Irreversibility Rate Research Articles

Advanced exergy analysis and risk estimation of novel NH3-H2O and H2O-LiBr integrated vapor absorption refrigeration system

In present work, thermodynamic potential and risk estimation of NH3-H2O and H2O-LiBr integrated vapor absorption refrigeration system (IVARS) have been reported. The performance of IVARS has also been compared with a conventional vapor absorption refrigeration system (VARS) for the same cooling duty. Comparative results show that the proposed configuration can maintain evaporator temperature of −30 °C with 92.1 °C generator temperature, which is 51.6 °C lower than that required in a conventional VARS. Further, coefficient of structural bonds (CSB) values predict that the solution heat exchanger of NH3-H2O subsystem (maximum CSB value 5.28) is the most sensitive heat exchanger; whereas, generator of H2O-LiBr subsystem (minimum CSB value 0.38) is the most efficient heat exchanger of IVARS, but contrary to this, their involvement in total irreversibility is merely 6.7% and 18.6% respectively. Based on 80/20 principle, Pareto chart suggests the designer to focus on improving the efficiency parameter of generators and absorbers of IVARS due to their significant contribution in total irreversibility rate. Hence, advanced exergy analysis has been performed to overcome this dilemma. Interestingly, 19.8% of the irreversible loss in IVARS is found avoidable and can be eradicated by modifying the efficiency parameters of different components of IVARS and 93.7% of irreversibility rate is due to the selected operating parameters of components itself. Moreover, the total annual risk due to toxic fluid ‘ammonia’ in NH3-H2O absorption subsystem is estimated to be US$ 996.6/year and the condenser of NH3-H2O is found to be the major contributor. Present study shows that IVARS has better thermodynamic performance and can be successfully operated using low temperature waste heat with efficient and effective recovery.

Exergetic and integrated exergoeconomic assessments of a hybrid solar-biomass organic Rankine cycle cogeneration plant

This study is aimed at investigating optimization potentials in a conceptual hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant, through component-based exergy and exergoeconomic analyses. The ORC is rated at 629 kWe, and it is related to a real and operational plant. Exergy balance is established in each system component, from where irreversibility rate in the respective components is obtained. Thus, exergy-based rational efficiency and efficiency defects are computed for each system component. Also, economic performance is assessed at component level, for the entire system, using conventional specific exergy costing (SPECO) approach. The energy quality level of each thermodynamic state is also integrated into SPECO formulations, providing a different way of obtaining unit exergy cost for each stream. This is termed here as integrated exergoeconomic approach. Exergy destruction cost rate, exergoeconomic factor and relative cost difference are used as criteria for exergoeconomic performance evaluation. Furthermore, the level of recoverability of exergy destruction in each of the system components is assessed, in order to identify notable improvement potentials. The evaluation of optimization potentials considers intrinsic irreversibilities in the respective components, which are imposed by the assumptions of systemic and economic constraints, and thus cannot be eliminated. Results showed that system exergetic efficiency amounts to about 11%. Also, cost of producing electricity was obtained as 10.5 c€/kWh and 12.1 c€/kWh, respectively for conventional and integrated exergoeconomic approach. Furthermore, cost of producing warm water was obtained to be lower by about 56% in integrated exergoeconomic approach, relative to the conventional approach. For the whole system, adopting integrated exergoeconomic approach led to reduced loss of investment costs by about 1.5 percent points, relative to the conventional approach.

Darcy–Forchheimer flow under rotating disk and entropy generation with thermal radiation and heat source/sink

This article investigates the second law of thermodynamics for chemically reactive Sisko nanofluid by a rotating disk saturated with non-Darcy porous medium. Thermophoresis and Brownian motion on irreversibility has been examined through Buongiorno model. The novel features of nonlinear thermal radiation, Joule heating, MHD and non-uniform heat source/sink are accounted. Modified Arrhenius model is executed to characterize the impact of activation energy. The governing flow equations are solved and validated numerically by adopting Runge–Kutta–Fehlberg method. It is noticed from the present analysis that irreversibility rate and Bejan number have reverse behavior for Brinkman number. Growing behavior of concentration is witnessed for greater estimations of activation energy variable. Total entropy generation has significant impact on reaction rate constant.

