Thermal resistance for hollow cylinder is given as
(Where, Am = logarithmic mean area of cylinder,
ro, ri, L = Outer radius, inner radius and length of cylinder respectively and k = Thermal conductivity):1
\(\frac{{{r_o} - {r_i}}}{{k{A_m}}}\)
2
\(\frac{{{r_o} - {r_i}}}{k}\)
3
\(\frac{L}{{kA}}\)
4
\(\frac{{{r_o} - {r_i}}}{{4\pi k\left( {{r_o} \times {r_i}} \right)}}\)