Detailed design of shell-and-tube heat exchangers using CFD

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Tezin Türü: Yüksek Lisans

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

Tezin Onay Tarihi: 2007

Öğrenci: ENDER ÖZDEN

Danışman: İLKER TARI

Özet:

Traditionally Shell-and-tube heat exchangers are designed using correlation based approaches like Kern method and Bell-Delaware method. With the advances in Computational Fluid Dynamics (CFD) software, it is now possible to design small heat exchangers using CFD. In this thesis, shell-and-tube heat exchangers are modeled and numerically analyzed using a commercial finite volume package. The modeled heat exchangers are relatively small, have single shell and tube passes. The leakage effects are not taken into account in the design process. Therefore, there is no leakage from baffle orifices and no gap between baffles and the shell. This study is focused on shell side flow phenomena. First, only shell side is modeled and shell side heat transfer and flow characteristics are analyzed with a series of CFD simulations. Various turbulence models are tried for the first and second order discretization schemes using different mesh densities. CFD predictions of the shell side pressure drop and the heat transfer coefficient are obtained and compared with correlation based method results. After selecting the best modeling approach, the sensitivity of the results to the flow rate, the baffle spacing and baffle cut height are investigated. Then, a simple double pipe heat exchanger is modeled. For the double pipe heat exchanger, both the shell (annulus) side and the tube side are modeled. Last, analyses are performed for a full shell-and-tube heat exchanger model. For that last model, a small laminar educational heat exchanger setup is used. The results are compared with the available experimental results obtained from the setup. Overall, it is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. The correlation based approaches may indicate the existence of a weakness in design, but CFD simulations can also pin point the source and the location of the weakness.