In the present paper, a model-size shell-and-tube heat exchanger with horizontal baffles is investigated numerically and compared to the measured values using the commercial software SC-Tetra V11. Determination of the heat transfer coefficients for the shell side depends on the type of the flow and the type of the baffles. Without baffles the shell side medium leaves in the shortest way, and dead zones are formed. With the usage of these baffles, the flow path is artificially formed and the flow velocity will be increased because of the decreased flow area. These two effects will cause a better heat transfer but the other hand this will increase the weight of the heat exchanger. There are very simple experimental correlations for the segment and disk-and-donut types baffles. However, must be known the real heat transfer coefficient in case of an optimal design. This study investigated the effect of the type of the baffles, the space between them and the baffle cut to the real heat transfer coefficient and the necessary material quantity and compared the simulated heat transfer coefficients with analytically calculated ones based on the literature.