In this project, self-build CFD code in C++ is employed to simulate several classical fluid dynamic, heat and mass transfer problems such as Driven Cavity, Deferential Heat Cavity, Square Cylinder problem. Besides, this work also includes a code of absorption chiller in condition of falling film, and the result of the code will be compared with previous work of other researchers. The inform consists of 6 chapters. Chapter 1 is introduction where the objective and scope is explained. In chapter 2, the govern equation of both mass, momentum and energy equation will be deduced at different conditions using different hypothesis and simplification. In chapter 3, the discretization of the govern equation and the mesh of the domain will be carried out. In chapter 4, the algorithm of fractional method step will be explained and, also the algorithm for the falling film. In chapter 5, the result of each corresponding code will be compared with high resolution benchmark result. In the final chapter 6, an experiment of component of absorption chiller with falling film of aqueous LiBr driven by gravity is carried out. The experiment should be operated in vacuum condition at absolute pressure around 1000 Pa, but no experiment data is acquired due to the lack of time. The information of experiment apparatus will be demonstrated in the annex.