Pub Date : 1900-01-01DOI: 10.5545/SV-JME.2021.7262
T. Bucki, M. Konieczny, D. Bolibruchová, S. Rzepa
The work deals with the fabrication of a joint between AZ31 magnesium alloy and AW-6060 aluminium alloy with the use of a Zn interlayer. The Zn layer was produced on the surface of an AW-6060 alloy insert by diffusion bonding. The insert was then placed inside a steel mould and kept at room temperature. The joint was produced using compound casting by filling the mould with liquid AZ31 alloy, heated to 650 °C. The microstructure of the bonding zone formed between joined alloys was analysed using an optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray spectroscope. The properties of the joint were examined using Vickers microhardness measurements and simple shear strength testing. As a result of the experiment, the 400 [micro]m thick bonding zone with a complex microstructure was formed between the alloys. The microstructural analysis showed that the bonding zone reveals a high concentration of Zn and Mg. The layers of a eutectoid (a MgZn phase + a solid solution of Al and Zn in Mg), a Mg5Al2Zn2 phase and a Mg(Al,Zn)2 phase with fine particles of other phases were observed there. The bonding zone was characterized by relatively high microhardness, which was related to the brittleness of the constituents. The shear strength of the examined joint was 19.6 +/- 2.5 MPa.
{"title":"Characterization of the AZ31/AW-6060 joint fabricated using compound casting with a Zn interlayer at relatively low temperature conditions","authors":"T. Bucki, M. Konieczny, D. Bolibruchová, S. Rzepa","doi":"10.5545/SV-JME.2021.7262","DOIUrl":"https://doi.org/10.5545/SV-JME.2021.7262","url":null,"abstract":"The work deals with the fabrication of a joint between AZ31 magnesium alloy and AW-6060 aluminium alloy with the use of a Zn interlayer. The Zn layer was produced on the surface of an AW-6060 alloy insert by diffusion bonding. The insert was then placed inside a steel mould and kept at room temperature. The joint was produced using compound casting by filling the mould with liquid AZ31 alloy, heated to 650 °C. The microstructure of the bonding zone formed between joined alloys was analysed using an optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray spectroscope. The properties of the joint were examined using Vickers microhardness measurements and simple shear strength testing. As a result of the experiment, the 400 [micro]m thick bonding zone with a complex microstructure was formed between the alloys. The microstructural analysis showed that the bonding zone reveals a high concentration of Zn and Mg. The layers of a eutectoid (a MgZn phase + a solid solution of Al and Zn in Mg), a Mg5Al2Zn2 phase and a Mg(Al,Zn)2 phase with fine particles of other phases were observed there. The bonding zone was characterized by relatively high microhardness, which was related to the brittleness of the constituents. The shear strength of the examined joint was 19.6 +/- 2.5 MPa.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124114404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5545/SV-JME.2017.5103
Z. Keran, Živko Kondić, P. Piljek, B. Runje
In micro-forming processes, such as coining, the microstructure of the material and dimension scale of the coined geometry can have a substantial influence on the mechanism of material deformation. The influence of the grain size on the coining force and closed die filling is investigated experimentally, and a mathematical model for result prediction has been created according to the obtained experimental results. The material of the billet is 99.5 % aluminium, and the die geometry is relatively complex. The presented mathematical model takes into account the influence of size effect on the material flow curve through die cavity geometry and estimates the final coining force and corresponding associated displacement of the tool. This enables a controlled influence of the grain size of the specimen material on forming force and tool displacement in the coining process and a reliable prediction of the final coining force and related tool displacement associated with a completely filled die cavity. To determine the accuracy of model force prediction, the experimental and modelled data were statistically analysed and graphically presented.
