scholarly journals Numerical Investigation into the Development Performance of Gas Hydrate by Depressurization Based on Heat Transfer and Entropy Generation Analyses

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1212 ◽  
Author(s):  
Bo Li ◽  
Wen-Na Wei ◽  
Qing-Cui Wan ◽  
Kang Peng ◽  
Ling-Ling Chen
Keyword(s):  
Heat Transfer ◽  
Energy Loss ◽  
Entropy Production ◽  
Entropy Generation ◽  
Gas Hydrate ◽  
Methane Hydrate ◽  
Dynamic Properties ◽  
Entropy Production Rate ◽  
Entropy Flow ◽  
Hydrate Reservoir

The purpose of this study is to analyze the dynamic properties of gas hydrate development from a large hydrate simulator through numerical simulation. A mathematical model of heat transfer and entropy production of methane hydrate dissociation by depressurization has been established, and the change behaviors of various heat flows and entropy generations have been evaluated. Simulation results show that most of the heat supplied from outside is assimilated by methane hydrate. The energy loss caused by the fluid production is insignificant in comparison to the heat assimilation of the hydrate reservoir. The entropy generation of gas hydrate can be considered as the entropy flow from the ambient environment to the hydrate particles, and it is favorable from the perspective of efficient hydrate exploitation. On the contrary, the undesirable entropy generations of water, gas and quartz sand are induced by the irreversible heat conduction and thermal convection under notable temperature gradient in the deposit. Although lower production pressure will lead to larger entropy production of the whole system, the irreversible energy loss is always extremely limited when compared with the amount of thermal energy utilized by methane hydrate. The production pressure should be set as low as possible for the purpose of enhancing exploitation efficiency, as the entropy production rate is not sensitive to the energy recovery rate under depressurization.

scholarly journals Effect of corrugated minichannel variable width on entropy generation for convective heat transfer of alpha-Alumina-water nanofluid

2021 ◽  
Vol 2053 (1) ◽  
pp. 012016
Author(s):  
N M Muhammad ◽  
N A C Sidik ◽  
A Saat ◽  
Y Asako ◽  
W M A A Japar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Entropy Production ◽  
Convective Heat ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Thermal Systems ◽  
Volume Fractions ◽  
Thermal Entropy ◽  
Alpha Alumina

Abstract Energy management and sustainability in thermal systems require maximum utilization of resources with minimal losses. However, it is rarely unattainable due to the ever-increasing need for a high-performance system combined with device size reduction. The numerical study examined convective heat transfer of an alpha-Alumina-water nanofluid in variable-width corrugated minichannel heat sinks. The objective is to study the impact of nanoparticle volume fractions and flow area variation on the entropy generation rate. The determining variables are 0.005 – 0.02 volume fractions, the fluid velocity 3 – 5.5 m/s and heat flux of 85 W/cm2. The numerical results show an acceptable correlation with the experiment results. The results indicate the thermal entropy production drop with an increase in nanoparticles volume fraction. Contrastingly, the frictional resistance entropy suggests the opposite trend due to the turbulence effect on the fluid viscosity. The induction of Alumina-Water nanofluid with enhanced thermal conductivity declined the entropy generation rate compared to water alone. The increase in width ratio by 16% between the cases translates to at least a 9% increase in thermal entropy production. The outcome of this study can provide designers and operators of thermal systems more insight into entropy management in corrugated heatsinks.

Analysis on the Flow Process of Hot Oil in the Organic Heat Transfer Material Heater Based on Finite Time Thermodynamics

2011 ◽  
Vol 250-253 ◽  
pp. 2979-2983 ◽  
Author(s):  
Wei Li Gu ◽  
Yuan Quan Liu
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Production Rate ◽  
Finite Time ◽  
Entropy Production Rate ◽  
Physical Parameters ◽  
Finite Time Thermodynamics ◽  
Flow Process ◽  
Dissipation Effect ◽  
Rate Of Dissipation

Analyses the flow process of hot oil in the organic heat transfer material heater based on finite time thermodynamics for the first time, obtains the entropy production rate which includes entropy production rate of dissipation effect and entropy production rate of potential difference, analyses the influence of flow pattern, physical parameters, structure and operation of the organic heat transfer material heater on the entropy production rate of dissipation effect, illustrates the influence of related parameters including Renold number, velocity, viscosity and pipe diameter on the entropy production rate of dissipation effect, and points out the type of hot oil must be considered to decrease the entropy production rate of dissipation effect and the velocity must be control under the premise of avoiding overheat.

