The influences of geometrical parameters on the shell side heat transfer in shell-and-tube heat exchangers are investigated by experiments using 32 different test heat exchangers. The test heat exchangers differ by number of tubes, length, shell and tube diameter, nozzle diameter and tube pitch. From the experimental results it can be confirmed that the influence of the tube pitch is small enough to be neglected in shell-and-tube heat exchangers used in real processes. The heat transfer rate of the longitudinal flow can be calculated from the correlation for turbulent flow in concentric annular ducts by inserting the porosity insted of the ratio of tube to shell diameter. The influence of the cross flow in the nozzle region increases with decreasing length of the heat exchangers. The heat transfer coefficients in the nozzle region are determined by comparing the overall heat transfer coefficients of the heat exchangers with that calculated from the correlation for the longitudinal flow. The results show that the heat transfer coefficient in the nozzle region is 40% greater than that in the parallel region, if the length of the apparatuses is about 30 times tha hydraulic diameter. A new correlation suitable for predicting the heat transfer coefficient is presented, which consists of a superposition of the Nusselt number for the flow in the nozzle region and that for the longitudinal flow.