Sustav dinamicko racunalno modeliranje jedan je od najprikladnijih i najucinkovitijih nacina dinamickog modeliranja složenih nelinearnih prirodnih, tehnickih i organizacijskih realiteta. Proucavanje dinamike ponasanja dizelskog motora,... more
Sustav dinamicko racunalno modeliranje jedan je od najprikladnijih i najucinkovitijih nacina dinamickog modeliranja složenih nelinearnih prirodnih, tehnickih i organizacijskih realiteta. Proucavanje dinamike ponasanja dizelskog motora, kao jednog od složenih dinamickih nelinearnih sustava, zahtjeva primjenu samo najucinkovitijih metoda modeliranja. Na primjeru jednog od podsustava dizelskog motora, njegovog rashladnog sustava, u radu je prikazana racunalna kontinuirana simulacija uz pomoc sustavne dinamike. U uvodnom dijelu opisan je rashladni sustav motora kao objekt regulacije i postavljen njegov matematicki model. Prema matematickom modelu izrađen je dinamicki kontinuirani racunalni simulacijski model rashladnog sustava dizelskog motora i automatskog regulatora u DYNAMO visem programskom jeziku, kojim se simulira dinamika ponasanja rashladnog sustava, tj. funkcionalna i vremenska ovisnost varijabli koje egzistiraju unutar promatranog sustava. Dobiveni rezultati simulacije prikaza...
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Different consequences of energy efficiency measures implementation, in low voltage installations, have been presented and analyzed. Especially, impact of energy inefficient light sources replacement by efficient lamps, and addition of... more
Different consequences of energy efficiency measures implementation, in low voltage installations, have been presented and analyzed. Especially, impact of energy inefficient light sources replacement by efficient lamps, and addition of variables speed drives to existing induction machines have been examined. The mentioned impacts have been analyzed on a small low voltage radial distribution network by harmonic power flow calculations. Nonlinear loads were modeled upon laboratory measurements of different compact fluorescent lamps and variable speed drives and harmonic analysis of respective current-voltage waveforms. In addition, impact of variable speed control on refrigeration machines and pumps has been examined and the results presented.U radu su obrađene neke od posljedica inherentnih sustavnom provođenju mjera za povećanje energetske učinkovitosti u niskonaponskim instalacijama zgrada. Posebno je analiziran utjecaj zamjene energetski neučinkovitih izvora svjetlosti učinkovitim...
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Analyses performed during the design of a fruit storage refrigeration system are presented. Simulation model describing all year round behavior of the cold storage and the refrigeration system has been established and simulations have... more
Analyses performed during the design of a fruit storage refrigeration system are presented. Simulation model describing all year round behavior of the cold storage and the refrigeration system has been established and simulations have been performed in order to evaluate optimal insulation thickness of the cold room and energy costs. Costs for energy, equipment and insulation, as well as costs caused by weight loss of the product have been introduced into a cost evaluation model and the complex which consists of storage and refrigeration system has been optimized. Comparison of energy consumption and investment costs between direct expansion and brine refrigeration system has been performed. Direct refrigeration system with higher COP and thus lower energy consumption has been found as the feasible choice. Analyses have also been aimed to the air-cooler design. Oversized evaporators have been chosen in order to maintain high air humidity within the storage and thus decrease the weigh...
Analyses performed during the design of a fruit storage refrigeration system are presented. Simulation model describing all year round behavior of the cold storage and the refrigeration system has been established and simulations have... more
Analyses performed during the design of a fruit storage refrigeration system are presented. Simulation model describing all year round behavior of the cold storage and the refrigeration system has been established and simulations have been performed in order to evaluate optimal insulation thickness of the cold room and energy costs. Costs for energy, equipment and insulation, as well as costs caused by weight loss of the product have been introduced into a cost evaluation model and the complex which consists of storage and refrigeration system has been optimized. Comparison of energy consumption and investment costs between direct expansion and brine refrigeration system has been performed. Direct refrigeration system with higher COP and thus lower energy consumption has been found as the feasible choice. Analyses have also been aimed to the air - cooler design. Oversized evaporators have been chosen in order to maintain high air humidity within the storage and thus decrease the wei...
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U radu se analizira utjecaj pojedinih svojstava teskog goriva, kao sto su gustoca, viskoznost, zapaljivost, sadržaj vode, pepela, sumpora i drugo, na ostecenja i kvarove brodskih dizelskih motora. Razmatraju se pojedini mjerni parametri... more
U radu se analizira utjecaj pojedinih svojstava teskog goriva, kao sto su gustoca, viskoznost, zapaljivost, sadržaj vode, pepela, sumpora i drugo, na ostecenja i kvarove brodskih dizelskih motora. Razmatraju se pojedini mjerni parametri pomocu kojih se dijagnosticira stanje kvarova ili razvoj ostecenja, te iznose postupci za smanjenje mogucnosti nastanka ostecenja ili smetnji normalnog rada brodskih dizelskih motora.
