Inverse Heat Conduction Errors From Temperature Bias in Thin Film Sensors: Effect of Contact Resistance

2011 ◽  
Author(s):  
Keith A. Woodbury ◽  
Jonathan W. Woolley
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Heat Conduction ◽  
Contact Resistance ◽  
Surface Temperature ◽  
Temperature Error ◽  
Lead Wire ◽  
Inverse Heat Conduction ◽  
Detailed Model ◽  
Thin Film Sensors

Thin platinum resistance thermometers (herein called thin film sensors) are often used in applications where rapid measurements of surface temperature are required. These gages are typically vapor deposited onto a non-conducting substrate surface and electrically connected with small wires through access holes to the surface. The time response of the gage is measured in milliseconds and surface temperature data obtained with this gage is often combined with a pseudo-inverse heat conduction algorithm to provide information about the surface heat flux. However, the thermal mass of the connecting wires, though small in absolute terms, is large compared to that of the thin film, and the capacitive effect of this mass gives rise to distortions in the temperature field in the area of the gage, resulting in a small error in the sensed temperature. This temperature error, when used in the inversion for heat flux, also results in an error. In this report, a detailed model of a particular thin film gage is used to compute the response of the sensor to supposed heating conditions. The effect of contact resistance between the parent material and the lead wire connections is investigated. The response of the sensor, with and without the contact resistance, and the undisturbed surface temperature are compared to estimate the temperature error. Finally, the error in the computed heat flux is determined. A simple approximate technique based on superposition is applied to account for the sensor dynamics and correct the error in the estimated heat flux.

Inverse Analysis of In-Cylinder Gas-Wall Boundary Conditions: Investigation of a Yittria Stabilized Zirconia Thermal Barrier Coating for Homogeneous Charge Compression Ignition

2016 ◽  
Author(s):  
Ryan O’Donnell ◽  
Tommy Powell ◽  
Mark Hoffman ◽  
Zoran Filipi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Conduction ◽  
Surface Temperature ◽  
Inverse Analysis ◽  
Fast Response ◽  
Thermal Barrier ◽  
Temperature Profiles ◽  
Inverse Heat Conduction ◽  
Cycle Efficiency

Thermal Barrier Coatings (TBC) applied to in-cylinder surfaces of a Low Temperature Combustion (LTC) engine provide opportunities for enhanced cycle efficiency via two mechanisms: (i) positive impact on thermodynamic cycle efficiency due to combustion/expansion heat loss reduction, and (ii) enhanced combustion efficiency. Heat released during combustion elevates TBC surface temperatures, directly impacting gas-wall heat transfer. Determining the magnitude and phasing of the associated TBC surface temperature swing is critical for correlating coating properties with the measured impact on combustion and efficiency. Although fast-response thermocouples provide a direct measurement of combustion chamber surface temperature in a metal engine, the temperature and heat flux profiles at the TBC-treated gas-wall boundary are difficult to measure directly. Thus, a technique is needed to process the signal measured at the sub-TBC sensor location and infer the corresponding TBC surface temperature profile. This task can be described as an Inverse Heat Conduction Problem (IHCP), and it cannot be solved using the conventional analytic/numeric techniques developed for ‘direct’ heat flux measurements. This paper proposes using an Inverse Heat Conduction solver based on the Sequential Function Specification Method (SFSM) to estimate heat flux and temperature profiles at the wall-gas boundary from measured sub-TBC temperature. The inverse solver is validated ex situ under HCCI like thermal conditions in a custom fabricated radiation chamber where fast-response thermocouples are exposed to a known heat pulse in a controlled environment. The analysis is extended in situ, to evaluate surface conditions in a single-cylinder, gasoline-fueled, HCCI engine. The resulting SFSM-based inverse analysis provides crank angle resolved TBC surface temperature profiles over a host of operational conditions. Such metrics may be correlated with TBC thermophysical properties to determine the impact(s) of material selection on engine performance, emissions, heat transfer, and efficiencies. These efforts will also guide next-generation TBC design.

Inverse Heat Conduction Using Measured Back Surface Temperature and Heat Flux

2010 ◽  
Vol 24 (1) ◽  
pp. 95-103 ◽  
Author(s):  
Jianhua Zhou ◽  
Yuwen Zhang ◽  
J. K. Chen ◽  
Z. C. Feng
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Surface Temperature ◽  
Back Surface ◽  
Inverse Heat Conduction

Inverse Heat Conduction in a Composite Slab With Pyrolysis Effect and Temperature-Dependent Thermophysical Properties

2009 ◽  
Author(s):  
Jianhua Zhou ◽  
Yuwen Zhang ◽  
J. K. Chen ◽  
Z. C. Feng
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Surface Temperature ◽  
Thermophysical Properties ◽  
Laser Heating ◽  
Front Surface ◽  
Back Surface ◽  
Inverse Heat Conduction ◽  
Temperature Dependent ◽  
Composite Slab

The inverse heat conduction problem (IHCP) in a one-dimensional composite slab with rate-dependent pyrolysis chemical reaction and outgassing flow effects is investigated using the conjugate gradient method (CGM). The thermal properties of the composites are considered to be temperature-dependent, which makes the IHCP a nonlinear problem. The inverse problem is formulated in such a way that the front-surface heat flux is chosen as the unknown function to be recovered, and the front-surface temperature is computed as a by-product of the IHCP algorithm, which uses back-surface temperature and heat flux measurements. The proposed IHCP formulation is then applied to solve the IHCP in an organic composite slab whose front surface is subjected to high intensity periodic laser heating. It is shown that an extra temperature sensor located at an interior position is necessary since the organic composites usually possess a very low thermal conductivity. It is also found that the frequency of the periodic laser heating flux plays a dominant role in the inverse solution accuracy. In addition, the robustness of the proposed algorithm is demonstrated by its capability in handling the case of thermophysical properties with random errors.

A Comparison of Radiation Versus Convection Calibration of Thin-Film Heat Flux Gauges

1999 ◽  
Author(s):  
D. E. Smith ◽  
J. V. Bubb ◽  
O. Popp ◽  
T. E. Diller ◽  
Stephen J. Hevey
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Surface Temperature ◽  
Temperature Response ◽  
Turbine Rotor ◽  
Separate Experiment ◽  
Measured Temperature ◽  
Conduction Model ◽  
Time Resolved ◽  
Turbine Rotor Blade

Abstract A transient, in-situ method was examined for calibrating thin-film heat flux gauges using experimental data generated from both convection and radiation tests. Also, a comparison is made between this transient method and the standard radiation substitution calibration technique. Six Vatell Corporation HFM-7 type heat flux gauges were mounted on the surface of a 2-D, first-stage turbine rotor blade. These gauges were subjected to radiation from a heat lamp and in a separate experiment to a convective heat flux generated by flow in a transonic cascade wind tunnel. A second set of convective tests were performed using jets of cooled air impinging on the surface of the gauges. Direct measurements were simultaneously taken of both the time-resolved heat flux and surface temperature on the blade. The heat flux input was used to predict a surface temperature response using a one-dimensional, semi-infinite conduction model into a substrate with known thermal properties. The sensitivities of the gauges were determined by correlating the semi-infinite predicted temperature response to the measured temperature response. A finite-difference code was used to model the penetration of the heat flux into the substrate in order to estimate the time for which the semi-infinite assumption was valid. The results from these tests showed that the gauges accurately record both the convection and radiation modes of heat transfer. The radiation and convection tests yielded gauge sensitivities which agreed to within ±11%.

Efficient Numerical Solution of Inverse Heat Conduction Problems

1995 ◽  
Author(s):  
Hans-Jürgen Reinhardt ◽  
Dinh Nho Hao
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Numerical Methods ◽  
Stationary Point ◽  
Forthcoming Paper ◽  
Inverse Heat Conduction ◽  
Piecewise Constant ◽  
Numerical Tests ◽  
Inverse Heat Conduction Problems ◽  
Special Case

Abstract In this contribution we propose new numerical methods for solving inverse heat conduction problems. The methods are constructed by considering the desired heat flux at the boundary as piecewise constant (in time) and then deriving an explicit expression for the solution of the equation for a stationary point of the minimizing functional. In a very special case the well-known Beck method is obtained. For the time being, numerical tests could not be included in this contribution but will be presented in a forthcoming paper.

A New Integral Equation for Heat Flux in Inverse Heat Conduction

1966 ◽  
Vol 88 (3) ◽  
pp. 327-328 ◽  
Author(s):  
L. I. Deverall ◽  
R. S. Channapragada
Keyword(s):  
Heat Flux ◽  
Integral Equation ◽  
Heat Conduction ◽  
Inverse Heat Conduction

Finite Element Formulation for Two-Dimensional Inverse Heat Conduction Analysis

1992 ◽  
Vol 114 (3) ◽  
pp. 553-557 ◽  
Author(s):  
T. R. Hsu ◽  
N. S. Sun ◽  
G. G. Chen ◽  
Z. L. Gong
Keyword(s):  
Heat Flux ◽  
Finite Element ◽  
Heat Conduction ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Element Formulation ◽  
Two Dimensional ◽  
Inverse Heat Conduction ◽  
Discrete Point ◽  
Element Algorithm

This paper presents a finite element algorithm for two-dimensional nonlinear inverse heat conduction analysis. The proposed method is capable of handling both unknown surface heat flux and unknown surface temperature of solids using temperature histories measured at a few discrete point. The proposed algorithms were used in the study of the thermofracture behavior of leaking pipelines with experimental verifications.

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