Caracterización hidrodinámica y procesos de mezcla en un depósito de agua potable mediante técnicas de dinámica de fluidos computacional (CFD)

Se han desarrollado simulaciones del flujo de ensayos llevados a cabo en el Instituto de Hidromecánica de Karlsruhe en un tanque rectangular. Los datos experimentales sirven para validar los modelos y, en conjunto, para estudiar en profundidad los procesos de mezcla. La técnica de CFD empleada es URANS (Unsteady Reynolds Averaged Navier-Stokes).Moncho Esteve, IJ. (2011). Caracterización hidrodinámica y procesos de mezcla en un depósito de agua potable mediante técnicas de dinámica de fluidos computacional (CFD). http://hdl.handle.net/10251/15736Archivo delegad

Procesos de Mezcla en Flujos Turbulentos con Técnicas de la Mecánica de Fluidos Computacional (CFD)

Tesis por compendioThe mixing processes are present in the hydraulics engineering field as well as in the environmental field, and they appear in many different situations that are of great interest for humankind. The mechanisms that rule these processes can be very diverse and complex, these being able to interact with each other. However, when a fluid has a turbulent behavior, it is highly unstable and three-dimensional, modifying greatly the other mixing processes. In these cases, the resolution for the fluid mechanics with classical methods can be extremely difficult, making the use of approximations and models necessary. On the other hand, in the last few years, numerical simulation techniques have advanced a lot, and with the velocity increase and the computational capacity, Computational Fluids Dynamics (CFD) allows the development of simulations of these complex processes. This doctoral thesis is motivated by the importance of analyzing the physics of the turbulent flow by numerical methods in different mixing processes of interest in the field of hydraulics engineering and the environmental fluid mechanics. It is intended to illustrate the utility and potentiality of the CFD through the application and analysis in four specific steps, grouped together in two groups of mixing processes: the ones influenced by a turbulent jet in a water tank, and the ones influenced by the turbulent structures due to the curved geometry of the meander channels. The four studied cases are: i) mixing processes in drinking water storage tanks, ii) inlet influence in the thermal stratification in hot water storage tanks, iii) turbulent flow and mixing in a meandering channel, and iv) turbulent flow and mixing in compound meandering channels. The developed work is focused in a practical context. To that effect, test simulations on each studied case have been developed. The experimental data is useful for validating the models and, overall, to thoroughly study the problem. Two CFD techniques are used to solve the Navier-Stokes equations, together with turbulence models, dispersion and/or heat transference, depending on the case. For the jet mixing cases, the chosen technique was the URANS (Unsteady Reynolds-Averaged Navier-Stokes). In the meander cases the LES (Large Eddy Simulation) technique was required. The first work shows a procedure for the study of the fluid dynamic in the mixing processes in potable water tanks. The procedure can be applied in the design and improvement of these elements by using the URANS technique together with experimental methods. In the second case, the URANS simulations in the hot water tank could determine the distribution of the temperature in the whole computational domain. Besides, the model, validated with a high level of adjustment, was developed for the study of the influence of some inlet configurations and to improve the degree of stratification. With respect to the third study, the suitability of the LES technique has been proved in the thorough study of the flow and the turbulence in meanders, even by using relatively coarse grids. The great influence of the secondary flows (due to the curved shape of the channel) on the mixing process has been clarified. Finally, the LES