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See detailEnergy performance comparison of ventilation-based heating versus water-based heating systems in an efficient residential building
Shirani, Arsalan UL; Merzkirch, Alexander; Leyer, Stephan UL et al

in Fluid Dynamics & Material Processing (in press)

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well ... [more ▼]

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well-known for their usage in passive houses during the past three decades. Available studies on such systems tend mostly to focus only on comparing exhaust air heat pump technology with conventional systems in efficient buildings. Moreover, most of the existing studies ignore the usual presence of the electrical heaters as backup. Besides, a comprehensive study and comparison between different air-based heating system concepts is still missing. In this study, four different air-based heating system concepts separated by the type of heat source of heat pump for heating and domestic hot water are defined. These systems are compared to four conventional heating system, including floor heating and direct electrical system employing dynamic annual simulations. According to simulation results, the systems with floor heating have shown the best system efficiencies and the lowest energy demand in comparison to the other systems. The main reason for this was the lower supply temperatures of the floor heating systems. Between the air heating systems, the system equipped with an outdoor air heat pump showed a better energy performance than an exhaust air system. The main reason for this could be attributed to the power limitation of exhaust air heat pump systems. [less ▲]

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See detailCharacterizing the Theory of Spreading Electric Vehicles in Luxembourg
Arababadi; Leyer, Stephan UL; Leyer, Stephan UL et al

in Sustainability (2021)

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See detailExperimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems
Shirani, Arsalan UL; Merzkirch, Alexander UL; Roesler, Jennifer et al

in Journal of Building Engineering (2021)

Due to the significant energy loss in the building sector, energy efficiency of the buildings and their heating systems is gaining interest especially in the last decades. Application of exhaust air heat ... [more ▼]

Due to the significant energy loss in the building sector, energy efficiency of the buildings and their heating systems is gaining interest especially in the last decades. Application of exhaust air heat pumps as an energy efficient heating technology to cover the heating and venting demand of the building is becoming conventional. The exhaust air heat pumps are attracting considerable interest due to their normally reasonable price and small footprint. This heat pump type is often installed as part of an air based heating system together with electrical heaters. These electrical heaters are installed to cover the residual heating demand and/or to insure thermal comfort. The technology of exhaust air heat pumps has been investigated in several studies. Available studies on exhaust air heat pumps have tended mostly to focus on comparison between different technologies utilized in efficient buildings. Almost all of the existing studies have ignored the actual application of this technology in air based heating systems together with electrical heaters. In this sense, there is still a need for discussion on the influence of different buildings’ standards and control strategies on the heating system performance. The present paper aims to call into question the energy efficiency of exhaust air heat pumps under different boundary conditions. In this study, the results of a long time field monitoring are utilized in order to model the dynamic behavior of an exhaust air heat pump in MATLAB/Simulink. The impact of different boundary conditions on the heat pump’s efficiency is studied and additionally compared to previous studies. The developed model is used for annual simulations of air based hybrid heating systems in three different building standards. Finally, the influence of control strategy on the system performance is investigated. It is shown that under certain boundary conditions and control strategy, the studied system could provide an efficient heating system with acceptable user comfort. Nevertheless, applying conventional heating control methods or installing the system in buildings with high heating energy demand could lead to high electrical energy consumption and/or undesirable thermal comfort. [less ▲]

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See detailField monitoring data on a residential exhaust air heat pump system (air-to-air heat pump)
Shirani, Arsalan UL; Merzkirch, Alexander; Roesler, Jennifer et al

in Data in Brief (2021)

This data article presents the raw data used in the article “Experimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems” (in review). The data set contains ... [more ▼]

This data article presents the raw data used in the article “Experimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems” (in review). The data set contains measurement results of a field monitoring on a residential exhaust air heat pump system (air-to-air heat pump) in Germany. This data could be used to investigate the dynamic behaviour and performance of the exhaust air heat pump systems. The data set contains air temperature and humidity of all four sides of the heat pump unit. Moreover, the electrical consumption of the unit and the dynamic pressure difference on the exhaust side (as indication of the air volume rate) could be also found in the data set. [less ▲]

