Author: Jason R. Casey
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 122
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Book Description
At Oregon State University the Multi-Application Small Light Water Reactor (MASLWR) integral effects testing facility is being prepared for safety analysis matrix testing in support of the NuScale Power Inc. (NSP) design certification progress. The facility will be used to simulate design basis accident performance of the reactor's safety systems. The design includes an initially evacuated, high pressure capable containment system simulated by a 5 meter tall pressure vessel. The convection-condensation process that occurs during use of the Emergency Core Cooling System has been characterized during two experimental continuous blowdown events. Experimental data has been used to calculate an average heat transfer coefficient for the containment system. The capability of the containment system has been analytically proven to be a conservative estimate of the full scale reactor system.
Author: Etienne M. Mullin
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 88
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Book Description
The Oregon State University Multi-Application Small Light Water Reactor test facility is employed in a series tests to evaluate condensation heat transfer in small, high pressure containment vessels characteristic of small modular reactor designs under development. This integral system test facility was constructed to demonstrate the feasibility of a pioneering SMR design and features a scaled containment vessel and cooling pool heat sink. The tests performed involve supplying steam into the containment and observing the condensation rates occurring on the heat transfer surface. The test data is reduced to quantify condensation heat transfer rates and heat transfer coefficients. Particular attention is paid to the influence of system pressure and noncondensable gas inventory.
Author: Palash Kumar Bhowmik
Publisher:
ISBN:
Category :
Languages : en
Pages : 199
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Book Description
"The purpose of this research was to perform scaled experiments and simulations to validate computational fluid dynamics (CFD) and empirical models of condensation heat transfer (CHT) for the passive containment cooling system (PCCS) of Small Modular Reactors (SMRs). SMRs are the futuristic candidates for clean, economic, and safe energy generation; however, reactor licensing requires safety system evaluations, such as PCCS. The knowledge in the reviewed relevant literature showed a gap in experimental data for scaling SMR's safety systems and validating computational models. The previously available test data were inconsistent due to unscaled geometric and varying physics conditions. These inconsistencies lead to inadequate test data benchmarking. This study developed three scaled (different diameters) test sections with annular cooling for scale testing and analysis to fill this research gap. First, tests were performed for pure steam and steam with non-condensable gases (NCGs), like nitrogen and helium, at different mass fractions, inlet mass flow rates, and pressure ranges. Second, detailed CFD simulations and validations were performed using STAR-CCM+ software with scaled geometries and experimental parameters (e.g., flow rate, pressure, and steam-NCG mixtures), thus mimicking reactor accident cases. The multi-component gases, multiphase mixtures, and fluid film condensation models were applied, verified, and optimized in the CFD simulations with associated turbulence models. Third, the physics-based and data-driven condensation models and empirical correlations were assessed to quantify the scaling distortions. Finally, the experiments, simulations, and modeling results were evaluated for critical insights into the physics conditions, scaling effects, and multi-component gas mixture parameters. This study supported improvements to nuclear reactor safety systems' modeling capabilities irrespective of size (small or big), and findings were equally applicable to other non-nuclear energy applications"--Abstract, page iii.
