References of "Ngendakumana, Philippe"
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See detailDevelopment and validation of a condenser three zones model
Cuevas, Cristian; Lebrun, Jean ULg; Lemort, Vincent ULg et al

in Applied Thermal Engineering (2009)

A general and simple ‘‘deterministic” model of a refrigeration condenser is presented. The model assumes that the condenser can be divided into three distinct zones on the refrigerant side: the vapour de ... [more ▼]

A general and simple ‘‘deterministic” model of a refrigeration condenser is presented. The model assumes that the condenser can be divided into three distinct zones on the refrigerant side: the vapour de-superheating zone, the two-phase zone and the sub-cooled liquid zone. The model inputs are the air supply temperature, the air mass flow rate, the refrigerant supply temperature (or the over-heating), the exhaust sub-cooling and the refrigerant mass flow rate. The model is able to identify the pressures and temperatures in each zone and the corresponding heat flows. The model also gives the geometrical repartition among the zones and the pressure drop on air-side. The condenser model is validated with a total of 183 tests. Testing conditions cover a very wide domain, including pressures up to 40 bars with refrigerant R134a. The model is able to predict with a probability of 95% the condenser supply pressure within a confidence interval of +0.5 and 0.1 bar. This means a condenser power confidence interval within 200 and +100 W, which is considered here as acceptable. Refrigerant pressure drop is predicted with a higher error, but it is attributed to measuring uncertainty. On the other hand, air pressure drop is predicted with a very poor accuracy. Undoubtedly, this is due to the friction factor correlation used in this study which is not the most adequate. Here a difference of 40% is obtained. [less ▲]

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See detailFeasibility study of the diluted combustion in a domestic heating boiler
SEGGIO, Giovanni; Ngendakumana, Philippe ULg; PESENTI, Barbara et al

in 4th European Combustion Meeting (ECM2009) (2009, April)

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The principle of this type of ... [more ▼]

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The principle of this type of combustion consists in providing a high level of dilution of the reactants with flue gases before combustion reaction occurs, to get a slower reaction in a much larger volume than in classical combustion. The resulting lower local heat release leads to a more homogeneous temperature field in the furnace, without peak values responsible of high thermal NOx formation. There are two requirements for working in diluted combustion: the dilution level of reactants by the flue gases has to be high enough and the temperature level in the combustion chamber has to be above a threshold (the auto-ignition temperature of the mixture). The aim of this work is to assess the technical feasibility and highlight the specific problems of application of diluted combustion in a medium scale boiler. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber. That prevents from getting the minimum level of reactants dilution and temperature needed to reach diluted combustion regime. The idea is to use a natural gas jet-burner (to preheat the combustion chamber) along with a secondary gas injector in order to get a high entrainment of the flue gases by the reactant jets. In fact the air (through the jet-burner) and the gas (through the secondary gas injector) are injected separately in order to get a high dilution of the reactants and a mixture temperature above the auto-ignition threshold. Our test bench consists in a Viessmann hot water boiler whose nominal output power is 370 kW. The combustion chamber of this boiler is cylindrical (length = 1.41 m, diameter = 0.56 m) and is water-cooled. A preliminary CFD study (Fluent ®) has first been performed to select on the market a jet burner and to determine the position of the air and gas injectors able to generate the requirements of diluted combustion. The influence of the operating conditions (firing rate and excess air) has also been studied numerically. The simulation results show the possibility to obtain a temperature field quite homogenous (typical of diluted combustion) but with a light increase of the CO level at the exit of the combustion chamber. These numerical results (obtained with a simple combustion model) have to be validated experimentally. A first experimental study has been carried out in classical combustion on the boiler equipped with the selected jet-burner. The temperature field has been measured in the median plane of the combustion chamber for different excess air and firing rate. These measurements allowed us to verify that the preheating obtained with the jet-burner was important enough for getting a temperature level above the auto-ignition temperature near everywhere in the combustion chamber. A second experimental study in diluted combustion on the combustion chamber equipped with the secondary gas injector will allow the validation the corresponding numerical results. [less ▲]

