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Abstract

The objective of the study reported in this paper was to determine the effect of structure on thermal power of cast-iron heat exchangers which in this case were furnace chambers constituting the main component of household fireplace-based heating systems and known commonly as fireplace inserts. For the purpose of relevant tests, plate-shaped castings were prepared of gray iron with flake graphite in pearlitic matrix (the material used to date typically for fireplace inserts) as well as similar castings of gray cast iron with vermicular graphite in pearlitic, ferritic-pearlitic, and ferritic matrix. For all the cast iron variants of different structures (graphite precipitate shapes and matrix type), calorimetric measurements were carried out consisting in determining the heat power which is quantity representing the rate of heat transfer to the ambient environment. It has been found that the value of the observed heat power was affected by both the shape of graphite precipitates and the type of alloy matrix. Higher thermal power values characterize plate castings of gray iron with vermicular graphite compared to plates cast of the flake graphite gray iron. In case of plates made of gray cast iron with vermicular graphite, the highest values of thermal power were observed for castings made of iron with ferritic matrix.

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Authors and Affiliations

Marek Mróz
ORCID: ORCID
A.W. Orłowicz
ORCID: ORCID
M. Tupaj
ORCID: ORCID
M. Jacek-Burek
M. Radoń
M. Kawiński
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Abstract

Calculations were performed of the thermal system of a power plant with installed water pressure tanks. The maximum rise in the block electric power resulting from the shut-off of low-pressure regenerative heaters is determined. At that time, the boiler is fed with hot water from water pressure tanks acting as heat accumulators. Accumulation of hot water in water tanks is also proposed in the periods of the power unit small load. In order to lower the plant electric power in the off-peak night hours, water heated in low-pressure regenerative heaters and feed water tank to the nominal temperature is directed to water pressure tanks. The water accumulated during the night is used to feed the boiler during the period of peak demand for electricity. Drops in the power block electric power were determined for different capacities of the tanks and periods when they are charged. A financial and economic profitability analysis (of costs and benefits) is made of the use of tanks for a 200 MW power unit. Operating in the automatic system of frequency and power control, the tanks may also be used to ensure a sudden increase in the electric power of the unit. The results of the performed calculations and analyses indicate that installation of water pressure tanks is well justified. The investment is profitable. Water pressure tanks may not only be used to reduce the power unit power during the off-peak night hours and raise it in the periods of peak demand, but also to increase the power capacity fast at any time. They may also be used to fill the boiler evaporator with hot water during the power unit start-up from the cold state.

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Authors and Affiliations

Jan Taler
Marcin Trojan
Dawid Taler
Piotr Dzierwa
Karol Kaczmarski
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Abstract

The paper presents the results of calorimetric tests of segment elements of fireplace inserts. The aim of the work was to optimize their thermal power by replacing the previously used gray cast iron with flake graphite with gray iron with vermicular graphite and replacing the existing geometry of the heat transfer surface with a more developed one. It turned out that the thermal power of the test segments made of cast iron with vermicular graphite was higher compared to the segments of the same shape made of gray cast iron with flake graphite. It was found that the use of segments made of vermicular cast iron with a ferritic matrix allowed for an increase in the thermal power value by dozen percent, compared to segments of the same shape made of vermicular cast iron with a pearlitic matrix. The test results showed that the thermal power of the test segments depends on the variant of the development of both the heat receiving surface and the heat giving off surface. The highest value of the thermal power was obtained when ribbing in the form of a lattice was used on both of these surfaces, and the lowest when using flat surfaces.
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Bibliography

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[12] Mróz, M., Orłowicz, A.W., Tupaj, M., Jacek-Burek, M., Radoń, M., Kawiński, M. (2019). Improvement of operating performance of a cast-iron heat exchanger by application of a copper alloy coating. Archives of Foundry Engineering. 19(3), 84-87.
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Authors and Affiliations

Marek Mróz
ORCID: ORCID
A.W. Orłowicz
1
ORCID: ORCID
M. Tupaj
1
ORCID: ORCID
M. Lenik
1
ORCID: ORCID
M. Kawiński
2
M.. Kawiński
2

  1. Rzeszow University of Technology, Al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland
  2. Cast Iron Foundry KAWMET, ul. Krakowska 11, 37-716 Orły, Poland
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Abstract

The paper presents formulas which can be used to determine steam condensation pressure in a power plant condenser in off-design conditions. The mathematical model provided in the paper makes it possible to calculate the performance of the condenser in terms of condensing steam pressure, cooling water temperature at the condenser outlet, and condenser effectiveness under variable load conditions as a function of three input properties: the temperature and the mass flow rate of cooling water at the condenser inlet and the mass flow rate of steam. The mathematical model takes into account values of properties occurring in reference conditions but it contains no constant coefficients which would have to be established based on data from technical specifications of a condenser or measurement data. Since there are no such constant coefficients, the model of the steam condenser proposed in the paper is universally applicable. The proposed equations were checked against warranty measurements made in the condenser and measurement data gathered during the operation of a 200 MW steam power unit. Based on the analysis, a conclusion may be drawn that the proposed means of determining pressure in a condenser in off-design conditions reflects the condenser performance with sufficient accuracy. This model can be used in optimization and diagnostic analyses of the performance of a power generation unit.
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Authors and Affiliations

Rafał Laskowski
1
Adam Smyk
1
Adam Ruciński
1
Jacek Szymczyk
1

  1. Institute of Heat Engineering, Faculty of Power and Aeronautical Engineering, Warsaw University of Technology, Nowowiejska 21/25, 00-665 Warsaw, Poland

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