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Peer Reviewed
See detailExperimental study and modelling of cooling ceiling systems using steady-state analysis.
Fonseca, N.; Lebrun, J.; Andre, Philippe ULiege

in International Journal of Refrigeration (2010), 33

Detailed reference viewed: 56 (17 ULiège)
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See detailExperimental Study and Statistical Modeling of an Injection Scroll Compressor Operating with R407c.
Quoilin, Sylvain ULiege

E-print/Working paper (2014)

This working paper describes an experimental study carried out on a refrigeration scroll compressor with and without vapour injection. The test rig designed for that purposed allows evaluating the ... [more ▼]

This working paper describes an experimental study carried out on a refrigeration scroll compressor with and without vapour injection. The test rig designed for that purposed allows evaluating the performance over a wide range of operating conditions, by varying the supply pressure, the injection pressure, the exhaust pressure, the supply superheating and the injection superheating. 97 Steady-state points are measured, with a maximum isentropic efficiency of 64.1% and a maximum consumed electrical power of 13.1 kW. A critical analysis of the experimental results is then carried out to evaluate the quality of the data using a machine learning method. This method based on Gaussian Processes regression, is used to build a statistical operating map of the compressor as a function of the different inputs. This statistical operating map can then be compared to the experimental data points to evaluate their accuracy. [less ▲]

Detailed reference viewed: 139 (15 ULiège)
Peer Reviewed
See detailExperimental study of a heat exchanger for an in-flight oxygen collection launcher
Hendrick, Patrick; Bizzarri, Didier; Dardenne, Laurent et al

in 14th AIAA/AHI International Space Planes and Hypersonic Systems and Technologies Conference (2006, November)

In the scope of an ESA-funded theoretical and experimental study (in the GSTP3 program) on heat exchangers intended to provide in-flight oxygen collection capability to a reusable or a semi-reusable TSTO ... [more ▼]

In the scope of an ESA-funded theoretical and experimental study (in the GSTP3 program) on heat exchangers intended to provide in-flight oxygen collection capability to a reusable or a semi-reusable TSTO launcher with an oxygen collection phase in supersonic cruise, two subscale models of an air-hydrogen precooler and a test set-up are currently being developed in Belgium and in Spain. The vehicle we foresee for this application is described in previous conference papers as well as the work on our ESA-funded airborne air separator, which is the other critical element of the oxygen collection plant. This current paper is concentrating only on the theoretical but mainly the technological and experimental aspects of such an air precooler. The experimental and technical aspects include choices and main trade-offs that have had to be made during the design process by the different partners (Techspace Aero, von Karman Institute, Iberespacio, University of Liège, Royal Military Academy of Belgium and University of Brussels). After we fixed the requirements at system level and at the precooler level, a simulation work of generic heat exchangers is presented including the problem of frost formation and its influence on the heat exchanger performance. A few advanced heat exchanger designs are analysed resulting in a more detailed parametric and performance analysis of two advanced configurations. A detailed study of the most advantageous heat exchangers materials is shown resulting in the selection of the alloys for the two breadboards. The manufacturing processes for these two breadboards are defined, based on trials on small scale models inspired from the two technology candidates. Perspectives are also given for the mechanical and thermodynamic testing of the two breadboards. [less ▲]

Detailed reference viewed: 67 (1 ULiège)
Peer Reviewed
See detailExperimental study of a randomly agitated 2D granular pile
Lumay, Geoffroy ULiege

Conference (2006, June 09)

Detailed reference viewed: 4 (1 ULiège)
Peer Reviewed
See detailExperimental study of a river biofilm growth on artificial cobbles in contrasted flow conditions
Moulin, F.; Peltier, Yann ULiege; Pen, C. et al

in International Workshop on Environmental Hydraulics (2009)

