References of "Lemort, Vincent"
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See detailCharge-sensitive modelling of organic Rankine cycle power systems for off-design performance simulation
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Guillaume, Ludovic ULiege et al

in Applied Energy (2018), 212

This paper focuses on a charge-sensitive model to characterize the off-design performance of low-capacity organic Rankine cycle (ORC) power systems. The goal is to develop a reliable steady-state model ... [more ▼]

This paper focuses on a charge-sensitive model to characterize the off-design performance of low-capacity organic Rankine cycle (ORC) power systems. The goal is to develop a reliable steady-state model that only uses the system boundary conditions (i.e. the supply heat source/heat sink conditions, the mechanical components rotational speeds, the ambient temperature and the total charge of working fluid) in order to predict the ORC performance. To this end, sub-models are developed to simulate each component and they are assembled to model the entire closed-loop system. A dedicated solver architecture is proposed to ensure high-robustness for charge-sensitive simulations. This work emphasizes the complexity of the heat exchangers modelling. It demonstrates how state-of-the-art correlations may be used to identify the convective heat transfer coefficients and how the modelling of the charge helps to assess their reliability. In order to compute the fluid density in two-phase conditions, five different void fraction models are investigated. A 2 kWe unit is used as case study and the charge-sensitive ORC model is validated by comparison to experimental measurements. Using this ORC model, the mean percent errors related to the thermal power predictions in the heat exchangers are lower than 2%. Regarding the mechanical powers in the pump/expander and the net thermal efficiency of the system, these errors are lower than 11.5% and 11.6%, respectively. [less ▲]

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See detailExperimental investigation of a multi-evaporator refrigerator for both cabin cooling and battery thermal management
Gillet, Thomas; Andres, Emmanuelle; El-Bakkali, Amin et al

Conference (2018, February 01)

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See detailDesigning an air-to-air heat exchanger dedicated to single room ventilation with heat recovery
Gendebien, Samuel ULiege; Martens, Jonathan; Prieels, Luc et al

in Building Simulation: An International Journal (2018), 11(1), 103-113

The present paper focuses on the development steps of heat exchangers dedicated to single room ventilation unit with heat recovery (SRVHR) by proposing a numerical approach. A methodology is suggested in ... [more ▼]

The present paper focuses on the development steps of heat exchangers dedicated to single room ventilation unit with heat recovery (SRVHR) by proposing a numerical approach. A methodology is suggested in order to determine the best trade-off between hydraulic and thermal performance given a specific geometry. The methodology consists in a mapping of the coefficient of performance (COP) of the unit. The latter is defined as the ratio between recovered heat and the fan energy use, given a specific indoor/outdoor temperature difference. However, the energy performance should not be the only criterion to be taken into account in the frame of the design steps of a heat recovery exchanger: technical, economic and acoustic aspects should also be considered. This numerical methodology is illustrated by means of a real example of a newly developed heat exchanger dedicated to a SRVHR. The optimization is first performed while using a semi-empirical model (based on the use of correlations and on a spatial division of the studied heat exchanger). The semi-empirical model allows for the creation of a COP map in order to identify the most effective geometry parameters for the heat exchanger. The decision concerning the final geometry is made accounting for the so-called technical, economic and acoustic considerations. A discussion on some parameters needed for the COP establishment is also proposed. [less ▲]

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See detailTechnical and economic optimization of subcritical, wet expansion and transcritical Organic Rankine Cycle (ORC) systems coupled with a biogas power plant
Dumont, Olivier ULiege; Dickes, Rémi ULiege; De Rosa, M. et al

in Energy Conversion and Management (2018), 157

Generally, >40% of the useful energy (cooling engine and exhaust gases) are wasted by a biogas power plant through the cooling radiator and the exhaust gases. An efficient way to convert this waste heat ... [more ▼]