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Rad je podsjetnik na dvjestotu godisnjicu prve uspjesne uporabe parnog stroja za pogon broda. Prikazan je povijesni razvoj stapnoga parnog stroja, parne i plinske turbine i generatora pare te njihova uporaba na brodovima. Posebno su... more
Rad je podsjetnik na dvjestotu godisnjicu prve uspjesne uporabe parnog stroja za pogon broda. Prikazan je povijesni razvoj stapnoga parnog stroja, parne i plinske turbine i generatora pare te njihova uporaba na brodovima. Posebno su istaknuti povijesni brodovi "Clermont" (1807.), "Turbinia" (1894.) i "Nautilus" (1954.), koji su imali pionirsku ulogu u koristenju novim vrstama propulzije: stapnim parnim strojem, parnim turbinama i nuklearnim reaktorom. Opisan je i svojedobno najveci brod na svijetu "Titanic" ; on ima važno mjesto u povijesti razvitka brodske parne propulzije. U radu je dan osvrt na povijesni razvoj brodskih generatora pare.
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Naobrazba i izobrazba pomoraca na Veleucilistu u Dubrovniku, organizirana sukladno svjetskim standardima, jamstvo je da ce nasi studenti, odnosno pomorci, kao i uvijek, zahvaljujuci svojim sposobnostima i pokazanom znanju, biti izuzetno... more
Naobrazba i izobrazba pomoraca na Veleucilistu u Dubrovniku, organizirana sukladno svjetskim standardima, jamstvo je da ce nasi studenti, odnosno pomorci, kao i uvijek, zahvaljujuci svojim sposobnostima i pokazanom znanju, biti izuzetno cijenjeni i traženi na brodovima svih zastava svijeta. Kvalitete hrvatskih pomoraca u posljednje vrijeme jos i vise dolaze do izražaja, buduci da je ljudski cimbenik najvažnija karika u lancu koji pridonosi sigurnosti plovidbe i sprecavanju oneciscenosti mora. Osim toga, primjena najnovijih spoznaja u zastiti ljudskih života, materijalnih dobara i morskog okolisa izuzetno je važna za Republiku Hrvatsku kao pomorsku zemlju s preko 30 000 pomoraca.
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This paper develops mathematical model for the flat plate which is including temperature dynamics of the top surface on the plate TPi(t) and dynamics of the heat load through the plate Q(t), both depending on the air temperature changes... more
This paper develops mathematical model for the flat plate which is including temperature dynamics of the top surface on the plate TPi(t) and dynamics of the heat load through the plate Q(t), both depending on the air temperature changes Tao(t) on one side and Tai(t) on the other side of the plate. The method of system dynamics, known as Forrester's dynamics, was used for development of dynamic model. Model is based on concentrated parameters and therefore simple differential equations are used for description of the plate temperature dynamics. Powersim program is used for simulation. Evaluation of dynamic model is performed for the plate edges with different values of the Biot number. Comparison of the simulation results and analytical computation is presented in a form of a table. It is confirmed that simulation model follows trend of the temperature dynamic on the top surface of the plate. Presented model is adequate both for thermally-thick and thermally-thin plates.
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U prvom dijelu rada opisane su vrste otpadnih voda i posebno brodskih otpadnih voda. Definirani su pokazatelji svojstava kucanskih, odnosno sanitarnih otpadnih voda, kojoj vrsti pripadaju i fekalne otpadne vode. Također su nabrojeni... more
U prvom dijelu rada opisane su vrste otpadnih voda i posebno brodskih otpadnih voda. Definirani su pokazatelji svojstava kucanskih, odnosno sanitarnih otpadnih voda, kojoj vrsti pripadaju i fekalne otpadne vode. Također su nabrojeni postupci i operacije koje se koriste u obradi otpadnih voda. Uz opis nacina rada opcenitog brodskog uređaja za obradu fekalnih voda, prikazan je uređaj Hamworthy Super Trident ST4A, kakav je ugrađen npr. na m/b "Petka" dubrovacke "Atlantske plovidbe". Postupak ozracivanja, koji se provodi radi stvaranja aerobnih uvjeta, te postupak bistrenja, kao karakteristicni procesi inženjerstva disperznih sustava, detaljno su opisani i teorijski objasnjeni. Prikazani su postupci dimenzioniranja osnovnih elemenata brodskog uređaja za obradu fekalnih voda, uz kriticki osvrt na prakticnu inženjersku primjenljivost pojedinih izraza za dimenzioniranje. U zavrsnom dijelu rada izneseno je stanje na planu ekoloskih propisa i osnovni podaci propisanih eko...