Detailed reference viewed: 23 (5 ULiège)
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See detailExperimental study of a vertical column of grains submitted to a series of impulses
Lumay, Geoffroy ULiege; Dorbolo, Stéphane ULiege; Gerasimov, Oleg et al

in European Physical Journal E -- Soft Matter (2013), 36

Detailed reference viewed: 44 (14 ULiège)
Peer Reviewed
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: 26 (1 ULiège)
Peer Reviewed
See detailExperimental Study Of An In-Flight Air Separation Device
Bizzarri, Didier; Hendrick, Patrick; Heyen, Georges ULiege et al

in AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference (2005, May)

Intending to provide in-flight Oxygen Collection capability to new launchers, a subscale model of a centrifugally enhanced air distillation unit is under development. The vehicle we foresee for this ... [more ▼]

Intending to provide in-flight Oxygen Collection capability to new launchers, a subscale model of a centrifugally enhanced air distillation unit is under development. The vehicle we foresee for this application is described elsewhere, the present paper concentrating only on the technological and experimental aspects. While the test setup has already been shown to be able to provide the adequate cooling power, the rig is still under construction. The experimental and technical aspects include choices and main trade-offs that had to be made during the design process. Of particular interest are the stainless steel all welded heat exchangers allowing for deep cooling and liquefaction of air from the main compressor and dryers. Specifically, developed hardware is described in details. On the test rig side, design of the rotating cryogenic separator is explained, including mechanical aspects, heat management and sealing. The whole system has modes of operation allowing, among other parameters, to explore various air compositions and mass flows rates on the gaseous and liquid sides. Perspectives are given for the testing of the separator. [less ▲]

Detailed reference viewed: 181 (5 ULiège)
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Peer Reviewed
See detailExperimental study of an oil-free steam piston expander for micro-combined heat and power systems
Bouvier, Jean-Louis; Lemort, Vincent ULiege; 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 ▲]

Detailed reference viewed: 18 (0 ULiège)
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See detailExperimental study of ball and roller bearings
Hanocq, Charles ULiege

in Proceedings of the general discussion on lubrication & lubricants : 13th-15th October 1937. Volume 2 (1937)

Detailed reference viewed: 10 (0 ULiège)
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Peer Reviewed
See detailExperimental study of cracking induced by desiccation in 1-dimensional systems
Lecocq, N.; Vandewalle, Nicolas ULiege

in European Physical Journal E -- Soft Matter (2002), 8(4), 445-452

We designed a simple experiment to study both the dynamical and statistical properties of cracking that occurs in a one-dimensional system composed of wet clay (or similar material) exposed to shrinkage ... [more ▼]

We designed a simple experiment to study both the dynamical and statistical properties of cracking that occurs in a one-dimensional system composed of wet clay (or similar material) exposed to shrinkage induced by desiccation. We study both the dynamical formation of cracks and the statistical characteristics of the final cracks pattern. We observe that the drying rate has a strong influence on the way cracks appear and grow. We find that the final crack width is related to the order of apparition of the cracks. We discuss the statistical distributions of cracks width and separation between two adjacent cracks. We also study the correlations between these two quantities. Our results are compared to the predictions of existing models. Finally, a comparison with another kind of clay is made. [less ▲]

Detailed reference viewed: 19 (0 ULiège)
See detailexperimental study of drying kinetics of a building material
Kahlerras, Loubna ULiege

Scientific conference (2014, October 23)

Detailed reference viewed: 16 (0 ULiège)
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See detailExperimental study of GdBCO pellets subjected to small transverse alternating magnetic fields at very low frequency: Evidence of saturation of the axial magnetization decay
Fagnard, Jean-François ULiege; Kirsch, Sébastien; Teshima, Hidekazu et al

Poster (2014, August)

Due to their ability to trap large magnetic inductions, bulk (RE)BCO materials (where RE stands for rare-earth ion) can be used as powerful permanent magnets. Previous works have shown that the ... [more ▼]

