In order to investigate the effect of various parameters on the adsorption chiller performance, the adsorbent bed should be modeled with appropriate governing equations and assumptions. In order to study the adsorption chiller numerically, the governing equations should be modeled in four domains of thermal fluid, metal tube, fins and adsorbent bed simultaneously. One of the assumptions, which greatly influenced the modeling complexity and computation cost is the uniform pressure approach for the bed. For some of modeling conditions the pressure of the bed should be calculated and the inter particle resistance cannot be neglected. In this study with comparing the governing equations of uniform pressure and non-uniform pressure approach, a dimensionless number is introduced and a limiting value is determined with the help of numerical results such as specific cooling power. This parameter can be employed to decide about the appropriate bed pressure assumption prior to start the modeling process.