Paper accepted: 26.12.2017. Stručni rad REZIME Zagrijavanje stambenih i poslovnih prostora u urbanim područjima tokom zime najčešće se ostvaruje korištenjem toplotne energije koja se distribuira putem centralnog ili gradskog grijanja. Kao osnovni radni medij za generisanje toplotne energije najviše se koriste voda, para i plin. Za zagrijavanje grada Kaknja i njegovih okolnih naselja, toplotna energija se proizvodi u Termoelektrani „Kakanj“i dalje distribuira do krajnjih potrošača koji su na relativno velikim udaljenostima od izvora toplotne energije. U ovom radu opisan je sistem daljinskog grijanja u gradu Kaknju i proces distribucije toplotne energije koju vrši JP „Grijanje“ d.o.o. Kakanj.

This paper aims to present and compare the damage identification results of two methods proposed by the authors for beam-like structures. Both methods use the same numerical and regression models as well as the experimentally obtained values of the beam bending frequencies. The difference between these methods lies in the final stage of their usage. The first method relies on finding three closest intersection points of frequency curves and the second method is based on finding a minimum value of the proposed frequency related functional. The results of damage identification for 28 damage scenarios using the proposed methods are presented and compared in this paper. The comparison showed that the accuracy of both methods is almost the same and depends mostly on the input data quality.

After passing a certain filtering process, the flue gases generated during fuel combustion process in the boiler of a thermal power plant are discharged into the environment by flue channels and a chimney. For a long time, the Thermal Power Plant "Kakanj" has used 300-meter chimney to discharge the treated flue gases into the environment. During the overhaul of the block 7 and reconstruction of 300meter chimney, which were done in the period September-December 2014, it was shown necessary to redirect the flue gases from blocks 5 and 6 toward the 100-meter chimney. This paper presents the calculation of operating parameters and design analysis of 100-meter chimney in order to determine whether blocks 5 and 6 could work without problems when connected to 100-meter chimney. Also, the installation of new flue channels from blocks 5 and 6 to the 100-meter chimney is shown.

Reduction of undesirable particles emission into the air is one of the main tasks for the environment protection. A particular problem is the emission of solid particles from the flue gases that are the product of combustion in the thermal power plant. There are several ways to reduce the emission of those undesired particles, such as using the separators, cyclones, dust chambers, various filters and so on. This paper presents the process of removing solid particles from the flue gases by installation of bag filters type FVU-P in blocks 5 and 6 of the Thermal Power Plant "Kakanj". The basic characteristics and components, application area, principle of operation and automatic ways of shaking bags off are presented in the paper as well as the effects of its installation to the air pollution parameters.

Damage in a structure is a local perturbation of its physical characteristics, i.e. its stiffness, mass and/or damping. Consequently, damage alters dynamic characteristics of the structure such as natural frequencies, damping value and mode shapes associated with each natural frequency. This is the base of vibration based structural health monitoring techniques. In this paper characteristics of mode shapes are investigated for identifying the location of damage in a beam structure. Cantilevered beam model is investigated numerically by use of finite element method. Slope and curvature of displacement mode shapes differences (between intact and damaged structure) were calculated using a central difference approximation. The results have shown that changes in the mode shape characteristics are good indicator of damage location and severity, and hence can be used to detect damage in a structure.

This paper addresses the problem of damage identification in beam-like structures on the base of bending frequency changes. The identification of damage location and its depth is performed by use of regression relations between changes in natural frequencies and damage parameters. Input data for establishing the regression relations are collected using numerical analysis (FEA) of the beam structure with and without damage. The damage is simulated as a narrow open notch perpendicular to the beam axis. The efficiency and limitations of the proposed technique are assessed through a series of damage scenarios.

SUMMARY The developments in Computational Fluid Dynamics (CFD) during the last decade have enabled accurate and reliable calculation of velocity, pressure and temperature fields in fluid flow through different mechanical parts and systems. The quality of results numerically obtained depends on the quality of finite volume mesh, i.e. the number and type of finite volumes that are used in mesh generation. The numerical analysis of stationary oil flow through chambers and channels of cylindrical piston distributing valve was performed and this paper presents the influence of the number of finite volumes and mesh refinement on Δp-Q characteristics of the valve. 1. INTRODUCTION Cylindrical piston distributing valve is one of the most important control and regulating components of hydraulic systems. In classic hydraulics the main function of distributing valves is to control the flow of fluids. Additionally, in proportional and servo hydraulics distributing valves have a great influence on kinematic, dynamic and fluid pressure characteristics. The use of hydraulic fluid systems with classical, proportional and servo distributing valves is very common and important in industrial applications. Consequently, number of engineering and scientific investigations deal with the analysis of distributing valves, [1]. However, Computer Fluid Dynamics (CFD), i.e. numerical analysis of fluid flow through channels and chambers of cylindrical piston distributing valves and their operating performances has been used only in a few special cases. The analyses were performed on simple two-dimensional models using some of the special programs developed for simulations. For instance, A.Kilchmann used the finite difference method in his investigations. On the basis of R.N.Clark investigations, M.Y.Guo and K.Nakano used the boundary elements method to analyze the compensation of fluid force acting on a valve piston. Also, T.Tsukiji used numerical analysis in investigation and simulation of the fluid flow by discrete vortex method. In recent years many authors have used numerical methods such as Finite Element Method (FEM) and Finite Volume Method (FVM) to analyze the fluid flow in cylindrical piston distributing valves. Some of those who used FEM are:

Modern mining industry imposes lots of requirements on mine hoisting equipment associated with hoisting speed, height and payload. To satisfy these needs hoisting equipment should be designed in a proper manner, which requires reliable information on process parameter values. This paper presents the results of strain measurements in a mine hoisting cage. The experiment was designed in order to get the dependence of cage strains and technological parameters, i.e. the hoist heigh (rope lenght), cage acceleration and payload. These data can be used for estimation of stresses and coefficients of safety and their comparison to those given in Regulations of Tecnical Normatives in Mines reffering to people and freight hauling, [1]. These results are also useful in validation of mathematical models and realized technical solutions. 1. INTRODUCTION Mine hoisting equipment represents complex intermittent transport machinery with several transporting operations during freight haulage in one transportation cycle. Theoretical analysis of hoisting equipment stress-strain state is based on some assumptions which can produce mathematical models that differ from the real system, especially in transient periods when dynamic forces appear. In that sense experimental measurements are used to capture real values of relevant physical quantities, which can be used for correction of established theoretical models or validation of realized design solutions. The results of strain measurements of two-storey hoisting cage which were conducted in real conditions (in-sity) are presented in this papaer. The measurements were performed during acceleration and deceleration of the cage when moving up and down. The strain rates and consequent stresses in hoisting equipment components change depending on the cage location in the shaft (height), hoisting speed (acceleration), freight weight, resistance force and so on.