Session: 13-01 - Heat Exchangers

Paper Number: 128871

128871 - An Experimental Case Study in Combining Topology Optimization and Additive Manufacturing Techniques to Generate Novel and High-Performance Compact Heat Exchanger Designs 

Two-fluid heat exchangers are widely used in turbomachinery for several purposes. Traditional designs include shell-and-tube, gasket plate, and plate-and-fin style designs. More recently, the industrialization of additive manufacturing processes has led to interest in alternative, more complex heat exchanger designs, such as those constructed from repeating triply periodic unit cell geometries like gyroids or Schwartz minimal surfaces. These types of heat exchanger designs are particularly convenient because their performance can be scaled up or down by including more or fewer periodic unit cells in the final heat exchanger lattice. Despite their complexity, repeating periodic unit cell-based heat exchanger designs have rarely shown performance advantages over more traditional designs and therefore have yet find widespread industrial application.

One promising design technique to improve the performance of periodic unit cell-based heat exchanger designs is topology optimization, a mathematical technique which uses a physics-driven design optimization loop to generate optimal geometries for a given objective function and flow condition. Additive manufacturing in combination with topology optimization enables immense opportunities in overcoming the challenges associated with conventional thermal management device designs.

This paper presents the results of project to design, build, and test a two-fluid heat exchanger based on a periodic unit cell design using topology optimization and additive manufacturing. The heat exchanger working fluids are nitrogen (hot side) and air (cold side), and it is arranged in a cross-flow design. A proprietary topology optimization algorithm was used to generate the unit cell which was replicated in a 20x20x20 matrix of unit cells. Analysis of the design of the unit cells showed that they generated secondary flows to increase the effectiveness of the heat transfer while also minimizing unnecessary loss-generating flow structures. The performance of the heat exchanger was simulated computationally using a combination of RANS-based CFD simulations on a single unit cell, the results of which were used to build a reduced-order model to predict the heat transfer and pressure drop across the entire heat exchanger at two operating conditions.

The final heat exchanger design was built using a RenAM 500Q machine in stainless steel (Figure 1). Two identical geometries were built to ensure repeatability can be assessed. The heat exchanger was experimentally tested at a range of operating conditions, with each measurement being repeated three times. The experimental results are compared against the numerical predictions for heat exchanger effectiveness, and j-f factors on both the hot and cold sides.

Presenting Author: Thomas Rees ToffeeAM Ltd

Presenting Author Biography: Thomas is an aerospace engineer specialized in fluid dynamics, particularly compressible flosws, heat transfer, and optimization. He holds an M.Eng in Aeronautical Engineering, an M.Res in Fluid Dynamics, and a PhD in hypersonic aerodynamics and heat transfer, all from Imperial College London. He was one of ToffeeAM's first employees and was appointed Tech lead in 2022. He has previously worked at Rolls-Royce, the Von Karman Institute for Fluid Dynamics, Fluid Gravity Engineering, and the European Space Agency.

Authors:

Thomas Rees ToffeeAM Ltd
Abdullah Azam Boeing
Nicola Casari ToffeeAM
Polly Banks Boeing
Lukas Jiranek Boeing
Stefano Furino ToffeeAM Ltd
Arun Muley Boeing