Wärmeimpulse

Wärmeimpuls, or heat impulse, refers to a short-duration thermal input that delivers energy to a system, causing a rapid rise in temperature and a transient heat flow. In physics and engineering, it is often modeled as a Dirac delta function in time to study the impulse response of a material or structure. The impulse is physically generated by brief energy sources such as a laser pulse, a flash lamp, or a short electrical current pulse through a resistive element, typically applied to a surface or a thin layer.

The subsequent temperature field evolves according to the heat equation, with boundary and initial conditions determined by geometry and environment. The impulse response—how temperature or surface temperature changes over time—contains information about thermal properties such as thermal diffusivity, thermal conductivity, and specific heat. By fitting appropriate models to measured responses, these properties can be extracted. Common experimental implementations include laser flash analysis (LFA), where a short laser pulse heats one face of a sample and the rear-face temperature is monitored, and time-domain thermoreflectance (TDTR), which uses ultrafast laser pulses to generate heat and measures reflectance changes to infer thermal behavior.

Wärmeimpulses are used in nondestructive testing, calorimetry, and materials science to characterize transient heat transfer, boundary resistance, and related phenomena. Limitations include the finite duration and shape of real pulses, assumptions about material homogeneity, and boundary conditions; accuracy depends on how well the impulse approximation and the underlying thermal model reflect the actual system.