Imperial College London

ProfessorChristosMarkides

Faculty of EngineeringDepartment of Chemical Engineering

Professor of Clean Energy Technologies
 
 
 
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Contact

 

+44 (0)20 7594 1601c.markides Website

 
 
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Location

 

404ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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284 results found

Pantaleo, Rotolo G, De Palma P, Amirante R, Oyewunmi OA, Chatzopoulou, Markides C, Simpson Met al., Thermo-economic optimization of small-scale ORC systems for heat recovery from natural gas internal combustion engines for stationary power generation, 4th Annual Engine ORC Consortium Workshop for the Automotive and Stationary Engine Industries

Conference paper

Ibarra R, Matar OK, Markides CN, 2017, Flow structures in low-inclination stratified oil-water pipe-flows using laser-based diagnostic techniques, International Conference on Multiphase Production, Publisher: BHR Group, Pages: 71-85

In this work, a novel two-line laser-based diagnostic measurement technique was developed and applied to obtain combined space- and time-resolved phase and velocity information in low-inclination upward (<+5°) stratified flows of oil (Exxsol D140) and water. The strength of this technique is in enabling direct measurements in the non-refractive-index-matched fluids of interest, as opposed to substitute (optically matched) fluids whose properties may be less representative of those in real field-applications. The experimental test-section consisted of a 32-mm internal diameter pipe with a total length of 8.5 m. Results reveal interesting interactions between the co-flowing liquid phases. The velocity gradients at the interface are enhanced at high pipe inclinations for upward flows as the oil and water velocities increase and decrease, respectively. This also has a direct effect on the velocity fluctuations (quantified through their rms) and on the interfacial instabilities, which in turn affect the local velocity distributions in both phases.

Conference paper

Pantaleo AM, Camporeale SM, Miliozzi A, Russo V, Mugnozza GS, Markides CN, Shah Net al., 2017, Thermo-economic assessment of an externally fired hybrid CSP/biomass gas turbine and organic Rankine combined cycle, 8th International Conference on Applied Energy (ICAE), Publisher: Elsevier, Pages: 174-181, ISSN: 1876-6102

This paper focuses on the thermo-economic analysis of a hybrid solar-biomass CHP combined cycle composed by a 1.3-MW externally fired gas-turbine (EFGT) and a bottoming organic Rankine cycle (ORC) plant. The primary thermal energy input is provided by a hybrid concentrating solar power (CSP) collector-array coupled to a biomass boiler. The CSP collector-array is based on parabolic-trough concentrators (PTCs) with molten salts as the heat transfer fluid (HTF) upstream of a fluidized-bed furnace for direct biomass combustion. Thermal-energy storage (TES) with two molten-salt tanks (one cold and one hot) is considered, as a means to reducing the variations in the plant's operating conditions and increasing the plant's capacity factor. On the basis of the results of the thermodynamic simulations, upfront and operational costs assessments, and considering an Italian energy policy scenario, the global energy conversion efficiency and investment profitability are estimated for 2 different sizes of CSP arrays and biomass furnaces. The results indicate the low economic profitability of CSP in comparison to only biomass CHP, because of the high investment costs, which are not compensated by higher electricity sales revenues.

Conference paper

Pantaleo AM, Camporeale SM, Markides CN, Mugnozza GS, Shah Net al., 2017, Energy performance and thermo-economic assessment of a microturbine-based dual-fuel gas-biomass trigeneration system, 8th International Conference on Applied Energy (ICAE), Publisher: Elsevier, Pages: 764-772, ISSN: 1876-6102

