The effects of activated cooler power on the transient pressure decay and helium mixing in the PANDA facility

R. Kapulla,S. Paranjape,M. Fehlmann,S. Suter,U. Doll,D. Paladino 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6

The main outcomes of the experiments H2P6 performed in the thermal-hydraulics large-scale PANDAfacility at PSI in the frame of the OECD/NEA HYMERES-2 project are presented in this article. The experiments of the H2P6 series consists of two PANDA tests characterized by the activation ofthree (H2P6_1) or one (H2P6_2) cooler(s) in an initially stratified and pressurized containment atmosphere. The initial stratification is defined by a helium-rich region located in the upper part of the vesseland a steam/air atmosphere in the lower part. The activation of the cooler(s) results i) in the condensation of the steam in the vicinity of the cooler(s), ii) the corresponding activation of large scale naturalcirculation currents in the vessel atmosphere, with the result of iii) the re-distribution and mixing of theHelium stratification initially located in the upper half of the vessel and iv) the continuous pressuredecay. The initial helium layer represents hydrogen generated in a postulated severe accident. The main question to be answered by the experiments is whether or not the interaction of thedifferent, localized cooler units would be important for the application of numerical methods. The paper describes the initial and boundary conditions and the experimental results of the H2P6series with the suggestion of simple scaling laws for both experiments in terms of i) the temperaturedifference(s) across the cooler(s), ii) the transient steam and helium content and iii) the pressure decay inthe vessel. The outcomes of this scaling indicate that the interaction between separate, closely localizedunits does not play a prominent role for the present experiments. It is therefore reasonable to modelseveral units as one large component with equivalent heat transfer area and total water flow rate

Experimental assessment of thermal radiation effects on containment atmospheres with varying steam content

Kapulla R.,Paranjape S.,Doll U.,Kirkby E.,Paladino D. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11

The thermal-hydraulics phenomena in a containment during an accident will necessarily include radiative heat transfer (i) within the gas mixture due to the high radiative absorption and emission of steam and (ii) between the gas mixture and the surrounding structures. The analysis of some previous PANDA experiments (PSI, Switzerland) demonstrated the importance of the proper modelling of radiation for the benefit of numerical simulations. These results together with dedicated scoping calculations conducted for the present experiments indicated that the radiative heat transfer is considerable, even for a very low amount of steam (z2%). The H2P2 series conducted in the large-scale PANDA facility at the Paul-Scherrer-Institut (PSI) in the framework of the OECD/NEA HYMERES-2 project is intended to enhance the understanding of thermal radiation phenomena and to provide a benchmark for corresponding numerical simulations. Thus, the test matrix was tailored around the two opposite extremes: either gas compositions with small steam content such that radiative heat transfer phenomena can be neglected. Or gas mixtures containing larger amounts of steam, so that radiative heat transfer is expected to play a dominant role. The H2P2 series consists of 5 experiments designed to isolate the radiation phenomena from convective and diffusive effects as much as possible. One vessel with a diameter of 4 m and a height of 8 m was preconditioned with different mixtures of air / steam at room and elevated temperatures. This was followed by the build-up of a stable helium stratification at constant pressure in the upper part of the vessel. After that, helium was injected from the top into the vessel which leads to an increase of the vessel pressure and a corresponding elevation-dependent and transient rise of the gas temperature. It is shown that even the addition of small amounts of steam in the initial gas atmosphere considerably impacts the radiative heat transport throughout all phases of the experiments and markedly influences i) the monitored gas peak temperature, ii) the temperature history during the compression and iii) the following relaxation phase after the compression was stopped. These PANDA experiments are the first of its kind conducted in a large scale thermal-hydraulic facility.

Optimization of the Spanwise Twist of a Flapping Wing for Bird-sized Aircraft using a Quasi-Steady Aerodynamic Model

Diganta Bhattacharjee,Aditya A. Paranjape,Rajkumar S. Pant 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.3

This paper analyzes the effect of spanwise distribution of twist angle on the forces generated by flapping wings as well as the power requirements. We consider four sample profiles of the twist angle as a function of spanwise location, and compute the forces and power requirements under non-accelerating level flight conditions. We investigate three different wing geometries, with varying wingspan and aspect ratios. It has been found that for planforms with moderate to high wingspans, a quadratic profile performs better than the constant and linear ones; whereas for planforms with smaller wingspans, a linear profile performs better than the rest. The analysis presented in this paper can be used to identify the most suitable wing twist profile as a function of the flight parameters and can be used as the basis for wing morphing.

Tunneling decay of self-gravitating vortices

Dupuis, É,ric,Gobeil, Yan,Lee, Bum-Hoon,Lee, Wonwoo,MacKenzie, Richard,Paranjape, Manu B.,Yajnik, Urjit A.,Yeom, Dong-han,Gwak, B.,Kang, G.,Kim, C.,Kim, H.-C.,Lee, C.-H.,Lee, J.,Lee, S.,Lee, W. EDP Sciences 2018 The European Physical Journal Conferences Vol.168 No.-

<P>We investigate tunneling decay of false vortices in the presence of gravity, in which vortices are trapped in the false vacuum of a theory of scalar electrodynamics in three dimensions. The core of the vortex contains magnetic flux in the true vacuum, while outside the vortex is the appropriate topologically nontrivial false vacuum. We numerically obtain vortex solutions which are classically stable; however, they could decay via tunneling. To show this phenomenon, we construct the proper junction conditions in curved spacetime. We find that the tunneling exponent for the vortices is half that for Coleman-de Luccia bubbles and discuss possible future applications.</P>

Silk Gland Fibroin from Indian Muga Silkworm Antheraea assama as Potential Biomaterial

Subrata Kar,Sarmistha Talukdar,Shilpa Pal,Sunita Nayak,Pallavi Paranjape,S.C. Kundu 한국조직공학과 재생의학회 2013 조직공학과 재생의학 Vol.10 No.4

There is an increasing demand for new versatile biomaterials. Silk is reported by many researchers as an ideal biomaterial for different biomedical applications. Most of the studies are carried out on mulberry silk Bombyx mori, however silk from Indian non-mulberry silkworms are relatively unexplored. In this report we fabricate 2D matrices from the regenerated aqueous silk fibroin protein of the glands of non-mulberry Indian muga silkworm Antheraea assama (assamensis). Its biochemical, biophysical characteristics and its cytocompatibility for biomedical uses are evaluated. The properties of this muga gland fibroin are compared with silk gland fibroin from non-mulberry Indian tropical tasar silkworm Antheraea mylitta and with the fibroin from the cocoon of mulberry silkworm Bombyx mori. The gland fibroin of Antheraea assama is observed to consist of two polypeptides of approximately 250kDa each linked by disulfide bond. Fourier transformed infrared spectroscopy and X-ray diffraction studies indicate random coil structure of dissolved fibroin solution. The alpha-helical structure in 2D films changed to beta-sheets upon ethanol treatment, imparting crystallinity and insolubility. The fibroin film is found to be the least hydrophilic, followed by B. mori and A. mylitta silk. Biocompatibility of the films from all three species is investigated through the cell attachment and spreading study of MG-63 human osteoblast-like cells. The cytocompatibility of non-mulberry fibroin matrices are comparable with that of standard tissue culture plates. The results indicate that the non-mulberry Indian muga silk gland fibroin is also suitable matrix as a natural biomaterial for tissue engineering applications.