Performance Evaluation of Dynamic Model of Compact Heat Exchange Reformer for High-Temperature Fuel Cell Systems

2013 ◽  
Vol 11 (1) ◽  
Author(s):  
Jeongpill Ki ◽  
Daejong Kim
Keyword(s):  
Steady State ◽  
Heat Exchanger ◽  
Fuel Cell ◽  
Heat Exchange ◽  
Dynamic Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Thermal Dynamics ◽  
Internal Reforming ◽  
Experimental Apparatus

Solid oxide fuel cell (SOFC) systems are the most advanced power generation system with the highest thermal efficiency. The current trend of research on the SOFC systems is focused on multikilowatt scale systems, which require either internal reforming within the stack or a compact external reformer. Even if the internal reforming within the SOFC stack allows compact system configuration, it causes significant and complicated temperature gradients within the stack, due to endothermic reforming reactions and exothermic electrochemical reactions. As an alternative solution to the internal reforming, an external compact heat exchange reformer (CHER) is investigated in this work. The CHER is based on a typical plate-fin counterflow or coflow heat exchanger platform, and it can save space without causing large thermal stress and degradation to the SOFC stack (i.e., eventually reducing the overall system cost). In this work, a previously developed transient dynamic model of the CHER is validated by experiments. An experimental apparatus, which comprises the CHER, air heater, gas heater, steam generator, several mass flow controllers, and controller cabinet, was designed to investigate steady state reforming performance of the CHER for various hot air inlet temperatures (thermal energy source) and steam to carbon ratios (SCRs). The transient thermal dynamics of the CHER was also measured and compared with simulations when the CHER is used as a heat exchanger with inert gas. The measured transient dynamics of CHER matches very well with simulations, validating the heat transfer model within the CHER. The measured molar fractions of reformate gases at steady state also agree well with the simulations validating the used reaction kinetics. The transient CHER model can be easily integrated into a total integrated SOFC system, and the model can be also used for optimal design of similar CHERs and provides a guideline to select optimal operating conditions of the CHERs and the integrated SOFC system.

Dynamic Analysis and Control of a Planar IT-SOFC System

2009 ◽  
Author(s):  
A. Salogni ◽  
P. Iora ◽  
S. Campanari
Keyword(s):  
Steady State ◽  
Fuel Cell ◽  
Dynamic Model ◽  
Characteristic Curve ◽  
Cell System ◽  
Internal Reforming ◽  
Internal Cell ◽  
Layer Region ◽  
Air Channels ◽  
And Control

This paper analyzes the dynamic behaviour of a 5 kW fuel cell system based on planar co-flow Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) stack, with internal reforming. The system is composed by the SOFC stack, a combustor of the cell exhausts, two heat exchangers for fuel and air preheating and the related control valves, where the air temperature at the stack exit and the fuel utilization is controlled by means of a PI (proportional integral) device. The model of the stack is based on a lumped parameters dynamic model of a single cell, which is composed of the fuel and air channels, the electrochemically active three layer region representative of the anode, the cathode and the electrolyte. The stack model is first used here for a qualitative steady-state validation, reproducing the cell characteristic curve. Then it is presented the dynamic model of the system, which has been implemented using an a-causal software based on the open-source Modelica modelling language, which allows for future integration in complex power-plant configurations. After a description of the plant layout and of the dynamic model, we present and discuss the results obtained by applying the PI controls to different load changes and with different tuning of the controller parameters, evidencing the amplitudes of load changes, the extent of the transient phase to the new steady-state conditions, the internal cell temperature distribution and the thermal gradients along the PEN structure, giving the possibilities to adapt the control system to the requirements of specific SOFC technologies.

Development of a Ceramic Heat Exchanger for Application as Solid Oxide Fuel Cell Cathode Air Preheater

2016 ◽  
Author(s):  
José Luis Córdova ◽  
Hooshang Heshmat
Keyword(s):  
Heat Exchanger ◽  
Fuel Cell ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Solid Oxide Fuel Cell ◽  
Ceramic Material ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Air Preheater