The focus of this paper is on the energy performance and thermo-economic assessment of a small scale (100 kWe) combined cooling, heat and power (CCHP) plant serving a tertiary/residential energy demand fired by natural gas and solid biomass. The plant is based on a modified regenerative micro gas-turbine (MGT), where compressed air exiting the recuperator is externally heated by the hot gases produced in a biomass furnace. The flue gases after the recuperator flow through a heat recovery system (HRS), producing domestic hot water (DHW) at 90 °C, space heating (SH), and also chilled water (CW) by means of an absorption chiller (AC). Different biomass/natural gas ratios and an aggregate of residential end-users in cold, average and mild climate conditions are compared in the thermo-economic assessment, in order to assess the trade-offs between: (i) the lower energy conversion efficiency and higher investment cost when increasing the biomass input rate; (ii) the higher primary energy savings and revenues from feed-in tariffs available for biomass electricity exported into the grid; and (iii) the improved energy performance, sales revenue and higher investment and operational costs of trigeneration. The results allow for a comparison of the energy performance and investment profitability of the selected system configuration, as a function of the heating/cooling demand intensity, and report a global energy efficiency in the range of 25-45%, and IRR in the range of 15-20% assuming the Italian subsidy framework.

Conference paper

Pantaleo AM, Camporeale SM, Miliozzi A, Russo V, Shah N, Markides CMet al., 2017, Novel hybrid CSP-biomass CHP for flexible generation: thermo-economic analysis and profitability assessment, Applied Energy, Vol: 204, Pages: 994-1006, ISSN: 1872-9118

This paper focuses on the thermo-economic analysis of a 2.1-MWe and 960 kWt hybrid solar-biomass combined heat and power (CHP) system composed of a 1.4-MWe Externally Fired Gas-Turbine (EFGT) and a 0.7-MWe bottoming Organic Rankine Cycle (ORC) power plant. The primary thermal energy input is provided by a hybrid Concentrating Solar Power (CSP) collector array covering a total ground area of 22,000–32,000 m2, coupled to a biomass boiler. The CSP collector array is based on parabolic-trough concentrators (PTCs) with molten salts as the heat transfer fluid (HTF), upstream of a 4.5–9.1 MWt fluidized-bed furnace for direct biomass combustion. In addition, two molten-salt tanks are considered that provide 4.8–18 MWh (corresponding to 1.3–5.0 h) of Thermal Energy Storage (TES), as a means of reducing the variations in the plant’s operating conditions, increasing the plant’s capacity factor and total operating hours (from 5500–6000 to 8000 h per year). On the basis of the results of the thermodynamic simulations, upfront and operational costs assessments, and considering an Italian energy policy scenario (feed-in tariffs, or FiTs, for renewable electricity), the global energy conversion efficiency and investment profitability of this plant are estimated for different sizes of CSP and biomass furnaces, different operation strategies (baseload and modulating) and cogenerative vs. electricity-only system configurations. Upfront costs in the range 4.3–9.5 MEur are reported, with operating costs in the range 1.5–2.3 MEur annually. Levelized costs of energy from around 100 Eur/MWh to above 220 Eur/MWh are found, along with net present values (NPVs) from close to 13,000 to −3000 kEur and internal rates of return (IRRs) from 30% down to almost zero when prioritizing electrical power generation (i.e., not in cogenerative mode). In all cases the economic viability of the systems deteriorate for larger CSP section sizes. The

Journal article

Mariaud A, Acha S, Ekins-Daukes N, Shah N, Markides CNet al., 2017, Integrated optimisation of photovoltaic and battery storage systems for UK commercial buildings, Applied Energy, Vol: 199, Pages: 466-478, ISSN: 1872-9118

Decarbonising the built environment cost-effectively is a complex challenge public and private organisations are facing in their effort to tackle climate change. In this context, this work presents an integrated Technology Selection and Operation (TSO) optimisation model for distributed energy systems in commercial buildings. The purpose of the model is to simultaneously optimise the selection, capacity and operation of photovoltaic (PV) and battery systems; serving as a decision support framework for assessing technology investments. A steady-state mixed-integer linear programming (MILP) approach is employed to formulate the optimisation problem. The virtue of the TSO model comes from employing granular state-of-the-art datasets such as half-hourly electricity demands and prices, irradiance levels from weather stations, and technology databases; while also considering building specific attributes. Investment revenues are obtained from reducing grid electricity costs and providing fast-frequency response (FFR) ancillary services. A case study of a distribution centre in London, UK is showcased with the goal to identify which technologies can minimise total energy costs against a conventional system setup serving as a benchmark. Results indicate the best technology configuration is a combination of lithium-ion batteries and mono-crystalline silicon PVs worth a total investment of £1.72 M. Due to the available space in the facility, the preferred PV capacity is 1.76 MW, while the battery system has a 1.06 MW power capacity and a 1.56 MWh energy capacity. Although PV performance varies across seasons, the solution indicates almost 30% of the energy used on-site can be supplied by PVs while achieving a carbon reduction of 26%. Nonetheless, PV and battery systems seem to be a questionable investment as the proposed solution has an 8-year payback, despite a 5-year NPV savings of £300k, implying there is still a performance gap for such systems to be massively

