References of "Lemort, Vincent"
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See detailSizing and Operation of an Isolated Microgrid with Cold Storage
Dakir, Selmane ULiege; Boukas, Ioannis ULiege; Lemort, Vincent ULiege et al

Scientific conference (2019, June)

Due to the technological developments and the advances of smart control, intermittent production from renewable energy sources can be better exploited locally in the context of a smart microgrid. Energy ... [more ▼]

Due to the technological developments and the advances of smart control, intermittent production from renewable energy sources can be better exploited locally in the context of a smart microgrid. Energy storage has a key role in achieving this task and batteries are the most suitable candidate. In this paper, a complementary solution is presented where excess electricity is used in a cold storage to produce ice which, when melting, supplies the cooling demand. A detailed model of each component is considered in order to simulate the operation of the entire system. The goal of this paper is the derivation of the optimal size of the different components to yield the minimum levelized cost of electricity. The methodology described is applied to a real case study in Marrakesh, and results illustrate that cold storage is able to reduce the total cost of energy in the context of an isolated microgrid. [less ▲]

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See detailInvestigation of a single room ventilation heat recovery exchanger under frosting conditions: Modeling, experimental validation and operating strategies evaluation
Gendebien, Samuel ULiege; Parthoens, Antoine ULiege; Lemort, Vincent ULiege

in Energy and Buildings (2019), 186

This paper tackles the issue of frost formation in air-to-air heat recovery devices dedicated to single room ventilation by means of both numerical simulations and experimental approaches. In such heat ... [more ▼]

This paper tackles the issue of frost formation in air-to-air heat recovery devices dedicated to single room ventilation by means of both numerical simulations and experimental approaches. In such heat exchangers, it is commonly known that the formation of a frost layer on the surface generates an additional thermal resistance and a flow section reduction, which leads to an overall degradation of the overall unit performance. This paper proposes a three-zone model, considering a dry, a wet and a frost zone, by determining the location of moving boundaries. Each zone is handled independently and the relative proportion of each zone is determined by means of the exchanger wall temperature. Besides this frost model, a defrost model is also envisaged. Once validated with experimental data collected on a U-flow-type heat exchanger, the developed model is used to implement different strategies to reduce or prevent frost formation in the exchanger. Based on three different criteria, these strategies are compared with each other to evaluate their benefits and drawbacks. The criteria give information on the energy efficiency of the ventilation, on the air renewal quality and on the pressure balance between the inside and the outside of the building. [less ▲]

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See detailInnovative thermal machines for waste heat recovery in industry
Lemort, Vincent ULiege

Scientific conference (2019, March)

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See detailGreenhouses: A Modelica Library for the Simulation of Greenhouse Climate and Energy Systems
Altés Buch, Queralt ULiege; Quoilin, Sylvain ULiege; Lemort, Vincent ULiege

in Proceedings of the 13th International Modelica Conference (2019, March)

This paper presents the results of an on-going project to develop Greenhouses, an open Modelica library for the simulation of greenhouse climate and energy systems. The Greenhouses library is one of the ... [more ▼]

This paper presents the results of an on-going project to develop Greenhouses, an open Modelica library for the simulation of greenhouse climate and energy systems. The Greenhouses library is one of the few open-source modeling frameworks for greenhouse climate and crop growth simulation, and the first able to handle simulating the energy integration of greenhouses coupled to thermal systems (e.g. generation and storage units). The proposed modeling framework can be used for multiple purposes, such as the optimal control of the greenhouse actuators, the optimal sizing of the heating appliances, or the optimal integration of the units in the power system. The Greenhouses library also comprises multiple example models, making it readily usable for both research and industrial applications. [less ▲]

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See detailOptimization of organic rankine cycle power systems for waste heat recovery on heavy-duty vehicles considering the performance, cost, mass and volume of the system
Imran, Muhammad; Haglind, Fredrik; Lemort, Vincent ULiege et al

in Energy (2019), 180

The use of organic Rankine cycle power systems for waste heat recovery on internal combustion engines of heavy-duty vehicles can help to mitigate the greenhouse gases and reduce the fuel consumption of ... [more ▼]

