Istraživanje tehničko-ekonomske vrijednosti otpadne biomase kao jednog od kriterija tehnološkog i energetskog razvoja drvoprerađivačkih pogona

A precise establishing of quantity, share, structure and place where wood waste appears considerably influences the speed and direction of technological and energy development of wood processing plants. Technical and economic value of waste biomass projects energy usage and efficiency of a production plant. Lack of experimental studies and usage of general empirical relations are often reasons of inadequate practical compatibility and connection of waste biomass with total efficiency of the plant. Based on studies carried out in eight plants in the Republic of Croatia, it was possible to determine quantity, type, share, structure and place of wood residue/waste appearance in relation to annual raw material processing. Thermal and electrical energy consumption was measured during the thermal processing of sawn timber. Numerical values expressed the fuel and economic value, depending on the quantity and structure of waste biomass. The research suggests a new diagram for determination of existing efficiency and parameters for technical and economic values of waste biomass as one of the criteria for technological and energy development of wood processing plants.Precizno utvrđivanje količine, udjela, strukture i mjesta nastanka drvnog otpada značajno utječe na brzinu i smjer tehnološko-energetskog razvoja drvoprerađivačkih pogona. Tehničko – ekonomska vrijednost otpadne biomase projicira energetsku uporabu i učinkovitost proizvodnog pogona. Nedostatak eksperimentalnih istraživanja i korištenjem poopćenih empirijskih relacija često je razlog nedovoljne praktične usklađenosti i povezanosti otpadne biomase s ukupnom učinkovitosti pogona. Na temelju provedenih istraživanja u osam drvoprerađivačkih pogona u Republici Hrvatskoj kvantificirano su utvrđene količina, vrsta, udjel, struktura i mjesto nastanka drvnih otpadaka u odnosu na godišnju preradu sirovine. Izmjerena je potrošnja toplinske i električne energije pri toplinskoj obradi piljenog drva. Numeričkim vrijednostima iskazana je ogrjevna i ekonomska vrijednost ovisno o količini i strukturi otpadne biomase. Predložen je novi dijagram za utvrđivanje postojeće učinkovitosti i parametara tehničko-ekonomske vrijednosti otpadne biomase kao jednog od kriterija tehnološko-energetskog razvoja drvoprerađivačkih pogona

Risk Management in the Higher Education Quality Insurance System

Due to the factors that affect the results of work on a daily basis, higher education institutions, through their quality assurance systems, or their planning, must assess risks. In doing so, they must take into account all issues of the internal and external context as well as the needs and expectations of all stakeholders in higher education. The paper explains in an appropriate way the concept of risk as well as all the elements that determine it and their classification in the field of higher education. Subsequently, a possible approach to risk management is discussed, with an emphasis on clarifying the principles and the risk management process itself. Finally, the basics of practical application in risk identification, analysis, evaluation and treatment are outlined

Experimental and Numerical Investigation of Centrifugal Vortex Pump Operating Benefits for Energy Efficient Systems

One of the ways to improve the performance of centrifugal pumps, proposed and experimentally validated by our research, is the method of creating so-called coherent structures, vortices and turbulence in the peripheral area of the centrifugal stage by adding a vortex rim to the back side of centrifugal rotor. A new construction of the pump, so called centrifugal vortex pump (CV), combines the good sides of these two types of pumps: high head of the vortex pump and high efficiency of the centrifugal pump. In addition, centrifugal pumps deliver higher flow rates with lower pressures, vortex pumps deliver higher pressures but with lower flow rates. For centrifugal vortex pumps, the vortex blades are located at the rear of the centrifugal rotor. The outer diameter of the vortex rim (VR) is smaller than the outer diameter of the centrifugal rotor (CR). The vortex rim induces vorticity to a portion of the flow that has passed through the centrifugal rotor. This vortexed flow is then reunited with the rest of the flow that has not been pulled down by vortex rotor. The vortex energy of that additional stream transfers some of its kinetic energy to the main stream. This added kinetic energy is converted to a pressure that accumulates the pressure exerted by the centrifugal rotor, and thus the vortex rim improves the overall pump performance. An intense process of gas dispersion occurs in the vortex region, which increases the stability of the pump when pumping a mixture of liquids and gases. The process of energy conversion in a centrifugal vortex pump, i.e., flow visualisation of mixing streams from a centrifugal rotor and a vortex rotor, and the quantization and superpositions have been shown in this paper

