scholarly journals Minimization of Entropy Generation Rate in Hydrogen Iodide Decomposition Reactor Heated by High-Temperature Helium

Entropy ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 82
Author(s):  
Rui Kong ◽  
Lingen Chen ◽  
Shaojun Xia ◽  
Penglei Li ◽  
Yanlin Ge
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Hydrogen Production ◽  
Performance Optimization ◽  
Reaction System ◽  
Decomposition Reaction ◽  
Hydrogen Iodide ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Inlet Temperature

The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors.

MHD and nonlinear thermal radiation effects on hybrid nanofluid past a wedge with heat source and entropy generation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fazle Mabood ◽  
Anum Shafiq ◽  
Waqar Ahmed Khan ◽  
Irfan Anjum Badruddin
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Heat Source ◽  
Thermal Radiation ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Hybrid Nanofluid ◽  
Nonlinear Thermal Radiation ◽  
Content Type

Purpose This study aims to investigate the irreversibility associated with the Fe3O4–Co/kerosene hybrid-nanofluid past a wedge with nonlinear radiation and heat source. Design/methodology/approach This study reports the numerical analysis of the hybrid nanofluid model under the implications of the heat source and magnetic field over a static and moving wedge with slips. The second law of thermodynamics is applied with nonlinear thermal radiation. The system that comprises differential equations of partial derivatives is remodeled into the system of differential equations via similarity transformations and then solved through the Runge–Kutta–Fehlberg with shooting technique. The physical parameters, which emerges from the derived system, are discussed in graphical formats. Excellent proficiency in the numerical process is analyzed by comparing the results with available literature in limiting scenarios. Findings The significant outcomes of the current investigation are that the velocity field uplifts for higher velocity slip and magnetic strength. Further, the heat transfer rate is reduced with the incremental values of the Eckert number, while it uplifts with thermal slip and radiation parameters. An increase in Brinkmann’s number uplifts the entropy generation rate, while that peters out the Bejan number. The results of this study are of importance involving in the assessment of the effect of some important design parameters on heat transfer and, consequently, on the optimization of industrial processes. Originality/value This study is original work that reports the hybrid nanofluid model of Fe3O4–Co/kerosene.

High-Temperature Potential of Uncooled Radial Turbines

1978 ◽  
Vol 100 (2) ◽  
pp. 294-302 ◽  
Author(s):  
D. J. Arnold ◽  
O. E. Balje
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Experimental Investigations ◽  
Inlet Temperature ◽  
High Reaction ◽  
Temperature Potential ◽  
Axial Turbines ◽  
Radial Turbines

Radial turbines are used predominantly for turbo-charges where the geometry is frequently compromised to favor low fabrications costs. Theoretical as well as experimental investigations have shown that the efficiency potential of radial turbines is as high as the efficiency potential of high reaction axial turbines. Structural and heat transfer studies on radial turbines show that the highest stresses in “deep scalloped” radial rotors occur at locations where the metal temperature is considerably lower than at rotor inlet. Thus the maximum allowable gas inlet temperature for radial turbines is several hundred degrees higher than for high-reaction axial turbines. This difference tends to increase with increasing expansion ratios, at least up to expansion ratios of 10:1. Since the thermal efficiency of typical gas turbine cycles increases with increasing gas temperatures and increasing expansion ratios, it results that the application of uncooled radial turbines will yield cycle efficiencies which are not obtainable with uncooled axial turbines.

