Numerical models were developed to assess the thermal performance of a HEX reactor with solid-to-gas reacting flow. Based on the experimental results obtained in part I of this study, numerical models were developed to predict the thermal performance of a plate heat exchanger-based HEX reactor involving multi-phase flow with chemical reactions. A reduced-order numerical model of a chevron plate heat exchanger was developed with thermal and momentum transfer analogies. Empirical correlations for momentum transfer and void fraction (validated in part I of this study) were implemented in the numerical model. The numerical model, coded in Maple 13 (TM), was used to size a compact reactor with a thermal load rating of 2 kW for the desired operating temperature; the modeling framework developed can also be used to study different candidate gas-generating reacting species, working fluids, and PHE configurations. (C) 2013 Elsevier Ltd. All rights reserved.