Numerically investigated effects of different Dean number and pitch size on flow and heat transfer characteristics in a helically coil-tube heat exchanger

A helically coil-tube heat exchanger is generally applied in industry applications due to its compact structure, larger heat transfer area and higher heat transfer capability, etc. However, flow and heat transfer phenomena related to this kind of heat exchanger are so sophisticated. A computational fluid dynamics (CFD) methodology is proposed in this paper to investigate effects of different Dean (De) number and pitch size on the thermal–hydraulic characteristics in a helically coil-tube heat exchanger. Three values of De number and four sizes of pitch are considered herein. Based on the simulation results, the complicated phenomena occurred within a helically coiled-tube heat exchanger can be reasonably captured, including the flow acceleration and separation in the shell side, the turbulent wake around the rear of a coiled tube, the secondary flow within the tube, and the developing flow and heat transfer behaviors from the entrance region, etc. Existing experimental data of friction factor and Nusselt (Nu) number versus Re number (or De number) have been used to validate the present CFD model. According to the comparison results, the present predicted trends correspond with the experimental measurements both qualitatively and quantitatively.