STP789

    Effect of Mounting on the Performance of Surface Heat Flow Meters Used to Evaluate Building Heat Losses

    Published: Jan 1983


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    Abstract

    This experimental evaluation of the effect of thermal contact resistance on the measurement precision of surface mounted heat flux sensors was conducted under radiant and convective heat exchange conditions simulating an in situ measurement of heat loss through a building wall. The total thermal resistance of mounted heat flux sensors and contact/bonding agents was determined from sensor-indicated heat flows and from test-surface/sensor-face temperature differences measured with an infrared imager. Two representative makes of heat flux sensor, one rigid and one flexible, were tested at two levels of surface roughness, with five representative bonding/contacting agents. Testing was done with the test surfaces both heated by and cooling to the ambient environment.

    The contacting/bonding agents did not significantly affect the indicated heat fluxes, except when the agents failed to keep the sensor in contact with the test surface. The differences between indicated heat fluxes and calculated surface heat loss increased with increasing surface roughness. A typical 20 percent difference between measured and calculated surface heat loss was not adequately accounted for in terms of thermal resistance of sensor and bonding agent, which suggested that the sensor calibration or some other factor was in error. The flexible sensor was transparent in the visible and in the infrared, so that its indicated heat flux would be affected by attempts to match its emittance or absorptance to surrounding surfaces or to minimize convective “noise”.

    Keywords:

    heat flux, heat measurement, measuring instruments, instrument errors, building heat transfer


    Author Information:

    Wright, RE
    Aerospace Technologist, Aerospace Technologist, and Engineering Technician, NASA Langley Research Center, Hampton, Va.

    Kantsios, AG
    Aerospace Technologist, Aerospace Technologist, and Engineering Technician, NASA Langley Research Center, Hampton, Va.

    Henley, WC
    Aerospace Technologist, Aerospace Technologist, and Engineering Technician, NASA Langley Research Center, Hampton, Va.


    Paper ID: STP29453S

    Committee/Subcommittee: C16.30

    DOI: 10.1520/STP29453S


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