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Star-shaped fins are a newer type of fin for which correlations for heat transfer and pressure drop do not yet exist in the literature. Therefore, correlation equations for air-side heat transfer and pressure drop in a finned heat exchanger with star-shaped stainless-steel fins in staggered arrangement were developed in this work. To obtain these correlations, a numerical analysis of the basic heat exchanger geometry and another 21 variants of heat exchanger geometry was performed using computational fluid dynamics, and then the results of laboratory tests of a model of heat exchangers with star-shaped fins were used. In the numerical analysis, the fin pitch, the fin thickness, and the air velocity at the inlet to the heat exchanger were varied. The Nusselt (Nu) and Euler (Eu) numbers were determined for each variation analyzed. Initial correlations for Nu and Eu were derived using the least-squares deviation method. The correlation coefficients thus obtained were adjusted to agree with the results of the laboratory tests. The deviation of the final obtained correlation for Nu from the experimental test results was up to 10% in the range of Re &lt, 3500, whereas for higher values of Re, the deviation was less than 2%. The Eu correlation deviated from experimental results up to 19% in the range of Re &lt, 4000, whereas in the range of Re &gt, 5600, the deviation was less than 1%. The correlations were valid in the range 2000 &lt, Re &lt, 16,000.

Building energy management system (BEMS) integrated in building is of great importance in modern nearly zero energy buildings (nZEB). Nearly zero energy standard describes energy efficiency concept with energy conservation and energy savings. In this work, an upgrade of the BEMS with goal of reduction of cooling energy demand for the building of the Mechanical Engineering Faculty in Slavonski Brod, object in Ivana Gundulica Street is proposed. BEMS controls ventilation system of below roof/attic area. Described technical solution is designed inside RESCUE IPA CBC project (Faculty of Technical Science Novi Sad, Faculty of Electrical Engineering, Computer Science and Information Technology Osijek).

Increase of the heat flow rate by applying finned surfaces is common in gas-liquid heat exchangers. Thereby, devices with annular fins are frequently used. Demands for higher capacity lead to size and mass increase of heat exchangers which over time becomes a significant problem, especially if the application of stainless steel is required. The solution to this problem is in a more efficient heat exchange on the gas side. This paper analyses the application of stainless steel star-shaped fins which increase the turbulence of fluid flow with their shape and in that way the heat exchange. For this purpose, two heat exchangers of identical size were made: one with annular fins and one with star-shaped fins. Both heat exchangers were experimentally tested with the same equipment and under identical conditions in the Reynolds number range from 2000 to 13,000. The test results indicate an increase in the heat flux by 39.3% when applying the star-shaped fins relative to annular fins, with the reduction of the heat exchanger mass by 23.8%.

Opisan je novi geometrijski oblik lamele (igličaste lamele) za orebrene cijevne izmjenjivače topline plin – tekućina pomoću kojeg se postiže veći koeficijent prijelaza topline, a time i manja masa izmjenjivačkih površina u odnosu na izmjenjivače topline s okruglim lamelama koji su u ovom slučaju poslužili kao baza za usporedbu. Za analizu izmjene topline i pada tlaka primijenjena je računalna dinamika fluida s programom ANSYS Fluent. Numerička simulacija provedena je za slučaj zagrijavanja zraka koji struji oko cijevi s lamelama novog geometrijskog oblika te oko cijevi s lamelama konvencionalnog kružnog oblika brzinama od 1 m/s do 5 m/s. Rezultati numeričke simulacije obzirom na izmijenjenu toplinu i pad tlaka za cijevi s okruglim lamelama provjereni su pomoću korelacija dostupnih u literaturi te su uspoređeni s rezultatima simulacije za cijevi s inovativnim lamelama. Rezultati pokazuju povećanje iznosa Nu značajke od 20 % do 30 % za 2300 > Re > 12000 uz smanjenje mase izmjenjivačkih površina od 23,8 %., A new geometric form of fins (needle fins) for finned heat exchangers of gas-liquid type is described. It achieves a higher heat transfer coefficient and lower mass of the heat exchange surface relative to the heat exchangers with circular fins which in this case served as a basis for comparison. For the analysis of the heat transfer, the computational fluid dynamics analysis with ANSYS Fluent software was applied. Numerical simulation was performed for the round fins and fins with a new, innovative geometric shape at air flow speeds of 1 m/s to 5 m/s. The results of numerical simulations, with regard to the exchanged heat and pressure drop were verified by the correlations available in the literature and compared to the simulation results for tubes with innovative fins. Results show an increase in the amount of Nu from 20 % to 30 % for 2300 >Re > 12000 while reducing mass of heat exchange surfaces of 23,8 %.

