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Stojanovic, Bojan
Publications (10 of 17) Show all publications
Hallberg, D., Stojanovic, B. & Akander, J. (2012). Status, needs and possibilities for service life prediction and estimation of district heating distribution networks. Structure and Infrastructure Engineering, 8(1), 41-54
Open this publication in new window or tab >>Status, needs and possibilities for service life prediction and estimation of district heating distribution networks
2012 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 8, no 1, p. 41-54Article, review/survey (Refereed) Published
Abstract [en]

An optimised and proactive maintenance strategy aims to maximise the economical profit, minimise environmental impacts and keep the risk of failure to a low level. Implementation of such strategy in the context of district heating requires efforts and abilities for predicting future performances and estimating service life of district heating components. A literature review on failures (damages and performance reductions) occurring on district heating pipes, reveals that failures in district heating pipes are mainly leaks due to corrosion or mechanical impacts and reduced thermal insulation performance: leaks being the more serious damage type. A feasible service life estimation method for this type of damage is the Factor Method. Since the application of this method within the context of DH pipes has not been found in other publications, this paper focuses on describing the method and discusses the possibilities on how to apply it in two specific cases with respect to leakage: service life estimation of repaired district heating pipe sections (i.e. maintenance of district heating network) and of district heating pipes in new or extended district heating networks. A particular attention is paid on which modifying factors to consider and how to quantify them.

Keywords
district heating, maintenance strategy, service life, Factor Method
National Category
Materials Engineering
Identifiers
urn:nbn:se:hig:diva-11021 (URN)10.1080/15732470903213740 (DOI)000302541400003 ()2-s2.0-84855962123 (Scopus ID)
Available from: 2011-12-09 Created: 2011-12-09 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B., Hallberg, D. & Akander, J. (2010). A steady state thermal duct model derived by fin-theory approach and applied on an unglazed solar collector. Solar Energy, 84(10), 1838-1851
Open this publication in new window or tab >>A steady state thermal duct model derived by fin-theory approach and applied on an unglazed solar collector
2010 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 10, p. 1838-1851Article in journal (Refereed) Published
Abstract [en]

This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (ID) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler ID analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no 'or negligible' temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the ID isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); ID heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition.

Keywords
Unglazed solar collector, Roof integrated, Duct, Modelling, Fin-theory, Benchmarking
National Category
Energy Engineering Materials Engineering
Identifiers
urn:nbn:se:hig:diva-10265 (URN)10.1016/j.solener.2010.06.016 (DOI)000282498500009 ()2-s2.0-77956180250 (Scopus ID)
Available from: 2011-09-22 Created: 2011-09-21 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B. & Akander, J. (2010). Build-up and long-term performance test of a full-scale solar-assisted heat pump system for residential heating in Nordic climatic conditions. Applied Thermal Engineering, 30(2-3), 188-195
Open this publication in new window or tab >>Build-up and long-term performance test of a full-scale solar-assisted heat pump system for residential heating in Nordic climatic conditions
2010 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 2-3, p. 188-195Article in journal (Refereed) Published
Abstract [en]

This paper presents the build-up and long-term performance test of a full-scale Solar-Assisted Heat Pump System (SAHPS) for residential heating in Nordic climatic conditions. This particular SAHPS was developed within the EU project ENDCHOUSING, by predominantly using components and techniques that are available on the market. The analysis primarily focuses on system performance, with emphasis on Heat Pump (HP) and total system Seasonal Performance Factor (SPF), based on long-term and full-scale operation. Analysis shows that despite unfavourable building conditions, for low energy use and utilisation of a SAHPS, the system was successfully in full operation (for about 2 years) fulfilling heating requirements. Data processing of the series representing the full year period of 2007(February)-2008(February), presented a HP and total SAHPS performance of. SPF(HP) = 2.85 and SPF(SAHPS) = 2.09. The authors argue that with an optimised SAHPS control and operation strategy, additional use of circulation pumps and energy (electricity) could be vastly reduced, hence attaining a SPF(SAHPS) value that is in parity with the SPF(HP). As the Nordic (Swedish) Endohousing SAHPS has not yet been properly optimised/designed and installed in an appropriate house, the SPFHP = 2.85 is considered satisfactory.

