Research in Agricultural Engineering, 2004 (vol. 50), issue 4
Technology and economy of energy crops
Z. Abrham, M. Kovářová, T. Kuncová
Res. Agr. Eng., 2004, 50(4):123-129 | DOI: 10.17221/4938-RAE 
The cost modelling for growing and harvest of selected energy crops and further costs for recommended forms of energy crops processing to biofuels was conducted. Importance and effect of subsidies on resulted costs for biofuels production was assessed. The result are then total costs per unit of fuel weight which range from 469 to 1,806 CZK/t for biofuels processed to form of chopped material or pressed bales and from 881 to 2,466 CZK/t for briquettes and pellets. The result costs per energy unit in biofuel have ranged from 59 to 121 CZK/GJ. On basis of economical data is evaluated the biofuels competitive power in comparison with main competitive...
Exergy of heat flows of the air-to-air plate heat exchanger
R. Adamovský, D. Adamovský, D. Herák
Res. Agr. Eng., 2004, 50(4):130-135 | DOI: 10.17221/4939-RAE
Based on extensive measurements of the temperature, humidity and flow rate of the heated and cooled air in the plate heat exchanger this article analyses the influence of air inlet temperatures on both the exergy efficiency of the heat exchanger and the heat loss exergy. Furthermore, it describes the dependence between the thermal and exergy efficiency of the heat exchanger. The analysis of the tested heat exchanger indicated that the exergy efficiency of heat utilization from cooled air increases with rising inlet air temperature different, while the exergy efficiency of the heat transfer from cool to heated air decreases. In addition, the experiments...
Heating briquettes from energy crops
D. Plíštil, M. Brožek, J. Malaťák, P. Heneman
Res. Agr. Eng., 2004, 50(4):136-139 | DOI: 10.17221/4940-RAE
The aim of this research is to find and to evaluate energy crops with respect to their compactibility. It resulted in an evaluation of mechanical properties of seven crop species and in findings concerning mechanical parameters that exert influence on the compacting process. The evaluated mechanical properties cover the briquette density and the force required to break the briquettes. Following energy crops were studied: Sorghum vulgare, Phalaroides arundinacea, Crambe abyssinica, Fectusa pragensia, Camelina sativa, Miscanthus sinensis, Carthamus tinctorius. Before compression these crops were disintegrated in a grinder. The fraction size...
Evaluation of cattle and sheep buildings with their surroundings using 'visual quality assessment' technique
T. Taşkin, A. Kaplan, A. Önenç, C. C Hepcan
Res. Agr. Eng., 2004, 50(4):140-151 | DOI: 10.17221/4941-RAE
This study was conducted to assess visual quality of cattle and sheep housings with their surroundings across the seven districts of İzmir province, located in western side of Turkey. A total of 58 animal farms consisting of 31 cattle and 27 sheep farms were investigated. After watching the videos of all animal housings with their environs, each sample lasts for approximately 60 seconds, the 250 photos derived from the video scenes were evaluated by an expert group of 30 respondents in one panel. The respondents were asked to rate visual quality of each photo and its features on a five-point scale in order of district and farm type (cattle or...
Influence of heat treatment on mechanical properties of steel
R. Chotěborský, M. Brožek
Res. Agr. Eng., 2004, 50(4):152-155 | DOI: 10.17221/4942-RAE
This article concerns an influence of heat treatment on strength and toughness of steel. The partial results of tests on steel 12 042 are presented.
The spring of internal combustion engine valve mechanism
J. Honců
Res. Agr. Eng., 2004, 50(4):156-159 | DOI: 10.17221/4943-RAE
This article deals with computational research of piston engine valve train including helical spring with variable number of active coils. This engine is destined for passenger car and therefore is featured by wide range of operational speed.