A ceramic heat exchanger with high effectiveness and low-pressure drop is being developed for application as a cathode air preheater for a Solid Oxide Fuel Cell (SOFC). At the operating conditions of SOFCs, typical metallic alloys as those used in commercial heat exchangers may undergo chromium volatilization, which is a known cathode degradation mechanism that reduces SOFC performance and life. Use of ceramics such as alumina or alumina-silicate instead of chromium-containing metal is one approach to eliminate the effects of chromium on the SOFC cathode. This project leverages the geometric design of a heat exchanger previously prototyped and tested, and demonstrated to have a nearly constant heat transfer effectiveness of 92% with low pressure drop [1], to fabricate a novel heat exchanger made from a ceramic material. This paper calculates heat exchanger performance requirements based on state of the art SOFC operating conditions, presents a thermal-based tradeoff analysis for ceramic material selection, and presents a modular heat exchanger and its heat exchange elements. The modular concept presented allows for incremental aggregation of modules to target a broad range of operating conditions typical of present and upcoming SOFC applications (e.g., 25 to 400 kWe). A fabricated sample ceramic heat exchange element is shown to demonstrate the viability of the concept for a real SOFC application.

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.

Internal Reforming Solid Oxide Fuel Cell Gas Turbine Combined Cycles (IRSOFC-GT): Part B — Exergy and Thermoeconomic Analyses

2001 ◽  
Author(s):  
Aristide F. Massardo ◽  
Loredana Magistri
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Specific Work ◽  
Oxide Fuel ◽  
Internal Reforming ◽  
System Pressure ◽  
Combined Cycles

The aim of this work is to investigate the performance of Internal Reforming Solid Oxide Fuel Cell (IRSOFC) and Gas Turbine (GT) combined cycles. A mathematical model of the IRSOFC steady-state operation was presented in Part A of this work (Massardo and Lubelli, 1998), coupled to the thermodynamic analysis of a number of proposed IRSOFC-GT combined cycles, taking into account the influence of several technological constraints. In the second part of this work, both an exergy and a thermoeconomic analysis of the proposed cycles have been carried out using the TEMP code developed by the Author (Agazzani and Massardo, 1997). A suitable equation for IRSOFC cost evaluation based on cell geometry and performance has been proposed and employed to evaluate the electricity generation cost of the proposed combined systems. The results are presented and the influence of several parameters is discussed: external reformer operating conditions, fuel to air ratio, cell current density, compressor pressure ratio, etc. Diagrams proposed by the Author (Massardo and Scialo’, 2000) for cost vs. efficiency, cost vs. specific work, and cost vs. system pressure are also presented and discussed.

Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants

2016 ◽  
Author(s):  
Adrian S. Sabau ◽  
Ali H. Nejad ◽  
James W. Klett ◽  
Adrian Bejan ◽  
Kivanc Ekici
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Cost Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Length Scale ◽  
Entrance Length ◽  
Scale Levels

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.

Internal Reforming Solid Oxide Fuel Cell Gas Turbine Combined Cycles (IRSOFC-GT)—Part II: Exergy and Thermoeconomic Analyses

2002 ◽  
Vol 125 (1) ◽  
pp. 67-74 ◽  
Author(s):  
A. F. Massardo
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Specific Work ◽  
Oxide Fuel ◽  
Internal Reforming ◽  
System Pressure ◽  
Combined Cycles

The aim of this work is to investigate the performance of internal reforming solid oxide fuel cell (IRSOFC) and gas turbine (GT) combined cycles. A mathematical model of the IRSOFC steady-state operation was presented in Part I of this work coupled to the thermodynamic analysis of a number of proposed IRSOFC-GT combined cycles, taking into account the influence of several technological constraints. In the second part of this work, both an exergy and a thermoeconomic analysis of the proposed cycles have been carried out using the TEMP code developed by the author. A suitable equation for IRSOFC cost evaluation based on cell geometry and performance has been proposed and employed to evaluate the electricity generation cost of the proposed combined systems. The results are presented and the influence of several parameters is discussed: external reformer operating conditions, fuel-to-air ratio, cell current density, compressor pressure ratio, etc. Diagrams proposed by the author for cost versus efficiency, cost versus specific work, and cost versus system pressure are also presented and discussed.

scholarly journals Three-Dimensional Based Model of a Planar SOFC Fuelled by Biomass Gas

2006 ◽  
Author(s):  
Stefano Cordiner ◽  
Massimo Feola ◽  
Vincenzo Mulone ◽  
Fabio Romanelli
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Electrochemical Reaction ◽  
Electrical Response ◽  
Operating Conditions ◽  
Cell Performance ◽  
Gas Composition ◽  
Minimization Method ◽  
Fuel Cell Performance ◽  
Internal Reforming

