Question

The Prandtl number, Npr, is a dimensionless group important in heat transfer calculations. It defined as Cuk, where C, is the heat capacity of a fluid, u is the fluid viscosity, and k is the thermal conductivity. For a particular fluid, C, = 0.583 J/(g.°C), k = 0.286 W/(m:°C), and 1936 lb./(ft·h). Estimate the value of Npr without using a calculator (remember, it is dimension less), showing your calculations; then determine it with a calculator.

Answer 1

Answer:

The Prandlt number for this fluid is 1630.

Explanation:

The Prandlt number is defined as:

$Pr=\frac{C_p\mu}{k}$

To compute the Prandlt number for this case, is best if we use the same units in every term of the formula.

$\mu=1936\frac{lb}{ft*h}*\frac{1000g}{2.205lb}*\frac{3.281ft}{1m}*\frac{1h}{3600s} \\ \\\mu=800 \frac{g}{m*s}$

Now that we have coherent units, we can calculate Pr

$Pr=\frac{C_p\mu}{k}=\frac{0.583*800}{0.286}= 1630$