As a critical component in the advanced non-light water nuclear power plants with indirect power cycles, an intermediate heat exchanger (IHX) is used to transfer the heat from the primary coolant system to the secondary system. Generally, such reactors are operated at very high temperatures and pressures. Therefore, IHXs are required to be able to provide high thermal effectiveness while withstanding demanding operating pressure and temperature combinations. A suitable IHX candidate needs to possess high mechanical integrity.
One of the promising IHX candidate is Printed Circuit Heat Exchangers (PCHEs). The compact diffusion-bonded PCHEs are characterized by mini- or micro-flow channels photo-chemically etched on flat metal plates. These etched plates are stacked up and diffusion-bonded to form a monolithic block. Therefore, the mechanical integrity of PCHEs are centered on the mechanical design of these etched flow channels.
To date, there are several flow channel geometries developed for PCHEs. Straight and zigzag channels, the first two designs, can be often seen in Heatric-manufactured PCHEs in compliance with ASME codes to ensure the mechanical integrity. To improve the fluid flow and heat transfer capability and reduce the associated pressure drop, straight and zigzag channels evolve to other two variants: S-shaped fin and airfoil fin channels. However, since the surface geometry of the flow channels become significantly complicated, the ASME code is not applicable any longer. Numerical simulation is then required to analyze the mechanical strength of the evolved flow channels under extremely harsh operating conditions.
This paper provides a review on the mechanical design of PCHEs with straight and zigzag channels, which refers to the ASME Boiler and Pressure Vessel Codes. In addition, numerical simulations of the mechanical stress for a case study of S-shaped fin will be presented with Inconel 617 as the construction material. Research plans at the Ohio State University are also presented. The aim of this paper is to summarize the common mechanical design method for PCHEs as well as introduce some of the ongoing research work related to the mechanical strength analysis of complicated flow channels with the aid of computer simulation.
