Heat transfer and pressure drop for a 3D flow in a pipe which is equipped with one or few inserts is numerically investigated. The Reynolds number for the flow ranges between 450 to 1800 for laminar and 3000 to 45000 for turbulent flow and the Prandtle number is 0.72. In laminar flow insert are inter-connected by a thin rod and kept in the center of the pipe. In turbulent flow inserts are connected to the wall. The number of inserts, the distance between them and their axial length are the variables and their effects on the heat transfer and pressure drop are investigated. Finite volume method is employed to transfer the govening equations into algebraic ones. To evalutae simultaneous effect of inserts on heat transfer and pressure drop, an overall enhanncement ratio (OER) is introduced and applied. The results show that in many cases, thinner ierts lead to a better OERs. Also in lamiar flow, the shape of the inserts is effective on the ORE. In turbulent flow longitudinal vortices near the wall more effects in heat transfer. Key Words: heat transfer enhancement, pressure drop, numerical method, tube inserts
