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Subramaniyan, Baskar, i R. Rajaraman. "Numerical Investigation on Airflow Distribution of Automotive Radiator". International Review of Mechanical Engineering (IREME) 9, nr 4 (31.07.2015): 417. http://dx.doi.org/10.15866/ireme.v9i4.6795.
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Ng, E. Y., P. W. Johnson i S. Watkins. "An analytical study on heat transfer performance of radiators with non-uniform airflow distribution". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219, nr 12 (1.12.2005): 1451–67. http://dx.doi.org/10.1243/095440705x35116.
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Heat exchangers used in modern automobiles usually have a highly non-uniform air velocity distribution because of the complexity of the engine compartment and underhood flow fields; hence ineffective use of the core area has been noted. To adequately predict the heat transfer performance in typical car radiators, a generalized analytical model accounting for airflow maldistribution was developed using a finite element approach and applying appropriate heat transfer equations including the ε-NTU (effectiveness - number of heat transfer units) method with the Davenport correlation for the air-side heat transfer coefficient. The analytical results were verified against a set of experimental data from nine radiators tested in a wind tunnel and were found to be within +24 and −10 per cent of the experimental results. By applying the analytical model, several severe non-uniform velocity distributions were also studied. It was found that the loss of radiator performance caused by airflow maldistribution, compared with uniform airflow of the same total flowrate, was relatively minor except under extreme circumstances where the non-uniformity factor was larger than 0.5. The relatively simple set of equations presented in this paper can be used independently in spreadsheets or in conjunction with computational fluid dynamics (CFD) analysis, enabling a full numerical prediction of aerodynamic as well as thermodynamic performance of radiators to be conducted prior to a prototype being built.
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Sun, He Chen, Jing Ye Zhao, Wen Hai Wang i Zhi Yong Gao. "Research on Thermal Comfort in HVAC Laboratory". Applied Mechanics and Materials 148-149 (grudzień 2011): 1122–26. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.1122.
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According to the characteristics of the laboratory, for the condition of using air conditioning that is falling to the ground pattern to assist radiator to heat, use CFD to simulate the airflow organization and thermal environment in laboratory. Meanwhile combine with the indoor relevant measured parameters, analyze distribution characteristics and finally evaluate the thermal comfort in laboratory in winter.
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Cvok, Ivan, Igor Ratković i Joško Deur. "Multi-Objective Optimisation-Based Design of an Electric Vehicle Cabin Heating Control System for Improved Thermal Comfort and Driving Range". Energies 14, nr 4 (23.02.2021): 1203. http://dx.doi.org/10.3390/en14041203.
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Modern electric vehicle heating, ventilation, and air-conditioning (HVAC) systems operate in more efficient heat pump mode, thus, improving the driving range under cold ambient conditions. Coupling those HVAC systems with novel heating technologies such as infrared heating panels (IRP) results in a complex system with multiple actuators, which needs to be optimally coordinated to maximise the efficiency and comfort. The paper presents a multi-objective genetic algorithm-based control input allocation method, which relies on a multi-physical HVAC model and a CFD-evaluated cabin airflow distribution model implemented in Dymola. The considered control inputs include the cabin inlet air temperature, blower and radiator fan air mass flows, secondary coolant loop pump speeds, and IRP control settings. The optimisation objective is to minimise total electric power consumption and thermal comfort described by predictive mean vote (PMV) index. Optimisation results indicate that HVAC and IRP controls are effectively decoupled, and that a significant reduction of power consumption (typically from 20% to 30%) can be achieved using IRPs while maintaining the same level of thermal comfort. The previously proposed hierarchical HVAC control strategy is parameterised and extended with a PMV-based controller acting via IRP control inputs. The performance is verified through simulations in a heat-up scenario, and the power consumption reduction potential is analysed for different cabin air temperature setpoints.
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Gendelis, S., i A. Jakovičs. "Numerical Modelling of Airflow and Temperature Distribution in a Living Room with Different Heat Exchange Conditions". Latvian Journal of Physics and Technical Sciences 47, nr 4 (1.01.2010): 27–43. http://dx.doi.org/10.2478/v10047-010-0016-z.
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Numerical Modelling of Airflow and Temperature Distribution in a Living Room with Different Heat Exchange ConditionsNumerical mathematical modelling of the indoor thermal conditions and of the energy losses for separate rooms is an important part of the analysis of the heat-exchange balance and energy efficiency in buildings. The measurements of heat transfer coefficients for bounding structures, the air-tightness tests and thermographic diagnostics done for a building allow the influence of those factors to be predicted more correctly in developed numerical models. The temperature distribution and airflows in a typical room (along with the heat losses) were calculated for different heater locations and solar radiation (modelled as a heat source) through the window, as well as various pressure differences between the openings in opposite walls. The airflow velocities and indoor temperature, including its gradient, were also analysed as parameters of thermal comfort conditions. The results obtained show that all of the listed factors have an important influence on the formation of thermal comfort conditions and on the heat balance in a room.
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Zhang, Xiaoyan, Baoyun Bu, Lang Liu, Tianrun Cao, Yaping Ke i Qiangqiang Du. "Numerical Simulation on Cooling Effect of Working Face under Radiation Cooling Mode in Deep Well". Energies 14, nr 15 (22.07.2021): 4428. http://dx.doi.org/10.3390/en14154428.
