This paper presents an analysis using a model of the dispersion process of a Diesel spray impinging on a flat wall. The objective is to simulate the spray / wall interaction process inside Diesel engines. This analysis has two parts: one for non - evaporative spray and the other for evaporative spray. For the non - evaporative spray analysis, a single spray of n - tridecane was injected at high - pressure from a single hole nozzle into a quiescent atmosphere at room - temperature. The spray impinged vertically on the wall at room temperature. Thus, the wall temperature Tw was less than the saturation temperature Tsat of the fuel, that is the boiling temperature. A new submodel including fuel film formation on the wall, its breakup process due to droplet impingement and the dispersion process of breakup - droplets was developed. Also, the droplet density distribution was measured experimentally by the laser light extinction method. For the evaporative spray analysis, the fuel spray was injected into a high - pressure and high - temperature atmosphere and impinged on a wall at a temperature of 550 K. Here, Tw was above Tsat. A submodel for the heat transfer from the wall to the droplet, the breakup behavior of impinging droplets owing to boiling at the liquid - solid interface and the dispersion process of breakup - droplets was considered. Further, the vapor and the liquid phases in the spray were separated experimentally by using exciplex fluorescence method. The new submodels for both temperature conditions were incorporated into the KIVA code and compared with the spray/wall impingement model of Naber & Reitz to calculate the dispersion process. It was found in 2 - dimensional calculations that the new submodels have better qualitative agreement with the experimental one, when compared with that of Naber & Reitz.