Journal article

Lecompte S, Oyewunmi OA, Markides C, Lazova M, Kaya A, van den Broek M, De Paepe Met al., 2017, Case study of an organic Rankine cycle (ORC) for waste heat recovery from an electric arc furnace (EAF), Energies, Vol: 10, ISSN: 1996-1073

The organic Rankine cycle (ORC) is a mature technology for the conversion of waste heat to electricity. Although many energy intensive industries could benefit significantly from the integration of ORC technology, its current adoption rate is limited. One important reason for this arises from the difficulty of prospective investors and end-users to recognize and, ultimately, realise the potential energy savings from such deployment. In recent years, electric arc furnaces (EAF) have been identified as particularly interesting candidates for the implementation of waste heat recovery projects. Therefore, in this work, the integration of an ORC system into a 100 MWe EAF is investigated. The effect of evaluations based on averaged heat profiles, a steam buffer and optimized ORC architectures is investigated. The results show that it is crucial to take into account the heat profile variations for the typical batch process of an EAF. An optimized subcritical ORC system is found capable of generating a net electrical output of 752 kWe with a steam buffer working at 25 bar. If combined heating is considered, the ORC system can be optimized to generate 521 kWe of electricity, while also delivering 4.52 MW of heat. Finally, an increased power output (by 26% with combined heating, and by 39% without combined heating) can be achieved by using high temperature thermal oil for buffering instead of a steam loop; however, the use of thermal oil in these applications has been until now typically discouraged due to flammability concerns.

Journal article

Lecompte S, Oyewunmi OA, Markides CN, Lazova M, Kaya A, Ameel B, van den Broek M, De Paepe Met al., Potential of organic Rankine Cycles (ORC) for waste heat recovery on an electric arc furnace (EAF), 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT2017), Publisher: ICHMT

The organic Rankine cycle (ORC) is a mature technology to convert low temperature waste heat to electricity. While several energy intensive industries could benefit from the integration of an ORC, their adoption rate is rather low. One important reason is that the prospective end-users find it difficult to recognize and realise the possible energy savings. In more recent years, the electric arc furnaces (EAF) are considered as a major candidate for waste heat recovery. Therefore, in this work, the integration of an ORC coupled to a100 MWe EAF is investigated. The effect of working with averaged heat profiles, a steam buffer and optimized ORC architectures is investigated. The results show that it is crucial to take into account the heat profile variations for the typical batch process of an EAF. An optimized subcritical ORC(SCORC) can generate an electricity output of 752 kWe with a steam buffer working at 25 bar. However, the use of a steam buffer also impacts the heat transfer to the ORC. A reduction up to 61.5% in net power output is possible due to the additional isothermal plateau of the steam

Conference paper

White MT, Oyewunmi OA, Haslam A, Markides Cet al., Exploring optimal working fluids and cycle architectures for organic Rankine cycle systems using advanced computer-aided molecular design methodologies, 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT2017), Publisher: ICHMT

