Research in Agricultural Engineering, 2013 (vol. 59), issue 3
Evaluation of tractor biodegradable hydraulic fluids on the basis of hydraulic pump wearOriginal Paper
R. Majdan, Z. Tkáč, J. Kosiba, R. Abrahám, J. Jablonický, Ľ. Hujo, M. Mojžiš, P. Ševčík, M. Rášo
Res. Agr. Eng., 2013, 59(3):75-82 | DOI: 10.17221/18/2012-RAE 
Two types of biodegradable hydraulic fluids (HEES and HEPR) with the mineral oil-based hydraulic fluid (HV) were compared. The tests were performed using a test bench. During the tests with a tractor hydraulic pump, the fluids were loaded by a cyclic pressure load. The tests of fluids were evaluated on the basis of wear of the pump. Evaluation parameters were the flow characteristics of the pump and the cleanliness level of tested fluids. The temperature of the fluid under which the test was performed was measured in real operating conditions of the Zetor Forterra 11441 tractor. It is possible to state upon the test results that the mineral oil-based...
Chemical, stoichiometric and thermal analysis of fatty acid methyl esters from processed animal fatOriginal Paper
J. Malaťák, L. Škarková, A. Prošková
Res. Agr. Eng., 2013, 59(3):83-90 | DOI: 10.17221/27/2010-RAE
The paper focuses on liquid biofuel raised by transesterification of processed animal fat from rendering plant production suitable for energy use. The objective of the paper is to carry out an element analysis and stoichiometric analysis of selected samples of fuel from rendering plant production and to compare them with classic elements. The results of the analyses prove higher values of nitrogen concentration in the samples from rendering plant fat. In case of the samples of fatty acid methyl esters (FAME) from it a reduction of nitrogen was proved even if the values are still higher than at fatty acid methyl esters rape oil. Concerning the concentration...
Analysis of ground massif temperatures with horizontal heat exchangerOriginal Paper
M. Šeďová, R. Adamovský, P. Neuberger
Res. Agr. Eng., 2013, 59(3):91-97 | DOI: 10.17221/30/2012-RAE
The paper is aimed at specification of ground massif temperatures in the horizontal heat exchanger area in both the heating season and during heat exchanger stagnation. The energetic potential of the ground massif was evaluated using the difference of temperatures of the ground massif in the area of the heat exchanger at the beginning and at the end of the heating season. Specific heat rates of the ground heat exchanger were also determined, and the influence of the ground massif thermal resistance and coefficient of heat transfer between the inner wall of the heat exchanger pipe and the heat-carrying liquid were analysed.
Disintegration process in disc crushersOriginal Paper
P. Vaculík, J. Maloun, L. Chládek, M. Přikryl
Res. Agr. Eng., 2013, 59(3):98-104 | DOI: 10.17221/28/2012-RAE
Grinding or crushing hard raw materials is usually a primary operation which precedes the follow-up technological processes in a number of industrial sectors. A great variety of machines using different principles of fragmentation are employed in the technology of pulverization. The food industry uses roller mills, in which the main process is the shear grinding. In the animal feed industry impact machines known as hammer mills are often used. In recent years, mills have been employed that use their frontal edges for grinding or crushing during the rotation of one of two adjacent discs. The modern design disc machines used for grinding grain have resulted...
Determination of oxygen permeability of polyethylene and polypropylene nonwoven fabric foilsOriginal Paper
Ľ. Kubík, S. Zeman
Res. Agr. Eng., 2013, 59(3):105-113 | DOI: 10.17221/31/2012-RAE
The paper deals with determination of oxygen permeability of the polyethylene and polypropylene foils applied in mulching and food packaging. The construction of the equipment of measurement of gas permeability through the foils is discussed. The design and construction of the equipment was realized with applying of the Standard STN EN 77 0333. The measurement of permeability of oxygen through the polyethylene Bralen 2-63 with 9% colored concentrate Maxithen HP 533041 - violet foil, Polyten®MLB black&white foil and black polypropylene nonwoven fabric foil were realized by means of the modified method.
Computer simulation of the teat-cup liner stress and strain tensorOriginal Paper
I. Karas, R. Gálik, Š. Pogran, M. Šesták
Res. Agr. Eng., 2013, 59(3):114-119 | DOI: 10.17221/23/2012-RAE
The three-notch black pressed teat-cup liners were selected into the set of the analysed teat-cup liners, and, for comparison purposes, teat-cup liners produced from silicone mixture. Wall thicknesses of the analysed teat-cup liners were adjusted by smoothing of the middle working part in length of 30 mm. The working part thickness thus changed from the original 2.37 to 0.41 mm for a teat-cup liner produced from black mixture and from the original thickness of 2.30 to 0.40 mm for a silicone teat-cup liner. A possibility of maximum closure of teat-cup liners in the pressing tact was assessed at the working suction of 50 kPa, the flow of distilled water...