39 research outputs found
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