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Deep mining results in an increasingly serious hazard. Based on the principle of heat transfer and radiant cooling, a three-dimensional heat transfer model of the working face was established. The influence of the inlet airflow parameter, the surrounding wall temperature and other parameters on the temperature distribution of airflow along the working face were analyzed under the radiation cooling mode. The results show that the increment of airflow temperature in several sections along the working face decreases by 0.67 °C, 0.48 °C, 0.40 °C, 0.36 °C, 0.33 °C, 0.29 °C respectively. The farther away from the airflow inlet, the more obvious the cooling effect was. The airflow temperature of the working face is positively correlated with the airflow inlet temperature and the surrounding wall temperature, and is negatively correlated with the airflow velocity. The research provides a good solution for the working face cooling of deep mines, and also provides a theoretical reference for the research on the radiation cooling technology of the working face.
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Xie, Xu Liang, i Fu Lin Shen. "Numerical Investigation on Thermal Environment inside the Passenger Compartment of a Highway Sleeper Coach". Applied Mechanics and Materials 55-57 (maj 2011): 215–18. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.215.
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In order to verify thermal comfort of a 12-meter-long highway sleeper coach equipped with a four-ducted air-conditioning system, the thermal environment inside the passenger compartment was numerical investigated with RNG k-ε turbulence model. Also, discrete ordinates radiation model was applied to consider the effect of solar irradiation. The characteristic distribution of the airflow organization and temperature field were obtained and compared with experiment results. Results show that the air flow and temperature distribution inside the passenger compartment are not uniform and greatly influenced by solar radiation and air inlet parameters.
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Zeller, Marie-Louise, Jannis-Michael Huss, Lena Pfister, Karl E. Lapo, Daniela Littmann, Johann Schneider, Alexander Schulz i Christoph K. Thomas. "The NY-Ålesund TurbulencE Fiber Optic eXperiment (NYTEFOX): investigating the Arctic boundary layer, Svalbard". Earth System Science Data 13, nr 7 (14.07.2021): 3439–52. http://dx.doi.org/10.5194/essd-13-3439-2021.
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Abstract. The NY-Ålesund TurbulencE Fiber Optic eXperiment (NYTEFOX) was a field experiment at the Ny-Ålesund Arctic site (78.9∘ N, 11.9∘ E) and yielded a unique meteorological data set. These data describe the distribution of heat, airflows, and exchange in the Arctic boundary layer for a period of 14 d from 26 February to 10 March 2020. NYTEFOX is the first field experiment to investigate the heterogeneity of airflow and its transport of temperature, wind, and kinetic energy in the Arctic environment using the fiber-optic distributed sensing (FODS) technique for horizontal and vertical observations. FODS air temperature and wind speed were observed at a spatial resolution of 0.127 m and a temporal resolution of 9 s along a 700 m horizontal array at 1 m above ground level (a.g.l.) and along three 7 m vertical profiles. Ancillary data were collected from three sonic anemometers and an acoustic profiler (minisodar; sodar is an acronym for “sound detection and ranging”) yielding turbulent flow statistics and vertical profiles in the lowest 300 m a.g.l., respectively. The observations from this field campaign are publicly available on Zenodo (https://doi.org/10.5281/zenodo.4756836, Huss et al., 2021) and supplement the meteorological data set operationally collected by the Baseline Surface Radiation Network (BSRN) at Ny-Ålesund, Svalbard.
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Conceição, Eusébio, João Gomes, Maria Manuela Lúcio i Hazim Awbi. "Development of a Double Skin Facade System Applied in a Virtual Occupied Chamber". Inventions 6, nr 1 (4.03.2021): 17. http://dx.doi.org/10.3390/inventions6010017.
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In this study a system constituted by seven double skin facades (DSF), three equipped with venetian blinds and four not equipped with venetian blinds, applied in a virtual chamber, is developed. The project will be carried out in winter conditions, using a numerical model, in transient conditions, and based on energy and mass balance linear integral equations. The energy balance linear integral equations are used to calculate the air temperature inside the DSF and the virtual chamber, the temperature on the venetian blind, the temperature on the inner and outer glass, and the temperature distribution in the surrounding structure of the DSF and virtual chamber. These equations consider the convection, conduction, and radiation phenomena. The heat transfer by convection is calculated by natural, forced, and mixed convection, with dimensionless coefficients. In the radiative exchanges, the incident solar radiation, the absorbed solar radiation, and the transmitted solar radiation are considered. The mass balance linear integral equations are used to calculate the water mass concentration and the contaminants mass concentration. These equations consider the convection and the diffusion phenomena. In this numerical work seven cases studies and three occupation levels are simulated. In each case the influence of the ventilation airflow and the occupation level is analyzed. The total number of thermal and indoor air quality uncomfortable hours are used to evaluate the DSF performance. In accordance with the obtained results, in general, the indoor air quality is acceptable; however, when the number of occupants in the virtual chamber increases, the Predicted Mean Vote index value increases. When the airflow rate increases the total of Uncomfortable Hours decreases and, after a certain value of the airflow rate, it increases. The airflow rate associated with the minimum value of total Uncomfortable Hours increases when the number of occupants increases. The energy production decreases when the airflow increases and the production of energy is higher in DSF with venetian blinds system than in DSF without venetian blinds system.
