Laser Processed Heat Exchangers

The considerable mass of Heat Exchangers (Hxs) and coldplates on spacecraft as well as the problematic coatings of the Condensing Heat Exchanger (CHx) are among the significant technical issues to be solved before long-duration spaceflight can occur. Specifically, high reliability CHx's and reduced mass Hxs and coldplates have been identified by the Evolvable Mars Campaign (EMC) as critical technologies needed to move beyond low earth orbit. The Laser Processed Heat Exchanger project aims to solve these problems. It will investigate the use of femtosecond laser processed surfaces to replace the harmful and problematic coatings of current CHx's and to reduce mass and volume in liquid/liquid heat exchangers. For this project, two sub-scale Hx's will be designed, manufactured, and tested. These two units consists of a high reliability CHx and a high efficiency liquid/liquid Hx. The goal of the high reliability CHx is to eliminate the dependency upon coatings and prove the feasibility in manufacturing a hydrophobic laser patterned CHx. Additionally, microbial growth testing will be conducted on the unit to assess its potential as a microbial growth mitigation strategy. The goal of the liquid/liquid Hx is to increase heat transfer by 25% compared to an identical non-treated Hx, directly translating to reduced mass and volume. To accomplish development of a high reliability CHx and decreased mass and volume Hxs, this project will be using femtosecond laser processed surfaces ("functionalized surfaces") to create a unique hydrophobic condensing surface for the CHx. A hydrophobic CHx will be designed and constructed. Testing of the CHx will take place in an airstream to validate construction methods, performance, and microbial growth resistance. Additionally, the project will be using functionalized surfaces to create increased heat transfer in a liquid/liquid Hx via increased surface area and low interfacial thermal resistance. Testing for increased heat transfer will be completed through design and development of a functionalized Hx and a typical stainless steel Hx.