{"title":"Accuracy of Model Force Prediction in Closed Die Coining Process","authors":"Z. Keran, Živko Kondić, P. Piljek, B. Runje","doi":"10.5545/SV-JME.2017.5103","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.5103","url":null,"abstract":"In micro-forming processes, such as coining, the microstructure of the material and dimension scale of the coined geometry can have a substantial influence on the mechanism of material deformation. The influence of the grain size on the coining force and closed die filling is investigated experimentally, and a mathematical model for result prediction has been created according to the obtained experimental results. The material of the billet is 99.5 % aluminium, and the die geometry is relatively complex. The presented mathematical model takes into account the influence of size effect on the material flow curve through die cavity geometry and estimates the final coining force and corresponding associated displacement of the tool. This enables a controlled influence of the grain size of the specimen material on forming force and tool displacement in the coining process and a reliable prediction of the final coining force and related tool displacement associated with a completely filled die cavity. To determine the accuracy of model force prediction, the experimental and modelled data were statistically analysed and graphically presented.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114338605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2004.INTTHERMSCISEMIN.1080
M. Aydin, G. Balık, A. Miguel, A. H. Reis, R. R. Ramalho
There has been a growing interest in the study of porous and complex flow structures due to its impact in technology. This concerns not only environmental but also diagnostic and therapeutic exposure in medical research. Physics of flow within porous structures is especially important to model transport and deposition of viruses, pollutants and drugs deep in these structures. In this work we analyze numerically low and medium Reynolds number flows in axisymmetric cylindrical duct surrounded by a torus. We also consider three different particle sizes (0.02, 0.1 and 20Pm) for possible physiological and environmental applications.
{"title":"Some Features of Flow and Particle Transport in Porous Structures","authors":"M. Aydin, G. Balık, A. Miguel, A. H. Reis, R. R. Ramalho","doi":"10.1615/ICHMT.2004.INTTHERMSCISEMIN.1080","DOIUrl":"https://doi.org/10.1615/ICHMT.2004.INTTHERMSCISEMIN.1080","url":null,"abstract":"There has been a growing interest in the study of porous and complex flow structures due to its impact in technology. This concerns not only environmental but also diagnostic and therapeutic exposure in medical research. Physics of flow within porous structures is especially important to model transport and deposition of viruses, pollutants and drugs deep in these structures. In this work we analyze numerically low and medium Reynolds number flows in axisymmetric cylindrical duct surrounded by a torus. We also consider three different particle sizes (0.02, 0.1 and 20Pm) for possible physiological and environmental applications.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124704536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.5545/SV-JME.2017.5079
M. Calì, S. Oliveri, A. Rita, G. Fichera
In the aerospace and automotive industries 65 % to 70 % of failures and breakdowns of mechanical systems are caused by geometric and/or size variations whose consequences were not accurately predicted during the design phase [1]. Dimensional and geometrical variations can significantly influence the functionality of assembled mechanical systems, especially those consisting of highly deformable components subjected to shock and vibration [2] and [3]. These systems characterized by the presence of sliding contacts and yielding constraints are generally used in mechanics to dampen vibrations and store or dissipate energy. Their reliability is as important as the need to precisely predict and control the variability of their dynamic characteristics since their geometrical properties (e.g. shape and dimension) are subjected to change. Examples of such assemblies include civil, military, automotive, naval and aerospace applications [4] to [6]. According to the available numerical analysis methods (i.e. finite element method (FEM) and multibody), simulations of these systems appear to be particularly complex, since it is difficult to determine the presence of extended sliding contacts and moving impacts between flexible components, as well as a high degree of geometric non-linearity [7] and [8]. Usually constitutive equations or rate constitutive equations are used in finite element software to model these systems and characterization of such systems is carried out by means of experimental testing [9] and [10]. This study proposes a replicable semi -empirical procedure, based on few targeted experimental displacement measurements and modal analyses, where functional tolerance specifications are used to predict and control the variability of the