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The Kingston Hot Press presents a particularly challenging heat transfer system to model. Six 750W Omega [http://www.omega.ca/shop/pptsc.asp?ref=OT_HEATER&Nav=heac01 OT-2107] strip heaters are clamped to the two "press" plates which transfer heat and pressure to the mold and tile composite material. A cork rubber gasket provides insulation between the press plates and the steel weldments which provide the necessary structural support for the device. A simple on/off controller regulates the temperature of the center of the plate with a thermocouple transducer. Standard setpoints range between 150°C and 250°C. Since a tile (or film) can be pressed within 5-35 minutes depending on the thickness of the mold, the problem almost certainly falls within the transient time period. However, the plates are preheated to the setpoint temperature, and so a steady state model can assist in determining the ideal performance of the heating plates upon the initiation of the press cycle.
A preliminary 2D model of the plate was developed to allow for a general understanding of the behaviour of the plate which could be made accessible for the community through open office. Using a 2D finite element control volume approach , a rough estimate of the temperature distribution can be arrived at in a simple spreadsheet. Using each cell as a finite control volume the energy balance equation can be used to derive an equation for the control volume (spreadsheet cell) temperature.
The energy balance equation for a 2D control volume is given by: