scholarly journals Power transport efficiency during O-X-B 2nd harmonic electron cyclotron heating in a helicon linear plasma device

2021 ◽  
Author(s):  
Juan Francisco Caneses Marin ◽  
Cornwall Lau ◽  
Richard H Goulding ◽  
Tim S Bigelow ◽  
Ted M Biewer ◽  
...  
Keyword(s):  
Microwave Power ◽  
Mode Conversion ◽  
Heating System ◽  
Heat Fluxes ◽  
Electron Heating ◽  
Magnetic Field Profile ◽  
Microwave Beam ◽  
Narrow Region ◽  
Plasma Device ◽  
The Impact

Abstract The principal objective of this work is to report on the power coupled to a tungsten target in the Proto-MPEX device during oblique injection of a microwave beam (< 70 kW at 28 GHz) into a high-power (~100 kW at 13.56 MHz) over-dense (n_e>1×10^19 m^(-3)) deuterium helicon plasma column. The experimental setup, electron heating system, electron heating scheme, and IR thermographic diagnostic for quantifying the power transport is described in detail. It is demonstrated that the power transported to the target can be effectively controlled by adjusting the magnetic field profile. Using this method, heat fluxes up to 22 MWm-2 and power transport efficiencies in the range of 17-20% have been achieved using 70 kW of microwave power. It is observed that most of the heat flux is confined to narrow region at the plasma periphery. Ray-tracing calculations are presented which indicate that power is coupled to the plasma electrons via an O-X-B mode conversion process. Calculations indicate that the microwave power is absorbed in a single pass at the plasma periphery via collisions and in the over-dense region via 2nd harmonic cyclotron resonance of the electron Bernstein wave. The impact of these results is discussed in the context of MPEX.

scholarly journals Characterization of the subsurface urban heat island and its sources in the Milan city area, Italy

2021 ◽  
Author(s):  
Alberto Previati ◽  
Giovanni B. Crosta
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Heat Fluxes ◽  
Shallow Aquifer ◽  
Heat Island ◽  
Groundwater Temperature ◽  
City Area ◽  
Groundwater Environment ◽  
Urban Heat ◽  
The Impact

AbstractUrban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

scholarly journals The Effect of Atmosphere–Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 688
Author(s):  
Soline Bielli ◽  
Christelle Barthe ◽  
Olivier Bousquet ◽  
Pierre Tulet ◽  
Joris Pianezze
Keyword(s):  
Tropical Cyclone ◽  
Mixed Layer ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Ocean Mixed Layer ◽  
Surface Cooling ◽  
Southwest Indian Ocean ◽  
Left Hand ◽  
Sea Surface Cooling ◽  
The Impact

A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

scholarly journals Influence of Land Cover and Soil Moisture on the Horizontal Distribution of Sensible and Latent Heat Fluxes in Southeast Kansas during IHOP_2002 and CASES-97

2007 ◽  
Vol 8 (1) ◽  
pp. 68-87 ◽  
Author(s):  
Margaret A. LeMone ◽  
Fei Chen ◽  
Joseph G. Alfieri ◽  
Mukul Tewari ◽  
Bart Geerts ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Latent Heat ◽  
Land Surface ◽  
Field Experiments ◽  
Time Of Day ◽  
Horizontal Distribution ◽  
Heat Fluxes ◽  
Surface Model ◽  
Green Vegetation ◽  
The Impact

Abstract Analyses of daytime fair-weather aircraft and surface-flux tower data from the May–June 2002 International H2O Project (IHOP_2002) and the April–May 1997 Cooperative Atmosphere Surface Exchange Study (CASES-97) are used to document the role of vegetation, soil moisture, and terrain in determining the horizontal variability of latent heat LE and sensible heat H along a 46-km flight track in southeast Kansas. Combining the two field experiments clearly reveals the strong influence of vegetation cover, with H maxima over sparse/dormant vegetation, and H minima over green vegetation; and, to a lesser extent, LE maxima over green vegetation, and LE minima over sparse/dormant vegetation. If the small number of cases is producing the correct trend, other effects of vegetation and the impact of soil moisture emerge through examining the slope ΔxyLE/ΔxyH for the best-fit straight line for plots of time-averaged LE as a function of time-averaged H over the area. Based on the surface energy balance, H + LE = Rnet − Gsfc, where Rnet is the net radiation and Gsfc is the flux into the soil; Rnet − Gsfc ∼ constant over the area implies an approximately −1 slope. Right after rainfall, H and LE vary too little horizontally to define a slope. After sufficient drying to produce enough horizontal variation to define a slope, a steep (∼−2) slope emerges. The slope becomes shallower and better defined with time as H and LE horizontal variability increases. Similarly, the slope becomes more negative with moister soils. In addition, the slope can change with time of day due to phase differences in H and LE. These trends are based on land surface model (LSM) runs and observations collected under nearly clear skies; the vegetation is unstressed for the days examined. LSM runs suggest terrain may also play a role, but observational support is weak.

