Akhilesh Arora

Performance analysis of a transcritical N2O refrigeration cycle with vortex tube

ABSTRACT In the present study, vortex tube is used in transcritical vapour compression cycle as expansion device to improve the coefficient of performance (COP). The thermodynamic analysis has been performed using nitrous oxide in transcritical cycle with vortex tube (TCVT) and its results are compared with those of a transcritical cycle with expansion valve (TCEV). The evaporator and the gas cooler temperatures have been varied between −55°C and 5°C and between 35°C and 60°C, respectively, for the analysis. The COP of the TCVT improves by 1.72–27.01% compared to TCEV. A decrease in evaporator temperature and an increase in gas cooler exit temperature result in a decrease in COP. The increase in cold mass fraction brings a negligible increase in maximum COP. The performance comparison of N2O and CO2 in TCVT shows that maximum cooling COP for N2O is higher than for CO2, but the optimum pressure required for N2O is lower than for CO2.

Grey relational analysis coupled with principal component analysis for optimization of the cyclic parameters of a solar-driven organic Rankine cycle

Purpose n n n n nThe purpose of this paper is to investigate the effect of four controllable parameters (fuel mixture, evaporation bubble point temperature, expander inlet temperature and condensation dew point temperature) of a solar-driven organic Rankine cycle (ORC) on the first-law efficiency, the exergetic efficiency, the exergy destruction and the volume flow ratio (expander outlet/expander inlet). n n n n nDesign/methodology/approach n n n n nNine experiments as per Taguchi’s standard L9 orthogonal array were performed on the solar-driven ORC. Subsequently, multi-response optimization was performed using grey relational and principal component analyses. n n n n nFindings n n n n nThe results revealed that the grey relational analysis along with the principal component analysis is a simple as well as effective method for solving the multi-response optimization problem and it provides the optimal combination of the solar-driven ORC parameters. Further, the analysis of variance was also employed to identify the most significant parameter based on the percentage of contribution of each cyclic parameter. Confirmation tests were performed to check the validity of the results which revealed good agreement between predicted and experimental values of the response variables at optimum combination of the input parameters. The optimal combination of process parameters is the set with A3 (the best fuel mixture in the context of optimal performance is 0.9 percent butane and 0.1 percent pentane by weight), B2 (evaporation bubble point temperature=358 K), C1 (condensation dew point temperature=300 K) and D3 (expander inlet temperature=370 K). n n n n nResearch limitations/implications n n n n nIn this research, the Taguchi-based grey relational analysis coupled with the principal components analysis has been successfully carried out, whereas for any optimized solution, it is required to have a real-time scenario that may be taken into consideration by the application of different soft computing techniques like genetic algorithm, simulated annealing, etc. The results generated are purely based on theoretical modeling, and, for further research, experimental analyses are required to consolidate the generated results. n n n n nOriginality/value n n n n nThis piece of research work will be helpful to users of solar energy, academicians, researchers and other concerned persons, in understanding the importance, severity and benefits obtained by the application, implementation and optimization of the cyclic parameters of the solar-driven ORC.

Energy and Exergy Analysis of Organic Rankine Cycle Using Alternative Working Fluids

The present study is based on parametric investigation in terms of thermal efficiency, exergetic efficiency and exergy destruction with the help mathematical modeling on different ORC models using different fluids. The Thermal efficiency of ORC model of Saturated, Trilateral is compared by using working fluids such as (HFO-1234yf,HFC-134a,HFC-245fa,Ethanol,Iso-pentane by varying expander inlet temperature (30- 160⁰C),at fixed condensation temperature(30⁰C) assuming fixed expander isentropic efficiency ( =0.75) and fixed isentropic pump efficiency( =0.60). The Thermal efficiency as well as exergetic efficiency has been observed best for theHFO-1234yf and found nearly close with HFC-134a. HFO-1234yf has good potential for working fluid for ORC application for low to medium temperature. It has zero global warming potential (GWP), zero Ozone layer depletion (ODP) and very Low evaporation Temperature. This paper provides a basis to compare the thermal and exergetic efficiency for various working fluids and exergy destruction in various component such as Expander, Evaporator,Condenser,Pump for saturated and Trilateral cycle when used with R-1234yf as working substance.

Thermodynamic analysis of low-grade solar heat source-powered modified organic Rankine cycle using zeotropic mixture (Butane/R1234yf)

ABSTRACT This paper communicates detailed energy and exergy analysis of low-grade energy resource of solar-powered organic Rankine cycle (ORC) integrated with both the internal heat exchanger and open feed water heater, ORC incorporated with the internal heat exchanger, with open feed water heater and basic ORC, respectively. Results indicate that highest first law efficiency (11.9%), exergetic efficiency (51.88%) and lowest exergy destruction (1749u2009kW) are obtained for ORC integrated with both internal heat exchanger and open feed water heater among other considered ORCs. Moreover, zeotropic mixture (butane/R1234yf) shows better first law and exergetic efficiency and lower exergy destruction than pure fluid.