Keywords
Solar-assisted heat pump system, Roof-integrated unglazed solar collector, Ground heat storage/source, Long-term, Full-scale, Test
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-10276 (URN)10.1016/j.applthermaleng.2009.08.004 (DOI)000272001100015 ()2-s2.0-74449090530 (Scopus ID)
Available from: 2011-09-22 Created: 2011-09-21 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B. (2009). Lifetime performance assessment of thermal systems: studies on building, solar and district heating applications. (Doctoral dissertation). Stockholm: KTH
Open this publication in new window or tab >>Lifetime performance assessment of thermal systems: studies on building, solar and district heating applications
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH, 2009. p. 112
Keywords
lifetime performance, degradation, assessment, modelling, field exposure, thermal components and systems
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:hig:diva-4918 (URN)978-91-7415-384-2 (ISBN)
Public defence
(English)
Available from: 2009-07-03 Created: 2009-07-03 Last updated: 2018-04-10Bibliographically approved
Hallberg, D., Akander, J., Stojanovic, B. & Kedbäck, M. (2008). Life Cycle Management System: a planning tool supporting Long-term based design and maintenance planning. In: A. Nil Türkeri, Özkan Sengül (Ed.), Durability of Building Materials & Components 11: Globality and Locality in Durability. Paper presented at 11DBMC Conference on Durability of Building Materials and Components "Globality and Locality in Durability", in Istanbul, Turkey, May 2008 (pp. 1871-1878). Istanbul: Istanbul Technical University
Open this publication in new window or tab >>Life Cycle Management System: a planning tool supporting Long-term based design and maintenance planning
2008 (English)In: Durability of Building Materials & Components 11: Globality and Locality in Durability / [ed] A. Nil Türkeri, Özkan Sengül, Istanbul: Istanbul Technical University , 2008, p. 1871-1878Conference paper, Published paper (Refereed)
Abstract [en]

Construction projects include large amounts of information that has to be communicated to a number of actors, such as authorities, companies, clients and end users. Information exchange is complex, involving various players on different levels and phases of the construction process. For private clients, who generally have little experience and knowledge of this process, the on-going “Bygga Villa”-project has developed a web-portal, which offers them relevant information about the process and a number of services to facilitate realisation of their projects. One of the services provides a tool for supporting long-term strategy planning. The tool is based on the Life cycle Management System (LMS) that is a predictive and generic life cycle-based management system, aimed to support decision-making and planning of optimal design and maintenance of any construction works. The LMS-Bygga Villa tool estimates service life and maintenance intervals of different building parts and systems based on environmental-dependent degradation models. Simulated scenarios can give optimised solutions by applying life cycle cost analysis. This paper presents two case studies within LMS-Bygga Villa. The first case focuses on service life performance analysis of exterior parts of buildings. The second focuses on service life performance analysis of energy systems; here specifically a borehole assisted heat pump system used for heating a Swedish single-family residence.

Place, publisher, year, edition, pages
Istanbul: Istanbul Technical University, 2008
Keywords
Life cycle Management System, design, maintenance, service life, heat pump system
National Category
Civil Engineering
Identifiers
urn:nbn:se:hig:diva-1708 (URN)978-975-561-325-3 (hela verket) (ISBN)978-975-561-329-1 (vol. 4) (ISBN)
Conference
11DBMC Conference on Durability of Building Materials and Components "Globality and Locality in Durability", in Istanbul, Turkey, May 2008
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B., Akander, J. & Eriksson, B. (2008). Natural and semi-natural field exposure testing and analysis, on optical degradation of a building integrated unglazed solar collector surface. Materials and Structures, 41(6), 1057-1071
Open this publication in new window or tab >>Natural and semi-natural field exposure testing and analysis, on optical degradation of a building integrated unglazed solar collector surface
2008 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 41, no 6, p. 1057-1071Article in journal (Refereed) Published
Abstract [en]

