Insulated Pipe Heat Loss

Conduction through a cylindrical insulation layer: Q per metre = 2π·k·(T_fluid − T_ambient) ÷ ln(r₂ ÷ r₁), where r₁ is the pipe outside radius and r₂ = r₁ + insulation thickness. Typical k: mineral wool 0.04 W/m·K, polyurethane foam 0.025, fibreglass 0.035. Surface film resistance is ignored, so real losses are slightly lower.