Using thermal response factors with time dependent thermal properties

This paper presents a simple and fast methodology to consider changing thermal properties in, for example, the design of shallow geothermal systems, by using thermal response factors. The simulation period is split into multiple sections according to the changes in thermal properties. By transforming the temperature response from one section to the next and subsequent superposition, any changes in the thermal conductivity properties of the media through which heat travels can be taken into account. The method is verified by numerical simulation and its efficiency is demonstrated in an application example. Results show that even though the computational effort increases exponentially with the variation of thermal parameters in time, the computational time is significantly shorter than comparable numerical simulations.