Author: Dongyoung Lee
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 132
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Book Description
There is renewed interest in the reliability and safety of nuclear power plants following the Fukushima Daiichi nuclear accident followed by 8.9 magnitude earthquake and Tsunami with the height of 15 m on March 11, 2011. Small Modular Reactors (SMRs) have been developed to improve safety systems by utilizing passive and natural circulation forces under normal operations and accident conditions. One key feature of the safety systems in SMRs is the use of containment condensation to prevent core melt down. For further development of the SMR for design certifications, the condensation model at relatively high pressures compared with current operating power plants should be verified and validated. For this process, at Oregon State University, the MASLWR (Multi Application Small Light Water Reactor) test facility, which has 1:3 length scale, can perform integrated tests on containment condensation of SMRs. Using the MASLWR test facility experimental data, this study investigated three major subjects: heat flux estimation on the containment wall, flow transition of condensation film flow dynamics and assessing the scaling effects of the MASLWR test facility. An inverse heat conduction algorithm was developed to estimate the heat fluxes of film condensation at the containment wall in the MASLWR test facility during transients. Through a fundamental one-dimensional approach for condensation film flow, the governing equations were derived and numerically solved. A linear perturbation stability analysis using steady-state results of condensation film flow at the containment wall found that Re ~1600 is the transition point between laminar and turbulent film flow regimes. This finding agreed with the experimental results of Ishigai et al. (1974) and Morioka et al. (1993). Based on scaling analysis using the diffusion layer model and experimental correlations, the length distortion factor was examined. In this study, it was found that the 1:3 length scale test facility underestimated the heat transfer rate more than the prototype. The results presented in this dissertation cover the film flow dynamics of condensation film flows as well as an inverse heat transfer calculation to advance the knowledge of containment condensation in SMRs.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 225
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Book Description
This NEUP funded project, NEUP 12-3630, is for experimental, numerical and analytical studies on high-pressure steam condensation phenomena in a steel containment vessel connected to a water cooling tank, carried out at Oregon State University (OrSU) and the University of Wisconsin at Madison (UW-Madison). In the three years of investigation duration, following the original proposal, the planned tasks have been completed: (1) Performed a scaling study for the full pressure test facility applicable to the reference design for the condensation heat transfer process during design basis accidents (DBAs), modified the existing test facility to route the steady-state secondary steam flow into the high pressure containment for controllable condensation tests, and extended the operations at negative gage pressure conditions (OrSU). (2) Conducted a series of DBA and quasi-steady experiments using the full pressure test facility to provide a reliable high pressure condensation database (OrSU). (3) Analyzed experimental data and evaluated condensation model for the experimental conditions, and predicted the prototypic containment performance under accidental conditions (UW-Madison). A film flow model was developed for the scaling analysis, and the results suggest that the 1/3 scaled test facility covers large portion of laminar film flow, leading to a lower average heat transfer coefficient comparing to the prototypic value. Although it is conservative in reactor safety analysis, the significant reduction of heat transfer coefficient (50%) could under estimate the prototypic condensation heat transfer rate, resulting in inaccurate prediction of the decay heat removal capability. Further investigation is thus needed to quantify the scaling distortion for safety analysis code validation. Experimental investigations were performed in the existing MASLWR test facility at OrST with minor modifications. A total of 13 containment condensation tests were conducted for pressure ranging from 4 to 21 bar with three different static inventories of non-condensable gas. Condensation and heat transfer rates were evaluated employing several methods, notably from measured temperature gradients in the HTP as well as measured condensate formation rates. A detailed mass and energy accounting was used to assess the various measurement methods and to support simplifying assumptions required for the analysis. Condensation heat fluxes and heat transfer coefficients are calculated and presented as a function of pressure to satisfy the objectives of this investigation. The major conclusions for those tests are summarized below: (1) In the steam blow-down tests, the initial condensation heat transfer process involves the heating-up of the containment heat transfer plate. An inverse heat conduction model was developed to capture the rapid transient transfer characteristics, and the analysis method is applicable to SMR safety analysis. (2) The average condensation heat transfer coefficients for different pressure conditions and non-condensable gas mass fractions were obtained from the integral test facility, through the measurements of the heat conduction rate across the containment heat transfer plate, and from the water condensation rates measurement based on the total energy balance equation. 15 (3) The test results using the measured HTP wall temperatures are considerably lower than popular condensation models would predict mainly due to the side wall conduction effects in the existing MASLWR integral test facility. The data revealed the detailed heat transfer characteristics of the model containment, important to the SMR safety analysis and the validation of associated evaluation model. However this approach, unlike separate effect tests, cannot isolate the condensation heat transfer coefficient over the containment wall, and therefore is not suitable for the assessment of the condensation heat transfer coefficient against system pressure and noncondensable ...
