Design verification of heat exchanger for ballast water treatment

Using waste heat from ship's engines is one of the methods considered for heat treatment of ballast water. For such a system harvesting the engine exhaust heat, a heat exchanger will be vital. Design optimisation of a heater employing exhaust gases of the engine as utility fluid and ballast sea water as the process fluid was achieved using Lagrangian methods, keeping the annual cost as the objective function. Costs for installation, maintenance as also costs for the utility and process fluids were considered. Heat balance data, specific fuel consumption values from a typical operational ship and current fuel costs were considered for the design. The thermodynamic and geometric designs were worked out using computer based software for comparing the designs. Costs were also computed using a different approach for all the designs. Since the amount of heat transferred was specified and the application was limited to a single process, direct cost method was used for the computation. The objective function values obtained from Lagrangian equations were compared with the values obtained from direct cost computations. From the optimal designs, choice was justified based on annual cost, optimum exit temperature of shell side fluid and optimum mass flow of tube side flui

Envisaging a ballast water treatment system from shipboard waste heat

Non-native alien species cause harm to the environment. Epidemics to economic erosion of value resources are the harmfuleffects that are being experienced. Ballast water Management Convention of 2004 requires effective treatment replacing the currentshipboard practice of ballast water exchanges. With full ratification of the Convention nearing, treatment systems are being approved forcommercial availability. One of the treatment methods is by heat, which sterilises the water from typical marine species. A systemharnessing shipboard waste heat would provide an economic solution for ballast water treatment. Based on an analysis of waste heatavailable onboard an existing crude oil tanker, though heat availability is seen, a complementing treatment method is necessary to treathigh volumes. So, a heat-filtration combination system is proposed. The sea water circulating as secondary coolant in machineries isfiltered and heated by harvesting heat from machinery systems, steam heat rejections and exhaust gases. The treatment protocols areextended during sailing also at no extra cost. The combination promises to overcome sediment retention problems as also improvespecies mortalities. Alternative arrangement instead of back flushing of filters is projected. The system layout is presented as a promisingsolution which could possibly optimise ballast water management. Further analyses are suggested for other vessel types

Optimisation of a waste heat exchanger for ballast water treatment

Ballast Water Treatment systems, which are type approved and commercially available, require improvements to meet stricter standards, and heat treatment could be a viable additional option. Considering the waste heat potential on a ship, a system harvesting the engine exhaust heat may be envisaged for which a heat exchanger could be vital. Design optimisation of a heater, employing the exhaust gases of an engine as utility fluid, and ballast sea water as the process fluid, was achieved using Lagrangian methods, keeping the annual cost as the objective function. Limiting the number of variables, optimal values were calculated with cost considerations for utility fluid and also pumping costs for utility and process fluids. In all, four optimum designs and three comparative designs were developed. Heat balance data from an operational tanker, specific fuel consumption values and fuel costs were considered for the design. The thermodynamic and geometric designs were worked out using computer based software for a comparison. Designs were compared on the basis of annual cost, optimum exit temperature of shell side fluid, optimum mass flow of tube side fluid and heat exchanger effectiveness. It is demonstrated that an optimal heat exchanger design can be obtained with simple optimisation procedures

Ballast water management triad: administration, ship owner and the seafarer

The Ballast Water Convention requires less than 5% of the world tonnage for ratification. Consequently, ships will have to comply with the requirements. Compliance evaluation and enforcement will become mandatory. Ship owners have to invest in treatment systems and shipboard personnel have to operate them and ensure compliance. The monitoring and enforcement will be the responsibilities of the Administrations. Herein, a review of the current status of the Ballast Water Management and the issues faced by these are projected. Issues range from efficacy and economics of the treatment systems to sampling and testing. Health issues of chemical systems, paucity of data for decision support etc., are other issues. It is emphasized that management of ballast water must be extended to ashore and sustainable solutions must be researched upon. An exemplar treatment system based on ship’s waste heat is also suggested

Orphan disease: Cherubism, optic atrophy, and short stature

A 12-year-old female presented with complaints of progressive visual impairment in both her eyes. On clinical examination, she was short for her age and her ophthalmoscopic examination revealed bilateral optic atrophy. Computed tomography of the patient revealed multiple expansile lytic lesions of mandible suggesting cherubism. The optic atrophy was confirmed on magnetic resonance imaging, which additionally revealed bilateral retrocerebellar arachnoid cysts. This association of cherubism with optic atrophy and short stature was grouped as orphan disease by National Institutes of Health and only one case was reported in the literature so far

Prediction of maneuvering behavior of an offshore supply vessel by using simulation program

Manoeuvring ability of Offshore Supply Vessel (OSV) is a very critical aspect. An early prediction of vessel behaviour will definitely help to improve upon the design. The regular methods available for manoeuvring prediction such as free running model test, captive model test etc., are found to be expensive and time consuming. As an alternative, the current approach tries a numerical simulation method with parameters determined from a database. This study presents the manoeuvring prediction of an OSV which includes the development of time domain simulation program by using Matlab Simulink software. Three degrees of freedom were considered and applying the Newtonian laws, the equations of motion were framed. Further, forces on hull, forces and moments induced by propeller and rudder were also taken into reckoning. Results were obtained with inputs of vessel speeds, engine revolutions etc. Validation of the prediction results was also carried out by comparing the results with full-scale sea trial data. The prediction results show a good agreement with the sea trial data. Applying approximate numerical formula for manoeuvring prediction is seen to be a reliable and economic prediction tool at early design stages of such vessels

Laboratory tests on heat treatment of ballast water using engine waste heat

Waste heat recovery from shipboard machineries could be a potential source for heat treatment of ballast water. Similar to a shipboard schematic arrangement, a laboratory-scale engine-heat exchanger set-up harvesting waste heat from jacket water and exhaust gases was erected to test the level of species’ mortalities. Mortalities were also assessed under experimental conditions for cultured and natural plankton communities at laboratory level. Effect of pump impellers on species’ mortalities were also tested. Exposures between 60°C and 70°C for 60 sec resulted in 80–100% mortalities. Mortalities due to pump impeller effects were observed in the range of 70–100% for zooplankton. On the laboratory-scale arrangement, >95% mortalities of phytoplankton, zooplankton and bacteria were recorded. It was demonstrated that the temperature of tropical sea waters used as secondary coolant can be raised to cause species’ mortalities, employing engine exhaust gases. The results also indicated that pump impeller effects will enhance species’ mortalities. The limitations of the shipboard application of this method would be the large ballast volumes, flow rates and time for treatment