This paper describes the second law of thermodynamics analysis of a regenerative heat exchanger. The analysis is based on the fact that the dimensionless parameters, known as the reduced periods and reduced length, are the characteristic variables to describe the heat exchanger. The solid matrix in the heat exchanger passage is discretized using trapezoidal rule and the elemental matrix is taken as a thermodynamic system. The second law of thermodynamics is applied to the system and the entropy generation equation is obtained using the dimensionless numbers Reduced period (Π) and Reduced length (Λ) in each element. In the present paper, the variation of entropy generation due to reduced length and reduced period is studied. The influence of the effectiveness of the heat exchanger on entropy generation is also highlighted.