This research aims to develop a time-efficient physics-based model for laser directed energy deposition through coaxial powder feeding (LDED-CPF). A clear understanding of the interaction of the laser beam, powder, and substrate and its effects on the temperature field and geometrical characteristics of the melt pool, is of tremendous importance. This research first tries to analytically couple the moving laser beam, the powder stream, and the semi-infinite substrate. A process model is then developed for single-track deposition and experimental validation is conducted by depositing a titanium alloy (Ti-5553) at different laser powers and carrier gas flow rates. Moreover, an alternative method is established to estimate the deposit height based on the melt-pool projection and a process window is developed to consider more physics. Using the developed model, the processing parameters can be efficiently selected and the geometry and temperature field can be predicted for the single-track depositions.