scholarly journals The Influence of Thermoelectric Effects on the Maximum Temperature in a Radially Constricted Gas Discharge Between Electrodes

1961 ◽  
Vol 14 (2) ◽  
pp. 279
Author(s):  
PW Seymour
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Gas Discharge ◽  
Maximum Temperature ◽  
Thermoelectric Effects

In an earlier paper the author provided a method for estimating the maximum temperature in a steady-state, centrally constricted, highly ionized deuterium discharge between electrodes. The analysis applied to discharges not too long, so that bremsstrahlung loss could be neglected compared to the main heat loss by conduction to the electrodes, and thermoelectric effects were not included.

scholarly journals Corrigenda

1961 ◽  
Vol 14 (3) ◽  
pp. 435
Keyword(s):  
Gas Discharge ◽  
Maximum Temperature ◽  
Thermoelectric Effects

The Influence of Thermoelectric Effects on the Maximum Temperature in a Radially Constricted Gas Discharge between Electrodes

scholarly journals Estimation of the Maximum Temperature in a Radially Constricted Gas Discharge Between Electrodes

1961 ◽  
Vol 14 (1) ◽  
pp. 129
Author(s):  
PW Seymour
Keyword(s):  
Heat Conduction ◽  
Steady State ◽  
Free Boundary ◽  
Cross Section ◽  
Discharge Tube ◽  
Boundary Surface ◽  
Gas Discharge ◽  
Maximum Temperature ◽  
Main Question ◽  
The Cross

A steady-state deuterium discharge between two electrodes is considered and the free boundary surface of the plasma is assumed thermally insulated when pinched away from the walls of the discharge tube. Cooling is therefore by heat conduction to the electrodes, compared to which bremsstrahlung loss is shown to be negligible if the discharge is not too long. The main question examined is how much the maximum temperature T m can be raised by constricting the cross section of the discharge near the centre.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Natalie R. Smith ◽  
Timothy C. Allison ◽  
Jason C. Wilkes ◽  
Christopher Clarke ◽  
Michael Cave
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital for acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow all facility components to reach a steady-state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: (1) the method is not susceptible to effects due to thermal heat loss in the facility, and (2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1 °C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady-state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

2018 ◽  
Author(s):  
Natalie R. Smith ◽  
Christopher Clarke ◽  
Timothy C. Allison ◽  
Michael Cave ◽  
Jason C. Wilkes
Keyword(s):  
Steady State ◽  
Heat Loss ◽  
Performance Metrics ◽  
Aerodynamic Performance ◽  
Performance Data ◽  
Testing Time ◽  
Southwest Research Institute ◽  
Significant Difference ◽  
Thermal Measurements ◽  
Isentropic Efficiency

Full-thermal heat-soak of machinery is vital to acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow for all facility components to reach a steady state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: 1) the method is not susceptible to effects due to thermal heat loss in the facility, and 2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1°C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1998 ◽  
Vol 120 (2) ◽  
pp. 405-409 ◽  
Author(s):  
P. Monmousseau ◽  
M. Fillon ◽  
J. Freˆne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

scholarly journals HELIUM RELEASE FROM 12Cr18Ni10Ti STAINLESS STEEL AFTER IMPACT OF STEADY STATE GLOW DISCHARGE He PLASMA

2021 ◽  
pp. 32-36
Author(s):  
G.P. Glazunov ◽  
M.N. Bondarenko ◽  
A.L. Konotopskiy ◽  
I.E. Garkusha ◽  
S.M. Maznichenko ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Steady State ◽  
Glow Discharge ◽  
Thermal Desorption ◽  
Gas Discharge ◽  
Plasma Pressure ◽  
Discharge Voltage ◽  
Probe Surface ◽  
Physical Mechanisms ◽  
He Atom

The thermal desorption experiments were carried out to study the process of helium outgassing from the stainless steel 12Cr18Ni10Ti after exposure to a steady state glow discharge (GD) plasma in He atmosphere. The currentvoltage characteristics in different plasma regimes have been measured and estimation of He ions energy has been made. Measurements of He release from the stainless steel probes showed the saturation of probe surface with He after the fluencies of ~ 4 ∙ 1019 ion/cm2. The value of He outgassing strongly depends on the regime of GD plasma: pressure of work gas, discharge voltage, etc. Several maximums, including the maximum at the temperature of 100…150 °C, were registered in the He desorption curves that indicated different He atom states on the surface and in the nearest surface bulk. Physical mechanisms of such He outgassing are discussed.

