The Experts below are selected from a list of 3123 Experts worldwide ranked by ideXlab platform
Benjamin J Eggleton - One of the best experts on this subject based on the ideXlab platform.
-
bit error ratio improvement with 2r optical Regenerators
IEEE Photonics Technology Letters, 2005Co-Authors: Martin Rochette, J N Kutz, Justin L Blows, David J Moss, Benjamin J EggletonAbstract:We show that an all-optical optical regenerator can improve the bit-error ratio (BER) of a signal passing through it only if the regenerator has different power transfer functions for the logical ones and logical zeros. A regenerator that operates with a single transfer function-which constitute most of optical Regenerators reported in the literature-cannot improve the BER, but can only reduce the BER degradation when, for example, placed before optical amplifiers. Of all the optical Regenerators reported to date, only the one proposed by Mamyshev, based on filtering a self-phase modulated signal, has different transfer functions for the logical ones and the logical zeros. This makes the Mamyshev scheme a superior candidate for ultrahigh-speed all-optical regeneration.
-
bit error ratio improvement with 2r optical Regenerators
IEEE Photonics Technology Letters, 2005Co-Authors: Martin Rochette, J N Kutz, Justin L Blows, David J Moss, Joe T Mok, Benjamin J EggletonAbstract:We show that an all-optical optical regenerator can improve the bit-error ratio (BER) of a signal passing through it only if the regenerator has different power transfer functions for the logical ones and logical zeros. A regenerator that operates with a single transfer function-which constitute most of optical Regenerators reported in the literature-cannot improve the BER, but can only reduce the BER degradation when, for example, placed before optical amplifiers. Of all the optical Regenerators reported to date, only the one proposed by Mamyshev, based on filtering a self-phase modulated signal, has different transfer functions for the logical ones and the logical zeros. This makes the Mamyshev scheme a superior candidate for ultrahigh-speed all-optical regeneration.
-
investigation of group delay ripple distorted signals transmitted through all optical 2r Regenerators
Optics Express, 2004Co-Authors: Joe T Mok, Justin L Blows, Benjamin J EggletonAbstract:We investigate the use of all-optical Regenerators to correct pulse distortions introduced by group delay ripple. Group delay ripple creates unwanted satellite pulses and intensity fluctuations. By placing an all-optical regenerator after a device that introduces group delay ripple, we show that the signal distortions can be effectively reduced. This has the benefit of opening the signal eye at the receiver. The performances of both self-phase modulation and four-wave mixing based Regenerators in reducing ripple induced system penalties are examined. We find that the regenerator based on four-wave mixing achieves better suppression of group delay ripple distortions than the self-phase modulation based alternative. The eye closure penalty introduced by group delay ripple is reduced by the four-wave mixing based regenerator by 1dB.
Jader R Barbosa - One of the best experts on this subject based on the ideXlab platform.
-
Influence of inlet flow maldistribution and carryover losses on the performance of thermal Regenerators
Applied Thermal Engineering, 2018Co-Authors: P V Trevizoli, Guilherme F Peixer, Matheus S. Capovilla, Alan T.d. Nakashima, Jaime Lozano, Jader R BarbosaAbstract:Abstract Void (dead) volumes represent a penalty to the thermal performance of Active Magnetic Regenerators (AMR). While much effort has been put in designing AMRs with small void volumes, in most designs, penalties associated with inlet flow maldistribution and pressure loss may increase with the reduction of the void volumes. In this work, an experimental evaluation of the combined effect of void volume and inlet flow maldistribution is carried out. The analysis is performed based on the regenerator thermal effectiveness determined experimentally in a passive regenerator test apparatus. The results show that the negative impact of inlet flow maldistribution on the regenerator effectiveness is more significant than that of the void volume.