Načela aditivne proizvodnje su takva da omogućuju izradu vrlo komplicirane geometrije proizvoda. Krutost printanih dijelova ne raste proporcionalno povećanju ispuna samih dijelova. Načini printanja imaju veći utjecaj na krutost od same ispune. Provedenim ispitivanjima na uzorcima "punog" modela utvrđena je zadovoljavajuća krutost dijelova dobivenih 3D printanjem uz manje utrošenog materijala i kraće vrijeme izrade pravilnim izborom parametara i načina printanja., The principles of additive production are such that they enable the making of very complex product geometry. The hardness of printed parts is not increased proportionally to the increase of the infill of the parts themselves. Different ways of printing have a bigger impact on the hardness than the infill. The research conducted on the "solid" model samples established sufficient hardness of parts gained from 3D printing with less material use and shorter time of production due to correct selection of parameters and the way of printing.

The article compares the tube heat exchanger with annular fins with innovative star shaped fins. For the analysis of the heat transfer and pressure drop, the computational fluid dynamics analysis with ANSYS Fluent software was applied. Through the tubes flow the hot water and heat the cold air flowing around the fins and tubes. The validation of selected turbulence models (k-ω SST and k-e Realizable) was performed by annular fins comparing with the results in the literature. The results of the numerical analysis for star shaped fins for 2200

Određivanje distribucije temperaturnih polja kod elektrolučnog zavarivanja taljenjem je vrlo važno zbog njihovog utjecaja na mehanička svojstva i kvalitetu zavarenih spojeva. U radu se prikazuju analitički modeli za 2D i 3D vođenje topline temeljeni na rješenjima Fourierove diferencijalne jednadžbe za vođenje topline. Pored toga, autori daju pojednostavljene jednadžbe za proračun trajanja hlađenja i brzine hlađenja za 2D i 3D modele vođenja topline., It is of high importance to determine the distribution of thermal fields in arc fusion welding processes due to their influence on mechanical properties and quality of welded joints. This paper presents analytical models for 2D and 3D heat conduction based on solutions of the Fourier’s heat conduction differential equation. Furthermore, authors provide simplified equations for the calculation of cooling time and cooling rate for 2D and 3D heat conduction models.

Provedena su istraživanja pri spaljivanju šest različitih skupina biomase, svaka skupina za tri slučaja prosječne početne vlage u cilju kvantificiranja vrijednosti utjecajnih parametara i doprinosa povezanosti kakvoće biomase s učinkovitosti termoenergetskog sustava. Korišteno je toplovodno postrojenje toplinske snage Q = 600 kW sa toplifikacijskim sustavom niskoakumulativnog objekta s malom termofizikalnom karakteristikom i vremenskom konstantom.Istraživanja su provedena u osamnaest jednakih ciklusa pri niskim vanjskim temperaturama zraka i maksimalnoj potrebi korisne toplinske energije. Kvantificiranim vrijednostima utvrđena je potrošnja svih skupina i prosječne vlažnosti biomase. Analizom ispitivane temperature ogrjevnog medija i dimnih plinova pri izgaranju svake skupine biomase prikazan je izravan utjecaj njene kakvoće i prosječne vlage na održivost i stabilnost toplifikacijskog sustava. Predložena je najpovoljnija biomasa. Izravnom primjenom rezultata istraživanja doprinosi se pravilnom određivanju vrste, sastava i prosječne vlage biomase, te većoj učinkovitosti cjelovitog termoenergetskog sustava., Research was conducted during the incineration of six different biomass groups, whereat each group was observed for three cases of average initial moisture level for the purpose of quantifying the values of impact parameters and contribution to the correlation between biomass quality and the efficiency of a thermal power system. A hot water plant with the power to heat ratio amounting to Q = 600 kW was used, which included a district heating system of a low-accumulation object with a low thermophysical constant and a low time constant. Research was conducted in 18 equal cycles at low outside air temperatures and a maximum need for useful thermal energy. Quantified values showed the consumption of all groups of all average moisture levels of biomass. By analysing the examined temperature of a heating medium and flue gases during the combustion of each biomass group, a direct influence of its quality and average moisture on the sustainability and stability of the district heating system was shown. The most favourable biomass was proposed. Direct application of research results contributes to correct determination of the type, composition and average moisture of biomass, as well as a higher efficiency of the whole thermal power system.