Diagnosis of a hydrogen-fueled 1-kW PEMFC system based on exergy analysis

In this study, a model based diagnosis of a hydrogen-fueled 1-kW proton exchange membrane fuel cell (PEMFC) system was conducted based on exergy analysis to identify faulty components. Faulty components of balance of plant (BOP) were experimentally simulated by reducing the rpm signals of the pump, fan, and air and fuel blowers; reducing the output signals of the air and fuel flow meters; increasing the output signal of the temperature sensor; opening the valve between the air blower and the air flow meter; and blocking the heat exchange area during the operation of the PEMFC system. The irreversibility rate, malfunction (MF) and dysfunction (DYS) of each component were calculated for the case under normal condition and simulated failure conditions using the observed data. The residuals of the MF and relative malfunction (RMF) between the normal and failure conditions were the fault indicators used to identify the faulty components in the system. The proposed diagnosis method employing both the MF and the RMF was found to be not only simple but also effective.

Thermodynamic performance analysis of a copper–chlorine thermochemical cycle and biomass based combined plant for multigeneration

The primary objective of this work is to investigate a comprehensive thermodynamic assessment of the biomass-assisted multigeneration plant for electrical energy, hydrogen, heating-cooling, drying, and hot water production. The suggested multigeneration plant includes the biomass gasification process, Brayton cycle, Kalina cycle, organic Rankine cycle, and cascade refrigeration plant, which is to produce heating and cooling loads, drying system, hydrogen generation with copper–chlorine thermochemical process, and hydrogen liquefaction process. Based on the thermodynamic laws, the total irreversibility rate and performance assessment of the examined study is conducted. Moreover, the impact of various factors such as reference temperature, biomass gasifier temperature, and mass flow rate of biofuel, on the effectiveness and useful outputs of planned plant are examined. The outcomes of the proposed study show that 18 626, 3948 and 1037 kW electrical energy are generated by using the Brayton, Kalina, and organic Rankine cycle. Furthermore, the total cooling and heating capacities and hydrogen generation rates are 2392, 2864 kW and 0.068 kg s−1. Finally, energetic and exergetic effectiveness of the examined model are calculated as 56.71% and 53.59%.

Modified auxiliary exergy costing in advanced exergoeconomic analysis applied to a hybrid solar-biomass organic Rankine cycle plant

This study concerns advanced exergoeconomic analysis of a hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant. The hybrid plant had been previously conceived as structural optimization scheme to upgrade thermo-economic performance of a real 630 kW solar-ORC plant which currently runs in Ottana, Italy. The irreversibility rates, investment cost rates and irreversibility cost rates were obtained for each system component, based on thermodynamic balance as well as cost balance and auxiliary equations established for the components. Next, the avoidable/unavoidable and exogenous/endogenous splitting options were applied to investigate the sources of thermo-economic losses in the system, the effects of component interactions on the losses, as well as the best approach to improving the system. The main contribution of this paper centers on modification of the traditional auxiliary exergy costing in advanced exergoeconomic methodology, by incorporating stream energy quality into the cost formation process. Results showed that more than 50% of total irreversibility rates can be avoided in almost all of the components of the hybrid plant, most of which are endogenous. Similarly, it was obtained that component interdependencies have little impact on thermo-economic losses. Specifically, more than 60% of irreversibility cost rates could be avoidable in the hybrid plant by optimizing internal operations of each of the system components individually. Moreover, results showed that how auxiliary exergy costing is defined in advanced exergoeconomic method plays a significant role on the analysis, and the modified approach presented in this study is a viable choice.

Design and thermodynamic assessment of a biomass gasification plant integrated with Brayton cycle and solid oxide steam electrolyzer for compressed hydrogen production

In this paper, a comprehensive thermodynamic evaluation of an integrated plant with biomass is investigated, according to thermodynamic laws. The modeled multi-generation plant works with biogas produced from demolition wood biomass. The plant mainly consists of a biomass gasifier cycle, clean water production system, hydrogen production, hydrogen compression, gas turbine sub-plant, and Rankine cycle. The useful outputs of this plant are hydrogen, electricity, heating and clean water. The hydrogen generation is obtained from high-temperature steam electrolyzer sub-plant. Moreover, the membrane distillation unit is used for freshwater production, and also, the hydrogen compression unit with two compressors is used for compressed hydrogen storage. On the other hand, energy and exergy analyses, as well as irreversibilities, are examined according to various factors for examining the efficiency of the examined integrated plant and sub-plants. The results demonstrate that the total energy and exergy efficiencies of the designed plant are determined as 52.84% and 46.59%. Furthermore, the whole irreversibility rate of the designed cycle is to be 37,743 kW, and the highest irreversibility rate is determined in the biomass gasification unit with 12,685 kW.

