This thesis is based on the numerical simulation of flow and heat transfer in a plate heat exchanger. At the beginning, brazed plate heat exchangers are explained and the application of the finite volume method for the numerical simulation of flow and heat transfer is shown and described. The geometry of the heat exchanger was created in the NX 12 computer program with the help of the data from the SWEP Software Package (SPP) tool. Based on the geometrical characteristics, a CFD calculation of the flow in the fluid-fluid type plate heat exchanger was performed in the Ansys Fluent program. The simulation was carried out for two geometries. One geometry represents a flat plate of heat exchanger, while the other has a sinusoidal cross-section. With regard to the same given input parameters (inlet temperature and inlet mass flow rate), the exchanged heat flow rates were obtained. The B5TH heat exchanger has a sinusoidal cross-section and can exchange greater heat flow rate, while a flat plate has a smaller exchanged heat flow rate in comparison to a sinusoidal plate. Mass flow rates, input and output velocities, inlet and outlet temperatures are also shown in the results. At the end, a comparison of the exchanged heat flow rates in relation to the working media is made. The working media that were compared were water, R32, R125, n-Hexane, olive oil, a mixture of Glycerol and water, a mixture of Ethylene Glycol and water. Results and discussion are presented after the CFD calculations. The final result indicates that the working medium water-water and the mixture of Ethylene Glycol and water give the best results, while olive oil and R125 give the least exchanged heat flow rate.