The combination of computer-aided molecular design(CAMD) with an organic Rankine cycle (ORC) power-systemmodel presents a powerful methodology that facilitates an in-tegrated approach to simultaneous working-fluid design andpower-system thermodynamic or thermoeconomic optimisation.Existing CAMD-ORC models have been focussed on simplesubcritical, non-recuperated ORC systems. The current workintroduces partially evaporated or trilateral cycles, recuperatedcycles and working-fluid mixtures into the ORC power-systemmodel, which to the best knowledge of the authors has not beenpreviously attempted. A necessary feature of a CAMD-ORCmodel is the use of a mixed-integer non-linear programming(MINLP) optimiser to simultaneously optimise integer working-fluid variables and continuous thermodynamic cycle and eco-nomic variables. In this paper, this feature is exploited by in-troducing binary optimisation variables to describe the cycle lay-out, thus enabling the cycle architecture to be optimised along-side the working fluid and system conditions. After describingthe models for the alternative cycles, the optimisation problemis completed for a defined heat source, considering hydrocar-bon working fluids. Two specific case studies are considered,in which the power output from the ORC system is maximised.These differ in the treatment of the minimum heat-source outlettemperature, which is unconstrained in the first case study, butconstrained in the second. This is done to replicate scenariossuch as a combined heat and power (CHP) plant, or applicationswhere condensation of the waste-heat stream must be avoided.In both cases it is found that a working-fluid mixture can per-form better than a pure working fluid. Furthermore, it is foundthat partially-evaporated and recuperated cycles are optimal forthe unconstrained and constrained case studies respectively.

Conference paper

Markides C, Tunnicliffe H, 2017, A concentrated effort, TCE The Chemical Engineer, Pages: 38-41, ISSN: 0302-0797

Concentrated solar power (CSP) has received less attention and funding compared to its more popular solar power rival, especially since photovoltaic (PV) technology is more viable in widespread smaller-scale applications. CSP has the ability to store thermal energy unlike conventional photovoltaics. CSP power stations that has storage facilities can utilize heat to generate power even when the sun is out. According to Christos Markides, reader in clean energy processes at the Department of Chemical Engineering at Imperial College London, UK, a silicon PV panel has an efficiency, in terms of solar energy transformed into electricity, or about 15%-20%, while CSP technologies will have efficiencies close to 25%. Markides and his team are researching on a slightly different CSP concept, in which H2O that drives the turbine generation cycle is also utilized as the heat transfer fluid that is sent to the parabolic collectors, rather than using an intermediate thermal oil, a process called direct steam generation. Markides is leading a five-year collaborative CSP research project with African universities - the University of Pretoria in South Africa, the University of Lagos in Nigeria, and the University of Mauritius. The project is a program grant funded by the UK Department for International Development.

Journal article

Ramos Cabal A, Guarracino I, Mellor A, Alonso Álvarez D, Childs P, Ekins Daukes N, Markides CNet al., 2017, Solar-Thermal and Hybrid Photovoltaic-Thermal Systems for Renewable Heating, Publisher: Grantham Institute, Imperial College London

Headlines Heat constitutes about half of total global energy demand. Solar heat offers key advantages over other renewable sources for meeting this demand through distributed, integrated systems. Solar heat is a mature sustainable energy technology capable of mass deployment. There is significant scope for increasing the installed solar heat capacity in Europe. Only a few European countries are close to reaching the EU target of 1 m2 of solar-thermal installations per person. One key challenge for the further development of the solar-thermal market arises from issues related to the intermittency of the solar resource, and the requirement for storage and/or backup systems. The former increases investment costs and limits adaptability. An analysis of EU countries with good market development, suggests that obligation schemes are the best policy option for maximising installations. These do not present a direct cost to the public budget, and determine the growth of the local industry in the long term. Solar-thermal collectors can be combined with photovoltaic (PV) modules to produce hybrid PV-thermal (PV-T) collectors. These can deliver both heat and electricity simultaneously from the same installed area and at a higher overall efficiency compared to individual solar-thermal and PV panels installed separately. Hybrid PV-T technology provides a particularly promising solution when roof space is limited or when heat and electricity are required at the same time.

