The task of this paper includes the analysis of heat exchange in a plate heat exchanger. In order to understand the physical phenomena that takes place in the mentioned thermal device, the basic mechanisms of heat transfer are described: conduction, convection and radiation. After that, heat exchangers classification is shown and a brief description is given for all of them. Plate heat exchanger is described separately since it was analyzed in this work. In order to solve the physical problem, a mathematic model of fluid flow and heat transfer is defined, ie the calculation area is defined, and the conservation differential equations and boundary conditions are presented. Furthermore, a description of the laboratory measurement, as well as the values of the measured quantities, are given in the following parts. Laboratory measurements were performed for several cases of different input velocities and temperatures. The observed physical problem was also solved numerically using the Ansys software package and Fluent computer program. For this purpose, a description of the used numerical method is given, as well as a description of the applied discretization scheme and algorithm for solving the pressure and velocity fields. Also, the paper describes the implementation of numerical calculation in previously mentioned computer program, which includes the creation of geometry and structured mesh, their displays, and calculation settings in Fluent. The final chapters refer to the analysis of heat exchange in the observed plate heat exchanger, separately for numerical calculation and experiment approach, and for variable input parameters of water currents. The results obtained by numerical calculation were compared with the results of experimental measurements. After the results comparison, it is concluded that the results of the numerical calculation are in good agreement with the results of the experimental measurements.