Miklós Neményi

Investigation of simultaneous heat and mass transfer within the maize kernels during drying

Abstract The main goal of this study is to give a mathematical model with numerical solution to follow the heat and moisture distributions inside a cross sectional area of an individual maize kernel as a function of drying time with respect to the effects of the coupled heat and mass transfer processes. The applied drying models are similar to the modified Luikov’s equations, which were first published by Husain et al., 1973. Simultaneous heat and mass diffusion in biological materials. J. Agric. Eng. Res. 18, 343–354. This mathematical model can be used for investigating maize hybrids with different drying characteristics during drying. The data (heat physical constants and variables) for the different maize hybrids (for the slow and the fast drying individual maize hybrids) derive from experiments which have been in progress since the 1980s. The mathematical model with the boundary and initial conditions can reveal for example the difference between the fast and the slow drying hybrids. The temperature and moisture distributions inside the individual maize kernels produced by the model show more realistic picture than the results published before.

Investigation of simultaneous heat and mass transfer within the individual maize kernels during drying

Abstract The main aim of this study is to give a mathematical model with numerical solution to follow the heat and moisture distributions inside a cross sectional area of an individual maize kernel as a function of drying time with respect to the effects of the coupled heat and mass transfer processes to be beyond the existing models and solutions published by literature sources. The applied drying models are similar to the modified Luikovs equations, which were applied by Husian firstly. This mathematical model is used to compare fast and slow drying individual maize hybrids. The data (heat physical constants and variables) for the slow and the fast drying individual maize hybrids derive from experiments which have been in progress since 1981. This model can follow the drying process very well. The mathematical model with the boundary and initial conditions can reveal the difference between the fast and slow drying hybrids. The temperature and moisture distributions inside the individual maize kernel produced by the model show more realistic picture than the results published before.

Soil moisture distribution mapping in topsoil and its effect on maize yield

Abstract Soil moisture content directly influences yield. Mapping within field soil moisture content differences provides information for agricultural management practices. In this study we aimed to find a cost-effective method for mapping within field soil moisture content differences. Spatial coverage of the field sampling or TDR method is still not dense enough for site-specific soil management. Soil moisture content can be calculated by measuring the apparent soil electrical conductivity (ECa) using the Veris Soil EC-3100 on-the-go soil mapping tool. ECa is temperature dependent; therefore values collected in different circumstances were standardized to 25°C temperature (EC25). Constants for Archie’s adjusted law were calculated separately, using soil temperature data. According to our results, volumetric moisture content can be mapped by applying ECa measurements in our particular field with high spatial accuracy. Even though within-field differences occure in the raw ECa map standardization to EC25 is recommended. Soil moisture map was also compared to yield map showing correlation (R2 = 0.5947) between the two datasets.

Investigation of a Non-Thermal Effect of Microwave Treatment

The aim of our experiments was to demonstrate the non-thermal effect of microwave treatment on Saccharomyces cerevisiae fermentation activity. A method was developed for studying the effects of various treatments in the course of must fermentation. The raw material (must) was treated in different ways: (i) heat transfer; (ii) microwave treatment; (iii) inoculation with yeast, and (iv) their combinations. The results of the treatments were compared with respect to alcohol concentration, sugar content, and acidity. The results proved that sugar content of the treated samples rapidly decreased compared to the control sample, and fermentation time was 40% shorter in the fastest case. These results can be explained by the yeast inoculation and microwave treatment. Due to non-thermal effects, fermentation capacity increased by about 30%, while the energy consumption decreased.

