Law Of Thermodynamics Analysis Research Articles

Entropy generation on MHD motion of hybrid nanofluid with porous medium in presence of thermo-radiation and ohmic viscous dissipation

Hybrid nanotechnology has significantly contributed to enhancing energy efficiency and reducing heat loss. This study addresses entropy analysis in the motion of hybrid nanofluids incorporating magnetohydrodynamic effects, thermal radiation, and ohmic viscous dissipation phenomena. The implementation of magnetohydrodynamic, thermal radiation, and dissipation effects allows for a second law of thermodynamics analysis. The hybrid nanoparticles considered are Graphene Oxide (GO) and Molybdenum Disulphide (MoS2), with water serving as the base liquid. Entropy generation analysis, a thermodynamic approach, quantifies irreversibility and inefficiencies within the system, aiding in understanding losses and identifying areas for improvement. Additionally, a comparative study is conducted. The BVP4C algorithm, implemented using MATLAB, is employed to address this study and obtain solutions. The key findings indicate that heat transfer rates are higher for blade-shaped nanoparticles, and entropy is minimized by controlling parameters such as the radiation parameter, Brinkman parameter, and temperature difference.

An Ocean Thermal Energy Conversion power plant: Advanced exergy analysis and experimental validation

An ocean thermal energy conversion power plant was simulated from the point of view of the first, the second law of thermodynamics, and advanced exergy analysis with the aim of increasing the efficiency of the cycle, quantifying and knowing the nature of the exergy destruction. First, the net power output and efficiency of the cycle were successfully calculated as a function of the surface temperature and a certain depth of the ocean, given a pinch temperature differential and the mass flow of seawater in the evaporator and condenser. The numerical simulation are compared with experimental evidence, obtaining better results than thermodynamic models previously reported. Then, the second law of thermodynamics analysis was made using appropriate correlations for the estimation of thermo-physical properties of seawater, revealing the imprecision of assuming properties of pure water in the calculation of the total exergy destruction of the system. Finally, advanced exergy analysis is developed, it provides the nature of the exergy destruction and the best strategy to increase the efficiency of the cycle. The evaporator and turbine are presented as the most promising pieces of equipment to be developed in new future research due to their avoidable endogenous nature of exergy destruction.

First and second law thermodynamic analysis of a single and dual-stage ignition biomass downdraft gasifier

The dual-stage ignition biomass downdraft gasifier is an enormous tar reduction technology as against a single-stage ignition biomass gasification. Exergetic analysis of the system guides toward a possible performance enhancement. In dual-stage gasification, around 67.76% of input exergy is destructed in the several components, while 9.16% is obtained as a useful exergy output and 24.34% is found to be as a useful energy output there. The entire unit was assessed with a progressively rising electric load from 15.24 kW to 38.86 kW. The enhanced producer gas quality comes from 57% combustible gas with a higher heating value of 6.524 MJ/Nm3 and tar content of 7 mg/Nm3 after the paper filter, whereas the biomass consumption rate is 58 kg/h at the greatest load with the grate temperature of 1310–1370 °C. The samples of exhaust gas emissions are obtained environmentally favorable. The results even described that the dual-stage ignition biomass downdraft gasifier has significantly greater energetic and exergetic efficiency as compared to the single-stage gasifier.

Theoretical analysis of the performance and optimization of indirect flat evaporative coolers

External-cooling indirect evaporative coolers with different configurations and working air sources are incomprehensively analyzed and compared so far. This paper investigates the mechanism and theory of operation of indirect flat-panel evaporative coolers based on X-analysis. Then, based on the second law of thermodynamics analysis, the entropy production rate of the flat-plate heat exchanger of the cooler is calculated. As a result of this analysis, the optimal energy efficiency-evaporation efficiency and cooling capacity values are presented in terms of effective parameters in the design.

