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See detailPerformance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application: An experimental comparison between R245fa and R1233zd
Guillaume, Ludovic ULg; Legros, Arnaud ULg; Desideri, Adriano ULg et al

in Applied Energy (2016)

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial ... [more ▼]

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial- inflow turbine is a small-scale prototype designed to convert the waste heat from the exhaust gases of a truck combustion engine and was developed mainly using components of truck turbochargers. It is directly connected to a high-speed synchronous generator. The bearings system of the turbine and the generator have the innovative particularity to be respectively lubricated and cooled down by the working fluid so no additional lubricant or coolant is needed. The experimental comparison is carried out over a test-rig equipped with the radial turbine. The heat wasted by the truck through the exhaust gases is sim- ulated using an electric oil boiler coupled to the ORC loop. The electrical power supplied by the turbine, limited to a maximum of 3.5 kWel by the generator, is then dissipated in a load bank composed of truck fans while the condenser is cooled by a water loop. Measurements in steady-state are performed in order to evaluate the performance of the turbine-generator set when varying the pressure ratio, the rotational speed, the inlet temperature and the mass flow rate of the turbine and the lubrication flow rate of the bearings for various oil temperatures and mass flow rates. In order to identify the most suitable fluid for the Waste Heat Recovery (WHR) application, three comparison methods are proposed and discussed based on the measurements. Finally, because the turbine-generator set is the first oil-free prototype developed by the manufacturer, potential sources of improvements are discovered and discussed. [less ▲]

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See detailTransient performance evaluation of waste heat recovery Rankine cycle based system for heavy duty trucks
Grelet, Vincent; Reiche, Thomas; Lemort, Vincent ULg et al

in Applied Energy (2016)

The study presented in this paper aims to evaluate the transient performance of a waste heat recovery Rankine cycle based system for a heavy duty truck and compare it to steady state evaluation. Assuming ... [more ▼]

The study presented in this paper aims to evaluate the transient performance of a waste heat recovery Rankine cycle based system for a heavy duty truck and compare it to steady state evaluation. Assuming some conditions to hold, simple thermodynamic simulations are carried out for the comparison of several fluids. Then a detailed rst principle based model is also presented. Last part is focused on the Rankine cycle arrangement choice by means of model based evaluation of fuel economy for each concept where the fuels savings are computed using two methodologies. Fluid choice and concept optimization are conducted taking into account integration constraints (heat rejection, packaging . . . ). This paper shows the importance of the modeling phase when designing WHRS and yields a better understanding when it comes to a vehicle integration of a Rankine cycle in a truck. [less ▲]

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See detailExperimental study of an oil-free steam piston expander for micro-combined heat and power systems
Bouvier, Jean-Louis; Lemort, Vincent ULg; Michaux, Ghislain et al

in Applied Energy (2016), 1 69

This paper presents an experimental study conducted on an oil-free steam piston expander for micro combined heat and power systems. This expander can produce electrical power (between 740 and 2400 W) with ... [more ▼]

This paper presents an experimental study conducted on an oil-free steam piston expander for micro combined heat and power systems. This expander can produce electrical power (between 740 and 2400 W) with a significant range of supply temperature (between 260 and 340 C) and pressure (between 20 and 34 bar). The expander electrical power output exhibits a fast dynamic response to a change of working or supply fluid conditions. The reached expander overall isentropic efficiency (including electrical generator efficiency) was between 19% and 40%. An empirical model has been developed in order to conduct a sensitivity analysis of the system by varying working variables such as supply and exhaust pressures, rotational speed and supply temperature. The parameters of this model have been identified using experimental results. The sensitivity analysis showed a limited increase of the electrical power output with a rotational speed until 900 rpm and a reduction of the power output for values beyond 900 rpm. It also highlighted the significant positive impact of the supply pressure on the electrical power output and the negative impact of the superheating on the expander overall isentropic efficiency. The obtained results are useful for the future control of the expander integrated into a Rankine cycle. Since the fluid at the expander exhaust is steam at a pressure close to 1 bar, it is possible to produce heat at a temperature close to 80 C, which is sufficient for most domestic applications (heating or direct hot water production). [less ▲]

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See detailQuantifying self-consumption linked to solar home battery systems: Statistical analysis and economic assessment
Quoilin, Sylvain ULg; Kavvadias, Konstantinos; Mercier, Arnaud et al

in Applied Energy (2016)

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See detailSimulation and optimization of a CHP biomass plant and district heating network
Sartor, Kevin ULg; Quoilin, Sylvain ULg; Dewallef, Pierre ULg

in Applied Energy (2014), 130

Biomass Combined Heat and Power (CHP) plants connected to district heating (DH) networks are recognized nowadays as a very good opportunity to increase the share of renewable sources into energy systems ... [more ▼]

