Research in Agricultural Engineering, 2005 (vol. 51), issue 3

Exergy of heat flows in exchanger consisting f gravity heat pipes

D. Adamovský, P. Neuberger, D. Herák, R. Adamovský

Res. Agr. Eng., 2005, 51(3):73-78 | DOI: 10.17221/4906-RAE  

The paper deals with the analysis of the impact of inlet air temperature on the exergy efficiency and exergy of the losing heat flow and determination of the relation between the exergy and thermal efficiency in an exchanger consisting of gravity heat pipes. The assessment of heat processes quality and transformation of energy in the exchanger are also dealt with.

Structural dynamic modification of circular disc using pre-stressed fields

M. Naď

Res. Agr. Eng., 2005, 51(3):79-84 | DOI: 10.17221/4907-RAE  

Dynamical properties of circular discs are investigated in this paper. One of the techniques of the disc modifications to achieve the required dynamic properties is to initiate pre-stress in disc plane. To obtain appropriate in-plane stress either roll-tensioning of disc surface or volume transformation of disc segment can be used. The role of in-plane stresses is assessed from the change in natural frequencies and modal shapes. The natural frequency characteristics for various rolling position and various rolling depth of the annulus are obtained by modal analysis using Finite Element Method (FEM).

Mathematical function for the transition curves description

R. Chotěborský, D. Herák, V. Bezouška, P. Hrabě, M. Müller

Res. Agr. Eng., 2005, 51(3):85-90 | DOI: 10.17221/4908-RAE  

Toughness is one of important material properties. At present steel is still the most used material. Owing to the temperature this material can fail both brittly and ductily. Therefore we look for the temperature above which the material will failur ductily. The Charpy impact test is one of methods how to determine the ductility by the temperature - transition access in the determined temperature range. The measured data file is large and it requires the interlay by a curve which presents the relation between the impact energy and the temperature.

Testing device with opened hydrostatic circuit for dynamic loading of the tractor engine by power take off shaft

Š. Drabant, M. Bolla, A. Žikla, I. Petranský, J. Ďuďák

Res. Agr. Eng., 2005, 51(3):91-98 | DOI: 10.17221/4909-RAE  

The developed loading device with opened hydrostatic circuit for measurement of speed and dynamic characteristics of the tractor engine by power take off is presented. This loading device may also be used as a portable type for field measurement. At present for development of these loading devices controlled hydrogenerators and electro-hydraulic proportional pressure valves directed by computer may by used to adjust geometrical volume of the hydrogenerator from zero to maximum value. There is a possibility to built these devices which consist of one hydrogenerator and one by-pass valve for the maximum power of internal combustion engine 420 kW which...

Longitudinal oscillations of the sugar beet root crop body at vibrational digging up from soil

V. Bulgakov, I. Holovach, M. Berezovyy

Res. Agr. Eng., 2005, 51(3):99-104 | DOI: 10.17221/4910-RAE  

The longitudinal vibrations theory of a continuous elastic body with one fixed extremity is designed. The Ostrogradskii-Hamilton principle of a stationary operation is applied. By Ritz's method the Ritz's equation of frequencies for viewed oscillatory process is obtained. In particular analytical expressions for definition of the first and second fundamental frequencies of body oscillations and forced oscillations amplitude of its any cross-section are obtained.