A low time constant and thermophysical characteristic of low-accumulation objects significantly increases the sensitivity of the inside air temperature in the area of cultivation of agricultural products to external, especially sudden, microclimate changes. Inversely proportional rate of heating and cooling an object considerably reduces the efficiency of the district heating system and the production cost-effectiveness. With custom software support experimental research was conducted in a limited period of time at three objects (GH1, GH2 and GH3) in different locations and the impact of the district heating system on the rate of achieving the mean daily internal air temperature under average external microclimate conditions in the winter period and the technologically most sensitive period for plant cultivation was analyzed and compared with and without a heat tank. By using the accumulated thermal energy from the heat tank, around 50% faster mean values of daily inside air temperature are achieved as compared to the minimally allowed inside air temperature. The consumption of thermal energy and biomass is about 23 % to 28 % higher in the operation of thermal power plants without heat tank, while thermal capacity is about 25 % higher per unit area of the heated area for the same purpose. Direct application of research results contributes to more appropriate sizing and shaping of accumulation heat tanks and a greater efficiency and cost-effectiveness of heat energy systems of low-accumulation objects of various and strict technological requirements., Mala vremenska konstanta i termofizikalna karakteristika niskoakumulativnih objekata izrazito povećavaju osjetljivost unutarnje temperature zraka u zoni uzgoja agro kultura na vanjske, naročito nagle, mikroklimatske promjene. Obrnuto proporcionalna brzina grijanja i hlađenja objekta značajno smanjuje učinkovitost toplifikacijskog sustava i ekonomičnost proizvodnje. Uz prilagođenu softversku podršku provedena su eksperimentalna istraživanja u ograničenom vremenskom intervalu na tri objekta (GH1, GH2 i GH3) na različitim lokacijama te je analiziran i uspoređen utjecaj toplifikacijskog sustava sa i bez spremnika topline na brzinu postizanja srednje dnevne unutarnje temperature zraka pri prosječnim vanjskim mikroklimatskim uvjetima u zimskom periodu i tehnološki najosjetljivijem uzgojnom periodu biljaka. Korištenjem akumulirane toplinske energije iz spremnika topline postižu se za oko 50 % brže srednje vrijednosti dnevne unutarnje temperature zraka od minimalno dopuštene unutarnje temperature zraka. Potrošnja toplinske energije i biomase je za oko 23 % do 28 % veća pri pogonu termoenergetskog postrojenja bez spremnika topline i veće toplinske snage za oko 25 % po jedinici površine grijanog prostora iste namjene. Izravna primjena rezultata provedenih istraživanja doprinosi svrhovitijem dimenzioniranju i oblikovanju akumulacijskih spremnika topline te većoj učinkovitosti i ekonomičnosti toplifikacijskih sustava niskoakumulativnih objekata različitih i strogih tehnoloških zahtjeva.

This article presents the dimensioning and 3D modeling of a swing check valve with lever and weight in welded design, based on the existing 2D workshop documentation in cast design and reverse engineering. Based on analytical calculations, pipe wall thickness of a swing check valve housing was selected for the nominal pipe diameter DN 300 and water test pressure p = 2.4 MPa. All 3D models of components, as well as the assembly, were made in the program tool SolidWorks. The 3D model of the swing check valve with flanges was subjected to stress analysis (Finite Element Analysis) for the purpose of checking the accuracy of the analytical calculations. Fluid flow analysis (Flow Simulation) was used for presenting fluid flow process and rate through the swing check valve assembly. A low-budget 3D MakerBot Replicator 2X printer was used for constructing a reduced-scale 3D assembly model of the swing check valve with lever and weight, by implementing the FDM (Fused Deposition Modeling) technology., Prikazano je dimenzioniranje i 3D oblikovanje povratne zaklopke s polugom i utegom u zavarenoj izvedbi na temelju postojeće 2D radioničke dokumentacije u lijevanoj izvedbi i reverznog inženjeringa. Na temelju analitičkog proračuna odabrana je debljina stjenke cijevi kućišta povratne zaklopke za nazivni promjer cijevi DN 300 i vodni ispitni tlak p = 2,4 MPa. Svi 3D modeli dijelova, kao i sklop, izrađeni su u programskom alatu SolidWorks. Na 3D modelu kućišta povratne zaklopke s prirubnicama u zavarenoj izvedbi provedena je analiza naprezanja (Finite Element Analysis) sa svrhom provjere točnosti analitičkog proračuna. Analizom strujanja fluida (Flow Simulation) prikazan je tijek i brzine strujanja fluida kroz sklop povratne zaklopke. Na niskobudžetnom 3D MakerBot Replicator 2X pisaču, primjenom FDM tehnologije taložnog očvršćivanja materijala, izrađen je umanjeni 3D model sklopa povratne zaklopke s polugom i utegom.