Determination of Thermal Conductivity of Soils: A Need for Computing Heat Loss Through Buried Submarine Pipelines

1982 ◽  
Vol 22 (04) ◽  
pp. 558-562 ◽  
Author(s):  
P.C. Rawat ◽  
S.L. Agarwal
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Crude Oil ◽  
Rheological Properties ◽  
Heat Loss ◽  
Experimental Results ◽  
Dry Density ◽  
Empirical Relationships ◽  
Thermal Conductivities

Abstract An important parameter required for computing heat loss through buried submarine pipelines transporting crude oil is the thermal conductivity of soils. This paper describes an apparatus designed for determination of the thermal conductivity of soils at the desired moisture/ density condition in the laboratory under steady-state conditions. Experimental results on the three soils studied show that thermal conductivity increases as dry density increases at a constant moisture content and that it increases as water content increases at constant dry density. These results confirm the trends isolated earlier by Kersten. The experimental results are compared with the available empirical relationships. Kersten's relation is observed to predict the thermal conductivity of these soils reasonably. The predictions from Makowski and Mochlinski's relation (quoted by Szilas) are not good but improve if the sum of silt and clay fractions is treated as a clay fraction in the computation. Introduction Submarine pipelines are used extensively for transporting crude oil from offshore to other pipelines offshore or onshore. These pipelines usually are steel pipes covered with a coating of concrete. They often are buried some depth below the mudline. The rheological properties of different crude oils vary, and their viscosities increase with a decrease in temperature. Below some temperature, the liquid oil tends to gel. Therefore, for efficient transportation, the crude must be at a relatively high temperature so that it has a low viscosity. The temperature of the soil/water system surrounding a submarine pipeline is usually lower than that of oil. This temperature difference induces heat to flow from the oil to the environment, and the temperature of the oil decreases as it travels along the length of the pipeline. One must ensure that this temperature reduction does not exceed desirable limits dictated by the rheological properties of oil and by the imperatives of efficient economic properties of oil and by the imperatives of efficient economic transportation. Thus the analytical problem is to predict the temperature of crude in the pipeline some distance away from the input station. To do so, knowledge of the overall heat transfer coefficient for the pipeline is required, for which, in turn, it is necessary to know the thermal conductivities of the oil, the pipeline materials and its coating, and the soil. This paper presents thermal conductivities of soils determined in the laboratory under steady-state conditions and also presents a comparison of the test results of three soils with values determined from existing empirical relationships. Literature Review Heat moves spontaneously from higher to lower temperatures. In a completely dry porous body, transmission of heat can take place not only by conduction through the solid framework of the body and the air in the pores but also by convection and radiation between the walls of a pore and by macro- and microdistillation. In soils, however, it can be ascribed essentially to conduction, a molecular phenomenon that can be expressed in terms of experimentally determined coefficients of conductivity or resistivity, although these actually may include microdistillation and other mechanisms. SPEJ p. 558

The Polytropic Approach in Modelling Compressible Flows Through Constant Cross-Section Pipes

2021 ◽  
Author(s):  
Alessandro Ferrari ◽  
Oscar Vento ◽  
Tantan Zhang
Keyword(s):  
Steady State ◽  
Cross Section ◽  
Compressible Flows ◽  
Analytical Formula ◽  
Local Maximum ◽  
Wall Friction ◽  
Numerical Code ◽  
Maximum Temperature ◽  
Constant Cross Section ◽  
Polytropic Exponent

Abstract A compressible flow with wall friction has been predicted in a constant cross-section duct by means of a barotropic modelling approach, and new analytical formulas have been proposed that also allow any possible heat transfer to the walls to be taken into account. A comparison between the distributions of the steady-state flow properties, pertaining to the new formulas, and to those of a classic Fanno analysis has been performed. In order to better understand the limits of the polytropic approach in nearly chocked flow applications, a numerical code, which adopts a variable polytropic coefficient along the duct, has been developed. The steady-state numerical distributions along the pipe, obtained for either a viscous adiabatic or an inviscid diabatic flow by means of this approach, coincide with those of the Fanno and Rayleigh models for Mach numbers up to 1. A constant polytropic exponent can be adopted for a Fanno flow that is far from choking conditions, while it cannot be adopted for the simulation of a Rayleigh flow, even when the flow is not close to choking conditions. Finally, under the assumption of diabatic flows with wall friction, the polytropic approach, with a constant polytropic exponent, is shown to be able to accurately approximate cases in which no local maximum is present for the temperature along the duct. The Mach number value at the location where the local maximum temperature possibly occurs has been obtained by means of a new analytical formula.

