Experimental and CFD Investigation of a Modified Uneven-Span Greenhouse Solar Dryer in No-Load Conditions under Natural Convection Mode

An uneven-span modified greenhouse dryer was constructed and tested in no-load conditions under natural convection mode under the weather conditions of Marrakech, Morocco, for two distinct days. Moreover, a CFD evaluation of the uneven-span greenhouse dryer was performed as tool to visualize the air temperature distribution inside the dryer. For validating the CFD model, the temperature variations along the hours of the day were compared to the experimental results. A good agreement is obtained between the computed and measured inside air temperature with a difference not exceeding 8.46°C, with a correlation coefficient ( r ) and root mean square percentage deviations ( e ) 0.94 and 8.17, respectively. Furthermore, the maximum inside air temperature was measured to be 56°C and 52°C while the minimum inside relative humidity was measured to be 17% and 12%, for day-1 and day-2, respectively. The benefice of using asphalt as a floor covering material was revealed as an efficient way to heat the inside air at low solar radiations. The performances of the dryer were evaluated by the percentage of net heat gain variation as a way to validate the effectiveness of the dryer. This latter is found to be equal to 46% and 48% for the two days, respectively.

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The Effect of Tree-Planting Patterns on the Microclimate within a Courtyard

Sustainability ◽

10.3390/su11061665 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1665 ◽

Cited By ~ 2

Author(s):

Junying Li ◽

Jiying Liu ◽

Jelena Srebric ◽

Yuanman Hu ◽

Miao Liu ◽

...

Keyword(s):

Air Temperature ◽

Local Heat Transfer ◽

Field Measurements ◽

Weather Conditions ◽

Local Heat ◽

Tree Planting ◽

Cfd Model ◽

Planting Pattern ◽

Wind Velocities ◽

Computational Fluid Dynamics Cfd

Current landscape design within a courtyard usually does not take into account the influence of the tree-planting pattern, which has an important influence on the outdoor microclimate and occupants’ thermal comfort. At present, the extent of the influence on the microclimate has not yet been made clear. Computational Fluid Dynamics (CFD) was employed to run this model under hot summer weather conditions. Field measurements validated the performance of the CFD model. This study conducted numerical simulations for five different tree-planting patterns, including (i) focused tree-planting (F), (ii) cornered tree-planting (C), (iii) multi-row tree-planting (R), (iv) surround tree-planting (S) and (v) no tree-planting (N). Our study found that the tree-planting pattern affects both the distribution of air temperature and the degree of local heat transfer. Specifically, the C, S and N patterns allow for higher ventilation in the studied courtyard, while the F and R patterns cause lower wind velocities and associated courtyard ventilation. The average air temperature for the C pattern is lower during summer afternoons than the other patterns. The wind flow pattern in the studied courtyard does not vary significantly with different tree-planting patterns. Nevertheless, the general relative humidity in the courtyard does not vary significantly with different tree-planting patterns, except for the N pattern. A future analysis is needed to investigate the mechanisms of the phenomenon.

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CuO–Water Nanofluid Magnetohydrodynamic Natural Convection inside a Sinusoidal Annulus in Presence of Melting Heat Transfer

Mathematical Problems in Engineering ◽

10.1155/2017/5830279 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9 ◽

Cited By ~ 11

Author(s):

M. Sheikholeslami ◽

R. Ellahi ◽

C. Fetecau

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Natural Convection ◽

Hartmann Number ◽

Volume Fraction ◽

Melting Heat ◽

Melting Heat Transfer ◽

Limiting Case ◽

Good Agreement ◽

Melting Parameter

Impact of nanofluid natural convection due to magnetic field in existence of melting heat transfer is simulated using CVFEM in this research. KKL model is taken into account to obtain properties of CuO–H2O nanofluid. Roles of melting parameter (δ), CuO–H2O volume fraction (ϕ), Hartmann number (Ha), and Rayleigh (Ra) number are depicted in outputs. Results depict that temperature gradient improves with rise of Rayleigh number and melting parameter. Nusselt number detracts with rise of Ha. At the end, a comparison as a limiting case of the considered problem with the existing studies is made and found in good agreement.