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In many branches of industry parts made out of composite materials are used. Their usage depends on possibilities for production of parts with specified quality. In order to achieve demanded quality during cutting process of composite... more
In many branches of industry parts made out of composite materials are used. Their usage depends on possibilities for production of parts with specified quality. In order to achieve demanded quality during cutting process of composite materials based on carbon and aramid fibres, cutting tools must satisfy special requirements of tool material and cutting part geometry. In this paper summary of cutting tools and recommended machining regimes, based on theoretical and laboratory data, are given. Additionally, several possible ways of quality improvement in machining of composite materials are given.
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Sustav dinamicko racunalno modeliranje jedan je od najprikladnijih i najucinkovitijih nacina dinamickog modeliranja složenih nelinearnih prirodnih, tehnickih i organizacijskih realiteta. Proucavanje dinamike ponasanja dizelskog motora,... more
Sustav dinamicko racunalno modeliranje jedan je od najprikladnijih i najucinkovitijih nacina dinamickog modeliranja složenih nelinearnih prirodnih, tehnickih i organizacijskih realiteta. Proucavanje dinamike ponasanja dizelskog motora, kao jednog od složenih dinamickih nelinearnih sustava, zahtjeva primjenu samo najucinkovitijih metoda modeliranja. Na primjeru jednog od podsustava brodskog dizelskog motora, njegovog rashladnog sustava, u radu je prikazana racunalna kontinuirana simulacija uz pomoc sustavne dinamike. U uvodnom dijelu opisan je rashladni sustav motora kao objekt regulacije i postavljen njegov matematicki model. Prema matematickom modelu izrađen je dinamicki kontinuirani racunalni simulacijski model u DYNAMO visem programskom jeziku, kojim se simulira dinamika ponasanja rashladnog sustava, tj. funkcionalna i vremenska ovisnost varijabli koje egzistiraju unutar promatranog sustava. Dobiveni rezultati simulacije prikazani su numericki i graficki. U radu su iznesene osnov...
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During grinding, heat from machined object, chip and grinder is transffered into the cooling and lubricating medium. Grinder's wear and pore clogging reduces their grinding stability and reduces quality of machining. Chips and... more
During grinding, heat from machined object, chip and grinder is transffered into the cooling and lubricating medium. Grinder's wear and pore clogging reduces their grinding stability and reduces quality of machining. Chips and mechanical particles within coolin and lubricating medium cause clogging of grinder's pores. By reducing the quantity of mechanical particles grinder's cutting ability and productivity is increased. In this paper, results of quality of cooling and lubricating medium for machining of spiral grooves in high speed steel drills are given.
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Knowledge of the psychrometric properties of moist air is essential in the design of air conditioning, cold storage, and drying processes. The presented paper describes the development of mathematical model suitable for calculating... more
Knowledge of the psychrometric properties of moist air is essential in the design of air conditioning, cold storage, and drying processes. The presented paper describes the development of mathematical model suitable for calculating psychometric properties and for simulation of dynamic behaviour of moist air in refrigerated room. Moist air, circulating around refrigerated product within cold chamber, is continuously in direct contact with surface of the goods, chamber walls, chamber outfit, fans, defrosting coils and evaporator surface. Simultaneous heat and mass exchange occurs between moist air and all elements that air flows by. During the flow within the cold chamber, moist air is simultaneously exposed to all typical changes of state, such as cooling, heating, dehumidification, moistening and mixing with outside air stream caused by door opening and air leakage. Developed mathematical model, describing the dynamics of air temperature and humidity change caused by those multiple ...
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U ovom radu razvijen je i opisan dinamicki model sustava brodskog rashladnog kontejnera kojiomogucuje simulaciju njegova dinamickog ponasanja. Za modeliranje i simulaciju koristilo se metodomsistemske dinamike. Ispitivanje je provedeno na... more
U ovom radu razvijen je i opisan dinamicki model sustava brodskog rashladnog kontejnera kojiomogucuje simulaciju njegova dinamickog ponasanja. Za modeliranje i simulaciju koristilo se metodomsistemske dinamike. Ispitivanje je provedeno na 12,2-metarskom (40-stopnom) rashladnom kontejneruoznake 1 AAA opremljenom integralnim rashladnim uređajem Thermo King, model CRR40 PS. Sobzirom na to da je sustav brodskog rashladnog kontejnera složeni dinamicki sustav, promatran je ianaliziran s pomocu jednostavnijih podsustava koji su kreirani tako da cine njegove komponente.Razvijeni su posebni matematicki modeli pojedinih podsustava: kontejnerske stijenke, hlađenogvlažnog zraka u kontejneru, hlađenog predmeta, kondenzacijske jedinice, isparivaca, kontejnerskeopreme, ventilatora isparivaca i grijaca odmrzivaca. Matematicki modeli, koji su s usredotocenimparametrima, zasnovani su na masenim i energijskim bilancama. Njima su opisane uzrocno--posljedicne veze između ulaznih, izlaznih i internih var...
