Theoretical investigation of plasma dynamical behavior and halo current analysis

Khan²,

et al. 2020

Int J Energy Res

For the fast uptake into industrial applications, the further development of robust methods of nanomaterials, which are inexpensive and simultaneously technologically feasible, is one of the major key factors. A newly introduced atmospheric pulsed laser deposition method, based on a flowing gas approach, was used for plasmonic metal nanoparticle (NP) film of silver. Contrary to vacuum, in this method, the ambient air restricts expansion of the ablation plume within 1 to 3 mm above the target surface. These sets constrain on the formation of NP film close to the ablation spot. For deposition on a widely spaced surface, ablation material was entrained in a flow of argon, supplied at $32 ms −1 , and effectively delivered to the substrate at $20 ms −1. The films produced were crystalline and particulate in nature, showing spectral plasmonic feature of surface plasmon resonance in the visible region. The film was directly tested in surface-enhanced Raman spectroscopy for chemical detection of crystal violet; the film with large particulates and aggregated crystallites was well-performed, showing enhanced Raman signals and detection sensitivity. Certainly, flowing gas atmospheric pulsed laser deposition seems a fast alternative to vacuum-pulsed laser deposition but needs further investigations to bring it in the industry for applications in sensor, catalysis, solar cell, and coating technology.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Silver nanoparticle films by flowing gas atmospheric pulsed laser deposition and application to surface‐enhanced Raman spectroscopy

Khan²,

et al. 2020

Int J Energy Res

“…As the Newtonian fluid flows under steady conditions in rigid wall channel, the flow is fully developed i.e. the velocity is maximum at center and zero at walls 43 . Such type of flow is usually called as poiseuille flow and the wall shear stress for this flow can be given as: …”

Section: Mathematical Model Descriptionmentioning

confidence: 99%

Performance improvement and thermodynamic assessment of microchannel heat sink with different types of ribs and cones

Zhang

Ahmad

et al. 2022

Sci Rep

The present study aims to investigate the performance of microchannel heat sink via numerical simulations, based on the first and second law of thermodynamics. The heat transfer and flow characteristics of rectangular microchannel heat sinks have been improved by adding six different types of surface enhancers. The cross-sections include rectangular, triangular, and hexagonal-shaped ribs and cones. The cones have been created from the same cross-sections of ribs by drafting them at an angle of 45° orthogonal to the base, which is expected to decrease the pressure drop, dramatically. The performance of ribs and cones has been evaluated using different parameters such as friction factor, wall shear stress, entropy generation rate, augmentation entropy generation number, thermal resistance, and transport efficiency of thermal energy. The results of the present study revealed that the novel effect of coning at an angle of 45° reduces frictional losses (Maximum pressure drop reduced is 85%), however; a compromise on thermal behavior has been shown (Maximum Nusselt number reduced is 25%). Similarly, the application of coning has caused a significant reduction in wall shear stress and friction factor which can lead to reducing the pumping power requirements. Moreover, triangular ribs have more ability to transfer thermal energy than rectangular and hexagonal ribs. Furthermore, it has been examined in the present study that the trend of total entropy generation rate for triangular ribs decreases up to Re = 400 and then increases onwards which means that thermal losses are more significant than frictional losses at lower Reynolds number. However, frictional losses dominate over thermal losses at higher Reynolds numbers, where vortex generation takes place, especially in triangular ribs.

Optimization of divertor design for Pakistan spherical tokamak

Alam

Khan²,

Abdullah³

et al. 2023

Kerntechnik

Handling the power deposition, reducing erosion effects, and plasma configuration are the key factors in the design of a divertor. The design of Pakistan Spherical Tokamak (PST) is based on double-null divertor configuration with actively cooled graphite targets at outer/inner strike point and peak heat flux range capacity of 0.1–0.3 MW/m2. The configuration of PST divertor module is designed with mock-up (used flat type tiles on baffles and dome) and cassette (support PFC and cooling channels) technology. Helium-cooled stage and water-cooled stage are two options for divertor. Therefore, one part of this research is focused on water-cooling system for the divertor. This paper presents the divertor design for PST with cooling channel and material analysis of the divertor, which is carried out in three phases. In the first phase, the plasma edge temperature, density, particle velocity, input power, heat flux, and surface temperature are estimated. In second phase, physics and engineering design of divertor system has been performed. In the third phase, COMSOL simulation has been performed to analyses the material properties, surface temperature rise (∆T °C) at stable heat flux, and thermal hydraulic system for the divertor. It is found from the analysis that the specific heat flux of 0.3 MW/m2 up to 3 s is the safe zone limit. The R & D work ratifies that manufacturing and installation processes are plausible for the proposed divertor design. This design is able to meet the requirement of PST. However, increasing time or specific heat flux beyond these limits would require redesigning of the cooling channel.