BITS Faculty Publications

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    Selection of Best Suitable Eco-Friendly Refrigerants for HVAC Sector and Renewable Energy Devices
    (MDPI, 2022-09) Bhattacharyya, Suvanjan
    This paper investigates the selection of the best suitable eco-friendly organic and in-organic refrigerants for heating, ventilation, and air conditioning (HVAC) and renewable energy devices. Inorganic and organic refrigerants are used to cool renewable energy devices, such as solar cells, photovoltaics, and electronic devices. Owing to the renewable energy community’s importance, development in this area has rapidly improved over the past few years. R134a, R404, and R717 have become the most used refrigerants in the HVAC sector and supermarkets across the globe for both cooling and frozen food refrigeration. R134a and R404A have two significant drawbacks: (a) they do not attain optimal energy efficiency in many applications, and (b) they have a large global warming potential (GWP). Hence, optimization experiments were performed to select low global potential refrigerants for replacing R134a and R404A from the HVAC sector and supermarkets using multi-criteria making (MCDN) tools. The techniques used for investigation involved (i) the technique for order of preference by similarity to ideal solution (TOPSIS), (ii) evaluation based on distance from average solution (EDAS), and (iii) multi-objective optimization based on ratio analysis (MOORA). The assessment criteria of optimization involved (i) thermo–physical properties of refrigerants, (ii) environmental aspects of refrigerants, and (iii) economic status of refrigerants. Out of 27 refrigerants chosen for the study, R290 (PROPANE) aced the selection by all the three techniques, i.e., TOPSIS, EDAS, and MOORA, with assessment scores of 0.6056, 0.6761, and 0.466, respectively. R41 (FLUOROMETHANE) is the least preferred refrigerant by EDAS (assessment score—0.3967) and MOORA, while R407C is the least preferred by TOPSIS (assessment value—0.5123). The likelihood of making a bad refrigerant decision may be reduced by the effective evaluation of the MCDM analysis. In conclusion, the suggested MCDM technique provides a practical tool and systematic way for reducing the number of options and may be utilized to identify the ideal refrigerant.
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    Evaluation applicability of trans-critical CO2 refrigeration system using field data of an ammonia based plant
    (IIR, 2016) Dasgupta, Mani Sankar
    The study evaluates the potential of a trans-critical CO2 refrigeration system as replacement of an ammonia system in a milk refrigeration plant for a warm climate condition in northern India where the annual range of temperature is 48ºC to -2 ºC. Twenty-four months of field data from the ammonia based plant is collected. An ideal thermodynamic model of the same is built and operated with field data and the performance is compared. A co-relation factor is developed that relates ideal and actual performance encompassing the practical consideration that contribute towards reduction of plant performance from ideal. The performance is next compared with that of hypothetical replacement plant based on CO2 transcritical cycle with booster system, weighing up practical consideration. A few possible COP improvement strategies are also evaluated.
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    Investigation of effect of suction nozzle pressure drop and degree of sub-cooling on co2 transcritical ejector system
    (Begell House, 2017) Dasgupta, Mani Sankar; Yadav, Shyam Sunder
    A two-phase ejector is often used to improve the performance of a CO2 transcritical refrigeration system, such systems are also, mostly equipped with an internal heat exchanger. Any effect on performance due to suction nozzle pressure drop (SNPD) is generally neglected for theoretical studies using constant pressure mixing model. A few authors, in the recent past, have highlighted the effect of SNPD. A detailed investigation of effect of SNPD as well as sub-cooling on the performance parameters like pressure recovery, ejector efficiency, entrainment ratio and overall COP of the system are presented here. Optimized ejector SNPD values are determined for maximizing COP across a wide range of operating conditions. COP increment upto 4.95% is observed at optimized SNPD condition. Further, the effect of degree of sub-cooling on cycle parameters is studied and optimum degree of sub-cooling for COP improvement for a range of operating conditions is also determined.
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    Annual energy and economic performance assessment of transcritical R744 supermarket refrigeration systems powered by an organic Rankine cycle
    (Elsevier, 2023-08) Dasgupta, Mani Sankar
    In this work the annual and economic performance of a transcritical R744 booster supermarket refrigeration system integrated with an organic Rankine cycle (ORC) was investigated. The results were compared to those of a conventional R744 booster supermarket refrigeration system (i.e. without ORC) in nine different locations worldwide. The benefits from overfeeding the medium temperature (MT) evaporators were also studied. It was found that the ORC can be used at outdoor temperatures above 27 °C. Also, it was observed that the proposed systems offer energy savings from 6 % to 16 % in warm and hot locations, such as New Delhi (India), Phoenix (USA), Bangkok (Thailand) and Riyadh (Saudi Arabia). The payback period of the additional investment associated with the ORC was equal to about 3.5 years in Athens (Greece) and less than 1.5 years in New Delhi, Phoenix, Bangkok and Riyadh.
