The heat rejection system of a plant, which deals with the circulating water, requires a separate instrument that is called a condenser. The original purpose of a condenser is to condense the steamed working fluid and thus recover the high-quality feedwater for reuse in the cycle. Condensers are operated in power plants to condense exhaust steam from turbines and refrigeration plants to condense refrigerant vapors, such as ammonia and fluorinated hydrocarbons. Condensers increase the enthalpy drops and turbine work by lowering the turbine outlet pressure. The lower the pressure, the higher the efficiency and power; hence, it is vital to employ cooling working fluid temperatures that are the lowest available.
Gas Turbines basically consist of three main sections:
Condensers are broadly classified into two types: Direct Contact Condenser and Surface Condenser. Direct contact type condenser is not a typical type of condenser because, in this type of condenser, the cooling water is directly sprinkled into the steam. To do that, the cooling water of the same quality as that of steam is required, which is very high-priced and not economical. So, Surface Type condensers are used in the majority of power plants, in which the cooling water is crossed through the tubes, and the steam flows in the shell of the heat exchanger. This water takes the heat of the water and circulates continuously for converting steam into water.
According to the external fluid, condensers can be classified into Water-cooled condensers, Air-Cooled Condensers (ACC), and Evaporative condensers. As the name implies, in a water-cooled condenser, water is the external fluid. In an air-cooled condenser, the air is the external fluid, i.e., the working fluid rejects heat to air flowing over the condenser. In an evaporative condenser, both air and water are employed to extract heat from the condensing working fluid. Evaporative condensers are commonly utilized in medium to large capacity systems.
The Components of the Condenser unit are Ejector, Condensate Pump, Tube, Water box, and Hot well. The ejector’s function is to make the condensation room inside the condenser become vacuum to quickly use steam from the turbine flows into the condenser chamber. The condensate pump pumps condensate water from the reservoir (Hot well) to the filling water tank. The cooling-water pump pumps water into the condenser and another cooling stream pumped from the river, sea, or reservoir (also cooling towers in power plants) for units that use closed cooling. The tube is a place of cooling water flow and is the spot where the heat transfer process between steam and cooling water happens. The water box is a passage for cooling steam. A hot well is a place for collecting water from condensation. Based on the condensing unit type, the heated water is releasing to the sea water or a river (once through condenser), or passing it through a cooling tower unit.
The working principle of the condenser is the same as heat exchangers, particularly the heat transfer process between two flow streams separated by a solid wall. The heat contained in the steam phase is removed by transferring to the cooling flow.
All condensers operate by eliminating heat from the gas or vapor; once sufficient heat is eliminated, liquefaction occurs. A heat pump transfers heat from a low-temperature heat source into a higher temperature heat sink in the refrigeration cycle. The most typical of the refrigeration cycles employs an electric motor to drive a compressor, which is located inside the condensing unit. Because evaporation happens when the heat is absorbed, and condensation occurs when the heat is released, air conditioners are devised to utilize a compressor to cause pressure changes between two sections and actively pump working fluid around. Inside the condenser, the working fluid vapor is compressed and pushed through a heat exchange coil, condensing it into a liquid and discarding the heat previously absorbed from the cool indoor area.