Academic literature on the topic 'Ventilated envelopes'
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Journal articles on the topic "Ventilated envelopes"
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Monstvilas, Edmundas, Karolis Banionis, Jurga Poderytė, Raimondas Bliūdžius, and Arūnas Burlingis. "ON THE SOLUTION OF ENERGY BALANCE EQUATION SYSTEM TO PREDICT TEMPERATURE DISTRIBUTION IN THE BUILDING ELEMENTS WITH VENTILATED AIR GAP." Journal of Civil Engineering and Management 21, no. 1 (December 23, 2014): 21–30. http://dx.doi.org/10.3846/13923730.2014.937357.
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The article presents the solution of heat balance equation system, describing heat exchange processes in ventilated envelopes, which was applied to derive formulas for the calculation of temperatures in the ventilated layers of the envelopes. The accurateness of the formulas was assessed by experimental research and analysis of the calculation results. During the process of heat exchange balance equation solution, the equations were simplified by introducing the following restriction into the derived formulas: they may only be applied for the ventilated envelopes with steel or similar coatings as their external layers, i.e. coatings having small heat capacity and minor difference between the external and internal surface temperatures. The derived formulas enable the calculation of the temperatures of the ventilated envelopes in the distance which does not exceed a half of the ventilated air gap length measuring from the air entrance into the gap. However, this restriction does not impede the estimation of the average thermal indicators of the ventilated envelopes.
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Capener, Carl-Magnus, and Eva Sikander. "Green Building Envelopes – Moisture Safety in Ventilated Light-weight Building Envelopes." Energy Procedia 78 (November 2015): 3458–64. http://dx.doi.org/10.1016/j.egypro.2015.11.179.
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Balter, Julieta, Carolina Ganem, and Gustavo Barea. "Mejoras en el desempeño energético de edificios en verano mediante la integración de envolventes ventiladas en fachadas norte y cubiertas. El caso de Mendoza, Argentina." Revista Hábitat Sustentable 10, no. 2 (December 30, 2020): 94–105. http://dx.doi.org/10.22320/07190700.2020.10.02.07.
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The proposal of energy efficiency measures in the residential sector in Argentina requires analyzing the architectonic possibilities of building rehabilitation using technologies that reduce energy consumption, that are feasible to implement locally. In regions with high solar radiation levels, as is the case of the city of Mendoza, heat fluxes transmitted inside can be reduced by the natural ventilation of the layers in the envelope, both on facades and roofs, thus obtaining significant savings in consumption for cooling purposes. This work evaluates the potential for improvement with the integration of ventilated envelopes. The work methodology is structured in two stages: i) survey of residential buildings by morphological typology and analysis of rehabilitation possibilities with ventilated facades, considering the exposed envelope surfaces by orientation; ii) simulation of a case study - previously validated with onsite measurements - using the EnergyPlus software. On integrating ventilated facades and roofs important energy savings of around 32% were achieved, considering the building without users (unoccupied). In the case of units on the top floor, with roofs exposed to the outside, energy savings of 260% were recorded.
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Saelens, Dirk, and Hugo Hens. "Experimental Evaluation of Airflow in Naturally Ventilated Active Envelopes." Journal of Thermal Envelope and Building Science 25, no. 2 (October 2001): 101–27. http://dx.doi.org/10.1106/cu0x-xl16-6qta-29qc.
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Gao, Jun, Jia-ning Zhao, and Fu-sheng Gao. "Displacement of Natural Ventilation in an Enclosure With a Convective/Radiative Heat Source and Nonadiabatic Envelopes." Journal of Solar Energy Engineering 128, no. 1 (April 2, 2005): 83–89. http://dx.doi.org/10.1115/1.2148975.