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See detailPropulsion vehicle integration for reusable launcher using in-flight oxygen collection
Bizzarri, D.; Hendrick, Patrick ULg; Heyen, Georges ULg et al

in Aerospace Science and Technology (2008), 12(6), 429-435

The use of in-flight oxygen collection has shown to significantly improve space launcher performance. The conceptual approach followed by Belgian teams working on oxygen collection has been to try to ... [more ▼]

The use of in-flight oxygen collection has shown to significantly improve space launcher performance. The conceptual approach followed by Belgian teams working on oxygen collection has been to try to widening the available design margins in order to reduce the required technological leap and limit the economical risk associated with such a development. The aim of the ESA-funded theoretical and experimental study on an air separation device is to demonstrate the possibility of performing efficient air distillation in a compact rotating column. An integration of the vehicle, propulsion system and separation unit designs is presented. The objective is to optimise the overall vehicle performance while keeping technological difficulty and system complexity at a reasonable level. Reference vehicles are presented within their specific mission profiles with an emphasis on TSTO's. Different layouts of the internal energy and mass flowsheets have been studied and were compared in order to make best use of the refrigeration capacity of the hydrogen fuel running through the propulsion system during the first phase of the flight. In those flowsheets, the separator is considered as a classical distillation tray column. That analysis provides the requirements in terms of heat exchange capacity, compression ratios and number of so-called transfer units needed in the separator. The system is intentionally kept simple to limit complexity, but the analysis is thorough and accurate, including, for example, the effect of the presence of argon. Results for a supersonic carrier are presented. A compact separation unit has been designed in order to reach those requirements. That includes internals, practical building with estimates of pressure drops, separation performance and flow limitation. Main results are given, sizing of the separator bed is provided for a carrier plane showing that such on-board separator is indeed practical. (C) 2007 Elsevier Masson SAS. All rights reserved. [less ▲]

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See detailMODELLING OF A DOMESTIC GAS-FIRED CONDENSING BOILER
Makaire, Danielle ULg; Ngendakumana, Philippe ULg

Conference (2008, September)

Nowadays, condensing technology is widely used in domestic heating. This paper presents a model that simulates the performance in steady-state regime of a domestic gas-fired condensing boiler. The model ... [more ▼]

Nowadays, condensing technology is widely used in domestic heating. This paper presents a model that simulates the performance in steady-state regime of a domestic gas-fired condensing boiler. The model is similar to a conventional boiler model with a dry heat exchanger at which a wet heat exchanger is added to simulate the heat recovered by condensation. Experimental parameters are used to simulate the different components. The model has been applied to a 24 kW gas-fired condensing boiler test bench available in the laboratory. According to the experimental results (at full load), the model predicts correctly the thermal efficiency of the boiler. Indeed, calculated values are in good agreement with measured values. [less ▲]

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See detailMODELLING OF A DOMESTIC GAS-FIRED CONDENSING BOILER
Ballant, Adrien; Makaire, Danielle ULg; Ngendakumana, Philippe ULg

Scientific conference (2008, May)

Within the actual context of energy savings and pollutant emissions reduction, installing condensing boilers becomes indispensable because of their high efficiency compared to conventional boilers. A ... [more ▼]

Within the actual context of energy savings and pollutant emissions reduction, installing condensing boilers becomes indispensable because of their high efficiency compared to conventional boilers. A simulation model predicting boiler performances and condensing rate in the boiler heat exchanger is very valuable. The model developed within this work is a one-dimension model of a domestic gasfired condensing boiler. The aim of the model is to know whether or not the boiler works in good condensing conditions. It gives a better understanding of using and installation requirements of condensing boilers. The structure of the model is similar to a conventional boiler model [1] with a combustion chamber and a dry heat exchanger (HX1), at which a wet heat exchanger (HX2) is added (Figure 1). The calculation consists of evaluating combustion gas temperature and gas composition after the dry heat exchanger. Then, retrievable energy from the flue gas is calculated for a fixed geometry and efficiency of wet heat exchanger and for a fixed return water temperature. The heat transfer coefficient in the wet heat exchanger is calculated according to Liang et al. [2] . The influence of different parameters on condensing performances are analysed: excess air, return water temperature and flue gas mass flow rate for different heat output power. The model has been validated with measurements on a test bench equipped with a 24 kW gas-fired condensing boiler. The test bench is represented on Figure 2. [less ▲]

