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See detailDynamic modeling and control strategy analysis of a micro-scale CSP plant coupled with a thermocline system for power generation
Dickes, Rémi ULiege; Desideri, Adriano ULiege; Bell, Ian ULiege et al

in Elimar, Frank; Philippe, Papillon (Eds.) Proceedings of the ISES EuroSun 2014 Conference (2014, September 17)

Concentrated solar power systems are characterized by strong transients and require proper control guidelines to operate efficiently. In this context, a dynamic model of a 5 kWe solar ORC system is ... [more ▼]

Concentrated solar power systems are characterized by strong transients and require proper control guidelines to operate efficiently. In this context, a dynamic model of a 5 kWe solar ORC system is developed in the Modelica language to investigate the possible advantages of coupling a concentrating solar power system with a thermocline packed-bed storage. The models of the solar field, the thermocline storage and the ORC unit are described and integrated in the open-source ThermoCycle library. A first regulation strategy is proposed and implemented into a controller unit. Results of a three-day simulation using real meteorological data are finally analyzed and discussed. [less ▲]

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See detailOptimization Of A Heat Pump For Satellite Cooling
Bell, Ian ULiege; Lemort, Vincent

in 15 th International Refrigeration and Air Conditioning Conference at Purdue (2014, July)

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See detailThermoCycle: A Modelica library for the simulation of thermodynamic systems
Quoilin, Sylvain ULiege; Desideri, Adriano ULiege; Wronski, Jorrit et al

in Proceedings of the 10th International Modelica Conference 2014 (2014)

This paper presents the results of an on-going project to develop ThermoCycle, an open Modelica library for the simulation of low-capacity thermodynamic cycles and thermal systems. Special attention is ... [more ▼]

This paper presents the results of an on-going project to develop ThermoCycle, an open Modelica library for the simulation of low-capacity thermodynamic cycles and thermal systems. Special attention is paid to robustness and simulation speed since dynamic simulations are often limited by numerical constraints and failures, either during initialization or during integration. Furthermore, the use of complex equations of state (EOS) to compute thermodynamic properties significantly decreases the simulation speed. In this paper, the approach adopted in the library to overcome these challenges is presented and discussed. [less ▲]

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See detailExperimental investigation of an ORC system for a micro-solar power plant
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Declaye, Sébastien ULiege et al

in Proceedings of the 2014 Purdue Conferences (2014)

Because of the depletion of fossil fuels and global warming issues, the world energy sector is undergoing various changes towards increased sustainability. Among the different technologies being developed ... [more ▼]

Because of the depletion of fossil fuels and global warming issues, the world energy sector is undergoing various changes towards increased sustainability. Among the different technologies being developed, solar energy, and more specifically CSP (Concentrated Solar Power) systems are expected to play a key role to supply centralized loads and off-grid areas in the medium-term. Major performance improvements can be achieved by implementing advanced control strategies accounting for the transient and random nature of the solar heat source. In this context, a lab-scale solar power plant has been designed and is under construction for experimental purposes and dynamic analysis. The test rig includes an Organic Rankine Cycle (ORC) unit, a field of parabolic trough collectors and a thermal energy storage system. This paper presents the results of an experimental campaign conducted on the ORC module alone. This power unit, designed for a 2.8 kW net electrical output, consists of two scroll expanders in series, an air-cooled condenser, a recuperator, a volumetric pump and an oil-heated evaporator. The ORC engine is constructed using standard mass manufactured components from the HVAC industry, this practice reducing considerably the system cost. The overall unit performance and components effectiveness are presented in different operating conditions and relevant empirical correlations are derived to be implemented in a steady state model of the ORC unit. [less ▲]

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See detailMethods to Increase the Robustness of Finite-Volume Flow Models in Thermodynamic Systems
Quoilin, Sylvain ULiege; Bell, Ian ULiege; Desideri, Adriano ULiege et al

in Energies (2014), 7(3), 1621-1640

This paper addresses the issues linked to simulation failures during integration in finite-volume flow models, especially those involving a two-phase state. This kind of model is particularly useful when ... [more ▼]

