Fluid/Thermal Analysis of High Temperature Heat Exchanger and Chemical Decomposer for Hydrogen Production

2007 ◽  
Author(s):  
Valery Ponyavin ◽  
Yitung Chen ◽  
Anthony E. Hechanova ◽  
Merrill Wilson
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
High Temperature ◽  
Heat Exchanger ◽  
Hydrogen Production ◽  
Three Dimensional ◽  
Flow And Heat Transfer ◽  
Temperature Heat ◽  
Improved Design ◽  
Sulfuric Acid Decomposition

This paper presents fluid flow and heat transfer study of a high temperature heat exchanger and chemical decomposer. The decomposer will be used as a part of the plant for hydrogen production. The decomposer is manufactured using fused ceramic layers that allow creation of channels with dimensions below one millimeter. The main purpose for this study is to increase thermal performance of the decomposer which can help to intensify sulfuric acid decomposition rate. Effects of using various channel geometries of the decomposer on the pressure drop are studied as well. A three-dimensional computational model is developed for the investigation of fluid flow and heat transfer in the decomposer. Several different geometries of the decomposer channels such as straight channels, ribbed ground channels, hexagonal channels, and diamond-shaped channels are examined. Based on results of the calculation, the recommendations for the improved design of the decomposer are obtained.

Development of an Advanced High Temperature Heat Exchanger Design for Hydrogen Production

2004 ◽  
Author(s):  
Sundaresan Subramanian ◽  
Roald Akberove ◽  
Yitung Chen ◽  
Anthony E. Hechanova ◽  
Clayton Ray De Losier
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Hydrogen Production ◽  
Numerical Simulations ◽  
Transfer Enhancement ◽  
Heat Exchanger Design ◽  
Temperature Heat ◽  
Fin Thickness ◽  
Offset Strip Fin

This paper deals with the development of an advanced high temperature heat exchanger design for hydrogen production by the sulfur iodine thermochemical cycle from advanced nuclear reactor concepts. The offset strip-fin hybrid plate type compact heat exchanger concept is chosen, and the material of manufacture is the liquid silicon impregnated carbon composite. The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on enhancing heat transfer. The effect of the fin thickness, pitch in flow direction, and the aspect ratio of the offset fins on the flow field and heat transfer are studied in 2-D using Computational Fluid Dynamics (CFD) techniques, and the results are then compared with the analytical calculation results. The preprocessor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT, that is based on the finite volume method is used to produce numerical results. Proper dimensions of the strip fins need to be chosen in order to have an optimized heat transfer enhancement coupled with a reduced pressure drop. The study is conducted with helium gas as the working fluid with varied of Reynolds number values. The flow and heat transfer is considered to become periodically fully developed after a certain entrance length hence numerical simulations were performed using periodic boundary conditions. Two-dimensional numerical simulations were also performed for the whole length of the heat exchanger which has 37 such periodic modules. Comparison study was performed between the cases of fins with rectangular and curved geometry. Attempt has also been made in order to validate the coefficient of fin thickness (Cfin) value using CFD techniques, which has been used in the existing empirical correlations to suit this type of heat exchanger geometry. The model developed in this paper is used to investigate the heat exchanger design parameters in order to find an optimal design.

Modeling and Parametric Study of a Ceramic High Temperature Heat Exchanger and Chemical Decomposer

2006 ◽  
Author(s):  
Valery Ponyavin ◽  
Yitung Chen ◽  
Taha Mohamed ◽  
Mohamed Trabia ◽  
Merrill Wilson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Sulfuric Acid ◽  
High Temperature ◽  
Heat Exchanger ◽  
Three Dimensional ◽  
Ansys Software ◽  
Temperature Heat ◽  
Fluent Software ◽  
Flow Heat ◽  
Chemical Cycle

It is proposed to use ceramic high temperature heat exchanger as a sulfuric acid decomposer for hydrogen production within the sulfur iodine thermo-chemical cycle. The decomposer is manufactured using fused ceramic layers that allow creation of channels with dimensions below one millimeter. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer, stresses and chemical reactions in the decomposer. Fluid, thermal and chemical reaction analyses are performed using FLUENT software. Temperature distribution in the solid is imported to ANSYS software and used together with pressure as the load for stress analysis. Results of this research can be used as a basis for investigation optimal design of the decomposer that can provide maximum chemical decomposition performance while maintaining stresses within design limits.

Transient Analysis of a Ceramic High Temperature Heat Exchanger and Chemical Decomposer

2007 ◽  
Author(s):  
Valery Ponyavin ◽  
Taha Mohamed ◽  
Mohamed Trabia ◽  
Yitung Chen ◽  
Anthony E. Hechanova
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Heat Exchanger ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Failure Criteria ◽  
Operating Conditions ◽  
Finite Element Software ◽  
Micro Channels ◽  
Temperature Heat

Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature heat exchanger and chemical decomposer, which is a part of the Sulphur-Iodine (SI) thermo-chemical cycle. The heat exchanger is expected to operate in the range of 950°C. The proposed design is manufactured using fused ceramic layers that allow creation of micro-channels with dimensions below one millimeter. A proper design of the heat exchanges requires considering possibilities of failure due to stresses under both steady state and transient conditions. Temperature gradients within the heat exchanger ceramic components induce thermal stresses that dominate other stresses. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer and stresses in the decomposer. Temperature distribution in the solid is imported to finite element software and used with pressure loads for stress analysis. The stress results are used to calculate probability of failure based on Weibull failure criteria. Earlier analysis showed that stress results at steady state operating conditions are satisfactory. The focus of this paper is to consider stresses that are induced during transient scenarios. In particular, the cases of startup and shutdown of the heat exchanger are considered. The paper presents an evaluation of the stresses in these two cases.

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