Using Linear Superposition to Solve Multiple Heat Source Transient Thermal Problems

For many years engineers have been using linear superposition to solve steady state thermal problems with multiple-heat-source systems. Predicting transient response of single-heat-source systems has been performed using R-C Foster networks with reasonable success. In most real applications there are multiple heat sources that are interacting perhaps in very complex ways in the time domain. Being able to simulate these interactions using a spreadsheet tool or a circuit simulator may be very advantageous to a device or application engineer designing or evaluating an application design. Using an RC-network model of a system to represent the individual transient response curves, we’ll show how to do this bookkeeping (and all the other calculations) for a simple system using Microsoft Excel. We’ll also see how to set up this sort of problem in a circuit simulator.