This paper addresses the issues linked to simulation failures during integration in finite-volume flow models, especially those involving a two-phase state. This kind of model is particularly useful when modeling 1D heat exchangers or piping, e.g., in thermodynamic cycles involving a phase change. Issues, such as chattering or stiff systems, can lead to low simulation speed, instabilities and simulation failures. In the particular case of two-phase flow models, they are usually linked to a discontinuity in the density derivative between the liquid and two-phase zones. In this work, several methods to tackle numerical problems are developed, described, implemented and compared. In addition, methods available in the literature are also implemented and compared to the proposed approaches. Results suggest that the robustness of the models can be significantly increased with these different methods, at the price of a small increase of the error in the mass and energy balances. [less ▲]

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See detailPure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp
Bell, Ian ULiege; Wronski, Jorrit; Quoilin, Sylvain ULiege et al

in Industrial & Engineering Chemistry Research (2014), 53

Article Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp ACS ActiveView PDFHi-Res Print, Annotate, Reference QuickView PDF [2027 ... [more ▼]

Article Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp ACS ActiveView PDFHi-Res Print, Annotate, Reference QuickView PDF [2027 KB] PDF w/ Links[457 KB] Full Text HTML Abstract Supporting Info -> Figures Reference QuickView Add to ACS ChemWorx Ian H. Bell *†, Jorrit Wronski *‡, Sylvain Quoilin *†, and Vincent Lemort *† † Energy Systems Research Unit, University of Liège, Liège, Belgium ‡ Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark Ind. Eng. Chem. Res., 2014, 53 (6), pp 2498–2508 DOI: 10.1021/ie4033999 Publication Date (Web): January 13, 2014 Copyright © 2014 American Chemical Society OpenURL UNIV DE LIEGE *E-mail: ian.bell@ulg.ac.be., *E-mail: jowr@mek.dtu.dk., *E-mail: squoilin@ulg.ac.be., *E-mail: vincent.lemort@ulg.ac.be. ACS AuthorChoice Abstract Over the last few decades, researchers have developed a number of empirical and theoretical models for the correlation and prediction of the thermophysical properties of pure fluids and mixtures treated as pseudo-pure fluids. In this paper, a survey of all the state-of-the-art formulations of thermophysical properties is presented. The most-accurate thermodynamic properties are obtained from multiparameter Helmholtz-energy-explicit-type formulations. For the transport properties, a wider range of methods has been employed, including the extended corresponding states method. All of the thermophysical property correlations described here have been implemented into CoolProp, an open-source thermophysical property library. This library is written in C++, with wrappers available for the majority of programming languages and platforms of technical interest. As of publication, 110 pure and pseudo-pure fluids are included in the library, as well as properties of 40 incompressible fluids and humid air. The source code for the CoolProp library is included as an electronic annex. [less ▲]

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See detailRobust and Computationally Efficient Dynamic Simulation of ORC Systems: The ThermoCycle Modelica Library
Quoilin, Sylvain ULiege; Desideri, Adriano ULiege; Bell, Ian ULiege et al

Conference (2013, October 07)

The ThermoCycle library, an open-source library for dynamic modeling of ORC systems, has been recently developed in the Modelica language and is presented in this paper. Special attention has been paid to ... [more ▼]

The ThermoCycle library, an open-source library for dynamic modeling of ORC systems, has been recently developed in the Modelica language and is presented in this paper. Special attention has been paid to robustness and to simulation speed. Dynamic simulations are indeed often limited by numerical constraints and failures, either during initialization or during integration. Furthermore, the use of complex equations of state (EOS) to compute thermodynamic properties dramatically decreases the simulation speed. In this paper, the different numerical methods developed to overcome these limitations are presented and discussed and the proposed models are then benchmarked against alternative simulation tools. [less ▲]

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See detailInvestigation on a scroll expander for waste heat recovery on internal combustion engines
Legros, Arnaud ULiege; Guillaume, Ludovic ULiege; Lemort, Vincent ULiege et al

Scientific conference (2013, September 09)

