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See detailSimulation-assisted evaluation of potential energy savings: Application to an administrative building in France
Randaxhe, François ULg; Bertagnolio, Stéphane ULg; Lemort, Vincent ULg

in Randaxhe, François; Bertagnolio, Stéphane; Lemort, Vincent (Eds.) International Conference for Enhanced Building Operations ICEBO 2012 at Manchester, October 23-26, 2012 (2012, October)

The case study presented here falls within a project of feasibility studies to improve the energy efficiency, the carbon footprint and the environmental impacts of several administrative buildings in ... [more ▼]

The case study presented here falls within a project of feasibility studies to improve the energy efficiency, the carbon footprint and the environmental impacts of several administrative buildings in France. The first part of the paper briefly presents the data obtained during a classical audit and inspection procedure: the description of the building in term of design, the HVAC system characteristics, the occupancy and operating profiles and the control strategy applied. The second part of the paper gives the first results obtained using an evidence-based calibrated building energy simulation model to analyze the actual building global consumption but also analyze the local consumptions (heat pumps, air handling units, terminal units, lightings, pumps,...). The last part of the paper then demonstrates the possibilities given by the building energy simulation model to evaluate potential energy saving scenarios through different examples. The advantages and drawbacks of the applied methods and tools are also discussed. [less ▲]

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See detailDynamic modeling and control strategies for Organic Rankine Cycle systems
Quoilin, Sylvain ULg; Lemort, Vincent ULg

Conference (2012, September 13)

Control and optimization are major issues in ORC systems applied to waste heat sources. This talk provides an overview of the current state of the art and of the main areas of R&D in that topic, including ... [more ▼]

Control and optimization are major issues in ORC systems applied to waste heat sources. This talk provides an overview of the current state of the art and of the main areas of R&D in that topic, including: - Steady-state and dynamic modeling of ORC cycles (simulation platforms, modeling paradigms, numerical issues) - Optimization of the working conditions for a given heat source and heat sink, and in particular of the evaporating temperature - Optimal start-up and shut-down strategies (grid synchronization, pressure overshoot, ...) - Control of the cycle under transient heat source conditions - Traditional and advanced controllers (PID, Model predictive control) The different adjustable working conditions (condensing/evaporating temperature, superheating, subcooling, working fluid flow rate) are listed with regard to the available degrees of freedom (pump/expander speed, secondary fluid flow rates and temperatures) and their optimal values are derived, depending on the target application. [less ▲]

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See detailAdvances in ORC expander design
Lemort, Vincent ULg; Quoilin, Sylvain ULg

Conference (2012, September 13)

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See detailCharacterisation of a scroll expander for small scale absorption power and cooling cycle activated by solar energy or waste heat
Mendoza, Luis Carlos; Navarro, Joaquin; Lemort, Vincent ULg et al

Poster (2012, September)

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See detailDESIGN OF A SMALL-SCALE ORGANIC RANKINE CYCLE ENGINE USED IN A SOLAR POWER PLANT
Declaye, Sébastien ULg; Georges, Emeline ULg; Bauduin, Maxime ULg et al

in Proceedings of Heat Powered Cycles Conference 2012 (2012, September)

Under the economical and political pressure due to the depletion of fossil fuel and global warming potential, it is necessary to develop more sustainable techniques to provide electrical power. In this ... [more ▼]