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A reflexion on the environmental effect on the transmission of COVID-19

10.5194/egusphere-egu21-10284 ◽

2021 ◽

Author(s):

Victor L Barradas ◽

Monica Ballinas

Keyword(s):

Solar Radiation ◽

Air Temperature ◽

Low Temperatures ◽

Minimum Distance ◽

Vapor Pressure Deficit ◽

Environmental Parameters ◽

Air Humidity ◽

Evaporative Demand ◽

Small Water ◽

The Hours

This research is a general reflection of the possible transmission not only of COVID-19 but of any influenza disease depending on environmental parameters such as solar radiation, air humidity and air temperature (vapor pressure deficit), evoking the Penman-Monteith model regarding the evaporation of the water that constitutes the small water droplets (aerosols) that carry the virus. In this case the evapotranspiration demand of the atmosphere with which it can be deduced that the spread of the disease will be higher in those places with less evaporative demand, that is, high air humidity and / or low temperatures, and / or low radiation intensities, and vice versa. It can also be deduced that the hours of greatest potential contagion are the night hours, while those with the lowest risk are between 2:00 p.m. and 4:00 p.m. On the other hand, in those rooms with low temperatures the contagion would be more effective. So, considering that the drops produced by a sneeze, by speaking or breathing can go beyond two meters away, it is roughly explained that the use of face masks and keeping a safe minimum distance of two meters can limit transmission of viruses and / or infections. However, this practice is not entirely safe as the environment can play an important role. What is recommended to reduce the spread of these pathogens is to produce high evaporative demands: increasing solar radiation, and increasing air temperature and reducing air humidity, which is practice that can be effective in closed rooms.

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Indoor Air Quality (IAQ): Accuracy of Natural Ventilation for Temperature, Air Flow Rate and Relative Humidity (RH) in School Building Classrooms

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.9.15271 ◽

2018 ◽

Vol 7 (3.9) ◽

pp. 42

Author(s):

Norsafiah Norazman ◽

Adi Irfan Che Ani ◽

Nor Haslina Ja’afar ◽

Muhamad Azry Khoiry

Keyword(s):

Air Quality ◽

Relative Humidity ◽

Indoor Air Quality ◽

Indoor Air ◽

Natural Ventilation ◽

Air Flow ◽

Weather Conditions ◽

Potential Health ◽

The Hours ◽

Hot Weather

Indoor Air Quality (IAQ) is an essential matter in achieving students’ satisfaction for the learning process. Building’s orientation is a factor that may encourage sufficient natural ventilation for the classroom occupants. Inadequate ventilation is an issue for most existing classrooms. The purpose of this paper is to analyze the accuracy of natural ventilation in classrooms. Therefore, experimental on 20 classrooms has been conducted by using Multipurpose Meter at secondary school buildings in Malaysia. The findings indicated that the accuracy of natural ventilation testing was below the permissible limits throughout the hours monitored, thus this may cause potential health hazards to the students. Temperature and air flow rates were lower than 23 °C and 0.15 m/s respectively, it fulfilled the basic requirements as a standard learning environment. However, measurements taken showed the overall relative humidity (RH) in the classrooms can be categorized as acceptable with 40% to 70% range. On the basis of these findings, it is evident that naturally ventilated classrooms are important especially due to energy efficiency, whereas mechanical ventilation should only be installed as an alternative under extremely hot weather conditions.

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Natural Convection from a Horizontal Cylinder—Laminar Regime

Journal of Heat Transfer ◽

10.1115/1.3244495 ◽

1981 ◽

Vol 103 (3) ◽

pp. 522-527 ◽

Cited By ~ 81

Author(s):

B. Farouk ◽

S. I˙. Gu¨c¸eri

Keyword(s):

Natural Convection ◽

Horizontal Cylinder ◽

Heat Transfer Characteristics ◽

Convective Flows ◽

Finite Difference Numerical Method ◽

Temperature Boundary ◽

Recirculation Zones ◽

Boussinesq Fluid ◽

Temperature Boundary Condition ◽

Good Agreement

A finite-difference numerical method has been adopted to generate flow patterns and heat transfer characteristics for laminar, steady-state, two-dimensional natural convection around a circular cylinder submerged in an unbounded Boussinesq fluid. The approach allows the use of nonuniform as well as uniform specified temperature and heat flux distributions over the cylindrical surface. Part of the results are generated for reverse convective flows with recirculation zones which occur when part of the cylinder is below the ambient temperature while the remaining part is above. The results for uniform temperature boundary condition are in good agreement with the experimental data and other solutions available in literature.

