Step-wise transient method for analysis of thermal properties of materials Part 1. Theoretical considerations

Publication date: Available online 4 October 2019Source: Thermochimica ActaAuthor(s): P. Koniorczyk, J. Zmywaczyk, M. WielgoszAbstractThe authors’ approach to stepwise transient plane source method for measuring specific heat, thermal diffusivity and thermal conductivity of chosen materials: foams, polymers and metals has been presented. The dynamic temperature field is generated by the passage of the constant current through a plane electrical resistance made of thin nichrome foil in the form of disk sandwiched between two identical pieces of sample material. The sample material must completely cover the heater. A step-wise heating power is applied to this heater, resulting in a transient temperature response that is recorded by the two thermocouples mounted on the samples on the both sides of the heater. To determine thermal properties of materials it is sufficient to measure the temperature as a function of time by only one thermocouple. However, if it is possible a better way is to take the average of both signals, i.e. from the both thermocouples. From temperature response in this sandwich-sample setup configuration the thermal properties are obtained by plotting the temperature increase at the center of the sample’s surfaces along the axis symmetry of the measuring stack as a function of square root of time ΔT(t). The initial part of this plot is used to determine the thermal conductivity from the slope of the best line-fit. The second part of dependence ΔT(t) is ...

Source: Thermochimica Acta - October 5, 2019 Category: Chemistry Source Type: research