Due to their ability to trap large magnetic inductions, bulk (RE)BCO materials (where RE stands for rare-earth ion) can be used as powerful permanent magnets. Previous works have shown that the magnetization of a bulk superconductor can be destroyed by the presence of an ac magnetic field applied transversally to the remnant magnetization. Up to now, the exact process of this magnetization decay is not completely understood, i.e. it is not clear if the decay is only due to a redistribution of the superconducting currents in the volume of the pellet or if a part of this decay can be due to self-heating of the material subjected to the ac excitation. In this work, we carry out, in liquid nitrogen, measurements for which the ac field is applied during several hours. We investigate the range of relatively small ac field amplitudes (in comparison to the penetration field of the pellet) and in a wide range of low frequencies (1mHz–20Hz). The waveform of the parasitic ac field is either sinusoidal or triangular, the latter corresponding to a constant variation of the applied induction, dBapp/dt. The studied sample is a cylindrical bulk single grain GdBCO pellet whose dimensions are 10mm in height and 15mm in diameter. Thermocouples are placed on the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to measure the local magnetic induction normal to the surface (and parallel to the transverse ac field). The results show first that, for a given number of applied triangular transverse cycles, lower values of dBapp/dt induce larger magnetization decays.. An important feature of practical interest is that, after a very large number of cycles (>10000) which cause the removal of a given amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. The thermocouples show no evidence of self-heating in that range of amplitude and frequency of the applied field. Acknowledgements We thank the FRS-FNRS, the Communauté Française de Belgique for cryofluid, travel and equipment grants, under reference ARC 11/16-03. [less ▲]

Detailed reference viewed: 10 (4 ULiège)
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Peer Reviewed
See detailExperimental study of granular compaction dynamics at different scales: Grain mobility, hexagonal domains, and packing fraction
Lumay, Geoffroy ULiege; Vandewalle, Nicolas ULiege

in Physical Review Letters (2005), 95(2), 28002

We present an original experimental study of the compaction dynamics for two-dimensional granular systems. Compaction dynamics is measured at three different scales: the macroscopic scale through the ... [more ▼]

We present an original experimental study of the compaction dynamics for two-dimensional granular systems. Compaction dynamics is measured at three different scales: the macroscopic scale through the normalized packing fraction rho, the mesoscopic scale through the normalized fraction phi of hexagonal domains in the system, and the microscopic scale through the grain mobility mu. Moreover, the hexagonal domains are found to obey a growth process dominated by the displacement of domain boundaries. A global picture of compaction dynamics relevant at each scale is proposed. [less ▲]

Detailed reference viewed: 20 (2 ULiège)
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See detailExperimental study of isolated response curves in a two-degree-of-freedom nonlinear system
Detroux, Thibaut ULiege; Noël, Jean-Philippe ULiege; Kerschen, Gaëtan ULiege et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXIV (2016, January)

In the present paper, the observation and characterization of isolated response curves (IRCs) are experimentally reported in the case of a nonlinear system consisting of two masses sliding on an ... [more ▼]

In the present paper, the observation and characterization of isolated response curves (IRCs) are experimentally reported in the case of a nonlinear system consisting of two masses sliding on an horizontal guide. Transverse springs are attached to one mass to provide the nonlinear restoring force, and a harmonic motion of the complete system is imposed by prescribing the displacement of their supports. The existence of an IRC is related to a 3:1 internal resonance between the two modes of the system. The observed IRC is studied in detached and merged conditions using swept-sine excitations and system perturbations. [less ▲]

Detailed reference viewed: 74 (19 ULiège)
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See detailExperimental study of journal bearings
Hanocq, Charles ULiege

in Proceedings of the general discussion on lubrication & lubricants : 13th-15th October 1937. Volume 2 (1937)

Detailed reference viewed: 6 (0 ULiège)
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See detailExperimental study of loss of head in a closed pipe carrying clay slurry
Hanocq, Charles ULiege

in Transactions of the American Society of Mechanical Engineers (1929), 51(8), 75-78

Detailed reference viewed: 5 (0 ULiège)
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See detailExperimental study of methods to increase the shielded volume in passive superconducting magnetic screens
Wera, Laurent ULiege

Doctoral thesis (2017)

This thesis is dedicated to the experimental study of methods to increase the shielded volume in passive magnetic shields made of high temperature superconductors (HTS). Two main approaches are ... [more ▼]

