scholarly journals Gas-Solid Flow in a Fluidized-Particle Tubular Solar Receiver: Off-Sun Experimental Flow Regimes Characterization

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7392
Author(s):  
Ronny Gueguen ◽  
Guillaume Sahuquet ◽  
Samuel Mer ◽  
Adrien Toutant ◽  
Françoise Bataille ◽  
...  
Keyword(s):  
Acquisition Time ◽  
Internal Diameter ◽  
Short Acquisition Time ◽  
Wide Range ◽  
Temporal Pressure ◽  
Secondary Air ◽  
Fluidized Particle ◽  
Solar Power Tower ◽  
Fluidized Particles ◽  
Solar Receiver

The fluidized particle-in-tube solar receiver concept is promoted as an attractive solution for heating particles at high temperature in the context of the next generation of solar power tower. Similar to most existing central solar receivers, the irradiated part of the system, the absorber, is composed of tubes in which circulate the fluidized particles. In this concept, the bottom tip of the tubes is immersed in a fluidized bed generated in a vessel named the dispenser. A secondary air injection, called aeration, is added at the bottom of the tube to stabilize the flow. Contrary to risers, the particle mass flow rate is controlled by a combination of the overpressure in the dispenser and the aeration air velocity in the tube. This is an originality of the system that justifies a specific study of the fluidization regimes in a wide range of operating parameters. Moreover, due to the high value of the aspect ratio, the particle flow structure varies along the tube. Experiments were conducted with Geldart Group A particles at ambient temperature with a 0.045 m internal diameter and 3 m long tube. Various temporal pressure signal processing methods, applied in the case of classical risers, are applied. Over a short acquisition time, a cross-reference of the results is necessary to identify and characterize the fluidization regimes. Bubbling, slugging, turbulent and fast fluidization regimes are encountered and the two operation modes, without and with particle circulation, are compared.

scholarly journals Aiming Strategy on a Prototype-Scale Solar Receiver: Coupling of Tabu Search, Ray-Tracing and Thermal Models

2021 ◽  
Vol 13 (7) ◽  
pp. 3920
Author(s):  
Benjamin Grange ◽  
Gilles Flamant
Keyword(s):  
Tabu Search ◽  
Ray Tracing ◽  
Wall Temperature ◽  
Gradual Increase ◽  
Particle Temperature ◽  
Outlet Temperature ◽  
Operation Conditions ◽  
Start Up ◽  
Fluidized Particle ◽  
Solar Receiver

An aiming point strategy applied to a prototype-scale power tower is analyzed in this paper to define the operation conditions and to preserve the lifetime of the solar receiver developed in the framework of the Next-commercial solar power (CSP) H2020 project. This innovative solar receiver involves the fluidized particle-in-tube concept. The aiming solution is compared to the case without the aiming strategy. Due to the complex tubular geometry of the receiver, results of the Tabu search for the aiming point strategy are combined with a ray-tracing software, and these results are then coupled with a simplified thermal model of the receiver to evaluate its performance. Daily and hourly aiming strategies are compared, and different objective normalized flux distributions are applied to quantify their influence on the receiver wall temperature distribution, thermal efficiency and particle outlet temperature. A gradual increase in the solar incident power on the receiver is analyzed in order to keep a uniform outlet particle temperature during the start-up. Results show that a tradeoff must be respected between wall temperature and particle outlet temperature.

