scholarly journals Problems of irradiance characteristics measurement of solar simulators for ground spacecraft tests

2020 ◽  
Vol 4 (3) ◽  
pp. 129-140
Author(s):  
A. A. Shevchuk ◽  
O. V. Pastushenko ◽  
V. V. Dvirniy ◽  
G. V. Dvirniy ◽  
A. A. Filatov
Keyword(s):  
Heat Flux ◽  
Direct Measurement ◽  
Thermal State ◽  
Solar Spectrum ◽  
Experimental Tests ◽  
Thermal Vacuum ◽  
Solar Simulator ◽  
Vacuum Chambers ◽  
Mismatch Correction ◽  
Photoelectric Converters

The reliability of both spacecraft as a whole and of their systems is confirmed at the stage of complex ground-based experimental tests, including complex thermal vacuum tests. The thermal state of the test object in thermal vacuum chambers is obtaining, in particular, using a solar simulator. Radiometers based on silicon photoelectric converters are most often used to control the irradiance of a solar simulator under conditions of thermal vacuum tests. At the same time, an analysis of the features of silicon photoelectric converters shows that their direct measurement with the accuracy required for ground-based tests of spacecraft is impossible; their output is nonlinear, depends on the received spectrum, their own temperature and has long-term instability. The achieved measurement accuracy directly depends on the number and accuracy of the tools used and the methods of the necessary correction, of which the mismatch correction between the solar simulator spectrum and the solar spectrum is the most difficult and laborious. At the same time, spectrally nonselective heat flux radiometers are free from the above disadvantages. In the course of the experiment we carried out, the significant dependence of the accuracy of measuring the irradiance with radiometers based on silicon photoelectric converters on the received spectrum was confirmed. The conclusion is made that direct measurement by heat flux radiometers of the irradiance of the solar simulator is most justified under the conditions of thermal vacuum tests.

Thermal Environment Simulator for Vacuum Testing of Large Spacecraft

1988 ◽  
Vol 31 (1) ◽  
pp. 29-49
Author(s):  
T. Marshall
Keyword(s):  
Heat Flux ◽  
Vacuum Chamber ◽  
Lower Cost ◽  
Thermal Environment ◽  
Thermal Vacuum ◽  
Solar Simulator ◽  
Temperature Environment ◽  
Vertical Beam ◽  
Cold Walls ◽  
Vacuum Testing

A thermal environment simulator (TES) with 56 independently controllable temperature zones has been developed for Martin Marietta's Space Simulation Laboratory. This simulator is designed to test shuttle payloads in a thermal vacuum chamber with liquid nitrogen cold walls. The thermal environment simulator is an alternative to a 4.9-m (16-tt) diameter vertical beam solar simulator and two-axis gimbal system. The simulator can accommodate larger test articles at a lower cost. It provides complex heat flux distributions by surrounding the test articles with a multifaceted temperature environment. Issues resolved during initial operation included vacuum and cryogenic compatibility, control capabilities, instrumentation, calibration, heat flux uniformity, and reliability.

The effect of geothermal heat flux on the deglacial evolution of the Greenland ice sheet

2021 ◽  
Author(s):  
Parviz Ajourlou ◽  
François PH Lapointe ◽  
Glenn A Milne ◽  
Yasmina Martos
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Thermal State ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sampling Procedure ◽  
Geophysical Research ◽  
Geothermal Heat ◽  
Input Field ◽  
Uncertainty Estimates

<p>Geothermal heat flux (GHF) is known to be an important control on the basal thermal state of an ice sheet which, in turn, is a key factor in governing how the ice sheet will evolve in response to a given climate forcing. In recent years, several studies have estimated GHF beneath the Greenland ice sheet using different approaches (e.g. Rezvanbehbahani et al., Geophysical Research Letters, 2017; Martos et al., Geophysical Research Letters, 2018; Greve, Polar Data Journal, 2019). Comparing these different estimates indicates poor agreement and thus large uncertainty in our knowledge of this important boundary condition for modelling the ice sheet. The primary aim of this study is to quantify the influence of this uncertainty on modelling the past evolution of the ice sheet with a focus on the most recent deglaciation. We build on past work that considered three GHF models (Rogozhina et al., 2011) by considering over 100 different realizations of this input field. We use the uncertainty estimates from Martos et al. (Geophysical Research Letters, 2018) to generate GHF realisations via a statistical sampling procedure. A sensitivity analysis using these realisations and the Parallel Ice Sheet Model (PISM, Bueler and Brown, Journal of Geophysical Research, 2009) indicates that uncertainty in GHF has a dramatic impact on both the volume and spatial distribution of ice since the last glacial maximum, indicating that more precise constraints on this boundary condition are required to improve our understanding of past ice sheet evolution and, consequently, reduce uncertainty in future projections.</p>