Razni modeli manipulatora često se koriste u industrijskim pogonima i tehnologijama. Prikazana je mogućnost uporabe i usporedbe novih metoda upravljanja aktuatorima. Za izvedeni TTT manipulator neophodno je utvrditi standardne kataloške podatke. Glavna karakteristika pri upotrebi ovakvih manipulatora je njihov stabilan odziv u regulaciji pozicioniranja. Pokusno mjerenje provodi se s različitim mehaničkim opterećenjima, uglavnom koncentriranih u okolini standardnog mehaničkog opterećenja korištenog za simulaciju modela industrijskih pogona. Prikazani su rezultati provedenog eksperimenta najveće dostupne stabilne brzine koračnog motora za najopterećeniju os modela TTT manipulatora. Određivanje stabilnosti provedeno je do dvostrukog standardnog mehaničkog opterećenja. Najveću utvrđenu stabilnu brzinu motora moguće je koristiti za sve ostale osi bez utjecaja na stabilnost obzirom da je eksperiment proveden za mehanički naojopterećeniju os., The various models of manipulators are commonly used in industry plants and technologies. Possibility of applying and comparing such new methods is presented for actuator control. For produced TTT (Translation-Translation-Translation) manipulator it is necessary to determine standard catalogue information. The main issue in usage of such manipulators is stabile positioning regulation. The test survey is conducted with various mechanical loads, mainly concentrated in close surrounding of standard mechanical load used for simulations of industry models. Results of the highest available stabile speed of stepper motor are presented for the worst axis case of the model of TTT manipulator. The stability determination is conducted up to double standard mechanical load. The result of highest stabile motor speed can be applicable on all other axis with no influence on stability, since experiment is conducted on most mechanically loaded axis.

Provedena je analiza i izbor najpovoljnijeg energenta za izgaranje i pretvorbu u toplinsku energiju za tehnološke potrebe, grijanje i pripremu PTV – e proizvodnog pogona u kontinentalnom klimatskom području. Analizirani energenti su: prirodni plin, bioplin, drvna sječka, peleti i ekstra lako loživo ulje. I uz 1,5 – 2,0 puta veća investicijska ulaganja u termoenergetsko postrojenje obnovljiva drvna sječka je ekološki i ekonomski najpovoljnije pogonsko gorivo za proizvodnju toplinske energije. U tom slučaju cijena 1 kWh toplinske energije je višestruko manja (3 – 7 puta) od cijene 1 kWh toplinske energije dobivene izgaranjem ostalih analiziranih pogonskih goriva. Rast jedinične cijene drvne sječke osjetljivo ne utječe na održivost i ekonomičnost cijene 1 kWh toplinske energije. Emisija štetnih plinova u okolinu je najmanja., The analysis and selection of the most favorable energy generating product for the combustion and transformation into thermal energy for technological needs, heating and preparation of consumable hot water (CHW) of a production plant in the continental climate area were carried out. The analyzed energy generating products are: natural gas, biogas, wood chips, pellets and extra light heating oil. Even with 1.5 – 2.0 times higher investments in thermal energy plant, renewable wood chips are, from the ecological and economical perspective, still the most favorable drive fuel for the production of thermal energy. In this case the price of 1kWh of thermal energy is several times lower (3 – 7 times) than the price of 1kWh of thermal energy obtained by the combustion of other analyzed drive fuels. The increase in the unit price of wood chips does not strongly affect the sustainability and cost–efficiency of the price of 1 kWh of thermal energy. The emission of harmful gases into the environment is the lowest.

Prikazana i analizirana je pozicija ugradnje cirkulacijske pumpe u toplovodnom termotehničkom sustavu s otvorenom ekspanzijskom posudom. Istaknut je značaj neutralne točke O u termotehničkom sustavu sa aspekta cirkulacije tople vode, visine postavljanja (dovoljan statički tlak) otvorene ekspanzijske posude, te stabilnog rada termotehničke instalacije. Opisane su moguće pozicije ugradnje cirkulacijske pumpe (statički i dinamički tlak) u termotehničkoj instalaciji u odnosu na neutralnu točku O. Predloženo je najpovoljnije tehničko rješenje primjenjivo u praksi., The circulator pump installation in a water heating thermal technical system with open expansion vessel is presented and analyzed. The significance of the neutral point O in the thermal technical installation is highlighted from the aspect of hot water circulation, installation height (sufficient static pressure) of the open expansion vessel, and stable operation of the thermal technical installation. Possible circulator pump installation positions (static and dynamic pressure) in the thermal technical installation are described in relation to the neutral point O. The most favorable technical solution applicable in practice is proposed.

In the processing industry high viscosity media are transferred by using very expensive worm-drive pumps whose form and characteristics are adapted to the standardized packaging of the media. A significantly cheaper and simpler device with a worm coil has been designed for the purpose of transporting media of various viscosities. Experimental transferring was carried out on a limited number of media samples of various viscosities. The functionality of the device was confirmed. The results of the experiment during the operation of the device with two versions of worm coils (1 and 2) were compared. Guidelines for further research and possible development of an applicable device were proposed., U prerađivačkoj industriji se za pretakanje visokoviskoznih medija koriste veoma skupe zavojne pumpe oblikom i karakteristikama prilagođene standardiziranoj ambalaži medija. Osmišljen je znatno jeftiniji i jednostavniji uređaj s pužnom zavojnicom za transport medija različite viskoznosti. Provedena su pokusna ispitivanja pretakanja na ograničenom broju uzoraka dostupnih medija različite viskoznosti. Utvrđena je funkcionalnost uređaja. Uspoređeni su rezultati ispitivanja pri radu uređaja sa dvije izvedbe pužne zavojnice (1 i 2). Predložene su smjernice daljnjeg istraživanja i mogućeg razvoja primjenjivog uređaja.

Sušenjem higroskopnih materijala, a naročito voća (borovnica, kupina, malina, itd.) i nekih vrsta povrća u vakuumskim sušarama zračenjem pri niskoj temperaturi, zadržavaju se njihova izvorna kakvoća i ljekovita vrijednost. Provedena su pokusna istraživanja primjenom metode kapacitivnog mjerenja snižavanja vlage plodova borovnice sušenih u vakuumu u cilju provjere metode i doprinosa mogućem razvoju primjenjivih uređaja. Korištena je realna vakuum komora sa zračećim pločastim električnim grijačima i pripadajućom funkcionalnom i regulacijskom opremom. Projektirani i izrađeni su mjerni senzori te je sklopljen i programiran mjerni uređaj. Promjenom vrlo malih vrijednosti električnog kapaciteta potvrđena je mogućnost mjerenja snižavanja vlage plodova borovnice pri provedbi režima sušenja. Istaknuta je uska povezanost preciznosti regulacije radnih parametara (podtlak, temperatura) u komori s točnosti mjerenja vlažnosti materijala. Interdigitalnim senzorom postignuta je prihvatljiva osjetljivost mjerenja vlažnosti sušenog materijala. Predložene su smjernice daljnjeg istraživanja i mogućeg razvoja primjenjivog mjernog uređaja., Dehydration of hygroscopic materials, especially fruit (blueberries, blackberries, raspberries, etc.) and some types of vegetables in vacuum dehydrators by means of radiation at low temperatures preserves their original quality and medicinal value. Experimental research has been carried out, whereby the moisture reduction of vacuum-dried blueberry fruits was measured by applying the capacitive measuring method, in order to check the method and contribute to possible development of applicative devices. A real vacuum chamber with radiating plate electric heaters and additional functional and regulation equipment was used. Measuring sensors were projected and made, and a measuring device was assembled and programmed. By changing very low values of capacitance, the possibility of measuring moisture reduction in blueberry fruits during drying was confirmed. A close connection between the regulation precision of working parameters (subpressure, temperature) in the chamber and the accuracy of measuring the material moisture was underlined. By using an interdigital sensor acceptable sensitivity in measuring the moisture of dried material was achieved. Guidelines for further research and possible development of an applicable measuring device were suggested.

In lime production drive fuel is the most significant factor in determining the price, competitiveness and sustainability of a product on the market. The comparison and analysis of partial or total usage of synthetic gas obtained by wood chips gasification were carried out. The technological process of lime production in the Maerz furnace was described, and fundamental technical and economic parameters of using and/or substituting natural and synthetic gas were graphically and analytically presented. The impact of price alterations and distance radius related to the supply of wood chips on annual drive fuel costs was analyzed. The reduction in annual drive fuel costs by using synthetic gas was quantified. A full analysis of the applicability of wood chips gasification plant from the aspect of technical and technological conditions, cost-effectiveness, sustainability and ecological effectiveness within a concrete lime production process is required., U proizvodnji živog vapna pogonsko gorivo je najutjecajniji faktor u formiranju cijene, konkurentnosti i održivosti proizvoda na tržištu. Uspoređeno je i analizirano djelomično ili potpuno korištenje sintetičkog plina dobivenog rasplinjavanjem drvne sječke. Opisan je tehnološki proces proizvodnje živog vapna u Maerzovoj peći, te su grafički i analitički prikazani osnovni tehnički i ekonomski parametri korištenja i/ili supstitucije prirodnog i sintetičkog plina. Analizirani su utjecaji promjene cijena i polumjera udaljenosti dobave drvne sječke na godišnje troškove pogonskog goriva. Kvantificirano je smanjenje godišnjih troškova pogonskog goriva primjenom sintetičkog plina. Nužna je cjelovita analiza primjenjivosti postrojenja za rasplinjavanje drvne sječke s aspekta tehničkih i tehnoloških uvjeta, ekonomičnosti, održivosti i ekološke učinkovitosti u konkretnoj proizvodnji živog vapna.

