Thermo-hydraulic characterization of an automotive intercooler for a low pressure EGR application

in Applied Thermal Engineering (2011), 31(14-15), 2474-2484

In this work an experimental study is carried out to determine the thermo-hydraulic performance of an intercooler (IC) with flat tubes provided with triangular plain internal fins and louvered external ... [more ▼]

In this work an experimental study is carried out to determine the thermo-hydraulic performance of an intercooler (IC) with flat tubes provided with triangular plain internal fins and louvered external fins when it is used on a car equipped with a low pressure EGR. The main unknowns to be answered are the thermo-hydraulic characteristics of the IC working under humid conditions induced by EGR, the conditions under which the water content in the mixture of air and exhaust gases begins to condense and the conditions under which the condensed water will be retained inside the IC. The exhaust gases are here replaced by a mixture of dry air and water vapour which are mixed upstream of the IC. The IC is submitted at the following testing conditions: on the ambient air side, the air temperature is fixed at around 20 °C and the air velocity is settled at 1, 2 and 4 ms/s; on the exhaust gases side, the supply temperature was varied between 90 and 150 °C, with dry gas flow rates of 20, 50 and 100 g /s, and water contents varying between almost 0 and 0.09 kgw kgg-1. At these conditions the IC transfers between 1 and 13 kW with overall heat transfer conductance varying between 0.05 and 0.38 kWK-1 and effectivenesses between 0.3 and 0.97. A water accumulation inside the IC was detected for the tests carried out at low dry gas flow rate of 20 g s-1 and for all the water content explored here (higher than 0.02 kgw kgg-1). [less ▲]

Validation théorique d’une Architecture d’injection Régénérative pour moteur thermique au Gaz Liquéfié (VARGAL) : Rapport semestriel n° 4, Rapport Final.

Report (2011)

Thermo-hydraulic Characterization of a Louvered Fin and Flat Tube Heat Exchanger

in Experimental Thermal & Fluid Science (2011), (1), 154164

In the present study, a whole heat exchanger with a hydraulic diameter of 2.3 mm is tested, which is a minichannel heat exchanger according to the Kandlikar classification. This is a louvered fin and flat ... [more ▼]

In the present study, a whole heat exchanger with a hydraulic diameter of 2.3 mm is tested, which is a minichannel heat exchanger according to the Kandlikar classification. This is a louvered fin and flat tube heat exchanger currently used in car cooling systems, also known as radiator. A glycol-water mixture (60/40 in volume) circulates through the tubes at flows ranging from 100 to 7800 l/h and at a supply temperature of 90ºC. This fluid is cooled with ambient air at a temperature of 20ºC and at frontal air velocities varying between 0.5 and 7 m/s. The thermohydraulic performance of the heat exchanger is compared with the classical correlations given in the literature for the heat transfer and the friction factor calculation. On the glycolwater side the heat exchanger is characterized for Reynolds numbers from 30 to 8000. A first comparison is carried out with the correlations available in the literature with a purely predictive model by obtaining a predictive value with a systematic under prediction lower than 10%. In a second step a semi-empirical model is considered to identify the experimental heat transfer coefficients for this application. [less ▲]

Validation théorique d’une Architecture d’injection Régénérative pour moteur thermique au Gaz Liquéfié (VARGAL) : Rapport semestriel n° 3

Report (2010)

SIMULATION MODEL OF A GAS-FIRED CONDENSING BOILER AT FULL LOAD OPERATION IN STEADY-STATE REGIME

in ASME-ATI-UIT 2010 Conference on Thermal and Environmental Issues in Energy Systems (2010, May)

The model in this paper was developed to predict thermal performances of gas-fired condensing boilers. The structure of the developed model is similar to the one of a conventional boiler with a main ... [more ▼]

The model in this paper was developed to predict thermal performances of gas-fired condensing boilers. The structure of the developed model is similar to the one of a conventional boiler with a main counterflow gas-water heat exchanger, at which a condensing heat exchanger is added. Prior to the second heat exchanger, the exhaust gas are converted into equivalent wet air. The condensing heat exchanger is divided into smaller parts and each part is simulated by a cooling coil model currently used in HVAC simulation. Several tests have been performed in steady-state regime on a household gas-fired boiler whose nominal output is 24 kW. The experimental results are compared to the model results and the results are discussed. [less ▲]

Modelling the thermal efficiency of condensing boilers working in steady-state conditions

Scientific conference (2010, May)

The structure of the model is similar to the model of a conventional boiler model with a main counterflow gas-water heat exchanger (HX1), at which a condensing heat exchanger is added (HX2). The case ... [more ▼]

The structure of the model is similar to the model of a conventional boiler model with a main counterflow gas-water heat exchanger (HX1), at which a condensing heat exchanger is added (HX2). The case losses to the ambient is neglected. Prior to the second heat exchanger (HX2), the exhaust gas are converted to equivalent wet air as the wet heat exchanger is simulated by a cooling coil used in air treatment. The model has been validated experimentally on gas- and oil-fired boilers. Calculated thermal efficiencies agree very well with experimental results. [less ▲]

Equipement à combustion diluée au gaz naturel et chaudières à combustible liquide : rapport technique annuel des travaux 2009

Report (2010)

Air–Hydrogen Heat Exchangers for Advanced Space Launchers

in Journal of Propulsion and Power (2009), 25(6),

This paper deals with air–hydrogen heat exchangers intended to provide in-flight oxygen collection capability to a reusable or semireusable two-stages-to-orbit launcher with an oxygen collection phase in ... [more ▼]

This paper deals with air–hydrogen heat exchangers intended to provide in-flight oxygen collection capability to a reusable or semireusable two-stages-to-orbit launcher with an oxygen collection phase in supersonic cruise at Mach 2.5. It aims to present a theoretical but mainly technological and experimental feasibility study of heat exchangers sufficiently efficient and reliable to suit the extreme requirements of this application. Two precoolers of two different types (shell and tubes, and plate and fins) have been selected and designed with the objective of fulfilling all constraints of the concept in terms of performance, leak tightness, reliability, compactness, etc. This design process has been validated with four subscaled breadboards (two of each type) tested on two test benches (for performance and leak tightness), developed by Belgium and Spain, in on-design and off-design conditions. All these results highlight the suitability of the new technologies given the extreme requirements of the concept. An optimum design for each technology is recommended considering its proper advantages and disadvantages. An innovative precooler technology is presented and tested. [less ▲]

Adaptation des brûleurs SOCOMEF pour l'utilisation d'agrocombustibles

Report (2009)

Feasibility study of the diluted combustion in a domestic heating boiler

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 ▲]