Under the economical and political pressure due to the depletion of fossil fuel and global warming potential, it is necessary to develop more sustainable techniques to provide electrical power. In this context, medium and large scale Organic Rankine Cycle solar power plants appear to be a promising solution because of their good efficiency, robustness and acceptable economical probability. However, only a few ORC solar power plants are in operation today, but technical literature indicate that several demonstration projects are under development. The spreading out of that technology requires, among others, a good knowledge of control strategies of the entire plant comprising the field of parabolic trough collectors, the ORC engine and thermal storage systems. The present project aims at designing, building and testing a small scale ORC solar power plant (a few kWe) in order to define and optimize control strategies that could be applied to larger systems. The paper presents the design step of the solar power plant, and more specifically the ORC engine. This design is defined based on simulation models of the ORC engine and on the experience gained in the Thermodynamics laboratory in the field of testing small-scale ORC systems. The design accounts for technical limitations such as allowed operating ranges and technical maturity of components. The paper first presents the architecture of the envisioned solar plant. The choice of the different technologies of components is justified. Simulation models of components (scroll expander, plate and fin-and-tubes heat exchangers, etc.) and of the whole system are then presented. Based on those models, parametric studies are conducted in order to optimize the sizing and the operating conditions of the system and to select the most appropriate working fluid. Also, the relevance of using two expanders in series is discussed and the control of the ORC engine is investigated. Simulations indicate that ORC engine efficiency close to 12% can be reached for evaporating and condensing temperatures of 140°C and 35°C. [less ▲]

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See detailExperimental investigation on a decentralized air handling terminal: procedure of aeraulic and thermal performance determination of the entire unit under several operating conditions
Gendebien, Samuel ULg; Prieels, Luc; Lemort, Vincent ULg

in Proceedings of the 6th European Thermal Sciences Conference (2012, September)

A new local ventilation device is actually developed in such a way to procure ventilation “on demand” in each room, with a maximal effectiveness. It consists in a wall or window frame mounted plane ... [more ▼]

A new local ventilation device is actually developed in such a way to procure ventilation “on demand” in each room, with a maximal effectiveness. It consists in a wall or window frame mounted plane-parallel box, containing two (injection and extraction) fans, an electronic control, and a heat recovery exchanger. The present paper describes the experimental investigations carried out on some single components and on the entire unit in order to characterize the aeraulic and thermal performance of the device. [less ▲]

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See detailGlobal Sensitivity Analysis applied to Total Energy Use in Buildings
Ruiz Flores, Roberto ULg; Bertagnolio, Stéphane ULg; Lemort, Vincent ULg

in Proceedings of the 2nd International High Performance Buildings Conference (2012, July 16)

The work presented in this paper has been carried out in the frame of the IEA-ECBCS Annex 53 project: “Total Energy Use in Buildings: Analysis and evaluation methods”. The aim of this work is to present a ... [more ▼]

The work presented in this paper has been carried out in the frame of the IEA-ECBCS Annex 53 project: “Total Energy Use in Buildings: Analysis and evaluation methods”. The aim of this work is to present a methodology to identify the most influential parameters affecting the final energy consumption in office buildings. In order to represent buildings and HVAC systems, a representative typology was defined, modeled and simulated and subsequently a global sensitivity analysis (variance-based method) was performed. This paper provides useful information to future works related to design building decisions, building calibration, energy management strategy, etc. helping to detect and rank those factors which need to be better measured and/or estimated, in order to improve building energy efficiency. [less ▲]

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See detailEnergy and comfort performance analysis of monitored thermally activated building systems combined with geothermal heat pumps
Gantiez, Clément ULg; Lemort, Vincent ULg; Hoogmartens, Jan et al

in International High Performance Buildings Conference at Purdue, July 16-19, 2012 (2012, July)

The combination of geothermal heat pumps (GEO HPs) and thermally activated building systems (TABS), that allow both low temperature heating and high temperature cooling, could yield primary energy savings ... [more ▼]

The combination of geothermal heat pumps (GEO HPs) and thermally activated building systems (TABS), that allow both low temperature heating and high temperature cooling, could yield primary energy savings of around 20- 71% in comparison with conventional heating/cooling systems. However, the potential energy savings are rarely reached in practice due to bad integration of the different subsystems and inefficient control. The present paper presents the analysis of two monitoring campaigns by stressing the influence of relevant parameters such as the performance of components (heat pump, ground heat exchangers, TABS, etc.), building characteristics and the implemented control strategies. The buildings have been monitored and analyzed in the frame of the WKSP-project realized by Institute of Building Services and Energy Design (IGS) at Technical University of Braunschweig. The results show good performance of ground coupled heat pump with seasonal COP up to around 5. Moreover, the use of ground heat exchangers to perform free chilling allows seasonal EER up to 20. Furthermore, the control strategies implemented in the different buildings are quite different. It is also shown that this system can lead to a running cost reduction up to 50% compared to conventional systems and that CO2 emissions can be reduced by 40%. [less ▲]