technique was very effective upon adding information about the flow and the turbulence in meanders with different flooding levels. A very good consistency with the experimental data was obtained, despite the use of relatively coarse grids. The mixing process between the flooding flow and the meander has been observed with more clarity.Los procesos de mezcla están presentes tanto en el campo de la ingeniería hidráulica como en el del medio ambiente y aparecen en infinidad de situaciones que son de gran interés para el ser humano. Los mecanismos que gobiernan estos procesos pueden ser muy diversos y complejos, pudiendo interaccionar entre sí. Sin embargo, cuando un fluido tiene un comportamiento turbulento, éste es altamente inestable y tridimensional, modificando en gran medida los otros mecanismos de mezcla. En estos casos, la resolución con métodos clásicos de la mecánica de fluidos puede llegar a ser extremadamente difícil, siendo necesario utilizar aproximaciones o modelos. Por otro lado, en los últimos años, se ha avanzado mucho en las técnicas de simulación numérica, y junto con el aumento de la velocidad y capacidad computacional, la Dinámica de Fluidos Computacional (en inglés Computational Fluid Dynamics, CFD) permite desarrollar simulaciones de estos complejos procesos. Esta Tesis Doctoral está motivada por la importancia de analizar mediante métodos numéricos la física del flujo turbulento en diferentes procesos de mezcla de interés en el campo de la ingeniería hidráulica y la mecánica de fluidos medioambiental. Se pretende ilustrar la utilidad y potencialidad de la CFD a través de la aplicación y análisis a cuatro casos concretos, agrupados en dos grupos de procesos de mezcla: los dominados por un chorro turbulento de entrada en un tanque de agua y los dominados por las estructuras turbulentas debidas a la propia geometría curva de los canales meándricos. Los cuatro casos de estudio son: i) procesos de mezcla en tanques de agua potable, ii) influencia del chorro de entrada en la estratificación térmica en tanques de agua caliente, iii) flujo turbulento y mezcla en canales con meandros, y iv) flujo turbulento y mezcla en canales con meandros inundables. El trabajo desarrollado está centrado en un contexto práctico donde, a partir de casos concretos, se buscan los métodos y modelos más adecuados en cada uno de ellos. A tal efecto, se han desarrollado simulaciones de ensayos llevados a cabo en cada uno de los casos de estudio. Aunque los datos experimentales empleados fueron generados por diferentes equipos de investigación, en todo momento existió una estrecha relación y colaboración con todos los grupos. Dichos datos experimentales sirvieron para validar los modelos y, en conjunto, para estudiar en profundidad el problema. El trabajo en el que se analiza el primero de los cuatro casos muestra un procedimiento para el estudio de dinámica de fluidos de los procesos de mezcla en tanques de agua potable. El procedimiento puede aplicarse en el diseño y mejora de de estos elementos mediante la técnica URANS junto con métodos experimentales. En el segundo caso, las simulaciones URANS en el tanque de agua caliente permitieron determinar la distribución de temperatura en todo el dominio computacional. Además, el modelo, validado con un alto nivel de ajuste, fue desarrollado para el estudio de la influencia de algunas configuraciones de entrada y mejorar el grado de estratificación inicial. Con el tercer caso de estudio, se ha mostrado la idoneidad de la técnica LES en el estudio en profundidad del flujo y la turbulencia en meandros, incluso habiendo empleado mallas relativamente gruesas. La mayor influencia de los flujos secundarios (resultado de la forma curva del canal) sobre el proceso de mezcla ha podido ser clarificada. Por último, la técnica LES resultó ser muy eficaz a la hora de ampliar la información disponible sobre el flujo y la turbulencia en meandros con diferentes planos de inundación. Se obtuvo una muy buena concordancia con los datos experimentales, pese al uso de mallas