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Active thermal isolation for temperature responsive sensorsThe detection of flow transition between laminar and turbulent flow and of shear stress or skin friction of airfoils is important in basic research for validation of airfoil theory and design. These values are conventionally measured using hot film nickel sensors deposited on a polyimide substrate. The substrate electrically insulates the sensor and underlying airfoil but is prevented from thermally isolating the sensor by thickness constraints necessary to avoid flow contamination. Proposed heating of the model surface is difficult to control, requires significant energy expenditures, and may alter the basic flow state of the airfoil. A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specific surface of the body. The total thickness of the isolator and sensor avoid any contamination of the flow. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes (1) operating the isolator at the same temperature as the constant temperature of the sensor; and (2) establishing a fixed boundary temperature which is either less than or equal to, or slightly greater than the sensor constant temperature. The present invention accordingly thermally isolates a temperature responsive sensor in an energy efficient, controllable manner while avoiding any contamination of the flow.
Document ID
19940030568
Acquisition Source
Legacy CDMS
Document Type
Other - Patent
Authors
Martinson, Scott D. (NASA Langley Research Center Hampton, VA, United States)
Gray, David L. (NASA Langley Research Center Hampton, VA, United States)
Carraway, Debra L. (NASA Langley Research Center Hampton, VA, United States)
Reda, Daniel C. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
May 17, 1994
Subject Category
Fluid Mechanics And Heat Transfer
Accession Number
94N35074
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Patent
US-PATENT-5,311,772|NASA-CASE-LAR-14612-1
Patent Application
US-PATENT-APPL-SN-820431

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