Durability is of great importance when considering sustainable energy systems. In turn it lays emphasis on assessing performance over time of energy systems and components. This paper presents a study on optical degradation of a building-integrated Unglazed Solar Collector (USC) surface, by exposing USC specimens to a natural and semi-natural field exposure test. Particular interest is devoted to the semi-natural field exposure test method evaluation, and the degradation of optical properties. The study showed that about 11 months of field exposure testing did not cause any significant optical (total solar absorptance and IR emittance) or material (surface coating) degradation; although measurements revealed a decrease in specular reflectance as diffuse increased. It was likely due to surface pollution that predominantly consisted of quartz. The study also showed that it is possible to achieve a considerable increased moisture exposure on test surfaces (seminatural field exposure test), through a relatively simple cooling device (Direct-Air Peltier-Element) and rough control strategy.

Keywords
Natural and semi-natural field exposure, Optical degradation, Unglazed solar collector
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:hig:diva-2734 (URN)10.1617/s11527-007-9306-1 (DOI)000256434800006 ()2-s2.0-44649195111 (Scopus ID)
Available from: 2008-05-28 Created: 2008-05-28 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B. & Akander, J. (2008). Oglasade takintegrerade solfångare: Ett energitekniskt aktivt byggnadsskal. Bygg & Teknik (4)
Open this publication in new window or tab >>Oglasade takintegrerade solfångare: Ett energitekniskt aktivt byggnadsskal
2008 (Swedish)In: Bygg & Teknik, ISSN 0281-658X, no 4Article in journal (Other (popular science, discussion, etc.)) Published
National Category
Building Technologies Other Materials Engineering
Identifiers
urn:nbn:se:hig:diva-1775 (URN)
Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2018-03-13Bibliographically approved
Akander, J., Stojanovic, B. & Hallberg, D. (2008). Simulated Long-term Thermal Performance of a Building That Utilizes a Heat Pump System and Borehole. In: A. Nil Türkeri, Özkan Sengül (Ed.), Durability of Building Materials & Components 11: Globality and Locality in Durability. Paper presented at 11DBMC Conference on Durability of Building Materials and Components "Globality and Locality in Durability", in Istanbul, Turkey, 11-14 May 2008. Istanbul, Turkey: Istanbul Technical University
Open this publication in new window or tab >>Simulated Long-term Thermal Performance of a Building That Utilizes a Heat Pump System and Borehole
2008 (English)In: Durability of Building Materials & Components 11: Globality and Locality in Durability / [ed] A. Nil Türkeri, Özkan Sengül, Istanbul, Turkey: Istanbul Technical University, 2008Conference paper, Published paper (Refereed)
Abstract [en]

Over the last decades, installation and use of heat pumps has grown rapidly in Sweden, to the extent that these mainly or partly heat roughly 25 % of the heated floor space in single-family houses. A majority are ground coupled where the heat exchanger is a borehole of 60-220 m depth. As the heat pump system operates, heat extraction will in time reduce borehole temperatures, rendering lowered efficiency of the heat pump system thus directly affecting its economical and environmental aspects. Within the building sector, durability and life performance dynamics of energy systems is often not reflected upon. System performance and efficiency is assumed to be static over time, changing only due to different operation scenarios. This paper serves to quantify the long-term thermal performance degradation of a component, in this case the borehole, and how the degradation of this component affects performance-over-time of an entire system, in this case the heating system of the building. A dynamic thermal simulation model is used to assess the long-term thermal performance of the borehole. The building, which the heat pump serves, is assumed to be a typical Swedish house with normal energy consumption. Simulation results show that the depth of the borehole is of great importance to limit over-time temperature drops. The efficiency of the heat pump system is directly dependent of temperatures in the borehole. How the overall system performance is affected by component performance degradation, is highlighted.