relativamente gruesas. El proceso de mezcla entre el flujo de la inundación y el del meandro ha podido ser observado con mayor claridad.Els processos de mescla estan presents tant en el camp de l'enginyeria hidràulica com en el del medi ambient i apareixen en infinitat de situacions que són de gran interès per a l'ésser humà. Els mecanismes que governen aquests processos poden ser molt diversos i complexos, podent interaccionar entre si. No obstant això, quan un fluid té un comportament turbulent, aquest és altament inestable i tridimensional, modificant en gran mesura els altres mecanismes de mescla. En aquests casos, la resolució amb mètodes clàssics de la mecànica de fluids pot arribar a ser extremadament difícil, sent necessari utilitzar aproximacions o models. D'altra banda, en els últims anys, s'ha avançat molt en les tècniques de simulació numèrica, i juntament amb l'augment de la velocitat i capacitat computacional, la Dinàmica de Fluids Computacional (en Anglès Computational Fluids Dynamics, CFD) permet desenvolupar simulacions d'aquests complexos processos. Aquesta Tesi Doctoral està motivada per la importància d'analitzar mitjançant mètodes numèrics la física del flux turbulent en diferents processos de mescla d'interès en el camp de l'enginyeria hidràulica i la mecànica de fluids mediambiental. Es pretén il¿lustrar la utilitat i potencialitat de la CFD a través de l'aplicació i anàlisi a quatre casos concrets, agrupats en dos grups de processos de mescla: els dominats per un doll turbulent d'entrada en un tanc d'aigua i els dominats per les estructures turbulentes degudes a la pròpia geometria corba dels canals meàndrics. Els quatre casos d'estudi són: i) processos de mescla en tancs d'aigua potable, ii) influència del doll d'entrada en l'estratificació tèrmica en tancs d'aigua calenta, iii) flux turbulent i mescla en canals amb meandres, i iv) flux turbulent i mescla en canals amb meandres inundables. El treball desenvolupat està centrat en un context pràctic on, a partir de casos concrets, es busquen els mètodes i models més adequats en cadascun d'ells. A aquest efecte, s'han desenvolupat simulacions d'experiments duts a terme en cadascun dels casos d'estudi. Tot i que les dades experimentals emprats van ser generats per diferents equips d'investigació, en tot moment va existir una estreta relació i col¿laboració amb tots els grups. Aquests dades experimentals varen servir per validar els models i, en conjunt, per estudiar en profunditat el problema. El treball en el qual s'analitza el primer dels quatre casos mostra un procediment per a l'estudi de dinàmica de fluids dels processos de mescla en tancs d'aigua potable. El procediment pot aplicar-se en el disseny i millora d'aquests elements mitjançant la tècnica URANS juntament amb mètodes experimentals. En el segon cas, les simulacions URANS en el tanc d'aigua calenta van permetre determinar la distribució de temperatura en tot el domini computacional. A més, el model, validat amb un alt nivell d'ajust, va ser desenvolupat per a l'estudi de la influència d'algunes configuracions d'entrada i millorar el grau d'estratificació inicial. En el tercer cas d'estudi, s'ha mostrat la idoneïtat de la tècnica LES en l'estudi en profunditat del flux i la turbulència en meandres, fins i tot havent emprat malles relativament gruixudes. La major influència dels fluxos secundaris (resultat de la forma corba del canal) sobre el procés de mescla ha pogut ser aclarida. Per últim, la tècnica LES va resultar ser molt eficaç a l'hora d'ampliar la informació disponible sobre el flux i la turbulència en meandres amb diferents plànols d'inundació. Es va obtenir una molt bona concordança amb les dades experimentals, malgrat l'ús de malles relativament gruixudes. El procés de mescla entre el flux de la inundació i el del meandre ha pogut ser observat amb major claredat.Moncho Esteve, IJ. (2017). Procesos de Mezcla en Flujos Turbulentos con Técnicas de la Mecánica de Fluidos Computacional (CFD) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90573TESISCompendi