-
thermal hydraulic behavior and influence of carryover losses in oscillating flow Regenerators
International Journal of Thermal Sciences, 2017Co-Authors: P V Trevizoli, Jader R BarbosaAbstract:Abstract Thermal Regenerators that use a liquid as the heat transfer fluid are encountered in active-caloric (e.g., magnetocaloric, electrocaloric, elastocaloric) coolers/heat pumps and other applications. In this study, we present a mathematical model, its numerical implementation and comparisons with an extensive experimental database on the thermal performance of packed bed Regenerators composed of stainless steel spheres [1]. The regenerator model consists of the one-dimensional Brinkman-Forchheimer equation to describe the fluid flow in the porous matrix and coupled energy equations to determine the temperatures in the fluid and solid phases. A mathematical model for the so-called carryover (leakage) losses provoked by the dead (void) volumes on each side of the regenerator was implemented to improve the thermal effectiveness prediction. A good agreement between the mathematical model and the experimental data was observed, enabling an accurate quantification of thermal-hydraulic losses. The mathematical model and its results can be extended to and incorporated into performance analyses of active magnetic Regenerators.
-
thermal hydraulic evaluation of oscillating flow Regenerators using water experimental analysis of packed beds of spheres
International Journal of Heat and Mass Transfer, 2016Co-Authors: P V Trevizoli, Guilherme F Peixer, Jader R BarbosaAbstract:Thermal Regenerators that use liquid heat transfer fluids are being researched for their application in active caloric cooling/heat pumping systems. The performance of active caloric devices is significantly influenced by the regenerator thermal effectiveness and by viscous losses. The present paper is the first part of a study on the thermal–hydraulic evaluation of packed bed Regenerators that use water as a thermal fluid. Here, a detailed experimental analysis of the thermal–hydraulic performance of regenerative matrices composed of packed beds of stainless steel spheres is carried out. A laboratory apparatus was developed to quantify the viscous losses and thermal effectiveness in oscillating-flow Regenerators that use water as the heat transfer fluid. Operating parameters such as frequency and mass flow rate were varied to cover broad ranges of utilization and number of transfer units (NTU). The diameter of the spherical particles and the dimensions of the regenerator housing were also changed in order to evaluate their influence on the behavior of the time-dependent and time-average performance parameters.
-
entropy generation minimization analysis of oscillating flow Regenerators
International Journal of Heat and Mass Transfer, 2015Co-Authors: P V Trevizoli, Jader R BarbosaAbstract:Abstract The thermodynamic efficiencies of regenerative cooling cycles are directly linked to the heat transfer effectiveness and thermal losses in the regenerator. This paper proposes a performance analysis for Regenerators based on the Entropy Generation Minimization (EGM) theory. The mathematical model consists of the one-dimensional Brinkman–Forchheimer equation to describe the fluid flow in the porous matrix and coupled energy equations to determine the temperatures in the fluid and solid phases. The cycle-average entropy generation contributions due to axial heat conduction, fluid friction and interstitial heat transfer are calculated. The influences of parameters such as the mass flow rate, operating frequency, regenerator cross sectional area, housing aspect ratio, utilization factor and particle diameter are evaluated according to the variable geometry (VG) and fixed face (cross-section) area (FA) performance evaluation criteria (PEC). Optimal regenerator configurations are found for each PEC for flow rates between 40 and 300 kg/h (0.01 and 0.083 kg/s) and frequencies between 1 and 4 Hz with constraints of regenerator effectiveness equal to 95% and temperature span of 40 K.
-
experimental assessment of the thermal hydraulic performance of packed sphere oscillating flow Regenerators using water
Experimental Thermal and Fluid Science, 2014Co-Authors: P V Trevizoli, A Rowe, Yifeng Liu, A Tura, Jader R BarbosaAbstract:Abstract Regenerators are storage-type heat exchangers with a wide-range application in thermal systems. In refrigeration, they can be used as passive thermal storage devices in Stirling and pulse-tube coolers, or as active magnetocaloric Regenerators in magnetic refrigerators. In either case, the performance of the cooling system is significantly influenced by the regenerator thermal effectiveness and by viscous losses. A laboratory apparatus for testing passive Regenerators that uses water as the thermal fluid was developed aiming at quantifying the fluid pumping power and the regenerator heat transfer effectiveness as a function of operating parameters such as frequency and thermal capacity ratio (utilization factor) for different regenerative materials and packing geometries. In the present paper, the experimental rig, data processing and test results obtained for packed beds of stainless steel, lead and gadolinium spheres with different particle diameters are described and discussed.
