Designing scroll expanders for use in heat recovery Rankine cycles

(2009)

This paper first investigates experimentally the performance of a prototype of oilfree open-drive scroll expander working with water and with HCFC-123. Using experimental data, two different simulation ... [more ▼]

This paper first investigates experimentally the performance of a prototype of oilfree open-drive scroll expander working with water and with HCFC-123. Using experimental data, two different simulation models of the expander are then proposed and validated. These models are finally used to analyze the measured performance with regard to the expander design characteristics. [less ▲]

Contribution to the Characterization of Scroll Machines in Compressor and Expander Modes

Doctoral thesis (2008)

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used ... [more ▼]

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used inside an air-cooled water chiller. b) An oil-free open-drive scroll expander integrated into an Organic Rankine Cycle (ORC) power system. c) Open-drive scroll compressor and expander used in a Liquid Flooded Ericsson Cycle Cooler (LFEC). Such a system uses the liquid flooding of the compressor and of the expander to approach isothermal compression and expansion processes. New semi-empirical models of the scroll compressor and expander were proposed and existing models improved. A deterministic model of the scroll expander was established. The model associates a geometrical description of the machine with a thermodynamic description of the expansion process. This model was validated for the two expanders investigated experimentally. The model validation revealed that the performance of the expanders is mainly affected by the supply pressure drop and by the internal leakages. Using the validated model, parametric studies were carried out to investigate the variation of the performance of both expanders with modification of their design and with the operating parameters. The thesis also investigated the scroll machines from the point of view of their integration into thermal systems. A first experimental investigation was carried out on an air-cooled chiller. The scroll compressor semi-empirical model, with its parameters identified on the basis of published manufacturer data, was used as a refrigerant flow meter. The analysis of the experimental data allowed a better understanding of the chiller operation and a better identification of its model parameters (such as the fan and the hot gas bypass control models). A second experimental investigation was carried out on an ORC power system, working with R123. In order to select the most appropriate fluid, the performances achieved with four different fluids were compared by simulation. The experimental study confirmed that the scroll expander is a good candidate for an ORC system: the tested prototype presented a good performance (the maximum global isentropic effectiveness achieved was 68%). Using an ORC simulation model, parametric studies were carried out to investigate the effects of the expander characteristics and operating conditions on the cycle performance. The latter is mainly affected by the expander internal leakage and by the liquid subcooling at the condenser exhaust. A third experimental investigation was performed on a LFEC working with nitrogen as refrigerant and alkyl-benzene oil as flooding liquid. Experimental data was used to identify the parameters of the scroll compressor and expander semi-empirical models. Parametric studies were performed to identify the different factors affecting their performance. One of the undesirable features of the machines is the increase of the supply and exhaust pressure drops with the increase of oil quantity. [less ▲]

Analysis of Liquid-Flooded Compression Using a Scroll Compressor

(2008, July)

One possible means of decreasing the work of compression of a scroll gas compressor is by injecting, or flooding, high specific heat liquid into the inlet gas stream of the compressor. The high specific ... [more ▼]

One possible means of decreasing the work of compression of a scroll gas compressor is by injecting, or flooding, high specific heat liquid into the inlet gas stream of the compressor. The high specific heat liquid can then absorb the heat of compression of the gas and offer the possibility of a reduction in the net power of the compressor. The particular application of interest for this flooded-compression technology is the Liquid-Flooded Ericsson cycle as proposed by Hugenroth et al. (2007), a gas refrigeration cycle. Adequate performance of the Ericsson cycle is contingent on designing scroll compressors that can efficiently compress high heat of compression gases. A detailed model of the flooded scroll compressor has been constructed which allows prediction of the compressor performance over a wide range of operating conditions. The detailed flooded scroll compressor model has been validated with experimental data, for which good agreement was found. [less ▲]

Analysis of liquid-flooded expansion using a scroll expander

(2008, July)

This paper presents the development and the experimental validation of a model of a scroll expander integrated into a Liquid Flooded Ericsson Cooler (LFEC) as proposed by Hugenroth (2007). This system ... [more ▼]

This paper presents the development and the experimental validation of a model of a scroll expander integrated into a Liquid Flooded Ericsson Cooler (LFEC) as proposed by Hugenroth (2007). This system uses liquid flooding of the compressor and the expander to approach isothermal compression and expansion processes. A detailed model of the flooded scroll expander has been constructed which allows prediction of its performance over a wide range of operating conditions. This model is validated with experimental data collected on a prototype of a Liquid Flooded Ericsson Cooler. A parametric study is finally conducted for investigating the performances of the expander under different design changes, such as the shape of the tip of the scroll and the leakage gap size. [less ▲]

Study of an Organic Rankine Cycle Associated to a Biomass-Fuelled Boiler for Cogeneration Application

(2008, April)

This paper presents a cogeneration system composed of a biomass-fuelled boiler and of an Organic Rankine Cycle (ORC). The first part of the paper describes the model of the system. This model is built by ... [more ▼]

This paper presents a cogeneration system composed of a biomass-fuelled boiler and of an Organic Rankine Cycle (ORC). The first part of the paper describes the model of the system. This model is built by interconnecting the sub-models of the different components: heat exchangers, pump, boiler and scroll expander. In the second part, the results of an experimental study are presented : this study aimed at evaluating the performances of an ORC working with refrigerant R-123 and using scroll expander. The above models are validated using test results. The last part of the paper investigates, through simulations, the performances of the cogeneration system and points out some possible improvements. [less ▲]

