Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Taleghani, S. Taslimi; Sorin, Mikhaı̈l; Poncet, Sébastien

doi:10.3390/en12091686

Cited by 9 publications

(5 citation statements)

References 29 publications

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“…Many scientific papers presenting results of exergy analysis appear every year in the literature. They concern, for instance, combined cycle power plants [1][2][3][4], steam Rankine cycles [5][6][7][8], organic Rankine cycles [9][10][11][12], refrigeration cycles [13][14][15][16], thermal and PV solar systems [17][18][19][20], fuel cells [21][22][23][24], heat exchangers [25][26][27][28]. Review papers on the exergy analysis of combined cycle power plants [29], steam power plants [30], solar energy applications [31], fuel cells [32], and heat exchangers [33] are available.…”

Section: Introductionmentioning

confidence: 99%

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A unified deduction of the expressions of exergy and flow exergy

Zanchini

2023

Eur. J. Phys.

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Exergy analysis is a branch of thermodynamics receiving an increasing interest in the scientific literature and in didactic presentations. Exergy represents the maximum useful work obtainable by a system that can interact with a reference environment. There exist two exergy functions: exergy, that refers to a collection of matter contained within the reference environment; flow exergy, that refers to a collection of matter flowing in a pipe, that can interact with the environment and diffuse into it. The usual derivations of the expressions of exergy and flow exergy are either complicated or not general. Moreover, two separate derivations are necessary, due to the different conceptual schemes employed in the definitions of these properties. As a consequence, the expressions of exergy and flow exergy are often reported without a derivation in didactic treatises. In this paper, we provide a simple and general unified deduction of the expressions of exergy and flow exergy. Moreover, we show that the logical scheme proposed, based on the concept of useful energy of a system contained in a pressure field, allows a simpler deduction and a deeper interpretation of the energy balance equation for a control volume in steady state. Finally, in order to complete the didactic treatment, we rewrite the expression of the molar exergy of a pure substance at ambient temperature and pressure in a form applicable to reactive substances, and we present an application of this form.

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Section: Introductionmentioning

confidence: 99%

“…If one now considers the sequence of the infinitesimal deformations of S that yield the displacement of A from V 1 to V 2 , one obtains equation (13).…”

Section: Introductionmentioning

confidence: 99%

A unified deduction of the expressions of exergy and flow exergy

Zanchini

2023

Eur. J. Phys.

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“…However, in the transcritical heat pump cycle, the higher-pressure difference causes higher exergy loss, so choosing the appropriate expansion device is vital. The ejector was introduced as an alternative method to decrease the expansion loss, and it attracts many researchers' attention [3,[7][8][9][10]. Fangtian and Yitai [11] compared the ejector and throttling valve performance in the heat pump cycle.…”

Section: Introductionmentioning

confidence: 99%

Exergy Efficiency and COP Improvement of a CO2 Transcritical Heat Pump System by Replacing an Expansion Valve with a Tesla Turbine

2022

Self Cite

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The heat pump system has been widely used in residential and commercial applications due to its attractive advantages of high energy efficiency, reliability, and environmental impact. The massive exergy loss during the isenthalpic process in the expansion valve is a major drawback of the heat pump system. Therefore, the Tesla turbine exergy analysis in terms of transiting exergy efficiency is investigated and integrated with the transcritical heat pump system. The aim is to investigate the factors that reduce exergy losses and increase the coefficient of performance and exergy efficiency. The contribution of this paper is twofold. First, a three-dimensional numerical analysis of the supercritical CO2 flow simulation in the Tesla turbine in three different geometries is carried out. Second, the effect of the Tesla turbine on the coefficient of performance and exergy efficiency of the heat pump system is investigated. The effect of the rotor speed and disk spacing on the Tesla turbine power, exergy loss, and transiting exergy efficiency is investigated. The results showed that at a lower disk spacing, the turbine produces higher specific power and transiting exergy efficiency. In addition, the coefficient of performance (COP) and exergy efficiency improvement in the heat pump system combined with the Tesla turbine are 9.8% and 28.9% higher than in the conventional transcritical heat pump system, respectively.

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“…Sahar Taslimi et al evaluate the system performance of a CO2 two-phase ejector for the HPACS based on Grassmann exergy analysis and transiting exergy analysis. It was concluded that transiting exergy analysis is more suitable for a CO 2 two-phase ejector compared to Grassmann exergy analysis [23]. Honghyun Cho et al conducted an advanced exergy analysis on automotive air conditioning systems with R1234yf refrigerant.…”

Section: Introductionmentioning

confidence: 99%

Heating Performance Characteristics of an Electric Vehicle Heat Pump Air Conditioning System Based on Exergy Analysis

Tang

Guo

et al. 2020

Energies

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In this paper, a heat pump air conditioning system (HPACS) with refrigerant R134a based on the functional requirements of battery electric vehicle is designed and tested. Experiments were conducted to evaluate the effects of different ambient temperature, air flow rate of internal condenser, expansion valve (EXV) opening and compressor speed. The results demonstrate that air flow rate of internal condenser, EXV opening and compressor speed have important impact on heating capacity, compressor power consumption and coefficient of performance (COP) under several ambient temperatures. To verify the HPACS can also provide the heating capacity required by the battery electric vehicle cabin in cold climate, the system was also tested under a −5 °C ambient temperature, it was found that the heating capacity is 3.6 kW and the COP is 3.2, demonstrating that the system has high energy efficiency. In addition, heating process analysis of the HPACS under lower temperature is studied by exergy principle. The results indicate that compressor is the highest exergy destruction in all components, accounting for 55%. The percentage of exergy destruction in other components is about 28%, 12% and 5% for the expansive valve, condenser, and evaporator. Furthermore, air flow rate of internal condenser, ambient temperature and expansion valve opening have important impact on exergy destruction and exergy efficiency of the HPACS.

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Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Cited by 9 publications

References 29 publications

A unified deduction of the expressions of exergy and flow exergy

A unified deduction of the expressions of exergy and flow exergy

Exergy Efficiency and COP Improvement of a CO2 Transcritical Heat Pump System by Replacing an Expansion Valve with a Tesla Turbine

Heating Performance Characteristics of an Electric Vehicle Heat Pump Air Conditioning System Based on Exergy Analysis

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