Irreversibility Analysis and Heat Transport in Squeezing Nanoliquid Flow of Non-Newtonian (Second-Grade) Fluid Between Infinite Plates with Activation Energy

The main theme of this communication is to scrutinize the chemically reactive flow of second-grade nanoliquid between two infinite plates. The MHD fluid is considered. Both plates approach symmetrically to each other, generating squeezing flow. The Buongiorno model is utilized for the modeling. Viscous dissipation and Ohmic heating effects are further considered. The total irreversibility rate is achieved via thermodynamics second law. To transform the reactants into products, a concept of activation energy is used. The nonlinear PDEs are altered into ordinary ones through similarity transformations and solved through homotopy analysis method. The impact of sundry parameters on flow, temperature and concentration fields is studied with the help of graphic illustrations. Velocity and temperature gradients are discussed numerically through Tables 2 and 3. The velocity of fluid particles increases versus squeezing parameter, while temperature field decreases. The entropy rate and Bejan number demonstrate the contrast influence against Brinkman number.

Design and thermodynamic modeling of a renewable energy based plant for hydrogen production and compression

In the examined paper, a solar and wind energy supported integrated cycle is designed to produce clean power and hydrogen with the basis of a sustainable and environmentally benign. The modeled study mainly comprises of four subsystems; a solar collector cycle which operates with Therminol VP1 working fluid, an organic Rankine cycle which runs with R744 fluid, a wind turbine as well as hydrogen generation and compression unit. The main target of this work is to investigate a thermodynamic evaluation of the integrated system based on the 1st and 2 nd laws of thermodynamics. Energetic and exergetic efficiencies, hydrogen and electricity generation rates, and irreversibility for the planned cycle and subsystems are investigated according to different parameters, for example, solar radiation flux, reference temperature, and wind speed. The obtained results demonstration that the whole energy and exergy performances of the modeled plant are 0.21 and 0.16. Additionally, the hydrogen generation rate is found as 0.001457 kg/s, and the highest irreversibility rate is shown in the heat exchanger subcomponents. Also, the net power production rate found to be 195.9 kW and 326.5 kW, respectively, with organic Rankine cycle and wind turbine. The final consequences obtained from this work show that the examined plant is an environmentally friendly option, which in terms of the system's performance and viable, for electrical power and hydrogen production using renewable energy sources.

Entropy analysis in nonlinearly convective flow of the Sisko model in the presence of Joule heating and activation energy: the Buongiorno model

This investigation deals with entropy generation optimization and an activation energy mechanism for nonlinear convective flow of a Sisko nanofluid due to a stretchable rotating disk. Heat transfer analysis is accomplished through nonlinear thermal radiation and non-uniform heat generation/absorption. The Joule heating effect is also considered with viscous dissipation. The nanofluid model includes Brownian motion and thermophoresis. Apposite transformations are endorsed to obtain the nonlinear-coupled ordinary differential equation system. The attained system endeavors for series solutions by the homotopy technique. Total entropy generation is analyzed through numerous flow variables. A comparative study of shear-thickening and shear-thinning fluids is also presented for the Bejan number, heat transfer rate, mass transfer Nusselt number, entropy generation, temperature, velocity and concentration. Here the entropy generation rate (irreversibility rate) is enhanced for the thermal radiation parameter while the reverse behavior is noted for the material parameter and Brinkman number. Furthermore, the behavior of the temperature profile and nanoparticle concentration will be displayed through a Brownian motion parameter and an activation energy parameter.

Exergy analysis of plate heat exchanger with graphene alumina hybrid nanofluid: experimentation

The water-based hybrid nanofluid is proposed as a cooling agent in a corrugated counter-flow type plate heat exchanger aimed at sub-ambient temperature applications. For this purpose, an experimental investigation has been done with different working fluids. Fluids considered as a coolant are DI water, alumina nanofluid, and alumina-graphene hybrid nanofluid in 80:20 nanoparticle ratio by volume with a total volume concentration of 0.01% dispersed in DI water. Various exergy related performance factors like coolant outlet temperature, coolant exergy rate, irreversibility rate, non-dimensional exergy, and second law efficiency have been considered. The influence of coolant inlet temperature and flow rate on different parameters has been investigated. Coolant outlet temperature, coolant exergy rate, irreversibility rate and non-dimensional exergy augments by 2.5%, 4.8%, 7.5% and 3.5%, respectively. While the second law efficiency degrades using nanoparticles and increasing flow rate and decreases with the coolant inlet temperature.

