Mahmood Reza Rahimi - Chemical engineering department, School of engineering, Yasouj University, Yasouj ۷۵۹۱۸-۷۴۸۳۱, Iran
Aboalfazl Askari
Mehdi Ghanbari

Helical coil heat exchangers are widely used in industrial applications such as, nuclear industries, power plants and heat recovery systems, etc. In many cases the working fluid that is flowing through helical coil, is two phase flow. Heat transfer to flow of air–water mixture through a helical pipe, at constant pipe wall temperature, is analyzed with a computational fluid dynamic model of two-phase flows. The bubble size distribution and coalescence and breakage of bubble groups handled through the population balance model (PBM). The obtained result for pressure drop is in good agreement with experimental results. It was found that, in comparison to the flow in a straight pipe, where high velocity region is observed at the centre of the pipe, centrifugal forces leads to high velocity region at the outer side of the pipe walls. Air volume fraction distribution obtained in this study, was shown that centrifugal forces leads to the higher concentration region of water lies at the outer side of the pipe walls.

Helical Pipes; Air–water Two Phase Flow ;Population Balance Equation; MUSIG model