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See detailAppendices of the ORC19 journal paper
Dumont, Olivier ULiege

Cartographic material (2019)

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See detailOnline Measurement Of The Working Fluid Mass Repartition In A Small-Scale Organic Rankine Cycle Power System
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Quoilin, Sylvain ULiege et al

in Proceedings of Purdue 2018 (2018, July 12)

This paper presents an experimental investigation of the working fluid charge repartition in a 2kWe ORC (organic Rankine cycle) test bench. To this end, an online measurement apparatus is built and fully ... [more ▼]

This paper presents an experimental investigation of the working fluid charge repartition in a 2kWe ORC (organic Rankine cycle) test bench. To this end, an online measurement apparatus is built and fully calibrated to evaluate the charge enclosed in the three heat exchangers and the liquid receiver of the ORC unit. By changing all the system boundary conditions (including the charge enclosed in the test rig), an experimental database of 304 steady-state points is gathered and post-treated. The charge inventories obtained by online measurements demonstrate promising results on average but experience high uncertainties when considering each point individually (i.e. the uncertainty on the global inventory is around ± 2.5 kg for a total charge of 31.2 kg). Deviations of the evaporator mass measurements are identified at high temperature of the heat source and discussed in details. A reconciliation method is applied to the raw measurements in order to retrieve consistent charge inventories while accounting for the different sources of uncertainty. Ultimately, the paper analyses the impact of increasing the charge in the ORC and how this parameter influences the thermodynamic state of the system. [less ▲]

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See detailExperimental and numerical investigation of a roots expander integrated into an ORC power system
Parthoens, Antoine ULiege; Guillaume, Ludovic ULiege; Dumont, Olivier ULiege et al

in Proceedings of Purdue 2018 (2018, July)

The performance of internal combustion engines can be improved by valorising the waste heat by means of organic Rankine Cycle power systems (ORC). This paper focuses on an expander of a truck-embedded ORC ... [more ▼]

The performance of internal combustion engines can be improved by valorising the waste heat by means of organic Rankine Cycle power systems (ORC). This paper focuses on an expander of a truck-embedded ORC system. The considered expander is a roots machine. The roots machine is a volumetric machine characterized by a theoretical internal volume ratio of 1. It is typically used as compressor under low pressure ratios (for instance, engine supercharging or air “blowers”). First, a test rig has been built to perform several tests on the volumetric machine. It is an ORC power system with a typical architecture using R245fa as working fluid (and 5% in mass oil fraction), heated oil as heat source and tap water as heat sink. Maps presenting produced powers, filling factors and isentropic efficiencies versus on one side the pressure ratio (from 1.2 to 4.5) and on the other side the shaft rotational speed (from 1000 to 11000 RPM) are investigated. The maximal delivered power is slightly above 3 kW. Concerning the filling factor the range is between 0.85 and 2.75 and the isentropic efficiency reaches a maximum about 50%. Wet expansions are envisaged leading to a deterioration of the performance. From the experimental data, a semi-empirical model is calibrated. This model is able to extrapolate the performance outside the experimental operating conditions and identify the different loss sources. Moreover, effects of overheat level and lubricating oil are also envisaged. The actual tested machine does not have an internal volumetric ratio strictly equal to 1 but is slightly larger. Such volumetric ratio implies that best efficiencies are achieved under small pressure ratios. However, these limited pressure ratios do not lead to large produced powers. To tackle this issue, simulations based on the calibrated model are driven for two expanders in series. This allows to increase the global internal volumetric ratio and shift the best performance towards higher pressure ratios. To enhance either the efficiency or the output power, the intermediate pressure (i.e. the pressure between the two expanders in series) is numerically optimized. [less ▲]

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See detailExperimental performance of a field of parabolic trough collectors for small-scale power generation
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Thiebaut, Jérémie et al

in Proceedins of ECOS 2018 (2018, June 23)

The present work investigates the solar field performance of a pilot system installed at the University of Liège in Belgium. The system includes eight parabolic trough collectors connected in series (66m² ... [more ▼]

The present work investigates the solar field performance of a pilot system installed at the University of Liège in Belgium. The system includes eight parabolic trough collectors connected in series (66m² in total) and is aimed for small-scale power generation (2kWe) at low-temperature operation (150°C max.). The paper describes the test facility and presents experimental data gathered under various operating conditions. After posttreatment, the measurements are used to calibrate a deterministic model of the solar collectors. This model is used to better estimate the various sources of losses during the solar energy conversion and to investigate potential means of performance improvements. While the collection efficiency recorded experimentally does not exceed 30%, it is shown that an improvement of the tracking could raise this value to 65% and thus meet the design expectations. [less ▲]

