Original scientific paper
https://doi.org/10.18048/2022.62.01
Thermodynamic Analysis of Steam Cooling Process in Marine Power Plant by Using Desuperheater
Vedran Mrzljak
orcid.org/0000-0003-0323-2600
; Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
Tomislav Senčić
orcid.org/0000-0001-5011-7344
; Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
Igor Poljak
; Department of Maritime Sciences, University of Zadar, Mihovila Pavlinovića 1, 23000 Zadar, Croatia
Vedran Medica-Viola
; Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
Abstract
Thermodynamic (energy and exergy) analysis of steam cooling process in the marine steam propulsion
plant is presented in this research. Steam cooling is performed by using Desuperheater which inject
water in the superheated steam to obtain wet steam. Wet steam is used in auxiliary heaters for various
heating purposes inside the marine steam propulsion system. Auxiliary heaters require wet steam
due to safety reasons and for easier steam condensation after heat transfer. Analysis of steam cooling
process is performed for a variety of steam system loads. Mass flow rates of cooling water and
superheated steam in a properly balanced cooling process should have the same trends at different
system loads - deviations from this conclusion is expected only for a notable change in any fluid
temperature. Reduction in steam temperature is dependable on the superheated steam temperature (at
Desuperheater inlet) because the temperature of wet steam (at Desuperheater outlet) is intended to
be almost constant at all steam system loads. Energy losses of steam cooling process for all observed
system loads are low and in range between 10–30 kW, while exergy losses are lower in comparison
to energy losses (between 5–15 kW) for all loads except three the highest ones. At the highest system
loads exergy losses strongly increase and are higher than 20 kW (up to 40 kW). The energy efficiency
of a steam cooling process is very high (around 99% or higher), while exergy efficiency is slightly
lower than energy efficiency (around 98% or higher) for all loads except the highest ones. At the highest
steam system loads, due to a notable increase in cooling water mass flow rate and high temperature
reduction, steam cooling process exergy efficiency significantly decreases, but still remains acceptably
high (between 95% and 97%). Observation of both energy and exergy losses and efficiencies leads
to conclusion that exergy analysis consider notable increase in mass flow rate of cooling water which
thermodynamic properties (especially specific exergies) strongly differs in comparison to steam. Such
element cannot be seen in the energy analysis of the same system.
Keywords
Steam cooling; Desuperheater; Thermodynamic analysis; Marine power plant
Hrčak ID:
281441
URI
Publication date:
23.8.2022.
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