| 1. |
- Brembilla, Christian, 1983-
(författare)
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Efficiency factors for space heating system in buildings
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis focuses on the efficiency of the space heating system. In particular, the efficiency factors measure the efficiency of thermal zone. The efficiency factors measures how the energy is used in a space heating. Efficiency factors relatively close to one mean that the energy is used "efficiently'', by contrast, efficiency factors close to the zero mean that the majority of the energy is lost to the outdoor environment. This method for the appraisal of space heating performance reads as if it is apparently simple and intuitive. In reality, the efficiency factor method has several pitfalls.The thesis provides tools, insights and remarks on how to apply the efficiency factor method to space heating systems equipped with hydronic panel radiator and floor heating respectively. Models of the latter heaters together with the multilayer wall were developed and validated to understand the reliability of their predictions. The hypothesis is that the heat stored in the building thermal mass and heaters plays a role in defining the building thermal performance and as a result in the appraisal of the efficiency factors. The validation is based on the sensitivity bands of the models' predictions. The heaters were tested in in a thermostatic booth simulator. Benefits and drawbacks of each model were highlighted to increase awareness of their use in the engineering fields. The results showed how the models accounting for the heat stored performed the charging phase. In addition, results of how the multilayer wall delayed and damped down the heat wave coming from the outdoor environment were presented with the appraisal of the decrement factor and time delay of the indoor temperature. The results of the efficiency factors analysis reveal how the weather affects the efficiency of each locality situated in cold climates. Lastly how different control strategies impact on the efficiency factors of space heating and its distribution system. To conclude, this study highlights the paradoxes around the efficiency factor method. The thesis proposes how such factors have to be interpreted by researchers and scientists tackling the lack of information around this topic.
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| 2. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Hybrid heating system for open-space office/laboratory
- 2015
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Ingår i: Energy, Science and Technology 2015. - Karlsruher, Germany : Karlsruhe, KIT. ; , s. 315-315
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Konferensbidrag (refereegranskat)abstract
- Open-space office/laboratory are quite common in Scandinavia and they are usually designed for multipurposework. There are office area where is possible to work standing up and in the same time to work at the desk. Forthis purpose a hybrid heating system made by electric convectors and panel radiators is investigated. Two stepresponse tests of the hybrid heating system are performed at the laboratory of Umeå University. The first test isexecuted during the week, disturbances from heat sources degrading the quality of the results. The second test isperformed during week-end. The error analysis shows a maximum discrepancies of +0.6 °C between measuredand simulated data. However, a thermal time constant of the room can be deducted and use it for controlling purposes.
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| 3. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Hybrid heating system for open-space office/laboratory
- 2015
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Ingår i: Energy, Science and Technology 2015. - Karlsruhe : Karlsruher Institut für Technologie (KIT). ; , s. 315-315
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Konferensbidrag (refereegranskat)abstract
- Open-space office/laboratory are quite common in Scandinavia and they are usually designed for multipurpose work. There are office area where is possible to work standing up and in the same time to work at the desk. For this purpose a hybrid heating system made by electric convectors and panel radiators is investigated. Two step response tests of the hybrid heating system are performed at the laboratory of Umeå University. The first test is executed during the week, disturbances from heat sources degrading the quality of the results. The second test is performed during week-end. The error analysis shows a maximum discrepancies of +0.6 °C between measured and simulated data. However, a thermal time constant of the room can be deducted and use it for controlling purposes.
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| 4. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Investigation of thermal parameters addressed to a building simulation model
- 2015
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Ingår i: Energy, Science and Technology 2015. - Karlsruher, Germany : Karlsruher Institute of Technology (KIT). ; , s. 128-
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Konferensbidrag (refereegranskat)abstract
- Introduction The uncertainty of setting input parameters in a building model can have a major impact on the simulated output. The tolerance of thermal parameters is a necessary information that helps modeler to know the influence of eachfactors on the outcomes. This paper shows the allowable tolerance of thermal parameters in order to build anaccurate building model.
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| 5. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Investigations of thermal parameters addressed to a building simulation model
- 2015
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Ingår i: Proceedings of BS2015. - India, Hyderabad : International Building Performance Simulation Association (IBPSA). ; , s. 2741-2748, s. 2741-2748
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Konferensbidrag (refereegranskat)abstract
- This paper shows the tolerance of thermal parameters addressed to a building simulation model in relation to the local control of the HVAC system. This work is suitable for a modeler that has to set up a building simulation model. The modeler has to know which parameter needs to be considered carefully and vice-versa which does not need deep investigations. Local differential sensitivity analysis of thermal parameters generates the uncertainty bands for the indoor air. The latter operation is repeated with P, PI and PID local control of the heating system. In conclusion, the local control of a room has a deterministic impact on the tolerance of thermal parameters.
