In an industrial plant, air quality is normally improved before being fed into a building and a heat exchanger is one of the usual devices employed to achieve such air improvement. Therefore, enhancement of heat exchanger thermal performance as well as its operating cost is always required. A heat exchanger is a mechanical device usually consists of a main duct for transferring working fluid while there are tabulators embedded inside. The tabulators will create turbulent flow in the duct, which usually enhances convection heat transfer. It can generate by obstructions in channel of the fluid flow. This technique is known as periodic flow interruption. This paper presents the design of tabulators by using computational fluid dynamics (CFD). The case study of laminar periodic flow and heat transfer in a square duct with isothermal walls and with staggered Ushape baffles is investigated numerically. The computation studies based on the finite volume method have been conducted for fluid flow for Reynolds numbers ranging from 100 to 1,200. Effect of baffle high (BR = 0.1, 0.2 & 0.3) and pitch length ratio (PR = 1, 2 & 3) on heat transfer and flow characteristics in the duct are investigated. The study shows the flow characteristics created by U-shape baffles help to increase the heat transfer rate over the test duct.