Thermal analysis and optimization of indirect flat evaporative coolers

• Analyzing the energy and exergy performance of indirect flat evaporative coolers on the basis of a verified numerical model and experimental correlation • Investigating the mechanism and theory of operation of indirect flat-panel evaporative coolers based on X-analysis • Calculating the entropy production rate of the flat-plate heat exchanger of the cooler Less attention and analysis have been given to cooling indirect evaporative coolers with different configurations and working air sources so far. This paper investigates the mechanism and theory of operation of indirect flat-panel evaporative coolers based on X-analysis. Then, based on the second law of thermodynamics analysis, the entropy production rate of the flat-plate heat exchanger of the cooler is calculated. As a result of this analysis, the optimal energy efficiency-evaporation efficiency and cooling capacity values are presented in terms of effective parameters in the design. It was concluded that dew point effectiveness and COP of the proposed system change monotonously with inlet mass flow rate, temperature and humidity ratio of primary air, respectively. The dew point effectiveness also varies monotonously with the mass flow rate ratio of secondary air to primary air. However, there exists an optimal mass flow rate ratio resulting in a maximum COP.

Adsorption of difluoromethane onto activated carbon based composites: Adsorption kinetics, heat of adsorption, cooling performance and irreversibility evaluation

To further the research on R32 refrigerant-based adsorption cooling applications, Maxsorb-III activated carbon composites synthesized with the additives of H25 Graphene nanoplatelets (GNP), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid with polyvinyl alcohol (PVA) are studied for cooling performance evaluation. Their respective kinetic characteristics and heat of adsorption assessments are carried out for this purpose in the present study. The adsorption kinetics characteristics are studied using gravimetrically for the composite samples. A first-order kinetics model is seen to fit their kinetic uptakes with regression coefficients ≥ 0.97. The heat of adsorption estimates of the composites for varying uptakes and temperatures are numerically evaluated, incorporating the non-ideal behavior of the refrigerant. An approach for a holistic comparison of the cooling performances of the composites containing their respective heat and mass transfer characteristics for compact heat exchanger designs is further proposed. While the composite with the highest Maxsorb-III mass fraction yields the highest specific and volumetric cooling powers, the composite with the highest thermal conductivity requires the lowest heat exchanger area with a slightly larger adsorbent volume of around 12.1% over the former. A second law thermodynamic analysis is further carried out to evaluate the composite performances for cooling applications.

Exergy analysis in diesel engine with binary blends

Investigation on Diesel engine with minimized fuel consumption rate and increased output power is not the meaningful procedure if irreversibility in the thermodynamic system is ignored. This current procedure is aimed to signify the importance of exergy analysis in Diesel engine performance on the perspective of Second law of thermodynamics analysis. In this study, diesel-cotton seed oil blends were tested on engine running with direct fuel injection mode of operation. The experiments were conducted with diesel (D), 5% cotton seed oil-95% diesel (CB5), 10% cotton seed oil-90% diesel (CB10), and 15% cotton seed oil-85% diesel (CB15) for estimation of brake power, energy rate, and exergy rate in the fuel and exhaust, heat release rate, exergy destruction, ideal efficiency (I law), and actual (II law) efficiency. The results outcome that an increase in trend was observed in the fuel exergy and thermal exergy loss with engine speed for D, CB5, CB10, and CB15. The loss of exergy, heat release rate, percentage of exergy and exergy transferred through exhaust gases decreased for CB5, CB10, and CB15 compared to diesel.

Parametric analysis and minimization of entropy generation in bioinspired magnetized non-Newtonian nanofluid pumping using artificial neural networks and particle swarm optimization

Magnetohydrodynamic rheological bio-inspired pumping systems are finding new applications in modern energy systems. These systems combined the electrically conducting properties of flowing liquids with rheological behaviour, biological geometries and propulsion mechanisms. Further enhancements in transport characteristics can be achieved with the deployment of nanofluids. Second law thermodynamic analysis also provides a useful technique for optimizing thermal performance by minimizing entropy generation. In the present study, all these aspects are combined to analyze the heat transfer in magnetic viscoelastic nanofluid flow in a two-dimensional deformable channel containing a rigid porous matrix under peristaltic waves subject to a transverse magnetic field. The Williamson model is deployed for the nanofluid rheology and the Buongiorno model for nanoscale effects. Under lubrication approximations, the conservation equations for mass, momentum, energy and nanoparticle species are simplified. These partial differential equations are further non-dimensionalized using relevant transformation variables. The mathematical model is solved analytically by means of the Homotopy Analysis Method (HAM). Next, entropy generation is minimized by applying Particle Swarm Optimization (PSO) and Artificial Neural Networks (ANN). In the first phase, the equation for Entropy generation is derived as a function of temperature distribution, velocity profile utilizing geometrical and thermophysical parameters. The first step is to discover entropy generation to estimate some extraordinary influencing parameters. In the next step, some specific multi-layer perceptron ANNs are trained, which depend on the information from the first stage. In the last step, PSO in the considered peristaltic flow is used to minimize entropy generation. The optimized value (minimum) of entropy generation is 3.65 kJ/kg acquired at magnetic parameter (M) = 3, Brownian motion parameter (Nb) = 0.3, thermophoresis parameter (Nt)= 0.5 and Brinkman number (Br)=2 . Entropy generation is also very sensitive to both iteration number and magnetic field exhibiting a nonlinear topology.

