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A Steady State Thermal Duct Model Derived by Fin-Theory Approach and Applied on an Unglazed Solar Collector.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
2009 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 10, 1838-1851 p.Article 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.

Place, publisher, year, edition, pages
2009. Vol. 84, no 10, 1838-1851 p.
Keyword [en]
PERFORMANCE; DEGRADATION; VALIDATION; SYSTEMS; SURFACE; DESIGN; ENERGY
National Category
Building Technologies Materials Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-19461DOI: 10.1016/j.solener.2010.06.016ISI: 000282498500009Scopus ID: 2-s2.0-77956180250OAI: oai:DiVA.org:kth-19461DiVA: diva2:338103
Note
QC 20100810, QC 20111110Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Lifetime Performance Assessment of Thermal Systems: Studies on Building, Solar and Disctrict Heating Applications
Open this publication in new window or tab >>Lifetime Performance Assessment of Thermal Systems: Studies on Building, Solar and Disctrict Heating Applications
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in order to evaluate if these changes will jeopardise the intended system performance requirement, hence service life (SL). The lack of knowledge/approaches and tools for assessing durability and performance-over-time of thermal systems complicates the task of incorporating these aspects in engineering. In turn, this pro-active assessment and analysis is in line with today’s performance based directives, laws and regulations; of which the working life is an essential part. The durability of materials, components and systems is not a topic that is an end in itself, but becomes a vital part in a comprehensive perspective as sustainability. The lifetime performance assessment of thermal systems, as presented in this thesis, shows that it is a vital part of the R&D in the quest of sustainable energy/thermal systems and energy use.

This thesis gives knowledge to the thermal (energy) system/technology R&D and engineering sector, regarding durability and lifetime performance assessment methodologies; but also to the durability of construction works sector, regarding the needs for assessing lifetime performance of materials and components in relation to system performance. It also presents descriptions of requirements on construction works. Specifically, the studies presented in the thesis show how durability and lifetime performance assessment of thermal systems may be sought, with knowledge on: methodologies, exposure test set-ups, modelling and the attainment and use of adequate tools. The main focus is on performance-over-time modelling, tying material/component degradation to altered thermal performance, thereby attaining performance-over-time assessment tools to be used in order to incorporate these aspects when engineering thermal systems; hence enabling the forecasting of SL. The presented work was predominantly done in association to the EU project ENDOHOUSING. The project developed a solar-assisted heat pump system solution, with heat storage, to provide the thermal energy to meet space heating, cooling and hot water requirements for domestic houses in different regions of the EU. The project constituted the platform for the work presented in this thesis, thereby outlining the main context with studies on durability and lifetime performance of:

  • flat plate solar collectors
  • ground heat sources/storages and interaction with a heat pump system
  • evaluation of the ENDOHOUSING solar-assisted heat pump system

The thesis also presents a study of SL prediction and estimation of district heating distribution networks (an additional thermal system application). In this particular context, the Factor Method is proposed as a methodology. The main issue of lifetime performance of thermal systems is how and to what extent performance reduction in individual materials or components influence the overall system performance, as the essence of energy/thermal system sustainability is system performance.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xvi, 112 p.
Keyword
Lifetime performance, degradation, assessment, modelling, field exposure, thermal components and system
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10967 (URN)978-91-7415-384-2 (ISBN)
Public defence
2009-09-11, Gävle Teknikpark, Hörsalen, Nobelvägen 2, Gävle, 10:00 (English)
Opponent
Supervisors
Note
QC 20100810Available from: 2009-09-01 Created: 2009-09-01 Last updated: 2012-03-23Bibliographically approved
2. System for Predictive Life cycle Management of Buildings and Infrastructures
Open this publication in new window or tab >>System for Predictive Life cycle Management of Buildings and Infrastructures
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Life Cycle Management System (LMS) aims at supporting decision-makers and engineers in their efforts to achieve a more optimised proactive life cycle design and maintenance management strategy. LMS is an open and integrative system, which has to be adapted and developed in order to meet the needs and requirements of users. This process should be geared to and governed by the clients. The Architecture, Engineering, Construction and Facility Management (AEC/FM) sector includes all varieties of clients and stakeholders, all of them having different qualifications, possibilities and requirements for implementing, or increasing the feature of predictive maintenance management and optimised proactive strategies. The possibilities of adopting predictive maintenance management are dependent on the availability of performance-over-time and service life forecasting models and methods. The relevance of these models and methods depends on the required level of detailing. Furthermore, the use of the models and methods depends on the availability of reliable input data, such as material data and environmental exposure/in-use condition data. The thesis aims at analysing the possibilities of implementing predictivity in different fields of applications and at evaluating relevant tools facilitating management of information associated with predictive maintenance management systems. The thesis includes studies of three different clients and fields of application; Swedish Road Administration – management of bridges, Locum AB – management of hospital buildings, and Gävle Energi AB – management of district heating distribution systems. While the Swedish Road Administration is responsible to ensure an economically efficient, sustainable transport system for the society throughout the country, Locum AB and Gävle Energi AB compete on an "open" market. The Swedish Road Administration have gathered information about their bridges since 1944, for what reason their bridge management system includes a large amount of valuable data for performance-over- time analyses and service life forecasting. Locum AB has recently begun to systematically gather condition data, why the amount of data is limited. However, since the performance of buildings generally is well known, it is assumed that possibilities of implementing predictive maintenance management tools are rather good. Since district heating pipes are buried into the ground, it is difficult to assess the condition. Therefore, data for service life estimation rely mainly on damage reports. Environmental exposure data on macro or meso level can be obtained from meteorological and environmental institutes, thus making it possible to apply available dose-response and damage functions. Environmental exposure data on a micro level are lacking. Guidelines, methods and tools for environmental measuring and modelling on a micro level are therefore strongly needed. Efficient management of information plays an important role in predictive life cycle management systems. The ongoing development and implementation of open Building Information Model (BIM) tools in the AEC/FM sector is a promising progress of making the information management more cost effective and valuable, especially when open BIM solutions being fully integrated into the AEC/FM business. Geographical Information Systems (GIS) are tools for efficient handling of spatial positioned information. GIS provide possibilities of processing and presenting, e.g., environmental exposure data and environmental risk factors.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. viii, 100 p.
Keyword
Life Cycle Management System, service life, performance-over-time, maintenance management
Identifiers
urn:nbn:se:kth:diva-10312 (URN)978-91-7415-262-3 (ISBN)
Public defence
2009-04-24, Gävle Teknikpark, Hörsalen, Nobelvägen 2, Gävle, 10:00 (English)
Opponent
Supervisors
Note
QC 20100716Available from: 2009-05-06 Created: 2009-05-06 Last updated: 2012-03-14Bibliographically approved

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