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This paper studies the real case of naturally ventilated space with a convective/radiative heat source and nonadiabatic envelopes. The real envelopes and heat source are introduced into a simple two-layer model of the displacement of natural ventilation, and then contribute to achieving a newly developed one: the “Thermal and airFlow Natural Ventilation” (TFNV) model. The TFNV model divides a whole space into two vertical zones of different temperatures and defines air temperature in the lower zone higher than in outdoor air. Comparisons of the predictions by the TFNV model and Computational Fluid Dynamics (CFD) simulation show good agreement. It is found that the TFNV model simplifies the multilevel stratifications in such a real case of naturally ventilated space into an ideal two-layer thermal stratification. Through a procedure for the TFNV model, fundamental guidelines for well-designed real naturally ventilated buildings are then discussed in this paper. Two notable points are presented, first, improving natural ventilation by increasing the effective area of openings and second, designing displacement of natural ventilation based on a desired interface height.
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Karpov, D. F., M. V. Pavlov, A. A. Sinitsyn, N. N. Monarkin, and A. G. Gudkov. "FEATURES OF MOUNTED VENTILATED FACADE HEAT CONTROL SYSTEMS IN CONSTRUCTION PROJECTS." Herald of Dagestan State Technical University. Technical Sciences 47, no. 1 (April 21, 2020): 147–55. http://dx.doi.org/10.21822/2073-6185-2020-47-1-147-155.
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Abstract. Aim. An integral part of an energy audit of buildings and structures consists in thermal imaging diagnostics. This permits an evaluation of the heat-shielding properties of the enclosing structures of buildings in order to control the functional and operational status of engineering systems, as well as to identify implicit (invisible) and explicit (visible) defects in them. The aim of the work is to analyse some features and results of thermal control of an opaque hinged ventilated facade system and translucent enclosing structures in the form of window systems of a capital construction project. Method. Thermal imaging was used as a control for resolving issues of energy and resource conservation. The special importance of thermal control of translucent facade systems and non-translucent hinged ventilated facades of capital construction projects having various functional and operational purposes is highlighted. Results. A detailed algorithm is presented for supporting a comprehensive diagnosis of the heat engineering state of building envelopes for various construction projects by analysing thermograms, using thermal monitoring methods, to take into consideration engineering systems, building materials and finished products, along with technologies of full-scale thermal imaging inspection of translucent building envelopes. The obtained thermograms are presented and analysed. Conclusion. Current problems in the fields of energy efficiency and energy saving in the construction and energy industries are considered in the light of the latest technological developments. The proposed graph-analytical algorithm supporting a diagnosis of the heat engineering state of building envelopes based on the analysis of thermograms is the most comprehensive among known analogues and prototypes
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Sadauskiene, Jolanta, Juozas Ramanauskas, and Algimantas Vasylius. "Impact of point thermal bridges on thermal properties of building envelopes." Thermal Science 24, no. 3 Part B (2020): 2181–88. http://dx.doi.org/10.2298/tsci180719299s.
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During the design of energy-efficient buildings with a ventilated fa?ade systems, the evaluation of point thermal transmittance is complicated. It requires additional theoretical knowledge, special software and skills to use it. Because of that, point thermal transmittance is often ignored in practice. The dependence of point thermal transmittance, which is appearing because of aluminum fixing elements used in the insulated wall with ventilated fa?ade system, from the thermal and geometrical properties of construction layers are analyzed in this paper. Research has shown, that thermal properties of the supporting wall, where fixing element is located, had the biggest influence on the point thermal transmittance. When thermal conductivity of the supporting wall was increasing, as well as a thickness of the insulation layer, a value of thermal bridge was increasing in a non-linear way. For this reason, the thermal transmittance coefficient of all construction could increase up to 35%. When the thickness of the supporting wall and thermal conductivity of the insulation layer was increased, the value of point thermal bridge was decreasing. The tests revealed strong dependency of the point thermal bridge on the thermal conductivity of bearing layer material and the thickness of the bearing layer of wall. For this reason, thermal bridges should receive greater consideration. It is not enough to use the diagrams of typical fasteners that very often do not take into account the exact thickness and thermal characteristics of materials
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Meng, Xiaojing, Beibei Wei, and Yingni Zhai. "Sensitivity Analysis of Envelope Design Parameters of Industrial Buildings with Natural Ventilation." Sustainability 12, no. 24 (December 9, 2020): 10288. http://dx.doi.org/10.3390/su122410288.
