جستجوی مقالات مرتبط با کلیدواژه « هم دما » در نشریات گروه « مکانیزاسیون کشاورزی »

In 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.   

In 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).

The 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.

The 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.

In recent years, the role of robotics technology in the management of poultry conditions and the welfare of livestock has led to increase of production rate and reduce of production costs. The purpose of this research was to construct a robot to measure and plot the distribution of temperature, humidity, ammonia and oxygen parameters in the poultry house, and to apply the commands necessary to optimize the poultry conditions in different parts of the building. For this purpose, an experiment was carried out using 700 laying hens for 20 days from age of 20 days. The robot made in this study includes 3 hardware components, a set of sensors (ammonia, carbon dioxide, temperature and humidity), data storage unit, displays, mechanical components (wheels, gearboxes and chassis) and the software sector. The robot made in this study includes 3 hardware components, a set of sensors (ammonia, carbon dioxide, temperature and humidity), data storage unit, displays, mechanical components (wheels, gearboxes and chassis) and the software sector. The robot made in this study includes 3 hardware components, a set of sensors (ammonia, carbon dioxide, temperature and humidity), data storage unit, displays, mechanical components (wheels, gearboxes and chassis) and the software sector.In order to control the local environment of each cage, due to the variability of the amount of excrement, birds activity, and also the remoteness and proximity to poultry conditioning, a control circuit was constructed to optimize the conditions of each cage. By calculating the directional error, the angular difference between the orientation of the path and the actual orientation of the robot, the speed of the motors was adjusted automatically. The amount of robotic deviation from the predetermined path in the direct path and bypass was calculated and the mean error of the robot in the seven points examined was 1.34 and 4.5 cm, respectively. In addition, according to the distribution diagrams, the parameters of temperature, humidity, ammonia and oxygen were determined and the required action was taken.

Introduction Phosphorus (P) is an essential nutrient for all forms of life on the earth, but in excess concentrations, it can act as a serious water pollutant through eutrophication. Thus, it is very important to remove P from aqueous solutions before their release into natural water resources. Among the various P removal techniques that have been developed, the sorption process is widely accepted to be an effective water treatment technique because of low cost, ease of operation, simplicity of design, and high sorption capacity in dilute solutions. Layered double hydroxides (LDHs) are a type of two-dimensional nanostructure anionic clays with high capacities to sorption of anions. These non-silicate clays consist of positively charged brucite-like octahedral sheets which neutralize by a negatively charged interlayer containing relatively weak bonded anions and water molecules. The positive charges generated by the isomorphous substitution of trivalent cations for divalent cations are balanced by interlayer anions that can be exchanged by other anions making them good anion-exchangers with high selectivity. LDHs have been widely used as environmental sorbents because of their high charge density, large interlayer areas, good thermal stability, and high anion exchange capacities of the interlayer anions. The aim of the present study was to synthesize a Mg-Fe LDH as a sorbent for P removal from aqueous solution. Materials and Methods The Mg-Fe LDH was synthesized using the co-precipitation method. In brief, a mixture solution containing 0.03 mol MgCl2. 6H2O, and 0.01 mol FeCl3. 6H2O was added dropwise into a flask containing 100 ml of 1 M NaOH solution under vigorous stirring at pH=10. The obtained slurry was filtered and washed repeatedly with DW until the filtrate pH reached neutral. Mg-Fe LDH particles were then obtained by drying the filtrate at 70 °C in an oven overnight. The crystallinity of the sample was studied using X-ray diffraction (XRD) analysis. In order to investigate the performance of the synthesized LDH as a P sorbent, batch experiments were carried out in polyethylene centrifuge tubes. The suspensions were shaken for 24 hours at 250 rpm, and the supernatant was then separated by centrifugation at 4000 rpm for 10 minutes and were filtered by Whatman ashless grade 42 filtration papers. Equilibrium P concentration was determined according to the ascorbic acid method using UV-vis spectrophotometer at the wavelength of 880 nm. The effects of pH, initial P concentration, and contact time on P sorption were investigated in the ranges of 2-10, 0-300 mg/L and 0-1440 min, respectively. Results and Discussion The XRD pattern of the LDH sample showed typical structure of hydrotalcite-like compounds with sharp and reflection peaks corresponding to the (003), (006), (012), (015), and (110) crystal planes which are characteristic planes of hydrotalcite-like compounds. The efficiency of LDH to remove P decreased with the increasing of initial P concentration and the maximum removal efficiency of LDH occurred in the range of 5-20 mg/L of initial P concentration. With increasing of initial P concentration from 20 to 300 mg/L, the P removal efficiency of LDH decreased from 98.7 to 24.6 %. The P removal efficiency was increased with time and reached equilibrium at 60 min. The P removal rate of LDH in this time was about 66 % and no significant decrease in residual P concentration was observed after 60 min. The sorption of P on LDH was highly pH dependent, and the maximum P removal was found at pH of 4. The sorption kinetic and isotherm data were well described by pseudo-second-order and Langmuir equations, respectively. According to the Langmuir equation, the maximum P sorption capacity (Qmax) of LDH was obtained as 13.96 mg/g. Conclusion It was found from the results of this study that the mechanisms involved in the P sorption onto LDH included electrostatic attraction, ligand exchange, and surface complex formation. In addition, the results suggested that the synthesized Mg-Fe LDH can be potentially used as an effective sorbent for the removal of P from aqueous solutions. Further research is needed on the regeneration of the LDH after P sorption and the evaluation of desorption behavior of P from LDH under different conditions.

