scholarly journals Entropy Generation and Exergy Analysis of Premixed Fuel-Air Combustion in Micro Porous Media Burner

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1104
Author(s):  
N. C. Ismail ◽  
M. Z. Abdullah ◽  
N. M. Mazlan ◽  
K. F. Mustafa
Keyword(s):  
Porous Media ◽  
Double Layer ◽  
Entropy Generation ◽  
Equivalence Ratio ◽  
Single Layer ◽  
Exergy Efficiency ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Total Entropy ◽  
Porous Media Burner

The performance of porous media micro-burners plays an important role in determining thermal efficiency and improving our daily life. Nowadays, a lot of scholars are actively involved in this research area and ongoing studies are still being carried out due to the burners’ excellent performance. The exergy efficiency and entropy generation of a porous media burner are strongly dependent on the characteristics of the flame and its thermal behavior. In this study, a single-layer and double-layer porous media form were constructed to investigate the effects of various types of porous foam arrangement in a cylindrical burner. The burner was operated using premixed butane-air combustion with an inner diameter of 23 mm and a length of 100 mm. The experiments were carried out in rich fuel conditions with an equivalence ratio, φ ranging from 1.3 to 2.0. The results showed significant improvement in the thermal and exergy efficiency with an increase in the equivalence ratio in a double-layer compared with a single-layer. The peak temperature recorded was 945.21 °C at φ = 1.3 for a porcelain single-layer, and the highest exergy efficiency was 83.47% at φ = 2.0 for an alumina-porcelain double-layer burner. It was also found that the average temperature of the burner wall decreased with an increase in the equivalence ratios for PMB2 and PMB4, whereas the average wall temperature for PMB3 was largely unaffected by the equivalence ratios. The total entropy generation rate reached the highest value at φ = 2.0 for all PMB configurations, and the highest percentage increase for total entropy generation rate was 46.09% for PMB1. The exergy efficiency for all burners was approximately similar with the highest exergy efficiency achieved by PMB4 (17.65%). In addition, the length and location of the flame with thermal distribution was significantly affected by the equivalence ratio between the single-layer and double-layer porous material. Overall, a double-layer porous media burner showed the best performance calculated based on the second law of thermodynamics when compared with other configurations, and it is ideal for domestic application.

scholarly journals Analytical Analysis of Heat Transfer and Entropy Generation in a Tube Filled with Double-Layer Porous Media

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1214 ◽  
Author(s):  
Kun Yang ◽  
Wei Huang ◽  
Xin Li ◽  
Jiabing Wang
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Nusselt Number ◽  
Double Layer ◽  
Entropy Generation ◽  
Single Layer ◽  
Entropy Generation Rate ◽  
Total Entropy ◽  
Interfacial Radius

The heat transfer and entropy generation in a tube filled with double-layer porous media are analytically investigated. The wall of the tube is subjected to a constant heat flux. The Darcy-Brinkman model is utilized to describe the fluid flow, and the local thermal non-equilibrium model is employed to establish the energy equations. The solutions of the temperature and velocity distributions are analytically derived and validated in limiting case. The analytical solutions of the local and total entropy generation, as well as the Nusselt number, are further derived to analyze the performance of heat transfer and irreversibility of the tube. The influences of the Darcy number, the Biot number, the dimensionless interfacial radius, and the thermal conductivity ratio, on flow and heat transfer are discussed. The results indicate, for the first time, that the Nusselt number for the tube filled with double-layer porous media can be larger than that for the tube filled with single layer porous medium, while the total entropy generation rate for the tube filled with double-layer porous media can be less than that for the tube filled with single layer porous medium. And the dimensionless interfacial radius corresponding to the maximum value of the Nusselt number is different from that corresponding to the minimum value of the total entropy generation rate.

scholarly journals Double-Layer Micro Porous Media Burner from Lean to Rich Fuel Mixture: Analysis of Entropy Generation and Exergy Efficiency

Entropy ◽  
2021 ◽  
Vol 23 (12) ◽  
pp. 1663
Author(s):  
Nazmi Che Ismail ◽  
Mohd Zulkifly Abdullah ◽  
Khairil Faizi Mustafa ◽  
Nurul Musfirah Mazlan ◽  
Prem Gunnasegaran ◽  
...  
Keyword(s):  
Porous Media ◽  
Double Layer ◽  
Entropy Generation ◽  
Heat Exchangers ◽  
Fuel Mixture ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Cylindrical Shape ◽  
Total Entropy ◽  
Porous Media Burner

Porous media burner (PMB) is widely used in a variety of practical systems, including heat exchangers, gas propulsion, reactors, and radiant burner combustion. However, thorough evaluations of the performance of the PMB based on the usefulness of entropy generation, thermal and exergy efficiency aspects are still lacking. In this work, the concept of a double-layer micro PMB with a 23 mm cylindrical shape burner was experimentally demonstrated. The PMB was constructed based on the utilization of premixed butane-air combustion which consists of an alumina and porcelain foam. The tests were designed to cover lean to rich combustion with equivalence ratios ranging from ϕ = 0.6 to ϕ = 1.2. It was found that the maximum thermal and exergy efficiency was obtained at ϕ = 1.2 while the lowest thermal and exergy efficiency was found at ϕ = 0.8. Furthermore, the findings also indicated that the total entropy generation, energy loss, and exergy destroyed yield the lowest values at ϕ = 1.0 with 0.0048 W/K, 98.084 W, and 1.456 W, respectively. These values can be stated to be the suitable operating conditions of the PMB. The findings provided useful information on the design and operation in a double-layer PMB.