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It is beneficial for designers to identify the most important design parameters of building envelopes. This study undertook sensitivity analysis integrated with EnergyPlus to assess the impacts of envelope design parameters for naturally ventilated industrial buildings. Sensitivity coefficients of six envelope design parameters for different internal heat intensities were analyzed and compared for buildings in the city of Xi’an, located in the cold climate zone of China. Our results showed that the heat transfer coefficient of the roofs had the most significant impact on indoor temperature. The weights were 32.29%, 33.71% and 30.71%, and the heat intensities were 5, 10 and 15 W/m3, respectively. The effect of the skylight-to-roof ratio was the second most sensitive. The impact of the solar absorptances of the walls and roof on the total number of hours was not sensitive. The results could be helpful for designers to efficiently form alternative design solutions in the design of new and retrofitting industrial buildings.
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Valachova, Denisa, Andrea Badurova, and Iveta Skotnicova. "Thermal Technical Analysis of Lightweight Timber-Based External Wall Structures with Ventilated Air Gap." Sustainability 13, no. 1 (January 4, 2021): 378. http://dx.doi.org/10.3390/su13010378.
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Lightweight timber-based structures are an increasingly common part of envelopes of new buildings due to increasing requirements for their energy performance. In addition, due to the fact that wood is a sustainable material, it can be assumed that the share of these structures in civil engineering will continue to increase. The subject of this article is the thermal analysis of timber-based lightweight structures under winter conditions to expand information about thermal processes in these structures. This article deals with the lightweight timber-based external wall structures with a ventilated facade and a double-skin roof structure. Experimental temperature measurements inside the structures and ventilated air gaps are used to perform the thermal analysis. By comparing experimental and theoretical data obtained by performing numerical simulation, it was shown that for achieving an ideal match of numerical simulations and measured physical properties it is necessary to take into account not only external temperatures affecting these structures, but also other factors such as solar radiation and heat emission into the cold night sky. In the case of the external walls with ventilated facade, the benefit of a ventilated air gap has been demonstrated in relation to smaller temperature fluctuations that affect the structures.
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Hostikka, Simo, Rahul Kallada Janardhan, Umar Riaz, and Topi Sikanen. "Fire-induced pressure and smoke spreading in mechanically ventilated buildings with air-tight envelopes." Fire Safety Journal 91 (July 2017): 380–88. http://dx.doi.org/10.1016/j.firesaf.2017.04.006.
Full textDissertations / Theses on the topic "Ventilated envelopes"
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Bakri, Miassar Mohammed. "Using Ventilated Envelopes to Improve the Thermal Performance of Buildings in Hot-Humid Climate." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/603493.
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Many attempts have been made to design buildings that reduce the heat gain inside the building. In hot-humid region, architects deal with many forces of nature. These forces might be Rain, Humidity, and solar heat gain. Thermal mass was been used for centuries in hot-arid region as a way to limit the dry-bulb temperature swing inside the building. However, there are some architects who agree that thermal mass materials could be used in hot-humid climate. This thesis project suggests using ventilated envelope that incorporates thermal mass in the design of the ventilated envelope. The result of the experiment shows that using ventilated envelopes with thermal mass would allow the heat gained in the cladding and in the thermal mass to be released to the air cavity and therefore releasing the heat from the building to the exterior atmosphere. The ventilated facade could be improved by adding thermal insulation and by using reflective materials on the cladding.
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Saadon, Syamimi. "Modeling and simulation of a ventilated building integrated photovoltaic/thermal (BIPV/T) envelope." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0049.
