1. A holistic approach to cooling system selection and injection molding process optimization based on non-dominated sortingJanez Gotlih, Miran Brezočnik, Snehashis Pal, Igor Drstvenšek, Timi Karner, Tomaž Brajlih, 2022, original scientific article Abstract: This study applied a holistic approach to the problem of controlling the temperature of critical areas of tools using conformal cooling. The entire injection molding process is evaluated at the tool design stage using four criteria, one from each stage of the process cycle, to produce a tool with effective cooling that enables short cycle times and ensures good product quality. Tool manufacturing time and cost, as well as tool life, are considered in the optimization by introducing a novel tool-efficiency index. The multi-objective optimization is based on numerical simulations. The simulation results show that conformal cooling effectively cools the critical area of the tool and provides the shortest cycle times and the lowest warpage, but this comes with a trade-off in the tool-efficiency index. By using the tool-efficiency index with non-dominated sorting, the number of relevant simulation cases could be reduced to six, which greatly simplifies the decision regarding the choice of cooling system and process parameters. Based on the study, a tool with conformal cooling channels was made, and a coolant inlet temperature of 20 °C and a flow rate of 5 L/min for conformal and 7.5–9.5 L/min for conventional cooling channels were selected for production. The simulation results were validated by experimental measurements.
Keywords: conformal cooling, injection molding, tooling, additive manufacturing, numerical simulation, non-dominated sorting
Published in DKUM: 05.12.2024; Views: 0; Downloads: 5
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2. Optimization of billet cooling after continuous casting using genetic programming—industrial studyMiha Kovačič, Aljaž Zupanc, Robert Vertnik, Uroš Župerl, 2024, original scientific article Abstract: ŠTORE STEEL Ltd. is one of the three steel plants in Slovenia. Continuous cast 180 mm × 180 mm billets can undergo cooling to room temperature using a turnover cooling bed. They can also be cooled down under hoods or heat treated to reduce residual stresses. Additional operations of heat treatment from 36 h up to 72 h and cooling of the billets for 24 h, with limited capacities (with only two heat treatment furnaces and only six hoods), drastically influence productivity. Accordingly, the casting must be carefully planned (i.e., the main thing is casting in sequences), while the internal quality of the billets (i.e., the occurrence of inner defects) may be compromised. Also, the stock of billets can increase dramatically. As a result, it was necessary to consider the abandoning of cooling under hoods and heat treatment of billets. Based on the collected scrap data after ultrasonic examination of rolled bars, linear regression and genetic programming were used for prediction of the occurrence of inner defects. Based on modeling results, cooling under hoods and heat treatment of billets were abandoned at the casting of several steel grades. Accordingly, the casting sequences increased, and the stock of billets decreased drastically while the internal quality of the rolled bars remained the same.
Keywords: billet cooling, continuous casting, ultrasonic testing, logistic regression, genetic programming, industrial study, steel making, optimization
Published in DKUM: 25.11.2024; Views: 0; Downloads: 8
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3. 6th International Conference En-Re Energy & Responsibility : Book of Extended Abstracts2024 Abstract: In the context of escalating climate challenges, the EnRe conference is dedicated to exploring pathways to climate neutrality and the sustainable green transition. The conference is focused on the development and implementation of innovations supporting the transformation of energy systems, industrial systems, and living systems, all with the goal of creating a sustainable future with net-zero emissions. The conference brings together experts, researchers, policymakers, and business leaders to share their experiences, research, and visions. The aim of the conference is to foster collaboration and exchange of ideas, and to collectively develop comprehensive approaches and strategies for achieving climate neutrality. This conference is not just a knowledge exchange, but also a platform for encouraging concrete actions that will ensure a greenerand more sustainable future for our next generations to come.
Keywords: alternative energy systems, dynamic tariffing, electrical machines and drives, energy conversions, financing energy projects, nuclear energy, conventional energy systems, climate changes - climate pan, mathematical methods in engineering, micro and nano energy, low-carbon technologies and strategies, renewable energy technologies heating and cooling systems, smart buildings, cities and networks, policies and strategies for renewable energy sources, energy efficiency and the climate
Published in DKUM: 17.05.2024; Views: 332; Downloads: 48
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4. Production, thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildingsJurij Avsec, Daniel Brandl, Helmut Schober, Urška Novosel, Janko Ferčec, 2019, published scientific conference contribution Abstract: The effects of global warming are a crucial issue in the near future. The combination of renewable energy sources (RES) and the use of alternative energy technology such as heat pumps and hydrogen technology could solve major ecological problems. In Central Europe, the energy demand for heating and cooling in residential buildings is clearly higher than for generation of electricity or energy for trucking e.g. In this paper, a new solar thermal absorber has been analysed which is produced by using the so called "roll bond" technology (ABS Network, 2018). The focus of this study lies on the determination of the energy efficiency by combining this solar thermal absorber with heat pumps and biomass or geothermal systems in the region of Central Europe.