Performance characteristics of a Two- stage Transcritical N2O Refrigeration Cycle with Vortex Tube

ABSTRACT The thermodynamic analysis has been presented in this article using nitrous oxide as the refrigerant in a two-stage transcritical cycle with the vortex tube (TSTCVT) instead of the expansion valve and its results are compared with the two-stage transcritical cycle with the expansion valve (TSTCEV). The evaporator and the gas cooler temperature ranges in both the cycles have been considered between −55°C to 5°C and 35°C to 60°C for the analysis. Gas cooler and intercooler pressures are simultaneously optimised to obtain the maximum cooling coefficient of performance (COP). The COP of the TSTCVT improves by 1.97–27.19% in comparison to TSTCEV. A decrease in evaporator temperature and an increase in gas cooler exit temperature reduce the COP of TSTCVT. The comparison of refrigerants N2O and CO2 in TSTCVT shows that N2O exhibits higher cooling COP, higher second law of efficiency and lower optimum gas cooler pressure under the considered operating conditions.

Exergy analysis of the transcritical N2O refrigeration cycle with a vortex tube

ABSTRACT In this article, a comparative study is presented for the transcritical cycle with expansion valve (TCEV) and transcritical cycle with vortex tube (TCVT) mainly based on the second law of thermodynamics. Natural refrigerant nitrous oxide (N2O) is used in both the cycles for analysis. The evaporator and gas cooler temperatures are varied from −55°C to 5°C and 35°C to 60°C, respectively. The effects of various operating and design parameters on the optimum heat rejection pressure, coefficient of performance (COP), exergy loss (irreversibility), and the exergetic efficiency are studied. Exergy analysis of each component in TCEV and TCVT is performed to identify the amount and locations of irreversibility. It is observed that the use of the vortex tube in place of the expansion valve reduces the total exergy losses and increases the exergetic efficiency as well as COP. The exergetic efficiency and COP of the TCVT are on average 10–12% higher compared to TCEV for the considered operating conditions. The computed values of the exergetic efficiency for TCVT using refrigerant N2O are the highest at an evaporator temperature of −55°C, and the corresponding values of exergetic efficiency and exergy losses varies between 25.35% and 15.67% and between 74.65% and 84.33%, respectively. However, COP at the same evaporator temperature of −55°C varies between 0.83 and 0.51. Furthermore, the optimum heat rejection pressure in TCVT is lower compared to that in TCEV. The results offer significant help for the optimum design and operating conditions of TCVT with refrigerant N2O.

Thermo-economic and multiobjective optimization of saturated and superheated organic Rankine cycle using a low-grade solar heat source

This paper presents detailed energy and exergy analysis and comparison of low-grade solar heat source powered superheated and saturated organic Rankine cycle (ORC) using zeotropic mixture butane/R1234ze. The required expression to evaluate the power output, first law efficiency exergetic efficiency, exergy destruction, and required heat exchangers area are coded in Matlab 2015a interfaced with REFPROP 9.0. Moreover, saturated and superheated ORCs are further optimized by genetic algorithm by selecting exergetic efficiency and product of overall heat transfer coefficient and heat exchanger area. It is observed that superheated ORC exhibits better net power output, first law, and exergetic efficiency, lower exergy destruction, and poorer economy than saturated ORC. Further, the performance of saturated ORC is increased by 34.02% and that of superheated ORC by 17.06% by the multiobjective genetic algorithm.

Thermodynamic and multi-objective optimisation of solar-driven Organic Rankine Cycle using zeotropic mixtures

ABSTRACT This paper communicates the performance of low-grade solar heat source powered Organic Rankine Cycle (ORC). To investigate the system performance, first law and exergetic efficiencies, power output are evaluated and compared for zeotropic mixtures of (iso)butane/(iso)pentane and cyclohexane/R123. The results indicate that there exists an optimal mass fraction for which energy and exergetic efficiencies, and power output are maximum corresponding to a given value of expander inlet temperature compared with pure fluids. However, the specific volume flow ratio of the expander is higher for zeotropic mixtures; which results in a lower economy of mixtures than pure fluids. The use of an internal heat exchanger in the system improves cycle performance. Moreover, the multi-objective genetic algorithm further improves the performance of ORC and exhibits better exergetic efficiency 51–57% and 0–14.09% reduction in lower expander-specific volume flow ratio (v 6/v 5) than thermodynamically optimised ORC.

Energy, exergy, environment and economic analyses and optimization of two-stage absorption–compression combined refrigeration system

In the present paper, integration of a two-stage absorption refrigeration system with a compression refrigeration system is proposed for utilizing low-temperature heat and reducing electric energy consumption. The proposed system is analyzed and compared with vapor compression system from the viewpoint of energy, exergy, environment and economics. The proposed system reduces the electricity consumption by 89.3% and CO2 emission from 112.6 to 12.1xa0ton/year. The size and cost of the system are determined by designing the heat exchangers. The optimization is also performed with the objective of minimizing the annual cost of plant operation which includes fuel exergy cost, initial investment and maintenance cost and environmental damage cost due to CO2 emission. The annual cost of its operation is 21.6% less than equivalent vapor compression refrigeration system which is further reduced by 18.2% through system optimization.