Simulation And Study Of The Large Container Ship Waste Heat Recovery System

The large ocean-going ship is an important means of transport in the international trade during the last decades.But due to the unprecedented rise of fuel prices and increasingly stringent regulations of emissions,the energy saving and emission reduction technologies are of growing concern in the shipping industry.The steam Rankine cycle heat recovery system has been widely employed in the large ocean-going vessels to recover the waste heat from the diesel engines,resulting in the substantial energy saving.This kind of heat recovery system is featured of the lower operating costs,the higher security as well as the more matured technology.In this work,the steam Rankine cycle heat recovery system of a large container ship was investigated.The respective equipment energy-saving potential and the boiler optimal heat transfer areas in the examined WHR system were studied based on the WHR model developed in the MATLAB environment.The research contents are as follows:(1)The qualitative and quantitative analysis of the WHR system of large container ships were carried out using the thermodynamics theory;the WHR system mathematical models were developed in the MATLAB environment based on the energy analysis and the exergy analysis,respectively.(2)The engine waste heat recovery system was investigated at 50%,75%,85% and 100% engine load using the in-house energy analysis simulation model at the following cases:(a)feed water not heated,(b)the feed water heated to 80 ℃ using the air cooler high temperature stage and(c)the feed water heated to 120 ℃ using the air cooler high temperature stage.The results show that the engine exhaust heat recycling efficiency,the system efficiency increased extent and the overall system efficiency become higher employing the air cooler energy.In addition,as the engine load increases the engine exhaust heat recycling efficiency rises,and the system efficiency increased extent becomes lower and then higher,whereas the overall system efficiency undergoes the contrary features.(3)The engine waste heat recovery system was investigated at 75% engine load using the in-house exergy analysis simulation model without heating the feed water.The results show that the exergy loss rate and respective coefficients in the heat recovery system evaporator,economizer and steam turbine are relatively considerable and therefore,these three equipment have high energy-saving potential.(4)The boiler heat exchanger areas were optimized using the modeFRONTIER adopting the NSGA-Ⅱ algorithm combined with developed MATLAB waste heat recovery model.The optimization process was carried out based on one typical engine load and the engine operational profile,respectively.The results show that the optimization reduces the heat recovery boiler total heat exchanger areas significantly,and the profit is more substantial based on engine operational profile.