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09:00   System design and optimization II
Chair: Prof. Jos van Buijtenen
20 mins
Santiago Suarez de la Fuente, Alistair Greig
Abstract: The predictions of CO2 atmospheric concentrations by 2050 are between 480 ppm to 550 ppm with increases of temperature from 0.5 to 2.5°C; shipping contributes in 3.3% of the total human CO2 emissions (1). It is therefore important to start generating green and intelligent solutions based on new strategies and technologies, which will help to follow a green agenda in shipping. The biggest source of energy losses in a ship is found in the propulsion system (1). This study focuses on analyzing and working with the concept of heat management for waste heat energy from the exhaust gas. Using waste heat recovery systems to make shipping more efficient represents a good area of opportunity from an academic and industrial point of view. Organic Rankine Cycles have been applied in land based systems before, showing improvements in performance when compared with traditional Rankine cycle (2–4). However, their use in ships has been limited, offering an important area of opportunity to be considered (5,6). The proposed ORC waste heat recovery system is modelled with a typical ship main propulsion, slow speed diesel engine installed after the turbo compressors in the exhaust gas system. The energy recovered from the exhaust gas flow will be transformed via the thermodynamic cycle into electricity which will help to cover the ship demand. By doing this there will be a fuel consumption reduction, hence decreasing the emissions of CO2 and other greenhouse gases. A code generated explicitly for this purpose will show the behaviour of different working fluids appropriate for the chosen scenario at each stage of the thermodynamic cycle. With this it is possible to demonstrate that a simple ORC can be more effective than a water based Rankine cycle, challenging previous research and common standards for the industry. This research project will provide new knowledge on thermodynamics and waste heat recovery systems with a simulation model to enable the use of accurate information to experiment for ship design and identify new areas of opportunity and improvement. The presentation will include the relevant literature that anchors the research, its strengths, weaknesses and gaps. Then, it shows a quantitative comparison that uses the first and second thermodynamic laws and pinch point analysis. With those tools a consistent and unbiased decision-making model is elaborated for ships operating under different and changing conditions. That will allow identification of areas of improvement of thermodynamic technologies. Benefits of this research are threefold. From the academic perspective it increases the knowledge on thermodynamics and behaviour of waste heat recovery systems in challenging environments. From the industrial point of view it will find areas of opportunity for ship design attractive to the consumer and in a cost efficient basis. For the society in general, it represents a possibility of environmental friendly transportation that helps to reduce CO2 emissions.
20 mins
Sotirios Karellas, Kyriaki Zourou, Konstantinos Braimakis, Emmanuel Kakaras
Abstract: Container glass manufacturing is a high temperature, energy-intensive process and rejects to the atmosphere high temperature exhaust gases. Waste heat recovery systems can be implemented in the process to utilize the rich energy content of the flue gases from industrial processes and contribute to the increase of the efficiency and also to significant abatement of the emissions. The aim of this paper is to examine and compare two Waste Heat Recovery systems for the glass industry. Namely a water-steam Rankine cycle and an Organic Rankine Cycle (ORC) were designed for the case study of Yioula Glassworks S.A. The temperature of the exhaust gases is 450-500oC leading to a waste heat of around 2,5 ΜWth, while the annual CO2 emissions from natural gas combustion in the furnace reaches the amount of 30467 tonnes per year. With the implementation of an ORC system, it is estimated that more than 600kWe can be recovered. The ORC system has been designed and dimensioned for several working fluids (R245fa, isopentane, neopentane, pentane, toluene, MM, MDM) focusing on the increase of the efficiency and the decrease of the investment costs. The waste heat recovery systems were compared energetically, exergetically and also from an economic perspective. Furthermore, the CO2 avoidance benefits were precisely calculated. Finally an economic feasibility analysis has been conducted in order to evaluate the viability of the implementation of the abovementioned applications. WHR installations in glass industry can reduce significantly the energy consumption operating costs, thus being an attractive investment which enhances the environmental policy of the industry according to the BAT.
20 mins
Steven Lecompte, Henk Huisseune, Martijn van den Broek, Michel De Paepe
Abstract: Combined heat and power (CHP) systems are able to decrease the total energy use of primary energy sources. In the CHP system studied, internal combustion engines produce electricity and the hot engine cooling water is used for building heating. However, there is still waste heat left which can be fed to an Organic Rankine Cycle (ORC) to produce electricity. The objective of this study is to develop a methodology to design an economically optimal ORC system, taking into account the variable load for heating and the change in ambient temperature during a year. Also the auxiliary equipment such as pumps and fans are considered. A thermodynamic steady-state part-load model is developed to simulate the changing behaviour hour-by-hour of the complete system in different operating conditions. The ORC efficiency varies strongly over a year. The methodology allows selecting the optimal size of the heat exchangers (condenser and evaporator), the optimal mass flow rates and the maximal power of fans and pumps needed for the considered application.