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See detailSIMULATION MODEL OF A SEMI-INDUSTRIAL FUEL OIL BOILER
Makaire, Danielle ULg; Ngendakumana, Philippe ULg

in Stoffels, G. G. M.; van der Meer, T. H.; van Steenhoven, A. A. (Eds.) Proceedings 5th European Thermal-Sciences Conference (2008, May)

The model developed within this work is a model which simulates the performance in steady-state regime of an industrial fuel oil boiler equipped with a two firing rate burner. To simplify calculations ... [more ▼]

The model developed within this work is a model which simulates the performance in steady-state regime of an industrial fuel oil boiler equipped with a two firing rate burner. To simplify calculations, the model uses two parameters which were fitted from experimental results. A literature review was first performed in order to get the most suitable correlations for the gas and water flows in the heat exchangers. The comparison of simulation and experimental results shows that, in general, gas temperature at the exhaust of the combustion chamber is predicted within the measurement uncertainty at high firing rate. The error on gas temperature at the boiler stack is below 10K and the power transferred to the water is also well estimated (below 2% of error) for both firing rates. The model was validated with complementary tests at low and high firing rates. The results show that gas temperatures and the useful effect are within the measurements uncertainty. The validity of the model is restricted to fuel mass flow rates around the nominal flow rates. [less ▲]

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See detailCompact Air Separation Technology For In-Flight Oxygen Collection
Bizzarri, Didier; Hendrick, Patrick; Heintz, N. et al

in 15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference (2008, April)

In the context of an ESA-funded study on an air separation device intended to provide in-flight Oxygen Collection capability to future launchers, experimental and system level investigations are performed ... [more ▼]

In the context of an ESA-funded study on an air separation device intended to provide in-flight Oxygen Collection capability to future launchers, experimental and system level investigations are performed. The project consortium is run by the Université Libre de Bruxelles and includes the Belgian Defence, Techspace Aero (Safran Group) and Liège university among others. In-flight Oxygen Collection has already been described in previous publications, mainly as a conceptual approach. The improvement potentials have been studied and possible uses of the technology go beyond the concept presented here. That is in the aerospace field and also outside, in a much wider range of applications. Hardware work on compact separation are seldom described. As the setup was nearing completion, design know how improved. The last problems were solved and the setup was made fully operational and subject to testing. The following review summarizes the work with latest information on the technological and experimental aspects. In the vehicles using air separation and collection, the cooling capacity of the fuel, liquid hydrogen, is used during a first air breathing phase of the flight to enrich in oxygen and liquefy a fraction of the incoming air. Compact and light weight heat exchanger, coupled to the separator, perform that task. The main advantages of the concept, applied in our preferred concept to TSTO’s, are a much reduced take off mass, a reduced mass for the liquid rocket engines and a much increased operational flexibility in terms of reachable orbit and launch window. Moreover, unlike scramjet propulsion, separation does not rely on high technology material but on readily available material and hardware used with proper design know how and appropriate expertise. The experimental setup development follows a somewhat different route. Liquid and saturated gaseous air are prepared in special heat exchangers before the separator can be fed, the cold source used being liquid nitrogen. The experimental separator itself is, in reality, a 'section' of a real separator. Disposing of the fluids in this machine deserves special care, since pressure has to be controlled while a liquid seal has to be kept stable in most of the operating conditions. Some workarounds had to be developed for that last problem and different solutions were kept available during the testing. Separating is an aspect, interactively measuring -required to tune to proper performance- is another. The operating fluids, that are supposed to be liquid or gaseous in the simple modeling, are in practice often two phase, which is difficult to asses during test and which can strongly impact flow and concentration measurements. High temperature gradients, low temperatures had to be considered for mechanical, sealing and bearing design, nevertheless, strong uncertainty remained before separation results are presented and demonstrate the concept. Most result went above expectations and much further compactification potentials are present. The know how gathered from testing experience allows to foresee improvement directions, both in the global concept and the detail design of a real unit. Those results will allow to extrapolate the real potentials of the separator design developed by our laboratory to the bigger units required for a real concept. [less ▲]

