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

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.

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

Entropy ◽

10.3390/e22101104 ◽

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.

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

Entropy ◽

10.3390/e22111214 ◽

2020 ◽

Vol 22 (11) ◽

pp. 1214 ◽

Cited By ~ 1

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.

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NANO-FLUID EFFECTS ON TOTAL ENTROPY GENERATION THROUGH PLATE HEAT EXCHANGERS

Journal of Al-Azhar University Engineering Sector ◽

10.21608/auej.2019.33354 ◽

2019 ◽

Vol 14 (51) ◽

pp. 513-527

Author(s):

M Hefny, ◽

A Hussein, ◽

A Hamed ◽

N Mahmoud

Keyword(s):

Entropy Generation ◽

Heat Exchangers ◽

Total Entropy ◽

Plate Heat ◽

Nano Fluid

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Exergy efficiency design for multi-stream plate-fin heat exchangers based on entropy generation assessment

International Journal of Exergy ◽

10.1504/ijex.2021.10036475 ◽

2021 ◽

Vol 34 (3) ◽

pp. 331

Author(s):

Jianrong Tan ◽

Shuyou Zhang ◽

Jinghua Xu ◽

Mingyu Gao ◽

Tiantian Wang ◽

...

Keyword(s):

Entropy Generation ◽

Heat Exchangers ◽

Exergy Efficiency

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The Thermohydraulic Characteristics and Optimization Study of Radial Porous Heatsinks Using Multi-Objective Computational Method

Journal of Heat Transfer ◽

10.1115/1.4051126 ◽

2021 ◽

Author(s):

Amer Al-damook ◽

Itimad D J Azzawi

Keyword(s):

Heat Transfer ◽

Porous Media ◽

Entropy Generation ◽

Heat Sink ◽

Flow Direction ◽

Inlet Temperature ◽

Conductive Heat ◽

Saturated Porous Media ◽

Total Entropy ◽

Multi Objective

Abstract The use of porous media to improve conductive heat transfer has been at the focus of interest in recent years. Limited studies, however, have focused on heat transfer in radial heat sinks fully and partially saturated porous media with a different arrangement. The current research, therefore, addresses the ability of radial porous heat sink solutions as a development of the above-mentioned investigations to improve the thermohydraulic characteristics and reduce the effect of 2nd thermodynamics law. The response surface method technique (RSM) with ANSYS FLUENT-CFD is accomplished to optimize the thermohydraulic features and the total entropy generation by the multi-objective optimum design for different parameters design such as porosity (Ø), inlet temperature (Tin) and applied heat flux (Q) simultaneously after achieving the optimum porous media arrangement related to the flow direction. The results showed that in terms of the flow direction, the optimum radial porous heat sink of 100%PM model was recognized (fully saturated porous media). Moreover, a significant agreement between the predicted and numerical simulation data for the optimum values is also seen. The optimum and undesirable designs of the thermohydraulic features, the total entropy generation and the optimum thermal management are detected in this investigation.

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Performance Evaluation of Heat Transfer Enhancement for Offset Strip Fins Used in Plate-Fin Heat Exchangers

Journal of Heat Transfer ◽

10.1115/1.4030247 ◽

2015 ◽

Vol 137 (10) ◽

Cited By ~ 2

Author(s):

Yujie Yang ◽

Yanzhong Li ◽

Biao Si ◽

Jieyu Zheng

Keyword(s):

Heat Transfer ◽

Heat Transfer Enhancement ◽

Entropy Generation ◽

Heat Exchangers ◽

Operating Conditions ◽

Geometrical Parameters ◽

Distribution Factor ◽

Transfer Enhancement ◽

Entropy Generation Number ◽

Fin Thickness

In general, offset strip fin (OSF) used in plate-fin heat exchangers is able to provide a greater heat transfer coefficient than the plain fin with the same cross section, but it will also cause the increase of flow friction and pressure drop owing to the fin offset. A new parameter denoted by Ψ*, called relative entropy generation distribution factor, is proposed in this paper to comprehensively reflect the thermodynamic performance of different passage structures in plate-fin heat exchanger. This parameter physically represents relative changes of entropy generation and irreversibility, which are induced by both heat transfer and friction loss due to the utilization of OSF fins. The high magnitude of Ψ* represents a beneficial contribution of OSF with higher degree of the heat transfer enhancement. The proposed method is more reasonable and comprehensive than either the conventional augmentation entropy generation number, Ns,a, or the entropy generation distribution factor, ψ, to evaluate the heat transfer enhancement for OSF cores subject to various operating conditions. With the proposed method, the relative effects of the geometrical parameters of OSF fins, such as the fin thickness-to-height ratio α, fin density γ, and fin thickness-to-length ratio δ, on the heat transfer enhancement are discussed in detail. The results show that relatively small δ results in a better performance, while the parameter α or γ, which contribute to a higher degree of heat transfer enhancement of OSF fin, should be determined after the selection of the other two geometric parameters.

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Exergy efficiency design for multi-stream plate-fin heat exchangers based on entropy generation assessment

International Journal of Exergy ◽

10.1504/ijex.2021.113848 ◽

2021 ◽

Vol 34 (3) ◽

pp. 331

Author(s):

Jinghua Xu ◽

Mingyu Gao ◽

Tiantian Wang ◽

Qianyong Chen ◽

Shuyou Zhang ◽

...

Keyword(s):

Entropy Generation ◽

Heat Exchangers ◽

Exergy Efficiency

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Entropy Generation in Counter Flow Gas to Gas Heat Exchangers

Journal of Heat Transfer ◽

10.1115/1.2130407 ◽

2005 ◽

Vol 128 (1) ◽

pp. 87-92 ◽

Cited By ~ 21

Author(s):

Hany Ahmed Mohamed

Keyword(s):

New York ◽

Heat Exchanger ◽

Entropy Generation ◽

Heat Exchangers ◽

Operating Conditions ◽

Working Fluid ◽

Counter Flow ◽

Thermodynamic Irreversibility ◽

Flow Imbalance ◽

New Equation

Analysis of heat transfer and fluid flow thermodynamic irreversibilities is realized on an example of a counter flow double pipe heat exchanger utilizing turbulent air flow as a working fluid. During the process of mathematical model creation and for different working and constructing limitations, total thermodynamic irreversibility is studied. The present work proves that the irreversibility occurred due to unequal capacity flow rates (flow imbalance irreversibility). It is concluded that the heat exchanger should be operated at effectiveness, ε, greater than 0.5 and the well operating conditions will be achieved when ε approaches one where low irreversibility is expected. A new equation is adopted to express the entropy generation numbers for imbalanced heat exchangers of similar design with smallest deviation from the exact value. The results obtained from the new equation are compared with the exact values and with those obtained by Bejan (Bejan, A., 1997, Advanced Engineering Thermodynamics, Wiley, New York).

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