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Tong, Zheming, i Hao Liu. "Modeling In-Vehicle VOCs Distribution from Cabin Interior Surfaces under Solar Radiation". Sustainability 12, nr 14 (8.07.2020): 5526. http://dx.doi.org/10.3390/su12145526.
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In-vehicle air pollution has become a public health priority worldwide, especially for volatile organic compounds (VOCs) emitted from the vehicle interiors. Although existing literature shows VOCs emission is temperature-dependent, the impact of solar radiation on VOCs distribution in enclosed cabin space is not well understood. Here we made an early effort to investigate the VOCs levels in vehicle microenvironments using numerical modeling. We evaluated the model performance using a number of turbulence and radiation model combinations to predict heat transfer coupled with natural convection, heat conduction and radiation with a laboratory airship. The Shear–Stress Transport (SST) k-ω model, Surface-to-surface (S2S) model and solar load model were employed to investigate the thermal environment of a closed automobile cabin under solar radiation in the summer. A VOCs emission model was employed to simulate the spatial distribution of VOCs. Our finding shows that solar radiation plays a critical role in determining the temperature distribution in the cabin, which can increase by 30 °C for directly exposed cabin surfaces and 10 °C for shaded ones, respectively. Ignoring the thermal radiation reduced the accuracy of temperature and airflow prediction. Due to the strong temperature dependence, the hotter interiors such as the dashboard and rear board released more VOCs per unit time and area. A VOC plume rose from the interior sources as a result of the thermal buoyancy flow. A total of 19 mg of VOCs was released from the interiors within two simulated hours from 10:00 am to noon. The findings, such as modeled spatial distributions of VOCs, provide a key reference to automakers, who are paying increasing attention to cabin environment and the health of drivers and passengers.
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Ivanov, Nikolay, Marina Zasimova, Evgueni Smirnov, Alexey Abramov, Detelin Markov i Peter Stankov. "Unsteady RANS Simulation of Air Distribution in a Ventilated Classroom with Numerous Jets". E3S Web of Conferences 111 (2019): 02010. http://dx.doi.org/10.1051/e3sconf/201911102010.
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The study is devoted to the Unsteady Reynolds-Averaged Navies-Stokes (URANS) simulation of ventilation in an isothermal room with numerous jets supplied from ceiling diffusers. The computations of the airflow under the test conditions considered were carried out in the classroom of the Technical University of Sofia with no occupants. The room floor has a simple rectangular form, but several columns, beams, window sills, and four radiators are located inside the room that makes the geometry more complex. Air is supplied to the room through four ceiling fan coils, the Reynolds number is 2×104. Calculations were carried out using the ANSYS Fluent 18.2 software with the standard k-ε turbulence model chosen. Computational meshes of up to 33 million hexahedral cells clustered to the inlet and outlet sections were used. The main aim of the study presented is to analyze and discuss the complicated 3D flow structure in the room and to give foundation for future measurements of air velocity field in the room.
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Kompatscher, Karin, Rick P. Kramer, Bart Ankersmit i Henk L. Schellen. "Indoor Airflow Distribution in Repository Design: Experimental and Numerical Microclimate Analysis of an Archive". Buildings 11, nr 4 (5.04.2021): 152. http://dx.doi.org/10.3390/buildings11040152.
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The majority of cultural heritage is stored in archives, libraries and museum storage spaces. To reduce degradation risks, many archives adopt the use of archival boxes, among other means, to provide the necessary climate control and comply with strict legislation requirements regarding temperature and relative air humidity. A strict ambient indoor climate is assumed to provide adequate environmental conditions near objects. Guidelines and legislation provide requirements for ambient indoor climate parameters, but often do not consider other factors that influence the near-object environment, such as the use of archival boxes, airflow distribution and archival rack placement. This study aimed to provide more insight into the relation between the ambient indoor conditions in repositories and the hygrothermal conditions surrounding the collection. Comprehensive measurements were performed in a case study archive to collect ambient, local and near-object conditions. Both measurements and computational fluid dynamics (CFD) modeling were used to research temperature/relative humidity gradients and airflow distribution with a changing rack orientation, climate control strategy and supply as well as exhaust set-up in a repository. The following conclusions are presented: (i) supplying air from one air handling unit to multiple repositories on different floors leads to small temperature differences between them. Differences in ambient and local climates are noticed; (ii) archival boxes mute and delay variations in ambient conditions as expected—however, thermal radiation from the building envelope may have a large influence on the climate conditions in a box; (iii) adopting night reduction for energy conservation results in an increased influence of the external climate, with adequate insulation, this effect should be mitigated; and (iv) the specific locations of the supply air and extraction of air resulted in a vertical gradient of temperature and insufficient mixing of air, and adequate ventilation strategies should enhance sufficient air mixing in combination with the insulation of external walls, and gradient forming should be reduced.
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Zhang, Li. "The Simulation Study on Environmental Field of Livestock and Poultry Establishments under Two Winds Conditions". Applied Mechanics and Materials 263-266 (grudzień 2012): 1323–26. http://dx.doi.org/10.4028/www.scientific.net/amm.263-266.1323.