P V Trevizoli - One of the best experts on this subject based on the ideXlab platform.
-
experimental characterization of multilayer active magnetic Regenerators using first order materials multiple points of equilibrium
Journal of Applied Physics, 2018Co-Authors: P Govindappa, P V Trevizoli, I Niknia, T V Christiaanse, R Teyber, A RoweAbstract:Multiplepoints of equilibrium (MPE) have recently been observed in single layer active magnetic Regenerators (AMRs) using first order magnetic materials (FOMs). Here, we describe experiments using three multilayer MnFeP1-xAsx FOM regenerator beds characterized under a range of applied loads and rejection temperatures. Thermal performance and the impacts of MPE are evaluated via heating and cooling experiments where the rejection (hot side) temperature is varied in a range from 283 K to 300 K. With fixed operating conditions, we find multiple points of equilibrium for steady-state spans as a function of warm rejection temperature. The results indicate a significant impact of MPE on the heating and cooling temperature span for a multilayer MnFeP1-xAsx FOM regenerator. Unlike single material FOM tests where MPEs tend to disappear as load is increased (or span reduced), with the layered AMRs, MPEs can be significant even with small temperature span conditions.Multiplepoints of equilibrium (MPE) have recently been observed in single layer active magnetic Regenerators (AMRs) using first order magnetic materials (FOMs). Here, we describe experiments using three multilayer MnFeP1-xAsx FOM regenerator beds characterized under a range of applied loads and rejection temperatures. Thermal performance and the impacts of MPE are evaluated via heating and cooling experiments where the rejection (hot side) temperature is varied in a range from 283 K to 300 K. With fixed operating conditions, we find multiple points of equilibrium for steady-state spans as a function of warm rejection temperature. The results indicate a significant impact of MPE on the heating and cooling temperature span for a multilayer MnFeP1-xAsx FOM regenerator. Unlike single material FOM tests where MPEs tend to disappear as load is increased (or span reduced), with the layered AMRs, MPEs can be significant even with small temperature span conditions.
-
Influence of inlet flow maldistribution and carryover losses on the performance of thermal Regenerators
Applied Thermal Engineering, 2018Co-Authors: P V Trevizoli, Guilherme F Peixer, Matheus S. Capovilla, Alan T.d. Nakashima, Jaime Lozano, Jader R BarbosaAbstract:Abstract Void (dead) volumes represent a penalty to the thermal performance of Active Magnetic Regenerators (AMR). While much effort has been put in designing AMRs with small void volumes, in most designs, penalties associated with inlet flow maldistribution and pressure loss may increase with the reduction of the void volumes. In this work, an experimental evaluation of the combined effect of void volume and inlet flow maldistribution is carried out. The analysis is performed based on the regenerator thermal effectiveness determined experimentally in a passive regenerator test apparatus. The results show that the negative impact of inlet flow maldistribution on the regenerator effectiveness is more significant than that of the void volume.
-
thermal hydraulic behavior and influence of carryover losses in oscillating flow Regenerators
International Journal of Thermal Sciences, 2017Co-Authors: P V Trevizoli, Jader R BarbosaAbstract:Abstract Thermal Regenerators that use a liquid as the heat transfer fluid are encountered in active-caloric (e.g., magnetocaloric, electrocaloric, elastocaloric) coolers/heat pumps and other applications. In this study, we present a mathematical model, its numerical implementation and comparisons with an extensive experimental database on the thermal performance of packed bed Regenerators composed of stainless steel spheres [1]. The regenerator model consists of the one-dimensional Brinkman-Forchheimer equation to describe the fluid flow in the porous matrix and coupled energy equations to determine the temperatures in the fluid and solid phases. A mathematical model for the so-called carryover (leakage) losses provoked by the dead (void) volumes on each side of the regenerator was implemented to improve the thermal effectiveness prediction. A good agreement between the mathematical model and the experimental data was observed, enabling an accurate quantification of thermal-hydraulic losses. The mathematical model and its results can be extended to and incorporated into performance analyses of active magnetic Regenerators.