Exergy analysis of plate heat exchanger with graphene alumina hybrid nanofluid: experimentation

The water-based hybrid nanofluid is proposed as a cooling agent in a corrugated counter-flow type plate heat exchanger aimed at sub-ambient temperature applications. For this purpose, an experimental investigation has been done with different working fluids. Fluids considered as a coolant are DI water, alumina nanofluid, and alumina-graphene hybrid nanofluid in 80:20 nanoparticle ratio by volume with a total volume concentration of 0.01% dispersed in DI water. Various exergy related performance factors like coolant outlet temperature, coolant exergy rate, irreversibility rate, non-dimensional exergy, and second law efficiency have been considered. The influence of coolant inlet temperature and flow rate on different parameters has been investigated. Coolant outlet temperature, coolant exergy rate, irreversibility rate and non-dimensional exergy augments by 2.5%, 4.8%, 7.5% and 3.5%, respectively. While the second law efficiency degrades using nanoparticles and increasing flow rate and decreases with the coolant inlet temperature.

Thermodynamic analysis of a gasifier-based coal-to-fuel cogeneration system

In this paper a thermodynamic model has been developed for the analysis of a coal gasifier based cogeneration system. The influence of the pressure ratio, turbine inlet temperature and pinch point is ascertained on cogeneration performance. Elevation of gasifier pressure leads to decrease the first law efficiency of cogeneration but a small gain in its second law efficiency is observed. Both first and second law efficiencies of cogeneration decrease with increasing the pinch point temperature, however, the increase of pinch point temperature involves a significant rise of power to heat ratio. A considerable improvement in the performance parameters of cogeneration is observed with the rise of turbine inlet temperature. Irreversibility rates of 5,994 kW and 2,597 kW are found in the combustion chamber and HRSG, respectively. Increasing the gasifier pressure enhance the first law efficiency of cogeneration but provides a small gain in the second law efficiency of cogeneration.

Thermodynamic analysis of a gasifier-based coal-to-fuel cogeneration system

In this paper a thermodynamic model has been developed for the analysis of a coal gasifier based cogeneration system. The influence of the pressure ratio, turbine inlet temperature and pinch point is ascertained on cogeneration performance. Elevation of gasifier pressure leads to decrease the first law efficiency of cogeneration but a small gain in its second law efficiency is observed. Both first and second law efficiencies of cogeneration decrease with increasing the pinch point temperature, however, the increase of pinch point temperature involves a significant rise of power to heat ratio. A considerable improvement in the performance parameters of cogeneration is observed with the rise of turbine inlet temperature. Irreversibility rates of 5,994 kW and 2,597 kW are found in the combustion chamber and HRSG, respectively. Increasing the gasifier pressure enhance the first law efficiency of cogeneration but provides a small gain in the second law efficiency of cogeneration.

Thermal runaway and thermodynamic second law of a reactive couple stress hydromagnetic fluid with variable properties and Navier slips

Theoretical solutions of a thermal runaway and irreversibility thermodynamic analysis of a couple stress hydromagnetic reactive fluid with Navier slip conditions and variable properties are examined. Ignoring the material assumption, the fluid is taken to be actively exothermic under Bimolecular kinetics. The dimensionless modeled equations are analytically solved using weighted residual method coupled with collocation techniques to obtain the bifurcation branch chain for criticality, irreversibility rate, flow rate and heat distribution solutions. It was noticed that the variable properties have no significant influence on the couple stress reactive liquid and heat distribution. Also, at high thermodynamic equilibrium, entropy generation in the system is minimized. This study results will help in understanding the relationship that exist between thermal explosion and thermal branched-chain in managing industrial engines in order to avoid system blow up.

Interacting influences of Lorentz force and bleeding on the hydrothermal behaviors of nanofluid flow in a trapezoidal recess with the second law of thermodynamics analysis

This study deals with the analysis of the interacting influences of Lorentz force and bleeding on the hydrothermal behaviors of magnetohydrodynamic (MHD) nanofluid flow and entropy generation in a trapezoidal recess. This trapezoidal recess is created by two inclined steps in a horizontal channel. The Lorentz force is appeared due to the existence of a magnetic field in the flow domain. The Brownian motion influences on the effective characteristics of CuO -water nanofluid are considered to have more accuracy. The effects of bleeding coefficients (−0.005 ≤ Vw ≤ + 0.005), Hartmann number (0 ≤ Ha ≤ 60) and concentration of solid nanoparticles (0 ≤ ϕ ≤ 0.04) on the flow characteristics, heat transfer and flow irreversibility rates are investigated. The results show that the trends and values of friction coefficient, Nusselt number and entropy generation number can be different at the various magnitudes of Ha and Vw, whereas the ϕ parameter only increases the values of them. These differences are related to the variations of streamlines contours against the Ha, Vw and ϕ parameters.

