Low grade waste heat recovery in an intercooled recuperated closed cycle gas turbine

The context of the work is the study of a 180 bar nitrogen recuperated and intercooled turbo-compressor of 300 MWe. The net efficiency of this closed cycle gas turbine is assessed between 37 and 37.5%, but which could be increased by considering waste heat recovery techniques. Among waste heat recovery technologies which are currently used in conventional gas turbines we find organic Rankine cycles (ORC). This kind of machine is similar to a conventional steam cycle energy conversion system, but uses an organic fluid instead of water. A main challenge is the low level of temperature of waste (90°C). Preliminary studies are carried out on the design of ORC using three different fluids: traditional and mature R245fa technology, innovative R125 cycle and high pressure low temperature transcritical CO2 machine. Different architectures are compared and advantages of using transcritical cycles have been underlined. From a thermodynamic point of view the best solution would be to use R125 cycle at a supercritical pressure at precooler secondary side and at a subcritical pressure at intercooler secondary side. A supplementary power of more than 15 MWe could be achieved. The resulting combined cycle could reach a net efficiency of 39%.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

River routing at the continental scale: use of globally-available data and an a priori method of parameter estimation

International audienceTwo applications of a river routing model based on the observed river network and a linearised solution to the convective-diffusion equation are presented. One is an off-line application to part of the Amazon basin (catchment area 2.15 M km2) using river network data from the Digital Chart of the World and GCM-generated runoff at a grid resolution of 2.5 degrees latitude and 3.75 degrees longitude. The other application is to the Arkansas (409,000 km2) and Red River (125,500 km2) basins as an integrated component of a macro-scale hydrological model, driven by observed meteorology and operating on a 17 km grid. This second application makes use of the US EPA reach data to construct the river network. In both cases, a method of computing parameter values a priori has been applied and shows some success, although some interpretation is required to derive `correct' parameter values and further work is needed to develop guidelines for use of the method. The applications, however, do demonstrate the possibilities for applying the routing model at the continental scale, with globally-available data and a priori parameter estimation, and its value for validating GCM output against observed flows

Thermo-electric energy storage using co2 transcritical cycles and ground heat storage

Multi-megawatt thermo-electric energy storage based on thermodynamic cycles is a promising alternative to PSH (Pumped-Storage Hydroelectricity) and CAES (Compressed Air Energy Storage) systems. The size and cost of the heat storage are the main drawbacks of this technology but using the ground as a heat reservoir could be an interesting and cheap solution. In that context, the aim of this work is i) to assess the performance of a massive electricity storage concept based on CO2 transcritical cycles and ground heat exchangers, and ii) to carry out the preliminary design of the whole system. This later includes a heat pump transcritical cycle as the charging process and a transcritical Rankine cycle of 1 – 10 MWe as the discharging process. A steady-state thermodynamic model is realized and several options, including regenerative or multi-stage cycles, are investigated. In addition, a one-dimensional design model of the geothermal heat exchanger network is used to optimize the number of wells for the ground heat storage. The results show the strong dependency between the charging and discharging cycles, and how the use of regenerative heat exchangers and a two-phase expander (in the charging cycle) could increase the system efficiency and lower the investment cost.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Sterilization of hydrogen peroxide resistant bacterial spores with stabilized chlorine dioxide

Bacillus pumilus SAFR-032 spores isolated from a clean room environment are known to exhibit enhanced resistance to peroxide, desiccation, UV radiation and chemical disinfection than other spore-forming bacteria. The survival of B. pumilus SAFR-032 spores to standard clean room sterilization practices requires development of more stringent disinfection agents. Here, we report the effects of a stabilized chlorine dioxide-based biocidal agent against spores of B. pumilus SAFR-032 and Bacillus subtilis ATCC 6051. Viability was determined via CFU measurement after exposure. Chlorine dioxide demonstrated efficacy towards sterilization of spores of B. pumilus SAFR-032 equivalent or better than exposure to hydrogen peroxide. These results indicate efficacy of chlorine dioxide delivered through a stabilized chlorine dioxide product as a means of sterilization of peroxide- and UV-resistant spores.This work is supported by the National Institutes of Health (1R01GM090064-01), a NASA EPSCoR Research Infrastructure Development (RID) grant NN07AL49A, and the University of Oklahoma.Ye

Thermal fluctuations in the lower plenum of an high temperature reactor

International audienc

A comparison between two ways of blocked pump losses prediction correlations and one dimensional CATHARE pump model.

International audienceComparaison des resultats de prediction de perte de charge a l'arret de pompes rotodyamiques, d'une part par une methode correlative et d'autre part par l'utilisation d'un modele unidimensionnel de pompe actuellement en developpement dans CATHARE 3

A rotodynamic pump seizure transient simulated using the CATHARE-3 one-dimensional pump model.

Presentation Version 2In the core of a nuclear reactor, irradiation defects created by the fast neutron flux can have a detrimental effect on the corrosion of aluminium alloys. In order to better understand the effect of irradiation on aluminium corrosion, a hydroxide obtained by corrosion of an Al-Mg-Si alloy is irradiated with Al ions. The damage created is 2.5 dpa (displacement per atom) on average in the aluminium hydroxide (Stopping and Range of Ions in Matter (SRIM) calculation). The ion irradiation seems to cause an amorphization of the hydroxide. Voids and nano-crystallites can also be observed.After re-corrosion of the irradiated hydroxide, an increase of the thickness of the oxide layer can be observed compared to the non-irradiated oxide

Description of an improved turbomachinery model to be developed in the cathare3 code for ASTRID power conversion system application

International audienceASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) is the 1500 MWthFrench sodium-cooled fast reactor (SFR) developed by the CEA and its partners. It is designed todemonstrate the workability at an industrial scale of this Generation IV reactor type. For safety reasons, agas power conversion system (PCS) based on a nitrogen Brayton cycle is envisaged for the tertiarycircuit. The safety demonstration for this innovative option will require the calculation of a wide range ofaccidental situations. The thermo-hydraulic transient calculations will be performed using the CATHARE3 code, that will have to accurately represent the primary (sodium), the secondary (sodium) and thetertiary (nitrogen) circuits

Modelling of a radial pump fast startup with the CATHARE-3 Code and analyse of the loop response

International audienceThe french alternative energies and atomic energy commission (CEA) is currently doingresearch in the pump modelling field. A predictive transient, two-phase flow rotodynamicpump model has been developed in the CATHARE-3 code. Flow inside parts of the pump(suction, impeller, diffuser, volute) is computed according to a one-dimensional discretization.A mean flow path has to be defined for such a modelling. Validation has startedduring years 2017-18 at the component scale by comparison to an existing experimentaldatabase. The ability of the model to predict head and torque as a function of time duringa 1-second pump fast start-up has been proved when imposing rotational speed and flowrate evolutions. The present study aims at extending the validation at the system scale awhole loop is modelled