Further Investigations in Tubesheet Design for a U-Tube Heat Exchanger

Abstract

A tubesheet for U-tubesheet heat exchanger is analyzed as an equivalent solid circular plate having complete isotropy in the plane of the tubesheet with usual effective elastic constants. However, the tubesheet is expected to have different values of modulus of elasticity, modulus of rigidity, and Poisson’s ratio in the thickness direction. This anisotropic behavior of the tubesheet in thickness direction is taken into account by using the anisotropic theory of plates. When performing theoretical analysis, normal stress in thickness direction is also not assumed equal to zero. Hence, the resulting expressions for deflection and bending stresses are closer to those of a thick plate. Expression for radial stress is compared with that of an isotropic thin circular plate. Based on this comparison, certain modifications in the existing code formulas are proposed. Some design aspects related to ligament efficiency, effective elastic constants, and tubesheet edge conditions are also discussed. Proposed modifications in the design procedure may lead to six to ten percent saving in the material cost.