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    Energetic, environmental and economic assessment of multi-evaporator CO2–NH3 cascade refrigeration system for seafood application
    (Springer, 2022-09) Dasgupta, Mani Sankar
    Refrigeration plays a vital role in ensuring quality and safety of seafood. In a tropical country like India, the seafood industry has a relatively larger cooling load throughout the supply chain due to higher temperature differences between ambient and chilled seafood. The cooling demands in a seafood processing plant are typically at four different temperature levels. Supply of chilled water at 2 °C, ice at − 5 °C, cold storage maintained at − 25 °C, and a plate or blast freezer at − 40 °C. Commonly, a multi-evaporator multi-stage refrigeration system with refrigerants like R22, R404A, or NH3 are used in India. However, R22 and R404A have harmful effects on the environment due to their high global warming potential. This study proposed an all-natural multi-evaporator CO2–NH3 cascade refrigeration system (CRS). For comparison, the refrigeration demands in a surimi (seafood) processing and storage plant located in Mumbai were utilized. The study revealed that CO2–NH3 CRS has the highest COP and the lowest annual energy consumption followed by conventional NH3 system. CO2–NH3 CRS exhibited 6.2%, 12.3% and 3.2% less energy consumption compared to R22, R404A, and NH3 systems, respectively. Similarly, CO2–NH3 CRS also showed the lowest total equivalent warming impact which is 26.8%, 44.3% and 3.2% less compared to R22, R404A, and NH3 systems, respectively. Furthermore, CO2–NH3 CRS also presented relatively better results in terms of annual cost rate and life cycle cost.
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    Thermal and economic analysis of an on-board compensatory refrigeration system for small fishing boats
    (Begell House, 2019) Dasgupta, Mani Sankar
    In this work, the feasibility of a novel low capacity on-board compensatory refrigeration system is proposed for small motorized boats that are used by fisherman in western coast of India for fishing. The proposed refrigeration unit will counteract the heat ingress into the iced compartments in the boat and ensure low temperature for preservation of fish quality for the average duration of a fishing trip of 10 days. A heat transfer model of the storage compartment is developed considering parameters such as ambient condition, compartment openings, product removal/loading, container wall insulation, water drainage etc. Required refrigeration load for the proposed retrofitted compensatory refrigeration system is estimated. Feasibility of a vapour absorption refrigeration (VAR) system powered by exhaust heat from the diesel engine is analysed. Market price of such a system is also estimated and payback period is computed.
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    Integrated supermarket refrigeration for very high ambient temperature
    (Elsevier, 2018-12) Dasgupta, Mani Sankar
    This paper analytically investigates and compares the performance of a proposed ‘all-natural’ NH3/CO2 cascaded booster system to a conventional R404A direct expansion system as well as to an ‘all-CO2’ system with multi-ejector unit and flooded evaporator. Performance comparison is made based on the annual combined COP and Life Cycle Climate Performance (LCCP) for operation in selected cities of Middle East and India. Our results show that in extreme warm climate, the energy efficiency of the proposed configuration exceeds that of all-CO2 configuration by a maximum of about 12.23% and the total emissions are lower by up to 11.20%. However, the all-CO2 multi ejector system performs better in cold and mild warm climate. In the NH3/CO2 cascade, the high temperature NH3 system can be designed to be isolated from the accessible locations of the supermarket. The work presented is expected to help adoption of natural refrigerants such as CO2 and NH3 for commercial application in extreme warm climate conditions prevailing in many cities of Middle East and India.
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    ReValue project Report – D1.3: Report on energy efficient refrigeration systems - Surimi case
    (SINTEF, 2020) Dasgupta, Mani Sankar; Routroy, Srikanta
    This report is a part of WP1 in the Revalue project and it presents the findings from research on energy-efficient and environment-friendly refrigeration system for Surimi processing and storage in warm ambient temperatures. During 2017-18, India exported about $17.6 million worth of surimi and it has good potential for further growth. The majority of surimi processing industries in India are located along the western coast and for this study, operational data from one such industry located in Mumbai has been used in this study. A surimi supply chain has substantial cooling demand at various temperatures, ranging from -40 to 8 ºC, from harvesting to the final product. Conventionally, a single NH3 refrigeration system with multiple evaporators is employed to meet the cooling demands in a processing plant, including the cold storage. However, due to several challenges faced by the surimi industry in India (Dasgupta et al, 2019), the plants operate in part-load conditions for a major part of the year and the overall efficiency is rather low. To improve energy efficiency, a smaller capacity plant is recommended and a CO2-NH3 cascaded refrigeration system (CRS) is proposed. In the cascade system, CO2 is used in low temperature circuit and NH3 in high temperature circuit, which also reduces the contamination hazard of food from NH3. Modelling and analysis of various CO2-NH3 configurations were conducted, and a CRS system having a COP of 6.2% higher than the conventional NH3 system was identified.