This model demonstrates the use of scripts in RadTherm/MuSESPro Version 7.1 to simulate simple thermostatic control of two heating systems. The steps to develop and implement this model are shown below. This model represents a common heated plate system used in many manufacturing operations. Heated plates are used to cure adhesives or control chemical reaction rates. This example plate has some recessed areas where parts would be held and heated by direct conduction during the manufacturing process.
We began our workflow by examining our geometry in a CAD package. Our software handles objects somewhat differently than traditional solid modeling codes. We are translating a 3D surface into a 2D representation with thickness defined in the GUI. This allows you to vary the thickness (including layered thicknesses) in the GUI without returning to CAD to modify the geometry.
The views to the left are ghosted, solid, and wireframe, with the resulting mesh created at the bottom. Only the top surface was meshed. The mesh was divided into parts where thickness varied or where heaters were located.
Model Setup
We imported the parted-out mesh geometry into RadTherm for thermal analysis. The goal was to control the temperature at two different points on the geometry, producing approximately 255ºC in one location and 240ºC in another zone of the heat plate.
Script Editor
RadTherm 7.1 utilizes the "QT Script" scripting language (based on Javascript) to perform hook functions (gathering data from the simulation) and to execute user-defined routines. In this case, scripts check the temperature of two different elements in the model, and independently turn heaters on/off relative to a set point and max delta above/below the setpoint. Version 7.1 includes a complete script editor; see screenshot below.
In addition to the script, which is generic, the user inputs a simple text string to assign the thermostatic element number, the set point temperature, delta temperature, and imposed wattage for ON and OFF conditions. The user string for each of the two heater scripts are printed below.
T-Stat A
(TA=240),(dTA=1.5),(sensorElemA=649),(powerOnA=2000),(powerOffA=0)
T-Stat B
(TB=255),(dTB=1.5),(sensorElemB=550),(powerOnB=600),(powerOffB=0)
This text is input in the Hook Functions dialog box.
The script also includes some run-time output to the console window, showing the current status of each heater, the temperature of the thermostatic elements, and whether or not the heater status is being changed on/off. Below is a screenshot of the console window. Data can also be written out to text files.
The heaters are considered to be embedded within the aluminum plate. To implement the heaters, we imposed the energy on the internal nodes of 3-layer parts in RadTherm. Since the heater is considered to be the middle layer, we impose the wattage on both sides. Since the power is imposed in two places (both interior thermal nodes), our script imposes only half the actual wattage on each. The wattage is defined in the user string read by the routine. Simply editing the user string allows the user to change the power levels and reanalyze the system. Alternately, the power could read from a text file and several runs processed in batch mode for optimization studies.
Thermal Results
Below is a plot of the thermal results from RadTherm 7.1b—the temperatures of the thermostatic elements. Overshoot is due in part to the use of 30-second timesteps in the simulation. The thermostatic elements are checked at the end of each 30-second time step and the heater switched on/off as needed.
Choosing Elements
The elements chosen for the thermostatic controls are shown below and based on key temperature locations for manufacturing this part.
To determine an element's number, right click ON the element (even if a different element is already selected) and choose Properties>Element. See screenshot below for an example.
Transient Results
Click on the images below to view animated GIFs of the simulation in two different temperature scales. Note that each GIF is about 3 MB.
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