Generally, >40% of the useful energy (cooling engine and exhaust gases) are wasted by a biogas power plant through the cooling radiator and the exhaust gases. An efficient way to convert this waste heat into work and eventually electricity is the use of an organic Rankine cycle (ORC) power system. Over the last few years, different architectures have been widely investigated (subcritical, wet expansion and trans-critical). Despite the promising performances, realistic economic and technical constraints, also related to the application, are required for a meaningful comparison between ORC technologies and architectures. Starting from the limited literature available, the aim of the present paper is to provide a methodology to compare sub-critical, trans-critical and wet expansion cycles and different types of expanders (both volumetric and turbomachinery) from both technical and economic point of view, which represent one of the main novel aspects of the present work. In particular, the paper focuses on the thermo-economic optimization of an ORC waste heat recovery unit for a 500 kWe biogas power plant located in a detailed regional market, which was not investigated yet. By means of a genetic algorithm, the adopted methodology optimizes a given economic criteria (Pay-Back Period, Net Present Value, Profitability Index and Internal Rate of Return) while respecting technical constraints (expander limitations) and thermodynamic constraints (positive pinch points in heat exchangers, etc.). The results show that optimal ORC solutions with a potential of energy savings up to 600 MWh a year and with a pay-back period lower than 3 years are achievable in the regional market analysed. © 2017 Elsevier Ltd [less ▲]

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See detailPerformance correlations for characterizing the optimal off-design operation of an ORC power system
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Quoilin, Sylvain ULiege et al

in Energy Procedia (2017), 129

The goal of this work is to develop a set of simple correlations in order to characterize the optimal off-design performance of an ORC power system. To this end, a 2kWe ORC test rig is investigated as ... [more ▼]

The goal of this work is to develop a set of simple correlations in order to characterize the optimal off-design performance of an ORC power system. To this end, a 2kWe ORC test rig is investigated as case study and a validated off-design model is used to assess the highest net power generation achievable by the system over its complete range of operating conditions. The off-design model employed is charge-sensitive (i.e. it imposes the total mass of refrigerant in the system) which permits to predict the ORC state (i.e. its pressures, temperatures, mass flow rates, subcooling, etc.) based on the system boundary conditions only. Since such modelling approach and optimization process are time-consuming, a set of simple analytical equations is developed so as to easily predict the optimal performance of the ORC systems. [less ▲]

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See detailEffects of void fraction and heat transfer correlations in a charge-sensitive ORC model – a comparison with experimental data
Dickes, Rémi ULiege; Guillaume, Ludovic ULiege; Dumont, Olivier ULiege et al

in Proceedings of ECOS 2017 (2017, July 02)

In order to properly evaluate the off-design performance of an ORC unit, it is important to use simulation tools that minimize the number of assumptions regarding the system state. To avoid imposing the ... [more ▼]

In order to properly evaluate the off-design performance of an ORC unit, it is important to use simulation tools that minimize the number of assumptions regarding the system state. To avoid imposing the condenser subcooling (or any other equivalent state variable), the ORC model should account for the mass repartition of working fluid through the unit in function of the operating conditions. Among the various components constituting ORC power systems, the proper modelling of the mass of working fluid enclosed in the heat exchangers is of primary importance. The goal of this work is to develop such a reliable charge-sensitive ORC model. To this end, a 2kWe recuperative ORC system is used as case study and experimental measurements are used as reference dataset. The ORC system features two brazed plate heat exchangers and one fin coil condenser. For these three heat exchangers, a large set of empirical correlations is investigated in order to evaluate both the fluids void fractions and their convective heat transfer coefficients. By comparing the models predictions with the experimental data, the study highlights the limitations of existing correlations and investigates three different correction methods to improve them. Ultimately, the analysis compares nine models of brazed plate heat exchangers, two models of condenser, three correction methods for improving the heat transfer correlations and four void fraction methods. Accounting for every combination possible, 288 different models of the ORC are compared for predicting both the heat exchangers thermal performance and the total mass enclosed in the ORC unit. Out of this study, the best modelling approach is identified and details of its charge inventory predictions are presented. [less ▲]

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See detailComparison of a dynamic model and experimental results of a residential heat pump with vapor injection and variable speed scroll compressor
Dechesne, Bertrand ULiege; Gendebien, Samuel ULiege; Lemort, Vincent ULiege et al

in PROCEEDINGS OF ECOS 2017 (2017, July)

The first part of this paper presents a Modelica-based dynamic model of the system. Finite-volume models are used for the heat exchangers and the evaporator model takes into account frost formation. A ... [more ▼]