Assessment of alumina/water nanofluid in a glazed tube and sheet photovoltaic/thermal system with geothermal cooling

This article presents evaluation of alumina/water nanofluid (NF) in a glazed tube and sheet photovoltaic/thermal (PV/T) system with ground-coupled heat exchanger (GCHE) in semi-arid region of Pilani, Rajasthan (India). Conventionally in the literature, the cooling performance of NF is reported compared to the normal fluid cooling under equal Reynolds number (Re) comparison criterion. However, according to many researchers, equal pumping power-based evaluation is more pragmatic and is explored here. The first law of thermodynamics analysis is invoked to appropriately assess the replacement of water with NF in the PV/T system coupled with GCHE. Nanoparticle concentration is varied from 0.5% to 6% by volume fraction and the Re from 3000 to 9000. Temperature of PV panel, temperature difference in PV/T outlet and inlet, electrical efficiency, thermal efficiency and Bejan number in PV as well as in GCHE are computed using a validated mathematical model for both equal Re and equal pumping power evaluation criteria. The performance of PV/T system with NF is found superior under equal Re comparison. The improvement observed are reduction in PV panel temperature by 2 °C, reduction in temperature difference in PV/T outlet and inlet by 6 °C, rise in electrical efficiency by 0.1% and a rise in thermal efficiency by 4%. However, the performance of PV/T system with NF is found inferior under equal pumping power evaluation criterion.

Cooling capacity of magnetic nanofluid in presence of magnetic field based on first and second laws of thermodynamics analysis

ABSTRACT In this numerical study, the cooling capacity of water/Cu magnetic nanofluids in a horizontal duct exposed to a magnetic field has been investigated. Both the first and second laws of thermodynamics analysis are conducted. All simulations have been performed for the volume fraction of 5%, Reynolds number (Re) of 100, and the Hartmann numbers (Ha) of 0, 20, 50, and 80. Temperature, velocity profiles, Nusselt number (Nu), Lorentz force (F), and thermal, frictional, and magnetic irreversibility have been studied by changing Ha. The received results indicate that as the Ha increases, the hydrodynamic boundary layer thickness decreases, while the length of the hydrodynamic entrance length increases. In addition, as the Ha increases in the range of 0 to 80, the local Nu number increases by about 7.5%, and the local wall temperature drops to 2.7%. The second law of thermodynamic analysis showed that as the Ha increases, the frictional irreversibility augments, while the thermal irreversibility decreases. Finally, the order of thermal irreversibility is larger than that of frictional and magnetic irreversibility.

The effect of low reactivity fuels on the dual fuel mode compression ignition engine with exergy and soot analyses

In this study, the effect of fuel injection timing of diesel on the dual fuelled compression ignition engine with gasoline, methanol and toluene has been investigated. Closed cycle combustion simulations have been conducted to complement the experiment results and for a better understanding of the in-cylinder dynamics. Second law of thermodynamics analysis has been done for the designing of energy recovery devices. Exhaust soot particles has been analysed by scanning electron microscopy to get soot particle structure. Distributions of soot particle number by size and particle mass by size have been investigated. Experiments have been conducted for respective premixed ratios of gasoline/methanol/toluene at different start of injection (SOI) timing of diesel. Outcomes revealed that the maximum gross indicated thermal efficiency (GITE) of 39% is obtained for gasoline/diesel mode. This mode shows 86% more oxides of nitrogen (NOx) in comparison with methanol/diesel mode at −25 crank angle degree (CAD) SOI case. About 54% more soot has been observed at −25 CAD SOI in toluene/diesel compared to that of gasoline/diesel mode. Maximum of 38.7% and minimum of 27.8% work exergies have been observed in gasoline/ and methanol/diesel modes respectively. Toluene/diesel mode shows the largest average primary particle diameter (Dp; 44 nm) among the dual fuel modes.

