag reduction and heat transfer augmentation by a traveling wave-like blowing/suction is explored for a laminar channel flow. In addition to the constant temperature difference condition, uniform heat generation is considered for the temperature field so that the boundary condition similar to that for the velocity field holds. Friction drag reduction and heat transfer augmentation are simultaneously achieved when the wave travels in the upstream direction. The global phases of streamwise velocity and temperature fluctuations are found to oppose each other, which eventually leads to dissimilarity between the friction drag and heat transfer. Direct numerical simulation (DNS) confirms that this dissimilar control effect can also be obtained in a turbulent channel flow.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418659","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 : 2011-01-21DOI: 10.1615/COMPUTTHERMALSCIEN.2011003483
I. Voicu, N. Galanis, T. Maré
CFD simulations of heat transfer between two fluids in a parallel-flow vertical double-pipe heat exchanger, taking into consideration conduction in the walls, viscous dissipation, variable fluid properties, and axial diffusion in the fluids, illustrate the effects of buoyancy on the velocity and temperature profiles as well as on the Nusselt numbers and friction coefficients. In particular, the results show that flow reversal occurs at different positions depending on the flow direction. In the developing region, the fluid bulk temperatures, the wall temperature, and the local Nusselt numbers for both fluids depend on the flow direction. For the conditions under consideration, the Nusselt number for the fully developed flow in the inner pipe lies between the corresponding forced convection values for the constant heat flux and constant temperature conditions, while the one in the annulus is smaller than both these forced convection values. It is established that the flow and thermal fields in the inner cylinder and the annulus cannot be predicted correctly by studying each one separately since the thermal condition at the solid wall separating the two fluids depends on flow characteristics such as the Richardson number in the inner tube.
{"title":"Effects of buoyancy on the performance of a vertical double-pipe heat exchanger","authors":"I. Voicu, N. Galanis, T. Maré","doi":"10.1615/COMPUTTHERMALSCIEN.2011003483","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011003483","url":null,"abstract":"CFD simulations of heat transfer between two fluids in a parallel-flow vertical double-pipe heat exchanger, taking into consideration conduction in the walls, viscous dissipation, variable fluid properties, and axial diffusion in the fluids, illustrate the effects of buoyancy on the velocity and temperature profiles as well as on the Nusselt numbers and friction coefficients. In particular, the results show that flow reversal occurs at different positions depending on the flow direction. In the developing region, the fluid bulk temperatures, the wall temperature, and the local Nusselt numbers for both fluids depend on the flow direction. For the conditions under consideration, the Nusselt number for the fully developed flow in the inner pipe lies between the corresponding forced convection values for the constant heat flux and constant temperature conditions, while the one in the annulus is smaller than both these forced convection values. It is established that the flow and thermal fields in the inner cylinder and the annulus cannot be predicted correctly by studying each one separately since the thermal condition at the solid wall separating the two fluids depends on flow characteristics such as the Richardson number in the inner tube.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418835","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2011002585
A. Bahlaoui, A. Raji, M. Hasnaoui, M. Naïmi
{"title":"MIXED CONVECTION-RADIATION HEAT TRANSFER IN A VENTED PARTITIONED RECTANGULAR ENCLOSURE","authors":"A. Bahlaoui, A. Raji, M. Hasnaoui, M. Naïmi","doi":"10.1615/COMPUTTHERMALSCIEN.2011002585","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011002585","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418066","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2012004188
M. Habib, I. Al-Zaharnah, T. Ayinde, S. Al-Anizi, Y. Al-Awwad
{"title":"INFLUENCE OF BOILER SWING RATE ON DYNAMICS OF THERMAL AND FLOW CHARACTERISTICS IN WATER CIRCULATION BOILERS","authors":"M. Habib, I. Al-Zaharnah, T. Ayinde, S. Al-Anizi, Y. Al-Awwad","doi":"10.1615/COMPUTTHERMALSCIEN.2012004188","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2012004188","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418584","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2011003212
T. Hattori, S. Armfield, M. Kirkpatrick, S. Maruyama, A. Komiya
{"title":"NUMERICAL STUDY OF A TRANSITIONAL NATURAL VENTILATION FLOW DRIVEN BY A LINE SOURCE PLUME WITH VARIED REYNOLDS AND PRANDTL NUMBERS","authors":"T. Hattori, S. Armfield, M. Kirkpatrick, S. Maruyama, A. Komiya","doi":"10.1615/COMPUTTHERMALSCIEN.2011003212","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011003212","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418616","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.V3.I1.60
