In the search for new forms of renewable energy production, an interesting option is to make use of the energy stored in the ocean in tropical areas. The sun heats up the surface water in these areas to a point it is feasible to generate electricity, using the temperature difference between the hot surface water and the cold ocean water at around 1 [km] depth. This form of renewable energy production is called Ocean Thermal Energy Conversion (OTEC). As the water temperature in these areas is quite constant, the electricity generation is quite constant as well, which is a big advantage as no inefficient energy storage or unsustainable base load generation is needed. To make OTEC power generation more economically attractive, design optimization and technology up-scaling need to be done, lowering the costs of the components and making sure the components work as efficiently as possible. A crucial component is the condenser. In the condenser, heat is transferred from the working fluid in the cycle (most commonly ammonia or ammonia-water) to the cold water. The working fluid is condensed, which can then be pumped around. The process of pumping the water up from 1 [km] depth is a costly operation (Kirkenier, 2014) and the condenser itself is a significant part of the cost of an OTEC-plant. It is relevant to gain more insight in the transport phenomena in the condenser by executing experiments, so the cost can be reduced. The experimental set-up is a small scale OTEC cycle prototype (OTEC-demo), located in the Process & Energy laboratory at the Delft University of technology. For this research, a gasketed plate heat exchanger is added to the set-up, which can be used as a condenser. On the gasketed plate heat exchanger it is possible to apply some modifications and to change the number of plates, as the heat exchanger can be disassembled. Nine miniature temperature sensors are placed along the flow direction of one of the heat transfer plates for local temperatures measurements. For future research on the flow patterns in the condenser, a transparent corrugated plate was designed and fabricated for visualization purposes. First, the plate was designed with 3D CAD software. Then, the plate was constructed by milling, at the central workshop of the Delft University of Technology. A single phase convective heat transfer coefficient correlation and a pressure drop correlation for the cold water side in the condenser were proposed, by executing experiments with water on both sides of the heat transfer plates in the gasketed plate heat exchanger. In order to research the influence of the vapour quality and the mass flux on the convective heat transfer coefficient on the working fluid side, ammonia-water mixture condensation experiments were executed. During the experiments, the measured cold water temperature profiles were linear for all the set mass flows. This means the convective heat transfer coefficient did not change much along the flow direction of the plate, which can be explained by the small change in vapour quality during the ammonia-water mixture experiments. The convective heat transfer coefficient on the working fluid side increases for increasing mass flux and also increases for increasing vapour quality. The results of these experiments were compared to the theory. A numerical condenser model, which can predict the measured data, was developed. The numerical condenser model is a modification of the numerical condenser model by Goudriaan (2017) and Kuikhoven (2017). By comparing the results of the experiments to the results from the model, the assumptions made in the model can be validated. The model can predict the cold water inlet temperature and the working fluid outlet temperature of the experimental data within an accuracy of 4%. However, this only applies to the measured range of experiments. More experiments are required to propose correlations that are valid in a higher range of mass flows and vapour qualities. Furthermore, pure ammonia experiments were executed. The results were compared to the ammonia-water mixture experiments. The convective and overall heat transfer coefficients decreased for increasing mass flux during the pure ammonia experiments, while the convective and overall heat transfer coefficients increased for increasing mass flux during the ammonia-water mixture experiments. More experiments are needed to investigate this phenomenon. The pressure drop of the pure ammonia flow is slightly higher than the pressure drop of the ammonia-water mixture, due to the lower density of pure ammonia.