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Method for determining air side convective heat transfer coefficient using infrared thermography.

Number: pap. 2587

Author(s) : WUJEK S. S., STAATS W. L., ELBEL S., et al.

Summary

Air side convective heat transfer coefficients are among the most important parameters to know when modeling thermal systems due to their dominant impact on the overall heat transfer coefficient. Local air side convective heat transfer coefficients can often prove challenging to measure experimentally due to limitations with sensor accuracy, complexity of surface geometries, and changes to the heat transfer due to the installation of the sensor itself. Infrared thermography allows local heat transfer coefficients to be accurately determined for many different surface geometries in a non-intrusive manner which does not impact the results. Moreover, when determining convective heat transfer coefficients for a large number of samples, it is less costly in terms of both time and materials than other experimental methods. Using infrared thermography, we report a method that determines the heat transfer coefficient for an arbitrary region by determining the rate at which the surface temperature changes due to a step change in air temperature. To utilize the method a simple calibration is first done to determine the local thermal time constant under natural convection. Alternatively, if the thermal properties of the object are well known, a model may be used. In subsequent tests, the ratio of thermal time constant to that from the calibration test can be determined. As the material properties of the solid object are unchanged, the convective heat transfer coefficient scales nearly inversely with the thermal time constant. A computer script was created which automates the entire analysis process with the exception of determining the region of interest. Using this method, real-time heat transfer coefficient measurements of were performed rotating fan blade.

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Pages: 10 p.

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Details

  • Original title: Method for determining air side convective heat transfer coefficient using infrared thermography.
  • Record ID : 30018750
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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