N15A-T019 TITLE: Additive Manufacturing Development of Efficiently Cooled Heat Exchangers

TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles, Materials/Processes

ACQUISITION PROGRAM: Applied Research Challenge Topic

OBJECTIVE: To explore and mature additive manufacturing (AM) processing via ICME (integrated computational materials (science and) engineering) methodology to develop consistent cellular heat exchangers for improved cooling effectiveness for applications in Naval ships, submarines, and aircraft. The proposed effort should also explore the science base of AM process factors that will lead to development of the evaluation criteria and methodologies to qualify (AM) components across the Naval Enterprise.

DESCRIPTION: As electronic applications multiply and new designs require higher power outputs, more efficient thermal management schemes for cooling are needed to reduce system level costs. As one example, submarines operating in warmer waters have difficulty handling heat dissipation from their electronic systems. Requirements for increased heat rejection from system electronics are wide-spread, existing across the board in Naval ship, submarine and aircraft/missile systems. With the advent of innovative additive fabrication/manufacturing methods, with which complex structures are constructed layer-by-layer, it is now possible to build cellular substrate structures in which flow channels are incorporated within the substrate. There are a number of factors that will contribute to the reliable manufacture of component via AM. Through the use of ICME, AM processes can be evaluated and modified to minimize/eliminate defects through control of process variability. It will also help determine the process window in which acceptable components can be produced by the AM process that will have similar or improved metallurgical microstructures, and physical and mechanical properties when compared to the traditionally fabricated heat exchangers. The integrity and performance of the AM-fabricated heat exchanger compared to the traditionally fabricated HX will be validated by (a) ICME methodologies, (b) mechanical and environment testing of the HX, (c) destructive examination, (d) non-destructive examination the HX, and (e) testing of the heat transfer characteristics.

The initial phases of the program should focus on the AM processing to deliver consistent, qualifiable HXs for Naval applications. In later stages of the program, if funding and time are available, the development work should include integrated models considering fluid flow (pressure drop, effects of turbulence, viscosity, etc.), heat transfer, mechanical and materials properties, as well as innovative additive manufacturing methodology for the fabrication of efficient, low cost cellular ceramic electronics substrate, with highly enhanced heat removal capability.

PHASE I: Using a generic HX CAD file supplied by ONR, employ ICME focused AM methods to replicate a current HX product design (baseline) demonstrating desired properties such as material strength, surface finish, flow integrity (i.e., devoid of defects, leaks or blockages) while maintaining component thermal efficiency with acceptable cost of manufacturing and realistic reliability factors. Laboratory scale specimens should be fabricated and characterized by mechanical testing, and destructive and non-destructive (NDE) evaluations. A framework for involving in-process NDE to improve component integrity should be planned.

PHASE II: Apply ICME tools and processes to AM methods to predict design limits needed to produce a more complex HX product with significant changes in properties such as improved heat transfer, reduced number of parts and joints, that meets the baseline HX "form, fit, and function" constraints while maintaining the physical and mechanical properties outlined in Phase I. Validation of ICME tools and predictive analysis capabilities will be analyzed by comparing the physical, metallurgical and mechanical properties of an AM heat exchanger with a current heat exchanger fabricated by traditional means to validate the production of a heat exchanger by one additive manufacturing process. Initial in-process NDE sensors with feedback control should be tested to determine the degree of AM process improvement. The non-destructive methods will be correlated with destructive examinations. The involvement of a HX original equipment manufacturer (OEM) will be strongly encouraged to participate and assist in developing the pathway for qualifying HXs and components for naval use.

PHASE III: Additive manufactured heat exchangers will be transitioned using funding provided by the Navy system program office for the system evaluated under the STTR program. The OEM involved during Phase II will be part of the transition team. Phase III will include defining the additive manufacturing parameters for qualified full scale system production and establishing facilities capable of achieving full scale production capability of Navy-qualified HXs.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Heat exchangers are universal and employed in numerous commercial systems that reject heat for engines, electronics, and other heat producing devices. The use of AM could lead to more innovative HX designs capable of more efficiently removing heat because such designs could eliminate or severely reduce joints. AM processing of components that are qualified for Navy use could also be applied to commercial use.

REFERENCES:
1. S. Baskutis, V. Vasauskas, "Mechanics and Material Aspects in Serviceability of the Heat Exchangers", Mechanika, 17 (3), pp. 239-245.

2. B.A. Cowles, D. Backman, "Advancement and Implementation of Integrated Computational Materials Engineering (ICME) for Aerospace Applications," AFRL-RX-WP-TP-21010-4151.

3. W.E. Frazier, "Metal Additive Manufacturing: A Review", Journal of Materials Engineering and Performance, v.23(6) June 2014 pp 1917-1928.

4. M. F. Horstemeyer, "Integrated Computational Materials Engineering (ICME) For Metals", John Wiley & Sons, Inc. 2012.

5. Lu, T.J., 1999, "Heat Transfer Efficiency of Metal Honeycombs", International Journal of Heat and Mass Transfer, Vol 42, No. 11, pp. 2031-2040.

KEYWORDS: Additive manufacturing; heat exchangers; qualification; reliability; thermal properties; mechanical properties; non-destructive evaluation

** TOPIC AUTHOR (TPOC) **

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