Students searching for "Chapter 9 solutions" often misplace exponents here. The solution manual clarifies that the exponent inside the denominator is $8/27$, not $1/3$.
The fluid properties of air at 1 atm and 60°C (film temperature) are: Students searching for "Chapter 9 solutions" often misplace
$$ Nu = \frachLk = \left 0.68 + \frac0.670 Ra_L^1/4[1 + (0.492/Pr)^9/16]^4/9 \right $$ Students searching for "Chapter 9 solutions" often misplace