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La demande d'énergie consommée par les habitants a connu une croissance significative au cours des 30 dernières années. Par conséquent, des actions sont menées en vue de développement des énergies renouvelables et en particulier de l'énergie solaire. De nombreuses solutions technologiques ont ensuite été proposées, telles que les capteurs solaires PV/T dont l'objectif est d'améliorer la performance des panneaux PV en récupérant l’énergie thermique qu’ils dissipent à l’aide d’un fluide caloporteur. Les recherches en vue de l'amélioration des productivités thermiques et électriques de ces composants ont conduit à l'intégration progressive à l’enveloppe des bâtiments afin d'améliorer leur surface de captation d’énergie solaire. Face à la problématique énergétique, les solutions envisagées dans le domaine du bâtiment s’orientent sur un mix énergétique favorisant la production locale ainsi que l’autoconsommation. Concernant l’électricité, les systèmes photovoltaïques intégrés au bâtiment (BIPV) représentent l’une des rares technologies capables de produire de l’électricité localement et sans émettre de gaz à effet de serre. Cependant, le niveau de température auquel fonctionnent ces composants et en particulier les composants cristallins, influence sensiblement leur efficacité ainsi que leur durée de vie. Ceci est donc d’autant plus vrai en configuration d’intégration. Ces deux constats mettent en lumière l’importance du refroidissement passif par convection naturelle de ces modules. Ce travail porte sur la simulation numérique d'une façade PV partiellement transparente et ventilée, conçu pour le rafraichissement en été (par convection naturelle) et pour la récupération de chaleur en hiver (par ventilation mécanique). Pour les deux configurations, l'air dans la cavité est chauffé par la transmission du rayonnement solaire à travers des surfaces vitrées, et par les échanges convectif et radiatif. Le système est simulé à l'aide d'un modèle multi-physique réduit adapté à une grande échelle dans des conditions réelles d'exploitation et développé pour l'environnement logiciel TRNSYS. La validation du modèle est ensuite présentée en utilisant des données expérimentales du projet RESSOURCES (ANR-PREBAT 2007). Cette étape a conduit, dans le troisième chapitre du calcul des besoins de chauffage et de refroidissement d'un bâtiment et l'évaluation de l'impact des variations climatiques sur les performances du système. Les résultats ont permis enfin d'effectuer une analyse énergétique et exergo-économiqueThe demand of energy consumed by human kind has been growing significantly over the past 30 years. Therefore, various actions are taken for the development of renewable energy and in particular solar energy. Many technological solutions have then been proposed, such as solar PV/T collectors whose objective is to improve the PV panels performance by recovering the heat lost with a heat removal fluid. The research for the improvement of the thermal and electrical productivities of these components has led to the gradual integration of the solar components into building in order to improve their absorbing area. Among technologies capable to produce electricity locally without con-tributing to greenhouse gas (GHG) releases is building integrated PV systems (BIPV). However, when exposed to intense solar radiation, the temperature of PV modules increases significantly, leading to a reduction in efficiency so that only about 14% of the incident radiation is converted into electrical energy. The high temperature also decreases the life of the modules, thereby making passive cooling of the PV components through natural convection a desirable and cost-effective means of overcoming both difficulties. A numerical model of heat transfer and fluid flow characteristics of natural convection of air is therefore undertaken so as to provide reliable information for the design of BIPV. A simplified numerical model is used to model the PVT collector so as to gain an understanding of the complex processes involved in cooling of integrated photovoltaic arrays in double-skin building surfaces. This work addresses the numerical simulation of a semi-transparent, ventilated PV façade designed for cooling in summer (by natural convection) and for heat recovery in winter (by mechanical ventilation). For both configurations, air in the cavity between the two building skins (photovoltaic façade and the primary building wall) is heated by transmission through transparent glazed sections, and by convective and radiative exchange. The system is simulated with the aid of a reduced-order multi-physics model adapted to a full scale arrangement operating under real conditions and developed for the TRNSYS software environment. Validation of the model and the subsequent simulation of a building-coupled system are then presented, which were undertaken using experimental data from the RESSOURCES project (ANR-PREBAT 2007). This step led, in the third chapter to the calculation of the heating and cooling needs of a simulated building and the investigation of impact of climatic variations on the system performance. The results have permitted finally to perform the exergy and exergoeconomic analysis
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CHOU, PO-CHENG, and 周伯丞. "A Study on the Naturally Ventilated Performances of the Envelop Openings." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/87475388464880040722.
