Raj Kumar

Bio: Raj Kumar is an academic researcher from YMCA University of Science and Technology. The author has contributed to research in topics: Exergy efficiency & Exergy. The author has an hindex of 8, co-authored 22 publications receiving 246 citations.

Soft computing based multi-objective optimization of Brayton cycle power plant with isothermal heat addition using evolutionary algorithm and decision making

Abstract: Display Omitted Two performance parameters are optimized through NSGA-II and MOEA/D.Optimal values of various input parameters are obtained.Significant improvement (about 15%) in thermal efficiency is reported.Suitability of heat exchanger for a particular application can be found.Effects of various input parameters on dual objectives are reported. An irreversible regenerative Brayton cycle model considering internal and external irreversibilities is developed in matrix laboratory (MATLAB) simulink environment and thermodynamic optimization based on finite time thermodynamic analysis along with multiple criteria is implemented. Evolutionary algorithms based on second version of non-dominated sorting genetic algorithm (NSGA-II) and multi-objective evolutionary algorithm based on decomposition (MOEA/D) are employed to optimize power output and thermal efficiency simultaneously where isobaric-side heat exchanger effectiveness (eH), isothermal-side effectiveness (eH1), sink-side effectiveness (eL), regenerator-side effectiveness (eR), and working medium temperature (T5) are taken as design variables. The optimal values of aforementioned design variables are investigated. Pareto optimal frontiers between dual objectives are obtained and the final optimal values of power output and thermal efficiency are chosen via LINMAP, fuzzy Bellman-Zadeh, Shannon's entropy and TOPSIS decision making approaches. The obtained results are compared and the best one is preferred. An improvement in thermal efficiency from 18.29% to 21.10% is reported. In addition to this, variations of different input parameters on the power output and thermal efficiency are conferred and presented graphically. With the goal of error investigation, the maximum and average errors for the obtained results are designed at last.

Multi-objective thermodynamic optimization of solar parabolic dish stirling heat engine with regenerative losses using NSGA-II and decision making

Abstract: The proposed work investigates optimal values of various decision variables that simultaneously optimize power output, net-work output and second law efficiency of solar driven Stirling heat engine with regenerative heat losses, conducting thermal bridging losses using evolutionary algorithm based on NSGA-II in Matlab simulink environment. Effects of design parameters as absorber temperature, concentrating ratio, radiative and convective heat transfers are included in the analysis. Pareto frontier is obtained for triple and dual objectives and the best optimal value is selected through four different decision making techniques viz. Fuzzy, Shannon entropy, LINMAP and TOPSIS. Triple objective evolutionary approach applied to the proposed model gives power output, net-work output and second law efficiency as (38.87 kW, 1.24 kJ, 0.3156) which are 18.19, 16.78 and 31.51% lower in comparison with reversible system. With the objective of error investigation, the average and maximum error of the obtained results are figured at last.

Recent advances in the development of biomass gasification technology: A comprehensive review

Abstract: Due to fast climate change and foreseen damage through global warming, access to clean and green energy has become very much essential for the sustainable development of the society, globally. Biomass based energy is one of the important renewable energy resources to meet the day to day energy requirements and is as old as the human civilization. Biomass gasification is among few important aspects of bioenergy for producing heat, power and biofuels for useful applications. Despite, the availability of vast literature, technological and material advancements, the dissemination of gasification technology could not overcome the critical barriers for the widespread acceptability over the conventional energy resources. This article presents a comprehensive review on the technical advancements, developments of biomass gasification technology and the barriers being faced by different stakeholders in the wide dissemination of the technology for day to day requirements of the society, followed by recommendations for policy makers to make this technology popular while serving the society.

Ejector refrigeration: A comprehensive review

Abstract: The increasing need for thermal comfort has led to a rapid increase in the use of cooling systems and, consequently, electricity demand for air-conditioning systems in buildings. Heat-driven ejector refrigeration systems appear to be a promising alternative to the traditional compressor-based refrigeration technologies for energy consumption reduction. This paper presents a comprehensive literature review on ejector refrigeration systems and working fluids. It deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance and all of the ejector refrigeration technologies, with a focus on past, present and future trends. The review is structured in four parts. In the first part, ejector technology is described. In the second part, a detailed description of the refrigerant properties and their influence over ejector performance is presented. In the third part, a review focused on the main jet refrigeration cycles is proposed, and the ejector refrigeration systems are reported and categorized. Finally, an overview over all ejector technologies, the relationship among the working fluids and the ejector performance, with a focus on past, present and future trends, is presented.

Overview of low GWP mixtures for the replacement of HFC refrigerants: R134a, R404A and R410A

Abstract: The current European F-gas regulation establishes restrictions in the use of fluoride refrigerants with a high global warming potential (GWP) in applications of refrigeration and air conditioning (RAC) systems. Moreover, a gradual limitation on the GWP weight of the fluoride refrigerants placed on the market is ongoing and will end with approximately one-fifth of today's offer. In this context, many of the RAC systems operate with refrigerants R134a, R404A, and R410A that have GWP values of 1300, 3943 and 2088, respectively, are being forced to be replaced by environmentally friendly alternatives, like hydrofluoroolefin (HFO) refrigerants and their mixtures with hydrofluorocarbons (HFC), which can be designed to present intermediate characteristics and become the ideal candidate many RAC applications. This work presents the most recent HFC/HFO/HC/R744 refrigerant mixture options for an alternative to the refrigerants mentiond above and compares their energetic and performance with the early developed mixture prototypes.