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The living environment of the rural livestock has the influence on livestock health and production performance. Its living environment in general is composited by the warm air temperature, humidity, airflow (wind) speed and solar radiation. Air flow conditions within the livestock and poultry establishments have a significant impact on livestock living environment and other factors. In this paper, the method of computational fluid dynamics is used to analyze the distribution of the velocity field and temperature field within the fan imports and corridor export conditions of livestock and poultry breeding places. The results show that: the airflow in the vicinity of the air inlet fan speed larger maximum reach 6.09m / s, the wind speed is low in the other regions. In Breeding places, the air flow near the fan on both sides of the wall near vortex, the more the more obvious near the center of the vortex of the place. The temperature near fans inlet is significantly lower than that near the other regions. The research results will provide ventilation of livestock breeding places designed to provide a theoretical basis and guidance.
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Villagrán, Edwin, i Andrea Rodriguez. "Analysis of the Thermal Behavior of a New Structure of Protected Agriculture Established in a Region of Tropical Climate Conditions". Fluids 6, nr 6 (14.06.2021): 223. http://dx.doi.org/10.3390/fluids6060223.
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Determining airflow patterns and their effect on the distribution of microclimate variables such as temperature is one of the most important activities in naturally ventilated protected agricultural structures. In tropical countries, this information is used by farmers and decision makers when defining climate management strategies and for crop-specific cultural work. The objective of this research was to implement a validated Computational Fluid Dynamics (CFD) model in 3D to determine the aerodynamic and thermal behavior of a new protected agricultural structure established in a warm climate region in the Dominican Republic. The numerical evaluation of the structure was carried out for the hours of the daytime period (6–17 h), the results found allowed to define that the CFD model generates satisfactory predictions of the variables evaluated. Additionally, it was found that airflow patterns are strongly affected by the presence of porous insect screens, which generate moderate velocity flows (<0.73 m s−1) inside the structure. It was also identified that the value of the average temperature inside the structure is directly related to the air flows, the level of radiation and the temperature of the outside environment.
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Yang, Lin, Xiangdong Li i Jiyuan Tu. "Thermal comfort analysis of a high-speed train cabin considering the solar radiation effects". Indoor and Built Environment 29, nr 8 (18.09.2019): 1101–17. http://dx.doi.org/10.1177/1420326x19876082.
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Due to the fast development of high-speed rail (HSR) around the world, high-speed trains (HSTs) are becoming a strong competitor against airliners in terms of long-distance travel. Compared with airliner cabins, HST cabins have much larger window sizes. When the big windows provide better lighting and view of the scenery, they also have significant effects on the thermal conditions in the cabins due to the solar radiation through them. This study presents a numerical study on the solar radiation on the thermal comfort in a typical HST cabin. The effect of solar radiation was discussed in terms of airflow pattern, temperature distribution and thermal comfort indices. Parametric studies with seven different daytime hours were carried out. The effect of using the roller curtain was also studied. The overall cabin air temperature, especially near passengers, was found to have significantly increased by solar radiation. Passengers sitting next to windows were recorded to have an obvious thermal comfort variation at different hours of the day. To improve the passengers’ comfort and reduce energy consumption during hot weather, the use of a curtain could effectively reduce the solar radiation effect in the cabin environment.
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Hamdad, Hichem, Salah Larbi i Abdelkader Kessouri. "A Sensitivity Study of some Parameters on the Efficiency of a Passive Ventilation System Based on Solar Chimney". Applied Mechanics and Materials 393 (wrzesień 2013): 815–20. http://dx.doi.org/10.4028/www.scientific.net/amm.393.815.
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The purpose of this work is related to passive ventilation system analysis based on solar chimney. It consists in the determination of the temperature distributions of the wall, the glazing, and along the airflow in the chimney. The air mass flow rate and the instantaneous efficiency of the solar chimney were also determined. The energy performance of the solar chimney has been studied versus some geometrical and environmental parameters. The sensitivity study of the influence of some parameters on the efficiency of the system is also analysed. It is shown that the incident solar radiation has an important role on the energy performance of the solar chimney. Obtained results are compared to those of the literature. Good agreement is observed between the different results.
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Liu, Xiang-Long, Guang-Cai Gong, Heng-Sheng Cheng i Li-Xing Ding. "Airflow and Heat Transfer in the Slot-Vented Room with Radiant Floor Heating Unit". Journal of Applied Mathematics 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/287271.
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Radiant floor heating has received increasing attention due to its diverse advantages, especially the energy saving as compared to the conventional dwelling heating system. This paper presents a numerical investigation of airflow and heat transfer in the slot-vented room with the radiant floor heating unit. Combination of fluid convection and thermal radiation has been implemented through the thermal boundary conditions. Spatial distributions of indoor air temperature and velocity, as well as the heat transfer rates along the radiant floor and the outer wall, have been presented and analyzed covering the domains from complete natural convection to forced convection dominated flows. The numerical results demonstrate that the levels of average temperature in the room with lateral slot-ventilation are higher than those without slot-ventilation, but lower than those in the room with ceiling slot-ventilation. Overall, the slot-ventilation room with radiant floor heating unit could offer better indoor air quality through increasing the indoor air temperature and fresh air exchanging rate simultaneously. Concerning the airborne pollutant transports and moisture condensations, the performance of radiant floor heating unit will be further optimized in our future researches.
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Al-Amri, Fahad, i Tapas Kumar Mallick. "Effects of Nonuniform Incident Illumination on the Thermal Performance of a Concentrating Triple Junction Solar Cell". International Journal of Photoenergy 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/642819.
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A numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i) adding new receiver plate with higher surface area or (ii) using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy.
