New method for transient cold wall heat flux measurements for unlimited exposure times

Abstract This paper presents a new method to measure high cold wall surface heat fluxes temporally resolved. It is based on a system identification approach, the so-called Non-Integer System Identification (NISI) method, which allows to correlate the surface heat flux to one single in-depth temperat...

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Main Authors: Fabian Hufgard, Christian Duernhofer, Clemens Mueller, Stefan Loehle
Format: Article
Language:English
Published: Nature Portfolio 2025-05-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-03245-8
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author Fabian Hufgard
Christian Duernhofer
Clemens Mueller
Stefan Loehle
author_facet Fabian Hufgard
Christian Duernhofer
Clemens Mueller
Stefan Loehle
author_sort Fabian Hufgard
collection DOAJ
description Abstract This paper presents a new method to measure high cold wall surface heat fluxes temporally resolved. It is based on a system identification approach, the so-called Non-Integer System Identification (NISI) method, which allows to correlate the surface heat flux to one single in-depth temperature measurement. Here, the model parameters are found experimentally by non-destructive calibration of the actual sensor hardware. The key feature of the new method is that the sensing wall segment is actively water-cooled at the backside, so that a transient, i.e. temporally varying, heat flux can be determined over long periods of time without damaging the sensing element. In the paper, the NISI model equation is derived from the heat equation considering this cooled backside boundary condition. We prove the useful applicability of our new approach by assessing data from a numerical thermal simulation. The determined heat flux shows excellent agreement with the known input data.
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spelling doaj-art-371d3aca0a2a4128b1f50b84ab3022912025-08-20T01:59:56ZengNature PortfolioScientific Reports2045-23222025-05-0115111010.1038/s41598-025-03245-8New method for transient cold wall heat flux measurements for unlimited exposure timesFabian Hufgard0Christian Duernhofer1Clemens Mueller2Stefan Loehle3High Enthalpy Flow Diagnostics Group (HEFDiG), Institute of Space Systems, University of StuttgartHigh Enthalpy Flow Diagnostics Group (HEFDiG), Institute of Space Systems, University of StuttgartHigh Enthalpy Flow Diagnostics Group (HEFDiG), Institute of Space Systems, University of StuttgartHigh Enthalpy Flow Diagnostics Group (HEFDiG), Institute of Space Systems, University of StuttgartAbstract This paper presents a new method to measure high cold wall surface heat fluxes temporally resolved. It is based on a system identification approach, the so-called Non-Integer System Identification (NISI) method, which allows to correlate the surface heat flux to one single in-depth temperature measurement. Here, the model parameters are found experimentally by non-destructive calibration of the actual sensor hardware. The key feature of the new method is that the sensing wall segment is actively water-cooled at the backside, so that a transient, i.e. temporally varying, heat flux can be determined over long periods of time without damaging the sensing element. In the paper, the NISI model equation is derived from the heat equation considering this cooled backside boundary condition. We prove the useful applicability of our new approach by assessing data from a numerical thermal simulation. The determined heat flux shows excellent agreement with the known input data.https://doi.org/10.1038/s41598-025-03245-8Transient heat flux measurementInverse problem
spellingShingle Fabian Hufgard
Christian Duernhofer
Clemens Mueller
Stefan Loehle
New method for transient cold wall heat flux measurements for unlimited exposure times
Scientific Reports
Transient heat flux measurement
Inverse problem
title New method for transient cold wall heat flux measurements for unlimited exposure times
title_full New method for transient cold wall heat flux measurements for unlimited exposure times
title_fullStr New method for transient cold wall heat flux measurements for unlimited exposure times
title_full_unstemmed New method for transient cold wall heat flux measurements for unlimited exposure times
title_short New method for transient cold wall heat flux measurements for unlimited exposure times
title_sort new method for transient cold wall heat flux measurements for unlimited exposure times
topic Transient heat flux measurement
Inverse problem
url https://doi.org/10.1038/s41598-025-03245-8
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AT stefanloehle newmethodfortransientcoldwallheatfluxmeasurementsforunlimitedexposuretimes