Multi-Objective Optimization of a Solar Combined Power Generation and Multi-Cooling System Using CO2 as a Refrigerant

This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by solar energy. Carbon dioxide is used as a refrigerant. A parabolic trough collector (PTC) is employed to collect solar radiation and convert it into thermal energy. The system includes a supercritical CO2 power system for power production and an ejector refrigeration system with two ejectors to provide cooling at two different evaporating temperatures. The CMCP system is simulated hourly with weather conditions for Tunisia. The PTC mathematical model is used to calculate the heat transfer fluid outlet temperature and the performance of the CMCP system on a specific day of the year. A 1D model of an ejector with a constant area is adopted to evaluate the ejector performance. The system’s performance is evaluated by an energetic and exergetic analysis. The importance of the system’s components is determined by an exergoeconomic analysis. The system is modeled using MATLAB software. A genetic algorithm is used for multi-objective optimization to determine the best values and solutions for the system’s design parameters. The optimal energy and exergy efficiencies were found to be 13.7 percent and 37.55 percent, respectively, and the total product unit cost was 31.15 USD/GJ

Multi-Objective Optimization of a Solar Combined Power Generation and Multi-Cooling System Using CO₂ as a Refrigerant

This paper proposes a new combined multi-cooling and power generation system (CMCP) driven by solar energy. Carbon dioxide is used as a refrigerant. A parabolic trough collector (PTC) is employed to collect solar radiation and convert it into thermal energy. The system includes a supercritical CO2 power system for power production and an ejector refrigeration system with two ejectors to provide cooling at two different evaporating temperatures. The CMCP system is simulated hourly with weather conditions for Tunisia. The PTC mathematical model is used to calculate the heat transfer fluid outlet temperature and the performance of the CMCP system on a specific day of the year. A 1D model of an ejector with a constant area is adopted to evaluate the ejector performance. The system’s performance is evaluated by an energetic and exergetic analysis. The importance of the system’s components is determined by an exergoeconomic analysis. The system is modeled using MATLAB software. A genetic algorithm is used for multi-objective optimization to determine the best values and solutions for the system’s design parameters. The optimal energy and exergy efficiencies were found to be 13.7 percent and 37.55 percent, respectively, and the total product unit cost was 31.15 USD/GJ

Simulation numérique de l’écoulement dans un éjecteur supersonique

International audience<p&gtCe travail présente une étude sur l’analyse de l’écoulement au sein de l’éjecteur et plus particulièrement du processus de recompression par chocs qui prend place le long de la tuyère secondaire. Les simulations numériques sont réalisées à l’aide du logiciel de CFD ANSYS- FLUENT.</p&gt<p&gtLes deux modes de fonctionnement de l’éjecteur (sans et avec flux induit) sont étudiés pour différentes valeurs de la pression génératrice primaire P1 comprises entre 2 et 5 bar. Dans un premier temps, les distributions axiales de la pression sont analysées. Ensuite, la structure de chocs est visualisée afin d’appuyer certaines conclusions. Des tests sur le choix du modèle de turbulence le mieux adapté en termes de représentation correcte des phénomènes physiques ont été réalisés. Il a été montré que le modèle k-oméga-SST semblait le mieux adapté pour prédire la structure de choc. Les résultats numériques obtenus à partir des simulations 2D axisymétriques sont très encourageants. Les performances de l’éjecteur en termes d’aspiration et d’entrainement de flux secondaire ont été déterminées numériquement et comparées aux données expérimentales. L’influence de la distance entre la section de sortie de la tuyère primaire et la section d’entrée de la chambre de mélange de l’éjecteur (facteur géométrique NXP) sur les performances de l’éjecteur a été ensuite analysée.</p&gt<p&gtAbstract – This paper describes the investigation of the flow within a supersonic ejector and more particularly the analysis of the shock recompression process which takes place along the secondary nozzle. Numerical simulations are performed using the CFD package Ansys-Fluent. The two operating modes of the ejector (without and with induced flow) are studied for different values of the primary stagnation pressure P1 between 2 and 5 bar. The impact of the distance between the outlet section of the primary nozzle and the inlet section of<br&gt</p&g

Experimental study of a two-phase ejector for CO2 transcritical refrigeration system

The geometry and operating parameters have an important influence on the performance of ejectors. The improvement of the refrigeration cycle performance and the design of the ejectors for the compression energy recovery requires a detailed analysis of the internal ejector working characteristics and geometry. To this aim, an experimental investigation of an ejector refrigeration system is conducted to determine the effect of the most important ejector dimensions on ejector working characteristics and system performance. Different dimensions of ejector components are tested. The influence of the ejector’s geometrical parameters on the system performance was analysed. The experiments with respect to the variation of ejector geometry such as the motive nozzle throat diameter, the mixing chamber diameter and the distance between the motive nozzle and diffuser were carried out. There exist optimum design parameters in each test. The experimental results show that the performance (entrainment ratio and a compression ratio of the ejector) increases significantly with the position between the primary nozzle and the mixing chamber. A maximum entrainment ratio of 57.3% and a compression ratio of 1.26 were recorded for the different parameters studied. The results obtained are consistent with experimental results found in the literature