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See detailPrevention of Electrostatic Charge Generation in Filtration of Low-Conductivity Oils by Surface Modification of Modern Filter Media
Staudt, Johannes; Duchowski, Johan; Leyer, Stephan UL

in Tribology Transactions (2020)

The electrostatic charging behavior of filter elements operating in various hydraulic and lubricating fluids has been re-examined from the perspective of fundamental material properties of the two ... [more ▼]

The electrostatic charging behavior of filter elements operating in various hydraulic and lubricating fluids has been re-examined from the perspective of fundamental material properties of the two materials participating in the event. In contrast to the previously proposed mechanisms that focused predominantly on fluid and material conductivities, new evidence strongly suggests that the relative placement of the substrates in the triboelectric series must be taken into account. The positions occupied in the triboelectric series account for the donor/acceptor tendencies exhibited by the materials when brought close together in close proximity ( 10 nm). Nevertheless, this behavior is only an outward manifestation of the deeper underlying characteristics that include material surface energies and, looking even deeper, the associated electron work functions of the interacting materials. Herein we provide several examples of the enhanced understanding of the electrostatic charging/discharging (ESC/ESD) phenomena as they occur in the course of filtration of hydraulic and lubricating fluids through modern filter elements constructed of synthetic glass fiber and polymer materials. [less ▲]

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See detailModelling of Passive Heat Removal Systems: A Review with Reference to the Framatome BWR Reactor KERENA: Part II
Manthey, René; Viereckl, Frances; Moonesi Shabestary, Amirhosein et al

in Energies (2019)

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven ... [more ▼]

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modeling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I dealt with numerical and experimental methods for modeling of condensation inside the emergency condenser and on the containment cooling condenser. This second part deals with boiling and two-phase flow instabilities. [less ▲]

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See detailModelling of Passive Heat Removal Systems: A Review with Reference to the Framatome KERENA BWR Reactor: Part I
Moonesi Shabestary, Amirhossein; Viereckl, Frances; Zhang, Yu et al

in Energies (2019)

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventionsand are solely driven ... [more ▼]

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventionsand are solely driven by thermal gradients and gravitational force. This brings up new needs forperformance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modelling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I deals with numerical and experimental methods for modelling of condensation inside the emergency condensers and on the containment cooling condenser while part II deals with boiling and two-phase flow instabilities. [less ▲]

Detailed reference viewed: 75 (8 UL)
See detailPANAS- Project: Heat Transfer Model Development for Passive Safety Systems,
Leyer, Stephan UL; Hampel; Schuster, C et al

in NURETH-18 (2019, August 18)

Detailed reference viewed: 70 (6 UL)
See detailLuxCube the First CubeSat Student Satellite in Luxembourg
Rabbadan Santana, E; Weiss, T; Djordjevic, A et al

Poster (2019, June 15)

Detailed reference viewed: 42 (1 UL)
See detailEvaluation of Stratified Condensation Models for a slightly inclined tube unsing ATHELT Code
Zhang, Yu; Moonesi Shabestary, Amir Hossein; Bieberle, Andre et al

in NURETH-18 (2019)

Detailed reference viewed: 86 (12 UL)
See detailInvestigation of Thermal Coupling in Condensation Process at COSMEA Facility with ATHLET Code
Zhang, Yu; Leyer, Stephan UL; Hampel, U

in Reactor engineering (2018, October)

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See detailAn investigation of condensation process at COSMEA test facility with ATHLET code
Zhang, Yu UL; Geißler, Thomas; Leyer, Stephan UL et al

in Kerntechnik (2018), 83(3), 208-214

Safety is an essential topic in the development process of nuclear power plant. Several Generation III and III+ reactor designs contain passive safety system to control accident without external power. An ... [more ▼]