Report

White MT, Oyewunmi OO, Haslam AJ, Markides CNet al., 2017, Industrial waste-heat recovery through integrated computer-aided working-fluid and ORC system optimisation using SAFT-γ Mie, Energy Conversion and Management, Vol: 150, Pages: 851-869, ISSN: 0196-8904

A mixed-integer non-linear programming optimisation framework is formulated and developed that combines a molecular-based, group-contribution equation of state, SAFT-γγ Mie, with a thermodynamic description of an organic Rankine cycle (ORC) power system. In this framework, a set of working fluids is described by its constituent functional groups (e.g., since we are focussing here on hydrocarbons: single bondCH3, single bondCH2single bond, etc. ), and integer optimisation variables are introduced in the description the working-fluid structure. Molecular feasibility constraints are then defined to ensure all feasible working-fluid candidates can be found. This optimisation framework facilitates combining the computer-aided molecular design of the working fluid with the power-system optimisation into a single framework, thus removing subjective and pre-emptive screening criteria, and simultaneously moving towards the next generation of tailored working fluids and optimised systems for waste-heat recovery applications. SAFT-γγ Mie has not been previously employed in such a framework. The optimisation framework, which is based here on hydrocarbon functional groups, is first validated against an alternative formulation that uses (pseudo-experimental) thermodynamic property predictions from REFPROP, and against an optimisation study taken from the literature. The framework is then applied to three industrial waste-heat recovery applications. It is found that simple molecules, such as propane and propene, are the optimal ORC working fluids for a low-grade (150 °C) heat source, whilst molecules with increasing molecular complexity are favoured at higher temperatures. Specifically, 2-alkenes emerge as the optimal working fluids for medium- and higher-grade heat-sources in the 250–350 °C temperature range. Ultimately, the results demonstrate the potential of this framework to drive the search for the next generation of ORC systems, and to

Journal article

Oyewunmi OA, white MT, Chatzopoulou M, Haslam A, Markideset al., Integrated Computer-Aided Working-Fluid Design and Power System Optimisation: Beyond Thermodynamic Modelling, 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017), Publisher: ECOS-2017

Improvements in the thermal and economic performance of organic Rankine cycle (ORC) systems are requiredbefore the technology can be successfully implemented across a range of applications. The integration ofcomputer-aided molecular design (CAMD) with a process model of the ORC facilitates the combinedoptimisation of the working-fluid and the power system in a single modelling framework, which should enablesignificant improvements in the thermodynamic performance of the system. However, to investigate theeconomic performance of ORC systems it is necessary to develop component sizing models. Currently, thegroup-contribution equations of state used within CAMD, which determine the thermodynamic properties of aworking-fluid based on the functional groups from which it is composed, only derive the thermodynamicproperties of the working-fluid. Therefore, these do not allow critical components such as the evaporator andcondenser to be sized. This paper extends existing CAMD-ORC thermodynamic models by implementinggroup-contribution methods for the transport properties of hydrocarbon working-fluids into the CAMD-ORCmethodology. Not only does this facilitate the sizing of the heat exchangers, but also allows estimates of systemcosts by using suitable cost correlations. After introducing the CAMD-ORC model, based on the SAFT-γ Mieequation of state, the group-contribution methods for determining transport properties are presented alongsidesuitable heat exchanger sizing models. Finally, the full CAMD-ORC model incorporating the componentmodels is applied to a relevant case study. Initially a thermodynamic optimisation is completed to optimise theworking-fluid and thermodynamic cycle, and then the component models provide meaningful insights into theeffect of the working-fluid on the system components.

Conference paper

Oyewunmi OA, Lecompte S, De Paepe M, Markideset al., Thermodynamic Optimization of Recuperative Sub- and Transcritical Organic Rankine Cycle Systems, 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017), Publisher: ECOS-2017