Efficient and low polluting production of electricity and heat is an issue which cannot be postponed. Fuel cells, which convert the chemical energy stored in a fuel into electrical and thermal energy, are an efficient solution for such a problem. These devices rely on the combination of hydrogen and oxygen into water: oxygen is extracted from the air while hydrogen can be obtained from either fossil fuels or renewable sources. The use of biomass as hydrogen source in connection with fuel cells is an argument of particular interest, since high temperature gasification processes are actually utilized. Solid Oxide Fuel Cells (SOFC), working at high temperatures, have become therefore an interesting candidate to realize the internal reforming of the feed gas from a gasifier. The reforming reaction occurs at the anode of the SOFC, upstream and separated from the fuel cell reaction. The section of the anode where reforming occurs is adjacent to the section where electrochemical reaction occurs. So, heat produced by the electrochemical reaction can be transferred internally with minimal losses. Simulation models of the performance of SOFC stacks and biomass gasifiers are useful to visualize temperature, current and concentration distributions, which are difficult to measure by experimental techniques, allowing the definition of optimal choices in terms of geometries and operating conditions. In this work, an analysis of a SOFC coupled with a biomass gasifier is performed. The objective of this study is the identification of the main effects of the operating conditions on the fuel cell performance in terms of efficiency, and the distribution of the main electro-thermal-fluid-dynamics variables, namely current and temperature. A gasifier model has been implemented to calculate the equilibrium compositions using the Gibbs free energy minimization method. The obtained results are directly used to estimate the inlet gas composition for the SOFC. The SOFC has been modelled by a 3D approach (FLUENT), which solves the energy and mass transport and the internal reforming, coupled with a 0D electrolyte model which, starting from the local information in terms of gas composition, temperature and pressure, is able to predict the fuel cell performance in terms of electrical response and mass-energy fluxes. The whole model has been applied to the analysis of an integrated SOFC-gasifier system to address a planar SOFC response by varying the gasifier operating conditions and the global system performance.

A multibody dynamic model for predicting operational load spectra of dual clutch transmissions

2021 ◽  
Vol 263 (2) ◽  
pp. 4132-4143
Author(s):  
Murat Inalpolat ◽  
Enes Timur Ozdemir ◽  
Bahadir Sarikaya ◽  
Hyun Ku Lee
Keyword(s):  
Steady State ◽  
Dynamic Model ◽  
Forced Vibration ◽  
Linear Time ◽  
Vibration Response ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Time Step ◽  
Gear Mesh ◽  
Multibody Dynamic

In this paper, a generalized nonlinear time-varying multibody dynamic model of dual clutch transmissions (DCT) is presented. The model consists of clutches, shafts, gears and synchronizers, and can be used to model any DCT architecture. A nonlinear clutch model is used to determine the transmitted power to the transmission at any speed and clutch temperature. The clutch can be a single- or multi-plate clutch and can operate in a wet or dry-clutch configuration. A combined kinematic and powerflow simulation enables calculation of gear, shaft, bearing and clutch quasi-static loads as well as gear mesh frequencies following a duty cycle as the input. For the corresponding Linear-Time-Invariant (LTI) system model, natural frequencies and mode shapes are obtained by solving the eigenvalue problem. The modal summation technique is used to determine the steady state forced vibration response of the system. For the corresponding NTV system, Newmark's time-step marching based integration is used to determine both the steady state and transient forced vibration response of the system. The DCT model is exercised using a common transmission architecture operating at several different operating conditions. The resulting impact of changing operational conditions on gear and bearing loads as well as dynamic transmission error spectra are demonstrated.

Intermediate temperature solid oxide fuel cell under internal reforming: Critical operating conditions, associated problems and their impact on the performance

2019 ◽  
Vol 235 ◽  
pp. 625-640 ◽  
Author(s):  
Dulce María Silva-Mosqueda ◽  
Francisco Elizalde-Blancas ◽  
Davide Pumiglia ◽  
Francesca Santoni ◽  
Carlos Boigues-Muñoz ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Intermediate Temperature ◽  
Oxide Fuel ◽  
Internal Reforming
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