The use of organic Rankine cycle power systems for waste heat recovery on internal combustion engines of heavy-duty vehicles can help to mitigate the greenhouse gases and reduce the fuel consumption of the vehicle. However, designing an organic Rankine cycle system for this application is a complex process involving trade-offs among factors such as performance, space/weight restrictions, and cost. This paper presents a multi-objective optimization study of an organic Rankine cycle unit for waste heat recovery from heavy-duty vehicles from techno-economic and sizing perspectives. The optimization was carried out for seven different working fluids using the genetic algorithm to minimize the cost, volume and mass, and maximize the net power output of the organic Rankine cycle unit. The organic Rankine cycle performances for a driving cycle of a truck were also evaluated. The results indicate that the mass, volume, cost and net power output of the organic Rankine cycle system increase with the evaporation temperature. Moreover, the results suggest that when the condensation temperature was decreased from 60 °C to 40 °C, the net power, weight, cost and volume of the organic Rankine cycle unit increases by 22%, 12%, 46%, and 12% respectively. The maximum net power output, both at the design and off-design conditions, is obtained with pentane as working fluid. For this design, the net power output of the organic Rankine cycle unit is 10.94 kW at design condition and 8.3 kW at off-design (in average) condition, and the mass, volume, and cost of the organic Rankine cycle system are 129 kg, 1.077 m3, and 8527 €, respectively. [less ▲]

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See detailExperimental characterization of a reversible heat pump for hybrid and electric vehicles
Cuevas, Cristian; Declaye, Sébastien; Lemort, Vincent ULiege

in Advances in Mechanical Engineering (2019), 11(4),

The most performant system for heating in electric and hybrid vehicles is the heat pump. This study proposes a heating system with a reversible heat pump, which works as a conventional air conditioning ... [more ▼]

The most performant system for heating in electric and hybrid vehicles is the heat pump. This study proposes a heating system with a reversible heat pump, which works as a conventional air conditioning system in cooling mode and in heating mode it uses a secondary circuit with water/glycol to transfer the heat from the condenser to the heater core located in the air conditioning module. This system was experimentally validated with 61 tests in heating mode and 19 tests in cooling mode. In the heating mode, there is a test which was developed with an ambient temperature of -1ºC with the air circulating through the outdoor unit at a velocity of 3.2m /s , an air flow rate of 388 kg/h supplied to the cabin and the compressor running at 2866 r/min. At these conditions, the air is supplied to the cabin at 41.5ºC, the heating power is 4.2kW and the COP is 1.9. In the cooling mode, there are tests developed at a condenser supply air temperature of 45.4ºC with a velocity of 5.7m/s . The air is supplied to the vehicle cabin with a temperature of 14.6ºC with a flow rate of 508 kg/h , with a cooling capacity of 3.88 kW and a coefficient of performance of 1.8. [less ▲]

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See detailModeling framework for the simulation and control of greenhouse climate
Altés Buch, Queralt ULiege; Lemort, Vincent ULiege

in Proceedings of the 10th International Conference on System Simulation in Buildings (2018, December)

This work presents an open-source modeling framework for the purpose of greenhouse climate simulation. To that end, a greenhouse climate model and a crop yield model are implemented, based on the ... [more ▼]

This work presents an open-source modeling framework for the purpose of greenhouse climate simulation. To that end, a greenhouse climate model and a crop yield model are implemented, based on the literature. Moreover, climate control system models are developed for the control of heating, ventilation, CO2 enrichment and supplementary lighting. Climate controllers aim at maintaining an indoor climate that has been designed to optimize crop growth. In this work, the indoor climate is computed by the climate model and the crop growth is defined by the yield model. To establish optimal growth conditions, a strategy is defined to select optimal temperature and CO2 set-points. The models are written in the Modelica language, thus enabling to simulate their integration with other thermal systems. The use of the models is illustrated in a case study. To that end, the models are coupled and run for a simulation time period equivalent to a growing cycle for tomato crop in mild-climate conditions. Results for the thermal consumption of the greenhouse, the harvest rate of the crop are presented. The control variables and the indoor climate variables and flows are illustrated. The obtained results and profiles are in accordance with the literature, thus ensuring the physical behavior of the model and the proper functioning of the proposed control strategies. [less ▲]

