THE POTENTIALS OF SOLAR ENERGY IN THE REPUBLIC OF SERBIA : CURRENT SITUATION, POSSIBILITIES AND BARRIERS

Although the potential of solar energy in the Republic of Serbia is up to 30% higher than in the countries of the European Union that lead to the implementation of these technologies, the Republic of Serbia is ranked among the countries with the lowest production in the region with the production of 10 MV solar PV capacities. The aim of the paper was to present the current balanced capacities, related to solar PV energy, in the Republic of Serbia and countries in the region. In order to present better the material and conclude why the results in the Republic of Serbia are not better, in the paper are analyzes the possibilities for installing such capacities as well as the barriers that need to be eliminated

AN ENERGY CONSUMPTION ANALYSIS ON PUBLIC APPLICATIONS IN THE CITY OF NOVI SAD

The aim of the paper was to analyse energy efficiency indicators of energy consumption over public buildings in the territory of the City of Novi Sad. Also, the paper analyses the costs of energy and water consumption, as well as the emission of CO2 and other greenhouse gases. Analysis of energy consumption was carried out on 200 public buildings in the territory of the City of Novi Sad. The time frame for observing energy consumption is 2013-2015. years. Total average primary energy consumption for the mentioned period amounted to 8,142 teo, and the average value of emissions of harmful gases with greenhouse gases was 25,527.23 tCO2

Analysis of Bearing Assemblies Refit in Agricultural PTO Shafts

The paper analyzes the problems of the most commonly used cardan shafts in agricultural machinery through a theoretical review and tests on a laboratory test bench. The aim of the research presented in this paper was to define the justification of a new method for retrofitting universal joint bearing units compared to the traditional methods of retrofitting. The new approach is based on energy efficiency (saving energy, raw materials and labor) compared to the conventional methods of retrofitting. The presented investigation to justify the proposed refit was carried out after the investigation of the extent of damage to the elements of the bearing assembly, which lasted 4.02 minutes per sample, with the aim of obtaining information essential for the purpose of our work. The proposed diagnosis and refit of the cardan bearings can help to extend the service life and improve the reliability of the universal joint shafts already in service. The results of the research have shown that the method with replaceable bushings (installation of undamaged surfaces in the load transfer zone) is 6.24 to 7.54 times cheaper than the complete repair of the elements of the bearing assembly, 2.11 to 2.83 times cheaper than the refit method, in which the damaged joints are replaced with new ones, and 1.62 to 2.74 times cheaper than the purchase of new double PTO (Power Take-Off) shafts

HEAT BALANCE OF COMBINED HEAT EXCHANGER AERODYNAMIC HEATING DRYERS

Today, the use of aerodynamic dryers for drying various types of fruit crops is very current. In them, the electric energy spent on the drive of the centrifugal fan is transformed into thermal energy due to the mutual friction of the air flows circulating in the closed chamber. In order to increase the energy efficiency of the drying process, the heat of the waste drying agent was used in the research. The presented dryer was equipped with a combined heat exchanger. In order to predict the thermal performance of the combined heat exchanger depending on external factor variables, the dependence of the temperature of the fresh drying agent at the outlet of the combined heat exchanger on the dryer operation time is theoretically determined on the basis of the heat balance equation. The air solar collector in the combined heat exchanger made it possible to increase the temperature of the drying agent at the outlet by another 10 oC without extra costs of electrical energy. A comparative analysis of the results of experimental and theoretical studies showed their high convergence

MODELING OF THE MECHANISM OF ACTION OF EPILAME FILM IN THE PROCESS OF PROCESSING

The article discusses the mechanism of action of the epilam film during the operation of epilated drills and the influence of cutting conditions, processing conditions on their condition. Tribological tests were carried out using a special installation, where the test conditions are close to the conditions characteristic of the drilling process. Based on the results of the experiment, it was found that the effectiveness of epilam film directly depends on the cutting speed, which determines the temperature in the contact zone. Research has shown that use of oil-based LCTF MR-7 (МР-7) has the best effect on the state of epilam coating