Effect of Wall Heat Flux on Entropy Generation in Turbulent Mixed Convection Heat Transfer of a Pipe Flow With Highly Variable Properties

2010 ◽  
Author(s):  
Majid Bazargan ◽  
Mahdi Mohseni
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Entropy Production ◽  
Entropy Generation ◽  
Convection Heat Transfer ◽  
Wall Heat Flux ◽  
Convection Heat ◽  
The Heat Transfer Coefficient

There are many engineering systems with working fluids which have properties varying significantly with temperature. This causes the effect of the wall heat flux on the velocity and temperature fields to become larger with respect to the constant property flows. In this study the effect of the wall heat flux on the entropy generation in the mixed turbulent convection heat transfer of a fluid flow with high property variations has been investigated. The local and total entropy generation is calculated. In addition, the region in which the entropy production is larger has been determined. Furthermore, the contribution of each of the mechanisms of entropy production which is depended on the wall heat flux is determined. It should be noted that the implementation of different heat fluxes at the tube wall affects all mechanisms of entropy generation. The results show that the bulk entropy generation reaches a minimum value when the heat transfer coefficient has a maximum value. The wall heat flux also has an opposite effect on the heat transfer coefficient and entropy generation which is a favorable result.

scholarly journals Heat Transfer Characteristics and Entropy Generation in Cascaded Air Cavity

2018 ◽  
Vol 7 (4) ◽  
pp. 2533
Author(s):  
Said M. A. Ibrahim ◽  
Salah El-Din El-Morshedy ◽  
Abdelfatah Abdelmaksoud
Keyword(s):  
Heat Transfer ◽  
Energy Loss ◽  
Thermodynamic Analysis ◽  
Entropy Generation ◽  
Temperature Difference ◽  
Irreversible Process ◽  
Thermodynamic Process ◽  
Heat Transfer Characteristics ◽  
Vertical Cavity ◽  
Microscopic Energy

In reality every thermodynamic process is irreversible process. All sort of processes have this kind of macroscopic and microscopic energy loss. Every system in a thermodynamic process, generates finite amount of entropy. The entropy generation is studied for vertical cavity with different configurations. The effect of cavity walls temperature difference, Cavity cascading, and cascading positions on the overall values of entropy generation is reported. An important analogy between this work and thermodynamic analysis of Carnot is observed.

Entropy Generation Minimization in Dimethyl Ether Synthesis: A Case Study

2018 ◽  
Vol 43 (2) ◽  
pp. 111-120 ◽  
Author(s):  
Diego Kingston ◽  
Adrián César Razzitte
Keyword(s):  
Entropy Production ◽  
Dimethyl Ether ◽  
Entropy Generation ◽  
Process Intensification ◽  
Entropy Production Rate ◽  
Efficient Operation ◽  
Operating Variables ◽  
Entropy Generation Minimization ◽  
Dimethyl Ether Synthesis ◽  
Plant Equipment

AbstractEntropy generation minimization is a method that helps improve the efficiency of real processes and devices. In this article, we study the entropy production (due to chemical reactions, heat exchange and friction) in a conventional reactor that synthesizes dimethyl ether and minimize it by modifying different operating variables of the reactor, such as composition, temperature and pressure, while aiming at a fixed production of dimethyl ether. Our results indicate that it is possible to reduce the entropy production rate by nearly 70 % and that, by changing only the inlet composition, it is possible to cut it by nearly 40 %, though this comes at the expense of greater dissipation due to heat transfer. We also study the alternative of coupling the reactor with another, where dehydrogenation of methylcyclohexane takes place. In that case, entropy generation can be reduced by 54 %, when pressure, temperature and inlet molar flows are varied. These examples show that entropy generation analysis can be a valuable tool in engineering design and applications aiming at process intensification and efficient operation of plant equipment.

scholarly journals Comprehensive Criteria for the Extrema in Entropy Production Rate for Heat Transfer in the Linear Region of Extended Thermodynamics Framework

Axioms ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 113
Author(s):  
George D. Verros
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Production Rate ◽  
Time Derivative ◽  
Local Heat Transfer ◽  
Extended Thermodynamics ◽  
Irreversible Processes ◽  
Entropy Production Rate ◽  
Transfer Coefficients ◽  
Linear Region

In this work comprehensive criteria for detecting the extrema in entropy production rate for heat transfer by conduction in a uniform body under a constant volume in the linear region of Extended Thermodynamics Framework are developed. These criteria are based on calculating the time derivative of entropy production rate with the aid of well-established engineering principles, such as the local heat transfer coefficients. By using these coefficients, the temperature gradient is replaced by the difference of this quantity. It is believed that the result of this work could be used to further elucidate irreversible processes.