dynamic behaviour in such systems. The actual tolerance specifying method is geometric dimensioning and tolerancing (GD&T) as indicated in the ASME Y14.5 [11] and ISO 1101 [12] standards. The application of GD&T can be ensured by different approaches, mainly attributable to tolerance analysis and tolerance synthesis. In tolerance analysis [13] and [14] the contribution to the accumulation of variations at one or more functional features in a tolerance stack-up is considered, while tolerance synthesis [15] to [17] studies the influence of geometrical variations in parts on the behaviour of a An Integrated Approach to Characterize the Dynamic Behaviour of a Mechanical Chain Tensioner by Functional Tolerancing Calì, M. – Oliveri, S.M. – Ambu, R. – Fichera, G. Michele Calì1,* – Salvatore Massimo Oliveri1 – Rita Ambu2 – Gabriele Fichera3 1University of Catania, Electric, Electronics and Computer Engineering Department, Italy 2University of Cagliari, Department of Mechanical, Chemical and Materials Engineering, Italy 3University of Catania, Civil Engineering and Architecture Department, Italy
{"title":"An Integrated Approach to Characterize the Dynamic Behaviour of a Mechanical Chain Tensioner by Functional Tolerancing","authors":"M. Calì, S. Oliveri, A. Rita, G. Fichera","doi":"10.5545/SV-JME.2017.5079","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.5079","url":null,"abstract":"In the aerospace and automotive industries 65 % to 70 % of failures and breakdowns of mechanical systems are caused by geometric and/or size variations whose consequences were not accurately predicted during the design phase [1]. Dimensional and geometrical variations can significantly influence the functionality of assembled mechanical systems, especially those consisting of highly deformable components subjected to shock and vibration [2] and [3]. These systems characterized by the presence of sliding contacts and yielding constraints are generally used in mechanics to dampen vibrations and store or dissipate energy. Their reliability is as important as the need to precisely predict and control the variability of their dynamic characteristics since their geometrical properties (e.g. shape and dimension) are subjected to change. Examples of such assemblies include civil, military, automotive, naval and aerospace applications [4] to [6]. According to the available numerical analysis methods (i.e. finite element method (FEM) and multibody), simulations of these systems appear to be particularly complex, since it is difficult to determine the presence of extended sliding contacts and moving impacts between flexible components, as well as a high degree of geometric non-linearity [7] and [8]. Usually constitutive equations or rate constitutive equations are used in finite element software to model these systems and characterization of such systems is carried out by means of experimental testing [9] and [10]. This study proposes a replicable semi -empirical procedure, based on few targeted experimental displacement measurements and modal analyses, where functional tolerance specifications are used to predict and control the variability of the dynamic behaviour in such systems. The actual tolerance specifying method is geometric dimensioning and tolerancing (GD&T) as indicated in the ASME Y14.5 [11] and ISO 1101 [12] standards. The application of GD&T can be ensured by different approaches, mainly attributable to tolerance analysis and tolerance synthesis. In tolerance analysis [13] and [14] the contribution to the accumulation of variations at one or more functional features in a tolerance stack-up is considered, while tolerance synthesis [15] to [17] studies the influence of geometrical variations in parts on the behaviour of a An Integrated Approach to Characterize the Dynamic Behaviour of a Mechanical Chain Tensioner by Functional Tolerancing Calì, M. – Oliveri, S.M. – Ambu, R. – Fichera, G. Michele Calì1,* – Salvatore Massimo Oliveri1 – Rita Ambu2 – Gabriele Fichera3 1University of Catania, Electric, Electronics and Computer Engineering Department, Italy 2University of Cagliari, Department of Mechanical, Chemical and Materials Engineering, Italy 3University of Catania, Civil Engineering and Architecture Department, Italy","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114167726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.320
S. Lalot
This paper focuses on the study of the internal shape factor of sheathed electrical heating elements. First, the studied geometries are presented and three dimensionless parameters are introduced. The analysis of finite elements simulations leads to the proposition of an analytical expression of the dimensionless internal shape factor. Then a non uniformity factor is proposed and it is shown that this non uniformity is in all cases inferior to 6%, and in most cases inferior to 1%. Then the proposed relation is applied to two examples, one determining the maximum heat flux for a given temperature, the second one determining the maximum temperature of the heating wire for a given heat flux.