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See detailExperimental study of air-hydrogen heat exchangers
Hendrick, Patrick; Heintz, N.; Bizzarri, Didier et al

in The 15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference . April 28- May 1 2008 (2008, April)

Detailed reference viewed: 20 (1 ULg)
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See detailFeasibility study of the diluted combustion in a semi-industrial boiler at low temperatures
SEGGIO, Giovanni; PESENTI, Barbara; LYBAERT, Paul et al

in 8th European Conference on Industrial Furnaces and Boilers (2008, March)

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess ... [more ▼]

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess the technical feasibility and highlight the specific problems of application of diluted combustion in a medium scale boiler. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which could prevent from getting the minimum level of reactants dilution and temperature needed to reach diluted combustion regime. The idea is to perform direct injection of the air and the gas in the combustion chamber in order to get a high dilution of the reactants and a mixture temperature above the auto-ignition threshold. Our test bench consists in a Viessmann hot water boiler whose nominal output power is 370 kW. The combustion chamber of this boiler is cylindrical (length = 1.41 m, diameter = 0.56 m) and is watercooled. A preliminary CFD study (Fluent ®) has first been performed to select on the market a jet burner (to be used for the preheating of the combustion chamber) and to determine the position of the air and gas injectors able to generate the requirements of diluted combustion. The selected burner has been purchased and fitted on the boiler. Then, the boiler-burner set has been characterized experimentally in normal combustion regime in order to adapt the boundary conditions to the heat balance. The temperature and the CO concentration will be measured in several locations in the combustion chamber at different firing rate and air excess. In short, the selected burner provides as expected the required preheating and the generated flame doesn’t impact the bottom of the combustion chamber. The results obtained experimentally confirm the simulation results in normal combustion regime. The last part of this work will consist in the determination of the feasibility of the diluted combustion in this boiler. [less ▲]

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See detailCO emissions of fuel oil boilers in transient and cyclic regimes: performance of burners without and with “antidrip” systems
Makaire, Danielle ULg; Ngendakumana, Philippe ULg

Conference (2007, September)

CO emission peaks from fuel oil boilers in transient and cyclic regimes have been measured in previous studies. In order to evaluate these emissions, tests have been performed without and with an anti ... [more ▼]

CO emission peaks from fuel oil boilers in transient and cyclic regimes have been measured in previous studies. In order to evaluate these emissions, tests have been performed without and with an anti-drip system installed on the burner nozzle. Flue gas composition was measured using classical analysers (CO2, O2, CO and NOx) and CO emissions results were analysed and discussed. It was found that the anti-drip system reduced cold start CO emissions and did not affect steady-state CO emissions. At first, no reduction was noticed when the burner was cycling. Further investigation indicated that there was an experimental artefact caused by an air volume trapped in the pressure measurement system. When the air was purged and with the anti-drip system, CO peaks when the burner was cycling were strongly reduced and CO emissions remained under European standards limits. [less ▲]

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See detailSecond breadboard design
Dardenne, Laurent; Ngendakumana, Philippe ULg

Report (2007)

Detailed reference viewed: 2 (0 ULg)
See detailFeasibility study of the diluted combustion in a semi-industrial boiler at low temperatures
Seggio, Giovanni; Ngendakumana, Philippe ULg; Pesenti, Barbara et al

Conference (2007, September)

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main ... [more ▼]

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which prevents from getting the minimum level of reactants dilution and temperature needed to reach mild combustion regime. Last year, a preliminary CFD study was performed to select a jet burner and secondary gas injector able to generate sufficient dilution and temperature of the air and gas jets before they meet in the combustion chamber of the boiler. In this work, the optimization of the position and the diameter of the gas injector has been performed. Finally, the boundary conditions and the parameters of the combustion model have been investigated. [less ▲]

Detailed reference viewed: 15 (5 ULg)