Biomass Combined Heat and Power (CHP) plants connected to district heating (DH) networks are recognized nowadays as a very good opportunity to increase the share of renewable sources into energy systems. However, as CHP plants are not optimized for electricity production, their operation is profitable only if a sufficient heat demand is available throughout the year. Most of the time, pre-feasibility studies are based on peak power demand and business plans only assume monthly or yearly consumption data. This approach usually turns out to overestimate the number of operating hours or oversize the plant capacity. This contribution presents a methodology intended to be simple and effective that provides accurate estimations of economical, environmental and energetic performances of CHP plants connected to district heating networks. A quasi-steady state simulation model of a CHP plant combined with a simulation model of the district heating network installed on the Campus of the University in Liège (Belgium) is used as an application framework to demonstrate the effectiveness of the selected approach. Based on the developed model and actual consumption data, several scenarios for energy savings are considered and ranked. The potential energy savings and resulting energy costs are estimated enabling more general conclusions to be drawn on the opportunity of using district heating networks in urban districts for Western Europe countries. [less ▲]

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See detailSystematic optimization of subcritical and transcritical organic Rankine cycles (ORCs) constrained by technical parameters in multiple applications
Maraver, Daniel; Royo, Javier; Lemort, Vincent ULg et al

in Applied Energy (2014), 117

The present work is focused on the thermodynamic optimization of organic Rankine cycles (ORCs) for power generation and CHP from different average heat source profiles (waste heat recovery, thermal oil ... [more ▼]

The present work is focused on the thermodynamic optimization of organic Rankine cycles (ORCs) for power generation and CHP from different average heat source profiles (waste heat recovery, thermal oil for cogeneration and geothermal). The general goal is to provide optimization guidelines for a wide range of operating conditions, for subcritical and transcritical, regenerative and non-regenerative cycles. A parameter assessment of the main equipment in the cycle (expander, heat exchangers and feed pump) was also carried out. An optimization model of the ORC (available as an electronic annex) is proposed to predict the best cycle performance (subcritical or transcritical), in terms of its exergy efficiency, with different working fluids. The working fluids considered are those most commonly used in commercial ORC units (R134a, R245fa, Solkatherm, n-Pentane, Octamethyltrisiloxane and Toluene). The optimal working fluid and operating conditions from a purely thermodynamic approach are limited by the technological constraints of the expander, the heat exchangers and the feed pump. Hence, a complementary assessment of both approaches is more adequate to obtain some preliminary design guidelines for ORC units. [less ▲]

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See detailA review on simulation-based optimization methods applied to building performance analysis
Nguyen, Anh Tuan ULg; Reiter, Sigrid ULg; Rigo, Philippe ULg

in Applied Energy (2014), 113

Recent progress in computer science and stringent requirements of the design of “greener” buildings put forwards the research and applications of simulation-based optimization methods in the building ... [more ▼]

Recent progress in computer science and stringent requirements of the design of “greener” buildings put forwards the research and applications of simulation-based optimization methods in the building sector. This paper provides an overview on this subject, aiming at clarifying recent advances and outlining potential challenges and obstacles in building design optimization. Key discussions are focused on handling discontinuous multi-modal building optimization problems, the performance and selection of optimization algorithms, multi-objective optimization, the application of surrogate models, optimization under uncertainty and the propagation of optimization techniques into real-world design challenges. This paper also gives bibliographic information on the issues of simulation programs, optimization tools, efficiency of optimization methods, and trends in optimization studies. The review indicates that future researches should be oriented towards improving the efficiency of search techniques and approximation methods (surrogate models) for large-scale building optimization problems; and reducing time and effort for such activities. Further effort is also required to quantify the robustness in optimal solutions so as to improve building performance stability. [less ▲]

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See detailDevelopment of benchmark models for the Egyptian residential buildings sector
Attia, Shady ULg; Evrard, Arnaud; Gratia, Elisabeth

in Applied Energy (2012), 94

The aim of this study is to develop representative simulation building energy data sets and benchmark models for the Egyptian residential sector. This study reports the results of a recent field survey ... [more ▼]

The aim of this study is to develop representative simulation building energy data sets and benchmark models for the Egyptian residential sector. This study reports the results of a recent field survey for residential apartment buildings in Egypt. Two building performance simulation models are created reflecting the average energy consumption characteristics of air-conditioned residential apartments in Alexandria, Cairo and Asyut. Aiming for future evaluation of the cost and energy affects of the new Egyptian energy standard this study established two detailed models describing the energy use profiles for air-conditioners, lighting, domestic hot water and appliances in respect to buildings layout and construction. Using EnergyPlus simulation tool the collected surveyed data was used as input for two building simulation models. The simulation models were verified against the apartment characteristic found in the survey. This paper presents details of the building models including the energy use patterns and profiles created for this study. [less ▲]

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See detailAdaptive thermal comfort model for different climatic zones of North-East India
Singh, Manoj Kumar ULg; Mahapatra, Sadhan; Atreya, S.K.

in Applied Energy (2011), 88(7), 2420-2428

Thermal comfort standards ISO 7730 and ASHRAE 55-2004 are based on the experimental results conducted in climatic chambers and the adaptive opportunities are usually limited in these experiments. However ... [more ▼]

