Performance analysis of supercritical ORC utilizing marine diesel engine waste heat recovery

Marine diesel engine is widely used in merchant ships as a propulsion system. The wasted heat of the diesel engines is one of the main drawbacks in this system. The aim of this paper is to recover this wasted heat to be used in designing combined heat and power plant. A bulk carrier WADI SAFAGA has been investigated as a case study. Power and electricity from Supercritical Organic Rankine Cycle will be produced as wasted heat recovery of the main engine. Maximum power, thermal efficiency and specific fuel consumption have been investigated according to the change of the evaporating pressure of organic fluid from 50 bar to 75 bar with increment of 5 bar. Heat exchangers must be redesigned due to the replacement of cooling water by refrigerant (R34a and R245fa). Also, parametric and economic studies will be taken into account. A comparison between diesel generator and SORC generator will be studied from economic and weight dimensions together with the specific power of generator point of view. The results showed that using SORC with R134a at working pressure of 50 bar have a satisfied performance with respect to the saving in specific fuel consumption, lubrication oil and cooling water. In addition, replacing three diesel generators by one SORC generator would decrease the weight by 12 tons, and would also decrease fuel consumption by 2.1 ton/day, shrinking the heat exchangers size, specific fuel consumption was decreased by 61 g/kW-h. Finally, the wasted heat of the main engine will decrease by 18%. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.