With the simulation presented heat engineering processes in a vacuum solar collector may be described. The collector consists of a flat absorber, a cylindrical evacuated glass pipe and a heat pipe. For the simulation of the total system, a differential equation was used, which describes the solar temperature of the fluid, heated by the solar collector, along its length and dependent on the time. The solution gives the exit temperature of the fluid dependent on the inlet temperature at any chosen time step. the determination of further parameters (heat resistance, heat capacity, transmission coefficient) is considered in detail. Exemplary calculations were carried out with the help of the assembled computer program on the basis of the technical data of a vacuum solar collector