该代码通过一系列的迭代循环在设备的各个方面决定着流体的热物性条件（因此， 在考虑工作条件时的每个部件的性能）。每个周期从其相应变量的暂定值开始，并在质 量和能量平衡的基础上确定正确的最终值。 论文网

此代码所使用的物理和热力学关系与先前所描述的设计代码所使用的相同。然而， 在这个“非设计工况”的代码中，方程的未知数和已知项之间的关系现在几乎总是相反。 为了更好的理解这段代码的功能，读者可以参考该报告 16 中流程图。 Abstract In this article, some configurations of waste heat recovery systems are described, analysed and compared, in order to find the optimal plant layout。 Starting from the availability of performance data of a two-stroke diesel engine, adopted for the propulsion plant of a crude oil tanker ship, the authors examined different solutions for the waste heat recovery from the diesel engine exhaust gas ensuring the best fulfilment of the vessel needs in terms of mechanical, electric and thermal energies。 The considered waste heat recovery systems can adopt either steam turbine and gas turbine or simply steam turbine for power generation。 As regards the steam plant, two basic layouts are considered, optimized and com- pared: the first plant scheme is a typical steam plant currently adopted for waste heat recovery purposes and the second one is a solution proposed by the authors。 Considering the different options, in this article, four different system layouts, applied to the mentioned diesel engine, are singly optimized and compared between them in order to find the most suit- able plant and the steam cycle parameters that provide its best operation at the engine normal continuous rating。 The performance of the optimized waste heat recovery systems is evaluated also by comparing them under off-design engine load conditions, in the engine power range between 50% and 100% of its maximum continuous rating。

KeywordsMarine propulsion, heat recovery, simulation

Date received: 7 January 2014; accepted: 31 March 2014

Introduction In recent years, rising prices of marine fuels and the growing attention of the international community to environmental issues have promoted the research of more and more efficient methods of energy conversion。 Presently, as known, the engine type most used for propulsion and electricity generation on board is the diesel engine (DE), whose efficiency is about 50% for the two-stroke engine and slightly lower for the four- stroke one。 As a consequence of that, a considerable

amount of thermal energy is wasted to the ambient。

An increase in the energy conversion efficiency of these types of engines can be achieved by recovering part of this discharged thermal energy to satisfy part of the ship mechanical, thermal and/or electric power requirements。

As observed in Theotokatos and Livanos,1 an exam-

ple of wasted energy is the energy lost in the exhaust gas of main and auxiliary DEs of the ship, representing about 25% of the chemical energy delivered to the engine by the fuel or, equivalently, about 40%–60%  of

the engine produced power。 Moreover, the temperature of the exhaust gas discharged from these engines is high enough for techno-economically efficient energy recov- ery。 In the literature, some waste heat recovery (WHR) installations fed by DE exhaust gases are proposed and discussed。1–13 In particular, simple pressure systems1 or more complicated double-pressure systems2,3 are con- sidered with the aim to reduce fuel consumption and CO2 emissions, but other contributions4,5 are more addressed to theoretical aspects of cogeneration sys- tems for ships。 In some studies,6–9 more complex instal- lations are designed comprising an exhaust gas turbine (EGT) in addition to the WHR steam turbine (ST)。 A part  of  the  cited  references10–12   is  addressed  to   the