The aim of this work is to present an experimental research of the shell side heat transfer coefficient and pressure drop in a plastic shell and tube heat exchanger with single segmental baffle. The tube bundle consisted of 110 U-tubes constructed of high-density polyethylene, the inside diameter was 9.2 mm, the tube pitch was 1.5 the out side diameter. The shell was constructed of polypropylene with a diameter of 315 mm. Shell side heat transfer coefficients and pressure drop were determined varying the flow rates. An experimental rig for the experimental research was designed and constructed. The overall experimental rig consisted of two operation cycles. The two fluids used in this system were hot and cold water. The experimental results were compared with theoretical predictions using the Bell-Taborek and Wills and Johnston Methods. The heat transfer coefficient predictions, for Reynolds number greater than 780, showed that the Bell-Taborek and Wills-Johnston methods are in general agreement with the experimental data with only 5% difference, Wills-Johnston overpredicts it and Bell underpredicts it, except at the lower Reynolds number than 780 where there was an average underprediction of 15%. The pressure drop predictions by Wills-Johnston and Bell-Taborek methods were generally acceptable including the inlet and outlet nozzles with the highest experimental data (Reynolds number greater than 780) within a 15% overprediction, however, at the lower data the pressure drop was overpredicted up to 2 times the measured values.