Experimental Investigation of Turbine Stage Flow Field and Performance at Varying Cavity Purge Rates and Operating Speeds

2016 ◽  
Author(s):  
Johan Dahlqvist ◽  
Jens Fridh
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
High Speed ◽  
Control Volume ◽  
Spatial Average ◽  
Turbine Stage ◽  
Wide Range ◽  
Annulus Flow ◽  
Purge Flow ◽  
Secondary Air

The aspect of hub cavity purge has been investigated in a high-pressure axial low-reaction turbine stage. The cavity purge is an important part of the secondary air system, used to isolate the hot main annulus flow from cavities below the hub level. A full-scale cold-flow experimental rig featuring a rotating stage was used in the investigation, quantifying main annulus flow field impact with respect to purge flow rate as it was injected upstream of the rotor. Five operating speeds were investigated of which three with respect to purge flow, namely a high loading case, the peak efficiency, and a high speed case. At each of these operating speeds, the amount of purge flow was varied across a very wide range of ejection rates. Observing the effect of the purge rate on measurement plane averaged parameters, a minor outlet swirl decrease is seen with increasing purge flow for each of the operating speeds while the Mach number is constant. The prominent effect due to purge is seen in the efficiency, showing a similar linear sensitivity to purge for the investigated speeds. An attempt is made to predict the efficiency loss with control volume analysis and entropy production. While spatial average values of swirl and Mach number are essentially unaffected by purge injection, important spanwise variations are observed and highlighted. The secondary flow structure is strengthened in the hub region, leading to a generally increased over-turning and lowered flow velocity. Meanwhile, the added volume flow through the rotor leads to higher outlet flow velocities visible in the tip region, and an associated decreased turning. A radial efficiency distribution is utilized, showing increased impact with increasing rotor speed.

Innovative Volumetric Solar Receiver Micro-Design Based on Numerical Predictions

2015 ◽  
Author(s):  
Raffaele Capuano ◽  
Thomas Fend ◽  
Bernhard Hoffschmidt ◽  
Robert Pitz-Paal
Keyword(s):  
Solar Radiation ◽  
Energy Demand ◽  
Large Scale ◽  
Solar Power ◽  
Numerical Models ◽  
Numerical Predictions ◽  
Proper Design ◽  
Global Increase ◽  
Solar Power Tower ◽  
Solar Receiver

Due to the continuous global increase in energy demand, Concentrated Solar Power (CSP) represents an excellent alternative, or add-on to existing systems for the production of energy on a large scale. In some of these systems, the Solar Power Tower plants (SPT), the conversion of solar radiation into heat occurs in certain components defined as solar receivers, placed in correspondence of the focus of the reflected sunlight. In a particular type of solar receivers, defined as volumetric, the use of porous materials is foreseen. These receivers are characterized by a porous structure called absorber. The latter, hit by the reflected solar radiation, transfers the heat to the evolving fluid, generally air subject to natural convection. The proper design of these elements is essential in order to achieve high efficiencies, making such structures extremely beneficial for the overall performances of the energy production process. In the following study, a parametric analysis and an optimized characterization of the structure have been performed with the use of self-developed numerical models. The knowledge and results gained through this study have been used to define an optimization path in order to improve the absorber microstructure, starting from the current in-house state-of-the-art technology until obtaining a new advanced geometry.

scholarly journals RARE-59. CARDIAC REMODELING IN PATIENTS WITH CHILDHOOD-ONSET CRANIOPHARYNGIOMA – RESULTS OF HIT-ENDO AND KRANIOPHARYNGEOM 2000/2007

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii455-iii455
Author(s):  
Panjarat Sowithayasakul ◽  
Leona Katharin Buschmann ◽  
Svenja Boekhoff ◽  
Hermann L Müller
Keyword(s):  
Cardiac Remodeling ◽  
Disease Duration ◽  
Interventricular Septum ◽  
Left Ventricular ◽  
Internal Diameter ◽  
Functional Impairments ◽  
Childhood Onset ◽  
Anthropometric Parameters ◽  
Hypothalamic Obesity ◽  
Wide Range

