Question

A tank contains liquid nitrogen at -190℃ is suspended in a vacuum shell by three stainless steel rods 0.80 cm in diameter and 3 meters long with a thermal conductivity of 16.3 W/m^2-℃. If the ambient air outside the vacuum shell is 15℃, calculate the magnitude of the conductive heat flow in watts along the support rods. A. 0.168 B. 0.0587 C. 0.182 D. 0.176

Answer 1

Answer:

C) 0.182 W

Explanation:

The effective conductive section is:

$3 * A = 3 * \frac{\pi * d^2}{4} = 3 * \frac{\pi * (0.008 m)^2}{4} = 1.5e-4 m^2$

The thermal conductivity of stainless steel is

k = 18 w/(m * K)

Heat conduction in a rod follows this equation:

$q = k * A * \frac{(t2 - t1)}{l} = 18 * 1.5e-4 * \frac{(15 - (-190))}{3} = 0.182 W$