Abstract
The increasing of fuel prices and global energy demand and enactment of new restrictive emissions regulations require more efficient and environmentally friendly engines to be designed. In this context, conversion of waste heat to useful energy is necessary to design more energy efficient vessel including using more efficient main engines and auxiliary engines. The aim of this study, thermodynamic characteristic of recovery of a ship's main engine waste heat is determined parametrically for waste heat recovery system (WHRS). Naturally, heat exchangers are used for waste heat recovery. Because of that reason, firstly shell–and–tube heat exchanger will be investigated parametrically. In order to make a more accurate calculation, it is important to reflect the pressure and enthalpy variations in the heat exchanger to the heat transfer calculations. After that the Transcritical Organic Rankine Cycle (TORC), which is recommended by many authors for the recovery of waste heat sources at low and medium temperatures, will be examined parametrically. The results show that increasing the number of pipes in the heat exchanger at a certain value may result in a decrease in system performance parameters that is The Net Power and Thermal Efficiency due to decreasing velocity of the mass flow in tubes. Moreover, The Net Power and Thermal Efficiency curves behaved differently with variable mass flow rate. Therefore, we will define performance parameter being important for WHRS.
Highlights
The increasing of fuel prices and global energy demand and enactment of new restrictive emissions regulations require more efficient and environmentally friendly engines to be designed
Different kind of technologies exist such as Subcritical and Transcritical Organic Rankine Cycles that are suitable to convert the waste heat to useful power
The transcritical organic Rankine cycles are used more than subcritical systems due to their lower loses and higher performance
Summary
The increasing of fuel prices and global energy demand and enactment of new restrictive emissions regulations require more efficient and environmentally friendly engines to be designed. R1234yf, widely used in ORC, was accepted as working fluid to convert waste heat to the work due to its thermophysical properties, its very low global warming potential and its zero ozone depletion potential [36] and Wartsila 4L20 type marine diesel engine which is fully compliant with the IMO Tier II exhaust emissions regulations, data were used for calculation of the waste heat capacity [37]. The effects of flow rates of working fluid and main engine exhaust gas, isentropic efficiencies of pump and turbine and the number and the length of heat pipes on The Thermal Efficiency and power generation of waste heat used transcritical organic Rankine cycle are investigated. The shell side Nusselt correlation and pressure loss correlation are given in (10 – 11) [39], 0,36
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