U radu je prikazan pregled i mogućnost primjene kvantitativnih metoda kod izbora materijala za nove i za postojeće proizvode. Prikazane su razlike u pristupu kod izbora materijala za nove proizvode i za postojeće proizvode. Kvantitativne metode pomažu u postizanju većeg stupnja objektivnosti kod izbora materijala. Primjena kvantitativnih metoda izbora materijala pretpostavlja postojanje i poznavanje brojčanih podataka o svojstvima materijala. Poznavanje funkcije, odnosno uvjeta rada nužno je za realnu procjenu težinskih faktora za svako svojstvo. Na primjeru stvarnog proizvoda pokazana je praktična primjena metode utjecajnosti svojstava za materijale košuljice (tijela) i vijaka vijčane pumpe., This paper presents an overview of quantitative methods and their application possibilities in selecting materials for new and existing products. Differences in the approach to selecting materials for new and existing products are shown. Quantitative methods are helpful in achieving a higher objectivity level in material selection. The application of quantitative methods in material selection requires the existence and knowledge of numerical data related to materials' properties. Knowing the function, i.e. operative conditions, is essential for weight factors to be assessed realistically for each property. An example of a real product was used for presenting the practical application of the properties' impact method regarding the cylinder (body) and pump screws materials.

Skromna je cjelogodišnja intenzivna proizvodnja povrća u zatvorenim prostorima s kontroliranim uvjetima, često neadekvatnih termotehničkih rješenja, s velikom potrošnjom i visokim troškovima energije. Proizvodni ciklus se ograničava na topliji dio godine kada su troškovi energije manji što značajno smanjuje ekonomičnost, kakvoću prinosa, konkurentnost i dugoročni opstanak proizvođača na tržištu. Bjelovarsko-bilogorska županija i susjedne županije raspolažu značajnim potencijalom obnovljivih izvora energije (biomasa, geotermalna energija) koji se multiplikativno ne usmjeravaju podizanju proizvodnih djelatnosti, a posebno intenzivnom uzgoju povrća u plastenicima. Nedostatak egzaktnih istraživanja i korištenje načelnih procjena često su razlog nedovoljnog praktičnog vrjednovanja biomase i geotermalne energije i mogućeg doprinosa ekonomičnoj intenzivnoj proizvodnji povrća. Provedena su istraživanja raspoloživosti šumske i biljne biomase, drvnih ostataka u drvoprerađivačkim pogonima te geotermalnog potencijala u Bjelovarsko-bilogorskoj županiji iskoristivih u energetskoj opskrbi centraliziranih i/ili decentraliziranih objekata (plastenika) za intenzivnu proizvodnju povrća. Analiziran je održivi ekonomični polumjer prikupljanja, pripreme i dobave obnovljive biomase. Prikazana i analizirana je potrošnja i ekonomičnost toplinske energije iz različitih vrsta pogonskog goriva usporediva s izravno primjenjivim obnovljivim izvorima energije. Kvantificiranim vrijednostima istaknuta je komplementarnost raspoloživih obnovljivih izvora energije s razvojem cjelogodišnje intenzivne proizvodnje povrća u plastenicima., The perennial intensive production of green food (fruit and vegetables), realised indoors, under controlled conditions, often with inadequate thermo-technical solutions, considerable consumption and high energy costs, is rather modest. The production cycle is limited to the warmer period when energy costs are lower, which reduces to major extent cost-effectiveness, yield quality, competitiveness and long-term presence on the market. The Bjelovar-Bilogora County and its neighbouring counties have at their disposal a major potential of renewable energy sources (biomass, geothermal energy), which are not directed towards the enhancement of production-related activities, in particular the intensive production of green food. The lack of exact research and the use of general assessments are often the cause of insufficient practical valuation of biomass and geothermal energy, as well as the possible contribution to cost-effective intensive production of green food. Research has been carried out regarding the availability of forest and plant biomass, wood residue in wood processing plants and geothermal potential in the Bjelovar-Bilogora County, usable for supplying the centralised and/or decentralised facilities (polythene greenhouses) for the intensive production of fruit and vegetables with energy. The sustainable cost-effective diameter of collecting, preparing and providing renewable biomass was analysed. The consumption and cost-effectiveness of thermal energy from diverse types of propellants, comparable to directly applicable renewable energy sources, were presented and analysed. By the means of presenting quantified values, the complementariness between the available energy sources and the development of the perennial intensive production of green food and other activities in the Bjelovar-Bilogora County was pointed out.

