The aim of this thesis is to analyze the heat transfer in steam generator of blocks in the nuclear power plant VVER 440. The steam generator represents the border between the primary and the secondary circuit. The heat is carried from a warm water from reactor to a cold water. The steam arises
after the heat transfer and drives the steam turbine. An important quantity which represents the heat transfer is a heat transfer factor. This thesis is divided into theoretical and a practical part.
In the theoretical part is mentioned a principle of the steam generator and the theoretical calculation
of the heat transfer factor, which comes first of all from the character of the streaming in the steam generator. The practical part brings a comparison of the heat transfer factor calculated from data measured after the start of the third block of EDU in 1986, with the heat transfer factor which comes
from the measurement after the power-increase for 105 % of nominal power of the same block in 2009. Further is shown the prediction of the heat transfer factor for next power-increase and the following service is shown too.