BITS Faculty Publications

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    Thermodynamic Analysis of Vapor Compression Refrigeration System for Aircraft with Refrigerant R134a
    (Journal of Aerospace Sciences and Technologies, 2016) Ranganayakulu, Chennu
    The Environmental Control System (ECS) for a typical fighter aircraft is used for cabin cooling and pressurization, demisting operations, and for avionics cooling. Most of the passenger and fighter aircrafts use Bleed-Air Cycle for ECS. In this paper a new ECS called All Electric Environmental Control System (AEECS) is presented which works on Vapor Compression Refrigeration System using ram air as medium. It is called a power optimized system. The sizing of the system is based on the heat load calculations of the cabin and avionics for different flight conditions. A generalized software program is developed for evaluating system performance which includes key results regarding air compressor capacity, thermodynamic properties of refrigerants and Vapor Compression Refrigeration System. The AEECS is found to reduce the power requirement of the system to 80 kW compared to the Bleed Air Cycle ECS which requires a power of 0.8 MW to run the system. The results are presented in the form of graphs.
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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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    Thermodynamic analysis of trans-critical CO2 refrigeration cycle in Indian context
    (IJSTA, 2015) Dasgupta, Mani Sankar
    The coefficient of performance for CO2 based trans-critical system is lower at high ambient temperature regions like India due to higher energy required for compression to a high temperature beyond critical point. This paper presents thermodynamic analysis of a basic trans-critical CO2 refrigeration cycle. Further, the basic cycle is modified for two different configurations incorporating parallel compression and inter-cooling. Use of parallel compression and inter-cooling in cycle configuration are two of the most promising cycle modifications for improving the performance of trans-critical CO2 refrigeration systems operating at high ambient temperatures. Simulation results show that parallel compression configuration is more effective. The maximum improvement in COP obtained is about 25% for parallel compression configuration. Also, the operating pressure of gas cooler is found lower for parallel compression configuration.
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    Carbon dioxide to bio-fuels by mixed and pure microbial cultures isolated from activated sludge: relative evaluation of CO2 fixation, biodiesel production, and thermodynamic analysis
    (Wiley, 2019-08-31) Gupta, Suresh; Raghuvanshi, Smita; Mishra, Somesh
    In the present work, the CO2(g) bio-mitigation potential (15% [v/v]) of a mixed microbial population, Enterobacter cloacae and Pseudomonas putida, is thermodynamically assessed and compared at different Fe(II) concentrations (energy source). CO2(g) removal efficiency values are evaluated on per-day basis for all cultures and found maximum for the mixed microbial population. Approximate material balance and thermodynamic assessment of the CO2(g) bio-mitigation studies have revealed that among all cultures, the mixed microbial population shows the highest actual CO2 utilization efficiency (R.RCO2) of 57.67 (±0.04)%. Leachate (biomass + cell free supernatant) obtained from CO2 bio-mitigation batch studies were analyzed using FTIR and gas chromatography–mass spectroscopy. The results obtained have shown the presence of fatty acids and hydrocarbons in considerable amounts. The fatty acids obtained from cultures have shown the presence of a carbon chain length in the range of C7–C25, which makes it a potential source of biodiesel. Biodiesel yields of 91.55%, 77.49%, and 38.69% were obtained for the mixed microbial population, E. cloacae and P. putida. The hydrocarbons obtained from all the microbial cultures were found to have a carbon chain length in the range of C9–C32 and comprised saturated and unsaturated groups, which make them comparable to light oil.
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    Investigation on CO2 bio-mitigation using Halomonas stevensii in laboratory scale bioreactor: Design of downstream process and its economic feasibility analysis
    (Elsiever, 2018-03) Gupta, Suresh; Raghuvanshi, Smita; Mishra, Somesh
    In the present study, H. stevensii was cultivated on a semi-continuous mode in a laboratory scale bio-reactor using CO2(g) [15% (v/v)] as carbon source and thiosulfate (S2O32−) as an energy source for the total duration of three days. Approximately, 100% CO2(g) removal from gaseous phase was achieved. Leachate obtained was subjected to different downstream bio-processing strategies. Biomass harvesting using filtration and recovery of metabolites without cell disruption using solvent extraction from wet biomass was observed as the best downstream processing strategy. Qualitative analysis of products was carried out using gas chromatography and mass spectroscopy (GC–MS) and their results have indicated fatty alcohols (C8–C27) as primary metabolites. Fourier transform infrared spectroscopy (FTIR) analysis, approximate material balance and thermodynamic analysis have confirmed the intracellular assimilation of CO2(g) as HCO3− and its metabolization into fatty alcohols. Economic feasibility of the process has suggested that the developed downstream process has the capability to replace coconut oil based process for the production of fatty alcohols (C12–C14) and it can be utilized for the production of dodecanol as compared to the tetradecanol.