{"title":"Analytical representation of the internal shape factor of sheathed electrical heating elements","authors":"S. Lalot","doi":"10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.320","DOIUrl":"https://doi.org/10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.320","url":null,"abstract":"This paper focuses on the study of the internal shape factor of sheathed electrical heating elements. First, the studied geometries are presented and three dimensionless parameters are introduced. The analysis of finite elements simulations leads to the proposition of an analytical expression of the dimensionless internal shape factor. Then a non uniformity factor is proposed and it is shown that this non uniformity is in all cases inferior to 6%, and in most cases inferior to 1%. Then the proposed relation is applied to two examples, one determining the maximum heat flux for a given temperature, the second one determining the maximum temperature of the heating wire for a given heat flux.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121480191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ichmt.2004.intthermscisemin.290
E. Adiutori
Natural convection heat transfer correlations are usually in the form Nusselt{Rayleigh}, and occasionally in the form Nusselt{Rayleigh*}. Both forms are inconvenient because they oftentimes require indirect solution: When Nusselt{Rayleigh} correlations are used to calculate heat flux, solution is simple and direct. But when they are used to calculate boundary layer temperature difference, solution must be indirect-i.e. must be based on an indirect method such as iteration or trial-and-error. When Nusselt{Rayleigh*} correlations are used to calculate boundary layer temperature difference, solution is direct. But when they are used to calculate heat flux, solution must be indirect. This manuscript describes an improved form for natural convection heat transfer correlations. The improved form allows direct solution for heat flux and for boundary layer temperature difference. Included in this manuscript are graphical and analytical correlations in the improved form obtained by transforming Nu{Ra} correlations from the literature.
{"title":"An improved form for natural convection heat transfer correlations","authors":"E. Adiutori","doi":"10.1615/ichmt.2004.intthermscisemin.290","DOIUrl":"https://doi.org/10.1615/ichmt.2004.intthermscisemin.290","url":null,"abstract":"Natural convection heat transfer correlations are usually in the form Nusselt{Rayleigh}, and occasionally in the form Nusselt{Rayleigh*}. Both forms are inconvenient because they oftentimes require indirect solution: When Nusselt{Rayleigh} correlations are used to calculate heat flux, solution is simple and direct. But when they are used to calculate boundary layer temperature difference, solution must be indirect-i.e. must be based on an indirect method such as iteration or trial-and-error. When Nusselt{Rayleigh*} correlations are used to calculate boundary layer temperature difference, solution is direct. But when they are used to calculate heat flux, solution must be indirect. This manuscript describes an improved form for natural convection heat transfer correlations. The improved form allows direct solution for heat flux and for boundary layer temperature difference. Included in this manuscript are graphical and analytical correlations in the improved form obtained by transforming Nu{Ra} correlations from the literature.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116597241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2004.INTTHERMSCISEMIN.610
M. Amin, Joel D. Lindstrom
Hybridized Carbonate and Solid Oxide fuel cell power plants are currently under investigation to fulfill demands for high efficiency and low emissions. Selection of high performance, compact recuperators is essential for such applications. In this paper compact heat exchanger (CHEX) technology applicable to hybrid fuel cell and gas turbine technology has been extensively reviewed. Various compact heat exchanger designs pertinent to gas-gas recuperative duties for fuel cell and gas turbine (FCGT) hybrid systems are presented. The type of CHEXs considered in this study included: brazed plate-fin, fin-tube, microchannel, primary surface and spiral. Comparison of the candidate designs is performed by rating each exchanger with a set of desired criteria. Based on this rating procedure, two CHEX designs namely, plate-fin and microchannel were chosen for further review. Plain, strip, louver, wavy and semicircular surface geometries were then analyzed with a numerical CHEX sizing procedure ultimately to select the most suitable surface geometry for FCGT systems. The brazed plate-fin CHEX having the louver fin geometry was chosen, where numerical results show that this surface holds the greatest potential for CHEX size and cost reduction.
