Design optimization of a high-temperature fin-and-tube heat exchanger manifold - A case study

摘要

High-temperature fin-and-tube heat exchangers are widely used in many industries such as petrochemical industry, automotive, energy, and many others. The major advantage of those heat exchanger is a large heat transfer area within a compact shape. However, it is necessary to ensure uniform distribution of velocity in all the tubes. Failing that, it leads to large differences in mean temperature in the tubes. Consequently, excessive thermal stress occurs, that may cause the heat exchanger to break down. The small volume of collectors of the heat exchangers implicates possibility of improper flow condition inside the tubes, causing an unsuitable inner distribution of thermal and mechanical loads. This case study presents a design optimization of high temperature fin and tube heat exchanger manifold. The modified design of heat exchanger manifold is proposed. To optimize the manifold shape, the Particle Swarm Optimization and Continuous Genetic Algorithms are used. The design consists of tube used for a typical manifold, welded to the wedge, that enlarges the volume of the fluid and improves the flow distribution to tubular space of heat exchanger. The ANSYS CFX based CFD simulations are performed in order to determine the flow distribution in the tubes of fin-and-tube heat exchanger. The structural analysis is performed with ANSYS to determine the occurring thermal stresses. The new design of heat exchanger manifolds allowed one to reduce the tube wall temperature from 185 °C to 134 °C and compressible stresses in the construction of heat exchanger by nearly five times (from 105 MPa to 23 MPa), compared to the traditional fin-and-tube heat exchanger manifold.