The purposes of this article are studying the effects of oxygen presence on waste wood pyrolysis process in order to produce bio-char. To reach the goal, cubic samples of size 2.5 cm pyrolized at 300 and 400 °C. The surface and center temperatures of samples were measured and their mass losses were calculated from the ratio of pyrolized mass to initial mass of the sample. increase in temperature caused increase in the rate of pyrolysis and temperature changes, but decrease the final efficiency of biochar. Moreover, the surface temperature of samples in oxidative pyrolysis compared with the pyrolysis in an environment containing inert gasses, is about 100 °C more, i.e. a reduction in time consumption and consequently in energy use during the oxidative pyrolysis process. According to the non-linear nature of waste wood pyrolysis process, artificial neural network (ANN) was used to model the temperature distribution and the mass loss of samples. The results of ANN were in a good agreement with the experimental consequences and showed the correlation coefficients of 0.9998 and 0.9991 in modeling of temperature distribution and mass loss of samples, respectively.

In this study, a numerical simulation was developed for flow in a pilot plant spray dryer with a cooling air jacket using the CFD method. A k-ɛ standard model was used to simulate turbulence. Air flow patterns and temperature variation in the chamber and cooling air jacket were estimated and suitable insulation calculated for the ceiling of the chamber. To verify the numerical results, velocity in the dryer was measured using a portable hot wire anemometer. Temperature variation was measured using transmitters installed at varying heights in the chamber. The numerical results showed that flow pattern consisted of a high velocity core extending toward the end of dryer. A circular flow around the circumference of the flow created vortices and caused particles to turn back toward the top of the dryer. The maximum temperature was at the core of the air flow and temperature decreased from the core toward the dryer wall. The flow path line in the cooling air jacket showed that the air layers were in smooth and harmonic motion around one another that produced little variation in axial velocity in this zone; however, at the junction of the cylindrical and conical parts of dryer jacket, some flow deviation occurred toward the wall. Adequate insulation for the ceiling was chosen according to the ratio of heat conductivity to the thickness of the insulator (K/L).

The underground temperature at a depth of about three to four meters is almost constant during the year. As a result in summer the underground is cooler than the ambient temperature. This potential is considered for greenhouse cooling by using an Earth-to-Air Heat Exchanger (EAHE). In this research the effects of two parameters were investigated: a) the area of greenhouse in three levels of 9, 18, 27 m2 and b) the percent of vegetation coverage inside the greenhouse in three levels of 0%, 50%, 100% on the performance of EAHE. The experimental design was factorial experiment in a randomized complete block design. The parameters of greenhouse’s inside temperature, thermal energy exchange and coefficient of performance (COP) were considered in cooling mode. As one of the remarkable results it was observed that the closed loop utilization of the system was infeasible in cooling mode. This was mainly due to the occurrence of vapor distillation inside the underground pipes and hence the blockages of the air flow. Also the effect of area and the percent of vegetation coverage were significant on the performance of EAHE. The highest average temperature difference between the temperature of testimonial greenhouse and the temperature of greenhouse was observed in treatment of 100% vegetation coverage and 9 m2 floor area which was measured as 9.6°C. The least average temperature difference in the treatment without vegetation coverage and 27 m2 floor area was measured as 5.2 °C. Considering thermal energy exchange in cooling greenhouse with open loop, the best treatment determined for EAHE in this research was the one with 9 m2 floor area and 100% of vegetation coverage.