KSB (Germany)

Different equations of state (EOS) were applied for describing thermodynamic properties of the system CO2+O2,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {CO}_{2} + \ ext {O}_{2},$$\\end{document} which is important for the Allam cycle: cubic EOS (Soave–Redlich–Kwong, Peng–Robinson), molecular-based EOS (PC-SAFT, PCP-SAFT, SAFT-VR Mie, polar soft-SAFT, BACKONE, sCPA), and multiparameter EOS (GERG-2008, EOS-CG). The pure component models were taken from the literature. The results for the mixture were compared to experimental data from the literature for two cases: (i) the thermodynamic properties of the mixture were modeled using predictive mixing and combination rules; (ii) additional binary interaction parameters were fitted to experimental data for improving the performance. In the predictive mode (i), the best results were obtained with molecular-based EOS. In the adjusted mode (ii) the best results were obtained with the multi-parameter GERG-2008 EOS and EOS-CG.

Abstract. The process-based model 4C (FORESEE) has been developed over the past 20 years to study climate impacts on forests and is now freely available as an open-source tool. The objective of this paper is to provide a comprehensive description of this 4C version (v2.2) for scientific users of the model and to present an evaluation of 4C at four different forest sites across Europe. The evaluation focuses on forest growth as well as carbon (net ecosystem exchange, gross primary production), water (actual evapotranspiration, soil water content), and heat fluxes (soil temperature) using data from the PROFOUND database. We applied different evaluation metrics and compared the daily, monthly, and annual variability of observed and simulated values. The ability to reproduce forest growth (stem diameter and biomass) differs from site to site and is best for a pine stand in Germany (Peitz, model efficiency ME=0.98). 4C is able to reproduce soil temperature at different depths in Sorø and Hyytiälä with good accuracy (for all soil depths ME > 0.8). The dynamics in simulating carbon and water fluxes are well captured on daily and monthly timescales (0.51 < ME < 0.983) but less so on an annual timescale (ME < 0). This model–data mismatch is possibly due to the accumulation of errors because of processes that are missing or represented in a very general way in 4C but not with enough specific detail to cover strong, site-specific dependencies such as ground vegetation growth. These processes need to be further elaborated to improve the projections of climate change on forests. We conclude that, despite shortcomings, 4C is widely applicable, reliable, and therefore ready to be released to the scientific community to use and further develop the model.

Abstract In previous investigations on life with flexible driving were highly stressed components predominantly in hot continuous pressurized part of power plants in the foreground. However cases of damage and subsequent studies on peripheral components such as the boiler circulation system (boiler circulating pump) showed that a potential failure as well as a high hazard potential respectively great consequential damage can occur when such components are operated under different conditions. To avoid damages and losses resulting from damage to peripheral components, these components have to be subjected to further analysis. Here especially the pump housing is in the focus.

