A New Apparatus for Study of Stabilities in Horizontal Air Layers Heated from Below

  • B. Krstic


An apparatus has been designed and built for studies and experimental evaluation of heat transfer by simultaneous conduction, convection and radiation. It consists of a rigid enclosure with two horizontal parallel plates separated by an air gap which was heated from below. Any preselected temperature difference, of up to 100°C across the plates could be maintained at a steady state. The apparatus was operated as a conduction-radiation cell. Using an energy balance and a calibration curve, “net” radiative heat transfer was evaluated and “emittance” of plain surfaces and “apparent emittance” of surfaces with V-notches was calculated. The results obtained were compared with these measured independently on the same samples by C.S.I.R.O. using optical techniques. It was found that a maximum difference of ±0.2% exists. To ensure that conduction and radiation only were present, a method similar to that used [1] to determine the onset of convection, was applied. Results obtained for “critical pressure” and “critical Rayleigh number” were of greater accuracy then theirs, due to the use of a small thin and very sensitive heat flux sensor of low thermal capacity.


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Copyright information

© Springer Basel AG 1980

Authors and Affiliations

  • B. Krstic
    • 1
  1. 1.Royal Melbourne Institute of TechnologyAustralia

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