Sustainable water desalination from the solar energy

Seawater desalination is the main source of water in areas where it is scarce. Reverse osmosis is among the technologies used for that purpose. It implies high energy consumption costs and, accordingly, a significant carbon footprint, as well as the depletion of limited natural resources and pollution from brine generated. AQUA.abib has developed a technology that provides fresh water as well as salt, two products from the same process, derived from seawater with few requirements from conventional energy. The thermal energy required is provided by the Sun. A pyramidal shaped energy collector is comprised of two layers: a transparent outer film and a black inner surface which heats the air between the two. It concentrates heated air at its apex where seawater is sprayed, to fully separate water from salt. The salt is collected and processed for marketing and steam-laden air is driven through a column down to an underground gallery to fully condense and collect distilled water. Latent condensation heat is recovered. No brine is produced, so no pollution is associated with the process. Economic returns come from fresh water, salt, and a multifunctional inner area enclosed in the pyramid. The structure provides a climatic conditioned space suitable for: green housing, animal farming, work and leisure activities, housing or storage. In geographical areas (or during seasons) in which water is scarce, the Sun is an excellent energy source due to its high level of irradiation. Hence, the supply of fresh water fits the demand like a key fits its lock. This technology has been tested and evaluated in different scenarios and has received a grant from the EASME programme of the European Commission. The construction of the first commercial size prototype plant is foreseen to take place at Ciutadella (Menorca, Spain) by Spring, 2018