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See detailSteady-state and dynamic validation of a parabolic trough collector model using the ThermoCycle Modelica library
Desideri, Adriano ULiege; Dickes, Rémi ULiege; Bonilla, Javier et al

in Solar Energy (2018), 174

Small-capacity (<200 kWel) concentrated solar power plants has been recognized as a promising technology for micro power applications. In particular, parabolic trough collectors have been identified as ... [more ▼]

Small-capacity (<200 kWel) concentrated solar power plants has been recognized as a promising technology for micro power applications. In particular, parabolic trough collectors have been identified as the most promising focusing technology. In this context, physics-based dynamic model of parabolic trough constitutes a significant tool for the further development of the technology, allowing to evaluate and optimize response times during transients, or to implement and test innovative control strategies. In this contribution, the dynamic model of a parabolic trough line based on the ThermoCycle Modelica library is validated against steady-state and transient experimental results from the parabolic trough test loop available at the Plataforma Solar de Almería, Spain. The simulation results are in good agreement with the measurements, both in steady-state and in transient conditions. The validated model is readily usable to investigate demanding dynamics-based problems for low capacity solar power systems. [less ▲]

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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 detailImpact of suction and injection gas superheat degrees on the performance of a residential heat pump with vapor injection and variable speed scroll compressor
Dechesne, Bertrand ULiege; Lemort, Vincent ULiege; Nadri, Madiha et al

in Proceedings of the 17th International Refrigeration and Air Conditioning Conference at Purdue (2018, July)

The first part of this paper focuses on the experimental results collected from a vapor injection and variable speed scroll compressor air-to-water residential heat pump. The unit is a 10 kW residential ... [more ▼]

The first part of this paper focuses on the experimental results collected from a vapor injection and variable speed scroll compressor air-to-water residential heat pump. The unit is a 10 kW residential system working with R410a and capable of providing floor heating and domestic hot water. It is tested in a controlled environment in order to achieve a wide range of outdoor and indoor conditions. The impact on the system performance of the vapor superheat degrees at both injection and suction ports is discussed. It is shown that a better control of these variables could improve the system COP and heating capacity by respectively 10 and 15%. It is also shown that the control of the superheat degrees is a coupled problem and the use of standard gain-scheduled (Single Input Single Output) SISO proportional–integral–derivative (PID) controllers is not optimal. The second part of this paper presents a multivariable decoupler-based proportional–integral (PI) controller using feedforward action in order to take into account the coupling between both superheat controls. System models are first presented, the first one is a MIMO (Multiple Input Multiple Output) first order transfer function based model in order to identify the decoupler and PI controller gains. The second one is a non-linear dynamic model of the injection line in order to first test the proposed controller in simulation. Finite-volume models are used for the heat exchangers and the split lines. 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 rates. Three adapted multivariable controllers are tested in simulation and compared to a baseline PI controller. All proposed controllers show increased performances compared to the SISO PI controller. [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 detailMulti-objective optimization of organic Rankine cycle power systems for waste heat recovery on heavy-duty vehicles
Imran, Muhammad; Haglind, Fredrik; Lemort, Vincent ULiege et al

in Proceedings of ECOS 2016 - the 31th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (2018, June)

The use of Organic Rankine Cycle (ORC) power systems for waste heat recovery on internal combustion engines of heavy-duty vehicles can help to mitigate the greenhouse gasses and reduce the fuel ... [more ▼]