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Marinho, Liégina Silveira, Nathalia Parente de Sousa, Carlos Augusto Barbosa da Silveira Barros, Marcelo Silveira Matias, Luana Torres Monteiro, Marcelo do Amaral Beraldo, Eduardo Leite Vieira Costa, Marcelo Britto Passos Amato i Marcelo Alcantara Holanda. "Assessment of regional lung ventilation by electrical impedance tomography in a patient with unilateral bronchial stenosis and a history of tuberculosis". Jornal Brasileiro de Pneumologia 39, nr 6 (grudzień 2013): 742–46. http://dx.doi.org/10.1590/s1806-37132013000600013.
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Bronchial stenosis can impair regional lung ventilation by causing abnormal, asymmetric airflow limitation. Electrical impedance tomography (EIT) is an imaging technique that allows the assessment of regional lung ventilation and therefore complements the functional assessment of the lungs. We report the case of a patient with left unilateral bronchial stenosis and a history of tuberculosis, in whom regional lung ventilation was assessed by EIT. The EIT results were compared with those obtained by ventilation/perfusion radionuclide imaging. The patient was using nasal continuous positive airway pressure (CPAP) for the treatment of obstructive sleep apnea syndrome. Therefore, we studied the effects of postural changes and of the use of nasal CPAP. The EIT revealed heterogeneous distribution of regional lung ventilation, the ventilation being higher in the right lung, and this distribution was influenced by postural changes and CPAP use. The EIT assessment of regional lung ventilation produced results similar to those obtained with the radionuclide imaging technique and had the advantage of providing a dynamic evaluation without radiation exposure.
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Wang, Lie Zhun, i Zi Qing Liu. "Green Design and Manufacturing of Premium Efficiency Motor". Applied Mechanics and Materials 456 (październik 2013): 268–73. http://dx.doi.org/10.4028/www.scientific.net/amm.456.268.
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YE3 series of premium efficiency three-phase asynchronous motors adopt computer integrated system and anticipate the best optimized electrical design. In the structure design, airflow validity is analyzed by finite-element method (FEM) and the motors fan is designed optimally through experimental results; on the fan housing, the Ansoft finite-element method is used in analyzing the electromagnetic field , and designing optimally electromagnetic environment with the test results; the finite-element method is also used in analyzing the temperature field, connecting with the test results to optimize the ventilation structure. The radiating rib is metrical distribution and arrangement along the diameter of axle direction on the motor housing, following the principle of heat radiation and the principle of fluid mechanics, which can improve the ventilation and cooling effect. The design of the motor has reached the international advanced level.
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David, L. M., I. A. Girach i P. R. Nair. "Distribution of ozone and its precursors over Bay of Bengal during winter 2009: role of meteorology". Annales Geophysicae 29, nr 9 (20.09.2011): 1613–27. http://dx.doi.org/10.5194/angeo-29-1613-2011.
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Abstract. Measurements of ozone and NO2 were carried out in the marine environment of the Bay of Bengal (BoB) during the winter months, December 2008–January 2009, as part of the second Integrated Campaign for Aerosols, gases and Radiation Budget conducted under the Geosphere Biosphere Programme of the Indian Space Research Organization. The ozone mixing ratio was found to be high in the head and the southeast BoB with a mean value of 61 ± 7 ppb and 53 ± 6 ppb, respectively. The mixing ratios of NO2 and CO were also relatively high in these regions. The spatial patterns were examined in the light of airflow patterns, air mass back trajectories and other meteorological conditions and satellite retrieved maps of tropospheric ozone, NO2, CO, and fire count in and around the region. The distribution of these gases was strongly associated with the transport from the adjoining land mass. The anthropogenic activities and forest fires/biomass burning over the Indo Gangetic Plains and other East Asian regions contribute to ozone and its precursors over the BoB. Similarity in the spatial pattern suggests that their source regions could be more or less the same. Most of the diurnal patterns showed decrease of the ozone mixing ratio during noon/afternoon followed by a nighttime increase and a morning high. Over this oceanic region, photochemical production of ozone involving NO2 was not very active. Water vapour played a major role in controlling the variation of ozone. An attempt is made to simulate ozone level over the north and south BoB using the photochemical box model (NCAR-MM). The present observed features were compared with those measured during the earlier cruises conducted in different seasons.
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Belfegas, Billal, Salah Larbi i Tahar Tayebi. "Experimental and Theoretical Investigation on a Solar Chimney System for Ventilation of a Living Room". Mathematical Modelling of Engineering Problems 8, nr 2 (28.04.2021): 259–66. http://dx.doi.org/10.18280/mmep.080213.
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The present work relates to the analysis of an energy system based on the solar chimney for passive ventilation of a living space. It consists of an experimental and theoretical study of the energy performance according to some geometrical and environmental parameters. The designed prototype was installed and followed for several days. In parallel, a numerical code was developed in FORTRAN platform to simulate the phenomena in the solar chimney and compare the theoretical results with those experimental in the transient regime. The results obtained relate to the distributions of temperature on the glazing, within the airflow and on the internal wall of the chimney. The hourly rate of air change (ACH), the air-outlet velocity and its mass flow rate have also been determined. The comparison of the results obtained in this study with those of the literature has shown a good agreement. The obtained results have shown that the incidental solar radiation plays a fundamental role in the energy performance of such systems and there is an optimum value of the ratio between the width of the chimney and the wall opening for a high rate of air renewal.