Gas Hydrate Decomposition Rate in Flowing Water

2006 ◽  
Vol 129 (2) ◽  
pp. 102-106 ◽  
Author(s):  
Ryokichi Hamaguchi ◽  
Yuki Nishimura ◽  
Gen Inoue ◽  
Yosuke Matsukuma ◽  
Masaki Minemoto
Keyword(s):  
Heat Transfer ◽  
Gas Hydrate ◽  
Decomposition Rate ◽  
Methane Hydrate ◽  
Lattice Gas ◽  
Production Systems ◽  
Simulation Method ◽  
Flowing Water ◽  
Public Attention ◽  
Hydrate Decomposition

The development of methane hydrate (MH), which exists under the ocean floor, has recently been brought to public attention. However, the production technology has not yet been established. It is important to understand the decomposition phenomenon of MH for an investigation of the safety and the profitability of production systems. In this research, the gas hydrate decomposition rate in flowing water was measured using HCFC141b hydrate as a substitute for MH. When the water temperature was higher than the boiling point of the decomposition gas, it was observed that the decomposition gas increased the decomposition rate. Moreover, the decomposition phenomenon was simulated by the lattice gas automaton method in order to establish the technique which analytically estimates the decomposition rate. The validity of the simulation method was shown by comparing the experiments. Furthermore, the formula between Reynolds number and Nusselt number was obtained, which express the heat transfer around the gas hydrate lump.

Experimental Study on the Effect of Gas Hydrate Content on Heat Transfer

2015 ◽  
Author(s):  
Remi-Erempagamo T. Meindinyo ◽  
Runar Bøe ◽  
Thor Martin Svartås ◽  
Silje Bru
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Ethylene Oxide ◽  
Deep Water ◽  
Gas Hydrate ◽  
Atmospheric Pressure ◽  
Methane Hydrate ◽  
Hydrate Formation ◽  
Equilibrium Temperature ◽  
Gas Hydrate Formation

Gas hydrates are the foremost flow assurance issue in deep water operations. Since heat transfer is a limiting factor in gas hydrate formation processes, a better understanding of its relation to hydrate formation is important. This work presents findings from experimental study of the effect of gas hydrate content on heat transfer through a cylindrical wall. The experiments were carried out at temperature conditions similar to those encountered in flowlines in deep water conditions. Experiments were conducted on methane hydrate, Tetrahydrofuran hydrate, and ethylene oxide hydrate respectively in stirred cylindrical high pressure autoclave cells. Methane hydrate was formed at 90 bars (pressure), and 8°C, followed by a cooling/heating cycle in the range of 8°C → 4°C → 8°C. Tetrahydrofuran (THF) and ethylene oxide (EO) hydrates were formed at atmospheric pressure and system temperature of 1°C in contact with atmospheric air. This was followed by a heating/cooling cycle within the range of 1°C → 4°C → 1°C, since the hydrate equilibrium temperature of THF hydrate is 4.98°C in contact with air at atmospheric pressure. The experimental conditions of the latter hydrate formers were more controlled, given that both THF and EO are miscible with water. We found in all cases a general trend of decreasing heat transfer coefficient of the cell content with increasing concentration of hydrate in the cell, indicating that hydrate formation creates a heat transfer barrier. The hydrate equilibrium temperature seemed to change with a change in the stoichiometric concentration of THF and EO. While the methane hydrate cooling/heating cycles were performed under quiescent conditions, the effect of stirring was investigated for the latter hydrate formers.

Energy Loss and Entropy Generation Analysis in Fundamental Convective Heat Transfer Problems

2005 ◽  
Author(s):  
S. R. Javadinejhad
Keyword(s):  
Heat Transfer ◽  
Energy Loss ◽  
Entropy Generation ◽  
Circular Cross Section ◽  
Dimensionless Number ◽  
Parallel Plates ◽  
Heat Transfer Characteristics ◽  
Total Heat Transfer ◽  
Transfer Problems ◽  
Steady Laminar

Energy loss characteristics of heat transfer and fluid flow due to forced convection of steady laminar flow of incompressible fluid inside channel with circular cross section and channel made of two parallel plates is analyzed. Energy loss profiles and heat transfer characteristics for different problems have been discussed. In each case energy loss due to heat transfer effect and fluid friction have been drived analytically. For energy loss calculations a new dimensionless number have been introduced that is the energy loss to total heat transfer rate ratio. The energy loss dimensionless number behavior have been compared with entropy generation dimensionless number behavior for various problems.

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