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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 and optimal performance assessment of four volumetric expanders (scroll, screw, piston and roots) tested in a small-scale organic Rankine cycle system
Dumont, Olivier ULiege; Parthoens, Antoine ULiege; Dickes, Rémi ULiege et al

in Energy (2018)

The aim of this paper is to facilitate the selection of the expander for a small-scale organic Rankine cyclebased on an experimental comparison of a piston, a screw, a scroll and a roots expander. First ... [more ▼]

The aim of this paper is to facilitate the selection of the expander for a small-scale organic Rankine cyclebased on an experimental comparison of a piston, a screw, a scroll and a roots expander. First, based on aliterature review, a comparison between these four technologies of volumetric expansion machines isperformed. Afterward, four displacement expanders [2e4 kW] are tested on two similar small-scale ORCunit withfluid R245fa. The maximum effective isentropic efficiencies measured are 53% for the pistonexpander and the screw expander, 76% for the variable-speed scroll and 48% for the roots machine.However, these performances do not reflect the highest efficiencies achievable by each expander: thetest-rig presents experimental limitations in terms of massflow rate and pressure drop (among others)that restricts the achievable operating conditions. The calibration of semi-empirical models based on themeasurements allows to overcome this issue and to predict the isentropic efficiency in optimal condi-tions despite the limitations of the test-rigs. Based on experimental results, extrapolated prediction ofthe semi-empirical model and practical considerations, some guidelines are drawn to help the reader toselect properly a volumetric expander. [less ▲]

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See detailInnovative architecture to valorize the waste heat of a passenger car through the use of a Rankine cycle
Dumont, Olivier ULiege; Diny, Mouad; Lemort, Vincent ULiege et al

in Proceedings of purdue conference 2018 (2018)

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See detailExperimental investigation and modelling of a 1.5 kW axial turbine designed for waste heat recovery through a Rankine cycle
Dumont, Olivier ULiege; Diny, Mouad; Lemort, Vincent ULiege

in SAE International Journal of Passenger Cars - Mechanical Systems (2018)

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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 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 detailDesign optimization of Rankine cycle systems for waste heat recovery from passenger car engines
Lemort, Vincent ULiege; Legros, Arnaud; Dumont, Olivier ULiege et al

Conference (2017, February 07)

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See detailInvestigation of a heat pump reversible in an organic Rankine cycle and its application in the building sector
Dumont, Olivier ULiege

Doctoral thesis (2017)

This thesis studies the concept of reversible heat pump / organic Rankine cycle (HP/ORC) and its application in the building sector. Chapter one describes this HP/ORC system and its possible applications ... [more ▼]

This thesis studies the concept of reversible heat pump / organic Rankine cycle (HP/ORC) and its application in the building sector. Chapter one describes this HP/ORC system and its possible applications. A tool based on operating maps is developed to determine the feasibility of such a system depending on the operating conditions of a given application. In Chapter two, the reversibility of volumetric machines is studied based on a theoretical comparison followed by experimental results collected on four different compressor/expander technologies. The comparison shows which technology should be used depending on the characteristics of an application. In Chapter three, the design and sizing methodology to optimize the performance of the reversible heat pump /organic Rankine cycle is described. This design and sizing optimisation is performed in the case of the residential application: the reversible HP/ORC system is coupled with a large solar absorber in a building to provide a polyvalent machine able to produce heat or electricity depending on the needs of the building. Steady-state models are then used to predict the annual performance of the system integrated in a building. As the theoretical results are promising in the case of the residential application, a test-rig is built and an experimental campaign is performed in both HP and ORC modes (Chapter four). A global methodology to improve the quality of experimental data is proposed based on two different mathematical tools. The method combines the reconciliation method and the Gaussian Processes sensitivity analysis. A model is calibrated based on experimentation to characterize the performance of the HP/ORC unit with an optimal control and with a wide range of inputs. Chapter five studies the reversible unit in the case of the building application based on advanced dynamic models. The global model combines validated sub-models: the reversible unit, the solar roof, the thermal energy storage, the horizontal ground heat exchanger and the building. An optimal control strategy is developed and presented. A parametric study is performed to observe the performance of the system in a wide range of typologies. The influence of different lights and appliances profiles, building envelopes, integration of batteries, roof tilt angles, locations, storage sizes is developed. Furthermore, a technical and economic comparison with one of the most mature technologies to get a positive energy building, namely photovoltaics panels combined with a heat pump in a passive house, is performed. [less ▲]

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See detailExperimental investigation of four volumetric expanders
Dumont, Olivier ULiege; Dickes, Rémi ULiege; Lemort, Vincent ULiege

in Energy Procedia (2017)

Detailed reference viewed: 721 (10 ULiège)