Numerical Simulation of a Scroll Expander for Use in a Rankine Cycle

(2008)

This paper presents two simulation models of scroll expanders for use in heat recovery Rankine cycle applications: a detailed reference model and a simplified model. The reference model associates a ... [more ▼]

This paper presents two simulation models of scroll expanders for use in heat recovery Rankine cycle applications: a detailed reference model and a simplified model. The reference model associates a detailed geometrical description of the expander to a thermodynamic modeling of the expansion process in the machine. Due to large computational effort, the reference model is not appropriate for simulation of the entire Rankine cycle system. The paper shows how a simplified model can be built from the reference model. This model involves a limited number of parameters, which describe the main features of the machine. An experimental study is carried out on a prototype of Rankine cycle working with HCFC-123. Based on detailed measurements, the validation of both models is conducted. It is found that both models are able to predict the mass flow rate, the delivered shaft power and the discharge temperature with a good accuracy. [less ▲]

From model validation to production of reference simulations: how to increase reliability and applicability of building and HVAC simulation models

in Building Services Engineering Research & Technology (2008), 29(1), 61-72

Validation of simulation models appears from a long time as a key issue in order to promote a more intensive and more efficient use of simulation models in the field of building and HVAC simulation. IEA ... [more ▼]

Validation of simulation models appears from a long time as a key issue in order to promote a more intensive and more efficient use of simulation models in the field of building and HVAC simulation. IEA Annex 34/43 originally targeted a number of specific applications where a more advanced validation was required: ground coupling problems, multizone building, shading, day lighting and cooling load interaction, HVAC components and ventilated facades. These validation exercises were built on the large methodological experience obtained in previous projects and address sometimes very fundamental problems of heat transfer in buildings. Consulting engineers and practitioners might see these exercises as a bit too far from their objectives and it is the reason why an additional activity was proposed with the specific aim of producing, based upon the results of the validation of models, a set of reference simulations. These applications cover a range of building types (residential, commercial) and systems (production, distribution emission) and run in a variety of climates. The paper will describe how models dedicated to these applications were developed, starting from validation results, going through the selection and consolidation of simulation hypothesises and ending with a number that might be considered as reference for the concerned applications. The paper will concentrate on models required by a residential building application (multizone building equipped with a heat pump or a condensing boiler, heat emitted by radiators or floor heating systems). Simulations make use of both EES and TRNSYS software and both software are applied in parallel as far as possible in the different applications in order to get a better judgment of their potential advantages and drawbacks. The use of reference simulations in view of qualifying normative methods currently in development in the frame of the European Energy Performance in Buildings Directive is also addressed and demonstrated in the paper. [less ▲]

Machines et Systèmes Thermiques

Learning material (2007)

Friendly simulation of residential heating systems.

Conference (2007, June)

Until now, the choice of a heating system is, in most cases, rather intuitive, but not based on significant comparisons among the many options available on the market. Friendly calculation tools are badly ... [more ▼]

Until now, the choice of a heating system is, in most cases, rather intuitive, but not based on significant comparisons among the many options available on the market. Friendly calculation tools are badly needed. A prototype of simulation model is shortly presented in this paper. It is designed as a preliminary design tool, allowing the different partners of a project to evaluate the energy impact of the very first design options: building envelope heat transfer coefficients, glazing areas, orientations, solar factors, ventilation mode, heat emission, distribution, generation and control strategy. The heating demand is calculated hour by hour with consideration to the time variations of inside and outside temperatures and free gains, to the control law and to the heating power actually available. The emitter is a water-ambient heat exchanger. It may have some thermal mass. Two emitters are here proposed: the radiator and the flow heating system. A steady state water distribution model is included in this simulation; it takes heat losses in unheated spaces into account: Three typical heating sources are proposed: classical boiler, condensing boiler and heat pump. All heat generators are here simulated with the help of very simple polynomial (“daughter”) models. The polynomial expressions are fitted on the simulation results obtained with reference (“mother”) models, themselves fitted on experimental data available. Examples of simulation results are presented in the paper. [less ▲]

Contribution à l'étude des cycles de Rankine de récupération de chaleur

(2007, May)

Ce papier présente tout d’abord un modèle de cycle de Rankine, dont l’expanseur est de type spiro-orbital. Ce modèle doit permettre d’orienter le design des différents éléments du cycle, mais aussi de ... [more ▼]

Ce papier présente tout d’abord un modèle de cycle de Rankine, dont l’expanseur est de type spiro-orbital. Ce modèle doit permettre d’orienter le design des différents éléments du cycle, mais aussi de prédire les performances du cycle pour des conditions opératoires imposées. Une méthode de comparaison des performances réalisées par différents fluides est ensuite proposée. Les résultats d’une étude expérimentale menée sur un prototype de cycle de Rankine de récupération de chaleur sont finalement présentés. Le modèle du cycle et la méthode de comparaison des performances des fluides ont été utilisés pour orienter le design de l’expanseur spiro-orbital et sélectionner le fluide de travail. [less ▲]