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博士國立成功大學
建築學系
88
The sustainability issues of recent studies are mainly focused on the energy preservation, environment protection, and economical development etc. One of the most beneficial senses is to utilize the natural driven forces to emphasize the air-exchange through the openings of the enclosure, and to reduce the dependence on utilizing the mechanical ventilation. This study, therefore, intends to develop the quantitative assess method as a tool during the design period to predict the naturally ventilated performances of rooms. Based on the literature review, numerical simulation was performed using CFD (Computational Fluid Dynamics) techniques. A full-scale bedroom Chamber was used in the experiments. Two types of windows were studied on the performances of different window positions and rotational angles. Our major findings were as below: 1. Close congruence with the experimental results shows the validity of numerical models. Those show CFD turbulence models in this study can act reasonably the role to predict the nature ventilation of buildings. 2. In the airflow of the forced convection, the standard k- model and the low-Reynolds number k- model are suitable, it, however, saves more calculated time using the standard k- model. In the airflow of the free convection, low-Reynolds number k- model performs more accurate, but a fine grid distribution near the wall boundary was necessary, and it took more calculated time. 3. In the seasons benefit the natural ventilation (spring & autumn), it is recommended utilizing cross-ventilation induced from the wind-pressure difference across the bedroom. For the bedroom-unit cases, wind-induced airflow was suitable for all of the window positions at the inlet wind-speed below 1 m/s. It was to avoid the window positions caused the mainstream through the head zone at the speed about 3 m/s. And, it was caused violently uncomfortable flow across the head zone as the air-draft effect for all of the window positions at the speed above 5 m/s. 4. In the seasons unfavorable for natural ventilation, especially in winter, it is used to close the door to keep warm in the sleeping nighttime. The single-sided ventilation, however, was harmful to provide convection. One of the solution is to utilize the central horizontal pivot window to introduce airflow into bedroom. For the bedroom-unit cases, when the window angle at 0-90°(cosθ>0), the airflow path induced from wind was against from stack, the ventilation efficiency at outdoor wind-speed UE = 0 m/s was more obvious than which at the slight wind-speed (UE = 0.3-0.5 m/s), the wind force, furthermore, become the major influence at wind-speed above 0.5 m/s. When the angle at 90-180°(cosθ<0), the airflow path induced from wind was overlapped from stack, the ventilation efficiency was greater accompanied the greater wind-speed.
Book chapters on the topic "Ventilated envelopes"
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Saber, Hamed H., Michael A. Lacasse, and Travis V. Moore. "Hygrothermal Performance Assessment of Stucco-Clad Wood Frame Walls Having Vented and Ventilated Drainage Cavities." In Advances in Hygrothermal Performance of Building Envelopes: Materials, Systems and Simulations, 198–231. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2017. http://dx.doi.org/10.1520/stp159920160100.
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Arlati, E. "University/industry experimental research program: ventilated facades envelopes & energy saving – Components' integration for innovative and sustainable building envelopes." In eWork and eBusiness in Architecture, Engineering and Construction, 197–205. CRC Press, 2020. http://dx.doi.org/10.1201/9781003060819-32.
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Zaidi, Gulrukh, and Paul H. Mayo. "Heart–lung interactions." In Oxford Textbook of Advanced Critical Care Echocardiography, edited by Anthony McLean, Stephen Huang, and Andrew Hilton, 73–80. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198749288.003.0005.
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Echocardiography is the most clinically practical method of visualizing cardiac structures and directly observing changes of cardiac function during the respiratory cycle. This chapter will review heart–lung interactions and will focus on the effects of intrathoracic pressure variation on cardiac function that can be measured with advanced critical care echocardiography. These measurements are derived from observing respirophasic variation of stroke volume (SV) and help the intensivist to guide management of haemodynamic failure. The heart–lung interactions that occur with changes in intrathoracic pressure variation have utility in identification of preload sensitivity and adverse patient ventilator interaction. Measurement of the systolic velocity envelope with pulsed-wave Doppler is a requisite skill in order to identify SV variation, as is the recognition that the measurements may be difficult with transthoracic echocardiography.
