The purpose of this paper is to reach the maximum energy recovery or maximum cold stream outlet terminal temperature in a plate fin heat exchanger (PFHE) with constant volume and heat transfer area for a specified maximum pressure drop. This paper presents a methodology in surface selection and design of PFHE where full pressure drop utilization is taken as a design objective in constant heat exchanger volume and heat transfer area. Several kinds of PFHE with different fin type and geometries and different heat exchanger width, length and height could satisfy the constant volume and area condition. Setting maximum pressure drop could reduce these several heat exchangers. While the fin type and dimension of each heat exchanger is extracted due to constant volume-area and pressure drop conditions respectively, the terminal temperature of the heat exchanger would be calculated utilizing thermo-hydraulic modeling of the PFHE. A typical gas turbine regenerator is chosen as case study. The methodology is applied to this case study and results are shown. The surfaces which result maximum energy recovery are specified. In the cases that energy recovery of some surfaces would be approximately the same, other parameters such as frontal area and flow length will be considered