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Herasymenko, Tetiana, Katerina Silchenko, Anna Hotvianska, Galyna Kyrsanova, Nina Budnyk, Alla Kainash, Lyudmila Polozhyshnikova i Iryna Taraymovich. "Design of an auger thermo-radiation dryer for drying plant-derived pomace". Eastern-European Journal of Enterprise Technologies 3, nr 1 (111) (10.06.2021): 62–69. http://dx.doi.org/10.15587/1729-4061.2021.232116.
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This paper reports the improved model design of an auger thermo-radiation dryer for drying plant-derived pomace under a low-temperature mode (35...80 °C) to the resulting moisture content at the level of 8...13 % of solids. The dryer has an adjustable speed of auger rotation (3...4 min–1), of airflow (0.05...0.09 m/s), and is characterized by the uniform distribution of heat flux. It is equipped with an energy-saving two-circuit complex that utilizes secondary energy to heat primary air from 21.1 °C to 28.9 °C. The use of Peltier elements, installed at the heating technical surface of the dryer's auger, makes it possible to convert thermal energy into a low-voltage supply voltage for the autonomous supercharger and exhaust fans. The duration of pomace drying in the model structure of the auger thermo-radiation dryer has been determined, in particular tomato pomace, with an initial content of 75 % of solids, which is 107 min. For apple pomace whose starting content of solids is 65 %, it is 98 min. For comparison, the duration of the convective drying of tomato pomace (75 % of solids) is 120 minutes. The drying was carried out at a temperature of 60 °C to the resulting moisture content of 10...12 % of solids. Organoleptic evaluation on the example of tomato pomace confirms the effectiveness of structural solutions in the auger dryer compared to the convective technique. The results reported in this study could create conditions for the further design and implementation of the proposed structure of thermo-radiation dryer for drying plant-derived pomace involving an altered heat supply technique and the utilization of secondary energy. The designed structure of the device makes it possible to process and preserve the quality properties of plant-derived pomace, allowing the use of this product for a wide range of foodstuffs
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Jalal M. Jalil, Jalal M. Jalil. "CFD Simulation for a Road Vehicle Cabin". journal of King Abdulaziz University Engineering Sciences 18, nr 2 (1.01.2007): 129–48. http://dx.doi.org/10.4197/eng.18-2.7.
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A numerical study of a two-dimensional, turbulent, recirculating flow within a passenger car cabin is presented. The study is based on the solution of the elliptic partial differential equations representing conservation of mass, momentum, temperature, turbulence energy and its dissipation rate in finite volume form. Algebraic expressions for the turbulent viscosity and diffusion coefficients are calculated using the two-equation model(k − ε). Different parameters are considered to illustrate their influences on the flow filed and temperature distribution inside car cabin. These parameters include number and location of the air conditioning systems inlets inside car cabin, different air temperatures at the inlets, different air velocities at the inlets, different solar intensity during day-time for a certain day of the year, different diffuse solar radiation (variation in the kind of car glass). Generally, the results indicate some of negative effects such as development of zones of low air circulation. Also it is found that the number of inlets inside car cabin play an important role in determining car air conditioning system efficiency. Moreover, the air temperature and velocity at inlets play an important role in determining cabin climate. The results are used to enhance the understating of the airflow fields within a road vehicle passenger cabin.
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Jadallah, Abdullateef A., Mohammed K. Alsaadi i Saeef A. Hussien. "The hybrid (PVT) double-pass system with a mixed-mode solar dryer for drying banana". Engineering and Technology Journal 38, nr 8A (25.08.2020): 1214–25. http://dx.doi.org/10.30684/etj.v38i8a.535.
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In this paper, the hybrid PVT double pass system with a mixed-mode solar dryer type under forced convection has been designed, fabricated and installed for drying crops. The dryer was tried by drying 300 grams of banana slices in the air temperature of dryer range from 43.2 to 60.2°C. The initial moisture rate of banana was about 78% and the most dropped in moisture content was from 78% to 33% after 8 hours of the drying process. The banana slices are distributed in two identical trays and it was noticed that the most and least decreasing in weight of banana samples was from 150 to 48 gram and from 150 to 55 gram in lower and upper tray respectively, when the mass flow rate as 0.031 and 0.017 kg/s, which means that the high reduction was 68% of weight banana at a high mass flow rate of airflow. The critical parameter such as temperature distribution of the PVT with dryer room, useful heat gain, and thermal efficiency are computed by using the MATLAB 2015b program built for this purpose. The optimum useful heat gain and thermal efficiency were reached 423.7 and 52.98% respectively when the solar radiation 1190 and the mass flow rate of 0.031 kg/s.
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Salma, Imre, Zoltán Németh, Tamás Weidinger, Boldizsár Kovács i Gergely Kristóf. "Measurement, growth types and shrinkage of newly formed aerosol particles at an urban research platform". Atmospheric Chemistry and Physics 16, nr 12 (27.06.2016): 7837–51. http://dx.doi.org/10.5194/acp-16-7837-2016.
