Department of Mechanical engineering

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Author: search.filters.author.Dasgupta, Mani SankarEnd date: 2019

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Now showing 1 - 10 of 37
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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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    Fuzzy controller development from information granules for a heat exchanger
    (NISCAIR, 2000-07) Dasgupta, Mani Sankar
    This paper discusses the experimental results of on-line fuzzy control of a heat exchanger unit. Fuzzy controllers are a class of model independent controllers. which use common sense logic, expressible in linguistic form and is more amenable to human way of decision-making, A collection of information granules, regarding the process under study, is documented first. Using the some, the steps of formation and justification of the fuzzy look-up table is demonstrated. An efficient fuzzy control is established using multiple look-up tables. These tables are further adapted to accommodate conflicting control demands of 'low overshoot' and 'small rise time', An algorithm for on-line table switching is also proposed.
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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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    Energetic and economic analysis of trans-critical CO2 booster system for refrigeration in warm climatic condition
    (Elsevier, 2017-08) Dasgupta, Mani Sankar
    The performance of five CO2 booster refrigeration systems is analysed and compared in this paper for supermarket application. The investigated configurations include a standard booster system, abbreviated as BC1, a booster system with parallel compressor (BC2), a booster system with flooded low temperature evaporator (BC3), a booster system with work recovery expander (BC4) and a booster with parallel compressor along with flooded low temperature evaporator and work recovery expander (BC5). Annual hourly averaged temperature variations at four prominent cities across the world are taken as case study. Simulation indicates advantage of the proposed system BC5 over BC1 configuration. Work recovery unit is found to have the highest potential in the annual energy savings in BC5, followed by parallel compressor and flooded evaporator. The maximum annual energy savings is found to be 22.16% for BC5 in New Delhi. Economic analysis reveals recovery time of less than four years for the additional investment made in BC5. The slope of recovery time is found steeper at lower tariff compared to that at higher tariff.
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    Transcritical CO2 Refrigeration System in Tropical Region: Challenges and Opportunities
    (IGI Global, 2015) Dasgupta, Mani Sankar
    Environmental concerns and enactments of Montreal and Kyoto Protocol for sustainable growth is a welcome impetus for researchers towards a quest for ecologically safe and natural refrigerants and cost effective designs of refrigeration systems. Carbon dioxide (CO2) is one such natural refrigerants that, although was abandoned once due techno-economic reason, has been receiving tremendous attention and is viewed as a strong candidate for long term alternative of synthetic refrigerants. The commercial success of CO2 as a refrigerant and its universal acceptance, however demands cost effective and widely accepted technology operable under various environmental conditions. In this chapter, the use of CO2 as refrigerant in trans-critical vapor compression system is discussed in detail along with its unique challenges associated with operating in tropical region. Further the opportunities for using these systems in tropical region with specific systematic modification are explored. Discussions on component design and system level performance analysis are also included in the chapter.
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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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    E-waste Management -- A Study in Perspective of Pilani
    (CURIE, 2010) Dasgupta, Mani Sankar
    E-waste management is an emerging issue, driven by the rapidly increasing quantities of complex end-of-life electronic equipments. E-waste contains large amount of both toxic and valuable substances. The international regulations, mainly under Basel convention, enforce a global ban on trans-border movements of E-waste but implementation of the same has its own difficulty due to lack of convergence in definition of E-waste followed by different governments, agencies and stake holders. Most E-waste in India ends up with slum based scrap dealers, who, in dangerous and hazardous working conditions take away resalable parts from this waste. The rest goes into landfills without proper treatment, posing serious ecological threat. Previous studies have shown region wise variation in E-waste handling pattern in India. Under this study, a comprehensive survey is carried out with scrap dealers in and around Pilani town of Jhunjhunu district of Rajasthan to gather information about time state of art. In the backdrop, comparison with the best practices in world is made to understand what is lacking in Pilani vis-à-vis India
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    Designing a modular rope climbing bot
    (IEEE, 2015) Dasgupta, Mani Sankar
    This paper discusses design of an autonomous rope climbing robot for identified industrial applications. Modified design goals are drawn up after analyzing the same from prior publications. A modular design with wheel based drive is conceptualized and suitable calculations are done to select drive motor, onboard power source etc. Limited laboratory based test is also carried out to establish suitability of the suggested drive mechanism. An embodiment is drawn out next for light weight modular construction satisfying the design goals. Salient design features are compared with published designs.
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    A Trans-critical CO2 Heat Pump System for Waste Heat Utilization in Warm Weather Condition Applied to a Milk Refrigeration Plant
    (Bepress, 2016) Dasgupta, Mani Sankar
    Based on field data from a medium scale ammonia based milk refrigeration plant located in northern part of India, a trans-critical CO2 based heat pump system is conceptualized to utilize the waste heat from the plant to improve overall coefficient of performance. Year round plant operating data is collected. The plant handles between 0.1 to 0.15 million liters of milk and milk products daily. It maintains two cooling chambers, one at 4°C and the other at -10°C. Every ten days it is required to replenish a 5000 liter tank with ground water for evaporative cooling of the system. Up-stream and down-stream processes in the milk processing plant utilizes a coal fired boiler system which also uses ground water. In this study, the condenser of the ammonia based refrigeration system is coupled with the evaporator of the proposed CO2 trans-critical heat pump system which is maintained at 25°C round the year. The heat pump delivers heat at about 70°C to pre heat the boiler feed water available in temperature range 22-25°C round the year. Augmentation of the proposed CO2 system is able to reduce coal consumption by utilizing the waste heat from the ammonia system at the same time reduce ground water utilized by eliminating evaporative cooling. The proposed heat pump system has encouraging COP and is designed to be largely independent of variation in ambient temperature. Based on field data, a comparative study is carried out using thermodynamic & thermo-economic analysis for a duration of one year to establish feasibility of the proposed system
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    Evaluating Applicability of a Scroll Expander for CO2 Refrigeration System at Warm Climate
    (World Scientific, 2017) Dasgupta, Mani Sankar
    Performance of a trans-critical CO2 refrigeration cycle equipped with a scroll work recovery expander is investigated using a semi-empirical model of the scroll, for high ambient temperature application. Maximum isentropic efficiency of 61% is obtained, for a pressure ratio of about 3.7 for the scroll expander. Simulation results obtained are further validated against the reported experimental results. It is also observed that, about 20% of the total energy consumed can be recovered with the help of scroll expander during trans-critical operation. Based on year-round ambient temperature data, at New Delhi (India), an economic analysis is carried out for installation of work recovery scroll system. Total payback period (PBP) for scroll expanders of various capacities are also determined. It is noted that the PBP of scroll expander is about 1 to 2 years or less, which is encouraging. Total Equivalent Warming Impact (TEWI) of the system is compared with that of a conventional trans-critical CO2 refrigeration system and system running on low global warming potential (GWP) hydrofluoroolefin (R1234yf) refrigerant. Trans-critical CO2 system along with work recovery scroll expander appears justified as the same has about 15% lower TEWI compared to conventional trans-critical CO2 system but is 50% more than R1234yf system.