scholarly journals Averaging-Related Biases in Monthly Latent Heat Fluxes

2012 ◽  
Vol 29 (7) ◽  
pp. 974-986 ◽  
Author(s):  
Paul J. Hughes ◽  
Mark A. Bourassa ◽  
Jeremy J. Rolph ◽  
Shawn R. Smith
Keyword(s):  
Latent Heat ◽  
Classical Method ◽  
Surface Flux ◽  
Heat Fluxes ◽  
Western Boundary ◽  
State University ◽  
Boundary Current ◽  
Surface Energy Fluxes ◽  
Temporal Averaging ◽  
The Impact

Abstract Seasonal-to-multidecadal applications that require ocean surface energy fluxes often require accuracies of surface turbulent fluxes to be 5 W m−2 or better. While there is little doubt that uncertainties in the flux algorithms and input data can cause considerable errors, the impact of temporal averaging has been more controversial. The biases resulting from using monthly averaged winds, temperatures, and humidities in the bulk aerodynamic formula (i.e., the so-called classical method) to estimate the monthly mean latent heat fluxes are shown to be substantial and spatially varying in a manner that is consistent with most prior work. These averaging-related biases are linked to nonnegligible submonthly covariances between the wind, temperature, and humidity. To provide additional insight into the averaging-related bias, the methodology behind the third-generation Florida State University monthly mean surface flux product (FSU3) is detailed to highlight additional sources of errors in gridded datasets. The FSU3 latent heat fluxes suffer from this averaging-related bias, which can be as large as 90 W m−2 in western boundary current regions during winter and can exceed 40 W m−2 in synoptically active portions of the tropics. The regional impacts of these biases on the mixed layer temperature tendency are shown to demonstrate that the error resulting from applying the classical method is physically substantial.

Suggestions to the test procedure for technical means of protection of steel welded domestic LPG gas cylinders from physical destruction in fire

2021 ◽  
pp. 67-72
Author(s):  
Владимир Леонидович Малкин ◽  
Владимир Александрович Угорелов ◽  
Петр Алексеевич Леончук ◽  
Руслан Андреевич Загуменников
Keyword(s):  
Coming Out ◽  
Test Procedure ◽  
Video Recording ◽  
Heating System ◽  
Measuring System ◽  
Cylinder Surface ◽  
In Fire ◽  
Gas Leaks ◽  
The Impact ◽  
Gas Cylinders

Разработана методика проведения испытаний технических средств защиты стальных сварных бытовых баллонов для сжиженных углеводородных газов (СУГ) от физического разрушения при воздействии на них пожара. В методике содержатся требования к отбору газовых баллонов, рассматриваемым модельным сценариям, установке для испытаний, мероприятиям по подготовке испытаний, порядку их проведения, к отчету о проведении испытаний. Использование предлагаемой методики позволит с высокой степенью достоверности оценивать эффективность применения технических средств защиты стальных бытовых баллонов для СУГ от физического разрушения при воздействии пожара. The paper contains proposals for inclusion in the testing methodology for technical means of protecting gas cylinders from physical destruction. The proposals relate to the choice of typical scenarios characteristic for emergencies and fire development in a room with LPG cylinders: the ingress of cylinders into the fire center, the impact on the cylinder surface of the heat flow of the adjacent fire center; the impact on the surface of the cylinder of LPG vapors jet combustion, simulating the effect of combustion of LPG vapors coming out of the outlet of the valve (safety valve or membrane) of the adjacent cylinder. The design of the installation for testing cylinders in accordance with the above scenarios is presented. There are given requirements for the test preparation procedure, including the verification of documentation, installation of technical protective equipment, filling and delivery of cylinders, checking for gas leaks from cylinders after delivery, installation for testing. A detailed description of the installation procedure is given in accordance with the presented diagrams for various test scenarios. The basic diagrams of the measuring system for the pressure inside the cylinder, mounting of thermocouples on the wall of the cylinder, and remote supply of liquid fuel to trays are described. There is described the test procedure, which consists of turning on the recording systems, gas supplying to the installation, activating the cylinder heating system, video recording of the experiment with timing, closing the valve in front of the pressure sensor after the end of combustion, discharging LPG from the sealed cylinder to the burner. The requirements for the composition of the test report are given, which make it possible to confirm the reliability of the experiments.

Sign in / Sign up

Export Citation Format

Share Document