Linear Transient Heat Transfer Analysis

Overview of Process

A transient heat transfer analysis is used to determine the temperature distribution throughout time. The same heat loads described for steady state analysis can be applied to a transient heat transfer analysis. Those loads are convection, internal heat generation, applied nodal temperature, heat flux, and radiation. These loads can be constant throughout the transient analysis or change as a function of time.

Specific heat constant and density are required

For a transient analysis, the specific heat (c _p ) and density (ρ) are required parameters. The specific heat is a measure of the variation of stored energy with temperature. The rate of energy decrease in an element is

-Volume ρ c _p dT/dt

where dT/dt is the change in temperature versus time.

Because the density entered is a mass density in units of mass, the specific heat must be in the same units of mass. The part properties control the values for specific heat and mass density and entered in the Material Specification screen. For example,

Mass Density	Specific Heat
(lbf · s2 / in) / in3	BTU / [ (lb · s2 / in) °F ]
kg/m3	J/(kg °C)
lbm/ft3	BTU/(lbm °F)
g/cm3	J/(g °C)

Tip: When using Model Units, the units of mass density must be dimensionally consistent with the units of force, length, and time. This can lead to the abnormal units of mass such as lb s ² /in. To avoid such behavior, use a Display Unit which allows the mass to be independent of the force, length, and time units. See the page General Options: Unit Systems: Selecting a Units System for details.

Plotting Temperature versus Time

The results of a node can be reviewed throughout the duration of the analysis by selecting the node, right-clicking, and selecting the Graph Result(s) command. A graph displays plotting the selected result for the selected nodes. Refer to Results section for information on actions that can be performed on the graph.