The effect of ventilator configurations in naturally ventilated greenhouse applications

In this paper the climate inside a greenhouse subject to various vent configurations is investigated. The greenhouse considered is a four span glass greenhouse, containing a plastic partition separating the greenhouse into two compartments. The temperature and velocity distribution at plant level is numerically analyzed with computational fluid dynamics. Six cases were considered. The first three cases have the roof vents open to the leeward side, while the side ventilators are opened at 30° and 45° respectively, after which a second row of side ventilators opened at 45° were added to the geometry. The last three cases have the roof vents open towards the windward side, with the same side ventilator configuration as mentioned for the first three simulations. Contour plots for both temperature and velocity are discussed and analyzed. Results seem to indicate that the temperature and velocity at plant level are significantly influenced by the arrangement and number of vents. The presence of a plastic partition also has an effect on the climate. The temperature in the east span of the greenhouse is slightly higher for the leeward ventilators compared to the windward roof ventilators, and the temperature distribution is also less homogeneous if the roof ventilators are opened leeward. The velocity distribution in the west span for leeward roof ventilators are higher compared to windward ventilators, and also less homogeneous. Comparing the velocity distribution in the east span for both leeward and windward roof ventilators, the results show an increase in air movement for the east span of the greenhouse. It is also shown that CFD can be a useful tool in development and design of greenhouses

The effect of raised benches containing crops on the indoor environment in greenhouses

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investigate the influence of o investigate the influence of o investigate the influence of o investigate the influence of o investigate the influence of o investigate the influence of o investigate the influence of peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the peninsular arranged perforated benches containing plants on the indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse indoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouseindoor environment of a naturally ventilated greenhouse. The The The The results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular results are compared to a greenhouse containing peninsular arranged solid bench arranged solid bencharranged solid bench arranged solid bencharranged solid bench arranged solid bencharranged solid bencharranged solid bencharranged solid bench arranged solid bencharranged solid bencharranged solid bench arranged solid bencharranged solid benches with no plants. es with no plants.es with no plants.es with no plants. es with no plants.es with no plants.es with no plants.es with no plants.es with no plants.es with no plants.es with no plants.es with no plants. es with no plants.es with no plants.es with no plants. 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Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. Fluid Dynamics (CFD) models. The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and The overall temperature and velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of velocity distribution were investigated at different sections of the greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatu the greenhouse. The temperatuthe greenhouse. The temperatuthe greenhouse. The temperature and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity re and velocity distributionsdistributionsdistributionsdistributionsdistributionsdistributionsdistributionsdistributionsdistributions distributionsdistributions at at at plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the plant level were of particular interest. Results indicated that the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the greenhouse containing the perforated perforated perforated perforated perforated perforated perforated perforated perfo

The effect of bench arrangements on the indoor climate of naturally ventilated greenhouses

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Greenhouses are used worldwide to effectively produce crops and flowers out of season by protecting them from adverse environmental factors [2]. High inputs (water, nutrients, plant protection chemicals, handling material and fossil energy) are required for this method of production, which may unfortunately lead to environmental problems [3]. Due to an increased interest in reducing energy consumption, natural ventilation has become a popular alternative method to control the indoor climate of greenhouses. Effective control of the indoor climate of greenhouses is of vital importance, as this directly influences the quality and quantity of the crop production. The purpose of this paper is to investigate the effect of bench arrangements on the internal environment in naturally ventilated Venlo-type greenhouses. The study will be conducted numerically, using computational fluid dynamics (CFD). Two-dimensional models will be created and a mesh sensitivity study will be conducted to determine a suitable mesh size. The effect of various bench arrangements used commonly in industry on the temperature and velocity distributions inside the greenhouses will be assessed. The case of a heated floor will be examined, with single, double and triple solid bench arrangements. A three-dimensional double span greenhouse will also be created containing four longitudinally arranged benches, and compared to a corresponding two-dimensional model. It was found that overall the wind direction and bench arrangements do have a significant effect on the microclimate at plant level, creating large velocity and temperature differences between the various bench arrangements.mp201

Technology diffusion and forecasting : the case of computational fluid dynamics (CFD) for simulation of greenhouse internal environments

Forecasting emerging technologies as well as rate of diffusion of resultant products are complex in the context of management of technology usually because of a lack of relevant data. Techniques such as bibliometric analysis and the Bass diffusion model are utilized in this paper to assess the growth rate and market penetration of Computational Fluid Dynamics (CFD) as a technology. The penetration and growth rate of user acceptance to two CFD codes (not identified) are simulated. Furthermore a technology forecasting model of research and innovation in the field of application of CFD in the assessment of greenhouses is presented. Some CFD results of simulations for internal and external flow in an eight span greenhouse are presented as illustration of the power of CFD as technology.http://www.worldscinet.com/ijitm/ai201