Thermal comfort standards ISO 7730 and ASHRAE 55-2004 are based on the experimental results conducted in climatic chambers and the adaptive opportunities are usually limited in these experiments. However, in naturally ventilated buildings, adaptive opportunities are not fixed and occupants always have the liberty to modify the opportunities in order to feel comfortable. A comfort survey has been carried out in three different climatic zones of North-East India in four different seasons of a year. Climatic parameters corresponding to actual mean vote (AMV) are recorded during the survey and the values are used to calculate the predicted mean vote (PMV) using ISO 7730 calculation procedures. Results show that the PMV deviates from AMV values. A corrective term ‘adaptive coefficient’ is calculated based on PMV and AMV values and least square method to assess the different adaption used for thermal comfort. Theoretical adaptive models of thermal comfort have been developed based on these adaptive coefficients for the region. The adaptive coefficient values are varying for different seasons and also for different climatic zones. This reflects the various levels of adaptation in different seasons in a particular climatic zone. This adaptive coefficient can be used as a reference to thermal comfort assessment of the buildings and also can be used as dynamic control of the set temperature in the air conditioning system, which will results enormous energy saving. Result of this study also contributes towards the debate over the applicability of PMV model to naturally ventilated building. [less ▲]

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See detailDynamic modeling and optimal control strategy of waste heat recovery Organic Rankine Cycles
Quoilin, Sylvain ULg; Aumann, Richard; Grill, Andreas et al

in Applied Energy (2011)

Organic Rankine Cycles (ORCs) are particularly suitable for recovering energy from low-grade heat sources. This paper describes the behavior of a small scale ORC used to recover energy from a variable ... [more ▼]

Organic Rankine Cycles (ORCs) are particularly suitable for recovering energy from low-grade heat sources. This paper describes the behavior of a small scale ORC used to recover energy from a variable flow rate and temperature waste heat source. A traditional static model is unable to predict transient behavior in a cycle with a varying thermal source, whereas this capability is essential for simulating an appropriate cycle control strategy during part-load operation and start and stop procedures. A dynamic model of the ORC is therefore proposed focusing specifically on the time-varying performance of the heat exchangers, the dynamics of the other components being of minor importance. Three different control strategies are proposed and compared. The simulation results show that a model predictive control strategy based on the steady-state optimization of the cycle under various conditions is the one showing the best results. [less ▲]

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See detailDevelopment of benchmark models for the Egyptian residential buildings sector
Attia, Shady

in Applied Energy (2011)

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See detailExperimental study and modeling of an Organic Rankine Cycle using scroll expander
Quoilin, Sylvain ULg; Lemort, Vincent ULg; Lebrun, Jean ULg

in Applied Energy (2010), 87(4), 1260-1268

This paper presents both a numerical model of an Organic Rankine Cycle (ORC) and an experimental study carried out on a prototype working with refrigerant HCFC-123, and whose heat sources consist in two ... [more ▼]

This paper presents both a numerical model of an Organic Rankine Cycle (ORC) and an experimental study carried out on a prototype working with refrigerant HCFC-123, and whose heat sources consist in two hot air flows. The ORC model is built by interconnecting different sub-models: the heat exchanger models, a volumetric pump model and a scroll expander model. Measured performance of the ORC prototype is presented and used to validate the ORC model. This model is finally used to investigate potential improvements of the prototype. [less ▲]

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See detailA parametric study on the emissions from an HCCI alternative combustion engine resulting from the auto-ignition of primary reference fuels
Machrafi, Hatim ULg; Cavadias, Simeon; Amouroux, Jacques

in Applied Energy (2008), 85(8), 755-764

The homogeneous charge compression ignition is an alternative combustion technology that can reduce automobile pollution, provided that the exhaust emission can be controlled. A parametric study can be ... [more ▼]

The homogeneous charge compression ignition is an alternative combustion technology that can reduce automobile pollution, provided that the exhaust emission can be controlled. A parametric study can be useful in order to gain more understanding in the emission reduction possibilities via this new combustion technology. For this purpose, the inlet temperature, the equivalence ratio and the compression ratio are changed, respectively, from 30 to 70 degrees C, 0.28 to 0.41 and 6 to 14. Also the diluting, thermal and chemical effects of exhaust gas recirculation were studied. The emission of CO, CO2, O-2 and hydrocarbons has been measured using primary reference fuels. It appears that an increase in the inlet temperature, the EGR temperature, the equivalence ratio and the compression ratio results into a decrease of the emissions of CO and the hydrocarbons of up to 75%. The emission of CO2 increased, however, by 50%. The chemical parameters showed more complicated effects, resulting into a decrease or increase of the emissions, depending on whether the overall reactivity increased or not. If the reactivity increased, generally, the emissions of CO and hydrocarbons increased, while that of CO2 increased. The increase of CO2 emissions could be compensated by altering the compression ratio and the EGR parameters, making it possible to control the emission of the HCCI engine. (c) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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