Marine Heat Exchangers Research Articles

Corrosion Behavior of Ni/NiCr/NiCrAlSi Composite Coating on Copper for Application as a Heat Exchanger in Sea Water.

This study introduces a novel Ni/NiCr/NiCrAlSi composite coating to enhance the corrosion resistance of copper, particularly for its use in marine heat exchangers. Utilizing characterization techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), the paper investigates the coating's composition, structure, and corrosion resistance in 3.5 wt.% NaCl aqueous solutions. A significant focus is placed on the role of aluminum within the NiCrAlSi layer, examining its influence on the coating's structure and corrosion behavior. The results indicate that the NiCrAlSi layer with an aluminum content of 5.49 at.% exhibits the most improved corrosion resistance, characterized by the highest corrosion potential and a corrosion current density that is more than one order of magnitude lower compared to the Ni/NiCr coating. The effectiveness of this composite coating is attributed to its multilayer structure and the synergistic effect of alloying elements Cr, Al, and Si, which collectively inhibit corrosive medium penetration. These insights present the Ni/NiCr/NiCrAlSi coating as a promising candidate for copper protection in sea water environments, merging enhanced durability with cost-effectiveness.

Redesign of an Exhaust Gas Economiser Using Software

Approaches to heat exchanger designs are numerous. Marine heat exchangers are usually single and they do not form part of a large network. Selections are generally based on the duties, area and the heat quantum. Over capacities and un-optimised designs could result. As an exercise to verify the choice, an existing heat exchanger on board of an operational ship was redesigned using computer software with thermodynamic data and standard geometric values. The formulae employed in the software were extracted and verified. The geometric data was used to develop the design drawings using SolidWorks®. Visualising the designs, the physical arrangement was improved. Comparisons and design improvements were made keeping the standard values in view. With the exercises, a method of developing an optimised physical design reducing the number of rating runs has been demonstrated.

Role of Iron in the Inhibition of Corrosion of Marine Heat Exchangers — A Review

Abstract It was observed in 1907 that iron corrosion products in the cooling water of a marine condenser reduced tube corrosion. However, although intensive investigations in England reported in 1924 further emphasised the importance of iron corrosion products in reducing corrosion of copper base alloys, it is only very recently that the mechanism aspects of this role of iron have been reopened.This review traces the history of the role of iron corrosion products as a corrosion inhibitor with particular reference to (a) the presence of iron corrosion products in the cooling water derived from either sacrificial galvanic iron protector blocks or by injection of ferrous sulphate into the system; (b) iron corrosion products provided from iron incorporated as an alloying element in the tube or tube plate material, considering in particular copper–zinc, copper–nickel and aluminium–bronee alloys.It is concluded that, although the actual mechanism of corrosion inhibition depends on the source of iron corrosion p...