The first part of this paper presents a Modelica-based dynamic model of the system. Finite-volume models are used for the heat exchangers and the evaporator model takes into account frost formation. A thermodynamic model of the vapor injection scroll compressor is developed using empirical correlations for the volumetric efficiency, isentropic efficiency and the ratio between the injection and suction mass flow rate. The second part presents experimental results of a vapor injection and variable speed scroll compressor air to water residential heat pump. The unit is a 10kW residential system working with R410a as working fluid and capable of providing floor heating and domestic hot water. It was tested in a controlled environment in order to achieve a wide range of outdoor, including frosting conditions, and indoor conditions. The model predictions and experimental results are compared in order to validate the component models in steady state. The experimental investigations showed that there is room for improvement on the control side of the system and the developed model can be used in order to develop model based control of the injection and outdoor electronic expansion valves. [less ▲]

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See detailImpact of Diesel generator limitations in the robust sizing of isolated hybrid Microgrids including PV and batteries
Balderrama Subieta, Sergio Luis ULiege; Canedo, Walter; Lemort, Vincent ULiege et al

in Proceedings of ECOS 2016 - the 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (2017, July)

The recent developments in PV and Lion-ion batteries along with the maturity of gensets technology to provide energy to isolated systems has fostered the use of hybrid micro-grids for rural ... [more ▼]

The recent developments in PV and Lion-ion batteries along with the maturity of gensets technology to provide energy to isolated systems has fostered the use of hybrid micro-grids for rural electrification. In this context, the optimal coupling of different technologies and the minimization of the cost to the final consumer are the objects of a number of previous researches. However, the approach usually relies on deterministic linear programming optimizations (LP), which do not allow to model certain non-linearities and limitations of the components. This paper aims at filling this gap by proposing an optimization of such system, with a detailed representation of each component. The case study of an isolated village (Las Misiones, Bolivia) with a peak electricity consumption of 9.2 MW is analyzed. The considered system comprises a diesel generator; a PV array and Li-Ion batteries whose nominal capacities should be optimized. A robust optimization tool is first proposed with an LP formulation and the net present cost as objective function. The basic model is then modified to take into account more complex operating characteristics of a gen-set operating in part-load. To that aim, the LP problem is changed into a mixed integer linear programing formulation. Results indicate that the more detailed constraints influence the final design of the system and negatively impact the total cost. [less ▲]

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See detailAggregation of flexible domestic heat pumps for the provision of reserve in power systems
Georges, Emeline ULiege; Quoilin, Sylvain ULiege; Mathieu, Sébastien ULiege et al

in Proceedings of the 30th International Conference on Efficiency, Cost, Optimisation, Simulation and Environmental Impact of Energy Systems. (2017, July)

The integration of renewable energy sources in the electricity production mix has an important impact on the management of the electricity grid, due to their intermittency. In particular, there is a ... [more ▼]

The integration of renewable energy sources in the electricity production mix has an important impact on the management of the electricity grid, due to their intermittency. In particular, there is a rising need for flexibility, both on the supply and demand sides. This paper assesses the amount of flexibility that could be reserved from a set of flexible residential heat pumps in a given geographical area. It addresses the problem of a load aggregator controlling a set of heat pumps used to provide both space-heating and domestic hot water. The flexibility of the heat pumps is unlocked in order to reduce electricity procurement costs in the day-ahead electricity market, while ensuring the provision of a predefined amount of reserve for real-time grid management. The objective of the paper is two-fold. On the one hand, an aggregation method of large sets of heat pumps based on physics-based models and random sampling techniques is proposed. On the other hand, a combined optimization problem is formulated to determine both the optimal electricity demand profile to be bought on the day-ahead market and the cost associated to the reservation of a defined amount of power. The method is applied to a set of 40000 residential heat pumps in Belgian houses. Results show that these houses can provide up to 100MW of upward reserve for 50% of the current costs. The provision of downward reserve at competitive cost is hampered by significant overconsumption. [less ▲]

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See detailDevelopment of an Ericsson Heat Engine for biomass Combined Heat and Power
Oudkerk, Jean-François ULiege; Lemort, Vincent ULiege

in Proceedings of the 30th International conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS) (2017, July)