Abstract BACKGROUND Hypothalamic obesity caused by childhood–onset craniopharyngioma results in long–term cardiovascular morbidity. Knowledge about clinical markers and risk factors is rare. PATIENTS AND METHODS A cross–sectional study on transthoracic echocardiographic parameters was performed to determine the associations with clinical and anthropometric parameters in 36 patients with childhood-onset adamantinomatous craniopharyngioma. RESULTS Body mass index (BMI) correlated with the thickness of interventricular septum in diastole (IVSd) (r=0.604, p<0.001) and left ventricular diastolic posterior wall in diastole (LVPWd) (r=0.460, p=0.011). Due to wide range of disease duration, 17 pediatric and 19 adult patients were analyzed separately. In the adult subgroup (age at study ≥18 years), BMI correlated with IVSd (r=0.707, p=0.003), LVPWd (r=0.592, p=0.020) and left ventricular internal diameter in diastole (LVIDd) (r=0.571, p=0.026). In the pediatric subgroup (age at study <18 years), no correlation between cardiac parameters and BMI was observed. Only LVIDd correlated with disease duration (r=0.645, p<0.001). All cardiac functions were within the normal range, indicating no association with severe functional impairments. CONCLUSIONS Cardiac remodeling in patients with childhood-onset craniopharyngioma correlates with the degree of hypothalamic obesity and disease duration. However, echocardiography has limited sensitivity in craniopharyngioma patients with obesity, so cardiac magnetic resonance imaging (MRI) should be considered as an alternative diagnostic approach for patients with craniopharyngioma and hypothalamic obesity.

scholarly journals Evaluation of Nonradiative Clinical Imaging Techniques for the Longitudinal Assessment of Tumour Growth in Murine CT26 Colon Carcinoma

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Johanne Seguin ◽  
Bich-Thuy Doan ◽  
Heldmuth Latorre Ossa ◽  
Lauriane Jugé ◽  
Jean-Luc Gennisson ◽  
...  
Keyword(s):  
Colon Carcinoma ◽  
Tumour Growth ◽  
Imaging Techniques ◽  
Acquisition Time ◽  
Longitudinal Assessment ◽  
Resonance Imaging ◽  
Orthotopic Model ◽  
Short Acquisition Time ◽  
Magnetic Resonance Imaging Mri ◽  
Good Delineation

Background and Objectives. To determine the most appropriate technique for tumour followup in experimental therapeutics, we compared ultrasound (US) and magnetic resonance imaging (MRI) to characterize ectopic and orthotopic colon carcinoma models. Methods. CT26 tumours were implanted subcutaneously (s.c.) in Balb/c mice for the ectopic model or into the caecum for the orthotopic model. Tumours were evaluated by histology, spectrofluorescence, MRI, and US. Results. Histology of CT26 tumour showed homogeneously dispersed cancer cells and blood vessels. The visualization of the vascular network using labelled albumin showed that CT26 tumours were highly vascularized and disorganized. MRI allowed high-resolution and accurate 3D tumour measurements and provided additional anatomical and functional information. Noninvasive US imaging allowed good delineation of tumours despite an hypoechogenic signal. Monitoring of tumour growth with US could be accomplished as early as 5 days after implantation with a shorter acquisition time (<5 min) compared to MRI. Conclusion. MRI and US afforded excellent noninvasive imaging techniques to accurately follow tumour growth of ectopic and orthotopic CT26 tumours. These two techniques can be appropriately used for tumour treatment followup, with a preference for US imaging, due to its short acquisition time and simplicity of use.

scholarly journals Time-resolved mid-infrared dual-comb spectroscopy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Muhammad A. Abbas ◽  
Qing Pan ◽  
Julien Mandon ◽  
Simona M. Cristescu ◽  
Frans J. M. Harren ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Vibrational Excitation ◽  
High Spectral Resolution ◽  
Acquisition Time ◽  
Time Resolved ◽  
Short Acquisition Time ◽  
Mid Infrared ◽  
Infrared Wavelength ◽  
Potential Applications ◽  
Kinetics Of

