H. Farzanpour; S. S. Seiiedlou Heris; H. Nalbandi
Abstract
IntroductionIn livestock and specifically poultry houses, controlling the internal environment conditions is a key factor to increase animal productivity and prevent their casualties. Controlling the atmospheric conditions like the air temperature and gas concentration in semi-enclosed spaces like poultry ...
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IntroductionIn livestock and specifically poultry houses, controlling the internal environment conditions is a key factor to increase animal productivity and prevent their casualties. Controlling the atmospheric conditions like the air temperature and gas concentration in semi-enclosed spaces like poultry houses can improve the living conditions. Experimental tests on the atmospheric conditions of livestock and poultry houses are challengeable and due to limitation of measurement points, unstable climate conditions and experimental errors. Simulation of the air temperature and momentum conditions is used unlimitedly with computer resources by Computational Fluid Dynamics (CFD) methods to overcome the limitations of experimental tests. This method has vast abilities of parametric analysis and predicting the optimum range of functional parameters. So in this research, the air temperature and velocity distribution of a poultry house were simulated using CFD to achieve the best condition for the air ventilation and uniform temperature distribution. Materials and MethodsIn the present study, the geometrical model of poultry house was created using Gambit software and meshed. The mesh independence study was also performed. According to the results, 166550 elements were enough to solve the problem with an acceptable accuracy.The Reynolds-averaged Navier-Stokes (RANS) equation was selected to simulate the momentum transfer inside the poultry house. The k-ε model is one of the most used turbulence models for industrial applications. The main assumption in this model is that the flow is incompressible and that the fluid is Newtonian. A transient heat transfer equation within the fluid domain was selected to predict the air temperature that describes a time-dependent process that includes the conduction and convection terms. All the boundary condition was measured experimentally during 24 hours and their temperature was modeled using the proper mathematical models and applied to the developed model. The mathematical models were solved simultaneously in ANSYS- FLUENT software. The developed simulator was validated experimentally by measuring the air temperature of some specified locations (13 points).Results and DiscussionThe results demonstrate that the model enjoyed satisfactory accuracy so that the RMSE value between the measured and predicted air temperature was in the range of 0.405 to 1.29 and the simulator could predict the air temperature with the accuracy of 0.6 degrees. Therefore, it is possible to use the validated simulator for the real-time controlling of poultry houses to optimize the ventilation process. According to the results, the high heterogeneity in the air temperature and about an 18-degree difference was observed in the air temperature distribution at various locations of poultry houses. In addition, the air velocity was not uniform at the different plans of poultry house; especially in the central points of poultry house, it was higher than 1 m/s that is higher than the recommended value. Therefore, the simulator was used to improve the ventilation of the poultry house. The results of various simulations carried out indicated that the angle of the air inlets vents affects the air turbulence. Also, the air temperature and velocity distribution were more uniform when the air inlet vents were across each other. Therefore, some new gates were opened and the angle of the existing gates was changed to improve the ventilation condition of the poultry house. By such modification, the ventilation condition of the poultry house was improved and the air velocity and temperature distribution in the optimized house were more uniform than that observed in the primary one. The air temperature and velocity were in the range of 291 to 297 K (18 to 24 °C) and 0.23 and 0.46 m s-1, respectively. These values are at the recommended condition for poultry houses.ConclusionThe opening angle of the vents had a significant effect on the air distribution. Application of across vents in the side-walls of poultry house led to uniform distribution of air velocity and temperature. The developed simulator has good performance and accuracy to design and construct poultry houses.
Modeling
J. Javadi Moghaddam; S. Ozlati; Gh. Zarei; D. Momeni; F. Azadshahraki
Abstract
IntroductionGreenhouse technology is a flexible solution for sustainable year-round cultivation of many horticulture products, particularly in regions with adverse climate conditions or limited water and resources. Greenhouses are the structures that provide the desired conditions for plant growth throughout ...
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IntroductionGreenhouse technology is a flexible solution for sustainable year-round cultivation of many horticulture products, particularly in regions with adverse climate conditions or limited water and resources. Greenhouses are the structures that provide the desired conditions for plant growth throughout the all seasons. Plant growing and crop production in the greenhouses require proper ventilation conditions to provide optimal temperature, relative humidity and CO2 and to minimize the toxic gases. Ventilation method of greenhouse is depending on the design of greenhouse ventilation and cooling is usually done by evaporative pad and fan systems or fan and vent systems. Recently different designs, different structures and different layouts of fans, pads and vents are used in greenhouses. Layout of fans, pads and vents affects the performance of ventilation systems. The aim of this study was to layout the fans, pads and vents to provide best air flow in an octagonal greenhouse. Materials and MethodsIn this study, three layouts of evaporative pad and fan systems and vents were modeled by computational fluid dynamics (CFD) method. For computational fluid dynamic of inside greenhouse airflow, the air flow was considered to be compressible. In order to estimate density, velocity and temperature, the Navier- Stokes equation included momentum, state, energy, continuity was used. For modeling the fluid flow, all necessary and dependent parameters of climate were considered based on the concentration and air pressure at the level of the open sea. Fluid flow equations were solved by finite volume technique. Three mentioned layouts of this study were 1- fans on the roof of the pyramids and vents on the wall of the pyramids, 2- pads and fans on the greenhouse side walls and 3- pads on the greenhouse side walls and fans on the roof of the pyramids (parallel pads). The performances of each arrangement can be improved by the speed of the fans, the size of the vents. The main equation in fluid flow simulation using CFD can be done by the following set of equations in which the continuity equation in the form of indicial notation can be presented as: Moreover, the momentum equation can be written by the following form: The equation 4 shows the state equation in a fluid flow interaction. All technical calculations and CFD simulations were done by Solidworks 2018 software.Results and DiscussionThe results showed that octagonal greenhouse by a specific form of the vents on the walls and fans on the roof could provide a circular air flow around the plants in the greenhouse. However, due to different powers of the fans, different velocity and different shape of air circulation could be achieved. When pads and fans are located on the greenhouse side walls, uniform air flow from the pads move uniformly throughout the greenhouse and then exit from opposite fans which causes desired air flow in the greenhouse. When the fans are located on the roof of the pyramids and pads are located on the side walls parallel, pad surface increases in the greenhouse and thus relative humidity increases and temperature decreases.ConclusionBecause of the specific shape of the vents in octagonal greenhouse, different air velocity and different shape of air circulation will be achieved when different power of the fan is used. This causes that the octagonal greenhouse can be used in different climate conditions. When the fans are located on the roof of the pyramids and pads are located on the side walls, temperature decreases and relative humidity increases and this layout is desirable for hot and dry climate. An octagonal greenhouse can be used in different climate by using a suitable layout of fan, pad and vents.