Investigation of a High-Temperature Packed-Bed Sensible Heat Thermal Energy Storage System With Large-Sized Elements

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Sarada Kuravi ◽  
Jamie Trahan ◽  
Yogi Goswami ◽  
Chand Jotshi ◽  
Elias Stefanakos ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Energy Storage ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Packed Bed ◽  
Inlet Temperature ◽  
Prototype System ◽  
Sensible Heat

A high-temperature, sensible heat thermal energy storage (TES) system is designed for use in a central receiver concentrating solar power plant. Air is used as the heat transfer fluid and solid bricks made out of a high storage density material are used for storage. Experiments were performed using a laboratory-scale TES prototype system, and the results are presented. The air inlet temperature was varied between 300 °C to 600 °C, and the flow rate was varied from 50 cubic feet per minute (CFM) to 90 CFM. It was found that the charging time decreases with increase in mass flow rate. A 1D packed-bed model was used to simulate the thermal performance of the system and was validated with the experimental results. Unsteady 1D energy conservation equations were formulated for combined convection and conduction heat transfer and solved numerically for charging/discharging cycles. Appropriate heat transfer and pressure drop correlations from prior literature were identified. A parametric study was done by varying the bed dimensions, fluid flow rate, particle diameter, and porosity to evaluate the charging/discharging characteristics, overall thermal efficiency, and capacity ratio of the system.

Performance Optimization of Compact Ceramic High Temperature Heat Exchangers

2007 ◽  
Author(s):  
Q. Y. Chen ◽  
M. Zeng ◽  
D. H. Zhang ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Performance Optimization ◽  
Heat Exchangers ◽  
Radiation Heat Transfer ◽  
Surface Radiation ◽  
Radiation Heat ◽  
High Temperature Side ◽  
Temperature Heat

In the present paper, the compact ceramic high temperature heat exchangers with parallel offset strip fins and inclined strip fins (inclined angle β = 0∼70°) are investigated with CFD method. The numerical simulations are carried out for high temperature (1500°C), without and with radiation heat transfer, and the periodic boundary is used in transverse direction. The fluid of high temperature side is the standard flue gas. The material of heat exchanger is SiC. NuS-G.R(with surface and gaseous radiation heat transfer) is averagely higher than NuNo.R (without radiation heat transfer) by 7% and fS-G.R is averagely higher than fNo.R by 5%. NuS-G.R(with surface and gaseous radiation heat transfer) is averagely higher than NuS.R (with only surface radiation heat transfer) by 0.8% and fS-G.R is averagely higher than fS.R by 3%. The thermal properties have significantly influence on the heat transfer and pressure drop characteristics, respectively. The heat transfer performance of the ceramic heat exchanger with inclined fins (β = 30°) is the best.

scholarly journals Optimization of absorption systems: case of the refrigerators and heat pumps

2019 ◽  
Vol Volume 30 - 2019 - MADEV... ◽  
Author(s):  
René Tchinda ◽  
Paiguy Armand Ngouateu Wouagfack
Keyword(s):  
Performance Optimization ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Working Fluid ◽  
Ecological Design ◽  
Ecological Performance ◽  
Heating Load ◽  
Main Components

The new thermo-ecological performance optimization of absorption is investigated by taking the ecological coefficient of performance ECOP as an objective function. ECOP has been expressed in terms of the temperatures of the working fluid in the main components of the system. The maximum of ECOP and the corresponding optimal temperatures of the working fluid and other optimal performance design parameters such as coefficient of performance, specific cooling load of absorption refrigerators, specific heating load of absorption heat pumps, specific entropy generation rate and the distributions of the heat exchanger areas have been derived analytically. The obtained results may provide a general theoretical tool for the ecological design of absorption refrigerators and heat pumps.

Design of Cryogenic Centrifugal Compressor Stages With Heat Transfer Considerations

2019 ◽  
Author(s):  
Jin Xiong ◽  
Yingkun Zhang ◽  
Penghua Guo ◽  
Jingyin Li
Keyword(s):  
Heat Transfer ◽  
Centrifugal Compressor ◽  
Design Method ◽  
Superconducting Magnet ◽  
High Energy ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Outlet Section ◽  
Heat Leakage ◽  
Stage Performance