Author: Moo Hwan Kim
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 552
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Book Description
Author: Battelle-Institut
Publisher:
ISBN:
Category : Nuclear reactors
Languages : en
Pages : 120
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Book Description
Author: Robert Hoyt Whitley
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 246
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Book Description
Author: Dhongik Samuel Yoon
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Condensation of steam vapor is an important mode of energy removal from the reactor containment in postulated design basis accidents where high-energy steam escapes into the reactor containment. Due to its passive nature and magnitude of heat transfer associated with phase change, condensation can be used as an effective energy removal mechanism, especially for reactors with a passive containment cooling system. Therefore, there has been a great interest in modeling condensation phenomena in the reactor containment for the purpose of accident analysis. Until recently, the focus has been the presence of noncondensable gas since traditional reactor designs operate at near atmospheric pressure with substantial amount of noncondensable gas in the containment, which hinders the process of condensation heat transfer. In this case, the phase change is dominated by diffusion resistance in the gas mixture phase and the thermal resistance of condensate film layer can be neglected. Recent advanced reactor designs, on the other hand, are designed to allow very low air pressure in the containment. In this case, the heat transfer resistance due to the presence of noncondensable gas is reduced significantly and the thermal resistance of condensate film layer can no longer be neglected. Moreover, it has been reported that condensation on the micro or nano-engineered surfaces shows substantially different behavior compared to traditional untreated surfaces. Those engineered surfaces with modified wetting characteristics can affect the condensation rates by affecting the condensate film behavior on such surfaces, proposing a potential way of affecting the heat removal from reactor containment by wall surface modification. Consequently, it has become relevant and necessary to study and characterize the effect of thermal resistance and kinetic conditions of the condensate film layer on the overall condensation heat transfer in the reactor containment regarding conditions with very low noncondensable gas concentration where the presence of condensate film layer can no longer be neglected. The current condensation model in MELCOR was evaluated in order to assess its capability to predict condensation heat transfer for traditional containment conditions. By modeling sets of containment condensation experiments, satisfactory performance of MELCOR in predicting condensation phenomena was confirmed for conditions with significant noncondensable gas concentration. It has to be noted that, as a result of this assessment, few adjustments has been implemented to guarantee more accurate predictions of MELCOR in specific conditions addressed in those experiments. However, it is observed that MELCOR may be inaccurate in predicting condensation for conditions with very low noncondensable gas concentrations where the effects of condensate film layer is more prominent. However, MELCOR's correlation-based models prevent further investigations on the parameters that have not been already implemented. In an effort to better understand the effect of thermal resistance and kinetic conditions of the condensate film layer for conditions with very low noncondensable gas concentrations, a condensation model was developed in the framework of a Computation Fluid Dynamics (CFD) to include thermal and kinetic conditions of the condensate film layer. The developed condensation model includes heat transfer resistances in both phases without directly simulating the two-fluid problem and proposes that the liquid-gas interface can be represented as a free surface. Case studies were conducted to show its theoretical validity. The developed condensation model including the thermal resistance of the condensate film layer and the free surface assumption was validated against two sets of separate effects experiments, one in traditional reactor containment conditions and the other in a pure steam condition. The results indicate that a free surface assumption can greatly improve the prediction of condensation heat transfer, even for traditional reactor containment conditions where the concentration of noncondensable gas is significant. Including the thermal resistance of the condensate film layer does not provide a significant change in the results for high noncondensable gas concentration cases, as expected. For near-pure steam conditions, however, the effect of the condensate film is not only significant but also increases with decreasing noncondensable gas concentration as expected. The proposed modeling approach is also able to account for this effect.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
An alternative model for calculating condensation heat transfer following a main stream line break (MSLB) accident is proposed. The proposed model predictions and the current regulatory model predictions are compared to the results of the Carolinas Virginia Tube Reactor (CVTR) test. The very conservative results predicted by the current regulatory model result from: (1) low estimate of the condensation heat transfer coefficient by the Uchida correlation and (2) neglecting the convective contribution to the overall heat transfer. Neglecting the convection overestimates the mass of steam being condensed and does not permit the calculation of additional convective heat transfer resulting from superheated conditions. In this study, the Uchida correlation is used, but correction factors for the effects of convection an superheat are derived. The proposed model uses heat and mass transfer analogy methods to estimate to convective fraction of the total heat transfer and bases the steam removal rate on the condensation heat transfer portion only. The results predicted by the proposed model are shown to be conservative and more accurate than those predicted by the current regulatory model when compared with the results of the CVTR test. Results for typical pressurized water reactors indicate that the proposed model provides a basis for lowering the equipment qualification temperature envelope, particularly at later times following the accident.