The use of Organic Rankine Cycle (ORC) power systems for waste heat recovery on internal combustion engines of heavy-duty vehicles can help to mitigate the greenhouse gasses and reduce the fuel consumption of the truck. However, designing an ORC system for this application is a complex process involving trade-offs among factors such as the performance, space/weight restrictions, and cost. This paper presents a multi-objective optimization study of an organic Rankine cycle unit for waste heat recovery from heavy-duty vehicles from techno-economic and sizing perspectives. The optimization was carried out for seven different working fluids using the genetic algorithm to minimize the cost, volume and mass, and maximize the net power output of the ORC unit. The ORC performances for a driving cycle of a truck were also evaluated. In general, the results indicate that the mass, volume, cost and net power output of the ORC system increase with increase in evaporation temperature. The results suggest that when condensation temperature was decreased from 60°C to 40°C, the cost, volume, and weight of the ORC unit increased significantly. The maximum net power output, both at design and off-design conditions, is obtained with pentane as working fluid. For this design the net power output of the ORC unit is 10.94 kW at design condition and 8.3 kW at off-design (in average) condition, and the mass, volume, and cost of the ORC system are 129 kg, 1.077 m3, and 8527 €, respectively. [less ▲]

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See detailModeling and control of CHP generation for greenhouse cultivation including thermal energy storage
Altés Buch, Queralt ULiege; Quoilin, Sylvain ULiege; Lemort, Vincent ULiege

in Proceedings of ECOS 2018 - The 31st International Conference on Efficiency, Cost, Optimization, Simulation and environmental impact of energy systems (2018, June)

In recent decades, greenhouse energy consumption has been the object of a substantial literature. Attention has also been paid to the modeling of greenhouse climate simulation and energy sources to ... [more ▼]

In recent decades, greenhouse energy consumption has been the object of a substantial literature. Attention has also been paid to the modeling of greenhouse climate simulation and energy sources to evaluate energy saving options. However, such models are not readily available in the literature. The goal of this work is therefore to propose an open modeling framework capable of simulating the complex interactions and energy flows relative to such systems. A detailed dynamic model of a greenhouse describing the indoor climate and the heating system components was implemented. A dynamic tomato crop yield model was also implemented to account for the effects of the indoor climate on the harvested dry matter. The models are written in the Modelica language, are released open-source and are run within the Dymola simulation platform. The use of the proposed simulation platform is then illustrated for a particular case. The limited electrical load of greenhouses implies an excess of electricity generation when using CHP units, which have a power-to-heat ratio close to one. In this work, the addition of a heat pump is proposed to foster electrical self-consumption. A control strategy is designed to optimize the operational cost of the system. The system includes thermal energy storage, which acts as a buffer and allows minimizing the electricity sold back to the grid. Performance-based models for each generation unit and the storage unit are developed. Results show that the gas consumption was reduced by 25%. The heat pump generated 25% of the thermal load, the rest being generated by the CHP. Only 42% of the generated electricity is sold back to the grid, 57% being consumed by the heat pump. In conclusion, the heat pump and the thermal energy storage significantly improve the self-consumption level and thereby reduce the system operational cost by 9%. [less ▲]

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See detailDevelopment of multi-zone heat exchanger model under frost and defrost conditions
Parthoens, Antoine ULiege; Gendebien, Samuel ULiege; Lemort, Vincent ULiege

in Proceedings of ECOS 2018 (2018, June)

Global warming is now recognized by the major part of the scientific community. An important issue is the carbon dioxide emissions. The residential area is one major impacting sector, accounting for 30 ... [more ▼]

Global warming is now recognized by the major part of the scientific community. An important issue is the carbon dioxide emissions. The residential area is one major impacting sector, accounting for 30% of the final energy consumed (in Europe). A solution to reduce heat losses due to ventilation is single room ventilation with heat recovery. The objective of this paper is to present the development of a model for the design of a heat exchanger implemented in this kind of unit. The proposed modelling is a multi-zone model with a moving boundary. It allows to consider completely dry, partially wet or completely wet regimes on the stale air side. The boundary between the different zones is determined by means of the exchanger wall surface temperature. This model can be extended to frost conditions by adding a new “frost zone”. The formation of a frost layer on the surface generates an additional thermal resistance as well as a fouling inside ducts. Consequently, it reduces the flow section and the air flow rate for a given fan’s rotational speed. The frost quantity may increase until it blocks the passage ways for exhaust air and stops completely the airflow. The aim of this paper is to introduce the new multi-zone model taking into account the frost formation as well as defrost phase and predicting the impact on the hydraulic and thermal performance. This model is validated on the basis of some experiments done on an actual air-air heat exchanger under frost conditions. These experiments also reveals the limitations of the model. [less ▲]