Abstract The large superconducting magnet are widely used and play an important role in nuclear fusion device, high-energy accelerator, space target infrared and other forefront fields. In this paper, we design several cryogenic centrifugal compressor stages for helium refrigerator with 3.3K∼11K inlet temperature, used in exhausting the low-pressure and low-temperature saturated helium steam, further producing superfluid helium and cooling the large superconducting magnet. Due to the cryogenic compressor running environment and the internal structure, about 30W heat leakage from impeller hubs and the end of shafts into the flow passages are unavoidable, and it is necessary to consider this heat leakage in the centrifugal compressor impeller design. Firstly, adding the heat leakage into thermodynamic process and centrifugal compressor effective formula, then adjusting the inlet and outlet design parameters according to the heat transfer rate and make the preliminarily designs of each stage of the compressor. Four different methods for varying p design condition parameters are compared by CFD simulation. The 3-D impellers are designed by the Streamline Curvature Method, and the vaneless diffusers and volutes are designed by the inlet and outlet section aerodynamic parameters. When the best design method is determined, the blade profiles are further adjusted in order to improve the stage performance. Finally, the characteristic curves under variable working conditions and the generalized stage performance curves of each stage are calculated. In this paper, we delve into a high efficiency centrifugal compressor stage design method with the consideration of heat transfer effect. In the next step, more running data will be obtained after the further experiments and the long-term operation.

Catalytic Properties of Ni3Al for Hydrogen Production Reactions

2005 ◽  
Vol 475-479 ◽  
pp. 755-758 ◽  
Author(s):  
Ya Xu ◽  
Satoshi Kameoka ◽  
Kyosuke Kishida ◽  
Masahiko Demura ◽  
An Pong Tsai ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Hydrogen Production ◽  
Catalytic Properties ◽  
High Strength ◽  
Decomposition Reaction ◽  
Methanol Decomposition ◽  
Ni Catalyst ◽  
Chemical Processing ◽  
Raney Ni

Ni3Al has attractive high temperature properties, such as high strength and good oxidation/corrosion resistance, and is possible to be used for high temperature chemical processing and manufacture. Until now, the catalytic properties of Ni3Al were rarely investigated since the leaching of aluminum from Ni3Al is difficult to obtain a porous Raney-Ni compared to NiAl3 and Ni2Al3. In the present work, the catalytic properties of Ni3Al were examined for hydrogen production reactions from methanol. It was found that alkali-leached Ni3Al showed high activity for methanol decomposition (CH3OH→ 2H2+CO). Furthermore, Ni3Al catalysts suppress the formation of methane, i.e. they show higher selectivity for the methanol decomposition reaction than Ni catalyst. These results indicate a possibility for Ni3Al used as a catalyst for hydrogen production reaction.

Experimental Study on Application of Heat Transfer Enhancement Method Using Porous Material With High Porosity

2009 ◽  
Author(s):  
Tetsuaki Takeda ◽  
Koichi Ichimiya
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Hydrogen Production ◽  
Heat Transfer Enhancement ◽  
Production System ◽  
High Porosity ◽  
Transfer Enhancement ◽  
Steam Reformer ◽  
Nuclear Heat ◽  
Helium Gas

A technology development of a hydrogen production system by nuclear heat is being performed as a heat application system of the Very High Temperature Reactor (VHTR) in worldwide. As for the development of the coupling technology between the VHTR and the hydrogen production system, Japan Atomic Energy Agency had carried out a coupling technology test using a steam reforming process by natural gas. In the hydrogen production system by nuclear heat, the catalyst tube of the steam reformer is heated by the high temperature helium gas from the intermediate heat exchanger (IHX). There are several methods for heat transfer enhancement. For example, there are attaching various fins on the heat transfer surface, processing the surface roughly, and so on. Disk type fins are attached on the outside surface of the catalyst tube. The catalyst tube is inserted into the guide tube to increase an amount of heat transferred from the high temperature helium gas. However, it has to take into consideration the deterioration of the structure strength by attaching the fins on the tube surface with the design of the steam reformer. The objective of this study is to clarify performances of a method for heat transfer enhancement using porous material with high porosity by an experiment. The experiment has been performed using an apparatus which simulated the passage structure of the steam reformer to obtain characteristics of heat transfer.

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