Influence of the secondary motions on pollutant mixing in a meandering open channel flow

[EN] This paper presents large eddy simulation of turbulent flow in a meandering open channel with smooth wall and rectangular cross-section. The Reynolds number based on the channel height is 40,000 and the aspect ratio of the cross-section is 4.48. The depthaveraged mean stream-wise velocity agree well to experimental measurements. In this specific case, two interacting cells are formed that swap from one bend to the other. Transport and mixing of a pollutant is analysed using three different positions of release, e.g. on the inner bank, on the outer bank and on the centre of the cross section. The obtained depth-average mean concentration profiles are reasonably consistent with available experimental data. The role of the secondary motions in the mixing processes is the main focus of the discussion. It is found that the mixing when the scalar is released on the centre of the cross-section is stronger and faster than the mixing of the scalar released on the sides. When the position of release is close to a bank side, the mixing is weaker and a clear concentration of scalar close to the corresponding side-wall can be observed in both cases.MGV acknowledges the financial support of the Spanish Ministry of Education through the program Jose Castillejo.Moncho Esteve, IJ.; Folke, F.; García-Villalba, M.; Palau-Salvador, G. (2017). Influence of the secondary motions on pollutant mixing in a meandering open channel flow. Environmental Fluid Mechanics. 17(4):695-714. https://doi.org/10.1007/s10652-017-9513-4S695714174Julien PY, Duan JG (2005) Numerical simulation of the inception of channel meandering. Earth Surf Process Landf J Br Geomorphol Res Group 30:1093–1110Boussinesq J (1868) Mémoire sur l’influence des frottements dans les mouvements reguliers des fluids. J Math Pures Appl 13:377–424Thomson J (1876) On the origin of windings of rivers in alluvial plains, with remarks on the flow of water round bends in pipes. 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In: Proceedings of 8th FMTM-CongressMockmore C (1943) Flow around bends in stable channels. Trans ASCE 3:334Blanckaert K, De Vriend HJ (2004) Secondary flow in sharp open-channel bends. J Fluid Mech 498:353–380. doi: 10.1017/S0022112003006979Balen WV, Uijttewaal WSJ, Blanckaert K (2009) Large-eddy simulation of a mildly curved open-channel flow. J Fluid Mech 630:413–442. doi: 10.1017/S0022112009007277van Balen W, Blanckaert K, Uijttewaal WSJ (2010) Analysis of the role of turbulence in curved open-channel flow at different water depths by means of experiments, LES and RANS. J Turbul 11:N12. doi: 10.1080/14685241003789404Christensen HB (1999) Secondary turbulent flow in an infinte bend. Iahr Symp. River Coast. Estuar. MorphodynamicsBlanckaert K, Graf WH (2004) Momentum transport in sharp open-channel bends. J Hydraul Eng 130:186–198. doi: 10.1061/(ASCE)0733-9429(2004)130:3(186)Stoesser T, Ruether N, Olsen NRB (2010) Calculation of primary and secondary flow and boundary shear stresses in a meandering channel. Adv Water Resour 33:158–170. doi: 10.1016/j.advwatres.2009.11.001Blanckaert K, Duarte A, Chen Q, Schleiss AJ (2012) Flow processes near smooth and rough (concave) outer banks in curved open channels. J Geophys Res Earth Surf 117:F04020. doi: 10.1029/2012JF002414Vaghefi M, Akbari M, Fiouz AR (2016) An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: secondary flow and bed shear stress. KSCE J Civ Eng 20:1582–1593. doi: 10.1007/s12205-015-1560-0Kang S, Lightbody A, Hill C, Sotiropoulos F (2011) High-resolution numerical simulation of turbulence in natural waterways. Adv Water Resour 34:98–113. doi: 10.1016/j.advwatres.2010.09.018Engel FL, Rhoads BL (2016) Three-dimensional flow structure and patterns of bed shear stress in an evolving compound meander bend. Earth Surf Process Landf 41:1211–1226. doi: 10.1002/esp.3895Khosronejad A, Hansen AT, Kozarek JL, Guentzel K, Hondzo M, Guala M, Wilcock P, Finlay JC, Sotiropoulos F (2016) Large eddy simulation of turbulence and solute transport in a forested headwater stream. J Geophys Res Earth Surf 121:2014JF003423. doi: 10.1002/2014JF003423Mera I, Franca MJ, Anta J, Peña E (2015) Turbulence anisotropy in a compound meandering channel with different submergence conditions. Adv Water Resour 81:142–151. doi: 10.1016/j.advwatres.2014.10.012Termini D (2015) Momentum transport and bed shear stress distribution in a meandering bend: experimental analysis in a laboratory flume. Adv Water Resour 81:128–141. doi: 10.1016/j.advwatres.2015.01.005Chang Y (1971) Lateral mixing in meandering channels. Ph.D., The University of IowaFischer HB (1969) The effect of bends on dispersion in streams. Water Resour Res 5:496–506. doi: 10.1029/WR005i002p00496Rozovskii IL (1957) Flow of water in bends of open channels. Kiev Acad. Sci. Ukr. SSR Isr. Program Sci. Transl. Wash. DC Available Off. Tech. Serv. US Dept Commer. 1957 Ie Jerus. 1961Taylor G (1954) The dispersion of matter in turbulent flow through a pipe. Proc R Soc Lond Math Phys Eng Sci 223:446–468. doi: 10.1098/rspa.1954.0130Elder JW (1959) The dispersion of marked fluid in turbulent shear flow. J Fluid Mech 5:544–560. doi: 10.1017/S0022112059000374Boxall JB, Guymer I (2003) Analysis and prediction of transverse mixing coefficients in natural channels. J Hydraul Eng 129:129–139. doi: 10.1061/(ASCE)0733-9429(2003)129:2(129)Demuren AO, Rodi W (1984) Calculation of turbulence-driven secondary motion in non-circular ducts. 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Mon Weather Rev 91:99–164. doi: 10.1175/1520-0493(1963)0912.3.CO;2Hinterberger C, Fröhlich J, Rodi W (2007) Three-dimensional and depth-averaged large-eddy simulations of some shallow water flows. J Hydraul Eng. doi: 10.1061/(ASCE)0733-9429(2007)133:8(857)Zhu J (1991) A low-diffusive and oscillation-free convection scheme. Commun Appl Numer Methods 7:225–232. doi: 10.1002/cnm.1630070307Denev JA, Fröhlich J, Bockhorn H (2009) Large eddy simulation of a swirling transverse jet into a crossflow with investigation of scalar transport. Phys Fluids 21:015101. doi: 10.1063/1.3054148Palau-Salvador G, García-Villalba M, Rodi W (2011) Scalar transport from point sources in the flow around a finite-height cylinder. Environ Fluid Mech 11:611–625. doi: 10.1007/s10652-010-9199-3Fröhlich J, García-Villalba M, Rodi W (2007) Scalar mixing and large-scale coherent structures in a turbulent swirling jet. 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Simple inlet devices and their influence on thermal stratification in a hot water storage tank

