Measurement of thermal conductivity and heat capacity of phase change materials with the longitudinal heat flow method.

Even though Differential Scanning Calorimetry (DSC) is a common method for the determination of specific heat capacity, there is also need for methods suitable for a larger specimen size in the range of several cubic centimeters instead of micro liters. For phase change materials or compounds which show specimen size dependent thermophysical caloric properties below a critical specimen volume, e.g. sub cooling effects, the larger specimen volumes are absolutely essential. The Longitudinal Heat Flow Method is a well-known steady state method to measure the thermal conductivity of medium sized solid samples. With a modification of the measurement procedure to a transient temperature step at the top and bottom end of the stack it is now possible to determine the heat capacity of a specimen in a defined temperature interval. An apparent heat flux is determined during the transient heating phase, which can be evaluated with a novel analytical model. Numerical simulations of this new measurement method are validated by experimental investigation of different materials.