Direct measurement of local heat flux during flow boiling in a minichannel

2020 ◽  
Vol 2020 (0) ◽  
pp. 0187
Author(s):  
Masanori Morisaki ◽  
Shota Minami ◽  
Koji Miyazaki ◽  
Tomohide Yabuki
Keyword(s):  
Heat Flux ◽  
Direct Measurement ◽  
Flow Boiling ◽  
Local Heat ◽  
Local Heat Flux

scholarly journals Some geophysical constraints to dynamic processes in the Southwestern Mediterranean

1996 ◽  
Vol 39 (6) ◽  
Author(s):  
V. Pasquale ◽  
M. Verdoya ◽  
P. Chiozzi
Keyword(s):  
Heat Flux ◽  
Continental Crust ◽  
Gravitational Collapse ◽  
Seismic Activity ◽  
Thermal State ◽  
Dynamic Processes ◽  
Oceanic Spreading ◽  
Evolutionary Scheme ◽  
Alboran Basin ◽  
Tectonic Framework

The total tectonic subsidence, thermal state and seismotectonic regime have been analysed to better constrain the dynamic processes which originated the basins of the Southwestern Mediterranean. It is argued that backarc extension and oceanic spreading are the possible and main processes which took place within a compressional framework, driven by the interaction between the African and European plates. As inferred by both subsidence and heat-flux data, in the central part of the Algerian-Balearic basin the crust is oceanic, 20 Ma old on average, originated by a spreading phase, which also affected the Ligurian-Provençal basin. The Alboran basin, which is underlain by stretched continental crust, shows an intermediate seismic activity and a few deep events, explainable by a gravitational collapse of cold lithosphere. After a review of the most recent geodynamical hypotheses, an evolutionary scheme is attempted envisaging the lateral continental escape of the Gibraltar arc. Within a convergent tectonic framework, some lithospheric material could translate almost perpendicular to the convergence direction, and undergo a lateral subduction process, secondary to the main boundary between plates.

scholarly journals Direct measurement of advective heat flux from several Yellowstone hot springs, Wyoming, USA

Geosphere ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 1860-1874 ◽  
Author(s):  
Nicholas McMillan ◽  
Peter Larson ◽  
Jerry Fairley ◽  
Joseph Mulvaney-Norris ◽  
Cary Lindsey
Keyword(s):  
Heat Flux ◽  
Direct Measurement ◽  
Hot Springs

Numerical Analysis to Predict the Temperature Distribution and Heat Transfer Rate From a Satellite Structure and Experimental Comparison

2012 ◽  
Author(s):  
Daniel T. Schwendtner ◽  
M. Ruhul Amin ◽  
David M. Klumpar
Keyword(s):  
Heat Flux ◽  
Numerical Analysis ◽  
Temperature Increase ◽  
Experimental Results ◽  
Vacuum System ◽  
Experimental Comparison ◽  
Bottom Plate ◽  
Flux Rate ◽  
Thermal Vacuum ◽  
Satellite Structure

Due to their small size and other attractive features, nanosatellites are becoming popular in space applications. Experimental investigation of the thermal behavior of such a satellite can be conducted in a laboratory setup using a thermal vacuum chamber to mimic the conditions of outer space. A small, cost effective thermal vacuum system was desired for performing thermal vacuum testing on nanosatellites. Numerical calculations and laboratory testing were performed as part of the design of this thermal vacuum system. A numerical method using the finite element method was employed to determine the amount of heat flux needed to be applied at the bottom plate of a satellite to achieve a certain rate of temperature increase in the plate. The numerical analysis was performed on a 40.5 kg satellite structure to predict the heat rate per unit area through its bottom surface when it was cycled in the temperature range of −40°C to +80°C with a rate of temperature change from 1°C/min to 5°C/min. A time dependent increase in temperature on the bottom wall was used as a boundary condition. The rest of the satellite walls were assumed to be insulated. Contact resistances between the components of the satellite structure were neglected. Temperature and heat flux distributions on various walls of the satellite were computed and reported in the study. From the numerical results, a maximum heat flux rate of 3,332 W/m2 was calculated on the bottom plate for a temperature increase rate of 1.5°C/min of the plate. A similar experimental setup was tested under similar conditions as a comparison and as a method to validate the thermal system design. Experimental results indicated a heat flux rate of 17,094 W/m2 through a test satellite. The difference between the numerical and experimental results is attributed to geometric differences between the numerical satellite model and the experimental test structure.

