Session: 13-01 - Heat Exchangers

Paper Number: 121284

121284 - CFD Modeling of Additively Manufactured Extreme Environment Heat Exchangers for Waste Heat Recuperation 

Advanced Brayton cycle based Integrated Power & Thermal Management Systems (IPTMS) for a targeted energy efficiency of 30% and gravimetric power densities ranging from 1.6-1.9 kW/kg is an attractive proposition for thermal management of future airplane designs. One of the critical technical challenges for maturation of these technologies is the need to achieve highly compact heat exchangers capable of operation under extremely high temperatures & pressures. Further, the overall power plant sizing is strongly influenced by the heat exchanger gravimetric & volumetric power densities. The current work presents the various CFD modeling strategies developed for the design and development of additively manufactured Extreme Environment Heat Exchangers (EEHX) under the U.S Department of Energy HITEMMP program.

The present work describes the selection, sizing & rating of candidate heat transfer surfaces for the targeted power density requirements. CFD modeling of heat transfer surfaces using conjugate heat transfer methods was utilized for thermo-hydraulic performance evaluation. Experimental data from additively manufactured cold-plate style coupons was utilized to validate the CFD models to within 10% of pressure drop & heat transfer rates. Thermo-hydraulic performance data was used for sizing & rating of the heat exchanger core using INSTED software. Candidate HX core with manifold design was developed following a Design for Additive Manufacturing (DFAM) guidelines with Haynes282 material as a potential material powder for LPBF build. The current work also describes the detailed heat exchanger thermal modeling using CFD methods to evaluate its performance while mitigating potential flow-maldistribution & spanwise temperature gradients. The heat exchanger modeling strategies involving a periodic boundary-based model and end-section models to predict the thermal performance of the HX core and end-effects respectively are described in detail in the current work. With the recuperator heat exchanger designed for counter-flow configuration, the design of manifolds plays a critical role. To this end, a novel porous media based HX core modeling approach with a high-fidelity manifold model was utilized for evaluating the HX core-flow distribution.

Modeling & simulation driven targeted design improvements to the heat exchanger were implemented to achieve a power-density of 15 kW/kg under extreme environment of 800°C inlet temperature & 80 bar pressure with supercritical CO₂ working fluid. Furthermore, modeling approaches to address the significant variation of sCO2 thermo-physical properties is described in detail.  A comprehensive physical testing of heat exchanger prototypes was carried out to validate various high & low-fidelity modeling approaches. The experimentally reported pressure drop & heat transfer rates were observed to be within 15% of the model’s predictions to further validate the heat exchanger design.

Presenting Author: Vyas Duggirala Boeing Research & Technology, India

Presenting Author Biography: Vyas Duggirala joined Boeing Research & Technology-India, Integrated Vehicle Systems group as a mechanical systems design & analysis engineer in May 2019. Vyas`s expertise is in the development of numerical conjugate heat transfer-based methods and tools for thermal-fluid system design and analysis. He is actively working in the areas of CFD based methodologies for thermal-hydraulic performance characterization of novel AM enabled heat transfer surfaces, modeling and analysis of extreme environment heat exchangers and development of physics-based semi empirical correlation methods. He has collaborated extensively with BR&T teams in the US during development of these capabilities, and transitioning them to business units. Of late his research interests are towards hybrid modeling approaches for heat exchangers, AM process thermal modeling, and development of medium and high-fidelity methods and tools for two-phase heat transfer systems. Prior to Boeing, Vyas worked at Honeywell Aerospace and Indian Space Research Organization for about 7 years in the areas of Thermal management of electronics and spacecraft payloads. He received his BE in Mechanical Engineering from Osmania University, India in 2010 and M.Tech in Mechanical Engineering from Indian Institute of Technology, Bombay in 2015. Vyas is currently pursing doctorate degree from the Indian Institute of Science, Bangalore.

Authors:

Vyas Duggirala Boeing Research & Technology, India
Venkateswara Reddy Boeing Research & Technology, India
Arun Muley Boeing Research & Technology, Huntington Beach, CA
Michael Stoia Boeign Research & Technology, Huntington Beach, CA
Doug Vanaffelen Boeing Research & Technology, Huntington Beach, CA