Analysis of a combined proton exchange membrane fuel cell and organic Rankine cycle system for waste heat recovery

ABSTRACT Proton exchange membrane fuel cell (PEMFC) has become a promising alternative power source due to its quiet operation, low emission, and high theoretical energy conversion efficiency. However, a relatively large fraction of the energy (around 40 ~ 50%) is dissipated into the ambient environment by the cooling system, leading to a waste of thermal energy. The present study aims to improve the practical PEMFC performance by harvesting the thermal energy from the cooling system utilizing an organic Rankine cycle (ORC) system. The R134a and R245fa are selected as the working liquids for ORC to harvest energy from the PEMFC. A combined PEMFC and ORC model is established based on the first and second law thermodynamic analysis. It is found that the cycle efficiency (ηorc ) of R134a (about 11.33%) is higher than that of R245fa (about 9.16%). The combined system efficiency (ηsys ) for R134a can be increased by approximately 5.84%, compared with that of the fuel cell stack alone. For R134a, the effect of changes in the operating temperature and current density of the PEMFC stack on its cycle efficiency (ηorc ) is investigated. The results indicate that as the working temperature of the PEMFC stack increases, both the ORC and combined system efficiencies (ηorc and ηsys ) increase, while with the increase of the current density of the PEMFC, the ORC cycle efficiency (ηorc ) remains almost constant, and the combined system efficiency (ηsys ) decreases. The exergy efficiency is found to have the same variation trends with the energy efficiency.

Second law thermodynamic analysis of thermo-magnetic Jeffery–Hamel dissipative radiative hybrid nanofluid slip flow: existence of multiple solutions

In this article, a detailed theoretical examination is conducted for the steady, incompressible, MHD hybrid nanofluid (Al2O3/Cu–water) dissipative slip flow between non-parallel (i.e., diverging or converging) shrinking/stretching walls in the presence of appreciable thermal radiation. Appropriate similarity transformations have been applied to render the hybrid transport model conservation equations dimensionless. The diffusion flux approximation is employed for radiative heat transfer. The well-posed boundary value problem has been analyzed for solution bifurcations with a predictor homotopy analysis method (PHAM) along with stability analysis. The eigenvalues obtained predict the upper branch (Ist solution) to be physically acceptable. The critical values ( $$\chi_{c} \le \chi < 0$$ ) of stretching/shrinking parameter are evaluated by varying slip and magnetic body force parameters. The impact of significant parameters on skin friction coefficient, Nusselt number and entropy generation number is also visualized and elaborated in detail. With stronger magnetic field parameter (M), i.e., enhancement in magnetohydrodynamic Lorentz drag force, the existence domain of the dual solutions is shown to be expanded and the critical points of the stretching parameter ( $$\chi$$ ) for $$M = 0.1,0.5,1$$ are identified, respectively, as $$\chi_{c} = - 3.2455, - 3.2680,$$ $$- 3.2987$$ . The upper branch of skin friction, Cfr decreases as the volume fraction $$\varphi$$ increases whereas the lower branch increases with an increase in the volume fraction of copper nanoparticles. Entropy generation is observed to be elevated with stronger radiation, inertial effect (Reynolds number) and Prandtl number (i.e., lower thermal conductivity) whereas it is suppressed with increasing hybrid nanoparticle volume fraction and wall hydrodynamic slip effect. Magnetic field is found to induce a weak modification in entropy generation. Increasing angular coordinate $$\left( {\xi = \frac{\theta }{\beta }} \right)$$ is observed to elevate the entropy generation. The computations find applications in thermo-magnetic nozzle design, electromagnetic propulsion systems and electroconductive materials processing.