Conference papers on the topic "Ventilated envelopes"
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Bianco, Vincenzo, Bernardo Buonomo, Alessandra Diana, Oronzio Manca, and Sergio Nardini. "Numerical Investigation on Thermal and Fluid Dynamics Behaviors of the Exit Section Effect in Inclined Ventilated Roofs." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67431.
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One of the most important requirements for building performance is energy saving and recovering and they are chased developing new strategies for the reduction of energy consumption, due to the heat flux transmitted through buildings envelopes. This work examines a prototypal ventilated roof numerically using a two-dimensional model in Ansys Fluent. Only a single flap of the roof is analyzed because its structure is geometrically and thermally symmetrical. The objective of this work is to study the thermal and fluid dynamic behaviors of a ventilated roof for different configurations of the exit section of the ventilated channel. The model is evaluated in air flow, considering a k-ε turbulence model to give the governing equations. Results are a function of an assigned heat flux on the top wall of the ventilation layer. They are analyzed studying temperature and air velocity distributions. The profiles of wall temperature and air velocity along the cross sections and longitudinal sections of the ventilated layer consider the different effects of the various geometric configurations. The results for different considering configuration detect that the ridge form and the outlet reservoir dimensions do not influence the thermal behavior inside the channel whereas a smaller outlet section determines higher wall temperature and lower air velocity in the channel.
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Jiru, Teshome E., Yong X. Tao, and Fariborz Haghighat. "Airflow and Heat Transfer in Sustainable Building Components: Double-Skin Facades." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23017.
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Double skin facades (DSFs) are building envelopes comprised of two glass facades, a ventilated air cavity and shading devices placed within the cavity. In this paper airflow and heat transfer simulation was conducted for a DSF system equipped with a venetian blind using computational fluid dynamics (CFD) with RNG turbulence model. Simulation was done for a three-level combination of slat tilt angle and blind position. The heat transfer coefficient was directly obtained from CFD simulation. The CFD prediction was validated using experimental data collected for a mechanically ventilated DSF (1.6 m wide and 2.5 m high and 0.15 m wide cavity) equipped with venetian blinds. The present study indicates that the presence of venetian blinds influences the surface heat transfer coefficients (SHTCs), the temperature and the air distribution in the DSF system. Specifically, for the cases considered, the position of the blinds is more important than the slat angles.
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Zhu, Yuan, Guo-ming Chen, and Hai-fa Deng. "Analysis of Hydrogen Sulfide Impact From Sour Gas Well Blowout in Offshore Platform." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20874.
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Several sour gas leakage accidents have occurred in the offshore platform during the past decades, such as the Kab 121 platform in 2007, which caused serious consequences mainly resulting from the lethal toxicity of hydrogen sulfide (H2S). Under the threat of H2S, it is a challenge to exploit resource in the sour gas filed. Especially during the drilling operation, an abrupt blowout or kick could bring huge amount of H2S, envelop the platform and disperse in the cabins. The present paper is aimed at introducing our analysis of H2S dispersion both in the outer deck and inner mud treatment cabin so as to fully assess the potential poisoning during well blowout. The method we chosen was computational fluid dynamics according to the spatial environment characteristics of the offshore platform. First, we drew a comparison between accident consequences deriving from the wellhead configurations of an opened bell nipple and a sealed rotary blowout preventer (BOP) in the outer deck under various wind directions and speeds. The instantaneous concentrations and hazard zone distributions show that the second configuration is much better from the view of accident control. And the accident severity is much lower when the wind blows from the larboard, not from the prow for both configurations. As a result, the potential hazard zone would not envelop the entire platform with suitable platform position and arrangements of the mud return ditch, accommodation, helicopter deck et al. Then, the simulations of H2S dispersion in the mud treatment cabin were conducted in case of the closed outlet doors, opened outlet doors and sealed cabin with air ventilator working. An immediately dangerous to life level may come up in a short break with the door closed. In such a dangerous situation, H2S can only be made to disperse to other areas through the opened door or effectively ventilated away by means of a ventilator. It is a good practice to isolate the cabins with the potential H2S leakage and install ventilator. And a simple model was proposed to calculate the working time for the ventilator.
