In this study, the effects of geometrical parameters on the thermal performance of PCHE compact heat exchangers are investigated numerically. A counterflow PCHE with sinusoidal channel profile is considered in order to improve the performance of conventional straight channel PCHE. A closed-form correlation for predicting the conduction thermal resistance of the PCHE unit cell with wavy channels is developed based on an extensive set of numerical results. Then, the effectiveness of the PCHE is manipulated. The effect of waviness factor, pitch, and channel diameters are studied. The results show that the thermal performance of the PCHE can be significantly improved by employing the wavy channels. It has been shown that there is an optimal value for the waviness factor or pitch, while the thermal performance monotonically increases as the channel size increases for a fixed pressure inlet condition. This study shed light on the design and optimization of the PCHE.