09:00
Parallel Session: Prototypes and Experiments
Chair: Jaakko Larjola
09:00
20 mins
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DEVELOPMENT OF A WASTE HEAT RECOVERY ORC PROTOTYPE USING AN OIL-FREE SCROLL EXPANDER
Sébastien Declaye, Sylvain Quoilin, Vincent Lemort
Abstract: The world is facing a historical increase in energy demand and energy consumption. As consequence the conventional fossil fuels are depleting faster with an inherent pollution causing sever damages to our environment. Renewable energy sources are considered as a solution to both environmental issue and energy demand. At the same time a lot of waste heat is witnessed in processes in industries. Our objective is to contribute to the development of ORC systems, that appear to us as a good solution to recover this wasted heat.
In such waste heat applications, depending on the heat source flow rate and temperature, electrical power output can be as low as a few kilowatts. In this power range, there is no cost effective expansion machine available on the market. On existing prototypes, expansion devices are usually retrofitted volumetric compressors originally designed for refrigeration or air compression applications. Air compressors have the advantage to handle higher inlet temperature but tightness is often an issue in ORC application since the fluids used have a non negligible environmental impact.
This paper presents the development of a small-scale WHR ORC unit at the Thermodynamic Laboratory of the University of Liège: the prototype uses a scroll expander, plate heat exchangers, a diaphragm piston pump and a liquid receiver. This system was tested with different working fluids (R123, R245fa and HFE7000) and a thermal efficiency close to 8% was obtained for a net output power of about 2 kWe.
The specificity of the proposed prototype is the absence of lubrication: in order to avoid oil circulation in the ORC loop, an oil-free scroll expander is developed. This expander is originally an air scroll compressor that was modified using a magnetic coupling to ensure tightness. The experimental results highlight the good efficiency of the device, despite a relatively high internal leakage due to absence of lubrication. The necessity of using magnetic coupling is also justified by comparing the experimental results with previous ones obtained using mechanical sealing.
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09:20
20 mins
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INFLUENCE OF MOLECULAR COMPLEXITY ON NOZZLE DESIGN FOR AN ORGANIC VAPOR WIND TUNNEL
Alberto Guardone, Andrea Spinelli, Vincent Vandecauter, Vincenzo Dossena
Abstract: A novel test rig for investigating the real-gas behavior of organic fluids operating at subsonic-supersonic speed in the proximity of the liquid-vapor critical point and the saturation curve has been constructed at the Politecnico di Milano, Italy. This is a blow-down facility in which an organic vapor is expanded from a high-pressure reservoir kept at controlled super-heated or super-critical conditions into a low-pressure reservoir, where the vapor is condensed and pumped back into the high-pressure reservoir.
Expansion to supersonic speeds occurs through a converging-diverging Laval nozzle.
A standard design technique based on the Method Of Characteristics (MOC) is used to design of the supersonic portion of the nozzle [1]. The transonic potential equation is solved by means of the approximate solution procedure of Sauer [2], which is applicable to real-gas flow without significant modifications, to compute the transonic flow at the nozzle throat. The transonic flow solution provides the initial data curve for the MOC. The expansion through the divergent section to the desired exit pressure is achieved via an initial circular profile followed by the so-called turning region, in which the nozzle upper wall geometry is determined by imposing the conservation of the mass flow at each section. The resulting flow at the nozzle exit is with uniform Mach number and parallel to the x axis. Further details on the design procedure, including comparisons with available ideal gas solutions, are given in [3].
Differently from the well-known ideal-gas results, the shape of the supersonic expander - the divergent section of the nozzle - depends on the reservoir or total flow conditions and therefore diverse designs are obtained for a given exit Mach number depending on the relative location of the initial state in the volume-pressure thermodynamic plane with respect to the liquid-vapor saturation curve. For flow states close to the liquid-vapor saturation curve and critical point, the nozzle length and height are larger than the corresponding ideal gas designs. Four different operating conditions for siloxane fluid MDM (Octamethyl-trisiloxane) and refrigerant R245fa are considered and the resulting nozzle designs are thoroughly discussed.
The effect of the molecular complexity of the fluid on the final design is throughly investigated for the cyclic siloxanes D4 (Octamethyl-cyclotetrasiloxane), D5 (Decamethyl-cyclopentasiloxane) and D6 (Dodecamethyl-cyclohexasiloxane) and for the linear ones MM (Hexamethyl-disiloxane), MDM, MD2M (Decamethyl-tetrasiloxane), MD3M (Dodecamethyl-pentasiloxane).