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| 6. |
- Brembilla, Christian, 1983-
(författare)
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Modelling and simulation of building components : thermal interaction between multilayer wall and hydronic radiator
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and Scope: The scope of this thesis is to investigate the thermal behaviour of building components as hydronic radiator and multilayer walls subjected to dynamic conditions. The modelling and simulation of these building components provide information on how these components thermally interact among each other. The thermal interaction is fundamental to know how the energy is used in buildings. In particular, the thermal energy used in rooms can be expressed as the efficiencies for emission in a space heating system. This thesis analyzes the efficiencies for emission of a space heating system equipped with hydronic radiator for Swedish buildings by providing a comprehensive and detailed approach on this topic.Methodology: The methods used in this thesis are: experiment, modelling of multilayer wall and hydronic radiator, the dynamic simulation of the building and the efficiencies for emission of a space heating system. Here, the experiment, known as step response test, shows the heating up process of a hydronic radiator. The observation of the qualitative measurements suggests the most suitable technique of modelling the radiator known as transient modelling with multiple storage elements. The multilayer wall has been discretized both in space and time variable with a Finite Difference Method. Dynamic simulation of the building provides the efficiencies for emission of a space heating system.Findings: The experimental results show how the radiator performs the charging phase. The performance of the transient model is compared with lumped steady state models in terms of temperature of exhaust flow and total heat emitted. Results of the dynamic simulation show how buildings located in a Northern climate use the energy in a better way than Southern climates in Sweden. Heavy active thermal mass provides higher efficiencies for emission than light thermal mass. Radiators with connection pipes located on the same side react faster at the thermodynamic changing of the mass flow rate by providing higher efficiencies for emission than radiators with connection pipes located on the opposite side.Conclusion and Outlook: This thesis increases the knowledge about the modelling and simulation of hydronic radiators and multilayer walls. More research is needed on this topic to encompass modelling details of building components often ignored. The modelling and simulation of building components are the key to understand how building components thermally interact with each other. The thermal interaction among building components is a fundamental parameter for the assessment of efficiencies of emission of the space heating system. In the near future, the concept of efficiencies of emission can be implemented in National Building Code, therefore, this study provides guidelines on how to assess these efficiencies.
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| 7. |
- Brembilla, Christian, 1983-, et al.
(författare)
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One dimensional model of transient heat conduction through multilayer walls/slabs : The functionality of insulation and brick materials in terms of decrement factor and time lag
- 2016
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Multilayer wall is a common type of building envelope used in buildings located in cold climates. The building envelope is typically composed by internal and external masses made by bricks or concrete separated by a large thickness of insulation material. This paper investigates the thermal behavior of a multilayer wall subjected to temperature excitation on both wall sides. The analysis is conducted by discretizing the continuous space and time variables of the mathematical model identified in the heat equation. Euler backwards solves the numerical model of multilayer wall by providing an unconditionally stable solution. The step response test shows the correct working of the model which reaches the steady state solution. The results of this paper are expressed in terms of temperature of each wall layer against the time. In particular, (i) the large thickness of insulation material separates thermodynamically the outside external mass from the internal mass, (ii) 20 cm thickness of insulation material damps the heat wave with a decrement factor of 3.41 °ͦC and a time lag of 1 hour, (iii) the external brick layer damps the heat wave with a decrement factor of 1.97 °ͦC and a time lag of 5 hours.
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| 8. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Paradoxes in understanding the Efficiency Factors of Space Heating
- 2019
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Ingår i: Energy Efficiency. - Dordrecht : Springer. - 1570-646X .- 1570-6478. ; 12:3, s. 777-786
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Tidskriftsartikel (refereegranskat)abstract
- Efficiency factors are here defined as the thermal energy performance indicators of the space heating. Until recently, the efficiency factors were assumed as one value for space heating located in any climate. This study addresses the problem of how the outdoor climate affects the efficiency factors of a space heating equipped with 1D model of hydronic floor heating. The findings show how the efficiency factors, computed with two numerical methods, are correlated with the solar radiation. This study highlights the paradoxes in understanding the results of efficiency factors analysis. This work suggests how to interpret and use the efficiency factors as a benchmark performance indicator.
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| 9. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Practical support for evaluating efficiency factors of a space heating system in cold climates : modelling and simulation of hydronic panel radiator with different location of connection pipes
- 2017
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Ingår i: Energy Efficiency. - : Springer Science and Business Media LLC. - 1570-646X .- 1570-6478. ; 10:5, s. 1253-1267
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Tidskriftsartikel (refereegranskat)abstract
- Plenty of technical norms, included in the EPBD umbrella, assess the performance of buildings or its sub-systems in terms of efficiency. In particular, EN 15316 and its sub-sections, determine the system energy requirements and the system efficiencies of space heating system. This paper focuses on the estimation of efficiencies for emission of hydronic radiators. The assessment of efficiencies for emission occurs by evaluating the amount of heat emitted from the heat emitter and the extra thermal losses towards building envelope. The heat emitted from radiators varies during the heating up/cooling down phases. A factor that influences the heat emitted during these phases is the location of connection pipes of the radiator. Connection pipes can be located on opposite side or at the same side of the radiator. To better estimate the heat emitted from radiators a transient model with multiple storage elements is used in a building simulation model. Sensitivity analysis encompasses all the possible variations on extra thermal losses due to the building location in different climates, the heaviness of active thermal mass and the type of radiator local control. The final outcome of this paper is a practical support where the designer can easily assess the efficiencies for emission of hydronic radiators for Swedish buildings. As main result, (i) the efficiency for control of space heating system is higher in Northern climates than in Southern climates, (ii) heavy active thermal masses allow higher efficiencies for emission than light active thermal masses, (iii) connection pipes located on the same side of the radiator enable higher efficiencies for emission than pipes located on opposite side.