Numerical assessment of Ag-water nano-fluid flow in two new microchannel heatsinks: Thermal performance and thermodynamic considerations

The present paper is devoted to the first and second law analysis of a aqueous nano-fluid (NF) containing suspended Ag nanoadditives in two new microchannel heatsinks. The influences of nanoadditives volume fraction (φ) and Reynolds number (Re) on performance indicators based on the first and second law of thermodynamics are taken into account and analyzed. The outcomes reveal that the augmentation of Re and φ causes an intensification in the convective heat exchange coefficient and a decrease in the CPU temperature, thermal irreversibility rate and enhance the CPU temperature uniformity. However, grow of Re intensifies both the pumping power and irreversibility due to flow friction. Additionally, the outcomes depicted the superior performance of NF compared to the base fluid. Moreover, the irreversibility inside the studied heatsinks is mainly due to the heat transfer compared to the flow friction. Finally, the results demonstrate that the heatsink with more path changes is more efficient form the viewpoint of the first and second laws of thermodynamics.

Heat transfer analysis of energy and exergy improvement in water-tube boiler in steam generation process

Steam generation is an essential process in steel production. Saturated steam is used in the cold-rolling mills of sample steel company to raise the acid pool temperature. The studied water-tube boiler had a rated saturated steam generation capacity of 47 tons per hour. This study used energy and exergy balance equations for each of the components in the cycle to calculate exergy efficiency and irreversibility rate. Results from the exergy analysis along with the exergy dissipation rate of the cycle were obtained. Based on the literature results, it was recommended to increase the input air temperature by means of a preheater. First, the exergy dissipation in the boiler was reduced by 68 kJ kg−1 with the installation of an economizer. The most important cause of exergy destruction was then presented, and some recommendations were provided on how to increase the temperature of the makeup water in order to increase the boiler efficiency and exergy.

Exergy analysis and performance optimization of bagasse fired boiler

In the present scenario, the energy crisis and its demand have become the global problems that restrict the sustainable development. To overcome this problem, one needs to develop an advanced technological system which not only improves the system performance but also reduces the environmental effects. Several technologies have been established among which cogeneration appeared to be the most lucrative option. India, one of the leading producers of sugarcane, has enough cogeneration capacity in sugar mills. From the previous research articles, energy analysis explores several components which account for the significant loss of energy in a cogeneration power plant but the analysis based on the second law depicts that maximum exergy destruction occurred in a boiler. Hence, to enhance the overall performance of the plant, we need to improve boiler performance. In the present study, the energy and exergy analyses of a sugarcane bagasse boiler are carried out, and it has been seen that the energy efficiency of the boiler is high enough (81.78%). However, the second law efficiency is 25.08%, the irreversibility rate associated with the combustion chamber is 50.06 MW is a significant value which shows that 45.56% of the input fuel exergy is destroyed in the combustion chamber only. The irreversibilities associated with the heat exchangers are also significant which has been investigated as 17.23% of the input exergy of the fuel. This shows that the combustion chamber and heat exchangers both have enough scope of improvement.

Development and techno-economic assessment of a new biomass-assisted integrated plant for multigeneration

In this paper, a novel renewable power-assisted multigeneration system is introduced for useful commodities such as cooling, hydrogen, heating, drying, hot water, and power generations. The biomass energy is preferred as a renewable power source. The proposed plant is including the biomass gasifier unit, gas turbine cycle, Kalina cycle, reverse osmosis unit, proton exchange membrane electrolyzer, absorption cooling cycle, dryer and heat pump subsystem. The primary purpose of this paper is to analyze a biomass assisted combined plant in terms of thermodynamic and economic viewpoints. In this regard, the thermodynamic performance, exergy destruction rate and economic examination are performed according to the various parameters. Results demonstrated that the whole energy and exergy efficiencies of the examined plant are 63.84% and 59.26%, respectively. Furthermore, the total irreversibility and hydrogen production rates are found as 53,406 kW and 0.072 kg/s. The overall purchase cost rate of the suggested cycle is about 2000 $/s.