There is significant interest in the deployment of organic Rankine cycle (ORC) technology for waste-heatrecovery and power generation in industrial settings. This study considers ORC systems optimized formaximum power generation using a case study of an exhaust flue-gas stream at a temperature of 380 °C asthe heat source, covering over 30 working fluids and also considering the option of featuring a recuperator.Systems based on transcritical cycles are found to deliver higher power outputs than subcritical ones, withoptimal evaporation pressures that are 4-5 times the critical pressures of refrigerants and light hydrocarbons,and 1-2 times those of siloxanes and heavy hydrocarbons. For maximum power production, a recuperator isnecessary for ORC systems with constraints imposed on their evaporation and condensation pressures. Thisincludes, for example, limiting the minimum condensation pressure to atmospheric pressure to prevent subatmosphericoperation of this component, as is the case when employing heavy hydrocarbon and siloxaneworking fluids. For scenarios where such operating constraints are relaxed, the optimal cycles do not featurea recuperator, providing some capital cost savings, with some cycles showing more than three times thegenerated power than with this component, making investments in sub-atmospheric components worthwhile.

Conference paper

Ramos Cabal A, Chatzopoulou MA, Guarracino I, Freeman J, Markides CNet al., 2017, Hybrid photovoltaic-thermal solar systems for combined heating, coolingand power provision in the urban environment, Energy Conversion and Management, Vol: 150, Pages: 838-850, ISSN: 0196-8904

Solar energy can play a leading role in reducing the current reliance on fossil fuels and in increasing renewable energy integration in the built environment. Hybrid photovoltaic-thermal (PV-T) systems can reach overall efficiencies in excess of 70%, with electrical fficiencies in the range of 15-20% and thermal efficiencies of 50% or higher. In most applications, the electrical output of a hybrid PV-T system is the priority, hence the contacting fluid is used to cool the PV cells to maximise their electrical performance, which imposes a limit on the fluid's downstream use. When optimising the overall output of PV-T systems for combinedheating and cooling provision, this technology can cover more than 60% of the heating and about 50% of the cooling demands of households in the urban environment. To achieve this, PV-T systems can be coupledto heat pumps or absorption refrigeration systems as viable alternatives to vapour-compression systems. This work considers the techno-economic challenges of such systems, when aiming at a low cost per kWh of energy generation of PV-T systems for co- or tri-generation in the housing sector. First, the viability and afordability of the proposed systems are studied in ten European locations, with local weather pro files, using annually and monthly averaged solar-irradiance and energy-demand data. Based on annual simulations, Seville, Rome, Madrid and Bucharest emerge as the most promising locations from those examined, and the most efficient system confi guration involves coupling PV-T panels to water-to-water heat pumps that usethe PV-T thermal output to maximise the system's COP. Hourly resolved transient models are then defi ned in TRNSYS in order to provide detailed estimates of system performance, since it is found that the temporal resolution (e.g. hourly, daily, yearly) of the simulations strongly affects their predicted performance. The TRNSYS results indicate that PV-T systems have the potential to cover 60% of the heating

Journal article

Guarracino I, Freeman J, Markides CN, 2017, Solar heat and power with thermal energy storage in the UK, SolaStor

Solar energy has the potential to cover a high fraction of thedemand for heat and electricity in residential buildings. Fig. 1 showsthe variation in incident solar irradiation received across Europe.In London the annual solar irradiation is ~1100 kWh/m2 per year,while the typical domestic energy consumption per household is~12000 kWh/year for heating and ~4000 kWh/year for electricity.Thus the solar energy received on a rooftop of ~15 m2is enoughpotentially enough to provide the entire annual demand fordomestic energy.Our research focuses on various aspects of two solar technologiesfor the combined provision of heating and power (CHP): solarorganic Rankine cycle systems with low-to-medium temperaturesolar-thermal collectors (Figs. 2-3) and hybrid photovoltaic/thermal(PVT) systems. (Fig.4).

