Modelling Novel Heat Exchangers for Aircraft Thermal Management

This thesis focuses on proposing a novel heat management solution which could be applied in the next generation aircraft. The need for novel solutions in this sector arises primarily from the severe installation constrains and the increased use of electronics which in turn creates the need for more efficient cooling. The research is accomplished by focusing on numerical modelling of heat exchanger performance using computational fluid dynamics. In Chapters 1-3 an overview of the topics relating to the project is provided. It was particularly focused on current heat exchangers used in industry and the recent advancements within the aircraft thermal management systems driving this project.Various additive layer manufacturing techniques are compared and the most suitable one for heat exchangers is identified. In addition, current analytical/empirical design methodology of heat exchangers is compared to existing numerical modelling work. In Chapter 4 a two dimensional sinusoidal heat exchanger channel geometry was taken from a published numerical study. It was used to assess the impact of various numerical modelling assumptions at the highest computational resolution feasible. It was found that for the flows occurring in the transitional Reynolds number regime a particular care needs to be taken in numerical solution setup to predict flow and heat transfer accurately which is often not demonstrated in the literature. In Chapter 5 a plate-fin heat exchanger with serrated corrugation was experimentally and numerically evaluated allowing to build a robust numerical modelling framework for heat exchangers. During the process a novel approach to model heat exchanger corrugation was proposed. It uses a slice of a heat exchanger core and models both hot and cold fluid streams separated by a solid. It enables simulating the cross-flow heat transfer effects directly and eliminates the need for analytical/empirical models still popular within industry. The data from this novel corrugation model was then used in the heat exchanger unit model and produced a better agreement with the experimental data than normally obtained in industry. In Chapter 6 the research focused on applying additive layer manufacturing to heat exchangers. A series of novel heat transfer ideas were designed and manufactured of titanium using selective layer melting. The most promising inter-layer heat exchanger corrugation was incorporated in a novel proof of concept heat exchanger design with manifold headers. It was then evaluated numerically and compared to a more conventional pin-fin heat exchanger. Overall, the novel heat exchanger design led to increased heat transfer with no penalty in flow resistance compared to the pin-fin heat exchanger. This novel design, whilst is a proof of concept heat exchanger, is a significant step in industry and opens the way for the next generation more efficient heat transfer solutions.