Optimization of air to air cross flow heat exchanger

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: İSMAİL ÇAĞATAY KOYUNCUOĞLU

Danışman: ABDULLAH ULAŞ

Özet:

An air to air cross flow heat exchanger for a jet fighter air conditioning system is optimized and analyzed in this work. Conditioned air should be supplied continuously in order to provide a safe and comfortable environment for passengers and crew. For this purpose, a small amount of highly pressurized and heated air is extracted from different stages of engine compressor, which is called ‘bleed air’. Bleed air temperature can be decreased by heat exchangers. Therefore, design of high performance, lightweight and small volume (compact) heat exchangers for aircrafts is very important. In the present study, optimum air to air cross flow heat exchangers are designed for generic supersonic aircrafts by using genetic algorithm optimization method. Firstly, parametric thermal and hydrodynamic performance formulae are created for offset-strip fin and wavy fin heat exchanger by using computational fluid dynamics (CFD). Ansys Fluent 16.0 software is used for all CFD analyses. This study allows designing unavailable fin shapes in literature for heat exchangers. Several geometrical and flow parameters such as fin height, fin spacing, wavelength, and the Reynolds number are selected for optimization. Then, multi-objective genetic algorithm is applied by choosing maximum heat transfer, minimum volume, and minimum ram air mass flow rate as three objective functions. Optimization is achieved by using Matlab commercial software. Finally, optimized design is validated by full scale CFD analysis using porous media approach instead of modelling full details of the heat exchanger in order to decrease computational effort.