Modelling of Turbulent Flow and Heat Transfer Phenomena in Pipes of District Heating Systems Including Transient Temperature Propagation
(2006)- Abstract
- Modern district heating systems, a carbon lean technology, involves dual usage of the energy due to the possibility to redistribute heat derived from numerous sources, such as industrial processes, refuse incineration, geothermal sources and combined heat and power plants. Such heat source flexibility facilitates the optimal usage of energy resources by varying the amount of purchased heat depending on demand, price and availability. As a result, the operating conditions are never stable and involve pronounced thermal and hydraulic transient regimes, in particular, temperature waves combined with temperature fluctuations. The prediction tools used for these phenomena have been applied for the optimization of the operational regimes. There... (More)
- Modern district heating systems, a carbon lean technology, involves dual usage of the energy due to the possibility to redistribute heat derived from numerous sources, such as industrial processes, refuse incineration, geothermal sources and combined heat and power plants. Such heat source flexibility facilitates the optimal usage of energy resources by varying the amount of purchased heat depending on demand, price and availability. As a result, the operating conditions are never stable and involve pronounced thermal and hydraulic transient regimes, in particular, temperature waves combined with temperature fluctuations. The prediction tools used for these phenomena have been applied for the optimization of the operational regimes. There is however, a need to identify the limitations of the prediction tools and to also improve the methods for more accurate simulations, to enable extended usage of the benefits of these tools in the understanding of transient heat transfer mechanics and to develop effective operational strategies.
This work has been concerned with the modelling of turbulent flow and heat transfer phenomena in pipes in district heating systems, especially focusing on transient temperature propagation. Both simplified models and turbulence models have been used and their performances have been assessed against experimental data. In the simplified model, the fluid flow conditions were simplified by assuming a non-viscous fluid flow, contrary to the turbulence models, where the complex flow patterns occurring in pipe bends and T-connections were simulated in details. In both cases, the pipe flow was treated as a conjugated heat transfer problem, i.e., it included the effect of pipe wall heat conduction.
The limitations of simplified approaches have been examined for the following cases: district heating pipelines, and the Neastved and Madumvej district heating networks located in Denmark. Simplified approaches provided a good approximation, particularly for representing the time delay in a system, as long as it is not used to predict the temperature value at a specific time during the emergence of the temperature changes. These values deviated from the measured values markedly for i) relatively large and sudden temperature changes at the network inlet and ii) low velocities combined with low turbulent Reynolds numbers. Other factors that can affect the temperature wave propagation throughout the network were also discussed in this work.
The performance of turbulence models, including different versions of high Reynolds number two-equation models, (mostly k-epsilon type), have been investigated for a pipe-network fragment of a district heating system. Available experimental data has been used for validation. A methodology for analysing the transient temperature propagation was proposed, where transient values are in principle not linked with the average thermal level of the system. The strength and weakness of the above-mentioned models are discussed in this thesis.
Moreover, heat transfer was modelled in a counter-flow double pipe arrangement (i.e., two adjacent pipes placed in a common insulation), which is practically applied in domestic hot water systems. The heat transfer coefficient and temperature distributions were predicted for typical operating regimes in such systems. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/547245
- author
- Gabrielaitiene, Irina LU
- supervisor
-
- Bengt Sundén LU
- opponent
-
- Professor Loyd, Dan, Linköpings Universitet
- organization
- publishing date
- 2006
- type
- Thesis
- publication status
- published
- subject
- keywords
- 'district heating systems', Energiforskning, Energy research, 'turbulence modelling'., 'modelling temperature dynamics'
- pages
- 100 pages
- publisher
- Lund University (Media-Tryck)
- defense location
- M:B, M-huset, Ole Römers väg 1, Lunds Tekniska Högskola
- defense date
- 2006-10-12 10:15:00
- external identifiers
-
- other:ISRN:LUTMDN/TMHP—06/1044—SE
- ISBN
- 978-91-628-6958-8
- language
- English
- LU publication?
