Temperature Control System Design for Flame-Sprayed Coating Based Heating Systems

  • Author / Creator
    John, Jacob Maxwell
  • A 2 cm thick American Iron and Steel Institute (AISI) 1018 steel sample was flame sprayed with Alumina (Al2O3) then a metal matrix composite consisting of Nickel-Chromium-Aluminum-Yttrium (NiCrAlY) and Alumina split 50 % by weight. A first order transfer function was derived from a lumped capacity model and was used to define parameters: time constant and gain which describe the dynamics of the heating system. Step inputs of 3, 6, and 9 V were applied to the heating element under internal forced convection heating conditions at an air temperature controlled to 15 ◦C. Temperature measurements were used to determine time constant, zero frequency gain, and confirm the Biot assumption. Heat transfer coefficient (HTC) dictating convective heat transfer rate was predicted from experimental measurements using the lumped capacity governing equation and a finite difference to describe the time derivative, values ranged from 208 W/m^(2)K and 250 W/m^(2)K. Experimental HTC was compared to theoretical HTC predictions showing a 40 % to 58 % difference. The resistance to temperature relationship for the coating material was measured using two voltage dividers in series. Results showed a maximum 2 % change in resistance over the experiment. Measured values were used in transfer function simulations to verify against experimental results, this showed that the linear model effectively predicts the non-linear system within the tested operating range. A sensitivity study shows the affect of uncertain parameters on transfer function predictions. Low uncertainty parameters are: area of the coated surface, density, thermal heat capacity, and thickness of the steel sample. High uncertainty parameters are: HTC and resistance across the flame sprayed Joule-heating element. After the transfer function was verified experimentally, it was used to design a temperature control system including a PI (Proportional integral) controller with windup control and input saturation management to provide a robust and energy efficient response.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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