The extended loss of AC power (ELAP) event can pose a significant challenge to the integrity of the Reactor Coolant System (RCS) in a Pressurized Water Reactor (PWR). To mitigate the consequences of this event, it is important to maintain adequate coolant inventory and the associated heat removal capability of the RCS. A critical RCS component in maintaining RCS inventory is the Reactor Coolant Pump (RCP) seals. To ensure seal integrity, the RCP seals are either independently cooled by back-up systems or are sufficiently robust to maintain their integrity without cooling until such time when cooling may be restored. A number of new RCP seal designs have been proposed by seal manufacturers to meet this challenge. This paper focuses on one such design, namely, the KSB Station Blackout (SBO) seal package. KSB RCP seals were first introduced in the nuclear industry in the 1970s. The original KSB RCP seals, designated as HDD-254 Type A, consisted of a three stage hydrodynamic design with each stage capable of retaining full RCS pressure. The Type A seals were initially installed in the Combustion Engineering (CE) Palo Verde units and in several reactors in Germany. In the 1980s, these seals were replaced with the Type C seals that incorporated several design improvements. These seals have been successfully installed and operated in over 100 RCPs in Europe, South America, South Korea, and China. These seals continue to demonstrate excellent operating experience with typical replacement interval of 4 to 6 years. Although the reliability of the Type C seals has been excellent based on operating experience, the seal was not specifically designed for coping with an ELAP event that might ensue following an SBO. In order to support the emerging needs of nuclear industry in response to Fukushima, KSB embarked on a seal design improvement program directed towards retaining the high operational reliability of the Type C seal while enhancing the RCP seal package’s high temperature coping capability. This activity resulted in a new seal package design that includes: (1) an advanced high temperature resistant, three stage, Type F seal, (2) a passive thermal check valve (PTCV) intended to passively isolate the RCP controlled bleed-off (CBO) line to maintain RCS inventory, and (3) a back-up fourth stage shaft seal called the “Stand-still” seal. This paper discusses the design and post-accident performance of KSB’s Type F hydrodynamic RCP seal package with emphasis on seal performance capabilities under ELAP conditions. The report concludes that the capability of the primary three stage hydrodynamic seals and the fourth stage “Stand-still” seal to function at high temperatures coupled with the reliable RCP CBO line closure capability and subsequent RCS depressurization ensures that any potential seal leakage would be held to a minimum (less than 2 gpm) for the duration of a 72 hour ELAP scenario. The ELAP coping strategies and their outcomes were validated by a seal test program conducted at KSB’s testing laboratories in Frankenthal, Germany. The results of the tests confirmed that the Type F seals exhibited extremely low leakage rates (∼0.01 gpm) at conditions representative of an ELAP scenario (120 hours up to 300 °C [572 °F] temperature and 160 barg [2320 psig] pressure).

The paper describes an experimental investigation on stall inception phenomena in a single-stage axial-flow pump, utilizing an oil flow technique and two different photo techniques. Moreover, the unsteady casing wall pressure was measured. Representative results are shown and discussed: the pump characteristic for two different NPSH values, selected oil flow pictures of the casing wall and the rotor blades, the wall pressure distribution at design, selected pictures of the cavitating core of the tip clearance vortex at stable and unstable operating conditions and the visualization of a cross-passage vortex as a deep stall phenomenon. These results allow a number of key features of the stall inception process to be identified and to be followed along the unstable part of the pump characteristic.

Pumps take care of the transport of liquids in plants and processes. If they stand still, the result can be loss of production or even failure of entire hydraulic systems. The more expensive a pump is or as more valuable a process is, the more important it is to regularly record and control the condition of the pumps. As pumps also react to changes in a plant, they are also indicators of the conditions prevailing there. In order to achieve real process improvement, it is important to find out the cause of failures and disturbances. With respect to centrifugal pumps, this could be the following: defective mechanical seals point to dry-running or partial-/over-load damaged rolling element bearings are the consequence of gas content of the pumped medium eroded impellers and casings are the result of cavitation.

The paper describes an experimental investigation of the stator hub and blade flow in two different stators of a highly loaded single-stage axial-flow low-speed compressor. The first stator (A) is a conventional design with blades of rectangular planform. The second stator (K) is an unconventional, more advanced design with blades of a special planform, characterized by an aft-swept leading edge with increasing sweep angle towards hub and casing. The experimental results show that stator K exhibits a much better hub performance than stator A, finally leading to a better overall performance of stage K compared to stage A. The better hub performance of stator K is, primarily, the result of a planform effect of the newly introduced blades with an aft-swept leading edge and the aerodynamics of an aft-swept wing.

The paper describes an experimental investigation of the stator hub and blade flow in two different stators of a highly loaded single-stage axial-flow low-speed compressor. The first stator (A) is a conventional design with blades of rectangular planform. The second stator (K) is an unconventional, more advanced design with blades of a special planform, characterized by an aft-swept leading edge with increasing sweep angle toward hub and casing. The experimental results show that stator K exhibits a much better hub performance than stator A, finally leading to a better overall performance of stage K compared to stage A. The better hub performance of stator K is, primarily, the result of a planform effect of the newly introduced blades with an aft-swept leading edge and the aerodynamics of an aft-swept wing.