Department of Mechanical engineering

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Author: search.filters.author.Dasgupta, Mani SankarSubject: search.filters.subject.Supermarket

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Now showing 1 - 6 of 6
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    Waste heat utilization: energy and economic benefits from multi-ejector chiller sub-cooling R744 supermarket refrigeration systems
    (Elsevier, 2024-12) Dasgupta, Mani Sankar
    This study investigated the energy and economic benefits of a novel sub-cooling technique using a heat-driven multi-ejector chiller (HDEC) in R744 supermarket refrigeration systems. Two configurations were evaluated: a conventional booster system with HDEC (CBEC) and a parallel compression system with HDEC (PCEC). Among various natural refrigerants, R717 was identified as most suitable for the HDEC. Various multi-ejector combinations were examined to assess the potential for waste heat utilization and energy savings in the R744 refrigeration system. The CBEC system provided effective operation only at ambient temperatures above 31 °C, whereas the PCEC system was effective above 24 °C. Performance of the proposed configurations were compared with a conventional R744 booster system (CB) and a parallel compression system (PC) both devoid of HDEC. The PCEC system showed improvements in the coefficient-of-performance ranging from 4.2 % to 23.9 % at ambient temperatures between 28 °C and 40 °C compared to the baselines. In various warm-climatic zones, including India, the Middle East, Thailand, and the USA, energy savings of approximately 2.1 %–9.5 % were observed compared to the PC system. Economic analysis indicated a reasonable payback period of 2.1–2.7 years for the additional investment required for deploying the PCEC system in Phoenix.
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    Transcritical R744 supermarket refrigeration system integrated with a heat-driven ejector chiller
    (MDPI, 2025-03) Dasgupta, Mani Sankar
    The subcooling potential of a novel R717-based waste heat-driven multi-ejector chiller (HEC) integrated with an R744 refrigeration system was evaluated for use in supermarkets. The performance was compared with an R744 refrigeration system coupled to R718- and R600a-based HECs, an R744 system equipped with parallel compression (PC), and a standard R744 booster system (CB) in various warm and hot climatic locations. Integration of the R717-based HEC was found to improve the coefficient of performance by 3.7% at 27 °C to 12.1% at 45 °C compared to the R718, and by 1.6% at 27 °C to 7.6% at 45 °C compared to the R600a-based system. The energy-saving potential of the R717 system (6.2% to 9.4%) was also found to be higher than that of the R718 (0.7% to 2.8%) and R600a systems (2.5% to 6.6%). The use of the existing high-pressure controllers of the CB system was found to impose a relatively lower penalty on the system performance compared to the controllers of the PC system. Although the integration of the R718 system incurred a significantly lower additional investment, the recovery time of the R600a-based HEC (2.3–4.8 years) was found to be the shortest.
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    Thermodynamic Analysis of a Novel Dual-Ejector Multi-Compressor Transcritical-CO2 Refrigeration System for Supermarket Applications in Warm Climates
    (Springer, 2023-04) Dasgupta, Mani Sankar
    The thermodynamic analysis of a novel dual-ejector multistage compressor-based transcritical CO2 booster system for supermarket application in warm climatic conditions is presented in this paper. Dual-ejector flow-pressurization and flow-splitting at higher ambient temperatures are implemented to improve performance. The proposed system is compared with various previously published CO2 systems including B1 (Standard CO2 booster system), B2 (CO2 booster system with parallel compression), B3 (CO2 booster system with flooded LT evaporator), B4 (CO2 booster system with work recovery expander), B5 (CO2 booster system with parallel compression, flooded LT evaporator, work recovery expander) and also with multi-stage ejector systems. The performance of the proposed system is found superior. The COP of the proposed system has been found to be 32% higher than B5 and 26% higher than the multi-ejector systems.