[EN] Thermal energy storage is a technology used mostly in buildings and industries in order to preserve thermal energy so that the stored energy can be used at a later time. Thermal stratification during the charge process in a cylindrical water tank was investigated using tools of Computational Fluid Dynamics (CFD). Simulations were validated by means of experimental measurements of time-dependent temperature profiles. The results showed that the model was able to adequately capture the experimental temperature evolution in the tank for all the validation cases. Once validated the model, simple modifications of the usual inlet devices and inflow rate by CFD techniques were accomplished with the intention of improving the tank performance. It was found that the modifications of the simulated inlet devices affected the stratification level. This could lead to improve designs and optimize system efficiency. The analyses confirmed numerically the results obtained experimentally, and it was evidenced that a sintered bronze conical diffuser can improve stratification compared to a conventional bronze elbow inlet. Therefore, CFD techniques proved to be quite a valuable complement of experimental studies. The use of low inflow, smooth out inlet velocity and operate inflow upwards near the top of the tank enhanced stratification. (C) 2017 Published by Elsevier B.V.This research was supported by the Plan Nacional de I+D+i del Ministerio de Ciencia e Innovacion (ENE2009-13376). The authors would like to thank L.H. Sanchis for his valuable and constructive suggestions during the planning and development of this research.Moncho Esteve, IJ.; Gasque Albalate, M.; González Altozano, P.; Palau-Salvador, G. (2017). Simple inlet devices and their influence on thermal stratification in a hot water storage tank. Energy and Buildings. 150:625-638. https://doi.org/10.1016/j.enbuild.2017.06.012S62563815

A numerical study of the complex flow structure in a compound meandering channel

In this study, we report large eddy simulations of turbulent flow in a periodic compound meandering channel for three different depth conditions: one in-bank and two overbank conditions. The flow configuration corresponds to the experiments of Shiono and Muto (1998). The predicted mean streamwise velocities, mean secondary motions, velocity fluctuations, turbulent kinetic energy as well as mean flood flow angle to meandering channel are in good agreement with the experimental measurements. We have analyzed the flow structure as a function of the inundation level, with particular emphasis on the development of the secondary motions due to the interaction between the main channel and the floodplain flow. Bed shear stresses have been also estimated in the simulations. Floodplain flow has a significant impact on the flow structure leading to significantly different bed shear stress patterns within the main meandering channel. The implications of these results for natural compound meandering channels are also discussed

A numerical study of the complex flow structure in a compound meandering channel

[EN] In this study, we report large eddy simulations of turbulent flow in a periodic compound meandering channel for three different depth conditions: one in-bank and two overbank conditions. The flow configuration corresponds to the experiments of Shiono and Muto (1998). The predicted mean streamwise velocities, mean secondary motions, velocity fluctuations, turbulent kinetic energy as well as mean flood flow angle to meandering channel are in good agreement with the experimental measurements. We have analyzed the flow structure as a function of the inundation level, with particular emphasis on the development of the secondary motions due to the interaction between the main channel and the floodplain flow. Bed shear stresses have been also estimated in the simulations. Floodplain flow has a significant impact on the flow structure leading to significantly different bed shear stress patterns within the main meandering channel. The implications of these results for natural compound meandering channels are also discussed.Moncho Esteve, IJ.; García-Villalba, M.; MUTO Y.; SHIONO K.; Palau-Salvador, G. (2018). A numerical study of the complex flow structure in a compound meandering channel. Advances in Water Resources. 116:95-116. https://doi.org/10.1016/j.advwatres.2018.03.013S9511611

Study of the influence of inner lining material on thermal stratification in a hot water storage tank

