The response surface methodology (RSM) is firstly employed to investigate the geometric and flow parameters on heat transfer, pressure drop and thermal performance of sinusoidal wavy channels with different phase shifts. The investigated flow and geometric parameters are axial Reynolds number 1106<Rea<2530, wave's amplitude ratio 0.2<b/H<0.6, phase shift 0∘<φ<180∘ and number of waves 5<Nw<15, respectively. The experiments are carried out by using face central composite design (FCCD). The geometric parameters are optimized and general correlations for pressure drop and Nusselt number inside sinusoidal channels are presented. The influence of each parameter on the heat transfer and pressure drop of sinusoidal wavy channel is also investigated. It is found that the heat transfer to pressure drop ratio is maximum for b/H=0.54, Nw=11, φ/π=0 and the corresponding value of η is 1.21. This optimization gives a lot of freedom to engineers to choose the optimal geometric parameters of plate heat exchangers.