Numerical Simulation of Closely Spaced Nozzle Openings for Fixed Tube sheet Heat Exchanger

Abstract

The location of nozzle openings is an important structural determinant in heat exchangers (of shell and tube type), for fixed tubesheet separation. When a nozzle is situated too near the tubesheet to shell connection, the local area will be vulnerable to large stress concentrations because of these loads conveyed by external piping systems. Such stresses may undermine the solidity and trustworthiness of the junction and the tubesheet. The study is intended to measure how the nozzle diameter size and its distance to the tubesheet junction affect the stresses that it produces to establish the nearest safe position to make the nozzles conform to the requirements of the ASME Section VIII design criteria Division 2. Finite Element Analysis (FEA) numerical simulations of different geometric models of a heat exchanger shell with a fixed tubesheet, and with nozzles of different diameters and movement off the junction were made. Depending on the scenario of the worst loading of the nozzle surface, the analyses were conducted to determine the resulting stresses within the shell and tubesheet area. Some important parameters, like the equivalent stress, deformation, and stress intensification adjacent to the junction, were also examined. The aim of this is to provide a rule of thumb for the minimum acceptable distance between the nozzle and the tubesheet junction to prevent loss of the structure at the design loads. The findings suggest that there is a critical response between the size and location of nozzles, offering information on the best design habits. This research is useful for enhancing the reliability and safety of heat exchangers, especially in those designs where the nozzle openings cannot be far apart because of space limitations.