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| 10. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Predictions' robustness of one-dimensional model of hydronic floor heating : novel validation methodology using a thermostatic booth simulator and uncertainty analysis
- 2018
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Ingår i: Journal of Building Physics. - : Sage Publications. - 1744-2591 .- 1744-2583. ; 41:5, s. 418-444
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Tidskriftsartikel (refereegranskat)abstract
- Hydronic floor heating models provide predictions in estimating heat transfer rates and floor surface temperature. Information on the model performance and range of validity of its results are often lacking in literature. Researchers have to know the accuracy and robustness of the model outcomes for performing energy and climate comfort calculations. This article proposes a novel validation methodology based on the uncertainty analysis of input data/parameters of one-dimensional model of hydronic floor heating tested in a thermostatic booth simulator and compared with experimental measurements. The main results are: (1) prediction accuracy between 0.4% and 2.9% for Tf and between 0.7% and 7.8% for qup when the serpentine has tube spacing (p) of 0.30 m, (2) prediction accuracy between 0.5% and 1.4% for Tf and between 8.7% and 12.9% for qup with p = 0.15m and (3) Tfld mostly affects predictions with oscillations between 6.2% and 2.2% for qup. This model provides robust and reliable predictions exclusively for qup when p = 0.30m.
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| 11. |
- Brembilla, Christian, 1983-, et al.
(författare)
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The impact of control strategies on space heating system efficiency in low-energy buildings
- 2019
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Ingår i: Building Services Engineering Research & Technology. - London : Sage Publications. - 0143-6244 .- 1477-0849. ; 40:6, s. 714-731
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Tidskriftsartikel (refereegranskat)abstract
- In this study efficiency factors measures the thermal energy performance for space heating. This study deals with the influence of control strategies on the effriciency factors of space heating and its distribution system. An adaptive control is developed and applied to two types of heating curves (linear and non-linear) for a low-energy building equipped with renewable energy sources. The building is modelled with a hybrid approach (law driven + data driven model). The design of the floor heating is calibrated and validated by assessing the uncertainty bands for low temperatures and mass flow rate. advantages and disavantages of linear and non-linear heating curves are highlighted to illustrate their impact on space heating thermodynamic behaviour and on the efficiency factors of the space heating system.Practical application: The study reveals that applying commercial building energy simulation software is worthwhile to determine reliable performance predictions. Oversimplified building models, in particular when considering building thermal mass, are not capable of simulating the thermodynamic response of a building subjected to different control strategies. The application of different heating cuirves (linear and non-linear) to massless building models leaves the amount of mass flow rate delivered to the space heating unchanged when the building is subjected to sharp variations of the outdoor temperature.
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| 12. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Transient model of a panel radiator
- 2015
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Ingår i: Energy, Science and Technology 2015. - Karlsruher, Germany : Karlsruher Institut für Technologie (KIT). ; , s. 321-321, s. 321-321
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Konferensbidrag (refereegranskat)abstract
- This paper shows a detailed transient model of a panel radiator considered as a system of multiple storageelements. The experiment records the temperature surface of the panel in the process of heating up. Thequalitative results of the experiment suggest the more appropriate technique for modelling this technology. The transient model performs the modelling with horizontal thermal capacitances connected in series. This modelcalculates the temperature of exhaust flow, heat emission towards indoor environment, temperature gradient onpanel surface, dead and balancing time identified numerically on the chart.
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| 13. |
- Brembilla, Christian, 1983-, et al.
(författare)
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Transient model of a panel radiator
- 2015
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Ingår i: Proceedings of BS2015. - India, Hyderabad : International Building Performance Simulation Association (IBPSA). ; , s. 2749-2756
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Konferensbidrag (refereegranskat)abstract
- This paper shows a transient model of a hydronic panel radiator modelled as a system of multiple storage elements. The experiment´s results suggest the more suitable technique for modelling this technology. The panel radiator is modelled numerically with eight thermal capacitance connected in series by keeping a memory of the heat injected in the thermal unit. The comparison of the performance among lumped steadystate models and transient model, in terms of heat emission and temperature of exhaust flow, shows the potential of the latter approach. To conclude, (1) the transient phase is essential for modelling stocky panels, and (2) this type of modelling has to be addressed for evaluating the performance of low energy buildings.
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