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Abstract. Budapest platform for Aerosol Research and Training (BpART) was created for advancing long-term on-line atmospheric measurements and intensive aerosol sample collection campaigns in Budapest. A joint study including atmospheric chemistry or physics, meteorology, and fluid dynamics on several-year-long data sets obtained at the platform confirmed that the location represents a well-mixed, average atmospheric environment for the city centre. The air streamlines indicated that the host and neighbouring buildings together with the natural orography play an important role in the near-field dispersion processes. Details and features of the airflow structure were derived, and they can be readily utilised for further interpretations. An experimental method to determine particle diffusion losses in the differential mobility particle sizer (DMPS) system of the BpART facility was proposed. It is based on CPC–CPC (condensation particle counter) and DMPS–CPC comparisons. Growth types of nucleated particles observed in 4 years of measurements were presented and discussed specifically for cities. Arch-shaped size distribution surface plots consisting of a growth phase followed by a shrinkage phase were characterised separately since they supply information on nucleated particles. They were observed in 4.5 % of quantifiable nucleation events. The shrinkage phase took 1 h 34 min in general, and the mean shrinkage rate with standard deviation was −3.8 ± 1.0 nm h−1. The shrinkage of particles was mostly linked to changes in local atmospheric conditions, especially in global radiation and the gas-phase H2SO4 concentration through its proxy, or to atmospheric mixing in few cases. Some indirect results indicate that variations in the formation and growth rates of nucleated particles during their atmospheric transport could be a driving force of shrinkage for particles of very small sizes and on specific occasions.
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Fitch, Kyle E., Chaoxun Hang, Ahmad Talaei i Timothy J. Garrett. "Arctic observations and numerical simulations of surface wind effects on Multi-Angle Snowflake Camera measurements". Atmospheric Measurement Techniques 14, nr 2 (12.02.2021): 1127–42. http://dx.doi.org/10.5194/amt-14-1127-2021.
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Abstract. Ground-based measurements of frozen precipitation are heavily influenced by interactions of surface winds with gauge-shield geometry. The Multi-Angle Snowflake Camera (MASC), which photographs hydrometeors in free-fall from three different angles while simultaneously measuring their fall speed, has been used in the field at multiple midlatitude and polar locations both with and without wind shielding. Here, we present an analysis of Arctic field observations – with and without a Belfort double Alter shield – and compare the results to computational fluid dynamics (CFD) simulations of the airflow and corresponding particle trajectories around the unshielded MASC. MASC-measured fall speeds compare well with Ka-band Atmospheric Radiation Measurement (ARM) Zenith Radar (KAZR) mean Doppler velocities only when winds are light (≤5ms-1) and the MASC is shielded. MASC-measured fall speeds that do not match KAZR-measured velocities tend to fall below a threshold value that increases approximately linearly with wind speed but is generally <0.5ms-1. For those events with wind speeds ≤1.5ms-1, hydrometeors fall with an orientation angle mode of 12∘ from the horizontal plane, and large, low-density aggregates are as much as 5 times more likely to be observed. Simulations in the absence of a wind shield show a separation of flow at the upstream side of the instrument, with an upward velocity component just above the aperture, which decreases the mean particle fall speed by 55 % (74 %) for a wind speed of 5 m s−1 (10 m s−1). We conclude that accurate MASC observations of the microphysical, orientation, and fall speed characteristics of snow particles require shielding by a double wind fence and restriction of analysis to events where winds are light (≤5ms-1). Hydrometeors do not generally fall in still air, so adjustments to these properties' distributions within natural turbulence remain to be determined.
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Liang, Chao, Arsen Krikor Melikov i Xianting Li. "The influence of heat source distribution on the space cooling load oriented to local thermal requirements". Indoor and Built Environment, 3.12.2019, 1420326X1989163. http://dx.doi.org/10.1177/1420326x19891632.
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Existing studies have shown that the space cooling load oriented to local thermal requirements is significantly influenced by different heat source distributions. However, numerical methods have been mainly used in the analysis based on a fixed airflow field and ignoring the thermal plume. Here, an experiment in a chamber with mixing ventilation was conducted. The heat sources were simulated by metal barrels and an oil-filled radiator, 13 types of heat source distributions were designed and the local cooling load (LCL) was used as the evaluation index. The results show that (1) the LCL is equal to the total amount of heat sources at the steady state in a room with mixing ventilation only if the heat sources are also distributed uniformly; (2) the LCL decreases with a decrease in the intensity of heat sources, achieving a decrease rate of 47.4%–70.8% in the experiment with different intensities; (3) the LCL is 9.2%–22.3% lower than the total amount of heat sources when these are located near the exhaust diffuser or far away from the target zone; (4) owing to its smaller surface area, the LCL with an oil-filled radiator is 7% lower than that with five metal barrels.
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Swanson, Larry W., i David K. Moyeda. "A Thermal Model for Concentric-Tube Overfire Air Ports". Journal of Thermal Science and Engineering Applications 1, nr 1 (1.03.2009). http://dx.doi.org/10.1115/1.3159524.
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A quasisteady multimode heat-transfer model for boiler concentric-tube overfire air ports has been developed that predicts the effect of geometry, furnace heat source and heat sink temperatures, axial injector wall conduction, and coolant flow rate on the tube wall temperature distributions. The model imposes a radiation boundary condition at the outlet tip of the ports, which acts as a heat source. The model was validated using field data and showed that both the airflow distribution in the ports and tube diameter can be used to control the maximum tube wall temperature. This helps avoid tube overheating and thermal degradation. For nominal operating conditions, highly nonlinear axial temperature distributions were observed in both tubes near the hot outlet end of the port.