scholarly journals Combustion Characteristics of Butane Porous Burner for Thermoelectric Power Generation

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
K. F. Mustafa ◽  
S. Abdullah ◽  
M. Z. Abdullah ◽  
K. Sopian
Keyword(s):  
Power Generation ◽  
Porous Media ◽  
Thermoelectric Power ◽  
Double Layer ◽  
Equivalence Ratio ◽  
Single Layer ◽  
Thermoelectric Power Generation ◽  
Porous Burner ◽  
Lean Fuel ◽  
Te Modules

The present study explores the utilization of a porous burner for thermoelectric power generation. The porous burner was tested with butane gas using two sets of configurations: single layer porcelain and a stacked-up double layer alumina and porcelain. Six PbSnTe thermoelectric (TE) modules with a total area of 54 cm2were attached to the wall of the burner. Fins were also added to the cold side of the TE modules. Fuel-air equivalence ratio was varied between the blowoff and flashback limit and the corresponding temperature, current-voltage, and emissions were recorded. The stacked-up double layer negatively affected the combustion efficiency at an equivalence ratio of 0.20 to 0.42, but single layer porcelain shows diminishing trend in the equivalence ratio of 0.60 to 0.90. The surface temperature of a stacked-up porous media is considerably higher than the single layer. Carbon monoxide emission is independent for both porous media configurations, but moderate reduction was recorded for single layer porcelain at lean fuel-air equivalence ratio. Nitrogen oxides is insensitive in the lean fuel-air equivalence ratio for both configurations, even though slight reduction was observed in the rich region for single layer porcelain. Power output was found to be highly dependent on the temperature gradient.

The Equivalence of Maximum Power and Minimum Entropy Generation Rate in the Optimization of Power Plants

1996 ◽  
Vol 118 (2) ◽  
pp. 98-101 ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Entropy Generation ◽  
Heat Input ◽  
Power Plants ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Total Entropy ◽  
Minimum Entropy ◽  
Minimum Entropy Generation

It is shown that to maximize the power output of a power plant is equivalent to minimizing the total entropy generation rate associated with the power plant. This equivalence is illustrated by using two of the oldest and simplest models of power plants with heat transfer irreversibilities. To calculate the total entropy generation rate correctly, one must recognize that the optimization process (e.g., the variability of the heat input) requires “room to move,” i.e., an additional, usually overlooked, contribution to the total entropy generation rate.

scholarly journals Multi-Objective Optimization of Braun-Type Exothermic Reactor for Ammonia Synthesis

Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 52
Author(s):  
Tianchao Xie ◽  
Shaojun Xia ◽  
Chao Wang
Keyword(s):  
Entropy Generation ◽  
Flow Rate ◽  
Ammonia Synthesis ◽  
Storage System ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Inlet Temperature ◽  
Total Entropy ◽  
Nsga Ii ◽  
Molar Flow Rate

The exothermic reactor for ammonia synthesis is a primary device determining the performance of the energy storage system. The Braun-type ammonia synthesis reactor is used as the exothermic reactor to improve the heat release rate. Due to the entirely different usage scenarios and design objectives, its parameters need to be redesigned and optimized. Based on finite-time thermodynamics, a one-dimensional model is established to analyze the effects of inlet gas molar flow rate, hydrogen–nitrogen ratio, reactor length and inlet temperature on the total entropy generation rate and the total exothermic rate of the reactor. It’s found that the total exothermic rate mainly depends on the inlet molar flow rate. Furthermore, considering the minimum total entropy generation rate and maximum total exothermic rate, the NSGA-II algorithm is applied to optimize seven reactor parameters including the inlet molar flow rate, lengths and temperatures of the three reactors. Lastly, the optimized reactor is obtained from the Pareto front using three fuzzy decision methods and deviation index. Compared with the reference reactor, the total exothermic rate of the optimized reactor is improved by 12.6% while the total entropy generation rate is reduced by 3.4%. The results in this paper can provide some guidance for the optimal design and application of exothermic reactors in practical engineering.

scholarly journals Heat Transfer and Entropy Generation Evaluation on Molten Salt Tank Foundation with Internal Water Cooling

2020 ◽  
Vol 194 ◽  
pp. 01032
Author(s):  
Shien Sun ◽  
Haihua Luo ◽  
Basher Hassan Al-Kbodi ◽  
Qiang Shen ◽  
Houlei Zhang
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Water Cooling ◽  
Total Entropy ◽  
Local Entropy ◽  
Heat Leakage ◽  
Local Entropy Generation