Validation of a Strategy for Deformation Monitoring of the Herschel Spacecraft Under Ambient Conditions by Photogrammetry

2009 ◽  
Vol 52 (1) ◽  
pp. 20-42
Author(s):  
Jafar Parian ◽  
Alessandro Cozzani ◽  
Matteo Appolloni ◽  
Gianluca Casarosa
Keyword(s):  
Local Oscillator ◽  
Deformation Monitoring ◽  
Ambient Conditions ◽  
Thermal Vacuum ◽  
Large Space ◽  
Balance Test ◽  
Vacuum Chambers ◽  
Network Simulations ◽  
Set Up ◽  
Global Accuracy

In the frame of the development of a videogrammetric system to be used in thermal/vacuum chambers at the ESA-ESTEC and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. The selected test set-up is the photogrammetric test of the Herschel Spacecraft Flight Model in the ESTEC Large Space Simulator. The videogrammetric system will be used to verify the Herschel Telescope alignment and Telescope positioning with respect to the Local Oscillator Unit inside the Large Space Simulator during thermal/vacuum/balance test phases. We designed a close-range photogrammetric network by heuristic simulation with a global accuracy of 1:100,000. A thermal/vacuum qualified videogrammetric system, which is able to work in vacuum and at cryo-temperatures in order to acquire images according to the designed network, was constructed by ESA-ESTEC Test Centre Division. In this paper we will present the videogrammetric system, the photogrammetric considerations, accuracy aspects, the result of photogrammetric network simulations, and real measurements. The results of real videogrammetric measurements of a dummy setup similar to the setup of Herschel spacecraft show a successful performance of the system in terms of functionality and accuracy.

Direct Measurement of Heat Flux Partitioning in Boiling Heat Transfer

2017 ◽  
Author(s):  
A. Richenderfer ◽  
A. Kossolapov ◽  
J. H. Seong ◽  
G. Saccone ◽  
M. Bucci ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Direct Measurement ◽  
Boiling Heat Transfer ◽  
Nuclear Reactors ◽  
Flow Boiling ◽  
Ir Camera ◽  
Flux Partitioning ◽  
Development And Validation ◽  
Transfer Models

The development and validation of mechanistic boiling heat transfer models has been a focal point in the efforts to improve the efficiency and profitability of power generation systems, e.g. nuclear reactors. The primary goal of these models is improving the accuracy of boiling heat transfer simulations and reducing the uncertainty margins that affect both the design and the safety of a system. However, the emergence of these models has also stimulated the need for high-fidelity experiments and experimental data for validation and verification. In this work we present first-of-a-kind data of heat flux partitioning in boiling heat transfer, obtained using cutting-edge diagnostics and post-processing techniques. A HSV camera was used to visualize the boiling surface at 10,000 frames per second with simultaneous front and side views of the two-phase flow. A high-speed IR camera was used to capture the 2-D radiative signal from the boiling surface to visualize bubble nucleation, growth and detachment at a 115 μm/pixel resolution at 2,500 frames per second. A coupled radiation-conduction calibration model was used to calibrate the IR data and extract the full local temperature and heat flux distributions on the boiling surface, which enable a direct measurement of the partitioned heat fluxes. Here we report the results of investigations performed in flow boiling conditions with a mass flux of 500 kg/m2/s, at atmospheric pressure and 10 K of subcooling. These data will be leveraged to inform the development and validation of the next generation of mechanistic boiling heat transfer models, to be used in Computational Fluid Dynamics (CFD) codes for the design and the safety analysis of nuclear reactors.

Sign in / Sign up

Export Citation Format

Share Document