The cold flow calorimeter is an apparatus for measuring a possibly rapidly varying heat-transfer coefficient on a surface. The cold flow calorimeter includes (1) a small strain gauge bonded to a small, thin steel shim that is placed on the surface of interest and (2) a circuit that controls the electric power supplied to the strain gauge to keep the strain-gauge grid at a constant temperature [e.g., 150 °F (≈66 °C)]. The instantaneous value of the heattransfer coefficient is deduced from the instantaneous power required to maintain the constant temperature. The heat-transfer coefficient measurable by use of this apparatus can range from values characteristic of natural convection to values as large as about 1,000 Btu/(ft·h·°R) [≈1.7 kW/(m·K).

In the original application for which this apparatus was conceived, there is a need to measure heat-transfer coefficients along an O-ring surface in a nozzle joint in a solid-fuel rocket motor. In this application, there is a gas path to the sealing O ring. The cold flow calorimeter makes it possible to determine the coefficient of transfer of heat from a confined gas jet to the sealing O ring. The measurement data obtained by use of the cold flow calorimeter can be used to verify solutions from computational fluid dynamics, determine spreading factors, and increase the accuracy of predictions of the transfer of heat to an O ring to which there is a confined gas path.

This work was done by Ed Mathias and John Shipley of Thiokol Corp. for Marshall Space Flight Center. For additional information, please contact Thiokol Corp. at (435) 863-2268. MFS-31463

NASA Tech Briefs Magazine

This article first appeared in the April, 2002 issue of NASA Tech Briefs Magazine.

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