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See detailDesign and experimental validation of an adaptive control law to maximize power generation of a small-scale waste heat recovery system
Hernandez Naranjo, Jairo Andrés ULiege; Desideri, Adriano ULiege; Gusev, Sergei et al

in Applied Energy (2017), 203

Increasing the energy efficiency of industrial processes is a challenge that involves, not only improving the methodologies for design and manufacturing, but optimizing performance during part-load ... [more ▼]

Increasing the energy efficiency of industrial processes is a challenge that involves, not only improving the methodologies for design and manufacturing, but optimizing performance during part-load operation and transient conditions. A well-adopted solution consists of developing waste heat recovery (WHR) systems based on Organic Rankine Cycle (ORC) power units. The highest efficiency for such cycle is obtained at low superheating values, corresponding to the situation where the system exhibits time-varying nonlinear dynamics, triggered by the fluctuating nature of the waste heat source. In this paper, an adaptive control law using the Model Predictive Control (MPC) framework is proposed. This work goes a step beyond most of the existing scientific works in the field of ORC power systems, since the MPC controller is implemented in a lab-scale prototype, and its performance compared against a gain-scheduled PID strategy. The experimental results show that the adaptive MPC outperforms the gain-scheduled PID based strategy, as it allows to accurately regulate the evaporating temperature, while keeping vapor condition at the inlet of the expander i.e., the superheating, in a safe operating range, thus increasing the net power generation. [less ▲]

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See detailWaste Heat Recovery by Means of Organic Rankine Cycle (ORC) System Coupled with Two-Phase Closed Thermosyphons
Le, Van Long ULiege; Declaye, Sébastien ULiege; Dumas, Xavier et al

in International Journal of Thermodynamics (2017)

This paper aims at assessing the performance of a waste heat-to-power plant by means of an ORC (Organic Rankine Cycle) system coupled with two-phase closed thermosyphons (or gravity-assisted heat pipes or ... [more ▼]

This paper aims at assessing the performance of a waste heat-to-power plant by means of an ORC (Organic Rankine Cycle) system coupled with two-phase closed thermosyphons (or gravity-assisted heat pipes or wickless heat pipes). The heat exchanger, made up of two-phase closed thermosyphons, is used for conveying heat from exhaust stream to ORC working fluid. In reality, a hot oil loop or a pressurized hot water loop or a saturated ste am loop or even a direct evaporator is often used to transfer heat from the heat source to the ORC system. However, installing a heat exchanger directly in the hot gas paths of ORC system evokes the concerns for the flammability and/or toxicity of organic working fluids especially when the heat source has a relatively high temperature. Also the use of an intermediate heat carrier loop such as thermal oil or saturated steam or pressurized water loop is costly and involves installation of comparatively heavy components. In principle, the use of two-phase closed thermosyphons for capturing and transporting heat from a waste heat source to organic working fluid is less expensive than utilizing an intermediate heat transfer loop and eliminates safety issues as in the case of direct installation of an ORC evaporator in the hot gas paths. [less ▲]

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See detailPERFORMANCES D’UNE MINI POMPE À CHALEUR RÉVERSIBLE FONCTIONNANT SUR L’AIR EXTRAIT : ÉTUDE NUMERIQUE ET EXPERIMENTALE
Ransy, Frédéric ULiege; Gendebien, Samuel ULiege; Lemort, Vincent ULiege

Poster (2017, May 22)

La majeure partie de la consommation d’énergie des immeubles à appartement dits « basse énergie » est liée à la production d’eau chaude sanitaire et aux pertes par ventilation. De plus, ces immeubles sont ... [more ▼]

La majeure partie de la consommation d’énergie des immeubles à appartement dits « basse énergie » est liée à la production d’eau chaude sanitaire et aux pertes par ventilation. De plus, ces immeubles sont soumis à un risque de surchauffe non négligeable en été. Afin de minimiser leur consommation d’énergie, les systèmes HVAC utilisés dans ces bâtiments se doivent d’être performants et multitâches. Dans cette optique, l’Université de Liège teste actuellement une mini-pompe à chaleur réversible sur air extrait. Cet article présente les résultats expérimentaux obtenus en laboratoire et démontre quelles sont les variables qui influencent les performances de cette machine. Un modèle polynomial est également proposé. [less ▲]

