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Evaluation of the thermal degradation process within the steam power plants heat exchangers

100%

Hajduk T.

tom Vol. 23, No. 4

127--133

The consequence of the deposits presence on the heat transfer surface of the following heat exchangers: shell-and-tube condensers, the regenerative feed water exchangers, are commonly the loss of heat exchanger capacity, owing to the high value of heat conductive resistance of fouling. The process is more often defined as the thermal (heat) degradation of a given heat transfer device. The symptoms of heat degradation are usually defined as the difference between the values of thermal-flow parameters for the current and the reference state. Moreover, this process always entails an increase in the cost of energy conversion, leading to increasing the emission output of greenhouse gases consequently increasing the environmental degradation. It is worth mentioning that deposits settled on the waterside of heat transfer surface could also initiate the process of tubes obliteration. This phenomenon is characteristic for condensers cooled by seawater in particular. Reducing internal diameter of any single heat exchanger pipe by the deposits cause the rise in flow resistance and also reduce the condenser cooling water pump capacity. Ultimately, it leads to the reduction in water flow rate, resulting in an additional increase in the resistance of heat transfer. Furthermore, reducing the flow rate of cooling water causes the enhancement of the fouling settling rate. The paper describes the above-mentioned phenomena and presents the quantitative determinants of the thermal degradation description for heat exchangers based on the results of the author’s own experimental research.

Research of deposit accumulated on heat exchange surfaces in the light of thermal degradation of heat exchange aparatus of steam power plants. Part I: study of real sediment

88%

Hajduk T.

tom nr 1

99--107

The presence of deposits on heat exchange surfaces in condensers and regenerative exchangers of ship and land steam power plants is always connected with the increase of the wall temperature on the water vapor side due to additional thermal resistances resulting from accumulated deposits. This increase always results in an increase in the condensing pressure, which results in the deterioration of the condensation process of the water vapor, leading to thermal degradation of a given heat exchanger. In addition, the resulting deposits form unevenness with a diversified, often stochastic, geometric structure of the surface layer surface, whose measure is most often the roughness parameters, describing the geometric structure of the surface. In addition, the increase in surface roughness of the heat transfer surface on the water vapor side promotes the formation of a thicker layer of condensate, thus worsening the organization of condensate runoff, which results in interference of the thermal degradation phenomenon of a given heat exchange apparatus. As a result, these phenomena lead to a reduction in the efficiency of a given thermal system, and thus entail an increase in the costs of energy conversion and consequently cause an increased degradation of the natural environment. In the article, based on the results of the author’s own experimental research, the types of pollution accumulating on heat exchange surfaces on the water vapor side of heat exchange apparatus in marine and land steam power plants and quantitative measures of the unevenness of the surface layer of these sediments are presented.

Ocena mocy cieplnej aparatów wymiany ciepła siłowni parowych dla różnych stanów ich użytkowania w aspekcie degradacji termicznej

63%

Hajduk T.

tom nr 108

43--54

Odkładające się osady na powierzchniach wymiany ciepła wymienników ciepła w okrętowych i lądowych siłowniach parowych są przyczyną m.in. wzrostu spiętrzeń temperatur oraz związanego z tym pogorszenia stopnia próżni w skraplaczach. Proces degradacji termicznej prowadzi zawsze do zmniejszenia strumienia cieplnego transportowanego przez wymienniki, a w końcowym efekcie do zmniejszenia sprawności danego układu cieplnego. Okazuje się jednak, że utrata mocy cieplnej wymiennika ciepła nie zależy tylko od wartości samych oporów ciepłych osadów, ale jest również ściśle skorelowana z atrybutami cieplnymi wymiennika ciepła, tj. wartościami współczynnika przenikania ciepła w różnych stanach eksploatacyjnych wymiennika. W artykule opisano powyższe zjawiska oraz zaprezentowano rezultaty własnych badań eksperymentalnych.

The fouling presence on the heat transfer surfaces of the heat exchangers within the stationary and the ship steam power plants cause an increase in terminal temperature difference values and entails a decrease of the vacuum level, as well. The thermal degradation process always leads to reducing the thermal flux transported by the heat exchangers and decreasing total efficiency of the thermal unit, finally. It turns out, however, that the loss of thermal power of a heat exchanger does not only depend on the fouling thermal resistance but is also closely correlated with the thermal attributes of given heat exchanger, i.e. the heat transfer coefficient values at various operating conditions for that heat exchanger. The article describes the above-mentioned phenomena and presents the results of the author’s own experimental research.