Second law thermodynamic analysis of imbalanced counter flow heat exchanger for energy conservation

Entropy generation of imbalanced counter flow heat exchanger is analyzed to know the thermal behavior effects such as entropy generation minimization and exergetic efficiency. The analysis of first law which does not considers different irreversibilities such as transfer of heat, drop in fluid pressure and mass flow streams unbalance is possible from second law of thermodynamics studies. In this analysis the parameters which are considered are length to diameter dimensions of heat transfer equipment tube, fluid streams capacity ratio, Reynolds number of fluid and type of fully developed fluid flow. To understand the behavior of heat exchanger the heat capacity rate of heat exchanger’s maximum value is changed for both cases of hot stream and cold stream. Optimum heat exchanger geometrical dimension namely length-to-diameter ratio can be obtained from the second law analysis corresponding to lower total entropy generation and higher second law efficiency which leads to energy conservation. Accordingly, for the minimum entropy generation and maximum exergetic efficiency resulted, the optimum length-to-diameter ratio are obtained for different cases considered.

Numerical investigation and experimental validation of thermo-hydraulic and thermodynamic performances of helical baffle heat exchangers with different baffle configurations

Helical baffle is deemed as a favorable substitute for segmental one. In the present paper, the investigations on fluid flow and heat transfer behaviors are conducted for heat exchangers with eight helical baffle configurations, involving the continuous helical (CH) scheme, quadrant helical (QH) scheme with diverse axial overlapped ratios and novel sextant helical (SH) scheme. The second law of thermodynamics analysis is exploited to further evaluate the irreversibility in helical baffle heat exchangers. Verifications between the experimental data and numerical predictions are performed, and a good agreement is achieved. The parallel and rotational components decomposed from shell-side velocity are detected, and a new conception of the swirl angle is advanced to reveal the stream pattern in helical channel. The leakages passing through conjunction notches between adjacent baffle plates are depicted to check the discrepancy between the spiral and pseudo-spiral flow states. It concludes that the alterations of baffle shapes and assembly arrangements influence the flow field properties significantly. By analyzing the heat transfer, resistance and comprehensive characteristics in shell side, the SH scheme possesses better thermo-hydraulic performance than the CH and QH schemes; moreover, the least entropy generation is received in the SH and QH schemes at low Reynolds number. In addition, larger axial overlapped ratio provides greater heat transfer coefficient and pressure drop but smaller their ratio as well as higher thermodynamic irreversible loss.

Advanced Exergetic Analysis of a Double-Effect Series Flow Absorption Refrigeration System

Abstract This paper contains theoretical results of an advanced exergy study of a double-effect series flow absorption refrigeration cycle. Traditional second law of thermodynamics analysis was performed and revealed the absorber as the component with the highest exergy destruction of the system. In the evaporator, ≈49.34% of the exergy destruction is avoidable and almost in it’s entirety, ≈99.12% is of endogenous nature. The highest potential for improvement of the high-pressure generator is its design and manufacture because ≈67.47% of the endogenous exergy destruction is avoidable. A parametric study was presented to discuss the sensitivity of splitting exergy destruction concepts taking into account temperature variations in the absorber and condenser temperatures and the heat source temperature.

Thermo-Economic Performance of an Organic Rankine Cycle System Recovering Waste Heat Onboard an Offshore Service Vessel

Recent regulatory developments in the global maritime industry have signalled an increased emphasis on the improvement of energy efficiency onboard ships. Among the various efficiency enhancement options, recovering waste heat using the organic Rankine cycle (ORC) has been studied and identified as a promising one in many earlier studies. In this paper, a marine application of ORC for waste heat recovery will be discussed by performing the first law thermodynamic analysis based on the operating profile and machinery design data of an offshore service vessel (OSV) and defining four standard cycle configurations that include simple, recuperated, dual heat source, and with intermediate heating. The use of five hydrocarbon working fluids that are suitable for shipboard usage comprising cyclopentane, n-heptane, n-octane, methanol and ethanol are examined. The economic analysis found that annual fuel saving between 5% and 9% is possible and estimated a specific installation cost of $5000–8000 USD/kW. Among the various options, the methanol ORC in a simple cycle configuration is found to have the shortest payback time relatively balancing between annual fuel saving and total module cost. Finally, the simple cycle ORC running on methanol is further examined using the second law entropy generation analysis and it is found that the heat exchangers in the system accounted for nearly 95% of the overall entropy generation rate and further work is recommended to reduce this in the future.