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See detailDEVELOPPEMENT D’UN MODELE DE SYSTEME DE CLIMATISATION AUTOMOBILE MULTI-EVAPORATEURS
Gillet, Thomas ULiege; Gendebien, Samuel ULiege; Lemort, Vincent ULiege et al

Conference (2017, May 22)

La modélisation numérique d’un climatiseur d’automobile multi-évaporateurs, composé de deux évaporateurs et d’un refroidisseur d’eau, a été réalisée à l’aide du logiciel LMS Imagine.Lab Amesim® 1D avec le ... [more ▼]

La modélisation numérique d’un climatiseur d’automobile multi-évaporateurs, composé de deux évaporateurs et d’un refroidisseur d’eau, a été réalisée à l’aide du logiciel LMS Imagine.Lab Amesim® 1D avec le fluide frigorigène R-134a. Un banc d’essai capable de reproduire les conditions extérieures d’un climatiseur automobile a été conçu afin de tester l’architecture de cette machine multi-évaporateurs avec le fluide frigorigène R-1234yf. Les bilans thermiques des premiers résultats expérimentaux sont analysés et présentés. Afin d’illustrer la complexité du contrôle d’une telle architecture en régime dynamique, l’activation d’une vanne électromagnétique dans la boucle batterie du banc d’essais est présentée. Enfin, une perturbation de type échelon a été générée dans le modèle numérique afin de vérifier si les phénomènes transitoires observés expérimentalement sont reproduits. [less ▲]

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See detailExperimental investigation and dynamic modeling of an air-to-water residential heat pump with vapor injection and variable speed scroll compressor
Dechesne, Bertrand ULiege; Gendebien, Samuel ULiege; Lemort, Vincent ULiege et al

in 12th IEA Heat Pump Conference Proceedings (2017, May)

This paper presents experimental results of a residential air source heat pump using a scroll compressor with variable speed and vapor injection. The system is modeled using the Modelica language and a ... [more ▼]

This paper presents experimental results of a residential air source heat pump using a scroll compressor with variable speed and vapor injection. The system is modeled using the Modelica language and a comparison with the experimental results is performed. It was shown that there is still room for improvement on the control of the system. In fact, the tested gain scheduled PID controller showed limitation to maintain a low and steady superheat on both the suction and injection lines due to dynamics associated to the vapor split line or heat exchangers. The presented model of the system could be used in order to develop model based control and increase the system performances. [less ▲]

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See detailEtude expérimentale et numérique d'un échangeur destiné à la récupération de chaleur fatale sur bancs d'essais de moteurs aéronautiques
Gendebien, Samuel ULiege; Guillaume, Ludovic ULiege; Bellolio Domke, Sebastian Andres ULiege et al

in Colloque Inter-universitaire Franco-Québécois (CIFQ 2017), 22-24 mai 2017, Saint-Lô, France (2017, May)

Aujourd’hui, d’importants efforts sont réalisés dans divers secteurs afin de diminuer la consommation en énergie. En ce qui concerne le secteur aéronautique, de nombreux tests sont réalisés sur les ... [more ▼]

Aujourd’hui, d’importants efforts sont réalisés dans divers secteurs afin de diminuer la consommation en énergie. En ce qui concerne le secteur aéronautique, de nombreux tests sont réalisés sur les moteurs afin d’assurer la sécurité du transport aérien. Dans ce contexte, il a été envisagé de récupérer, recycler et valoriser l’énergie produite par le moteur au moyen d’un échangeur placé dans la cheminée d’évacuation des gaz. Pour ce faire, un prototype de modèle réduit d’échangeur récupératif sur gaz de combustion (gaz/eau ou gaz/huile) a été conçu, fabriqué et testé. Ce papier présente les caractéristiques du modèle réduit de l’échangeur développé spécifiquement pour cette application. L’ensemble du banc d’essais et le système de mesure mis en place afin de caractériser les performances de l’échangeur sont décrits. Une analyse des résultats expérimentaux est présentée. Les tests sont notamment divisés en deux parties : établissement des performances en régime monophasique et diphasique. Notons également que les performances hydrauliques de l’échangeur ont été expérimentalement déterminées. Un modèle numérique de type semi-empirique est proposé pour prédire les performances de l’échangeur. Ce dernier nécessite un calibrage des paramètres au moyen des données expérimentales afin de prédire les performances de l’échangeur sous une grande plage de conditions opératoires. Une comparaison entre résultats numériques et expérimentaux est finalement présentée. [less ▲]

