Original scientific paper
The Ambient Temperature Influence on the CO2 Low-power Marine Waste Heat Recovery Plant at Several Loads
Nikola Anđelić
; University of Rijeka, Faculty of Engineering, Rijeka, Croatia
Sandi Baressi Šegota
; Juraj Dobrila University of Pula, Faculty of Informatics, Pula, Croatia
Igor Poljak
; University of Zadar, Maritime Department, Zadar, Croatia
Vedran Mrzljak
orcid.org/0000-0003-0323-2600
; Univerity of Rijeka, Faculty of Engineering, Rijeka, Croatia
Abstract
This paper presents an exergy analysis of a marine CO2 low-power waste heat recovery plant and its
individual components under varying ambient temperatures and three load conditions. At nominal
load, the analyzed power plant produces only 146.95 kW of useful power. An increase in ambient
temperature results in higher exergy destruction and a simultaneous decrease in exergy efficiency
for both the whole plant and each plant component. Considering all loads and ambient temperatures,
all turbomachines from the analyzed plant (turbine, main compressor, and auxiliary compressor)
exhibit high exergy efficiencies (exceeding 90%). The exergy efficiencies of the turbomachines are
higher in comparison to any heat exchanger from the observed power plant. Within the analyzed
ambient temperature range, the cumulative change in exergy efficiency of each turbomachine at any
load is approximately 1% or less, while the cumulative change for each heat exchanger at any load
is approximately 4% or higher. This indicates that turbomachinery performance is considerably less
sensitive to ambient temperature variations than that of heat exchangers. Among all plant components,
the cooler demonstrates the lowest exergy efficiencies, not exceeding 38%. Furthermore, its exergy
efficiency is several times more sensitive to ambient temperature changes compared to the other
plant components. Under optimal operating conditions, the overall plant exergy efficiency reaches
approximately 34%. This relatively low exergy efficiency of the whole plant can be attributed to the use
of only a single waste heat flow from a marine low-speed diesel engine (combustion gases). For such
CO2 waste heat recovery plants, it is recommended to use various waste heat flows from the internal
combustion engine at different temperature levels – in that situation much higher exergy efficiencies
of the whole plant can be achieved.
Keywords
the ambient temperature change, exergy analysis, CO2 waste heat recovery plant, various plant loads
Hrčak ID:
346277
URI
Publication date:
14.4.2026.
Visits: 114 *