{"title":"Evaluation of compact heat exchanger technologies for hybrid fuel cell and gas turbine system recuperators","authors":"M. Amin, Joel D. Lindstrom","doi":"10.1615/ICHMT.2004.INTTHERMSCISEMIN.610","DOIUrl":"https://doi.org/10.1615/ICHMT.2004.INTTHERMSCISEMIN.610","url":null,"abstract":"Hybridized Carbonate and Solid Oxide fuel cell power plants are currently under investigation to fulfill demands for high efficiency and low emissions. Selection of high performance, compact recuperators is essential for such applications. In this paper compact heat exchanger (CHEX) technology applicable to hybrid fuel cell and gas turbine technology has been extensively reviewed. Various compact heat exchanger designs pertinent to gas-gas recuperative duties for fuel cell and gas turbine (FCGT) hybrid systems are presented. The type of CHEXs considered in this study included: brazed plate-fin, fin-tube, microchannel, primary surface and spiral. Comparison of the candidate designs is performed by rating each exchanger with a set of desired criteria. Based on this rating procedure, two CHEX designs namely, plate-fin and microchannel were chosen for further review. Plain, strip, louver, wavy and semicircular surface geometries were then analyzed with a numerical CHEX sizing procedure ultimately to select the most suitable surface geometry for FCGT systems. The brazed plate-fin CHEX having the louver fin geometry was chosen, where numerical results show that this surface holds the greatest potential for CHEX size and cost reduction.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115610416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.750
D. Sakellari, P. Lundqvist
The present environmental concerns and the rising human requirement for solutions with better comfort and lower costs have resulted in an increased awareness for the energy use in the built environment. Technical advances in building structural systems and materials, heating and other comfort-providing systems and controlling strategies all lead to the integration of building technology with the function of buildings and the aesthetics. Therefore, in the process of improving the performance of energy systems and increasing the energy efficiency, integrated system approaches are of high importance. Performing the necessary energy analysis before any construction-installation occurs can help designers and decision makers reach guided solutions. Hence, a broad range of calculation tools for evaluating the operation of energy systems and the controls in buildings have been developed the latest years with different levels of complexity and angles of focus. However, research and development regarding holistic energy system designs and techniques are in their infancy. The standard tactic has been to isolate system parts, study them as stand-alone sub-systems and focus on optimising components or processes of a complex function. In the present study, it is demonstrated the necessity for uniting energy engineers, architects, installers and technicians regarding decision making upon the energy use for heating, ventilation and air-conditioning (HVAC) in the built environment. Systems approach has been employed for studying the research issue that is presented in the current thesis. An extended part of this treatise has been devoted to systems thinking in practice. The thesis demonstrates systematic methods of modelling and analysing certain, integrated, domestic, HVAC applications. The reference system boundaries enclose the building as a construction and as a dynamic function, a comfort-providing system based on a heat pump, a low-temperature hydronic heat distribution system and controls in a residential application. Obviously, these are not the only components met in a hydronic heating system. Numerous pieces of equipment, as piping, circulating pumps, expansion tanks, zone valves, relief valves and other essential elements are needed to make a safe and functional heating system. However, this study focuses on the analysis of the chosen reference system. Several models have been developed in the computational tools of TRNSYS and EES. These tools have been employed because they allow co-solving, hence the integrated system as well as the interaction between the different parts of the system can be studied. The foremost result of this study is that approaching the system as a whole provides a better picture of the operation of every system component and the interaction between them. Explanations are given for the parameters that have a significant impact on the system’s performance. The thesis shows the importance of factors that are not easy to predict, a