- yes
- additional info
- Irina Gabrielaitiene, Benny Bøhm and Bengt Sunden. 2006. Evaluation of approaches for modelling temperature wave propagation in district heating pipelines Journal Heat Transfer Engineering, (inpress)Irina Gabrielaitiene, Benny Bohm and Bengt Sunden. 2006. Modelling Temperature Dynamics of a District Heating System in Naestved, Denmark – a Case Study Journal Energy Conversion and Management, (inpress)Irina Gabrielaitiene, Janusz Wollerstrand and Bengt Sunden. 2006. Proceedings of the 9th International Conference on Advance Computational Methods in Heat Transfer, 2006. Wessex Institute Of TechnologyIrina Gabrielaitiene, Benny Bøhm, Helge V. Larsen and Bengt Sunden. 2006. Dynamic performance of district heating system in Madumvej, Denmark Proceedings of the 10th International Symposium on District Heating and Cooling, 2006.Irina Gabrielaitiene, Benny Bøhm and Bengt Sunden. . Prediction of temperature propagation a pipe-network fragment of a district heating system employing turbulence modelling (manuscript)
- id
- c172c8a7-2ecd-459f-959d-4c6dbec444a2 (old id 547245)
- date added to LUP
- 2016-04-01 17:01:37
- date last changed
- 2018-11-21 20:46:03
@phdthesis{c172c8a7-2ecd-459f-959d-4c6dbec444a2, abstract = {{Modern district heating systems, a carbon lean technology, involves dual usage of the energy due to the possibility to redistribute heat derived from numerous sources, such as industrial processes, refuse incineration, geothermal sources and combined heat and power plants. Such heat source flexibility facilitates the optimal usage of energy resources by varying the amount of purchased heat depending on demand, price and availability. As a result, the operating conditions are never stable and involve pronounced thermal and hydraulic transient regimes, in particular, temperature waves combined with temperature fluctuations. The prediction tools used for these phenomena have been applied for the optimization of the operational regimes. There is however, a need to identify the limitations of the prediction tools and to also improve the methods for more accurate simulations, to enable extended usage of the benefits of these tools in the understanding of transient heat transfer mechanics and to develop effective operational strategies.<br/><br> <br/><br> This work has been concerned with the modelling of turbulent flow and heat transfer phenomena in pipes in district heating systems, especially focusing on transient temperature propagation. Both simplified models and turbulence models have been used and their performances have been assessed against experimental data. In the simplified model, the fluid flow conditions were simplified by assuming a non-viscous fluid flow, contrary to the turbulence models, where the complex flow patterns occurring in pipe bends and T-connections were simulated in details. In both cases, the pipe flow was treated as a conjugated heat transfer problem, i.e., it included the effect of pipe wall heat conduction.<br/><br> <br/><br> The limitations of simplified approaches have been examined for the following cases: district heating pipelines, and the Neastved and Madumvej district heating networks located in Denmark. Simplified approaches provided a good approximation, particularly for representing the time delay in a system, as long as it is not used to predict the temperature value at a specific time during the emergence of the temperature changes. These values deviated from the measured values markedly for i) relatively large and sudden temperature changes at the network inlet and ii) low velocities combined with low turbulent Reynolds numbers. Other factors that can affect the temperature wave propagation throughout the network were also discussed in this work.<br/><br> <br/><br> The performance of turbulence models, including different versions of high Reynolds number two-equation models, (mostly k-epsilon type), have been investigated for a pipe-network fragment of a district heating system. Available experimental data has been used for validation. A methodology for analysing the transient temperature propagation was proposed, where transient values are in principle not linked with the average thermal level of the system. The strength and weakness of the above-mentioned models are discussed in this thesis.<br/><br> <br/><br> Moreover, heat transfer was modelled in a counter-flow double pipe arrangement (i.e., two adjacent pipes placed in a common insulation), which is practically applied in domestic hot water systems. The heat transfer coefficient and temperature distributions were predicted for typical operating regimes in such systems.}}, author = {{Gabrielaitiene, Irina}}, isbn = {{978-91-628-6958-8}}, keywords = {{'district heating systems'; Energiforskning; Energy research; 'turbulence modelling'.; 'modelling temperature dynamics'}}, language = {{eng}}, publisher = {{Lund University (Media-Tryck)}}, school = {{Lund University}}, title = {{Modelling of Turbulent Flow and Heat Transfer Phenomena in Pipes of District Heating Systems Including Transient Temperature Propagation}}, year = {{2006}}, }