Poster

Taleb AI, Sapin PMC, Barfuß C, Fabris D, Markides CNet al., 2017, CFD Analysis of Thermally Induced Thermodynamic Loses in the Reciprocating Compression and Expansion of Real Gases, 1st International Seminar on Non-Ideal Compressible-Fluid Dynamics for Propulsion and Power, Publisher: IOP Publishing: Conference Series, ISSN: 1742-6588

The efficiency of expanders is of prime importance in determining the overallperformance of a variety of thermodynamic power systems, with reciprocating-piston expandersfavoured at intermediate-scales of application (typically 10–100 kW). Once the mechanical lossesin reciprocating machines are minimized (e.g. through careful valve design and operation), lossesdue to the unsteady thermal-energy exchange between the working fluid and the solid walls ofthe containing device can become the dominant loss mechanism. In this work, gas-spring devicesare investigated numerically in order to focus explicitly on the thermodynamic losses that arisedue to this unsteady heat transfer. The specific aim of the study is to investigate the behaviourof real gases in gas springs and to compare this to that of ideal gases in order to attain a betterunderstanding of the impact of real-gas effects on the thermally induced losses in reciprocatingexpanders and compressors. A CFD-model of a gas spring is developed in OpenFOAM. Threedifferent fluid models are compared: (1) an ideal-gas model with constant thermodynamicand transport properties; (2) an ideal-gas model with temperature-dependent properties; and(3) a real-gas model using the Peng-Robinson equation-of-state with temperature and pressure-dependent properties. Results indicate that, for simple, mono- and diatomic gases, like helium ornitrogen, there is a negligible difference in the pressure and temperature oscillations over a cyclebetween the ideal and real-gas models. However, when considering heavier (organic) molecules,such as propane, the ideal-gas model tends to overestimate the pressure compared to the real-gasmodel, especially if the temperature and pressure dependency of the thermodynamic propertiesis not taken into account. In fact, the ideal-gas model predicts higher pressures by as much as25% (compared to the real-gas model). Additionally, both ideal-gas models underestimate thethermall

Conference paper

White M, Sayma AI, Markides CN, 2017, Supersonic flow of non-ideal fluids in nozzles: An application of similitude theory and lessons for ORC turbine design and flexible use considering system performance, 1st International Seminar on Non-Ideal Compressible-Fluid Dynamics for Propulsion and Power (NICFD), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

White M, Oyewunmi OA, Haslam A, Markideset al., Incorporating Computer-Aided Working-Fluid Design in the System Optimisation of an Organic Rankine Cycle Using the SAFT-γ Mie Equation of State, SAFT 2017 Conference

Conference paper

Gupta A, Markides CN, An experimental study of the autoignition of polydispersed liquid-fuel droplets in a confined high-temperature turbulent coflow, 8th European Combustion Meeting

Conference paper

White MT, Oyewunmi OA, Haslam AJ, Markides CNet al., High-efficiency industrial waste-heat recovery through computer-aided integrated working-fluid and ORC system optimisation, The 4th Sustainable Thermal Energy Management International Conference (SusTEM 2017)

In this paper, we develop a mixed-integer non-linear programming optimisation framework that combines working-fluid thermodynamic property predictions from a group-contribution equation of state, SAFT- Mie, with a thermodynamic description of an organic Rankine cycle. In this model, a number of working-fluids are described by their constituent functional groups (i.e., -CH3, -CH2, etc.), and integer optimisation variables are introduced in the description of the structure of the working-fluid. This facilitates combining the computer-aided molecular design of novel working-fluids with the power system optimisation into a single framework, thus removing subjective and pre-emptive screening criteria, and simultaneously moving towards the next generation of tailored working-fluids and optimised organic Rankine cycle systems for industrial waste-heat recovery applications. The thermodynamic model is first validated against an alternative formulation that uses (pseudo-experimental) thermodynamic property predictions from REFPROP, and against an optimisation study taken from the literature. Furthermore, molecular feasibility constraints are defined and validated in order to ensure all feasible working-fluid candidates can be found. Finally, the optimisation problem is formulated using the functional groups from the hydrocarbon family, and applied to three industrial waste-heat recovery case studies. The results demonstrate the potential of this framework to drive the search for the next generation of organic Rankine cycles, and to provide meaningful insights into which working-fluids are the optimal choices for a targeted application.