Image Acquisition for Site-specific Weed Monitoring Using Panoramic Annular Lens

The practical application of ground-based site-specific applications using optical devices is set back by some typical limiting factors. In case of optical sensing of weeds, pests and other causative agents or even soil properties, there are some different theories to follow (separate weed species or not, take into account shape parameters or only the spectroscopic differences etc.). The more complex image processing is applied, the more elaborated system build-up and more computing demand are required. Besides, the problem of limited visual field still exists, what can be consequently blamed also for the inadequate operation efficiency. The authors applied a Panoramic Annular Lens (PAL) with a horizontal view angel of 360. allowing the coverage of a field part of 1 ha with a single image. The evaluation of the images is carried out in two parallel ways. After pulling the image on the surface of an inverse sphere identical with the PAL, the 1 ha area can be “walked through” and the weeds are present can be identified by means of visual evaluation on a given level of probability. Simultaneously, the pixels containing green plant parts are filtered and a so-called plant density value is calculated. Positioning the pixels containing plant parts and taking into account the information of the visual analysis proper site-specific weed control can be planned. The authors review their experiences in connection with the mentioned research tasks and the already reached results.

New Simulation Technique for Particle Mixing of Stored Bulk Materials

Bulk commodities; such as cereal grains loaded into a silo require active mixing during storage. A special pulsated bottom mixer was patented at our university for gentle mixing of granular solids stored in large containers or silos. Present work intends to reveal the fundamentals in displacement of single particles mixed with different pulsation orders. A glass-walled simulator (filled with wooden cylinders) was built to enable to follow particles within the simulated mixer. Three pulsating pistons – the movements of which provide the mixing effect – were attached to the bottom of the simulator. Selected particles (some with different densities and friction coefficients) were observed during mixing and their positions were recorded after certain pulsations. Based on the measurements the mixing velocity of (particles) cylinders was calculated. The focus of examinations was to give restrictions of the mixing: density and friction of particles in connection with pulsation. However, no correlations were found between the mixing velocity and density or friction of the particles. Our basic aim was to study the effect of the two factors (particle density and friction) on the movement of particles. The gained results indicate that present models – in which these two factors are basic parameters – require revision. A mathematical model of discrete element was used to describe the movement inside the simulator, aiming to calculate the restricted parameters. The model gives similar results with the measurements. However, further investigation is required to enhance the accuracy.

Convective Drying Simulation of Saccharomyces cerevisiae Biomass Using SIMULINK

Abstract The convective drying is a process due to the interaction between a material and a drying media. The moisture content of the material decreases during drying, which is described by the drying curve. In this paper a model for the drying of Saccharomyces cerevisiae (yeast-paste) is presented. Constants used for building up the model are experimentally determined. The simulations were performed with Matlab-Simulink software. Its dinamic building system provides model-upgrading possibilities as they are imposed.

Application of the Drucker-Prager Elastic-perfectly Plastic Material Model for Performing Finite Element Analyses of Deep Tillage

Abstract The possibility of conducting a non-linear, three-dimensional, finite element analysis of soil cutting process by medium-deep subsoiler based upon the Drucker-Prager elastic-perfectly plastic material model was investigated. The mathematical construction of the Drucker-Prager model was presented. The material nonlinearity of soil was dealt with using an incremental technique. Inside each step the Newton-Raphson iteration method was utilised. While the geometrical nonlinearity was solved by using either the small strain assumption or the updated Lagrange formulation of large displacement. The finite element predictions of subsoiler draught force as well as surface soil failure dimensions agreed well with those measured in a soil bin. An optimal subsoiler design was figured out, which required the lowest draught and developed a good soil loosening quality estimated as soil volume change.

ENERGETICAL OPTIMALISATION OF THE GRAIN DRYING PROCESSES BY THE CONTROL OF AIRFLOW RATE

Abstract The control of the grain driers is very important, both to save the quality of the agricultural products and to reduce the energy consumption of drying. The drying process of the different kernel products has to be divided into phases. The influence of the air flow rate on the drying characteristics of the maize kernels was investigated. The subject of this research work was to keep the relative humidity of the output drying air constant and hereby to increase the power efficiency of grain driers. The mathematical model described in this study is helpful in designing the energy and quality saving grain driers.