In the present article, a model of scroll expander will be introduced. This model is able to evaluate the performance of a given machine with influence of the geometry. Several losses are also included by ... [more ▼]

In the present article, a model of scroll expander will be introduced. This model is able to evaluate the performance of a given machine with influence of the geometry. Several losses are also included by the model such as internal leakages, heat transfers or mechanical losses. The forces generated by the gas pressure on the involutes can also be calculated. That expander model is used in order to demonstrate its potential and provide some guidelines to the design of a new expander suitable for the application. [less ▲]

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See detailSimulation of a cold climate heat pump furnished with a scroll compressor with multiple injection lines
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in Proceedings of the International Conference on Compressors and their Systems 2013 (2013, September)

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for ... [more ▼]

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for cold climate heat pumps. The required analysis is developed for vapor injection in scroll compressors with one or two injection lines. The improvement in heat pump efficiency at a -20 C evaporation temperature with one injection line is as much as 10% while with two injection lines the increase in efficiency can be as much as 16% [less ▲]

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See detailExperimental Testing of an Oil-Flooded Hermetic Scroll Compressor
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Journal of Refrigeration (2013), 36

In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an ... [more ▼]

In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an isothermal compression process. The compressor was tested with oil injection mass flow fractions of up to 45%. At an evaporating temperature of -10C and condensing temperature of 30C, the overall isentropic efficiency was up to 70% at the highest oil injection rate. Overall, over the testing envelope investigated, there are no significantly negative effects experienced for the compressor and the compressor isentropic efficiency and refrigerant mass flow rate improve monotonically as the oil injection rate is increased. [less ▲]

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See detailA computationally efficient hybrid leakage model for positive displacement compressors and expanders
Bell, Ian ULiege; Groll, Eckhard; Braun, James E. et al

in International Journal of Refrigeration (2013), 36

An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors. This correction ... [more ▼]

An empirical frictional correction factor to the isentropic nozzle model has been developed for application to refrigerant leakage modeling in scroll, rotary and other similar compressors. This correction factor is derived by calculating the leakage mass flow rate with a compressible, variable area, real gas properties model and referencing the results to an isentropic nozzle model. The ratio of flows is correlated to the Reynolds number, a characteristic length and the leakage gap width. A representative selection of fluids and geometries are employed. For all the correlations, at least 93% of the points are predicted within an absolute error band of 20%. [less ▲]

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See detailDevelopment of a generalized steady-state simulation framework for positive displacement compressors and expanders
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in Proceedings of the International Conference on Compressors and their Systems 2013 (2013)

In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw ... [more ▼]

In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package. The source code can be freely obtained from http://pdsim.sf.net [less ▲]

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See detailOptimization of a scroll compressor for liquid flooding
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Journal of Refrigeration (2012), 35(7), 19011913

In two companion papers, simulation models for the working processes of liquid-flooded scroll compressors and expanders have been developed and validated against experimental data. In this study, analytic ... [more ▼]

In two companion papers, simulation models for the working processes of liquid-flooded scroll compressors and expanders have been developed and validated against experimental data. In this study, analytic models are presented for the modes of irreversibility generation in the liquid-flooded scroll compressor including built-in volume ratio maladjustment, pressure drop and leakage. A thermodynamic model is used to derive the ideal volume ratio for a liquid-flooded compressor, which is higher than that of dry compression. An optimum set of built-in volume ratio and scroll base circle radius is found which maximizes the overall isentropic efficiency by minimizing the leakage and pressure drop irreversibilities. The irreversibility generation models are used to optimize a scroll compressor for the Liquid-Flooded Ericsson cycle application. The model predicts scroll compressor overall isentropic efficiency of over 80% (based on the shaft power) at an oil mass fraction of 88%. [less ▲]

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See detailPerformance Comparison of Hydronic Secondary Loop Heat Pump and Conventional Air-Source Heat Pump
Bell, Ian ULiege; Braun, James

in International Refrigeration and Air Conditioning Conference at Purdue, July 16-19, 2012 (2012, July)

In residential heat pump systems, the motivation for secondary loop systems is to allow for the use of flammable or toxic refrigerants with lower global warming potentials than the currently employed HFC ... [more ▼]