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See detailExperimental Investigation on a Reversible Heat Pump for a Passenger Car
Lemort, Vincent ULg; Cuevas, Cristian; Declaye, Sébastien ULg

in Proceedings of the 21st International Compressor Conference, Purdue 2012 (2012, July)

This paper summarizes the first results of a research project dealing with the development of a reversible heat pump for a passenger car. Heat pump systems appear to be a more efficient alternative to ... [more ▼]

This paper summarizes the first results of a research project dealing with the development of a reversible heat pump for a passenger car. Heat pump systems appear to be a more efficient alternative to electrical resistance heaters for the purpose of heating the car indoor environment. Heat pump systems could be easily implemented into cars by allowing the air-conditioning system to run in reverse. In order to check the technical feasibility of a reversible heat pump system, and to point out technical barriers, a prototype was built and tested. Experimental data was also used to calibrate and validate simulation models of components. A heat pump system model was finally built to investigate the operating conditions of the system. The first part of the paper describes the test rig (architecture, components, and measurement devices) and the experimental campaign. Performance of components (compressor, evaporator, condenser and heater core) is evaluated in terms of variation with the operating conditions. The second part of the paper presents the steady-state semi-empirical models of the components. Such lumped models retain and concentrate the main physical phenomena inherent to the components into successive elementary processes (pressure losses, heat transfers, etc.). They require a limited number of parameters that can be identified based on experimental data. The calibration and the validation of the proposed component models are detailed. Finally, an overall simulation model of the reversible heat pump system is proposed and used to evaluate the energy performance of the system as function of the operating conditions. [less ▲]

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See detailLiquid flooded compression and expansion in scroll machines - Part II: Experimental testing and model validation
Bell, Ian ULg; Lemort, Vincent ULg; 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 ULg; Lemort, Vincent ULg; 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 detailWorking fluid selection and operating maps for Organic Rankine Cycle expansion machines
Quoilin, Sylvain ULg; Declaye, Sébastien ULg; Legros, Arnaud ULg et al

in Proceedings of the 21st International Compressor Conference at Purdue (2012)

Fluid selection for the Organic Rankine Cycle has been the object of an abundant literature. Most of the scientific publications focus on the cycle thermodynamic efficiency in order to select the best ... [more ▼]

Fluid selection for the Organic Rankine Cycle has been the object of an abundant literature. Most of the scientific publications focus on the cycle thermodynamic efficiency in order to select the best candidate. However, other thermodynamics properties, such as molar mass, or vapor density condition the whole design of the cycle, and its cost. For example, the molar mass influences the number of stages required in the case of an axial turbine; the volume ratio between expander supply and exhaust conditions the possibility to use a volumetric expander (whose internal volume ratio is limited); the vapor density at the expander exhaust determine the size of the expander, and of the condenser; etc. This paper considers a whole range of ORC applications, in terms of power (from the kW-scale to the multi-MW plants), heat source temperature (from 90°C to more than 300°C) or heat source nature (solar, biomass, waste heat recovery, geothermy, etc.). For each of these applications, a screening of the available fluids is performed, and their thermodynamics performance are compared with respect to the foreseen application. A detailed analysis of the most common expansion machines is then conducted, by comparing their respective operating maps for each fluid and for each application type. The considered expansion machines are the radial-inflow turbine, the screw expander, and the scroll expander, since they are the most widely used in commercial applications and/or in scientific literature. [less ▲]

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See detailReciprocating expander for an exhaust heat recovery Rankine cycle for a passenger car application
Glavatskaya, Yulia; Podevin, Pierre; Lemort, Vincent ULg et al

in Energies (2012)

Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in ... [more ▼]

Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in fuel consumption. One solution is to integrate a heat recovery system based on a steam Rankine cycle. The key component in such a system is the expander, which has a strong impact on the system’s performance. A survey of different expander technologies leads us to select the reciprocating expander as the most promising one for an automotive application. This paper therefore proposes a steady-state semi-empirical model of the expander device developed under the EES (Engineering Equation Solver) environment. The ambient and mechanical losses as well as internal leakage were taken into account by the model. By exploiting the expander manufacturer data, all the parameters of the expander model were identified. The model computes the mass flow rate, the power output delivered and the exhaust enthalpy of the steam. The maximum deviation between predictions and measurement data is 4.7 %. A performance study of the expander is carried out and shows that the isentropic efficiency is quite high and increases with the expander rotary speed. The mechanical efficiency depends on mechanical losses which are quite high, approximately 90%. The volumetric efficiency was also evaluated. [less ▲]

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See detailAutomotive electric scroll compressor: Testing and modeling
Cuevas, Cristian; Fonseca, Nestor; Lemort, Vincent ULg

in International Journal of Refrigeration (2012)

The aim of this research is to characterize experimentally and by modelling an electrically driven automotive scroll compressor. The experimental characterization is carried out through 13 tests at ... [more ▼]

The aim of this research is to characterize experimentally and by modelling an electrically driven automotive scroll compressor. The experimental characterization is carried out through 13 tests at compressor speeds varying between 3000 and 5000 rpm. The DC/AC converter used to supply the compressor was characterized through a calorimetric balance, obtaining an efficiency that depends only on the compressor speed, ranging from 92.5 %, for a compressor speed of 1500 rpm, to 97.5%, for a compressor speed of 5000 rpm. The experimental results are used to identify the parameters of a semi-empirical compressor model, which is able to predict with an acceptable accuracy the main outputs of the mathematical model: confidence limits on the exhaust temperature of ± 1.0 K, on the refrigerant flow rate of ± 2 g s-1 and on the compressor power of ±60 W. This model is then used to determine the compressor cooling power at different compressor speeds and condensing pressures. [less ▲]

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See detailModeling and experimental validation in partially wet conditions of an air-to-air heat recovery exchanger
Gendebien, Samuel ULg; Bertagnolio, Stéphane ULg; Lemort, Vincent ULg

in Proceedings of the 12th Conference of The International Building Performance Simulation Association (2011, November)

Nowadays, important efforts are deployed to reduce our current residential building consumption. The most common retrofit option concerns the air tightness and the thermal insulation improvement. However ... [more ▼]

Nowadays, important efforts are deployed to reduce our current residential building consumption. The most common retrofit option concerns the air tightness and the thermal insulation improvement. However, this latter retrofit option could decrease the air indoor quality because of a reduction of air infiltration flow rate. Installation of an air-to-air heat recovery system allows for an efficient combination between consumption reduction due to the air tightness improvement and acceptable air indoor quality. The study presented in this paper has been realized in the frame of the „Green +‟ project, which aims at developing decentralized heat recovery ventilation systems. The present paper focuses on modeling and experimental validation of an air-to-air heat recovery exchanger in partially wet conditions (i.e. where condensation might occur in one of the two air streams). The knowledge of the thermal performance in dry and wet regimes is essential since it highly impacts on the heat recovered from the vitiated air flow rate (extracted from the building) to the fresh air flow rate (coming from the outdoor). The first part of the paper briefly describes a solving procedure able to determine the regime (completely dry, completely wet and partially wet). A moving boundary model for the partially wet regime is applied in order to predict performance of such device. Secondly, the experimental apparatus (and its control) designed to characterize thermal performance in different operating conditions (dry and wet regime) is presented. [less ▲]

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See detailComparison of control strategies for waste heat recovery Organic Rankine Cycle systems
Lemort, Vincent ULg; Zoughaib, Assaad; Quoilin, Sylvain ULg

(2011, October)

This paper investigates the control of waste heat recovery Organic Rankine Cycle systems. A dynamic simulation model of the system was developed under Modelica language. This model associates the sub ... [more ▼]