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Talaat, Khaled, Jinxiang Xi, Phoenix Baldez i Adam Hecht. "Radiation Dosimetry of Inhaled Radioactive Aerosols: CFPD and MCNP Transport Simulations of Radionuclides in the Lung". Scientific Reports 9, nr 1 (25.11.2019). http://dx.doi.org/10.1038/s41598-019-54040-1.
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AbstractDespite extensive efforts in studying radioactive aerosols, including the transmission of radionuclides in different chemical matrices throughout the body, the internal organ-specific radiation dose due to inhaled radioactive aerosols has largely relied on experimental deposition data and simplified human phantoms. Computational fluid-particle dynamics (CFPD) has proven to be a reliable tool in characterizing aerosol transport in the upper airways, while Monte Carlo based radiation codes allow accurate simulation of radiation transport. The objective of this study is to numerically assess the radiation dosimetry due to particles decaying in the respiratory tract from environmental radioactive exposures by coupling CFPD with Monte Carlo N-Particle code, version 6 (MCNP6). A physiologically realistic mouth-lung model extending to the bifurcation generation G9 was used to simulate airflow and particle transport within the respiratory tract. Polydisperse aerosols with different distributions were considered, and deposition distribution of the inhaled aerosols on the internal airway walls was quantified. The deposition mapping of radioactive aerosols was then registered to the respiratory tract of an image-based whole-body adult male model (VIP-Man) to simulate radiation transport and energy deposition. Computer codes were developed for geometry visualization, spatial normalization, and source card definition in MCNP6. Spatial distributions of internal radiation dosimetry were compared for different radionuclides (131I, 134,137Cs, 90Sr-90Y, 103Ru and 239,240Pu) in terms of the radiation fluence, energy deposition density, and dose per decay.
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Seytier, Charline, i Mohammad H. Naraghi. "Combined Convective-Radiative Thermal Analysis of an Inclined Rooftop Solar Chimney". Journal of Solar Energy Engineering 135, nr 1 (9.08.2012). http://dx.doi.org/10.1115/1.4007090.
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A model for the combined spectral radiative and convective heat transfer analysis of solar chimneys is developed. The radiation part of this model is based on the spectral distribution of the solar heat flux and spectral radiative properties of solar chimney components. Two approaches are used for the convective part of this model, empirical correlations and a CFD analysis. The empirical correlations are based on the stack effect correlation for airflow motion and a convective heat transfer correlation for the heat transfer coefficient. The empirical correlations are used to obtain an initial estimation of surface temperatures, which are then used in the CFD model to determine an improved estimation of the heat transfer coefficients and airflow rate. Iterating between the spectral radiative and the CFD models resulted in a converged set of values for the solar chimney airflow rate and its thermal characteristics. The model is used to predict the airflow rate for various configurations and solar irradiances of solar chimneys.
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TEMELJKOVSKI, DRAGANA. "AN EXPERIMENTAL VERIFICATION OF INFLUENCING FACTORS ON THE MECHANISM OF HEAT TRANSFER IN THE CAVITY ROOF VENTILATION". Safety Engineering 5, nr 2 (13.12.2015). http://dx.doi.org/10.7562/se2015.5.02.02.
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The roof, as a part of the building envelope with the thermal performance that’s a major requirement for guaranteeing a comfortable and hygienic interior climate, provides protection from thermal damage incurred by the sun. To improve this protection ability, the use of a ventilated roof can be considered, which has a ventilation layer known as a cavity, beneath the roof cover panel. Based on the proposed mechanism of heat transfer and the influence of such factors as cavity ventilation, the slope of the roof, intensity of solar radiation, the size and shape of the cavity, and panel profiles, airflow and temperature distribution are analyzed in the cavity, in an effort to improve the cooling effect of ventilation in the cavity of the roof. In this study, the influence of these elements on airflow is studied. Key words: temperature distribution, cooling effect, air flow, thermal comfort, ventilation channel.
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Li, Wang, Hanqing Wang, Chengjun Li i Chuck Wah Yu. "Control of temperature and fume generation by cooking in a residential kitchen by ceiling radiative cooling and fume hood extraction". Indoor and Built Environment, 26.08.2020, 1420326X2094575. http://dx.doi.org/10.1177/1420326x20945750.
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The heat radiation in a residential kitchen was simulated by CFD (Computational-fluid-dynamics) to evaluate the cooling by a radiant cooling ceiling panel and pollution dispersion by the range hood and the air extraction system. The kitchen has a 2-hobs stove and a fume hood for removing waste heat and fumes. The simulation was validated by measurements in a domestic kitchen in a home in Changsha, China, where summer temperature is generally about 33 °C and often over 35–42°C. The simulation results show that the pollutant concentration in the kitchen during cooking was much lower than the Chinese standard criteria of GB/T18883-2002. A standard turbulence model was used, which indicated satisfactory distribution of temperature and airflow in the kitchen. The indoor airflow velocity was low. The airflow temperature when both hobs were used was slightly higher by 3–4°C than when a single hob was used. The temperature in the kitchen during cooking was about 28 °C, which was a degree lower than the living-room temperature, thus maintaining a comfortable thermal and healthy environment. The radiant cooling in the ceiling was shown to be a significant contributing factor. The ring suction type range hood has a sufficient capacity to remove the kitchen fume contaminants.