As for the pressure loss coefficient, the Nusselt correlation is provided for the laminar and turbulent region: $$\text{Nu}_{lam}=\begin{cases}3.66&\text{for constant wall temperature}\\4.364&\text{for constant wall heat flux}\end{cases}$$ $$\text{Nu}_{turb}=\frac{\left(\xi/8\right)\cdot\text{Re}\cdot\text{Pr}}{1+12.7\cdot\sqrt{\xi/8}\cdot\left(\text{Pr}^{2/3}-1\right)}\cdot\left[1+\frac{1}{3}\left(\frac{D}{l}\right)^{2/3}\right]$$ where $\displaystyle\xi=\left(1.8\log_{10}\text{Re}-1.5\right)^{-2}$
Parameter | Symbol | Unit | Description |
Length | \(l\) | m | Length of the drilling |
Count | \(N\) | none | Number of parallel drillings |