Авіаційно-космічна техніка та технологія (Aug 2023)
Efficiency of marine power plants with heat exchangers made from tube bundles with dimple systems
Abstract
The direction of increasing the efficiency of marine power plants by using heat exchange elements that implement intensive methods of heat transfer, which are characterized by a predominant increase in heat transfer over aerodynamic resistance, is considered. The research method is mathematical modeling of processes in power plants at the level of their individual elements – heat engine, power, and technological heat exchangers. The adequacy of the mathematical model for research the efficiency of power plants is justified by the results of verification and validation by comparing the results of calculations with the results of a physical experiment that have a discrepancy not exceeding 9.3 %. The goal of the research is to improve the economic, environmental, resource and weight-size parameters of power plants by using heat exchange elements with the intensification of the processes of convective transfer of heat and mass by using finned surfaces with dimples. Thanks to the performance of dimple systems on the edges of round pipes with spiral-ribbon finning and elliptical pipes with lamellar finning, it is possible to increase the heat transfer coefficient up to 36 %, while the resistance coefficient of the beam remains unchanged. The use of heat exchangers with the proposed heat transfer elements as part of ship power plants with low-speed engines and gas-and-steam turbine units allows to improve their economic and environmental characteristics. It was obtained that for tankers of the PANAMAX type, the increase in the efficiency of the ship's power plant is 1.3 % due to the use of elliptical surfaces with plate finning and hole systems on the ribs in the utilization boiler. The ship's EEDI index decreased by 1.7 %. For container ships with a deadweight of more than 100,000 tons, the change in these indexes was 2.5 and 2.7 %, respectively. For a marine gas-and-steam turbine plant, the efficiency increase was 2.4 %. The presented mathematical model of the power plant is characterized by positive results of approbation for constructive and verification calculations of power plants in marine energy, transport, and industry.
Keywords