-
performance evaluation of two layer active magnetic Regenerators with second order magnetocaloric materials
Applied Thermal Engineering, 2016Co-Authors: R Teyber, P V Trevizoli, P Govindappa, I Niknia, T V Christiaanse, A RoweAbstract:Abstract Magnetic heat pumps and cooling systems typically use a magnetocaloric material in an active magnetic regenerator (AMR) cycle for application near room temperature. One method of improving AMR performance is to layer Regenerators with spatially varying Curie (or transition) temperatures. To study the impact of layering on AMR performance, four regenerator compositions comprised of two-layers are experimentally tested with interface temperature measurements. Each regenerator uses Gd as the layer with the highest Curie temperature; the second layer uses Gd and three compositions of Gd 1− x Y x . The four Regenerators are the same size and are tested using three different rejection temperatures and displaced volumes. Numerical simulations are in good agreement with the experimental results. The two-layer Regenerators present the largest performance improvements for the no-load conditions and, in general, develop the peak exergetic cooling power for almost all operating conditions.
-
thermal hydraulic evaluation of oscillating flow Regenerators using water experimental analysis of packed beds of spheres
International Journal of Heat and Mass Transfer, 2016Co-Authors: P V Trevizoli, Guilherme F Peixer, Jader R BarbosaAbstract:Thermal Regenerators that use liquid heat transfer fluids are being researched for their application in active caloric cooling/heat pumping systems. The performance of active caloric devices is significantly influenced by the regenerator thermal effectiveness and by viscous losses. The present paper is the first part of a study on the thermal–hydraulic evaluation of packed bed Regenerators that use water as a thermal fluid. Here, a detailed experimental analysis of the thermal–hydraulic performance of regenerative matrices composed of packed beds of stainless steel spheres is carried out. A laboratory apparatus was developed to quantify the viscous losses and thermal effectiveness in oscillating-flow Regenerators that use water as the heat transfer fluid. Operating parameters such as frequency and mass flow rate were varied to cover broad ranges of utilization and number of transfer units (NTU). The diameter of the spherical particles and the dimensions of the regenerator housing were also changed in order to evaluate their influence on the behavior of the time-dependent and time-average performance parameters.
Lionel Provost - One of the best experts on this subject based on the ideXlab platform.
-
Generation of localized pulses from incoherent wave in optical fiber lines made of concatenated Mamyshev Regenerators
Journal of the Optical Society of America B, 2008Co-Authors: Stéphane Pitois, Christophe Finot, Lionel Provost, D.j RichardsonAbstract:We investigate the novel properties of optical fiber lines made of Mamyshev Regenerators (MRs) based on self-phase modulation and subsequent spectral filtering. In particular, we show that such a regenerator line can be used to generate random sequences of optical pulses from an incoherent wave. This behavior is related to the existence of stable eigenpulses that can propagate unchanged through the regenerator line and act as attractors for incoming pulses. By changing the regenerator parameters, we also report the existence of multiple eigenpulses and limit cycles. Finally, we demonstrate that MRs could be used as efficient nonlinear gates in fiber laser cavities.
-
Asymptotic properties of incoherent waves propagating in an all-optical regenerator line
Optics Letters, 2007Co-Authors: Stéphane Pitois, Christophe Finot, Lionel ProvostAbstract:We present an original method to generate optical pulse trains with random time-interval values from incoherent broadband sources. More precisely, our technique relies on the remarkable properties of a line made of cascaded self-phase modulation-based optical Regenerators. Depending on the regenerator parameters, various regimes with noticeably different physical behaviors can be reported.
