A review of explicit approximations of Colebrook's equation

U radu je dat pregled najčešće korišćenih eksplicitnih jednačina za određivanje koeficijenta trenja u glatkim i hrapavim cevima. Odstupanje navedenih jednačina od Kolbrukove jednačine izraženo je preko srednje relativne greške, maksimalne pozitivne greške, maksimalne negativne greške, srednjeg odstupanja i korelacionog odnosa. Osim navedenih kriterijuma, poređenje jednačina je izvršeno i korišćenjem 'Model selection criterion' (MSC) i 'Akaike Information Criterion' (AIC). Navedenom analizom ustanovljeno je da su odstupanja jednačine koju su predložili Zigrang i Silvester najmanja u odnosu na Kolbrukovu relaciju, a da je Halandova jednačina najpogodnija za inženjersku upotrebu.The most common explicit correlations for estimation of the friction factor in rough and smooth pipes are reviewed in this paper. Comparison of any friction factor equation with the Colebrook's equation was expressed trough the mean relative error, the maximal positive error, the maximal negative error, correlation ratio and standard deviation. The statistical comparison of different equations was also carried out using the 'Model selection criterion' and 'Akaike Information Criterion'. It was found that the equation of Zigrang and Sylvester provides the most accurate value of friction factor, and that Haaland's equation is most suitable for hand calculations

A review of explicit approximations of Colebrook's equation

U radu je dat pregled najčešće korišćenih eksplicitnih jednačina za određivanje koeficijenta trenja u glatkim i hrapavim cevima. Odstupanje navedenih jednačina od Kolbrukove jednačine izraženo je preko srednje relativne greške, maksimalne pozitivne greške, maksimalne negativne greške, srednjeg odstupanja i korelacionog odnosa. Osim navedenih kriterijuma, poređenje jednačina je izvršeno i korišćenjem 'Model selection criterion' (MSC) i 'Akaike Information Criterion' (AIC). Navedenom analizom ustanovljeno je da su odstupanja jednačine koju su predložili Zigrang i Silvester najmanja u odnosu na Kolbrukovu relaciju, a da je Halandova jednačina najpogodnija za inženjersku upotrebu.The most common explicit correlations for estimation of the friction factor in rough and smooth pipes are reviewed in this paper. Comparison of any friction factor equation with the Colebrook's equation was expressed trough the mean relative error, the maximal positive error, the maximal negative error, correlation ratio and standard deviation. The statistical comparison of different equations was also carried out using the 'Model selection criterion' and 'Akaike Information Criterion'. It was found that the equation of Zigrang and Sylvester provides the most accurate value of friction factor, and that Haaland's equation is most suitable for hand calculations

Techno-economic evaluation of residue exhaustion in batch rectification ethanol production plant

This paper presents the techno-economic optimization of batch plant for production of rectified alcohol based on the concentration of ethanol in residue. The aim of the analysis was to determine the extent to which it is economically profitable to exhaust the residual liquid in boiler. The "profit production" criterion is used for calculations

Rectified ethanol production cost analysis

This paper deals with the impact of the most important factors of the total production costs in bioethanol production. The most influential factors are: total investment costs, price of raw materials (price of biomass, enzymes, yeast), and energy costs. Taking into account these factors, a procedure for estimation total production costs was establish. In order to gain insight into the relationship of production and selling price of bioethanol, price of bioethanol for some countries of the European Union and the United States are given

Kriterijumi za dimenzionisanje separacionog prostora kod isparivača sa potopljenim cevnim snopom

Postoji više kriterijuma za dimenzionisanje separacionog prostora kod isparivača sa potopljenim cevnim snopom. Ovi kriterijumi su navedeni i komentarisani u radu. Dat je i numerički primer koji ilustruje upotrebu ovih kriterijum

Development of the heating system using geothermal energy

The paper presents the results achieved by the project financed by Ministry of Science and Environmental Protection of Serbia during the period 2003-2005. The purpose of the project was determination methodology for designing heating system using geothermal water. Achieved results were implemented in the demonstration installment in factory "Palanački kiseljak" in Smederevska Palanka, Serbia, using geothermal water from the well near by factory

CO2 EMISSION REDUCTION BY USING CORN AS A RAW MATERIAL IN REFINED ALCOHOL PRODUCTION

In the paper, we analyze the operation of a plant producing refined alcohol with a capacity of 25,000 kg/day, which uses corn as the primary raw material. On the site location, there are a cow farm, a plant for the combined production of heat and electricity using biogas, and a distillery production plant. The raw material for biogas is manure from a cow farm. The energy required for the production process and the operation of the supporting systems (space heating, own consumption of the CHP plant, etc.) is obtained by burning biogas and ethanol so that fossil fuels are used only in cases of plant start-up or incident situations of production process failure. The analysis presented in this paper aims to set up a carbon dioxide balance for a production plant with accompanying systems and its comparison to the carbon dioxide consumption necessary for corn's growth.IEEP-Industrijska energetika i zaštita životne sredine u zemljama jugoistočne Evrop

Development of the heating system using geothermal energy

The paper presents the results achieved by the project financed by Ministry of Science and Environmental Protection of Serbia during the period 2003-2005. The purpose of the project was determination methodology for designing heating system using geothermal water. Achieved results were implemented in the demonstration installment in factory "Palanački kiseljak" in Smederevska Palanka, Serbia, using geothermal water from the well near by factory

Thermoeconomic analysis of spiral heat exchanger with constant wall temperature

Thermoeconomic analysis of spiral heat exchanger is conducted. Different geometrical parameters, such as outer diameter, plate height, passage gap, etc. are used and varied in a wide range. Detailed thermal and total costs analyses were performed for two spiral heat exchanger with different process fluids (water and thermal oil) with temperature changes, while the wall temperature was kept constant (condensation). The results were shown graphically. It is determined that optimum values of number of entropy generation units correspond to minimum total annual cost. The optimal solution could be found in the recommended range of geometric sizes for defined inlet and outlet temperatures and process fluid-flow rate