Use of response factor method to model earth-to-air heat exchanger behaviour. Integration in a whole building simulation into SIMSPARK plat form

This paper shows the numerical model of an earth-toair heat exchanger. The system is discretized into “n” sections perpendicular to the exchanger pipe. In each section, conduction is solved using response factor method in order to reduce computational time. Each response factor is calculated using a finite element program that solves 2D conduction problems. The particularity of this problem is that time-constants are very high, making it impossible to use classical properties of response factors to reduce the number of calculations. We will set out a new approach to solve this particular problem. Heat flux entering the pipe is then expressed as a function of the temperature of the air that circulate in the pipe and the external thermal driving forces. A heat balance is then applied for each layer to find the resulting outlet air temperature. The model is then compared to an analytical model and a 3D model based on the dynamic finite volume approach. Finally an example of coupling between an earth-to-air heat exchanger and a low-consumption building is presented.