An optimization study of a porous plate to improve the flow distribution in the tube side of a shell and tube heat exchanger was performed using numerical and experimental methods. The first assumption in the design stage of multichannel heat exchangers is that there is an even flow distribution along the multi channels. However, this assumption is generally not upheld in real situations. An experimental study was first performed to confirm the effectiveness of a porous baffle in improving the flow distribution in the tube side of a shell and tube heat exchanger. The results showed that the baffle can largely decrease maldistribution. We then performed numerical optimization of the porous baffle shape. The optimized curvature of a porous plate and the distribution of circular holes in the baffle were determined using the numerical method. The optimization results showed that the area-weighted averaged absolute error of the flow rate of the optimized baffle decreased to one-third that of the proto-type baffle model. For validation of the numerical optimization, the flow field with the optimized baffle was measured. Although there were some differences between the experimental and the numerical results, the results showed that the flow distribution using the optimized model was largely improved compared with that of the proto-type porous baffle.