This paper presents a numerical analysis of laminar periodic flow and heat transfer in a rectangular constant temperature-surfaced channel with triangular wavy baffles (TWBs).The TWBs were mounted on the opposite walls of the rectangular channel with inline arrangements.The TWBs are placed on the upper and lower walls with attack angle 45?.The numerical is performed with three dif-ferent baffle height ratios (BR=b/H=0.05 0.3) at constant pitch ratio (PR) of 1.0 for the range 100 ≤ Re ≤ 1000.The computational results are shown in the topology of flow and heat transfer.It is found that the heat transfer in the channel with the TWB is more effective than that without baffle.The in-crease in the blockage ratio,BR leads to a considerable increase in the Nusselt number and friction factor.The results indicate that at low BR,a fluid flow is significantly disturbed resulting in inefficient heat transfer.As BR increases,both heat transfer rate in terms of Nusselt number and pressure drop in terms of friction factor increase.Over the range examined,the maximum Nu/Nu0 of 7.3 and f/f0 of 126 are both found with the use of the baffles with BR=0.30 at Re=1000.In addition,the flow structure and temperature field in the channel with TWBs are also reported. This paper presents a numerical analysis of laminar periodic flow and heat transfer in a rectangular constant temperature-surfaced channel with triangular wavy baffles (TWBs). The TWBs were mounted on the opposite walls of the rectangular channel with inline arrangements. TWBs are placed on the upper and lower walls with attack angle 45?. The numerical is performed with three dif-ferent baffle height ratios (BR = b / H = 0.05 0.3) at constant pitch ratio (PR) of 1.0 for the range 100 ≤ Re ≤ 1000 . The computational results are shown in the topology of flow and heat transfer. It was found that the heat transfer in the channel with the TWB is more effective than that without baffle. In-crease in the blockage ratio, BR leads to a blockage ratio increase in the Nusselt number and friction factor. The results indicate that at low BR, a fluid flow is significantly disturbed resulting in inefficient heat transfer. AS BR increases, both heat transfer rate in terms of Nusselt number and pressure drop in terms of friction factor increase. Over the range examined, the maximum Nu / Nu0 of 7.3 and f / f0 of 126 are both found with the use of the baffles with BR = 0.30 at Re = 1000. In addition, the flow structure and temperature field in the channel with TWBs are also reported.