New H 2 O weighted sum of gray gases model for natural convection flows within large cavities

Radiation heat transfer plays a significant role in buoyancy driven flows for large scale facilities. In the analysis of nuclear containment safety during severe accidents, it has been found that the thermal radiation particularly affects the temperature distribution and containment pressurization due to the humidity environment. In order to model thermal radiation, one of the main challenges is the description of nongray gas property for the steam-air mixtures. The weighted sum of gray gases model (WSGG) is a reasonable method in engineering applications because of its computational efficiency. There are many WSGG models available for combustion applications, but none of them is dedicated for low temperature applications. Furthermore, most of the existing WSGG models only provide the fixed partial pressure ratios (e.g., p H 2 O = 2p CO 2 for methane). To overcome this limitation, a tailored WSGG model is derived by the Line-by-Line model for a gas mixture composed of arbitrary concentrations of H 2 O. This tailored WSGG model is valid for the pressure path length ranging from 0.0001 to 10 atm · m, and for the temperature from 300 to 1200 K. The WSGG correlations are verified against the Line-by-Line benchmark solutions with isothermal/non-isothermal temperatures and homogeneous/non-homogeneous concentrations. The results demonstrate the ability and efficiency of the new tailored WSGG formulation.

Non-Linear Analysis Of A Nuclear Containment Structure Under High Internal Pressure

The main objective of the current study is to investigate the response of an internally pressurized nuclear power plant containment structure at pressure values higher than design pressure, and is focused on the response of prestressed concrete containment to ultimate global structural failure. The containment structure consists of a prestressed concrete cylindrical perimeter wall, with a prestressed concrete tori-spherical dome, prestressed concrete ring beam, and conventionally reinforced concrete base slab. The finite element program ANSYS is used to predict the non-liner behaviour of the containment structure. Different techniques available in ANSYS program to model steel reinforcements for reinforced concrete and prestressed concrete is estimated to define a more suitable approach to model prestressing system. The approach proposed here is capable of incorporating parameters such as variation in tendon layout and non-uniform prestress losses in comparison to those done by other researchers. It is concluded that the design criteria for the containment structure are fully satisfied. No through crack was observed at design pressure. The first through crack develops in the dome at a pressure of 2.1 times the design pressure. There is no damage to be expected to the reactor systems up to a pressure well above design pressure. It is observed that the containment structure subject of this study meets the design requirement of the current standards and behaves linearly in excess of 1.5 times the design pressure. The response of the internally pressurized containment structure including the major openings is investigated. It is concluded that presence of openings does not have a significant effect on the pressure capacity of the containment structure. The minor differences in the responses are at pressure values beyond the linear limit and are less than 5%. The response when openings are included are very similar to those without openings, except at the immediate neighboring of the equipment airlock opening. It is concluded that to predict the pressure response of containment structure, including the openings can be ignored. In case of need for a more exact response, only the equipment airlock can be included in the model

Non-Linear Analysis Of A Nuclear Containment Structure Under High Internal Pressure

The main objective of the current study is to investigate the response of an internally pressurized nuclear power plant containment structure at pressure values higher than design pressure, and is focused on the response of prestressed concrete containment to ultimate global structural failure. The containment structure consists of a prestressed concrete cylindrical perimeter wall, with a prestressed concrete tori-spherical dome, prestressed concrete ring beam, and conventionally reinforced concrete base slab. The finite element program ANSYS is used to predict the non-liner behaviour of the containment structure. Different techniques available in ANSYS program to model steel reinforcements for reinforced concrete and prestressed concrete is estimated to define a more suitable approach to model prestressing system. The approach proposed here is capable of incorporating parameters such as variation in tendon layout and non-uniform prestress losses in comparison to those done by other researchers. It is concluded that the design criteria for the containment structure are fully satisfied. No through crack was observed at design pressure. The first through crack develops in the dome at a pressure of 2.1 times the design pressure. There is no damage to be expected to the reactor systems up to a pressure well above design pressure. It is observed that the containment structure subject of this study meets the design requirement of the current standards and behaves linearly in excess of 1.5 times the design pressure. The response of the internally pressurized containment structure including the major openings is investigated. It is concluded that presence of openings does not have a significant effect on the pressure capacity of the containment structure. The minor differences in the responses are at pressure values beyond the linear limit and are less than 5%. The response when openings are included are very similar to those without openings, except at the immediate neighboring of the equipment airlock opening. It is concluded that to predict the pressure response of containment structure, including the openings can be ignored. In case of need for a more exact response, only the equipment airlock can be included in the model