{"title":"Towards energy-use optimisation of a domestic heating system based on a heat pump","authors":"D. Sakellari, P. Lundqvist","doi":"10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.750","DOIUrl":"https://doi.org/10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.750","url":null,"abstract":"The present environmental concerns and the rising human requirement for solutions with better comfort and lower costs have resulted in an increased awareness for the energy use in the built environment. Technical advances in building structural systems and materials, heating and other comfort-providing systems and controlling strategies all lead to the integration of building technology with the function of buildings and the aesthetics. Therefore, in the process of improving the performance of energy systems and increasing the energy efficiency, integrated system approaches are of high importance. Performing the necessary energy analysis before any construction-installation occurs can help designers and decision makers reach guided solutions. Hence, a broad range of calculation tools for evaluating the operation of energy systems and the controls in buildings have been developed the latest years with different levels of complexity and angles of focus. However, research and development regarding holistic energy system designs and techniques are in their infancy. The standard tactic has been to isolate system parts, study them as stand-alone sub-systems and focus on optimising components or processes of a complex function. In the present study, it is demonstrated the necessity for uniting energy engineers, architects, installers and technicians regarding decision making upon the energy use for heating, ventilation and air-conditioning (HVAC) in the built environment. Systems approach has been employed for studying the research issue that is presented in the current thesis. An extended part of this treatise has been devoted to systems thinking in practice. The thesis demonstrates systematic methods of modelling and analysing certain, integrated, domestic, HVAC applications. The reference system boundaries enclose the building as a construction and as a dynamic function, a comfort-providing system based on a heat pump, a low-temperature hydronic heat distribution system and controls in a residential application. Obviously, these are not the only components met in a hydronic heating system. Numerous pieces of equipment, as piping, circulating pumps, expansion tanks, zone valves, relief valves and other essential elements are needed to make a safe and functional heating system. However, this study focuses on the analysis of the chosen reference system. Several models have been developed in the computational tools of TRNSYS and EES. These tools have been employed because they allow co-solving, hence the integrated system as well as the interaction between the different parts of the system can be studied. The foremost result of this study is that approaching the system as a whole provides a better picture of the operation of every system component and the interaction between them. Explanations are given for the parameters that have a significant impact on the system’s performance. The thesis shows the importance of factors that are not easy to predict, a","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"306 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117059242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.340
S. Prstic, M. Iyengar, A. Bar-Cohen
Studies using commercial computational fluid dynamics software, running on a supercomputer, were carried out to investigate the effects of fin density, inlet duct velocity, and clearance area ratio, on the extent of flowbypass and its impact on the thermal performance of the heat sink. Flow bypass was found to increase with increasing fin density and clearance, while remaining relatively insensitive to inlet duct velocity. An optimum geometry, for a fixed inlet duct velocity, bypass clearance, fixed heat sink volume, and constant thickness, was determined.
{"title":"Bypass effect in high performance heat sinks","authors":"S. Prstic, M. Iyengar, A. Bar-Cohen","doi":"10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.340","DOIUrl":"https://doi.org/10.1615/ICHMT.2000.THERSIEPROCVOL2THERSIEPROCVOL1.340","url":null,"abstract":"Studies using commercial computational fluid dynamics software, running on a supercomputer, were carried out to investigate the effects of fin density, inlet duct velocity, and clearance area ratio, on the extent of flowbypass and its impact on the thermal performance of the heat sink. Flow bypass was found to increase with increasing fin density and clearance, while remaining relatively insensitive to inlet duct velocity. An optimum geometry, for a fixed inlet duct velocity, bypass clearance, fixed heat sink volume, and constant thickness, was determined.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128090083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1615/ICHMT.2004.INTTHERMSCISEMIN.490
J. Dirker, Amaud G. Malan, J. Meyer
The optimum aspect ratios of uniformly distributed embedded rectangular cross-sectioned solid cooling inserts in a heat-generating medium are investigated. Numerical investigations were performed to determine and characterise how various geometric and thermal parameters determine these optimum shapes.
{"title":"Thermal characterisation of rectangular cooling shapes in heat generating mediums : A three-dimensional investigation","authors":"J. Dirker, Amaud G. Malan, J. Meyer","doi":"10.1615/ICHMT.2004.INTTHERMSCISEMIN.490","DOIUrl":"https://doi.org/10.1615/ICHMT.2004.INTTHERMSCISEMIN.490","url":null,"abstract":"The optimum aspect ratios of uniformly distributed embedded rectangular cross-sectioned solid cooling inserts in a heat-generating medium are investigated. Numerical investigations were performed to determine and characterise how various geometric and thermal parameters determine these optimum shapes.","PeriodicalId":237575,"journal":{"name":"Strojniški vestnik","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128112597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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