Place, publisher, year, edition, pages
Istanbul, Turkey: Istanbul Technical University, 2008
Keywords
Energy consumption, service life, heat pump system, borehole, modelling
National Category
Civil Engineering
Identifiers
urn:nbn:se:hig:diva-11019 (URN)978-975-561-325-3 (hela verket) (ISBN)978-975-561-329-1 (vol. 4) (ISBN)
Conference
11DBMC Conference on Durability of Building Materials and Components "Globality and Locality in Durability", in Istanbul, Turkey, 11-14 May 2008
Available from: 2011-12-09 Created: 2011-12-09 Last updated: 2018-03-13Bibliographically approved
Stojanovic, B. & Akander, J. (2008). Use of a Peltier Element to Increase Time of Wetness of Unglazed Solar Collector Specimens in a Natural Field Exposure Test. In: Durability of Building Materials & Components 11 (11DBMC), Istanbul, Turkey, 11-14 May 2008. Paper presented at 11DBMC, Istanbul, Turkey, 11-14 May 2008 (pp. 1169-1175).
Open this publication in new window or tab >>Use of a Peltier Element to Increase Time of Wetness of Unglazed Solar Collector Specimens in a Natural Field Exposure Test
2008 (English)In: Durability of Building Materials & Components 11 (11DBMC), Istanbul, Turkey, 11-14 May 2008, 2008, p. 1169-1175Conference paper, Published paper (Refereed)
Abstract [en]

In accelerated testing, material specimens are exposed to completely artificial environments, where exposure to individual degradation agents is enhanced. In contrast, field-testing exposes specimens to multiple degradation agents. When performing a semi-natural test, the influence of a selected degradation agent may be increased while the specimen is still situated in its natural environment. Moisture is such an agent. In an experimental set-up for evaluating long-term optical performance of an building integrated Unglazed Solar Collector, a sub-task was to increase Time of Wetness (TOW) for several collector specimens for two reasons: to “simulate” an active cooling of the component as is the case for solar collectors; and to assess the role of TOW on optical degradation of the solar collector. Specimen cooling and increase in TOW was achieved by utilisation of a Direct-Air Peltier Element. TOW was estimated through measurements with WETCORR sensors (monitoring surface temperatures and moisture) and climate parameters (temperature and relative humidity) at site. At this particular test site in Gävle, Sweden, TOW was more than doubled in comparison to non-cooled surfaces. The Peltier Element proved to be inexpensive and flexible for this purpose.

Keywords
Peltier Element, time of wetness, semi-natural environment, optical durability.
National Category
Building Technologies Other Materials Engineering
Identifiers
urn:nbn:se:hig:diva-1773 (URN)978-975-561-328-4 (ISBN)
Conference
11DBMC, Istanbul, Turkey, 11-14 May 2008
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2018-03-13Bibliographically approved
Hallberg, D. & Stojanovic, B. (2007). Analytical and numerical thermal modelling & analysis of an building integrated unglazed solar collector: PhD course paper. In: Mathematics for PhD-students in building science. Stockholm: Architecture and the Built Environment, Royal Institute of Technology
Open this publication in new window or tab >>Analytical and numerical thermal modelling & analysis of an building integrated unglazed solar collector: PhD course paper
2007 (English)In: Mathematics for PhD-students in building science, Stockholm: Architecture and the Built Environment, Royal Institute of Technology , 2007Chapter in book (Other (popular science, discussion, etc.))
Abstract [en]

The objective of this report is to derive an analytical and numerical USC model for thermal analysis. These models are meant to calculate USC temperature variation across the USC duct as well as the fluid temperature along the USC. The main purpose of the analytical model is to attain a detailed steady state tool for USC (as in this report) design and dimensioning. The numerical model is meant to calculate the time dependant USC thermal performance as well as being a benchmark for the analytical model.

Place, publisher, year, edition, pages
Stockholm: Architecture and the Built Environment, Royal Institute of Technology, 2007
Series
Trita-BYMA, ISSN 0349-5752 ; 2007:2
National Category
Building Technologies Other Materials Engineering
Identifiers
urn:nbn:se:hig:diva-1776 (URN)
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2018-03-13Bibliographically approved
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