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See detailPre-design of waste heat recovery ORC systems for heavy-duty trucks by means of dynamic simulation
Guillaume, Ludovic ULiege; Lemort, Vincent ULiege

Conference (2018, May 24)

Internal combustion engines (ICE) of heavy-duty trucks show efficiencies larger than 40% in nominal operating conditions. Despite these rather good efficiencies in comparison with smaller ICEs, a large ... [more ▼]

Internal combustion engines (ICE) of heavy-duty trucks show efficiencies larger than 40% in nominal operating conditions. Despite these rather good efficiencies in comparison with smaller ICEs, a large amount of heat is wasted to the ambient in the engine coolant circuit, in the exhaust gas and in the exhaust gas recirculation cooler. These different heat sources differ by their capacities and levels of temperatures. In order to meet the upcoming international CO2 regulations and in order to increase the competitiveness of transportation by trucks, truck industry is currently investigating the technical and economical feasibility of waste heat recovery by means of Organic Rankine Cycle heat engines. In this context, the present paper aims at comparing the energy and economical performance of different topologies of ORC on representative driving cycles. These topologies differ by the configuration of the different evaporators (EGR evaporator in parallel or in series with the exhaust gas evaporator), by the working fluids (R245fa, ethanol, acetone, cyclopentane and dimethylcarbonate) and by the expansion machines (volumetric expanders and radial inflow turbine). The choice of the investigated working fluids and expansion machines is justified by previous research projects whose results are summarized. Dynamic simulations are conducted with Amesim simulation tool. The control of the ORC is achieved by two different gain scheduling PIDs. Manipulated variables are the expander and pump rotational speeds and controlled variables are the expander supply pressure and temperature. The models of the components and the parameters identification process are described. Performance achieved with the different topologies are assessed in terms of fuel saving, power rejected at the condenser (which increases the cooling load of the truck) and payback time for the truck owner. Estimated fuel savings range from 2.3% to 3.2% and minimum payback time is 2 years. [less ▲]

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See detailWaste heat recovery (WHR) assessment in complete truck simulation environment
Galuppo, Francesco; Reiche, Thomas; Lemort, Vincent ULiege et al

in Proceedings of the 2018 SIA POWERTRAIN conference (2018, May)

Organic Rankine Cycle (ORC) based Waste Heat Recovery in long haul heavy duty (HD) trucks is a promising technology to reduce the fuel consumption. Despite several studies that have been conducted, such ... [more ▼]

Organic Rankine Cycle (ORC) based Waste Heat Recovery in long haul heavy duty (HD) trucks is a promising technology to reduce the fuel consumption. Despite several studies that have been conducted, such technology has not been introduced yet on the market. The constraints for a market introduction are related to driving cycle fuel efficiency, the integration of the WHR system in the truck, control of the system, material compatibility, weight and costs. This paper outlines the mentioned constraints and proposes a complete truck environment simulation study, considering interactions of the system with the other sub-systems of the truck. Control strategies and optimized Rankine energy utilisation are proposed to maximize the effectiveness of the system. [less ▲]

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See detailMODELING AND EXPERIMENTAL RESULTS OF A RESIDENTIAL HEAT PUMP WITH VAPOR INJECTION AND VARIABLE SPEED SCROLL COMPRESSOR
Dechesne, Bertrand ULiege; Lemort, Vincent ULiege

in Proceedings of the REHVA Annual Meeting Conference (2018, April 23)

The market share of heat pump systems has grown significantly in Europe in the past decades and, in residential applications, air-source heat pumps (ASHP) are usually considered due to their relatively ... [more ▼]

