Thermal Stresses in U-Tubes Versus Bend Radius and Baffle Spacings

Abstract

Analytical and explicit formulas are developed to give maximum rotation, bending moment and stress in heat exchanger U-tubes due to the difference between thermal expansions of hot leg and cold leg. The formula for maximum axial plus bending stress is given in the form of an ordinary uniaxial thermal stress multiplied by a factor f which is a function of geometric details of the tube. These formulas are intended for designers to quickly check secondary stresses in heat exchanger U-tubes and to study a possibility of improving the lifetime of small bends against Stress Corrosion Cracking by minimizing the stress in function of design details of U-tubes.