This thesis is dedicated to the experimental study of methods to increase the shielded volume in passive magnetic shields made of high temperature superconductors (HTS). Two main approaches are investigated. The first approach is to study how the size of the shield can be increased. The second is to study how the shielded volume can be extended in a shield of given size. In the first approach, we study how large-scale or scalable magnetic shields could be obtained. Scalability means the possibility of building magnetic shields of various dimensions by keeping the same fabrication technique. First, we study in detail the shielding properties and the behaviour of shields made as an assembly of superconducting coated conductor loops, obtained from second generation superconducting YBa2Cu3O7 coated conductor tapes that are commercially available. We show that such shields are an excellent alternative to bulk magnetic shields for shielding large volumes and fields of the order of 50 mT at 77 K. Different dimensions can be easily obtained by adapting the number and the length of the coated conductor tapes. This technique is shown to be very promising for building easily large size magnetic shields. However, unlike bulk magnetic shields, the shielding efficiency decreases rapidly when the applied field is no longer parallel to the main axis of the shield. The results in these configurations are analyzed to investigate the role played by the peculiar eye-shape cross-section of the shield on the various shielding current loops. We show that in the transverse field configuration, the structure can be used to locally modify the direction of the applied field. Finally, we take advantage of the scalability of such shields to build and study a triaxial structure that is able to attenuate a magnetic field of arbitrary orientation. Next we study the superconducting properties and the shielding efficiency of YBa2Cu3O7 superconducting tubes made by two distinct fabrication techniques allowing large-scale or scalable magnetic shields to be obtained. The first technique is the electrophoretic deposition (EPD) which consists in the deposition of a superconducting thick-film (about 100 μm thick) on a metallic substrate. Compared to previous studies, our results show an improvement of the shielding properties and open encouraging prospects for a future development of magnetic shields made by EPD. For the second technique, the shield is obtained by the pulsed-laser deposition (PLD) of a superconducting thin layer (about 1 μm thick) on a textured metallic substrate. In the case where a continuous layer (i.e. joint-free) has been deposited successfully, we show that the persistent current flowing in the superconducting layer has a critical current density close to that of the commercial YBa2Cu3O7 coated conductor tapes, and point out the similarities with the coated conductor structures studied previously. We also consider a similar material containing joints and compare their impact on the magnetic shielding in various configurations (DC/AC, axial/transverse). The results highlight the profound impact of nΩ level joint resistances on the superconducting shielding. For the second approach used in this thesis, we study how to increase the shielded volume in HTS bulk magnetic shields of given dimensions. In the case of non-textured polycrystalline superconductors (Bi2Sr2Ca2Cu3O10 commercial tubes), we analyse the improvements resulting from closing one or both ends of a tube by a cap made of the same material. In this configuration the joint between the cap and the tube is non-superconducting. Numerical simulations are used to see how the volume can be further increased by increasing the thickness of the cap or increasing its critical current density. Then, we study the shielding efficiency of a melt-textured bulk YBa2Cu3O7 superconducting tube closed at one extremity with a cap in which the joint between the cap and the tube is superconducting. Our results show that such a tube can shield axial fields in excess of 1 tesla at 20 K and is therefore useful for shielding small volumes against high magnetic fields. The beneficial effect of a cap is also studied in the transverse field configuration. We show experimentally and with help of numerical simulations that, in this case, the superconducting character of the joint between the tube and the cap is mandatory. In addition to the increase of the shielded volume, this thesis also addresses another problem relevant to future shielding applications. We investigate experimentally the effect of a magnetic field trapped initially in a bulk HTS hollow cylinder on its shielding performances. In the studied configurations, the initial applied field and the field to be shielded are mutually orthogonal. Remarkably the shielding properties are not affected provided the flux lines have not reached the inner hollow part of the cylinder. A trapped field inside the shield, however, is found to affect the threshold induction significantly. We then study how to efficiently demagnetize the superconducting tube without heating it above its critical temperature. By applying a single demagnetization cycle of adequate amplitude, we show that the initial shielding properties can be recovered. [less ▲]

Detailed reference viewed: 29 (11 ULiège)