This paper investigates the control of waste heat recovery Organic Rankine Cycle systems. A dynamic simulation model of the system was developed under Modelica language. This model associates the sub-models of the different components of the system: the evaporator, a scroll expander, the condenser, the liquid receiver and the pump. Both the speeds of the expander and of the pump are controlled in order to adjust the evaporating pressure and maintain the superheat at the outlet of the evaporator. Two types of controllers were implemented: Proportional Integral (PI) and Model Predictive Control (MPC) controllers. The PI controller on the expander speed is able to adjust the evaporating pressure with a high accuracy. It is also shown that the MPC controller on the pump speed maintains the superheat close to the set point value with a much better performance than the PI controller. Hence, the use of a MPC controller allows decreasing the set point value on the superheat without any risk of feeding the expansion machine with liquid droplets. [less ▲]

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See detailDevelopment of a waste heat recovery orc prototype using an oil-free scroll expander
Declaye, Sébastien ULg; Quoilin, Sylvain ULg; Lemort, Vincent ULg

Conference (2011, September 22)

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 severe damages to ... [more ▼]

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 severe 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. [less ▲]

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See detailNumerical optimization of an injection volumetric expander for use in waste heat recovery organic Rankine cycle
Declaye, Sébastien ULg; Quoilin, Sylvain ULg; Lemort, Vincent ULg

in Proceedings of the 7th International Conference on Compressors and their Systems (2011, September 05)

Waste heat recovery organic Rankine cycle (ORC) systems allow generating mechanical or electrical power from local low grade heat sources. This paper shows how the power produced by the system can be ... [more ▼]

Waste heat recovery organic Rankine cycle (ORC) systems allow generating mechanical or electrical power from local low grade heat sources. This paper shows how the power produced by the system can be increased by achieving several evaporating pressure levels and injecting low pressure flow during expansion. A numerical model of the vapour injection expansion is developed and different system configurations are compared. In comparison with a simple configuration of the cycle, vapour injection configuration yields a maximum increase of 16% of the power production. Moreover, the specific power can be increased by 26%, which would largely reduce the specific investment cost of the waste heat recovery system. [less ▲]

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See detailExhaust Heat Recovery Rankine System for passenger cars: modelling and design
Glavatskaya, Yulia; Lemort, Vincent ULg; Podevin, Pierre et al

(2011, July)

Nowadays, in average, one third of the fuel energy consumed by an engine is wasted throughout the exhaust gases. The recovery of this amount of energy would enable a reduction of the fuel consumption. One ... [more ▼]

Nowadays, in average, one third of the fuel energy consumed by an engine is wasted throughout the exhaust gases. The recovery of this amount of energy would enable a reduction of the fuel consumption. One solution is to integrate an exhaust heat recovery system based on a Rankine cycle. The first and most crucial step in the design is the definition of its architecture, the definition of the rated operating conditions and the sizing of the different components whilst considering the heat recovery over customer driving cycles. This paper presents a steady-state model of a steam Rankine cycle built by interconnecting sub-models of the heat exchangers, the pump and the expander. All the models were developed under EES (Engineering Equation Solver) environment. The models of heat exchanger are developed using the ε-NTU method. A heat exchanger is subdivided into three zones, each of them being characterized by both the exhaust gases and water side pressure drop as well as heat transfer coefficient. The evaluation of the two-phase zone pressure drop and heat transfer with respect to the vapour quality was carried out. The model of rotary piston expander describes the evolution of the fluid through the device and was split into three global steps: pressure drop across the supply port, isentropic and expansion at constant volume, internal and external heat transfers. The overall simulation model is finally used to predict the performance of the heat recovery system as the operating conditions and geometrical characteristics of each component are modified. An optimal sizing of the system is proposed and the underlying methodology is discussed. The analysis of the results pointed out that the levels of high/low pressure and the amount of superheat are the main parameters that impact the performance of the cycle and the sizing of the components. [less ▲]

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