Application of thermoelectric modules as renewable energy sources

Thermoelectric modules are used for heating or cooling if an electric current flows through them. If one side of such a module is heated and the other side is cooled, the outputs show a potential difference that creates the current flow through an enclosed circuit. The paper describes briefly the physical basis of the operation of semiconductor thermoelectric modules and their application for generating electricity as thermoelectric generators. The experimental measurements were made with different available modules of thermoelectric generators. The analysis of obtained results has provided the conclusions about the possibility of their application as sources of electricity. Although the efficiency of thermoelectric modules is still quite low, the latest research reveals the possibility of the use of materials that make modules more efficient. Considering the fact that they do not contain moving parts, they are characterized by reliable, long-lasting work and simple operation and maintenance

Korištenje alata za poboljšavanje kvalitete u Hrvatskoj metaloprerađivačkoj industriji

Modern production requires a daily monitoring process and seeks its continuous improvement in order to increase the quality, and therefore effectiveness. There are various tools and their use should become a daily routine to help participants in the process at all levels; from management to production workers. For the purpose of analyzing the frequency of use and confirming the insufficient use of tools and methods of improvement, a research was conducted among Croatian metal processing manufacturers. The research has confirmed a low frequency of tool use, but has also provided some guidelines for increasing their use in the future.Suvremena proizvodnja iziskuje svakodnevno praćenje procesa te teži njihovom kontinuiranom poboljšavanju kako bi se povećala njihova kvaliteta, a samim time i efektivnost. Alati koji se koriste su raznovrsni i njihovo korištenje trebalo bi postati svakodnevnica kako bi pomogle sudionicima procesa na svim nivoima proizvodnje od uprave do radnika u neposrednoj proizvodnji. U svrhu analize učestalosti korištenja i dokazivanju premalog korištenja alata i metoda poboljšavanja provedeno je istraživanje unutar hrvatskog metaloprerađivačkog sektora. Istraživanjem je dokazana premala učestalost korištenja alata, ali i daje neke smjernice za povećanje korištenja u budućnosti

Validacija realizirane mjerne nesigurnosti u postupku umjeravanja preciznih mjernih skala

Laboratorij za precizna mjerenja dužina koji je ujedno i Nacionalni laboratorij za duljinu sudjeluje (Laboratorij) CIPM MRA (Comité International des Poids et Mesures, Mutual Recognition Arrangement) ključnim usporedbama etalona duljine među kojima su od posebnog značaja i precizne mjerne skale. U usporedbenim mjerenjima pri iskazivanju rezultata mjerenja, neophodno je dati i procjenu mjerne nesigurnosti. U novije vrijeme, Monte Carlo simulacije (MCS) imaju sve veću primjenu u procjeni mjernih nesigurnosti. U radu se prezentira validacija realizirane mjerne nesigurnosti GUM metodom upotrebom MCS metode. MCS metoda temelji se na generiranju slučajnih brojeva iz funkcija gustoće vjerojatnosti za svaku ulaznu veličinu i stvaranju eksperimentalne funkcije gustoće vjerojatnosti izlazne veličine kombinirajući različite razdiobe kojima su definirane ulazne veličine. Isto tako, u radu se prezentiraju rezultati međunarodnog usporedbenog mjerenja koji predstavljaju stvarnu validaciju mjernog uređaja i procijenjene mjerne nesigurnosti

The choice of the optimum alternative of the process results quality control

Efikasna kontrola kvalitete rezultata procesa zahtijeva pravilan odabir vrste kontrole koja ovisi o: fazi poslovanja, periodu u kojem se izvodi, predmetu kontrole, kontroliranim parametrima, sustavu i razini kontrole, pristupu kontroli, tipu i planu kontrole te primijenjenim normama. U članku se obrađuju navedena pitanja s ciljem iznalaska optimalne varijante kontrole.An effective quality control of the process results requires the right choice regarding the type of control that depends on the following: the business stage, a period when it is implemented, the subject of control, controlled parameters, the control system, the control level, the control approach, the control plan type, the control plan, and the standard. This article discusses the aforementioned issues with the aim of finding the optimum control alternative

Istraživanje i rangiranje utjecajnih faktora na primjenu 6σ metodologije u malim proizvodnim organizacijama metodom apriornog rangiranja faktora

Ranking of factors that mostly influence the non-use of the 6σ-Methodology in small production organizations was conducted using the method of prior factor ranking. The method resulted in identifying factors which have a dominant impact in order to decrease it.Metodom apriornog rangiranja faktora izvršeno je rangiranje faktora koji najviše utječu na neprimjenu 6σ metodologije u malim proizvodnim organizacijama. Na taj se način došlo do faktora koji imaju dominantan utjecaj s ciljem poduzimanja mjera smanjivanja njihovog utjecaja