Conference paper

Willich C, Markides CN, White AJ, 2017, An investigation of heat transfer losses in reciprocating devices, APPLIED THERMAL ENGINEERING, Vol: 111, Pages: 903-913, ISSN: 1359-4311

Journal article

Ramos Cabal A, Chatzopoulou MA, Guarracino I, Freeman J, Markides CNet al., Hybrid photovoltaic-thermal solar systems for combined heating, cooling and power provision in the urban environment, 4th Sustainable Thermal Energy Management International Conference (SusTEM 2017)

Conference paper

Charogiannis, Denner, van Wachem, kalliadasis, Markideset al., 2017, Detailed Hydrodynamic Characterization of Harmonically Excited Falling-Film Flows: A Combined Experimental and Computational Study, Physical Review Fluids, Vol: 2, Pages: 014002-014002, ISSN: 2469-990X

We present results from the simultaneous application of planar laser-induced uorescence (PLIF)and particle image/tracking velocimetry, complemented by direct numerical simulations, aimed atthe detailed hydrodynamic characterization of harmonically excited liquid- lm ows falling underthe action of gravity. The experimental campaign comprises four di erent aqueous-glycerol solutionscorresponding to four Kapitza numbers (Ka= 14, 85, 350, 1800), spanning the Reynolds numberrangeRe= 2:3

Journal article

Le Brun N, Charogiannis A, Hewitt GF, Markides CNet al., 2017, TACKLING COOLANT FREEZING IN GENERATION-IV MOLTEN SALT REACTORS, 25th International Conference on Nuclear Engineering, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Kheirabadi AN, Freeman J, Cabal AR, Markides CNet al., 2017, EXPERIMENTAL INVESTIGATION OF AN AMMONIA-WATER DIFFUSION-ABSORPTION REFRIGERATOR (DAR) AT PART LOAD, ASME Summer Heat Transfer Conference, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Charogiannis A, Markides CN, 2017, APPLICATION OF LASER-INDUCED FLUORESCENCE, PARTICLE VELOCIMETRY AND INFRARED THERMOGRAPHY TO HEATED FALLING-FILM FLOWS, ASME Summer Heat Transfer Conference, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Herrando M, Guarracino I, del Amo A, Zabalza I, Markides CNet al., 2017, Energy Characterization and Optimization of New Heat Recovery Configurations in Hybrid PVT Systems, 11th ISES EuroSun Conference, Publisher: INTL SOLAR ENERGY SOC, Pages: 1228-1239

Conference paper

Herrando M, Ramos A, Zabalza I, Markides CNet al., 2017, Energy performance of a solar trigeneration system based on a novel hybrid PVT panel for residential applications, Pages: 1090-1101

© 2017. The Authors. The overall aim of this work is to assess the performance of high-efficiency solar trigeneration systems based on a novel hybrid photovoltaic-thermal (PVT) collector for the provision of domestic hot water (DHW), space heating (SH), cooling and electricity to residential single-family households. To this end, a TRNSYS model is developed featuring a novel hybrid PVT panel based on a new absorber-exchanger configuration coupled via a thermal store to two alternative small-scale solar heating and cooling configurations, one based on an electrically-driven vapour-compression heat pump (PVT+HP) and one on a thermally-driven absorption refrigeration unit (PVT+AR). The energy demands of a single-family house located in three different climates, namely Seville (Spain), Rome (Italy) and Paris (France), are estimated using EnergyPlus. Hourly transient simulations of the complete systems considering real weather data and reasonable areas for collector installation (< 30 m2) are conducted over a year. The household energy demands covered by the two systems indicate that the PVT+HP configuration is the most promising for the locations of Rome and Paris, covering more than 74% the DHW demand, 100% of the space heating and cooling demands, as well as an important share of the electricity demand. Meanwhile, for Seville, the PVT+AR configuration appears as a promising alternative, covering more than 80% of the DHW, around 70% of the cooling and electricity, and 54% of the space heating demands.

Conference paper

Chatzopoulou MA, Markides CN, Modelling of advanced combined heat and power systems in building applications, 2nd Thermal and Fluid Engineering Conference TFEC2017

Conference paper

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