[EN] The present study has analysed the influence of thermal conductivity of the inner lining material on the stratification process in a hot water tank during thermal charge and the later standby period. This analysis has been carried out numerically by a three-dimensional Computational Fluid Dynamics (CFD) model. Experimental measurements of temperature profiles are used to select and verificate the model, and to later validate CFD simulations. With the validated model, temperature over time at several heights, temperature profiles, velocity contours, water streamtraces and temperature contours, are studied and compared for three different inner lining materials. The obtained results confirm that a weak conducting lining material favours energy storage in the tank and the thermal stratification of water during charge and subsequent standby period. The effect of the inner lining material on the energy accumulated in water and on the moment of energy (stratification) is potentially enhanced when the material's thermal conductivity diminishes. The use of insulating paints as inner lining for water storage tanks could be a possible solution to be studied and subsequently adopted in practice to improve the efficient use of energy in stored water. The analysis techniques employed prove most useful and enable the results to be compared and presented in a novel way.This research was supported by the Plan Nacional de I+D+i del Ministerio de Ciencia e Innovacion (ENE2009-13376). The authors would like to thank L.H. Sanchis for his valuable and constructive suggestions during the planning and development of this research.Gasque Albalate, M.; González Altozano, P.; Maurer, D.; Moncho Esteve, IJ.; Gutiérrez-Colomer, RP.; Palau-Salvador, G.; García-Mari, E. (2015). Study of the influence of inner lining material on thermal stratification in a hot water storage tank. Applied Thermal Engineering. 75:344-356. https://doi.org/10.1016/j.applthermaleng.2014.10.040S3443567

Dispersion of CO using computational fluid dynamics in a real urban canyon in the city center of Valencia (Spain)

© 2020 by the authors.One of the main environmental problems we are currently facing is air pollution. Air quality models calculate how much pollution is emitted and dispersed into the atmosphere. This research presents a Computational Fluid Dynamic model using a real urban geometry for the analysis of CO contamination with a three-dimensional model. This method includes a procedure of calculating emissions using different types of vehicles. CO Measurements are obtained from a Wireless Sensor Network to validate the models. The present study analyzes six representative real cases of different traffic situations and climatic conditions plus 3 hypothetical cases in a hotspot area in the city center of Valencia. The results show what influences pollution levels the most is the wind direction, which influences the generation of velocity patterns. In the validation cases, the real wind direction is used and a slight change produces great differences in both velocities and CO concentration. In the hypothetical cases, parallel and perpendicular winds are defined to observe the differences when this ideal situation is applied. In conclusion, the mixing and transport of air pollutants are closely related to the structures of velocity and turbulence that occur in the air, which depends strongly on the wind direction

Study of the influence of inner lining material on thermal stratification in a hot water storage tank

[EN] The present study has analysed the influence of thermal conductivity of the inner lining material on the stratification process in a hot water tank during thermal charge and the later standby period. This analysis has been carried out numerically by a three-dimensional Computational Fluid Dynamics (CFD) model. Experimental measurements of temperature profiles are used to select and verificate the model, and to later validate CFD simulations. With the validated model, temperature over time at several heights, temperature profiles, velocity contours, water streamtraces and temperature contours, are studied and compared for three different inner lining materials. The obtained results confirm that a weak conducting lining material favours energy storage in the tank and the thermal stratification of water during charge and subsequent standby period. The effect of the inner lining material on the energy accumulated in water and on the moment of energy (stratification) is potentially enhanced when the material's thermal conductivity diminishes. The use of insulating paints as inner lining for water storage tanks could be a possible solution to be studied and subsequently adopted in practice to improve the efficient use of energy in stored water. The analysis techniques employed prove most useful and enable the results to be compared and presented in a novel way.This research was supported by the Plan Nacional de I+D+i del Ministerio de Ciencia e Innovacion (ENE2009-13376). The authors would like to thank L.H. Sanchis for his valuable and constructive suggestions during the planning and development of this research.Gasque Albalate, M.; González Altozano, P.; Maurer, D.; Moncho Esteve, IJ.; Gutiérrez-Colomer, RP.; Palau-Salvador, G.; García-Mari, E. (2015). Study of the influence of inner lining material on thermal stratification in a hot water storage tank. Applied Thermal Engineering. 75:344-356. https://doi.org/10.1016/j.applthermaleng.2014.10.0403443567