We are currently investigating the effects of ground water flow on borehole heat exchangers. As a first step we want to validate the Feflow borehole model with standard BHE models, mainly Earth Energy Designer and Finite Line SOurce. In the forum there are some questions concerning this, but I did not find answers.
For the comparsion we compare fluid temperature of the feflow model with the fluid temperatures of EED and the temperature in the borehole / ground (using the EED relation between borehole thermal resistance, borehole wall temperature and energy rate to calculate ground temperatures).
We can set up and run the feflow model using the guidance on borehole configuration (mesh points) etc. However, comparison with Earth Energy Designer for balanced or unbalanced monthly energy loads shows that the higher the energy rate, the higher the difference between the Feflow solution and EED.
Also, when running a constant energy extraction / injection we find the Feflow solution to go to a steady-state very rapidely. This is for instance the case when comparing with an FLS or EED constant energy simulation (several years) but also for a thermal response test data set (about 100 hours).
As it is important that we understand the behaviour of Feflow without natural ground water advection, we hope the forum can give us some suggestions / references how to set up and run the model.
As an example the following graphs shows the feflow and EED solution for contant heat injection:
Thank you !