本文透過三維的晶格波茲曼中的D_3 Q_15方法來模擬異形套管的流場現象與熱流混合效率問題。在固定入出口面積與雷諾數下，透過更改內橢圓管長短軸比例與節距大小討論內外管流場現象與不同節距長短討論其熱交換能力。依照不可壓縮流體的假設，選定適當的長短軸與節距來做比較，以確保流場與熱場為可收斂之場域。
根據研究結果顯示，將內管形狀改變成扭曲橢圓管時，增加異形管長短軸比值或縮短節距長短時，都將增加其二次流強度，但是同時也將增加管內的壓降，因此將增加流場為克服阻力所做的工。本文透過不同的幾何探討二次流增強的強度與摩擦因子增加的現象，提供未來設計熱交換套管的基礎。

In this thesis, D3Q15 model of the Lattice Boltzmann method has been used to simulate the flow field and heat transfer efficiency of double pipe with twisted oval tube. This thesis was discussed with constant inlet, outlet velocity and cross section area by adjusting the ratio between major axis and minor axis. The proper ratio was chosen in order to make sure the fluid field was convergent based on non-compressible hypothesis.
The intensity of secondary flow and the amount of heat transfer were increased with increasing the ratio between major axis and minor axis and with decreasing the pitch. On contrast, It caused more pressure drop. In this way, The system required much more work to overcome the air resistance. In the thesis, it focused on the relationship between secondary flow and Darcy friction factor to be the foundation of double pipe heat exchanger design

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