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- Efstathiadis, T., et al.
(författare)
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Geometry Optimization of Power Production Turbine For A Low Enthalpy (<= 100 degrees C) ORC System
- 2015
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 75, s. 1624-1630
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Tidskriftsartikel (refereegranskat)abstract
- The present paper is examining the geometry optimization of a power production turbine, in the range of 100kW(el), for a low enthalpy Organic Rankine cycle system (<= 100 degrees C). In the last years, accelerated consumption of fossil fuels has caused many serious environmental problems such as global warming, ozone layer destruction and atmospheric pollution. It is this reason that a growing trend towards exploiting low-enthalpy content energy sources has commenced and led to a renewed interest in small-scale turbines for Organic Rankine Cycle applications. The design concept for such turbines can be quite different from either standard gas or steam turbine designs. The limited enthalpic content of many energy sources imposes the use of organic working media, with unusual properties for the turbine. A versatile cycle design and optimization requires the parameterization of the main turbine design. There are many potential applications of this power-generating turbine, including geothermal and concentrate solar thermal fields or waste heat of steam turbine exhausts. An integrated model of equations has been developed, thus creating a model to assess the performance of an organic cycle for various working fluids such as R134a and isobutane-isopentane mixture. The most appropriate working fluid has been chosen, taking its influence on both cycle efficiency and the specific volume ratio into consideration. This choice is of particular importance at turbine extreme operating conditions, which are strongly related to the turbine size. In order to assess the influence of various design parameters, a turbine design tool has been developed and applied to define the geometry of blades in a preliminary stage. Finally, as far as the working fluid is concerned, the mixture of 85% isopentane-15% isobutane has been chosen as the most suitable fluid for the low enthalpy ORC system, since its output net power is 10% higher compared to the output net power of R134a.
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| 2. |
- Grane, P, et al.
(författare)
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Septic and aseptic post-operative discitis in the lumbar spine--evaluation by MR imaging
- 1998
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Ingår i: Acta radiologica (Stockholm, Sweden : 1987). - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 39:2, s. 108-115
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: the aim of this study was to determine whether it was possible to differentiate septic from aseptic post-operative discitis in the lumbar spine by means of MR imaging Material and Methods: the study was a retrospective evaluation of 12 patients with prior lumbar discectomy and suspected post-operative discitis displaying low-back pain and typical MR findings. Six patients had elevated serum C-reactive protein (CRP) (septic) and 6 had normal CRP (aseptic). We used MR imaging to assess the distribution and degree of changes in the disc, in adjacent bone marrow, and in surrounding soft tissue Results: of the 6 patients with increased CRP levels, 3 had extensive MR changes typical of septic post-operative discitis: 1 found soon after surgery; 2 found later. the other 3 patients with septic discitis, who were examined in the early post-operative period, showed MR changes similar to those in the 6 patients with aseptic discitis Conclusion: Suspicion of septic post-operative discitis should be confirmed by MR imaging, serum CRP, and disc puncture. MR imaging is not reliable as the sole method for distinguishing septic from aseptic discitis in the early post-operative stage
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