Heat Exchangers are critical components in various heat management systems and are used widely within a number of industries including aerospace, automotive and power generation.Compact heat exchangers are specifically designed to obtain large heat transfer surface areas per unit volume and have been developed for applications where requirements of small weight and space are mandatory. The important factors contributing to the growing need for high-temperature heat exchangers are the global trend towards more efficient power and propulsion systems that require higher operating temperatures and high-temperature thermal pollution control processes and heat recovery applications.
In high-temperature compact-type heat exchangers, materials will be exposed to very high temperatures, nearly up to 800°C, which results in metallurgical structural changes and thereby strength loss. Other factors like extent of oxidation of the material, thermal shock-bearing capability, and erosion due to suspended dirt particles also come into play. A potential material for manufacturing these heat exchangers is Ni-based superalloy. Haynes 282 alloy is one candidate that offers a balance of long-term creep strength, thermal stability, oxidation resistance, weldability, manufacturability, and repairability.
Major material joining techniques used in High-temperature compact-type heat exchangers are Diffusion bonding, Vacuum brazing and Additive manufacturing. Compact heat exchangers joined by diffusion bonding have been considered as an alternative to more conventional technologies for oil exploration platforms, advanced high-temperature reactors, concentrated solar power applications, synergetic air-breathing and rocket engines. But there is not much information in the literature on the diffusion bonding of high-temperature materials such as nickel-based superalloys. Additive manufacturing opens up new avenues for heat exchanger fabrication but there are limitations like residual stress formation, surface roughness, post-processing difficulties in complex geometries, and part qualification, which create boundaries for its application. The proposed research work is an attempt to address the challenges in diffusion bonding and additive manufacturing of high-temperature compact type heat exchangers using Nickel-based superalloy Haynes 282.