Split-type air conditioners (SACs) are widely used in households and offices. To aid the design of a SAC, this study develops a theoretical thermohydraulic and condensing phase-change model for the two-dimensional indoor unit of a small-sized SAC. It also adopts the Computational Fluid Dynamics (CFD) software-ANSYS FLUENT V19.1 to analyze its internal flow field and heat and mass transfer performance. To simulate the thermal performance of the evaporators, we employed the non-equilibrium thermal model to predict the temperature distribution of the aluminum fins and wet air. The two-phase mixture model was used to simulate the transport phenomena of wet air and liquid water within the SAC. We used Fick’s law and Chilton-Colburn analogy to predict the condensation rate on the surfaces of the round tubes and the compact fins of the evaporators, respectively. We also compared the results of the volume flow rate and the sensible and latent heat capacities of the indoor unit predicted by the CFD method with those measured by the experiments, revealing that both results were in close agreement and that the model developed in this study was accurate.