Dense suspension of solid particles as a new heat transfer fluid for concentrated solar thermal plants: on-sun proof of concept

This paper demonstrates the capacity of dense suspensions of solid particles to transfer concentrated solar power from a tubular receiver to an energy conversion process by acting as a heat transfer fluid. Contrary to a circulating fluidized bed, the dense suspension of particles’ flows operates at low gas velocity and large solid fraction. A single-tube solar receiver was tested with 64 µm mean diameter silicon carbide particles for solar flux densities in the range 200–250 kW/m2, resulting in a solid particle temperature increase ranging between 50 °C and 150 °C. The mean wall-to-suspension heat transfer coefficient was calculated from experimental data. It is very sensitive to the particle volume fraction of the suspension, which was varied from 26 to 35%, and to the mean particle velocity. Heat transfer coefficients ranging from 140 W/m2 K to 500 W/m2 K have been obtained, thus corresponding to a 400 W/m2 K mean value for standard operating conditions (high solid fraction) at low temperature. A higher heat transfer coefficient may be expected at high temperatures because the wall-to-suspension heat transfer coefficient increases drastically with temperature. The suspension has a heat capacity similar to a liquid heat transfer fluid, with no temperature limitation but the working temperature limit of the receiver tube. Suspension temperatures of up to 750 °C are expected for metallic tubes, thus opening new opportunities for high efficiency thermodynamic cycles such as supercritical steam and supercritical carbon dioxide

A new heat transfer fluid for concentrating solar systems: Particle flow in tubes

This paper demonstrates a new concept of heat transfer fluid (HTF) for CSP applications, developed in the frame of both a National and a European project (CSP2 FP7 project). It involves a dense suspension of small solid particles. This innovation is currently. The dense suspension of particles receiver (DSPR) consists in creating the upward circulation of a dense suspension of particles (solid fraction in the range 30%-40%) in vertical absorbing tubes submitted to concentrated solar energy. So the suspension acts as a heat transfer fluid with a heat capacity similar to a liquid HTF but only limited in temperature by the working temperature limit of the receiver tubes. Suspension temperatures up to 750°C are expected for metallic tubes, thus opening new opportunities for high efficiency thermodynamic cycles such as supercritical steam and carbon dioxide. First experimental results were obtained during on-sun testing with CNRS solar facility of a single tube DSPR for an outlet temperature lower than 300°C. In this lab-scale experimental setup, the solar absorber is a single opaque metallic tube, containing upward solid circulation, located inside a cylindrical cavity dug in a receiver made of refractory, and submitted to the concentrated solar radiation through a 0.10m x 0.50m slot. The absorber is a 42.4 mm o.d. stainless steel tube. SiC was used because of its thermal properties, availability and rather low cost. The 63.9 μm particle mean diameter permits a good fluidization with almost no bubbles, for very low air velocities. Solar flux densities in the range 200-250 kW/m2 were tested resulting in solid temperature increase ranging between 50 and 150°C. The mean wall-to-suspension heat transfer coefficient (h) was calculated from experimental data. It is very sensitive to the solid fraction of the solid suspension, which was varied from 27% to 36%. These latter values are one order of magnitude larger than the solid fraction in circulating fluidized beds operating at much higher air velocity. Heat transfer coefficients ranging from 140 to 500 W/m2.K have been obtained; i.e. 400 W/m2.K mean value for standard operating conditions at low temperature

Post-trauma scoliosis after conservative treatment of thoracolumbar spinal fracture in children and adolescents: results in 48 patients.

PURPOSE: Authors examined a case series of patients younger than 18 years old who had sustained a traumatic thoracolumbar spine fracture to evaluate radiological and clinical findings of coronal spinal balance, after conservative treatment. METHODS: From 1996 to 2014, a tricentric cohort of 48 patients with an average age of 12 years was radiographically reviewed at 50 months. Cobb angle of fractured vertebra and regional Cobb angle were measured both at baseline and follow-up. Analyses were done according to initial Risser grade, number of fractures and level of injury. RESULTS: There was a total of 11 scoliosis. In group with Risser grade 3 or above, with a single vertebral fracture and lumbar fracture, final regional Cobb angle was statistically higher than initial regional Cobb angle. CONCLUSIONS: The prevalence of scoliosis in our population is higher than those of idiopathic scoliosis; Risser grade 3 or above, lumbar fracture and a single fracture seem to account for more severe coronal deformatio

