**2. Problem Statement**

This paper presents a three-dimensional (3D) steady-state CDF simulation of PFTHE under the following assumptions:


$$e\_{T\_{ll}} = \frac{\left(T\_{nl} - T\_{6,790,572}\right)}{T\_{6,790,572}}\tag{1}$$

• Relative differences (*eTw* ) between the Nusselt number for a particular fin and tube surface temperature (*NuTw* ) and Nusselt number for the reference fin and tube surface temperature: 70 ◦C (*Nu*<sup>70</sup> ◦C) as calculated according to Equation (2).

$$\mathcal{e}\_{T\_w} = \frac{\left(\mathcal{N}\mu\_{T\_w} - \mathcal{N}\mu\_{70} \circ \mathcal{C}\right)}{\mathcal{N}\mu\_{70} \circ \mathcal{C}}\tag{2}$$
