Thermal_Systems_with_Simscape3e

matlab simulink 热模型

PowerPoint slides to accompany

System Dynamics, Third EditionWilliam J. Palm III

Using SimscapeTM for Modeling Thermal Systems:

Dynamics of a Quenching Process

Copyright © 2014. The McGraw-Hill Companies, Inc.

matlab simulink 热模型

These slides are intended to be used with the author’s text, System Dynamics, 3/e, published by McGraw-Hill© 2014.Acknowledgments

The author wishes to acknowledge the support of McGraw-Hill for hosting these slides, and The MathWorks, Inc., who supplied the software. Naomi Fernandes, Dr. Gerald Brusher, and Steve Miller of MathWorks provided much assistance. Dr. Brusher’s contributions formed the basis for many of the Simscape models presented here.MATLAB®, Simulink®, and Simscape are registered trademarks and trademarks of The MathWorks, Inc. and are used with permission.

The equations and math symbols in these slides were created with the new equation editor in PowerPoint 2010, and thus material containing these elements will appear as graphics when viewed in an earlier version.

matlab simulink 热模型

Simscape extends the capabilities of Simulink® by providing tools for modeling and simulation of multi-domain physical systems, such as those with mechanical, thermal, hydraulic, and electrical components. In this presentation, we will show you how to utilize Simscape to construct models of thermal processes. One such process is quenching, whose representation is shown below. We will start with a simple model, in which we assume that the bath temperature Tb remains constant. The differential equation model of this case is simple enough to be solved analytically, so we can use the solution to check our Simscape model. Then we will consider the case where Tb can vary with time.

matlab simulink 热模型

matlab simulink 热模型

matlab simulink 热模型

matlab simulink 热模型

We will discuss these blocks in more detail in the next few slides.

matlab simulink 热模型

Note that the units of the specific heat are selected as J/kg/K while the initial temperature has units of C. This is reasonable because DK = DC. Moreover, Simscape internally accounts for differences in units and makes the necessary conversions.8

matlab simulink 热模型

Thermal Reference Block: Its Block Parameters dialog box shows the definition of the block. It requires no parameters.

matlab simulink 热模型

Convective Heat Transfer Block: This models the convective resistance. Study its Block Parameters dialog box, which shows the definition of the block. It requires two parameters. Type in their symbols as shown. These represent the cube surface area A and the heat transfer coefficient h. Note the units, whose default values are the same as ours for this example. Again, we are making use of the fact that DK = DC.

matlab simulink 热模型

Ideal Temperature Source Block: Its Block Parameters dialog box shows the definition of the block. It requires no parameters.

matlab simulink 热模型

Ideal Temperature Sensor Block: Its Block Parameters dialog box shows the definition of the block. It requires no parameters.

matlab simulink 热模型

Now insert and connect the PS-Simulink Converter block, which is in the Simscape>Utilities library. Connect its input to the lowe

r output port (T) of the temperature sensor as shown below. This port provides a measurement of the bath temperature T. The B port is connected the Thermal Reference block.Data from a Simscape model can be further manipulated in Simulink. We will use Simulink to convert the temperature data to degrees C. Insert a Sum block and the Scope. The “K to degC ” block is simply a renamed Constant block from the Simulink>Sources library.

matlab simulink 热模型

The Block Parameters dialog box of the “K to degC ” block is shown below. Enter 273.15 for the value. This is the value of 0°C in degrees K. You create the name of the block as with any other block.

matlab simulink 热模型

The PS-Simulink Converter block converts the physical signal (PS) to a unit-less Simulink output signal. Its Block Parameters dialog box is shown below. Here the units were selected to be degrees K.

As an alternative to using Simulink to convert the temperature from Kelvin to Celsius, we could have also used this checkbox and then selected Celsius for units.

matlab simulink 热模型

Next select and place the Simulink-PS Converter block from the Simscape>Utilities library and the “DegC to K” block. This is simply a renamed Constant block from the Simulink>Sources library.