Conservative treatment of pediatric thoracic and lumbar spinal fractures

To assess sagittal plane spinopelvic balance and functional outcomes in a pediatric cohort of patients with a thoracic and/or a lumbar fracture treated conservatively. A multicentric study retrospectively reviewed radiological and functional outcomes (mean follow-up 49 months) of 48 patients (mean age 12 years) with thoracic and/or lumbar spinal fractures that occurred between 1996 and 2014. Demographic data and radiological spinopelvic parameters were analyzed. Functional outcome was evaluated by a telephone interview. First, a comparison between the initial and the last follow-up full-spine radiographs was performed for the assessment of bone remodeling and sagittal plane balance. Then, patients were classified into two groups (group 1: Risser≤2 and group 2, Risser>2) to assess the influence of skeletal maturity on the restoration of a correct sagittal balance. A total of 62% of the patients were at skeletal maturity at the final follow-up (Risser 4 and 5). Patients with a Risser grade of 2 or less had a higher remodeling potential. The mean residual local kyphosis in thoracic and lumbar fractures was, respectively, 8.2° and 8.7°. The mean thoracic global kyphosis remains stable at the last follow-up, in contrast to lumbar lordosis, which increased significantly. Sagittal plane global measurements on the basis of the C7-plumbline remained unchanged at the last follow-up. There was no change in the pelvic parameters, except for the sacral slope in the group 1 for patients with a lumbar fracture. The current study confirms a greater correction in younger patients (Risser≤2) in spinal fractures and reported that thoracic fractures have a higher remodeling potential than lumbar fracture. A local kyphosis of almost 10° remained at the last follow-up. However, no deterioration in the sagittal plane balance was found. This suggests compensatory mechanisms in adjacent structures for children and adolescents and excludes the only hypothesis of bone remodeling

La Napoléonienne / par L.-C. Boissière

Avec mode text

A Latour-d'Auvergne, à l'occasion d'un monument élevé à sa mémoire (par L.-C. Boissière)

Avec mode text

The lumbar lordosis index: a new ratio to detect spinal malalignment with a therapeutic impact for sagittal balance correction decisions in adult scoliosis surgery

Abstract Purpose Sagittal malalignment is frequently observed in adult scoliosis. C7 plumb line, lumbar lordosis and pelvic tilt are the main factors to evaluate sagittal balance and the need of a vertebral osteotomy to correct it. We described a ratio: the lumbar lordosis index (ratio lumbar lordosis/ pelvic incidence) (LLI) and analyzed its relationships with spinal malalignment and vertebral osteotomies. Methods 53 consecutive patients with a surgical adult scoliosis had preoperative and postoperative full spine EOS radiographies to measure spino-pelvic parameters and LLI. The lack of lordosis was calculated after prediction of theoretical lumbar lordosis. Correlation analysis between the different parameters was performed. Results All parameters were correlated with spinal malalignment but LLI is the most correlated parameter (r = -0.978). It is also the best parameter in this study to predict the need of a spinal osteotomy (r = 1 if LLI \0.5). Conclusion LLI is a statistically validated parameter for sagittal malalignment analysis. It can be used as a mathematical tool to detect spinal malalignment in adult scoliosis and guides the surgeon decision of realizing a vertebral osteotomy for adult scoliosis sagittal correction. It can be used as well for the interpretation of clinical series in adult scoliosis

Lettre de Louis Phélypeaux de Pontchartrain (chancelier de France) à Jean-Charles de La Fontaine, seigneur de La Boissière (lieutenant de roi à Dieppe) datée du 06 septembre 1713

Lettre de Louis Phélypeaux de Pontchartrain (chancelier de France) à Jean-Charles de La Fontaine, seigneur de La Boissière (lieutenant de roi à Dieppe) datée du 06 septembre 1713. In: Correspondance administrative sous le règne de Louis XIV, recueillie et mise en ordre par G. B. Depping. Tome II. Administration de la justice – Police – Galères. Paris : Imprimerie nationale, 1851. pp. 535-536