scholarly journals Optimization of Transient Heat Transfer Measurements Using Thermochromic Liquid Crystals Based on an Error Estimation

1996 ◽  
Author(s):  
Rainer Höcker
Keyword(s):  
Heat Transfer ◽  
Liquid Crystals ◽  
Measurement Techniques ◽  
Analytical Investigation ◽  
Transient Heat Transfer ◽  
Critical Parameters ◽  
Transfer Experiment ◽  
Transfer Measurement ◽  
Thermochromic Liquid Crystals ◽  
The Individual

An analytical investigation has been made to identify and quantify critical parameters influencing the final result of a transient heat transfer experiment. The aim was to obtain a set of dimensionless parameters, that describe the interaction of the individual measured quantities in a compact form. Among the wide variety of different kinds of heat transfer measurement techniques, the transient method, employing thermochromic liquid crystals, is very useful. It gives much detailed heat transfer information with a minimum effort in experimental time. The present paper focuses on this technique, although it is not the only choice for all kinds of applications, but it is the currently most frequently used one. This paper provides the means to lay out an experiment, so that it yields acceptable results with respect to the constraints for a set of test boundary conditions.

Developments in Instrumentation and Processing for Transient Heat Transfer Measurement in a Full-Stage Model Turbine

1989 ◽  
Vol 111 (1) ◽  
pp. 20-27 ◽  
Author(s):  
R. W. Ainsworth ◽  
J. L. Allen ◽  
M. R. D. Davies ◽  
J. E. Doorly ◽  
C. J. P. Forth ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Transient Heat Transfer ◽  
Stage Model ◽  
Two Dimensional ◽  
Turbine Stage ◽  
Transfer Measurement ◽  
Unsteady Effects ◽  
Heat Transfer Measurement

Transient heat transfer measurement techniques have long been used in two-dimensional stationary cascade tests designed to model turbine conditions used in Oxford. More recently, experiments studying some of the unsteady effects have been carried out using a rotating wake generator upstream of the rotor cascade. Currently work has concentrated on providing a fully three-dimensional rotating turbine stage. In an associated paper, the modifications necessary to accommodate this stage in the Oxford Isentropic Light Piston Tunnel are discussed. In this paper the developments necessary to permit the measurement of transient heat transfer under these rotating conditions are fully described.

A Hybrid Transient Step-Heating Heat Transfer Measurement Technique Using Heater Foils and Liquid-Crystal Thermography

1993 ◽  
Vol 115 (2) ◽  
pp. 319-324 ◽  
Author(s):  
J. von Wolfersdorf ◽  
R. Hoecker ◽  
T. Sattelmayer
Keyword(s):  
Heat Transfer ◽  
Liquid Crystals ◽  
Local Heat ◽  
Boundary Layer Flows ◽  
Liquid Crystal Thermography ◽  
Step Heating ◽  
Transfer Measurement ◽  
Local Heat Flux ◽  
Heating Pattern ◽  
The Heat Transfer Coefficient

A transient heat transfer technique using a heating foil and liquid crystals is described. The basic idea is a step-heating technique, eliminating the local heat flux and the surface temperature during the data reduction. Nonuniformities in the heating pattern are allowed and calibration of the liquid crystals is no longer necessary. They are used as an indicator of an isotherm only. The heat transfer coefficient is deduced from two time measurements. The laminar and turbulent boundary layer flows over a flat plate were tested to verify the applicability and accuracy of the method.

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