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Heat and cooling stands out with the great potential in decarbonisation since they have a large share in the final energy consumption. Power-to-heat technologies may contribute to the heat sector decarbonisation as well as the integration... more
Heat and cooling stands out with the great potential in decarbonisation since they have a large share in the final energy consumption. Power-to-heat technologies may contribute to the heat sector decarbonisation as well as the integration of renewables if they are sufficiently flexible. They are also shown to have a good effect on the system costs. This work will analyse the potential of seawater heat pump system for the utilization of high share of electricity production from the renewables. The Old City of Dubrovnik is selected as a case study because of its specific situation. A large number of the outdoor units are not well approved by UNESCO since the Old City is under the protection of the UNESCO World Heritage Centre. The results of the study showed that the combination of wind and solar electricity production can cover 67% of load for stand-alone seawater heat pump system based on hourly time step. Utilization of renewable electricity generation, for this case, resulted in 4...
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The quality of maritime education system could be considered as one of the most important pillar for safe and efficient shipping. Particularly vital is the maritime education at the university level and those ensuring seafarers’ top rank... more
The quality of maritime education system could be considered as one of the most important pillar for safe and efficient shipping. Particularly vital is the maritime education at the university level and those ensuring seafarers’ top rank qualifications in accordance with the STCW Convention. Generally, the quality of education of the individuals is correlated to the employability and promotion opportunities. In Croatia, maritime education system is well established with a long tradition of education at the university level enabling acquisition of top rank seafarers’ qualifications. This paper presents a survey of the results related to the seafarers’ satisfaction with the quality of maritime education and curricula provided during their education at the maritime higher education institution in Dubrovnik. The research was carried out by interviewing 154 marine engineers with different sea service experience, educational level and rank aiming to obtain their opinions about importance,...
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One of the most suitable and effective way of dynamics modelling of the complex nonlinear natural, technical and organization systems is The System Dynamics Computer Simulation Modelling Methodology. The System Dynamics school of... more
One of the most suitable and effective way of dynamics modelling of the complex nonlinear natural, technical and organization systems is The System Dynamics Computer Simulation Modelling Methodology. The System Dynamics school of modelling does have its own set of strict rules for what constitutes proper professional procedure or methodology. Following a number of computer-laboratory researches, the system dynamics simulation models were manufactured out from 1991 to 2007, as under-graduate theses at the Maritime Faculty University of Split and the Polytechnic of Dubrovnik (former Maritime Faculty in Dubrovnik). The aims of this paper are: 1. to show the efficiency of this modelling approach, 2. to give marine students the better "point of view" or tool for the non-linear dynamics models simulation, as it would improve marine education processes, and 3. to show one example for supporting new education quality, exactly as it is in case of THE MARINE STEAM TURBINE-DRIVE GENE...
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ABSTRACT A model describing the behaviour of an industrial scale shell-and-tube condenser is presented. The model can be used under steady-state as well as under transient conditions and is able to predict vapour and condensate flow... more
ABSTRACT A model describing the behaviour of an industrial scale shell-and-tube condenser is presented. The model can be used under steady-state as well as under transient conditions and is able to predict vapour and condensate flow rates, pressure drop and the temperatures of the vapour, condensate, wall and coolant. The derivation of the material and energy balances is presented. Thus the apparatus is subdivided into increments corresponding to the location of the baffles in the condenser. Each of these baffle spaces is assumed to be fully mixed. The heat and material fluxes between the phases are determined using local transfer coefficients which are calculated for each baffle space. The model also includes the determination of the pressure profile along the apparatus. The results of several simulations are compared with experimental data to achieve a validation of the model. Both the steady-state and the transient behaviour of the condenser were examined, the latter when the system was subjected to step changes in each of the five key loads that determine the condenser behaviour. These are the pressure, steam flow rate, air flow rate, coolant flow rate and coolant inlet temperature. The results of the simulations agreed well with the experimental data.
Research Interests: Engineering, Materials Science, Mechanics, Thermodynamics, Heat Transfer, and 14 moreHeat and Mass Transfer, Air flow, Modelling and simulation, Mathematical Sciences, Dynamic Simulation, Physical sciences, Energy Balance, Steady state, Pressure Drop, Shell Structure, Dynamic behaviour of materials, Flow Rate, Experimental Data, and Dynamic Behaviour
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