Ground-Water Loops
The software allows for a ground-water loop to be used in association with a heat pump. Here temperature is calculated depending on depth. The following assumptions were made in this respect:
Soil temperature θ(x,t) depending on depth x (into the soil) and time t varies under the influence of the seasonal course of the outdoor temperature according to the following formula:
\(\theta(x,t) = \ \theta_{m} – \ \theta_{0} \cdot exp\left( – x\sqrt{\frac{\pi}{a \cdot T}} \right) \cdot cos\left( \frac{2\pi}{T}t – x \cdot \sqrt{\frac{\pi}{a \cdot T}} \right)\)
With a ground water depth of about 10-15 m and deeper it can be assumed with good accuracy that the ground water temperature remains constant over the year and matches the average annual outdoor temperature.
Static Pressure
Polysun enables users to correctly calculate both static and dynamic pressure. To correctly calculate the required height difference ∆H a distinction should be made whether or not the loop return line is immersed in the return water tank. A negative difference is also possible; this will result in the pump being relieved of pressure. The image below illustrates this correlation:
