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The Hygroscopic Cycle is a thermodynamic cycle converting thermal energy into mechanical power by the means of a steam turbine. It is similar to the Rankine cycle using water as the motive fluid but with the novelty of introducing salts and their hygroscopic properties for the condensation. The salts are desorbed in the boiler or steam generator, where clean steam is released and superheated in order to be expanded and generate power through the steam turbine. Boiler blowdown with the concentrated hygroscocpic compounds is used thermally to pre-heat the steam turbine condensate, and as reflux in the steam-absorber. Condensation is done in a steam absorber, as opposed to the traditional condenser found in the Rankine cycle. Here the outlet steam is absorbed by cooled hygroscopic compounds using the same principles as in absorption refrigarators. These hygroscopic compounds are cooled by an air-cooler, where the heat of condensation is dissipated by an air-cooler. Because of the thermal recovery of the boiler blowdown, the hygroscopic reaction in the steam condenser, and the use of an air-cooler to dissipate the heat of condensation, the efficiency of the cycle is higher, with a higher electrical output,reduces or eliminates the need for cooling water, (reduces the operating costs ), and (the capital cost of the utility power plant ). == Principles == The hygroscopic effect of salts is well known and used in Absorption refrigerators where heat is used for refrigeration. In these machines, the refrigerant is absorbed-dissolved into another fluid (a hygroscopic fluid), reducing its partial pressure in the evaporator and allowing more liquid to evaporate. In the hygroscopic cycle, the gas absorbed-dissolved into the other fluid is the steam coming from the outlet of the steam turbine. As the steam is absorbed-dissolved into the hygroscopic fluid, more steam can condense, and the reduction in vapor pressure is equivalent to a reduction in the condensation pressure at the outlet of the steam turbine. The effect of this is that a steam turbine with a lower outlet pressure can be used, with a lower enthalpy level at the outlet of the turbine. This increases the efficiency of the turbine, and generates a higher electrical output. In the steam absorber, steam is absorbed with a concentrated hygroscopic fluid. As the steam is absorbed, the concentration of the hygroscopic fluid decreases, or the salt is diluted. Hygroscopic / deliquescent fluids with a high dilution capacity in water, such as LiBr usually also show a high saturation temperature / low saturation pressure. In other words, the deliquescent fluid can condense vapor at a higher temperature. This means that the temperature of the concentrated hygroscopic fluid entering the absorber can be higher than a non hygroscopic fluid. As a result, the cooling is easier than in a conventional Rankine cycle in the condensation section by using an air-cooler to dissipate the heat of condensation in the refluxed concentrated hygroscopic fluid mentioned earlier. With the appropriate salts, this can ''reduce, or even eliminate the (consumption of cooling water in the power plant )''. Cooling water circuits in power plants (consume a high amount of fresh water ) and chemicals, and their alternative, electric (air cooled steam condenser ) consumes part of the power produced in conventional power plants, reducing the Rankine cycle efficiciency. The air-cooler used in the hygroscopic cycle cools a liquid flow with concentrated hygroscopic compound, with an overall volumetric heat capacity much higher than the steam traditionally condensed in air cooled condenser mentioned earlier, thus reducing the (power needed for ventilation ), and needing less surface area for heat exchange and obtaining a lower overall cost of the plant. Cooling water circuits are also expensive, require numerous equipment, such as pumps and cooling towers, and (expensive water treatment ). Thus by reducing the cooling water needed, the operating costs of the plant will be reduced. Depending on the salts chosen, in particular those with a high dilution capacity (i.e. LiBr), saturation temperature of the hygroscopic fluid can be up to 40°C higher than the steam leaving the turbine. The salts are concentrated in the boiler, as steam is disengaged from liquid water. Given that the concentration of salts increases, the boiling point temperature of the mixture of salts is affected. In most salts, this will increase the boiling point temperature, and the steam temperature that is disengaged.〔http://patentscope.wipo.int/search/en/WO2010133726〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hygroscopic cycle」の詳細全文を読む スポンサード リンク
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