An engineering model of a gas-liquid turbulent bubbly flow in coiled tubing wound on a reel (vertical helical coils) is developed. A simplified monodispersed bubble system is considered. A largest size of a bubble was selected as a characteristic bubble size. The bubble concentration distributions across and along tubing are calculated. The concentration across tubing periodically changes along a coil. The concentration variation amplitude increases with increasing the tubing diameter and decreasing the flow rate. The model developed can be considered as a framework for a full liquid-gas turbulent flow model taking into account bubble system polydispersity. (c) 2010 Elsevier B.V. All rights reserved.