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A Meshfree Method for Heat Explosion Problems with Natural Convection in Inclined Porous Media

MATEC Web of Conferences ◽

10.1051/matecconf/201824101019 ◽

2018 ◽

Vol 241 ◽

pp. 01019 ◽

Cited By ~ 1

Author(s):

Abdoulhafar Halassi ◽

Youssef Joundy ◽

Loubna Salhi ◽

Ahmed Taik

Keyword(s):

Porous Media ◽

Natural Convection ◽

Vertical Direction ◽

Meshfree Method ◽

Boussinesq Approximation ◽

Complex Behaviour ◽

Meshless Collocation ◽

Darcy Equations ◽

Small Inclination ◽

Good Agreement

This paper investigates the interaction between natural convection and heat explosion in porous media. A meshless collocation method based on multiquadric radial basis functions has been applied to study the problem in an inclined two-dimensional porous media. The governing equations consist of coupling the Darcy equations in the Boussinesq approximation of low density variations to the heat equation with a nonlinear chemical source term. The numerical results obtained are in good agreement with some previous studies that consider the vertical direction. A complex behaviour of solutions is observed, including periodic and aperiodic oscillations. We have shown that a small inclination of the container stabilizes the reactive fluid and can prevent thermal explosion.

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Modelling pavement temperature for winter maintenance operations

Canadian Journal of Civil Engineering ◽

10.1139/l03-107 ◽

2004 ◽

Vol 31 (2) ◽

pp. 369-378 ◽

Cited By ~ 8

Author(s):

Aly Sherif ◽

Yasser Hassan

Keyword(s):

Surface Temperature ◽

Air Temperature ◽

Negative Impact ◽

Weather Conditions ◽

Statistical Modelling ◽

Dew Point ◽

Road Maintenance ◽

Winter Maintenance ◽

Pavement Surface ◽

Pavement Temperature

Road and highway maintenance is vital for the safety of citizens and for enabling emergency and security services to perform their essential functions. Accumulation of snow and (or) ice on the pavement surface during the wintertime substantially increases the risk of road crashes and can have negative impact on the economy of the region. Recently, road maintenance engineers have used pavement surface temperature as a guide to the application of deicers. Stations for road weather information systems (RWIS) have been installed across Europe and North America to collect data that can be used to predict weather conditions such as air temperature. Modelling pavement surface temperature as a function of such weather conditions (air temperature, dew point, relative humidity, and wind speed) can provide an additional component that is essential for winter maintenance operations. This paper uses data collected by RWIS stations at the City of Ottawa to device a procedure that maximizes the use of a data batch containing complete, partially complete, and unusable data and to study the relationship between the pavement surface temperature and weather variables. Statistical models were developed, where stepwise regression was first applied to eliminate those variables whose estimated coefficients are not statistically significant. The remaining variables were further examined according to their contribution to the criterion of best fit and their physical relationships to each other to eliminate multicollinearities. The models were further corrected for the autocorrelation in their error structures. The final version of the developed models may then be used as a part of the decision-making process for winter maintenance operations.Key words: winter maintenance, pavement temperature, statistical modelling, RWIS.

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When, where and why do people encounter Australian brownsnakes (Pseudonaja textilis : Elapidae)?

Wildlife Research ◽

10.1071/wr98043 ◽

1999 ◽

Vol 26 (5) ◽

pp. 675 ◽

Cited By ~ 11

Author(s):

P. B. Whitaker ◽

R. Shine

Keyword(s):

Air Temperature ◽

Agricultural Land ◽

New South ◽

Habitat Type ◽

Weather Conditions ◽

Time Of Day ◽

South Wales ◽

Experienced Observer ◽

Close Proximity ◽

Species Ecology

Encounters between humans and dangerously venomous snakes put both participants at serious risk, so the determinants of such encounters warrant attention. Pseudonaja textilis is a large fast-moving elapid snake responsible for most snakebite fatalities in Australia. As part of a broad ecological study of this species in agricultural land near Leeton, New South Wales, we set out to identify factors influencing the probability that a human walking in farmland would come into close proximity to a brownsnake. Over a three-year period, we walked regular transects to quantify the number and rate of snake encounters, and the proportion of snakes above ground that could be seen. The rate of encounters depended upon a series of factors, including season, time of day, habitat type, weather conditions (wind and air temperature) and shade (light v. dark) of the observers’ clothing. Interactions between factors were also important: for example, the effect of air temperature on encounter probability differed with season and snake gender, and the effect of the observers’ shade of clothing differed with cloud cover. Remarkably, even a highly-experienced observer actually saw <25% of the telemetrically monitored snakes that were known to be active (i.e. above ground) nearby. This result reflects the snakes’ ability to evade people and to escape detection, even in the flat and sparsely vegetated study area. The proportion of snakes that were visible was influenced by the same kinds of factors as described above. Most of the factors biasing encounter rates are readily interpretable from information on other facets of the species’ ecology, and knowledge of these factors may facilitate safer coexistence between snakes and people.

