Steam-water injectors are devices in which exchange of mass, momentum and energy between two fluids being in direct contact, occurs. They can operate as pumps, mixers or direct contact heat exchangers. In the last aspect their use as feed-water heaters in Rankine thermal cycle of steam power plants both in land and sea applications (to merchant and naval ships) is very interesting. This paper presents selected results of heat-and-flow investigations of a supercritical steam-water injector, obtained in Institute of Fluid Flow Machinery, Polish Academy of Sciences (IMP PAN). On their basis value of average heat transfer coefficient for mixing chamber was determined; the obtained values were even a few dozens greater than those for classical shell-and-tube heaters. In the theoretical part of this work is presented an original injector model based on balances of mass, momentum and energy, written for control volumes containing separately particular elements of injector. On the basis of the model flow parameters in characteristic cross-sections of injector were determined. The calulations were performed for two different injectors tested in IMP PAN (Gdańsk) and SIET (Piacenza, Italy), and their good compliance with experimental data was achieved.
In this paper a problem is discussed of thermal degradation of shell-and-tube recuperative feed-water heaters due to heat transfer surface fouling. Application (to an example steam cycle of power plant) of DIAGAR software system intended for the analysing of impact of degradation of a particular heat exchanger on whole recuperative system performance, is presented. On the basis of the systematically performed simulative calculations it was concluded that the degradation of feed-water heaters of the lowest extraction pressure results in an additional load imposed on the heaters of higher extraction pressures, moreover it was estimated that the degradation of the heaters due to presence of sediments of the thermal resistance reaching 5*10-4 m2*K/W, has resulted in the drop of turbine set efficiency by about 0.3%. Such drop depends on a given configuration of degree of degradation of particular feed-water heaters applied in a considered turbine set.
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