Molten salt tanks are used to store and release thermal energy. Large heat leakage through the molten salt tank foundation to the ground and high temperature of the foundation are detrimental to long-term operation safety. Here we evaluate the heat transfer and entropy generation characteristics of molten salt tank foundations with internal water cooling. Both laminar and turbulent flows reduce the heat leakage efficiently, while the power consumption for the laminar flow is negligible. The effects of the geometrical parameters are presented. Internal fins in the cooling channels decrease the heat leakage significantly. The total entropy generation rate with foundation cooling is higher than that without foundation cooling. The entropy generation rate in the solid domain is much larger than that in the fluid domain and the flow friction irreversibility is tiny. Larger insulation layer thickness decreases the heat leakage and the total entropy generation rate simultaneously. The local entropy generation rate map helps us identify where the most irreversibility is produced. The largest local entropy generation rate for the design with foundation cooling occurs near the solid-fluid interfaces and is much higher than that without foundation cooling.

Single-phase natural circulation loop using oils and ternary hybrid nanofluids: Steady-state and transient thermo-hydraulics

2020 ◽  
pp. 1-32
Author(s):  
Mayaram Sahu ◽  
Jahar Sarkar ◽  
Laltu Chandra
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Width Ratio ◽  
Total Entropy ◽  
Hybrid Nanofluids

Abstract Steady-state and transient behaviours of single-phase natural circulation loop (SPNCL) are investigated using four thermal oils (Therminol VP1, Paratherm CR, Dowtherm A and Dowtherm Q) and water-based ternary hybrid (various combinations of different nature and shaped nanoparticles: Al2O3, Cu, CNT and Graphene) nanofluids as loop fluid. The influences of nanoparticle volume concentration and loop height to width ratio on the mass flow rate and total entropy generation rate of SPNCL are investigated. Results disclose that ternary hybrid nanofluids enhance flow initiation, reduce fluctuation and are expected to attain a steady-state faster than water. Steady-state mass flow rate increases/decreases for ternary hybrid nanofluid depending on the shape of the nanoparticle and total entropy generation rate decreases as compared to water. Thermal oil shows a higher mass flow rate and total entropy generation rate as compared to water. Al2O3-Cu-CNT-water and paratherm CR show the best result among all ternary hybrid nanofluids and thermal oils, respectively. The nanoparticle shape decides the optimum nanoparticle volume fraction. Increasing the height to width ratio decreases the total entropy generation and upsurges the mass flow rate at specified input power. The optimum height to width ratio depends on fluid.

scholarly journals Heat transfer and Entropy analysis of airflow around an airfoil subjected to an external magnetic field

2020 ◽  
Author(s):  
Hamed Saffarzadeh ◽  
M.H Djavareshkian
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
External Magnetic Field ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Total Entropy ◽  
Field Source ◽  
Flow And Heat Transfer ◽  
Main Components

Abstract In the present study, the thermal Lattice Boltzmann Technique is combined with the Ghost Fluid method to simulate the flow and heat transfer rate around a NACA 0015 airfoil in the presence of an external magnetic field source. It is tried to investigate the mutual effects of the Hartmann and Reynolds numbers as well as the magnetic field angle and the attack angle of the airfoil on the flow and heat transfer characteristics. Besides, the total entropy generation rate of the system was studied through its main components, i.e. entropy generation rate due to friction, heat transfer, and Magneto Hydrodynamics. Therefore, the tests were carried out for various Re and Ha numbers, plus different magnetic field angles and airfoil attack angles, and their influence on the active parameters which are Cd, Cl, and Nu, along with the entropy generation rate of the system,were recorded. The results revealed that with an increment of the Re number the Cd and Cl graphs drop, but the Nu value raises. Also, the total entropy generation rate of the system is at its maximum around\(\gamma =60\).

Theoretical and experimental investigation of an organic Rankine cycle for a waste heat recovery system

2009 ◽  
Vol 223 (5) ◽  
pp. 523-533 ◽  
Author(s):  
W Gu ◽  
Y Weng ◽  
Y Wang ◽  
B Zheng
Keyword(s):  
Heat Source ◽  
Entropy Generation ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Entropy Generation Rate ◽  
Working Fluid ◽  
Total Entropy ◽  
Waste Heat Recovery System ◽  
Cycle Efficiency

This article describes and evaluates an organic Rankine cycle (ORC) for a waste heat recovery system by both theoretical and experimental studies. Theoretical analysis of several working fluids shows that cycle efficiency is very sensitive to evaporating pressure, but insensitive to expander inlet temperature. Second law analysis was carried out using R600a as a working fluid and a flow of hot air as a heat source, which is not isothermal, along the evaporator. The result discloses that the evaporator's internal and external entropy generation is the main source of total entropy generation. The effect of the heat source temperature, evaporating pressure, and evaporator size on the entropy generation rate is also presented. The obtained useful power is directly linked to the total entropy generation rate according to the Gouy—Stodola theorem. The ORC testing system was established and operated using R600a as a working fluid and hot water as a heat source. The maximum cycle efficiency of the testing system is 5.2 per cent, and the testing result also proves that cycle efficiency is insensitive to heat source temperature, but sensitive to evaporating pressure. The entropy result also shows that internal and external entropy of the evaporator is the main source of total entropy generation.

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