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Cars as next generation mobile weather stations: an initial investigation

10.5194/ems2021-290 ◽

2021 ◽

Author(s):

Giuliano Andrea Pagani ◽

Marcel Molendijk ◽

Jan Willem Noteboom

Keyword(s):

Air Temperature ◽

Weather Conditions ◽

Ground Temperature ◽

Warning Systems ◽

Traction Control ◽

The Future ◽

Weather Stations ◽

Temporal And Spatial ◽

Positive Correlation Coefficient ◽

Digital Equipment

Modern automobiles are becoming more and more &#8220;computers on the wheels&#8221; having lots of digital equipment on board. Such equipment is both for the comfort and entertainment of the passengers and for their safety. Sensors play a key role in measuring several parameters of the car performance (e.g., traction control, anti-lock breaking system) and also environmental &#160;parameters are observed directly (e.g., air temperature) or can be somehow inferred (e.g., precipitation via windscreen wipers activity/speed).KNMI has been provided air temperature recorded every 10 minutes by thousands of vehicles driving in the Netherlands for the period January-October 2020. We have performed an initial exploratory temporal and spatial analysis to understand the most promising periods of the day and areas where sufficient data is available to perform a more thorough data analysis in the future. Furthermore, we have performed a correlation analysis between the outside temperature measured by cars and air and ground temperature observed by official weather station sensors placed at one location on the Dutch highways. The correlation results for three randomly selected days (with different weather conditions) show a good positive correlation coefficient ranging from 0.93 to 0.76 for car and station air temperature and from 0.91 to 0.67 for car temperature and station ground temperature.This initial exploration paves the way to the use of (OEM) car data as (mobile) weather stations. We foresee in the future to use a combination of sensed variables from cars such as air temperature, traction control, windscreen wipers activity for example to improve observations of road slipperiness and related warning systems that are not restricted to Dutch highways only.

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Identification of solar radiation effect on climatic indicators of the territory of Ukraine

Geology Geography Ecology ◽

10.26565/2410-7360-2018-49-12 ◽

2018 ◽

Keyword(s):

Solar Radiation ◽

Solar Energy ◽

Air Temperature ◽

Temperature Regime ◽

Atmospheric Pressure ◽

Weather Conditions ◽

Climatic Conditions ◽

Practical Significance ◽

Statistical Dependence ◽

Physical Processes

Formulation of the problem. Understanding that solar energy is the main source of the majority of biological, chemical and physical processes on Earth, investigation of its influence on different climatic fields allows us to define the features of its space and hour fluctuations. To define radiation and temperature regime of the territory it is necessary to determine climatic features of the spreading surface, which absorbs and will transform solar energy. Considering the fact that modern climatic changes and their consequences cover all components of the system, today there is a problem of their further study for comprehension of atmospheric processes, modeling weather conditions on different territories depending on the properties. The purpose of the article is to determine interrelations between indexes of solar radiation (the Wolf's number) and air temperature, atmospheric pressure on the territory of Ukraine during 1965-2015, their change in space and time. Methods. Correlative method is one of the main methods of a statistical analysis which allows us to receive correlation coefficients of solar radiation variability indexes, air temperature, atmospheric pressure on the territory of the research. This technique estimates the extent of solar radiation influence on temperature regime of the territory and distribution of atmospheric pressure. Results. Coefficients of correlation, which characterize variability of solar radiation indexes, air temperature and atmospheric pressure on the explored territory have been received by means of statistical correlation analysis method. This technique allows us to estimate the degree and nature of solar radiation influence on a temperature regime of the territory and distribution of atmospheric pressure. It has been defined that direct correlative connection between indexes of solar radiation is characteristic of air temperature and atmospheric pressure fields. Significant statistical dependence between incoming solar radiation on the territory of Ukraine and atmospheric pressure has been noted during the spring and autumn periods mainly at the majority of stations. Between indexes of solar radiation and air temperature the inverse correlative connection in winter will be transformed to a direct connection during the spring and summer periods. Scientific novelty and practical significance. Physical processes, which happen in the atmosphere, are characterized by complex interrelations. For further research it is important to define solar radiation value and the extent of influence on climatic conditions.

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