AbstractDual-comb spectroscopy can provide broad spectral bandwidth and high spectral resolution in a short acquisition time, enabling time-resolved measurements. Specifically, spectroscopy in the mid-infrared wavelength range is of particular interest, since most of the molecules have their strongest rotational-vibrational transitions in this “fingerprint” region. Here we report time-resolved mid-infrared dual-comb spectroscopy, covering ~300 nm bandwidth around 3.3 μm with 6 GHz spectral resolution and 20 μs temporal resolution. As a demonstration, we study a CH4/He gas mixture in an electric discharge, while the discharge is modulated between dark and glow regimes. We simultaneously monitor the production of C2H6 and the vibrational excitation of CH4 molecules, observing the dynamics of both processes. This approach to broadband, high-resolution, and time-resolved mid-infrared spectroscopy provides a new tool for monitoring the kinetics of fast chemical reactions, with potential applications in various fields such as physical chemistry and plasma/combustion analysis.

Analysis of Gas Turbine Rotating Cavities by an One-Dimensional Model

2009 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Luca Innocenti ◽  
Mirko Micio
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Design Tool ◽  
Operating Conditions ◽  
Outer Flow ◽  
One Dimensional ◽  
Wide Range ◽  
Air System ◽  
Secondary Air ◽  
Radial Outflow

Reliable design of secondary air system is one of the main tasks for the safety, unfailing and performance of gas turbine engines. To meet the increasing demands of gas turbines design, improved tools in prediction of the secondary air system behavior over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore its analysis is not carried out through a complete CFD approach. Usually, that predictions are performed using codes, based on simplified approach which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and few calculation time. Generally the available simplified commercial packages allow to correctly solve only some of the components of a real air system and often the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design-tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for steady one-dimensional axysimmetric flow using experimental correlations both to incorporate flow phenomena caused by multidimensional effects, like heat transfer and flow field losses, and to evaluate the circumferential component of velocity. Although this calculation approach does not enable a correct modeling of the turbulent flow within a wheel space cavity, the authors tried to create an accurate model taking into account the effects of inner and outer flow extraction, rotor and stator drag, leakages, injection momentum and, finally, the shroud/rim seal effects on cavity ingestion. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow both with a Batchelor and/or Stewartson flow structures. A primary 1D-code testing campaign is available in the literature [1]. In the present paper the authors develop, using CFD tools, reliable correlations for both stator and rotor friction coefficients and provide a full 1D-code validation comparing, due to lack of experimental data, the in house design-code predictions with those evaluated by CFD.

scholarly journals Retinal Imaging of Infants on Spectral Domain Optical Coherence Tomography

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Anand Vinekar ◽  
Shwetha Mangalesh ◽  
Chaitra Jayadev ◽  
Ramiro S. Maldonado ◽  
Noel Bauer ◽  
...  
Keyword(s):  
Spectral Domain ◽  
Current Status ◽  
Acquisition Time ◽  
Imaging Device ◽  
Short Acquisition Time ◽  
Visual Potential ◽  
Detailed Assessment ◽  
First Year Of Life ◽  
Sd Oct

Spectral domain coherence tomography (SD OCT) has become an important tool in the management of pediatric retinal diseases. It is a noncontact imaging device that provides detailed assessment of the microanatomy and pathology of the infant retina with a short acquisition time allowing office examination without the requirement of anesthesia. Our understanding of the development and maturation of the infant fovea has been enhanced by SD OCT allowing an in vivo assessment that correlates with histopathology. This has helped us understand the critical correlation of foveal development with visual potential in the first year of life and beyond. In this review, we summarize the recent literature on the clinical applications of SD OCT in studying the pathoanatomy of the infant macula, its ability to detect subclinical features, and its correlation with disease and vision. Retinopathy of prematurity and macular edema have been discussed in detail. The review also summarizes the current status of SD OCT in other infant retinal conditions, imaging the optic nerve, the choroid, and the retinal nerve fibre in infants and children, and suggests future areas of research.

Sign in / Sign up

Export Citation Format

Share Document