Numerical study of effect of geometrical parameters on void fraction distribution during flow boiling in helically coiled tubes

This study describes the effect of helical coil geometrical parameters such as coil diameter, coil pitch and tube diameter on void fraction distribution during subcooled and saturated flow boiling in a small helically coiled tube at low vapor quality region subject to constant heat flux. A proper Eulerian-based mathematical model is used for interphase exchange forces and two-phase heat transfer in modeling using bulk boiling model. The results show that an increase in helical pitch results in an increase in heating surface s wet region and an increase in the coil diameter leads to more vapor coverage in the cross section of the tube. Furthermore, increasing tube diameter leads to more vapor generation and accumulation on tube walls.

Keywords:

CFD simulation , bulk boiling method , flow boiling , void fraction , helically coiled tube