Two models are presented in this Model of the Month—a steady state and a transient model. Both use the same Jeep Geometry developed from photos of a 97 Jeep Grand Cherokee (Trademarks of DaimlerChrysler). The model was developed with 37 total parts, including 9 fluid parts (coolant heat source to the radiator, advective air nodes underhood, etc.).
Each part has unique geometry, materials, surfaces, and convective boundary conditions. Some parts are assigned-temperature heat sources—like the engine block—while others are floating-temperature heat sources. The light bulb has 60W (assumed, not measured) of imposed heat upon it, and the bulb temperature is determined from the governing equations. Each is a heat source of a different type. RadTherm also allows negative heat sources: a negative heat load would be an energy drain from the system, such as the electrical power drained from a solar cell.
The steady state model would be used to locate hotspots or areas which could overheat due to combined electrical heat loads with solar loading (including solar greenhouse effects through the lens). The transient model simulates the lights turning on during a cold morning startup and heating the surrounding surfaces via radiation, conduction, and convection.
The heat sources in both models are the light bulbs, the engine, radiator, and solar loads. Depending on the part temperatures, the ambient air would be cooling or heating various elements.
Both models use RadTherm's "Natural Environment" setting for ultimate model boundaries. The model was constructed with numerous parts, each having assigned elements, materials, thicknesses, surface conditions, and convection links to fluid parts for advection effects.
Both models were run using the same weather file from a typical July day in the Midwestern US, but at different times of day.
To explore the model in detail, you can download it and open it in the demo version of RadTherm, which is also available for free download.