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Bagarić, Marina, Ivana Pečur, and Bojan Milovanović. "Preliminary monitoring results of ventilated heavyweight building envelope from recycled aggregate." In 7th International Building Physics Conference. Syracuse, New York: International Association of Building Physics (IABP), 2018. http://dx.doi.org/10.14305/ibpc.2018.ps26.
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Lee, Seung-Jae, Ellison Kawakami, and Roger E. A. Arndt. "Characteristics of Ventilated Supercavities in a Periodic Gust Flow." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16063.
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A ventilated supercavity consists of a large gas-filled bubble enveloped around an underwater vehicle that allows for significant drag reduction and an increase in maximum vehicle speed. Previous studies at the Saint Anthony Falls Laboratory (SAFL) of the University of Minnesota focused on the behavior of ventilated supercavities in steady horizontal flows. In open waters, vehicles can encounter unsteady flows, especially when traveling near the surface, under waves. In supercavitation technology, it is critical that the vehicle remains within the cavity while traveling through water to avoid unwanted planing forces. A study has been carried out in the high speed water tunnel to investigate the effects of unsteady flow on axisymmetric, ventilated supercavities. An attempt is made to duplicate sea states seen in open waters. In an effort to track cavity dimensions throughout a wave cycle, an automated cavity tracking script has been developed. Using a high speed camera and the proper software, it is possible to synchronize cavity dimensions with pressure measurements taken inside the cavity. Results regarding supercavity appearance, cavitation parameters and their relation to sea state conditions are presented. It was found that flow unsteadiness caused a decrease in the overall length of the supercavity while having only a minimal effect on the maximum diameter.
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Zou, Wang, Lei-Ping Xue, Wei-Wei Jin, and Xin-Tao Xiang. "Investigation of Internal Flow Velocity Distribution and Gas Loss of High-Speed Supercavitating Flows." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69468.
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Internal velocity distribution is an important content of flow structure and reveals the gas loss mechanism for supercavitating flows. Considering the three-phase momentum interactions and the water-vapor mass transport, the water-gas-vapor multi-fluid model is established to simulate ventilated supercavitating flows at high speed in the frame of the nonhomogeneous multiphase flows theory. Based on the model, the gas velocity field inside supercavity is studied. In the case of supercavitating flows around disk cavitator, two vortex cores are formed in the longitudinal plane under the actions of the adverse pressure gradient in the tail and the viscous friction on cavity surface, and are symmetrically distributed about the longitudinal axis. Most inner regions in the cavity cross section are occupied by circulation flows, where the velocity is in the opposite direction of incoming flows and decreases in the radial direction. When passing the vortex center, the velocity changes direction and increases in the radial direction. Part of gas departs to wake flows from the outermost regions close to the section boundary. The results confirm Spurk’s assumption for gas entrainment in detail. It is also found that the gas velocity distribution in the cross section through vortex cores does not depend on cavitation number. Supercavitating vehicle has the similar internal velocity distribution and gas loss mechanism. Due to the added viscous effect of the enveloped body, there are multiple axisymmetrical distributed vortices inside the cavity. The relative distance between the vortex core and the cavity wall increases downstream. Computations of ventilated supercavitating flows at different Reynolds numbers show that the gas leakage is decreasing with increasing Reynolds number for a given cavitation number. This study deepens the understanding of gas loss for ventilated supercavity at high speed, and lays a foundation for further refinement of the dynamic model of the maneuvering ventilated supercavity and the control of ventilated supercavitating flows.
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Gao, Jun, Jia-Ning Zhao, and Fu-Sheng Gao. "Displacement Natural Ventilation in an Enclosure With a Convective/Radiative Heat Source and Non-Adiabatic Envelope." In ASME 2004 International Solar Energy Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/isec2004-65147.