A numerical evaluation of multi-dimensional heat transfer effects in greenhouses

Abstract: Greenhouses are used extensively in both agricultural and horticultural industries. Cultivating crops in greenhouses is an energy-intensive process, especially as far as ventilation is concerned. The use of natural ventilation as an alternative to control the indoor climate of greenhouses has become increasingly popular. Natural ventilation in greenhouses is due to the air exchange process between the internal and external environment of the greenhouse mainly due to thermal buoyancy and wind-induced forces. The main objective of this thesis is to determine the effect of dimensional and geometrical influences on the heat transfer characteristics of greenhouses using Computational Fluid Dynamics. This entails an investigation into the effect of geometric design changes on the thermal and flow performance of greenhouses due to buoyancy driven flow. The study also includes a numerical investigation into the effect of plant benches on the indoor climate of greenhouses. This thesis commences with a review of the available literature, and identified areas in the research that require more attention. A background on the numerical tool used (Computational Fluid Dynamics) was given, as well as a background on the experimental methods used in this thesis. In this research study, the investigation was initiated with analysis of a simple, zero-degree roof angle cavity, which represents a square greenhouse. Results were compared to experimental results found in the literature and a good comparison was found. Confidence was established in the two-dimensional CFD model. A three-dimensional zero-degree roof angle cavity was also created and verified against data found in the literature. A good comparison between Nusselt numbers was found, and therefore confidence in the three-dimensional CFD model was also established. The three-dimensional CFD model approach was used to investigate the multi-dimensional heat transfer effects of the zero-degree greenhouse cavity. A significant difference between the two- and three-dimensional cases was observed. The next step was to modify the zero-degree roof angle cavity, by adding an angled roof. This represented a simple, single-span greenhouse. The heat transfer in the cavity subject to various roof angles was investigated, and Nusselt-Rayleigh number relationships were established. A three-dimensional cavity of similar dimensions was investigated and compared to the two-dimensional cavity. Temperatures were found to be higher, and velocities much lower compared to the two-dimensional case. A roof ventilator was added to the one side of the greenhouse, and it was found that adding a ventilator does have a noticeable effect on the heat transfer inside the cavity. Nusselt-Rayleigh number relationships were also established for the...D.Ing

A numerical evaluation of nonlinear material behaviour and geometric imperfections on the behaviour of #CR12 hot-rolled columns

M.Ing.3CR12 is corrosion-resisting steel containing 12% chrome. The corrosion-resisting characteristics of 3CR12 are between those of carbon steel and existing stainless steels. Since the material properties of 3CR12 differ from carbon steel, the current SABS code of practice cannot be utilized in the design of hot-rolled components. A numerical investigation into the effect of gradual yielding material behaviour on the buckling strength of 3CR12 columns is presented. The columns under investigation was hot-rolled channel (152 x 76 x 18) sections. The influence of material and geometric non-linearities were investigated numerically. The effect of residual stresses was also investigated. Material data for the Finite Element Model was obtained experimentally via compression tests. The magnitude and distribution of the residual stresses were obtained experimentally by using the sectioning method. The results obtained from the Finite Element Analysis are compared to the buckling load predictions of the South African Code of Practice (SABS 0162-1:1993). Conclusions are made regarding the applicability to hot-rolled 3CR12 sections

TECHNOLOGY DIFFUSION AND FORECASTING: THE CASE OF COMPUTATIONAL FLUID DYNAMICS (CFD) FOR SIMULATION OF GREENHOUSE INTERNAL ENVIRONMENTS

Forecasting emerging technologies as well the rate of diffusion of resultant products are complex in the context of management of technology usually because of a lack of relevant data. Techniques such as bibliometric analysis and the Bass diffusion model are utilized in this paper to assess the growth rate and market penetration of computational fluid dynamics (CFD) as a technology. The penetration and growth rate of user acceptance of two CFD codes (not identified) are simulated. Furthermore, a technology forecasting model of research and innovation in the field of application of CFD in the assessment of greenhouses is presented. Some CFD results of simulations for internal and external flow in an eight-span greenhouse are presented as an illustration of the power of CFD as technology.CFD, Bass diffusion model, bibliometric analysis, management of technology, greenhouse, flow fields

TECHNOLOGY DIFFUSION AND FORECASTING: THE CASE OF COMPUTATIONAL FLUID DYNAMICS (CFD) FOR SIMULATION OF GREENHOUSE INTERNAL ENVIRONMENTS

Forecasting emerging technologies as well as rate of diffusion of resultant products are complex in the context of management of technology usually because of a lack of relevant data. Techniques such as bibliometric analysis and the Bass diffusion model are utilized in this paper to assess the growth rate and market penetration of Computational Fluid Dynamics (CFD) as a technology. The penetration and growth rate of user acceptance to two CFD codes (not identified) are simulated. Furthermore a technology forecasting model of research and innovation in the field of application of CFD in the assessment of greenhouses is presented. Some CFD results of simulations for internal and external flow in an eight span greenhouse are presented as illustration of the power of CFD as technology.http://www.worldscinet.com/ijitm/ai201