Safety is an essential topic in the development process of nuclear power plant. Several Generation III and III+ reactor designs contain passive safety system to control accident without external power. An example is the Emergency Condenser (EC) of the KERENA reactor design. The EC removes heat from the Reactor Pressure Vessel in the case of design accidents. The experimental facility COSMEA at Helmhotz Zentrum Dresden Rossendorf (HZDR) was set up to investigate the flow morphology and heat transfer structure of condensation inside a slightly inclined tube. In this paper, the condensation process in COSMEA was simulated with the thermal hydraulic system codes ATHLET. The performance of the ATHLET heat transfer models were identified. The simulation results were compared against the experiments. The heat flux, condensation rate and temperature of cooling water during the condensation was analyzed. [less ▲]

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Peer Reviewed
See detailCFD Simulations of Adiabatic Boiling in Different Riser Geometries
Haag, M; Leyer, Stephan UL

Poster (2018)

Detailed reference viewed: 65 (4 UL)
See detailSimulation of condensation in a inclined tube with ATHLET code
Zhang, Yu UL; Leyer, Stephan UL

Presentation (2017, September 13)

Detailed reference viewed: 66 (2 UL)
Peer Reviewed
See detailSIMULATION OF CONDENSATION IN A SLIGHTLY INCLINED TUBE AT COSMEA FACILITY WITH ATHLET CODE
Zhang, Yu UL; Geißler, Thomas; Leyer, Stephan UL et al

Scientific Conference (2017, September 06)

Safety is an essential topic in the development process of nuclear power plant. Several Generation III reactor designs contain passive safety system to control accident without the need for external power ... [more ▼]

Safety is an essential topic in the development process of nuclear power plant. Several Generation III reactor designs contain passive safety system to control accident without the need for external power supply. An example for such passive systems is the Emergency Condenser (EC) of the KERENA reactor design. The system removes heat from the Reactor Pressure Vessel in the case of design basis accidents. The experimental facility COSMEA at Helmhotz Zentrum Dresden Rossendorf (HZDR) was set up to investigate the flow morphology and heat transfer structure of condensation processes. The test rig consists of a 3 m long condenser pipe which is 0.76° inclined with inner diameter 43.3 mm. On the shell side active cooling is performed using the TOPFLOW facility infrastructure. According to the Emergency Condenser Reference design, the experiments of COSMEA are conducted in different pressure levels (5, 15, 25, 45 and 65 bar) with steam mass flow rates up to 1 kg/s. An inlet mixing system was developed to operate the experiment in a stepwise method due to the scale of the test rig. Condensation rates, pressure, temperature and flow rate for different steam fraction are measured. In addition, an x-ray tomography is installed to study the details of the resulting stratified flow structures. Extra heat flux probes are assembled to detect the azimuthal distribution of the heat flux. In this work, COSMEA was simulated the thermal hydraulic system codes ATHLET. The performance of the ATHLET heat transfer models were identified. Primarily, the steady-state model was developed and the simulation results were compared to the experiment. The thermal coupling which considers the heat exchange between outside and inside of the pipe during the condensation was analyzed. Posteriorly the case of modeling transient condensation process was simulated. The influence on thermal coupling parameters, particularly heat transfer coefficient due to pressure drop inside the pipe was predicted and the feasibility and limitation of the system codes were evaluated. [less ▲]

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See detailDimensionshomogenität: Erkenntnis ohne Wissen?
Unger, Jochem; Leyer, Stephan UL

Book published by Springer-Verlag (2015)

Detailed reference viewed: 129 (4 UL)
See detailNaturkonstanten
Unger, Jochem; Leyer, Stephan UL

in Dimensionshomogenität (2015)

Detailed reference viewed: 68 (3 UL)
See detailEffizienz der Pi Theorem Methodik
Unger, Jochem; Leyer, Stephan UL

in Dimensionshomogenität (2015)

Detailed reference viewed: 66 (2 UL)
See detailAllometrie
Unger, Jochem; Leyer, Stephan UL

in Dimensionshomogenität (2015)

Detailed reference viewed: 48 (3 UL)