The paper is in Persian.
Nazari, M.R., and Alemrajabi A. A., Mechanical and Aerospace Engineering Journal, Vol. 4, No. 2, pp. 1-14, 2008

ABSTRACT
In this work, Heat transfer and pressure drop for a three-dimensional flow in the enterance region of a pipe, which is equipped with one or more inserts, is numerically investigated. The inserts were inter-connected by a thin rod and were kept in the center of the pipe. The Reynolds number for the flow ranged between 450 to 1800 and the Prandtl number was 0.72. The number of inserts, the distance between them, and their axial length were the variables whose effects on the heat transfer and on the pressure drop were investigated. Finite volume method was employed to transfer the govening equations into algebraic ones. To evalutae simultaneous effects of the inserts on heat transfer and on pressure drop, an overall enhanncement ratio (OER) was introduced and applied. The results show that in many cases, thinner insserts lead to a better OER’s. Also, in lamiar flows, the shape of the inserts affects ORE. On the other hand, inserts with an square shape lead to logitudinal vortices, which increase ORE.