On the Need for Multidimensional Stirling Simulations

Given the cost and complication of simulating Stirling convertors, do we really need multidimensional modeling when one-dimensional capabilities exist? This paper provides a comprehensive description of when and why multidimensional simulation is needed

Stirling Analysis Comparison of Commercial Versus High-Order Methods

Recently, three-dimensional Stirling engine simulations have been accomplished utilizing commercial Computational Fluid Dynamics software. The validations reported can be somewhat inconclusive due to the lack of precise time accurate experimental results from engines, export control/proprietary concerns, and the lack of variation in the methods utilized. The last issue may be addressed by solving the same flow problem with alternate methods. In this work, a comprehensive examination of the methods utilized in the commercial codes is compared with more recently developed high-order methods. Specifically, Lele's compact scheme and Dyson's Ultra Hi-Fi method will be compared with the SIMPLE and PISO methods currently employed in CFD-ACE, FLUENT, CFX, and STAR-CD (all commercial codes which can in theory solve a three-dimensional Stirling model with sliding interfaces and their moving grids limit the effective time accuracy). We will initially look at one-dimensional flows since the current standard practice is to design and optimize Stirling engines with empirically corrected friction and heat transfer coefficients in an overall one-dimensional model. This comparison provides an idea of the range in which commercial CFD software for modeling Stirling engines may be expected to provide accurate results. In addition, this work provides a framework for improving current one-dimensional analysis codes

Medical and hygienic issues of sports attire for young people

Introduction: One of the risk factors for heath impairment of youths can be incompliance of requirements to choosing, storing, and treatment of sports attire together with the disturbance of personal body hygiene after sports activities. Purpose: To study medical and hygienic issues associated with youths awareness of hygienic requirements to the treatment of sports attire and footwear in sports activities. Materials and methods: Subject of research - college students of the regional centre in Belarus. 340 individuals aged between 15 and 18 were assessed. The methods of research were: questionnaire and statistical method «Statistics 6.1». Results: 88% of the interviewed persons responded that they chose their sports attire according to the design of clothes and their size without considering specific purpose of clothing. Following physical exercise 72% of the respondents do not change their sports shoes and internal footwear (socks). 31% of students do not have the habit of changing underwear after physical exercise. The answers to the questions “Do you wash your sports clothes after physical exercise?” and “Do you air and wash your sports footwear after physical exercise?” were definitely negative in 72% of the respondents and “don’t know” - in 12% of the interviewed. Moreover, 86% of students responded that they put their sports attire into the polyethylene bags and keep it until the next sports class. 84% of the respondents reported increased sweating and 27% - of skin acne on the back and upper limbs. Body pruritus was marked by 56% of students, pruritus in the foot area - by 46%. Direct association was revealed in subjects, who did not change their footwear after physical exercise and did not air their footwear, with the concerns in the foot area. The questions about the hygienic procedures were answered only by one seventh of the respondents. While going to the physical training class only 31% of the interviewed take with them the items of personal hygiene (soap, towel, tissues). Statistically important differences between sexes were not marked during the questionnaire analysis on all items. Conclusion: In sports activities college students irrespective of their gender show low level of awareness of sports attire hygiene and personal hygiene rules following physical training classes. Incompliance of the sports attire and footwear treatment rules were marked among the college students. Risk group for the development of skin and fungal foot pathology comprises young people who study in colleges of the regional center due to their incompliance of hygienic requirements to sports attire and footwear care

<Session 2: Fish Telemetry II>Expanding from creeks to hydroelectric diversion facilities - Construction and in situ evaluation of large half-duplex PIT tag antennas to evaluate fish entrainment at high velocity water diversions

19–22 May 2020 Kyoto, JapanThe implementation of Passive Integrated Transponder (PIT) technology for monitoring fish has historically required small detection areas in either creeks or constricted openings. Advancements in PIT technology have evolved to allow for much broader applications and larger monitoring areas. Custom fabricated large-scale PIT tag readers were used to estimate entrainment in two diversion tunnels (up to 3.8 m x 4.4 m) that experienced discharge as high as 31.1 cubic meters per second and operated in water depths of up to 6.4 m. The PIT arrays, consisting of three separate antennas stacked one on top of the other, were hand-molded from fiberglass into a hydrodynamic 'wing' shape. This design enabled the antennas to withstand high flows, while simultaneously detecting fish over the entire monitoring area of the diversion tunnels. This also allowed for the diversions to operate at full capacity and not be constrained to a modified smaller detection area. The antenna arrays and tag detection systems achieved optimal performance throughout the duration of the study. The antennas operated continuously for over a year, and monitored upwards of 99.0 percent of all diverted flows through the tunnels due to minimal required maintenance. A total of 220 unique detection events representing 58 fish were observed at the two diversion tunnels and equated to performance efficiency greater than 90 percent. The continuous operation and high detection efficiency achieved by the relatively large-scale PIT arrays confirms the success of this innovative deployment of PIT tag technology that was previously limited to small creeks and monitoring areas