Prikazan je postupak projektiranja, izrade 3D modela i testiranje 3 osne CNC glodalice kao stroja za maloserijsku izradu dijelova pločastog namještaja od iverala i medijapana. Na temelju kreiranog 3D modela i realizacijom prototipa, provedeno je testiranje radnih karakteristika glodalice te postupak izrade G-koda i strojne obrade izradom logotipa Visoke tehničke škole u Bjelovaru., The procedure of designing, creating 3D models and test the 3 axis CNC milling machine, a machine for small series production of furniture parts from chipboard and MDF. Based on the created 3D models and prototype implementation was carried out performance testing of routers, and the procedure of G - code and machining Logo "Technical high school in Bjelovar."

High costs, irrational consumption of thermal energy and low efficiency are often characteristics of sawn timber drying by warm humid air in chamber drying kilns. A weak link between technological planning with the sawn timber mass dynamics in the systems with more drying kilns is the most common reason that influences considerably the economy of timber thermal processing and the heat source pre-dimensioning. Lack of experimental research and usage of general relations are common reasons for insufficient practical compliance and connection of drying thermal needs and the heat source capacity. Air heater thermal load has been researched during the sawn oak timber drying, 25 mm thick, as well as 32 mm and 50 mm thick beech, by applying of appropriate regimes during all the stages in more cycles of convective drying. Current thermal needs have been measured and registered in relation to maximal values during the characteristic intervals of each drying cycle. The exact values have been shown, while the defined correlation polynome has been used to describe a graphic and mathematical model of thermal load in all intervals of tested sawn timber drying cycles. An analytical procedure for determination of total maximal thermal needs of more drying kilns has been suggested based on timber moisture decreasing and technological drying planning. Using a characteristic example, its applicability and contribution to an optimal thermal source dimensioning has been shown., Viši troškovi, neracionalna potrošnja toplinske energije i mala učinkovitost česte su značajke sušenja piljenog drva toplim vlažnim zrakom u komornim sušarama. Slaba povezanost tehnološkog planiranja s dinamikom sušenja piljene drvne mase u sustavima s više sušara najčešće značajno utječe na ekonomičnost toplinske obrade drva i predimenzioniranje izvora topline. Nedostatak eksperimentalnih istraživanja i korištenjem općih relacija česti su razlozi nedovoljne praktične usklađenosti i povezanosti toplinskih potreba sušenja i kapaciteta izvora topline. Provedena su istraživanja toplinskog opterećenja grijača zraka pri sušenju piljenog drva hrasta debljine 25 mm te bukve debljine 32 mm i 50 mm, primjenom odgovarajućih režima tijekom svih faza u više ciklusa konvektivnog sušenja. Izmjerene su i registrirane trenutne toplinske potrebe u odnosu na maksimalne vrijednosti tijekom karakterističnih intervala svakog ciklusa sušenja. Prikazane su egzaktne vrijednosti, a pridruženim korelacijskim polinomom opisan je grafički i matematički model toplinskog opterećenja u svim intervalima ispitivanih ciklusa sušenja piljenog drva. Predložen je analitički postupak za određivanje ukupnih maksimalnih toplinskih potreba više sušara na osnovu dinamike snižavanja vlage drva i tehnološkog planiranja sušenja. Karakterističnim primjerom je prikazana njegova primjenjivost i doprinos optimalnom dimenzioniranju izvora topline.

Prikazana je izrada 3D modela proizvoda - Vrcaljke za med, uključivo i slijed izrade složenijih dijelova i montažnih sklopova. Predložena su moguća poboljšanja primjenom prozirnih materijala i pogona vrcaljke. Izradom 3D modela i generiranjem 2D tehničke dokumentacije, stvoreni su svi preduvjeti za izradu prototipa i funkcionalnu provjeru u stvarnim uvjetima primjene., 3D model construction of a product (honey extractor), including the sequence of complex parts and mounting assemblies’ construction, is shown. By implementing transparent materials and the extractor’s drive some possible improvements are proposed. By constructing 3D models and generating 2D technical documentation, all the preconditions necessary for prototyping and functional testing under real conditions of the application were created.