Efficient Thermal Analysis of Lab-Grown Diamond Heat Spreaders

2021 ◽  
Author(s):  
Zihao Yuan ◽  
Tao Zhang ◽  
Jeroen Van Duren ◽  
Ayse K. Coskun
Keyword(s):  
Steady State ◽  
Real World ◽  
High Performance ◽  
Silicon Layer ◽  
Maximum Temperature ◽  
Cooling Performance ◽  
Thermal Models ◽  
Heat Spreaders ◽  
Transient Simulations ◽  
Transient Thermal

Abstract Lab-grown diamond heat spreaders are becoming attractive solutions compared to traditional copper heat spreaders due to their high thermal conductivity, the ability to directly bond them on silicon, and allow for an ultra-thin silicon layer. Researchers have developed various thermal models and prototypes of lab-grown diamond heat spreaders to evaluate their cooling performance and heat spreading ability. The majority of existing thermal models are built using finite-element method (FEM) based simulators such as COMSOL and ANSYS. However, such commercial simulators are computationally expensive and lead to long solution times along with large memory requirements. These limitations make commercial simulators unsuitable for evaluating numerous design alternatives or runtime scenarios for real-world high-performance processors. Because of this modeling challenge, none of the existing works have evaluated the thermal behavior of lab-grown diamond heat spreaders on real-world high-performance processors running realistic application benchmarks. Recently, we have developed a parallel compact thermal simulator, PACT, that is able to carry out fast and accurate steady-state and transient thermal simulations and can be extended to support emerging integration and cooling technologies. In this paper, we use PACT to evaluate the steady-state and transient cooling performance of lab-grown diamond heat spreaders against traditional copper heat spreaders on various real-world high-performance processors (e.g., Intel i7 6950X, IBM Power9, and PicoSoC). By using PACT with architectural performance and power simulators such as Sniper and McPAT, we are able to run transient simulations with realistic benchmarks. Simulation results show that lab-grown diamond heat spreaders achieve maximum temperature and thermal gradient reductions of up to 26.73 °C and 13.75 °C when compared to traditional copper heat spreaders, respectively. The maximum steady-state and transient simulation times of PACT for the real-world high-performance chips and realistic applications used in our experiments are 259 s and 22 min, respectively.

scholarly journals Sensitivity of Characterizing the Heat Loss Coefficient through On-Board Monitoring: A Case Study Analysis

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3322 ◽  
Author(s):  
Marieline Senave ◽  
Staf Roels ◽  
Stijn Verbeke ◽  
Evi Lambie ◽  
Dirk Saelens
Keyword(s):  
Sensitivity Analysis ◽  
Steady State ◽  
Data Analysis ◽  
Heat Loss ◽  
Input Data ◽  
Loss Coefficient ◽  
Wide Range ◽  
Board Monitoring ◽  
The Impact

Recently, there has been an increasing interest in the development of an approach to characterize the as-built heat loss coefficient (HLC) of buildings based on a combination of on-board monitoring (OBM) and data-driven modeling. OBM is hereby defined as the monitoring of the energy consumption and interior climate of in-use buildings via non-intrusive sensors. The main challenge faced by researchers is the identification of the required input data and the appropriate data analysis techniques to assess the HLC of specific building types, with a certain degree of accuracy and/or within a budget constraint. A wide range of characterization techniques can be imagined, going from simplified steady-state models applied to smart energy meter data, to advanced dynamic analysis models identified on full OBM data sets that are further enriched with geometric info, survey results, or on-site inspections. This paper evaluates the extent to which these techniques result in different HLC estimates. To this end, it performs a sensitivity analysis of the characterization outcome for a case study dwelling. Thirty-five unique input data packages are defined using a tree structure. Subsequently, four different data analysis methods are applied on these sets: the steady-state average, Linear Regression and Energy Signature method, and the dynamic AutoRegressive with eXogenous input model (ARX). In addition to the sensitivity analysis, the paper compares the HLC values determined via OBM characterization to the theoretically calculated value, and explores the factors contributing to the observed discrepancies. The results demonstrate that deviations up to 26.9% can occur on the characterized as-built HLC, depending on the amount of monitoring data and prior information used to establish the interior temperature of the dwelling. The approach used to represent the internal and solar heat gains also proves to have a significant influence on the HLC estimate. The impact of the selected input data is higher than that of the applied data analysis method.

Sign in / Sign up

Export Citation Format

Share Document