In residential heat pump systems, the motivation for secondary loop systems is to allow for the use of flammable or toxic refrigerants with lower global warming potentials than the currently employed HFC refrigerants. The addition of radiant panels as integral building components (embedded in concrete at construction) is becoming more common. Combining the large surface area of the radiant panel and an efficient primary loop, the hydronic secondary loop heat pump system can greatly outperform the conventional air-to-air heat pump. The improvement in coefficient of performance is as much as 38% over the conventional air-to-air heat pump when the secondary loop hydronic system is employed. Due to the large area of the radiant panel, the condensing temperature of the primary loop for the hydronic secondary loop heat pump can be reduced by as much as 5°C at high ambient temperatures. [less ▲]

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See detailDerivation of optimal scroll compressor wrap for minimization of leakage losses
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Compressor Engineering Conference at Purdue, July 16-19, 2012 (2012, July)

The scroll wraps of a scroll compressor play a very important role in the compressor’s efficiency due to their impact on leakage and leakage irreversibilities. In this work, a short summary of the scroll ... [more ▼]

The scroll wraps of a scroll compressor play a very important role in the compressor’s efficiency due to their impact on leakage and leakage irreversibilities. In this work, a short summary of the scroll compressor geometry is presented. Using the geometry of the scroll wraps, an optimal scroll wrap geometry is derived for a given set of constraints on compressor displacement, scroll wrap thickness and volume ratio. This optimal scroll wrap geometry can be used as a starting point for further optimization in a detailed compressor model that includes the effects of mechanical losses. [less ▲]

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See detailLiquid flooded compression and expansion in scroll machines - Part II: Experimental testing and model validation
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in International Journal of Refrigeration (2012), 35

The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll ... [more ▼]

The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll machines were installed in a fully-instrumented Liquid- Flooded Ericsson Cycle test rig to conduct entire cycle performance tests. In addition, detailed compressor and expander performance data was obtained. Oil mass fractions of up to 92% and 76% were added to the gas entering the scroll compressor and expander respectively. The overall isentropic efficiency of the scroll compressor based on the shaft power with flooding was up to 73% and the volumetric efficiency was above 92%. For the expander, the best overall isentropic and volumetric efficiencies achieved were 66% and 105% respectively. The mechanistic model presented in the companion paper was vali- dated against the experimental data for both the compressor and the scroll expander with good agreement, though the agreement is better for the scroll compressor. [less ▲]

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See detailLiquid-flooded compression and expansion in scroll machines - Part I: Model development
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in International Journal of Refrigeration (2012)

A detailed mechanistic model has been developed for scroll compressors and scroll expanders with liquid flooding for application to the Liquid Flooded Ericsson Cycle. This model is based on the ... [more ▼]

A detailed mechanistic model has been developed for scroll compressors and scroll expanders with liquid flooding for application to the Liquid Flooded Ericsson Cycle. This model is based on the integration of a set of differential equations that arise from the conservation laws. The impact of the flooding liquid on the working process is also included through mixture properties as well as treatment of two-phase flow pressure drop. With the working process known, it is then possible to solve for the compressor power, total mass flow rate and other model outputs. The fine level of detail in the model allows for the investigation of the impact of design changes to the scroll machines. This model can also be readily extended to allow for the analysis of liquid flooded vapor compression refrigeration. [less ▲]

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See detailTheoretical and Experimental Analysis of Liquid Flooded Compression in Scroll Compressors
Bell, Ian ULiege

Doctoral thesis (2011)

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat ... [more ▼]