Experimental and Computational Analysis of Unidirectional Flow Through Stirling Engine Heater Head

A high efficiency Stirling Radioisotope Generator (SRG) is being developed for possible use in long-duration space science missions. NASA s advanced technology goals for next generation Stirling convertors include increasing the Carnot efficiency and percent of Carnot efficiency. To help achieve these goals, a multi-dimensional Computational Fluid Dynamics (CFD) code is being developed to numerically model unsteady fluid flow and heat transfer phenomena of the oscillating working gas inside Stirling convertors. In the absence of transient pressure drop data for the zero mean oscillating multi-dimensional flows present in the Technology Demonstration Convertors on test at NASA Glenn Research Center, unidirectional flow pressure drop test data is used to compare against 2D and 3D computational solutions. This study focuses on tracking pressure drop and mass flow rate data for unidirectional flow though a Stirling heater head using a commercial CFD code (CFD-ACE). The commercial CFD code uses a porous-media model which is dependent on permeability and the inertial coefficient present in the linear and nonlinear terms of the Darcy-Forchheimer equation. Permeability and inertial coefficient were calculated from unidirectional flow test data. CFD simulations of the unidirectional flow test were validated using the porous-media model input parameters which increased simulation accuracy by 14 percent on average

Electrocatalytic Assisted Performance Enhancement for the Na-S Battery in Nitrogen-Doped Carbon Nanospheres Loaded with Fe.

Room temperature sodium-sulfur batteries have been considered to be potential candidates for future energy storage devices because of their low cost, abundance, and high performance. The sluggish sulfur reaction and the "shuttle effect" are among the main problems that hinder the commercial utilization of room temperature sodium-sulfur batteries. In this study, the performance of a hybrid that was based on nitrogen (N)-doped carbon nanospheres loaded with a meagre amount of Fe ions (0.14 at.%) was investigated in the sodium-sulfur battery. The Fe ions accelerated the conversion of polysulfides and provided a stronger interaction with soluble polysulfides. The Fe-carbon nanospheres hybrid delivered a reversible capacity of 359 mAh·g-1 at a current density of 0.1 A·g-1 and retained a capacity of 180 mAh·g-1 at 1 A·g-1, after 200 cycles. These results, combined with the excellent rate performance, suggest that Fe ions, even at low loading, are able to improve the electrocatalytic effect of carbon nanostructures significantly. In addition to Na-S batteries, the new hybrid is anticipated to be a strong candidate for other energy storage and conversion applications such as other metal-sulfur batteries and metal-air batteries

Stirling Analysis Comparison of Commercial VS. High-Order Methods

The conclusions are: Low Reynold s number, wall bounded flow allows economical use of large eddy simulation for turbulent transition modeling. UHF and Compact comparable at conjugate heat transfer. UHF much better for turbulence modeling Modern methods much more efficient than those currently available commercially

Fast Whole-Engine Stirling Analysis

This presentation discusses the simulation approach to whole-engine for physical consistency, REV regenerator modeling, grid layering for smoothness, and quality, conjugate heat transfer method adjustment, high-speed low cost parallel cluster, and debugging

Electrochemical Activation of Graphene at Low Temperature: The Synthesis of Three-Dimensional Nanoarchitectures for High Performance Supercapacitors and Capacitive Deionization

An electrochemical technique is developed to activate graphene oxide (GO) at relatively low temperature and assemble it into porous electrodes. The activation process is carried out in molten KOH by switching the polarity between 2 symmetrical GO electrodes. The electrochemically activated graphene (ECAG) showed a specific surface area as high as 2170 m² g^–1 and nanometer-sized pore created at a temperature as low as 450 °C. The ECAG electrode shows a significant enhancement in the electrochemical activity and thus improved electrochemical performance when being used as electrodes in supercapacitors and capacitive deionization (CDI) cells. A specific capacitance of 275 F g^–1 is obtained in 6 M KOH electrolyte, and 189 F g^–1 in 1 M NaCl electrolyte, which maintains 95% after 5000 cycles. The desalination capacity of the electrodes was evaluated by a batch mode electrosorption experiment. The ECAG electrode was able to remove 14.25 mg of salts per gram of the active materials and satisfy a high adsorption rate of 2.01 mg g^–1 min^–1. The low energy consumption of the CDI system is demonstrated by its high charge efficiency, which is estimated to be 0.83