-
design scaling rules for 2r optical self phase modulation based Regenerators
Optics Express, 2007Co-Authors: Lionel Provost, Christophe Finot, Kazunori Mukasa, P Petropoulos, D.j RichardsonAbstract:We present simple scaling rules to optimize the design of 2R optical Regenerators relying on Self-Phase Modulation in the normal dispersion regime and associated offset spectral filtering. A global design map is derived which relates both the physical parameters of the regenerator and the properties of the incoming signal to the regeneration performance. The operational conditions for optimum noise rejection are identified using this map and a detailed analysis of the system behavior under these conditions presented. Finally, we demonstrate application of the general design map to the design of a regenerator for a specific 160 Gb/s system.
-
generalisation and experimental validation of design rules for self phase modulation based 2r Regenerators
Optical Fiber Communication Conference, 2007Co-Authors: Lionel Provost, Christophe Finot, Kazunori Mukasa, P Petropoulos, D.j RichardsonAbstract:We report the design of 2R-Regenerators based on self-phase modulation in lossy fibers. We experimentally demonstrate the applicability of the proposed scaling rules and present detailed characterization of the pulse characteristics at the regenerator output.
Muhammad Kamran - One of the best experts on this subject based on the ideXlab platform.
-
performance optimisation of room temperature magnetic refrigerator with layered multi material microchannel Regenerators
International Journal of Refrigeration-revue Internationale Du Froid, 2016Co-Authors: Muhammad Kamran, Hassan Ali, Muhammad Farhan, Yong Bai Tang, Yungui Chen, Hua Sheng WangAbstract:Abstract A hybrid numerical model of the magnetic refrigerator with multi-material microchannel regenerator has been developed. The magnetocaloric effect was implemented using instantaneous temperature rise/drop (discrete method). Two pipe-in-pipe heat exchangers at two ends of the regenerator were treated using e-NTU method. The commercially available compounds of LaFe13-x-yCoxSiy as well as hypothetical compounds of Gadolinium were considered as the magnetocaloric materials (MCMs) with different Curie temperatures. The predicted results of the present work for parallel-plate Regenerators employing different compounds of LaFe13-x-yCoxSiy were broadly in good agreement with the available experimental data. The cooling capacity increases as the number of MCMs increase. However, for a given length of regenerator, an optimum number of MCMs was seen yielding the maximum performance of the refrigerator. For a given number of MCMs, a smaller Curie temperature difference ΔTCu between the MCMs was found to give higher performance.
-
numerical investigation of room temperature magnetic refrigerator using microchannel Regenerators
Applied Thermal Engineering, 2016Co-Authors: Muhammad Kamran, Yong Bai Tang, Yungui Chen, Jie Sun, Hua Sheng WangAbstract:Abstract The paper reports numerical investigation of room temperature, active magnetocaloric regeneration (AMR) refrigerators/heat pumps using microchannel regenerator. The microchannel Regenerators are made of a magnetocaloric material (MCM), Gd, with diameter of the circular channels ranging from 0.7 mm to 2.0 mm. Water, the working fluid, oscillates in the regenerator loop driven by two piston-cylinder displacers operating in a range of mass flow rates. Three dimensional conjugated fluid convection and conduction heat transfer in the microchannel regenerator was modeled and numerically simulated using ANSYS Fluent. The magnetocaloric effect (MCE) was incorporated into conservation of energy using a discrete method to simulate the magnetization and demagnetization of the MCM. The hot and cold end heat exchangers were treated with the e – NTU method. Effects of utilization and porosity of the microchannel regenerator and cycle frequency on the cooling capacity and temperature span were examined. When the utilization, porosity and cycle frequency are 0.2, 0.5 and 5.0 Hz, respectively, the predicted maximum cooling capacity was about 22 W for a 0.8 T variation in intensity of magnetic field. The effects of magnetic field intensity, reservoir temperature span and flow rate profile on the refrigeration performance were also investigated. The performance of the microchannel regenerator is compared with that of the parallel plate regenerator for the no-load temperature span, cooling capacity and pumping power. Under specific geometric and operating conditions, the microchannel regenerator shows better performance than the parallel-plate one.