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This paper studies the real case of natural ventilated space with a convective/radiative heat source and non-adiabatic envelope. The real envelope and heat source are introduced into the ‘Emptying Filling Box’ model and then contribute to achieve a new developed one, Thermal and air Flow Natural Ventilation model. TFNV model combines the thermal and fluid mechanical characteristics of displacement natural ventilation. Two vertical zones of different temperature are divided as that in EFB model. But temperature in the lower zone is higher than outdoor. With TFNV model, natural ventilation parameters can be reasonably predicted — interface height, ventilation airflow rate, occupied zone temperature, etc. By comparison of the results of the two models, it is shown that EFB model underestimates the interface height as well as air temperature in the lower zone and overestimates the temperature difference between the upper and lower zone of the space. It is also observed that EFB model may improperly predict the ventilation airflow rate and ventilation load.
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Sailor, David J., Santiago Rodriguez, and Jeff Lauck. "In Situ Evaluation of Vanguard Technologies for High Performance Residential Buildings." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17528.
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High performance buildings demand innovative and often untested strategies for improving thermal performance and reducing energy consumption while maintaining indoor environmental quality. The Passive House design standard is increasingly being implemented in residential and small commercial construction. This standard results in buildings with airtight envelopes, high levels of insulation, very high performance windows, and energy efficient appliances. The intent of this paper is to evaluate the performance of several cutting-edge high performance building technologies as implemented in a Passive House duplex constructed in Portland, Oregon, USA. We provide an overview of the performance of the entire structure from multiple viewpoints, but focus largely on the performance of the heat recovery ventilator and heat pump water heater. Interactions of these systems with occupant behavior and indoor environmental quality are also discussed.
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Hendron, Robert, Mark Eastment, Ed Hancock, Greg Barker, and Paul Reeves. "Evaluation of a High-Performance Solar Home in Loveland, Colorado." In ASME 2005 International Solar Energy Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/isec2005-76231.
Full textAbstract:
Building America (BA) partner McStain Neighborhoods built the Discovery House in Loveland, Colorado, with an extensive package of energy-efficient features, including a high-performance envelope, efficient mechanical systems, a solar water heater integrated with the space-heating system, a heat-recovery ventilator (HRV), and ENERGY STAR™ appliances. The National Renewable Energy Laboratory (NREL) and Building Science Consortium (BSC) conducted short-term field-testing and building energy simulations to evaluate the performance of the house. These evaluations are utilized by BA to improve future prototype designs and to identify critical research needs. The Discovery House building envelope and ducts were very tight under normal operating conditions. The HRV provided fresh air at a rate of about 75 cfm (35 l/s), consistent with the recommendations of ASHRAE Standard 62.2. The solar hot water system is expected to meet the bulk of the domestic hot water (DHW) load (>83%), but only about 12% of the space-heating load. DOE-2.2 simulations predict whole-house source energy savings of 54% compared to the BA Benchmark [1]. The largest contributors to energy savings beyond McStain’s standard practice are the solar water heater, HRV, improved air distribution, high-efficiency boiler, and compact fluorescent lighting package.
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Hendron, Robert, Ed Hancock, Greg Barker, and Paul Reeves. "Field Evaluation of a Near Zero Energy Home in Oklahoma." In ASME 2007 Energy Sustainability Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/es2007-36103.
Full textAbstract:
The authors evaluated a Zero Energy Home (ZEH) built by Ideal Homes in Edmond, Oklahoma, that included an extensive package of energy-efficient technologies and a photovoltaic (PV) array for site electricity generation. The ZEH was part of a Building America (BA) research project in partnership with the Building Science Consortium to exhibit high efficiency technologies while keeping costs within the reach of average home buyers, and was a modified version of a production 1584-ft2, three-bedroom, single-story, slab-on-grade design with attached garage. The home included a tight, well-insulated envelope, an energy recovery ventilator, high-performance windows, tankless gas water heater, efficient lights and appliances, and a ground source heat pump (GSHP). We conducted a series of short-term tests beginning in August 2005, and have collected long-term data under occupied conditions since February 2006. The GSHP performance was disappointing until the outdoor unit was replaced, after which time the efficiency began to meet expectations. However, the electricity use of the replacement unit was higher than expected because of an unusually low cooling setpoint. Based on the measured test results, the predicted whole-house energy savings compared to the BA Benchmark was 96%, with savings of 55% for efficiency measures alone.