This paper presents a discretized enthalpy analysis of a FAME-MLL, NH3 plate-fin heat exchanger (PFHX) with single and two-phase flow. The paper outlines the methodology used to model the PFHX and presents a MATLAB simulation model, which uses the NIST REFPROP database for thermo-physical property evaluation. The paper presents analysis for a staged single-phase, two-phase PFHX architecture. Plots of the heat transfer coefficients, overall heat transfer coefficient, specific enthalpy and heat flux variation over the length of the PFHX are provided. The mass, volume, area, effectiveness-number of transfer units rating for each PFHX are given.