Modelling and development of high-pressure-lift ejector for low temperature evaporators in R744 refrigeration systems for supermarkets

acceptedVersio

Modelling and development of high-pressure-lift ejector for low temperature evaporators in R744 refrigeration systems for supermarkets

acceptedVersio

Performance of integrated R744 packs part 2 : ejectors performance, a comparison of data-driven model from onsite measurements with rom model predictions

Rising concerns for climate change impacts along with the new legislation aimed at lowering emissions indicates the inevitable transition in the cooling/heating industry towards a more energy-efficient solution with minimal environmental impact. Integrated refrigeration, air condition and heat recovery solutions by CO2 (R744) packs are efficient solutions to high energy demanding building (supermarkets and hotels). Proven performance enhancement of Multi Ejector SolutionTM makes the R744 systems more energy efficient, especially in warm climates, compared to the most conventional synthetic refrigerant systems in food retail applications. Pilot installation in the frame of MultiPack, an EU funded project(Horizon 2020), provided a wide range of data, offering the possibility of evaluating the real performance of each ejector group: high pressure (HP), low pressure (LP), and liquid ejector(LE), by running the system in different operating modes. Analysis of the data indicated performance improvement of a system with ejector, on average a 35% lower energy consumption compared to baseline parallel compression R744 system without ejectors. The availability of mass flow measurement from 5 Coriolis mass flow meters on this pilot, enabled the possibility of comparison of mass flow rate in different evaporation temperatures. Data-driven models were used to estimate the performance of ejectors (Entrainment ratio) using onsite data from various operating modes and compare them with the simulated performance from CFD and lab measurements. Careful data pre-processing allows the data-driven model to predict the ejector performance using compressor mass flow rate models trained based on no ejector mode data derived from onsite measurements and compare with models validated by highly accurate lab experiments

Performance of integrated R744 packs part 2 : ejectors performance, a comparison of data-driven model from onsite measurements with rom model predictions

Rising concerns for climate change impacts along with the new legislation aimed at lowering emissions indicates the inevitable transition in the cooling/heating industry towards a more energy-efficient solution with minimal environmental impact. Integrated refrigeration, air condition and heat recovery solutions by CO2 (R744) packs are efficient solutions to high energy demanding building (supermarkets and hotels). Proven performance enhancement of Multi Ejector SolutionTM makes the R744 systems more energy efficient, especially in warm climates, compared to the most conventional synthetic refrigerant systems in food retail applications. Pilot installation in the frame of MultiPack, an EU funded project(Horizon 2020), provided a wide range of data, offering the possibility of evaluating the real performance of each ejector group: high pressure (HP), low pressure (LP), and liquid ejector(LE), by running the system in different operating modes. Analysis of the data indicated performance improvement of a system with ejector, on average a 35% lower energy consumption compared to baseline parallel compression R744 system without ejectors. The availability of mass flow measurement from 5 Coriolis mass flow meters on this pilot, enabled the possibility of comparison of mass flow rate in different evaporation temperatures. Data-driven models were used to estimate the performance of ejectors (Entrainment ratio) using onsite data from various operating modes and compare them with the simulated performance from CFD and lab measurements. Careful data pre-processing allows the data-driven model to predict the ejector performance using compressor mass flow rate models trained based on no ejector mode data derived from onsite measurements and compare with models validated by highly accurate lab experiments.acceptedVersio

Performance of integrated R744-packs part 1: compressor mass flow estimation based on data-driven models using analytical methods and actual field measurements

Rising concerns for climate change impacts along with the new legislation aimed at lowering emissions indicates the inevitable transition in the cooling/heating industry towards a more energy-efficient solution with minimal environmental impact. Integrated refrigeration, air condition and heat recovery solutions by CO2 (R744) packs are efficient solutions to high energy demanding building (supermarkets and hotels). Proven performance enhancement of Multi Ejector SolutionTM makes the R744 systems more energy efficient, especially in warm climates, compared to the most conventional synthetic refrigerant systems in food retail applications. Pilot installation in the frame of MultiPACK, an EU funded project (Horizon 2020), provided a wide range of data, offering the possibility of evaluating the real performance of each ejector group: high pressure (HP), low pressure (LP) and liquid ejector (LE), by running the system in different operating modes. Analysis of the data indicated performance improvement of a system with ejector, on average a 35% lower energy consumption compared to baseline parallel compression R744 system without ejectors. Availability of mass flow measurement, 5 Coriolis mass flow meters on this pilot, enabled the possibility of comparison of mass flow rate estimation based on data acquisition from compressors with actual measurement. Methods utilized include: Energy balance, volumetric displacement, manufacturer polynomials, and data-driven method. The comparison reveals the importance of compressor suction and discharge parameters for obtaining reliable results based on energy balance, volumetric displacement, manufacturer polynomials methods. The current study shows data-driven method performs well after enough training time with error bounded to 3% and 10 % on low and medium temperature level compressors, respectively

The Performance Analysis of an Integrated CO2 Refrigeration System with Multi-Ejectors Installed in a Supermarket

The field data from an integrated CO2 refrigeration system installed in a supermarket located north of the capital of Lisbon was analyzed. The goal was to demonstrate the effect and performance of multi-ejectors on a refrigeration system operating in a warm climate. The measurement results for the system with and without activating ejectors were compared. It was observed that the system with a multi-ejector operation had considerable performance superiority. The ejectors improved the cooling capacity of the medium temperature stage of the system by 17.4%. The system with active ejectors had 7.5% less total power consumption compared to the ejector off mode of the same system

Comprehensive experimental performance study on a small-capacity transcritical R744 vapour-compression refrigeration unit equipped with an innovative ejector:Etude expérimentale complète des performances d'un groupe frigorifique à compression de vapeur transcritique R744 de petite capacité équipé d'un éjecteur innovant

Ejector-equipped transcritical R744 condensing units are believed to lead to a low-to-zero commercial refrigeration sector. In order to overcome the persisting barrier to their wider adoption represented by the lack of an affordable ejector control technique, the novel pulse-width modulation (PWM) ejector, being low cost, simple and invulnerable to clogging was recently implemented. However, additional experimental evaluations are needed. Therefore, in this experimental work the performance of two PWM ejector-equipped transcritical R744 condensing units, i.e. with and without overfed evaporator, was carried out. The experimental assessment was implemented at the medium temperature (MT) of about -5°C, heat sink temperatures from 30°C to 40°C and compressor speeds from 40 Hz to 60 Hz.The outcomes obtained revealed that the PWM ejector can effectively control the high pressure in transcritical operating conditions, regardless of the selected heat sink temperature and compressor speed. In addition, at the same cooling capacity, the PWM ejector-equipped R744 system was found to permit energy savings between 7.0 % and 11.1 % without overfed evaporator and between 11.5 % and 16.3 % with overfed evaporator compared to the standard R744 unit (i.e. with vapour by-pass valve and without ejector), respectively. Finally, higher values of coefficient of performance (COP) were found to be offered by the PWM ejector compared with its today's available competitor