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09:40
20 mins
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ORC MICRO-POWER PLANT FOR COMBINED HEAT AND ELECTRIC POWER GENERATION
Krzysztof Kosowski
Abstract: ABSTRACT
The micro steam turbines have found their applications in the micro-power plants, including the poly-generation power systems and the combined gas-steam installations. Apart from the traditional medium, i.e. water vapour, also low-boiling media, as a rule, organic ones, are applied. On the market the co-generation systems working with organic media are already available, however only a few examples can be found of ORC installations of output power smaller than 100kW. The problems faced by designers of such turbines are associated with very small volume flow rate of working medium which leads to small values of blades’ height and high values of rotor speed, up to hundred thousand rpm or more. The co-generative micro-power plant with the HFE7100 as a working medium was designed and built for experimental investigations. The values of the main cycle parameters were as follows:
- heat output: 20 kW,
- electric output: 3kW
- medium mass flow rate: 0.017kg/s,
- the pressure at turbine inlet: 1200kPa,
- the temperature at turbine inlet: 162oC,
- the pressure behind the turbine: 119kPa (the saturation temperature equal to about 65 oC).
In PART A a description of the experimental power plant is presented. Special attention is paid to the advanced design of the main elements of the power plant: a boiler, heat exchangers, a pomp and a turbine generator. The results of the preliminary experimental research are given and analysed. In PART B a design of a multi-stage micro-turbine with partial admission of all the stages is described in detail and the results of the particular experimental investigations and numerical calculations are shown, followed by an appropriate discussion and conclusions. It is worth emphasising that the turbine efficiency is higher than 80%.
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10:00
20 mins
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ORC POWER PLANTS WITH HERMETIC TURBOGENERATORS: FIRST PRACTICAL EXPERIENCES
Aleksandra Borsukiewicz-Gozdur, Pawel Hanausek, Wojciech Klonowicz
Abstract: The power plants based on the Organic Rankine Cycle find recently numerous
applications in utilization of the low temperature heat sources. The first in Poland
experimental plant of that type was built and put into operation at the West Pomeranian
University of Technology in Szczecin in 2008. In that plant, a high speed ORC turbine was
driving a small centrifugal air compressor. Problems were encountered with sealing system of
the turbine shaft and, in consequence, with the leakage of the organic fluid. Therefore, for the
next solutions of the ORC power plants that should generate electricity, several concepts of
the hermetic turbogenerators were invented. In those concepts the ORC turbine and the
electric generator are enclosed in a common hermetic casing, and the electric generator is
cooled with the turbine outlet vapour.
First small ORC power plant incorporating the invented hermetic turbogenerator and a
commercially available hermetic organic liquid pump was then put into operation in 2010.
This was preceded by long lasting endurance tests for the insulation materials of the electric
generator, during which those materials were immersed in the vapour of the organic fluid
selected to work in the ORC power plant. The successful operation of the entirely hermetic
ORC power plant will be reported and presented. Additionally, several aspects of the design
and applications of the hermetic turbogenerators will be discussed.
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10:20
20 mins
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A SMALL SCALE TURBINE FOR THE ORGANIC RANKINE CYCLE
Alexej Belozerov, Wolfgang Heddrich, Ralf Rieger, Yorck Leschber
Abstract: see attached file
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10:40
20 mins
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EXPERIMENT OF PUMPLESS ORGANIC RANKINE-TYPE CYCLE FOR LOW-TEMPERATURE WASTE HEAT RECOVERY
Noboru Yamada, Masataka Watanabe, Akira Hoshi
Abstract: Among the components of the conventional organic Rankine cycle (ORC) for the low-temperature waste heat recovery, the working fluid pump tends to cause a critical decline in the net cycle efficiency. A pump’s efficiency drops sharply under off-design conditions, such as high or low pressures at the inlet/outlet and mass flow rates that are greater or lesser than the designed value. This trend is pronounced in systems whose power output is less than 10 kW and whose hot-source temperature level is less than 200C (473 K). Furthermore, the working fluid pump limits the compactness of the system arrangement because the pump must be placed at a level lower than that of the condenser (i.e., a net positive suction head of the pump) in order to maintain sufficient inlet pressure to prevent the occurrence of cavitation, which results in considerable power consumption by the pump. These adverse effects of the working fluid pump appear in any ORC system with a small power output and a low-temperature hot source whose temperature level and heat quantity vary during operation. It should be noted that heat obtained from renewable energy sources, such as solar thermal energy, waste heat from factory processes, and heat obtained from the automobile engine have similar characteristics;
To overcome the abovementioned problems, one of the authors have attempted to develop “pumpless” ORC system [1]. The pumpless ORC mainly consists of an expander, two heat exchangers, and switching valves for the expander and heat exchangers. Instead of using a working fluid pump, the switching valves method (SVM) is employed to control the cycle. The SVM makes each heat exchanger switch between functioning as an evaporator and functioning as a condenser. In this arrangement, the working fluid flows back and forth between the two heat exchangers without a working fluid pump. Therefore, this cycle does not involve problems caused by a pump. The first experimental result with an displacement-type expander was carried out to clarify the feasibility of pumpless ORC. The experimental results shows that the proposed cycle works and produces power. Time-varying characteristics of the proposed cycle will be also shown and discussed.
REFERENCES
[1] N.Yamada, T.Minami, M.N.A Mohamad, Fundamental experiment of pumpless Rankine-type cycle for low-temperature heat recovery, Energy, Vol.36, pp.1010-1017, (2011).
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