#TITLE_ALTERNATIVE#

• Main Author: SIHOMBING (NIM : 23100002); Pembimbing : Prof. Ir.H. Filino Harahap, Ph.D, ARNOLD
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/15030
• Institution: Institut Teknologi Bandung

DC circuit containing the vertical foil. The immediate environment for the heated foil was protected from disturbances arising from movements in the surroundings of the interferometer test section by provision of an enclosure, which was open at the top and at places where beams of light of the interferometer had to get through. Local foil surface temperature at various distances from the foil leading edge was measured with an infrared non contact thermometer, which was calibrated with type T (copper–constantan) thermocouple in the range 29 - 232 ºC. Contrary to earlier assumptions of uniform flux at the surface of an electrically heated thin foil, it was found that actual conditions at the foil surface was of a non isothermal temperature which varies according to a power law of the local distance from the leading edge. From seven tests with currents ranging from 6 to 15 A passing through the foil, only one case exhibited the uniform surface flux behavior. Interferometric fringe pattern shifts between the non heated and heated foil at a given current were measured and used to evaluate the local heat transfer coefficients at various distances from the leading edge. These coefficients were then compared to the theoretically predicted results of Sparrow and Gregg for non isothermal free convection from a vertical plate, in the form of a plot of the local Nusselt number, Nux, versus the local Grashof number, Grx, covering the range 103 < Grx < 108 for the seven tests conducted. The exponent of the non isothermal power law temperature distribution along the foil surface was evaluated by plotting the measured local excess temperature, Tw - T&#8734;, versus the local distance from the leading edge, x, and subsequently, used to plot theoretical result. The experimental results were found to be in excellent agreement with their corresponding theoretical results. It was then concluded that the differential interferometer had successfully performed as an instrument for quantitative measurements of the local free convection coefficient. The present investigation also found that surface condition on an electrically heated thin foil was of the non isothermal power law type, Tw - T&#8734; = Bxb, for which the uniform heat flux condition was a special case with the value of b equal to 0.20. The range of b covered in this experiment was from 0.147 to 0.197 From the result and experience obtained in the present work, recommendation to build in more flexibility of the interferometer were formulated so that the instrument could be used to measure local free convection coefficients of miniature fin arrays. <br /> <br /> <br /> DC circuit containing the vertical foil. The immediate environment for the heated foil was protected from disturbances arising from movements in the surroundings of the interferometer test section by provision of an enclosure, which was open at the top and at places where beams of light of the interferometer had to get through. Local foil surface temperature at various distances from the foil leading edge was measured with an infrared non contact thermometer, which was calibrated with type T (copper–constantan) thermocouple in the range 29 - 232 ºC. Contrary to earlier assumptions of uniform flux at the surface of an electrically heated thin foil, it was found that actual conditions at the foil surface was of a non isothermal temperature which varies according to a power law of the local distance from the leading edge. From seven tests with currents ranging from 6 to 15 A passing through the foil, only one case exhibited the uniform surface flux behavior. Interferometric fringe pattern shifts between the non heated and heated foil at a given current were measured and used to evaluate the local heat transfer coefficients at various distances from the leading edge. These coefficients were then compared to the theoretically predicted results of Sparrow and Gregg for non isothermal free convection from a vertical plate, in the form of a plot of the local Nusselt number, Nux, versus the local Grashof number, Grx, covering the range 103 < Grx < 108 for the seven tests conducted. The exponent of the non isothermal power law temperature distribution along the foil surface was evaluated by plotting the measured local excess temperature, Tw - T&#8734;, versus the local distance from the leading edge, x, and subsequently, used to plot theoretical result. The experimental results were found to be in excellent agreement with their corresponding theoretical results. It was then concluded that the differential interferometer had successfully performed as an instrument for quantitative measurements of the local free convection coefficient. The present investigation also found that surface condition on an electrically heated thin foil was of the non isothermal power law type, Tw - T&#8734; = Bxb, for which the uniform heat flux condition was a special case with the value of b equal to 0.20. The range of b covered in this experiment was from 0.147 to 0.197 From the result and experience obtained in the present work, recommendation to build in more flexibility of the interferometer were formulated so that the instrument could be used to measure local free convection coefficients of miniature fin arrays.