The spray forming process is the process in which a molten metal is impinged by inert gases which results in atomized droplet. The resulting metal droplets while on flight and in residence time inside the spray cone cools rapidly before impinging onto the substrate. The temperature of smaller droplet drops down very fast and strikes the substrate in solid state while larger droplet strike the substrate in liquid form. Therefore to get the mushy droplet impinging on to the substrate knowledge of the thermal history of droplet is of utmost important. In order to determine the size of the cooling chamber of gas atomization plants, a fundamentally based mathematical model was described and the governing differential equation was solved using mathematically modelling method, and the relation between the flight distance and the time was established, then it is solved with the help of initial and boundary condition. With the help of the atomizer angle the size of the cooling chamber is calculated by the help of trigonometry.