Keywords: roll bond solar absorbers, thermal analysis, solar
systems, heat pump systems, heating and cooling in residential
buildings
Published in DKUM: 04.12.2023; Views: 332; Downloads: 32
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5. Fractal geometry as an effective heat sinkMatjaž Ramšak, 2022, original scientific article Abstract: "How long is the coast of Britain?" was the question stated by Mandelbrot. Using smaller and smaller rulers the coast length limits to infinity. If this logic is applied to the fractal heat sink geometry, infinite cooling capacity should be obtained using fractals with mathematically infinite surface area. The aim of this article is to check this idea using Richardson extrapolation of numerical simulation results varying the fractal element length from one to zero. As expected, the extrapolated heat flux has a noninfinite limit. The presented fractal heat sink geometry is non-competitive to the straight fins.
Keywords: fractal heat sink, LED cooling, CPU cooling, conjugate heat transfer, laminar flow, boundary element method, Koch snowflake
Published in DKUM: 14.07.2023; Views: 653; Downloads: 17
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6. Empirical modeling of liquefied nitrogen cooling impact during machining Inconel 718Matija Hriberšek, Lucijano Berus, Franci Pušavec, Simon Klančnik, 2020, original scientific article Abstract: This paper explains liquefied nitrogen’s cooling ability on a nickel super alloy called Inconel 718. A set of experiments was performed where the Inconel 718 plate was cooled by a moving liquefied nitrogen nozzle with changing the input parameters. Based on the experimental data, the empirical model was designed by an adaptive neuro-fuzzy inference system (ANFIS) and optimized with the particle swarm optimization algorithm (PSO), with the aim to predict the cooling rate (temperature) of the used media. The research has shown that the velocity of the nozzle has a significant impact on its cooling ability, among other factors such as depth and distance. Conducted experimental results were used as a learning set for the ANFIS model’s construction and validated via k-fold cross-validation. Optimization of the ANFIS’s external input parameters was also performed with the particle swarm optimization algorithm. The best results achieved by the optimized ANFIS structure had test root mean squared error (test RMSE) = 0.2620, and test R$^2$ = 0.8585, proving the high modeling ability of the proposed method. The completed research contributes to knowledge of the field of defining liquefied nitrogen’s cooling ability, which has an impact on the surface characteristics of the machined parts.
Keywords: cryogenic machining, cooling impact, Inconel 718, machine learning, adaptive neuro-fuzzy inference system, particle swarm optimization
Published in DKUM: 14.07.2023; Views: 564; Downloads: 40
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7. Simulation of automotive air-conditioning system in 1D simulation software : diplomsko deloMarko Copot, 2019, undergraduate thesis Abstract: The development of state-of-the-art vehicles requires advanced simulations tools in heating, ventilation and air-conditioning (HVAC). The focus of this thesis is the construction of an automotive HVAC model, its calibration and the simulation of the behaviour of the HVAC model in various ambient conditions. The theoretical background of refrigeration system as part of the HVAC system is presented. The model is constructed with following components: compressor, condenser, throttling device, evaporator and battery chiller, which is a heat exchanger between coolant and refrigerant. The description and role of each component in the HVAC model is presented. All heat exchangers are calibrated, which is done with multiple simulations that have defined input data. The results are compared to experimental data. With addition of vehicle cabin with air recirculation, HVAC control logic is implemented. The behaviour of the system is simulated in defined environmental conditions. The results of the simulations are presented in graphs and tables.
Keywords: 1D simulations, air-conditioning, HVAC, calibration, thermodynamics, cooling
Published in DKUM: 23.09.2019; Views: 1453; Downloads: 112
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8. Ground-sourced energy wells for heating and cooling of buildingsHeinz Brandl, Dietmar Adam, Roman Markiewicz, 2006, original scientific article Abstract: Energy wells are thermo-active elements for an economical extraction or storage of ground energy, similar to energy piles and other deep foundation elements also used as heat exchangers. Heating and/or cooling of buildings requires a primary and secondary thermo-active circuit, commonly connected by a heat pump. The paper gives several design aspects of energy wells which can be also used for the design of deep energy foundations. Thermal response tests have proved suitable for the in-situ determination of thermal ground properties required for an optimised design. Moreover, different systems of energy wells are discussed, and a comprehensive pilot research project is described.
Keywords: energy wells, energy foundations, geothermal geotechnics, geothermal heating/cooling, thermo-active structures, thermal ground properties, field testing
Published in DKUM: 17.05.2018; Views: 1086; Downloads: 129
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9. Cooling analysis of a light emitting diode automotive fog lampMatej Zadravec, Matjaž Ramšak, Jure Ravnik, Matjaž Hriberšek, Jernej Slanovec, 2017, original scientific article Abstract: Efficiency of cooling fins inside of a light emitting diode fog lamp is studied using computational fluid dynamics. Diffusion in heat sink, natural convection and radiation are the main principles of the simulated heat transfer. The Navier-Stokes equations were solved by the computational fluid dynamics code, including Monte Carlo radiation model and no additional turbulence model was needed. The numerical simulation is tested using the existing lamp geometry and temperature measurements. The agreement is excellent inside of few degrees at all measured points. The main objective of the article is to determine the cooling effect of various heat sink parts. Based on performed simulations, some heat sink parts are found to be very ineffective. The geometry and heat sink modifications are proposed. While radiation influence is significant, compressible effects are found to be minor.
Keywords: heat transfer, cooling of electronic devices, cooling fins, light emitting diode automotive lamp, compressible flow
Published in DKUM: 07.07.2017; Views: 1564; Downloads: 401
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