The present study evaluated biofilm growth in AISI 316L stainless steel tubes for seawater-cooled exchanger-condensers that had four different arithmetic mean surface roughness values ranging from 0.14 μm to 1.2 μm. The results of fluid frictional resistance and heat transfer resistance regarding biofilm formation in the roughest surface showed increases of 28.2% and 19.1% respectively, compared with the smoothest surface. The biofilm thickness taken at the end of the experiment showed variations of up to 74% between the smoothest and roughest surfaces. The thermal efficiency of the heat transfer process in the tube with the roughest surface was 17.4% greater than that in the tube with the smoothest surface. The results suggest that the finish of the inner surfaces of the tubes in heat exchanger-condensers is critical for improving energy efficiency and avoiding biofilm adhesion. This may be utilised to reduce biofilm adhesion and growth in the design of heat exchanger-condensers.

This article discusses the antifouling action of a continuous physical treatment process comprising the application of electromagnetic fields (EMFs) to seawater used as the refrigerant fluid in a heat exchanger-condenser to maintain the initial ‘clean tube’ condition. The results demonstrated that the EMFs accelerated the ionic nucleation of calcium and precipitation as calcium carbonate, which weakened the growing biofilm and reduced its adhesion capacity. Consequently, EMFs induced an erosive effect that reduced biofilm formation and fouling. This treatment allowed for the maintenance of significantly lower fouling factors in the treated tubes compared to a control group of untreated tubes, thereby leading to a higher heat transfer efficiency.

The influence of flow velocity (FV) on the heat transfer process in tubes made from AISI 316L stainless steel in a heat exchanger-condenser cooled by seawater was evaluated based on the characteristics of the resulting biofilm that adhered to the internal surface of the tubes at velocities of 1, 1.2, 1.6, and 3 m s⁻¹. The results demonstrated that at a higher FV, despite being more compact and consistent, the biofilm was thinner with a lower concentration of solids, and smoother, which favoured the heat transfer process within the equipment. However, higher velocities increase the initial cost of the refrigerating water-pumping equipment and its energy consumption cost to compensate for the greater pressure drops produced in the tube. The velocity of 1.6 m s⁻¹ represented the equilibrium between the advantages and disadvantages of the variables analysed for the test conditions in this study.

S-curves are usually taken as expression of project progress and have become a requisite tool for project managers through the execution phase. The common methodology for predicting S-curve forecasting models is based on classifying projects into groups and producing a standard S-curve for each group using multiple linear regression techniques. Traditional regression models taken to fit individual projects require a large amount of data and make many strict assumptions regarding statistical distribution of the data. The grey system theory, however, is well suited to study the behavior of a system with incomplete information or limited amount of discrete data. Easy of use and accuracy, two significant criteria for project managers when choosing a forecasting model, are considered two additional attributes of the grey system theory. This paper proposes a residual Grey prediction model to forecast the actual cost and the cost at completion of a project based on the grey system theory. Results show that the accuracy of the forecasting model is highly efficient.

This study quantitatively evaluates the antifouling action of the continuous physical treatment with electromagnetic fields (EMFs) of seawater used as heat exchanger fluid in an open rack vaporizer (ORV) pilot plant to reduce the growth of biofouling on external rib-tube surfaces. The results demonstrate that the biofilm adhered on the treated rib-tubes was reduced by 33% in thickness and by 44% in dissolved solids regarding the biofilm adhered on the untreated control rib-tubes. The lower conductivity and Ca²⁺ and Mg²⁺ ionic content in the effluent of the treated seawater confirmed that the EMFs accelerated the process of ionic calcium nucleation and precipitation as calcium carbonate. The precipitation of ions dissolved affected the inter-molecular interactions among extracellular polymers, thereby weakening the biofouling film matrix and reducing its adhesion capacity. The drag of small particles by the flow of seawater had an erosive action and decreased the biofouling film thickness. Consequently, the antifouling methods treatment with EMFs allowed reduce the negative effect that the biofouling have for the heat transfer equipment used in regasification process and keep highest techno-economic operating conditions.

Global warming and air pollution are undoubtedly the major issues of our time. As livestock is considered the main source of protein and dairy products and one of the main food sources for humanity, in some regions of the world, livestock vessels serve as the main logistical means of transportation. Reducing emissions from vessels is vital to ensure animal welfare and livestock health. The vessel MV Ganado Express was chosen to evaluate the overall emissions resulting from the main engine during a 24-hour navigation period under full engine load. This study aims to develop an approach to reduce greenhouse gas emissions using hydrogen proton exchange membrane fuel cells as an alternative to the conventional fossil fuel-powered main engine. The study indicates that replacing the ship's conventional main engine with hydrogen proton exchange membrane fuel cells can mitigate CO2 emissions by 10,200 kg, NOx by 1,637 kg, and SOX by 66 kg during a 24-hour sailing period under an engine load of 6,090 kW. During the same sailing conditions, the fuel consumption reduction when using hydrogen proton exchange membrane fuel cells is 62% lower than the fuel consumption when using a conventional diesel engine. Keywords: climate change; International Maritime Organization; zero emissions livestock ships. Viabilidade da utilização de células de combustível de hidrogênio em navios de transporte de gado para mitigar as emissões de gases de efeito estufa RESUMO: O aquecimento global e a poluição do ar são, sem dúvida, os grandes problemas atuais. Como o gado é considerado a principal fonte de proteína e laticínios e uma das principais fontes de alimento da humanidade, em alguns regioes do mundo, os navios de gado servem como os principais meios logisticos de transporte. Reduzir as emissões dos navios é vital para garantir o bem-estar animal e a saúde do gado. O navio MV Ganado Express foi escolhido para avaliar as emissões gerais resultantes do motor principal durante um período de navegação de 24 horas sob carga total do motor. Este estudo visa desenvolver uma abordagem para reduzir as emissões de gases de efeito estufa utilizando células de combustível de membrana de troca de prótons de hidrogênio como uma alternativa ao motor principal convencional movido a combustível fóssil. O estudo indica que a substituição do motor principal convencional do navio por células de combustível de membrana de troca de prótons de hidrogênio pode mitigar as emissões de CO2 em 10.200 kg, de NOx em 1.637 kg e de SOX em 66 kg durante o período de navegação de 24 horas sob uma carga de motor de 6.090 kW. Durante as mesmas condições de navegação, a redução do consumo de combustível durante o uso de células de combustível de membrana de troca de prótons de hidrogênio é 62% menor do que o consumo de combustível durante o uso do motor diesel convencional. Palavras-chave: mudanças climáticas; Organização Marítima Internacional; navios de gado com emissão zero.