In Open-cycle Ocean Thermal Energy Conversion (OC-OTEC) system, the net output power is the difference between the gross power output and the internal power consumption of the system. The main internal power consuming devices of the OC-OTEC system are the intake pumps for the cold deep sea water and the warm surface sea water, and the vacuum pumps or compressor for exhausting non condensable gases from the system. Therefore, the reduction of the internal pumping power of the system is important for the increase of the net power output of the system.
When surface sea water is flash evaporated in the evaporator, dissolved non-condensable gas are released. The non condensable gases have to be continuously removed, otherwise considerable reduction system power output would result. Exhaust vacuum pumps or compressors are used to remove or exhaust this non-condensable gases from the condenser chamber. To determine the pumping power required to remove the non condensable gases, a clear relationship between condenser performance and non-condensable gas concentration have to be established. This paper outlines the experiments performed to obtained this relationship for the particular condenser configuration specified within. The experimental results show that when the concentration of non condensable gases in the condenser exceed 5% by volume, the performance of condenser measured by it's thermal effectiveness ec drops to below 0.8. To keep the non condensable gas concentration below 5%, the exhaust gas discharge rate from the condenser should be at least 10 times the rate at which non condensable gases are released in the evaporator.