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

C) 0.182 W

Step-by-step explanation:

The effective conductive section is:

`3 * A = 3 * (\pi * d^2)/(4) = 3 * (\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 * ((t2 - t1))/(l) = 18 * 1.5e-4 * ((15 - (-190)))/(3) = 0.182 W`