For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is
A
Nu = 0.023 Re<sup>0.8</sup>.Pr<sup>0.4</sup>
B
Nu = $$\frac{\pi }{2}$$ Gz
C
Nu = $$\frac{2}{\pi }$$ Gz
D
Nu = 2 Gz<sup>0.5</sup>
Correct Answer: Nu = $$\frac{2}{\pi }$$ Gz