R. El Ayachi, A. Raji, M. Hasnaoui, A. Abdelbaki, Mohamed Naimi
{"title":"COMBINED EFFECTS OF RADIATION AND NATURAL CONVECTION IN A SQUARE CAVITY SUBMITTED TO CROSS GRADIENTS OF TEMPERATURE: CASE OF PARTIAL HEATING AND COOLING","authors":"R. El Ayachi, A. Raji, M. Hasnaoui, A. Abdelbaki, Mohamed Naimi","doi":"10.1615/COMPUTTHERMALSCIEN.V3.I1.60","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.V3.I1.60","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1615/COMPUTTHERMALSCIEN.V3.I1.60","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67420917","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2011003070
F. B. Nejma, K. Slimi
{"title":"EFFECT OF GAS RADIATION AND LAMINAR FORCED CONVECTION ON EVAPORATION","authors":"F. B. Nejma, K. Slimi","doi":"10.1615/COMPUTTHERMALSCIEN.2011003070","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011003070","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418515","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.2011002831
M. Akbari, N. Galanis, A. Behzadmehr
{"title":"Performance comparison of relations for nanofluids properties in the CFD prediction of mixed convection","authors":"M. Akbari, N. Galanis, A. Behzadmehr","doi":"10.1615/COMPUTTHERMALSCIEN.2011002831","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.2011002831","url":null,"abstract":"","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67418740","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 : 2011-01-01DOI: 10.1615/COMPUTTHERMALSCIEN.V3.I2.60
F. Jafar, G. Thorpe, O. Turan
In this paper, an experimental and numerical investigation of liquid film falling over three horizontal plain cylinders is presented. The flow Reynolds number range studied is 50−2000, rendering the flow laminar. Numerical predictions are obtained using FLUENT, a proprietary computational fluid dynamic (CFD) code, for the 2D and 3D configurations of the three cylinders. In the numerical predictions, the mathematical approach is based on the volume of fluid (VOF) method to account for the fluid's two phases, namely, air and water. The primary objective of the present study was to carry out experiments to validate the numerical code. It was found that increasing the Reynolds number resulted in the flow mode changing from droplet, to jet, to sheet mode. The numerical analyses accurately predicted the Reynolds numbers at which these transitions occur. The flow mode is also related to the separation distance between the horizontal cylinders. The flow mode tends to be droplet at large separation, whereas it tends to be jet and sheet modes at small separations. The distances between adjacent columns of droplets and the adjacent jet decrease with increasing Reynolds number and cylinder diameter, a phenomenon also captured by the numerical analyses. No effects of hysteresis were observed on the spacing of the columns of droplets and jets as the Reynolds number was increased and decreased. The frequency at which droplets fell from all of the cylinders increased when the distance between the water feeder and the cylinder increased, and this effect exhibited hysteresis as the flow rate was successively increased and decreased.
{"title":"LIQUID FILMS FALLING ON HORIZONTAL PLAIN CYLINDERS: PART 1-EXPERIMENTAL AND NUMERICAL STUDY OF FLOW BEHAVIOR","authors":"F. Jafar, G. Thorpe, O. Turan","doi":"10.1615/COMPUTTHERMALSCIEN.V3.I2.60","DOIUrl":"https://doi.org/10.1615/COMPUTTHERMALSCIEN.V3.I2.60","url":null,"abstract":"In this paper, an experimental and numerical investigation of liquid film falling over three horizontal plain cylinders is presented. The flow Reynolds number range studied is 50−2000, rendering the flow laminar. Numerical predictions are obtained using FLUENT, a proprietary computational fluid dynamic (CFD) code, for the 2D and 3D configurations of the three cylinders. In the numerical predictions, the mathematical approach is based on the volume of fluid (VOF) method to account for the fluid's two phases, namely, air and water. The primary objective of the present study was to carry out experiments to validate the numerical code. It was found that increasing the Reynolds number resulted in the flow mode changing from droplet, to jet, to sheet mode. The numerical analyses accurately predicted the Reynolds numbers at which these transitions occur. The flow mode is also related to the separation distance between the horizontal cylinders. The flow mode tends to be droplet at large separation, whereas it tends to be jet and sheet modes at small separations. The distances between adjacent columns of droplets and the adjacent jet decrease with increasing Reynolds number and cylinder diameter, a phenomenon also captured by the numerical analyses. No effects of hysteresis were observed on the spacing of the columns of droplets and jets as the Reynolds number was increased and decreased. The frequency at which droplets fell from all of the cylinders increased when the distance between the water feeder and the cylinder increased, and this effect exhibited hysteresis as the flow rate was successively increased and decreased.","PeriodicalId":45052,"journal":{"name":"Computational Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67420564","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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