Waste is one of the key issues of the modern civilisation and represents the result of our way of life. After the occurrence of bovine spongiform encephalopathy and the ban to feed animals with bone meals, new technologies of animal waste processing are developed, as well as animal waste uses for energy purposes. Certain parts of this waste, such as brains and spinal cord, are deemed high-risk substances and can be infected with prions; their treatment is therefore only possible in strictly controlled conditions. Tests against effects of hydrolysis were conducted on samples of first class animal waste, bovine brains, in circumstances of different temperatures and hydrolisation duration, using the designed and built experimental laboratory reactor for alkaline hydrolysis. Production of hydrolysed substance biogas is monitored using the existing laboratory biogas circuit. Large potentials of hydrolyzates utilisation for energy purposes is featured by the analysis and systematisation of quantified results of the research, and the method used can be successfully applied for the pre-treatment of high-risk biological substances in biogas production., Otpad je jedan od ključnih problema moderne civilizacije i predstavlja rezultat našeg načina života. Nakon pojave goveđe spongiformne encefalopatije, te zabrane hranjenja životinja mesnim koštanim brašnom razvijaju se nove tehnologije prerade životinjskog otpada i njegova upotreba u energetske svrhe. Neki dijelovi ovog otpada, kao mozak i leđna moždina, visoko su rizične tvari i mogu biti zaraženi prionima, te je njihovo zbrinjavanje moguće isključivo u strogo kontroliranim uvjetima. Pomoću osmišljenog i izgrađenog eksperimentalnog laboratorijskog reaktora za alkalnu hidrolizu provedena su ispitivanja učinaka hidrolize pri različitoj temperaturi i trajanju hidroliziranja na uzorcima prve kategorije otpada životinjskog podrijetla, mozgu goveda. Korištenjem postojećeg laboratorijskog bioplinskog sklopa praćena je proizvodnja bioplina hidroliziranog materijala. Analizom i sistematizacijom kvantificiranih rezultata istraživanja istaknut je velik potencijal energetske upotrebe hidrolizata te se korištena metoda može uspješno primijeniti za predtretman visoko rizičnih bioloških materijala pri proizvodnji bioplina.

U radu se raspravlja o povijesnom tehničko-tehnološkom napretku i utjecaju na prioritete čovjeka u funkciji njegova opstanka, održivog razvoja i obrazovanja. Istaknut je velik doprinos znanstveno-tehnološkog i informacijskog napretka razvoju globalizacije, ali i snaženju prijepornih društveno-ekonomskih vrijednosti i odnosa. Provedenim istraživanjima i kvantificiranim vrijednostima prikazano je stanje i operativne mogućnosti tehnike i tehnologije, korištenje informatike i komunikacija u proizvodnim tvrtkama Bjelovarsko-bilogorske županije. Analiziran je udio pojedinih grana djelatnosti u gospodarstvu Županije u zadnjih 18 godina. Dijagramski je prikazana suradnja domaćih i inozemnih stručnjaka i znanstvenika s nekim proizvodnim tvrtkama u proteklom razdoblju. Na karakterističnom primjeru procijenjen je učinak povjerenja u stručnjake na domaćem i inozemnom tržištu. Istaknuta je važnost osnivanja i razvoja visokih učilišta u BBŽ-u, stalnog rasta broja studenata, stručnog i znanstvenog potencijala neophodnih za jačanje proizvodnih djelatnosti. Predložene su smjernice djelovanja znanosti, tehnike i tehnologije s gospodarstvom BBŽ-a., The paper discusses the historical technical and technological progress and its impact on the priorities developed in the context of serving its survival, sustainable development and education of the mankind. The major contributions of the scientific, technological and information progress both to the development of the globalisation and to the strengthening of the social and economic values and relations of debatable nature are pointed out. The research results and quantification data show the current status and the operational possibilities of technique and technology, as well as the use of information science and communications in the County’s production sector. Individual sectors are analysed as regards their share in the County’s economy in the last 18 years. The cooperation of domestic and international scientists and experts that has recently been realised with some of the firms in the production sector is presented in the form of a diagram. Based on a characteristic example, the assessment of the level of trust in experts in both the domestic and the international markets is given. It is emphasised how important it is for the Bjelovar-Bilogora County to be able to offer university education, to have a constant increase in the number of students, and to dispose of the professional and scientific potential needed for the strengthening of the production sector. Finally, the manner in which science, technique and technology should work together with the economy of the Bjelovar-Bilogora County is suggested.

This paper deals with the results of investigating implementation of six sigma methodology in small production organizations in the Republic of Croatia and with experiences from some European countries (Great Britain and Finland). At the end the authors performed the DELPHI method to predict the time of wider application of this methodology in small Croatian organizations., Članak obrađuje rezultate istraživanja u primjeni metodologije 6σ u malim proizvodnim organizacijama u RH i iskustva u primjeni 6σ-programa u malim organizacijama nekih zemalja u Europi (Velike Britanije i Finske). Na kraju autori su proveli "Delphi" metodu s ciljem prognoziranja vremena početka masovnije primjene navedene metodologije u malim hrvatskim poduzećima.