THE STUDY OF CHARACTERISTICS OF ELASTICITY AND RESIDUAL STRESSES IN COATINGS APPLIED BY PLASMA METHODS

At present, a strategically important task of technological independence of Russian industries is restoration of worn-out parts of machines and equipment by plasma methods based on the use of coatings of different functional purpose. The purpose of this study is to solve the actual problem of choosing the rational modes of plasma coating in the process of restoration of worn parts, subjected to intensive wear in the operation process. To solve this problem, the experimental studies of the elasticity characteristics in the plasma-deposited coatings were carried out. The study results allowed determining the most optimal range of rational modes of plasma coating deposition in terms of obtaining high elastic properties of plasma coatings as the key stage of resource-saving technology for restoration of worn parts of machinery and equipment

New technologies improving aerodynamic properties of freight vehicles

© 2019 Published by the Serbian Academic Center. Fuel consumption of heavy duty vehicles is caused by actual vehicle resistances acting during the vehicle motion. This paper deals with possibilities to reduce the vehicle aerodynamic resistance, air drag coefficient. This resistance effects the vehicle fuel consumption by higher vehicle velocities at most. There are evaluated actual values of vehicle air drag coefficient, possible devices reducing the air drag and the influence of chosen aerodynamic devices on the drag reduction and fuel consumption reduction

Analysis of Bearing Assemblies Refit in Agricultural PTO Shafts

The paper analyzes the problems of the most commonly used cardan shafts in agricultural machinery through a theoretical review and tests on a laboratory test bench. The aim of the research presented in this paper was to define the justification of a new method for retrofitting universal joint bearing units compared to the traditional methods of retrofitting. The new approach is based on energy efficiency (saving energy, raw materials and labor) compared to the conventional methods of retrofitting. The presented investigation to justify the proposed refit was carried out after the investigation of the extent of damage to the elements of the bearing assembly, which lasted 4.02 minutes per sample, with the aim of obtaining information essential for the purpose of our work. The proposed diagnosis and refit of the cardan bearings can help to extend the service life and improve the reliability of the universal joint shafts already in service. The results of the research have shown that the method with replaceable bushings (installation of undamaged surfaces in the load transfer zone) is 6.24 to 7.54 times cheaper than the complete repair of the elements of the bearing assembly, 2.11 to 2.83 times cheaper than the refit method, in which the damaged joints are replaced with new ones, and 1.62 to 2.74 times cheaper than the purchase of new double PTO (Power Take-Off) shafts

Multi-Objective Optimization of Tribological Characteristics for Aluminum Composite Using Taguchi Grey and TOPSIS Approaches

In this study, a multi-objective optimization regarding the tribological characteristics of the hybrid composite with a base material of aluminum alloy A356 as a constituent, reinforced with a 10 wt.% of silicon carbide (SiC), size 39 µm, and 1, 3, and 5 wt.% graphite (Gr), size 35 µm, was performed using the Taguchi method, gray relational analysis (GRA), and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) decision-making methods. Tribological tests were carried out on a “block on disc” type tribometer with lubrication. Load, sliding speed, and graphite mass concentration were analyzed as input parameters. As output parameters, wear rate and coefficient of friction were calculated. An analysis of variance (ANOVA) was conducted to identify all parameters that have a significant influence on the output multi-response. It was found that the normal load has the highest influence of 41.86%, followed by sliding speed at 32.48% and graphite addition at 18.47%, on the tribological characteristics of composites. Multi-objective optimization determined that the minimal wear rate and coefficient of friction are obtained when the load is 40 N, the sliding speed is 1 m/s, and the composite contains 3 wt.% Gr. The optimal combination of parameters achieved by GRA was also confirmed by the TOPSIS method, which indicates that both methods can be used with high reliability to optimize the tribological characteristics. The analysis of worn surfaces using scanning electron microscopy revealed adhesive and delamination wear as dominant mechanisms