First law thermodynamic analysis of the recuperated humphrey cycle for gas turbines with pressure gain combustion

The current work is an analysis of the recuperated Humphrey cycle. Three cycle topologies are studied with and without turbine cooling. The study focuses on the interconnection between combustor pressure gain and heat recuperation. It is an attempt to optimize the cycle topology and configuration to achieve the maximum possible cycle efficiency. It is found that the best option to use recuperation in the Humphrey cycle is to operate the combustor at stoichiometric conditions, without preheating the air fed to it. The combustion air comes effectively form a compressor air bleed. The remaining air is further compressed at the combustor outlet pressure and is fed to a plenum between combustor and turbine once it is preheated by the recuperator. This cycle configuration results in the best performance both in terms of efficiency and specific work. Specifically, an efficiency increase between 2 and 5% points is achieved. This work concludes with a feasibility study for shockless explosion combustion (SEC) for the Humphrey cycle configurations and topologies that achieve an efficiency advantage against the Joule cycle. It is found that realistic SEC combustor lengths and efficiency gains can be simultaneously achieved, albeit not at the cycle configurations with the best performance.

Second law thermodynamic analysis of syngas premixed flames

The exergy loss in laminar premixed flames of syngas is investigated numerically by analyzing the local entropy generation. The effects of the change in the H2 molar ratio in H2-CO mixture at different temperature values (from 300 to 600 K), at atmospheric and high pressure (10 and 50 atm) conditions and for different equivalence ratios (0.5, 1 and 2) are studied identifying both the mainly responsible process for exergy loss and the factors that can positively affect the performance of the syngas combustion. It is found that the chemical reactions are not always the main contribution to the total entropy generation (i.e. to exergy loss) and that the roles of the chemical reactions and heat conduction are strongly affected by pressure. Furthermore, it is underlined that the hydrogen content in syngas worsens the exergy loss due to entropy generation by the combustion process, whereas pressure increase has positive effects. However, these beneficial effects are counterbalanced by an increase of the chemical exergy content in the flue gases (mostly due to unreacted species or incomplete combustion). Therefore, a careful selection of the combustion process conditions is required to meet efficiency constraints if exhaust exergy is not meant to be afterward exploited.

Experimental performance evaluation of desiccant coated heat exchangers from a combined first and second law of thermodynamics perspective

The electricity-driven vapor-compression air-conditioning system registers around 3–10% second law efficiency under tropical climates due to the coupling between sensible and latent cooling loads. Desiccant coated heat exchangers (DCHEs) are the next-generation technologies that can improve the efficiency of the air-conditioning process by decoupling sensible and latent loads. Existing literature on DCHEs is primarily directed towards material development and performance evaluation from the first law of thermodynamics standpoint. However, to have an insight into the operation of DCHEs concerning its process irreversibility, performing the second law of thermodynamics analysis is necessary. This analysis will pinpoint the causes of irreversibility in the DCHE system and evaluate the useful work destroyed during its cyclic operation. In this paper, we have developed a general steady-state thermodynamic framework to study the performance of DCHEs from a combined first and second law perspective. Experiments were carried out to obtain the thermodynamic state properties of air, water, and desiccant that are necessary to perform energy and exergy analyses. Further, fundamental parametric studies were conducted to understand the influence of different desiccant type, varying operating parameters, and ambient conditions. Key results revealed that the regeneration process contributed to significant entropy generation rates and by reducing the hot water temperature by 10 °C, the second law efficiency illustrates improvement of almost two times. Additionally, by selecting to coat the heat exchanger with a composite polymer material instead of silica gel, the second law efficiency of DCHEs is enhanced by around 2.6 times. Lastly, a hybrid air-conditioning system comprising vapor-compression chiller and DCHE records 50% savings in energy consumption and yields two-times higher second law efficiency.