This book investigated the effect of twisted tubes on the thermal performance of the shell and tube heat exchanger. The computational fluid dynamics (CFD) with different turbulence models (realizable k-ε and standard k-ε) was employed to analyze. The results were compared with the published study to verify the present solution. In this book, mass flow rates ranging from 0.5 kg/s to 2 kg/s were considered to investigate thermal performance. The results demonstrated changing the pitch from 180 mm to 135, 90, 67.5, and 45 mm increases the heat transfer coefficient to 7%, 13%, 25%, and 37%, respectively. Comparing the smooth tube with other cases shows that using the twisted tube (P=45 mm) increases the pressure drop by 25% and enhances the heat transfer coefficient by 57%.