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See detailMODELISATION D’UN ECHANGEUR A THERMOSIPHONS POUR LA RECUPERATION DE CHALEUR
Le, Van Long ULiege; Dumas, Xavier; Ferrand, Ludovic et al

in XIIIème Colloque Interuniversitaire Franco-Québécois sur la Thermique des Systèmes (2017, May)

Le présent travail a pour objectif de modéliser un échangeur à thermosiphons diphasiques pour transporter la chaleur d’un effluent gazeux (c.à.d. gaz de combustion) à haute température (720°C) au système ... [more ▼]

Le présent travail a pour objectif de modéliser un échangeur à thermosiphons diphasiques pour transporter la chaleur d’un effluent gazeux (c.à.d. gaz de combustion) à haute température (720°C) au système ORC (cycle organique de Rankine). Les thermosiphons sont placés dans les gaz de combustion et refroidis par le fluide de travail du système ORC (le Cyclopentane pour le cas actuel). Le débit massique des fumées et la puissance thermique de l’échangeur sont respectivement imposés de 21 kg/s et de 4.022 MWth. Le fluide organique s’évapore à une température de 200°C et quitte l’évaporateur sans surchauffe (vapeur saturée). Le modèle de simulation développé dans le logiciel EES (Engineering Equation Solver) est capable de déterminer le nombre nécessaiare de thermosiphons. L’influence des pas transversaux et longitudinaux de l’échangeur sur le nombre de thermosiphons et la perte de charge des fumées est également examinée pour les dispositions quinconces et alignées des tubes de thermosiphons. [less ▲]

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See detailModelling of organic Rankine cycle power systems in off-design conditions: an experimentally-validated comparative study
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Daccord, Rémi et al

in Energy (2017), 123

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development ... [more ▼]

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development, power generation from low-grade heat sources is gaining interest and the organic Rankine cycle (ORC) is seen as one of the most promising technologies for such applications. In this paper, it is proposed to perform an experimentally-validated comparison of different modelling methods for the off-design simulation of ORC-based power systems. To this end, three types of modelling paradigms (namely a constant-efficiency method, a polynomial-based method and a semi-empirical method) are compared both in terms of their fitting and extrapolation capabilities. Post-processed measurements gathered on two experimental ORC facilities are used as reference for the models calibration and evaluation. The study is first applied at a component level (i.e. each component is analysed individually) and then extended to the characterization of the entire organic Rankine cycle power systems. Benefits and limi- tations of each modelling method are discussed. The results show that semi-empirical models are the most reliable for simulating the off-design working conditions of ORC systems, while constant-efficiency and polynomial-based models are both demonstrating lack of accuracy and/or robustness. [less ▲]

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See detailMulti-evaporator air-conditioning system
Gillet, Thomas ULiege; Lemort, Vincent ULiege; Andres, Emmanuelle et al

Conference (2017, February 14)

Regulation in terms of greenhouse gas emissions becomes more and more stringent and the fuel consumption targets decrease. In order to meet these demands, vehicle electrification has increased over the ... [more ▼]

Regulation in terms of greenhouse gas emissions becomes more and more stringent and the fuel consumption targets decrease. In order to meet these demands, vehicle electrification has increased over the last decade. With the arrival of plug-in hybrids and battery electric vehicles, efficient battery cooling system becomes a necessity and has to be integrated into the vehicle thermal management. One of the possibility is to integrate a chiller in the air conditioning system for extreme operating points. Moreover, this kind of system can be dedicated to luxury or large passenger cars for which a secondary evaporator is present to guarantee the comfort for rear passengers. The main challenge of this air-conditioning architecture is to maintain simultaneously the cabin thermal comfort via one or two evaporators on one hand and to maintain the battery cells in an ideal temperature range on the other hand. [less ▲]

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