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    Energy and advanced exergoeconomic analysis of a novel ejector-based CO2 refrigeration system and its optimization for supermarket application in warm climates
    (Elsevier, 2023-09) Dasgupta, Mani Sankar
    Supermarkets' high refrigeration and air-conditioning energy use increases their carbon footprint. Thus, this sector must be encouraged to innovate to increase efficiency, reduce emissions, and support UN Sustainable Development Goals 11 and 13. In this study, we present a novel dual-ejector based CO2 refrigeration configuration. Real component data from manufacturers are utilised to make the theoretical evidence proximate to a controlled experiment. Mathematical model of the ejector is validated using published experimental data with a maximum deviation of 9.23%. Energetic performance of the proposed system is contrasted with a dedicated mechanical subcooling based CO2 system (DMS) and is found to be superior by 41.97% to 35.38% for operation within ambient temperature 28 °C − 40 °C. The year-round performance of the proposed system for various warm ambient locations in India, UAE and Spain is evaluated. Compared to a conventional R404A direct expansion system, a substantial annual energy savings, upto 11.35% is observed. Advanced exergy and exergoeconomic analysis, carried out at 40 °C ambient, provides an estimate of the limits up to which the irreversibilities and associated costs can be avoided for high ambient operation. The high-stage compressor in the configuration is found to have the highest potential of reducing the irreversibility by 36.08% and cost rate by 23.24%. Extent of mutual interactions among various components are also investigated using mexogenous analysis. A multi-objective optimization using genetic algorithm is employed to optimize exergoeconomic performance. The exergetic performance of the optimized system is found to be 6% higher than DMS system.
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    Energetic and environmental performance evaluation of a R744 multi-ejector enhanced parallel compression system in high ambient temperature locations
    (International Institute of Refrigeration, 2018) Dasgupta, Mani Sankar
    Hydrofluorocarbons (HFCs) are widely used today in supermarket refrigeration and air conditioning applications, despite their environmentally deleterious nature. However, the EU F-Gas Regulation 517/2014 ambitiously aims at lessening the HFC consumption by 79% by 2030. A further drop in the intake and production of these man-made refrigerants on global perspectives is offered by the recent adoption of the Kigali Amendment to the Montreal Protocol. Efficient HFC-free technologies for supermarket heating, cooling and refrigeration, such as fully integrated R744 multi-ejector enhanced parallel compression systems, are already available for the European food retail industry. In this theoretical work the energy consumption and the carbon footprint of a multi-ejector R744 refrigeration solutionintegrated with the air conditioning (AC) equipment are contrasted with those of two separated HFC-based units. The investigation was based on an average-size supermarket located in various Southern Europe cities. The results revealed that reductions in the electricity intake as well as in the Total Equivalent Warming Impact (TEWI) up to respectively 24.9% and 74.8% can be achieved by adapting the refrigerating system layout to the peculiarities of R744.
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    CFD supported thermodynamic analysis of a CO2 pressure exchanger based refrigeration system for supermarkets
    (Elsevier, 2023-04) Dasgupta, Mani Sankar
    This manuscript presents a method to thermodynamically model a pressure exchanger device. CFD-based model of a rotary energy recovery device used in desalination process is developed and validated with published experimental data with a maximum deviation of 5.19%. The dimensionality of the validated model was reduced to investigate the potential of the pressure exchanger device operating with CO2 as the working fluid. Based on the data obtained from several numerical experiments, two correlations were developed, by means of non-linear regression analysis, for estimating the pressure lift generated by the device as a function of inlet velocity of high pressure fluid (0.5 – 3 m/s), rotor speed (500 – 3000 rpm), receiver pressure (25 – 40 bar) and gas-cooler pressure (90 – 120 bar). The correlations were found to be within acceptable error margin. The pressure lift generated by the pressure exchanger was found to be directly proportional to the inlet velocity of the high pressure fluid and inverse proportionality to the rotor speed. The developed correlations are used to evaluate the thermodynamic performance of a multi evaporator supermarket refrigeration system integrated with pressure exchanger to a conventional parallel compression system and a published multi-ejector system in the ambient temperature range of 30 to 40°C. The pressure exchanger based system was found to outperform the parallel compression as well as the multi-ejector system and demonstrate significant energy savings.