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat pump systems, simple cycle modeling predicts that for systems that operate at very large temperature lifts, the increase in system coefficient of performance can be greater than 50%. In order to better understand the liquid-flooded working process, a detailed scroll compressor model has been developed which comprises a geometric model and an overall compressor model. The geometric model includes numerically validated analytic solutions for all geometric parameters, including force terms, for constant wall thickness scroll wraps that can have multiple pairs of compression chambers. The overall model includes a frictionally-corrected isentropic nozzle leakage model, adaptive Runge-Kutta solver for the system of differential equations, and numerically efficient thermodynamic and transport property routines. The compressor model has been validated against testing conducted on the Liquid-Flooded Ericsson Cycle for oil mass fractions as high as 92% oil by mass with error in predictions of shaft power and mass flow less than 3%. Optimization of the compressor performance with flooding for several applications is carried out, and with optimization, overall isentropic efficiencies over 75% are predicted for configurations with large amounts of oil flooding. Further testing on a refrigerant R410A vapor injected compressor with oil injection has shown that the performance with oil injection improves monotonically with the oil injection rate as long as the oil is cooled prior to injection. [less ▲]

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See detailAir-side particulate fouling of microchannel heat exchangers: Experimental comparison of air-side pressure drop and heat transfer with plate-fin heat exchanger
Bell, Ian ULiege; Groll, Eckhard

in Applied Thermal Engineering (2011), 31(5), 742-749

In this study, the air-side pressure drop and heat transfer performance of plate-fin and microchannel coils were tested under clean and fouled conditions. The heat exchangers were tested with two ... [more ▼]

In this study, the air-side pressure drop and heat transfer performance of plate-fin and microchannel coils were tested under clean and fouled conditions. The heat exchangers were tested with two different types of dust, ASHRAE dust and Arizona Road Test Dust. The ASHRAE dust was found to have a very significant impact on the pressure drop of the microchannel heat exchanger, increasing the air-side pressure drop of the microchannel heat exchanger over 200% for a dust injection of 267g (1612.5 g/m2). Fouling of the microchannel heat exchanger with Arizona Road Test Dust was not found to increase the air-side pressure drop of the microchannel heat exchanger but was found to decrease the heat transfer rate by more than 10%. In addition, from studies of the evolution of the air-side pressure drop during the fouling process, it is seen that microchannel coils with louvered fins with fin pitch below 2.0 mm were significantly more prone to fouling than louvered heat exchangers with larger fin pitch. Particulate fouling of the wavy-plate-fin heat exchanger resulted in significantly lower reductions in heat transfer and increase in air-side pressure drop than for the microchannel heat exchanger. [less ▲]

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See detailExperimental Analysis of the Effects of Particulate Fouling on Heat Exchanger Heat Transfer and Air-Side Pressure Drop for a Hybrid Dry Cooler
Bell, Ian ULiege; Groll, Eckhard; Konig, Holger

in Heat Transfer Engineering (2011), 32

It is well known that significant fouling by particulate matter can have a deleterious effect on the performance of enhanced surface heat exchangers, and the same is true for hybrid heat exchangers ... [more ▼]

It is well known that significant fouling by particulate matter can have a deleterious effect on the performance of enhanced surface heat exchangers, and the same is true for hybrid heat exchangers. Hybrid heat exchangers are heat exchangers which are typically run in dry mode to reject heat. When the ambient conditions require more heat rejection than can be provided by sensible heat transfer a water pump is turned on and water flows over the fins and the evaporation of water provides a further cooling effect. Fouling in dry mode operation is physically similar to that of air-cooled heat exchangers, but in evaporative mode the flow of the water over the coil eliminates the impact of fouling. A hybrid dry cooler heat exchanger of 60 cm x 60 cm frontal area has been installed in a well-instrumented wind tunnel to measure the heat exchanger’s performance. Hot water flows through the coil to provide the load, and air flows over the coil to provide cooling. During evaporative mode operation another stream of water flows over the outside face of the coil, adhering mainly to the louvered fins. The louvered fins are specially designed for optimized water flow during wetting mode. The fins are made of aluminum, the tubes are copper, and protection against corrosion is realized by a special E-coating. This coil has been tested clean and fouled with ASHRAE standard dust, for both dry and wet operation. Results are presented for the air side pressure drop and overall heat transfer conductance of the coil under all conditions for which 50% increases in air-side pressure drop are found under heavy fouling. The influence of fouling on heat transfer is small. Also, using the wetting water to wash the fouling off the coil is investigated, and found to be of some limited utility. [less ▲]

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