Steam condenser is a device in which the exhaust steam from steam turbine is condensed by means of cooling water. The main purpose of a steam condenser in turbine is to maintain a low back pressure on the exhaust side of the steam turbine. The cooling water absorbs the latent heat of steam released during condensing. The condensed water returns to the boiler (through deaerator) for steam reproduction, while the cooling water is headed to cooling towers for the release of the absorbed heat at the environment. A cooling tower uses water as a cooling medium and emits steam. If cooling water is not available, a fan-mounted air cooler can serve the purpose, although it is less energy-efficient. Moreover, an air-cooler is less appropriate in hot environments, as the cooler dimensions are increased with the ambient air temperature.
Cooling towers can be split into two distinct categories: open circuit (direct contact) and closed circuit (indirect) systems. In the first system the recirculating water returns to the tower after collecting heat and is then distributed across the tower, where the water is in direct contact with the atmosphere due to its recirculation through the tower structure. Closed circuit systems differ in the circulation of the return fluid (often water, or sometimes water mixed with glycol). The latter circulates through the tower structure in a coil and thus it is not exposed directly to the air, while the cooling tower water recirculates on its own in the tower structure.
In case of the air cooled condensers, the condensation system consists of vacuum heat exchangers cooled by ambient air flow. Exhaust steam from turbine is fed directly to the heat exchanger piping network of the air cooled condenser. Ambient air, which acts as the cooling mean, passes through condenser’s tubes and absorbs latent heat from steam and transfer the heat energy to the environment. Condensed water flows by gravity to the condensate tank located below; it is then fed back to the deaerator by condensate pumps.
The air cooled condenser is a multi-cell unit with each cell comprising tube bundles mounted in an inverted “vee” arrangement and a cooling fan placed horizontally beneath the heat exchange surface to provide a forced draught air discharge over the extended surface tube banks. The diameter and speed of the cooling fans are carefully selected to provide low operating noise levels. An Air Cooled Condenser is made of modules arranged in parallel rows. Each module contains a number of fin tube bundles. An axial flow, forced-draft fan located in each module forces the cooling air across the heat exchange area of the fin tubes.