The market share of heat pump systems has grown significantly in Europe in the past decades and, in residential applications, air-source heat pumps (ASHP) are usually considered due to their relatively low cost. In the literature, it has been widely demonstrated that injection cycle can improve the system performance and operating range. This paper presents an experimental study and a compressor model of such a system. The first part of the paper focus on the experimental results collected from 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 and indoor conditions. The impact of the split lines and of the four-way valve on the superheat level is described. Finally, the impact on the system performance of the levels of superheat of both injection and suction ports is discussed. The second part of this paper presents a model of the variable speed compressor. 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 rates. Finally, the comparison between the compressor model predictions and results from a steady-state experimental campaign is given. [less ▲]

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See detailSleeping evaporator and refrigerant maldistribution: An experimental investigation in an automotive multi-evaporator air-conditioning and battery cooling system
Gillet, Thomas ULiege; Andres, Emmanuelle; El-Bakkali, Amin et al

in International Journal of Refrigeration (2018)

With the arrival of electrified vehicles, the air-conditioning system has to be reconsidered. Battery cooling management system and high level of comfort for passengers make the single evaporator ... [more ▼]

With the arrival of electrified vehicles, the air-conditioning system has to be reconsidered. Battery cooling management system and high level of comfort for passengers make the single evaporator airconditioning system a multi-evaporator one. In a multi-evaporator air-conditioning system, evaporating pressures are equal in each evaporator so that evaporators are coupled dynamically. However, the demand in cooling capacity and temperature target can vary from each other. For an operating point with a first evaporator working at high load and a second at low partial load, thermal interaction can occur from the superheated refrigerant coming from a first evaporator to the outlet of a second evaporator. This phenomenon makes the second evaporator sleeping since its expansion valve bulb misreads the superheat and closes. Furthermore, sleeping evaporator looks like an extreme case of refrigerant maldistribution in the evaporator. Refrigerant maldistribution is then investigated to show some drawbacks and advantages multi-evaporator air-conditioning systems (MEAC) have to face or can benefit by comparing two types of expansion valve: thermostatic and electronic ones. In this paper, sleeping evaporator and refrigerant maldistribution phenomena are experimentally investigated in order to propose in the future a robust control of an automotive MEAC. A test bench was built to compare two types of expansion valves (thermostatic/electronic) and study their behaviours in steady and transient state to tackle sleeping evaporators and benefit from refrigerant maldistribution. [less ▲]

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See detailExperimental validation of an electrical and thermal energy demand model for rapid assessment of rural health centers in sub-Saharan Africa
Orosz, Matthew; Altés Buch, Queralt ULiege; Mueller, Amy et al

in Applied Energy (2018)

Rapid deployment of health service infrastructure is underway to meet the growing needs of populations in subSaharan Africa, however the energy infrastructure needed to support high quality services has ... [more ▼]

Rapid deployment of health service infrastructure is underway to meet the growing needs of populations in subSaharan Africa, however the energy infrastructure needed to support high quality services has tended to lag. Understanding the electrical and thermal energy needs of health centers constructed with local building methods and materials and operating outside of the jurisdiction of heating, ventilation and air conditioning (HVAC) codes is complicated by a lack of appropriately scaled and configured energy system design frameworks and validation data for dynamic simulations. In this work we address this gap by linking the thermal envelope performance of health center buildings under heating and cooling loads with measured indoor air temperature, meteorological conditions, and operational electricity demand. A resistance-capacitive type energy balance model is parameterized using typical health center architectural data for sub-Saharan Africa (floor plans from Uganda and Lesotho) and heat transfer characteristics; to achieve this energy flows between HVAC equipment, internal loads, and ambient conditions are simulated on an hourly time step with indoor temperature thresholds representative of thermostat settings. A typical meteorological year dataset for Lesotho is used as a case study, validated with indoor temperature measurements and power metering at four health center sites spanning a daily patient load ranging from 15 to 450 per day over rural and urban communities. High resolution electricity measurements from smart meters installed at the clinics are used to close the energy balance and form the basis of a probabilistic method for forecasting long term hourly electricity demand in African health centers. These data and the corresponding method have relevance to energy system design for health clinics across sub-Saharan Africa, especially those featuring intermittent renewable generation. The integration of these two modeling approaches constitutes a novel tool for sizing and costing energy infrastructure to meet operational demand at health centers in both urban and rural areas of developing countries. [less ▲]

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