scholarly journals A comparison of fuzzy logic and cluster renewal approaches for heat transfer modeling in a 1296 t/h CFB boiler with low level of flue gas recirculation

2017 ◽  
Vol 38 (1) ◽  
pp. 91-122 ◽  
Author(s):  
Artur Błaszczuk ◽  
Jarosław Krzywański
Keyword(s):  
Heat Transfer ◽  
Fuzzy Logic ◽  
Heat Transfer Coefficient ◽  
Flue Gas ◽  
Cfb Boiler ◽  
Suspension Density ◽  
Heat Transfer Modeling ◽  
Bed Temperature ◽  
Gas Recirculation ◽  
Furnace Height

AbstractThe interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131-1156 K and 1.93-6.32 kg/m3, respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109-241 W/(m2K) and 111-240 W/(m2K), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.

Bed-To-Wall Heat Transfer in a Supercritical Circulating Fluidised Bed Boiler

2014 ◽  
Vol 35 (2) ◽  
pp. 191-204 ◽  
Author(s):  
Artur Błaszczuk ◽  
Wojciech Nowak ◽  
Szymon Jagodzik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pressure Measurements ◽  
Fluidised Bed ◽  
Cfb Boiler ◽  
Suspension Density ◽  
Bed Temperature ◽  
Circulating Fluidised Bed ◽  
The Heat Transfer Coefficient

Abstract The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB) boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR) were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa) in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.

scholarly journals Heat Transfer Performance in a Superheater of an Industrial CFBC Using Fuzzy Logic-Based Methods

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 919 ◽  
Author(s):  
Krzywanski
Keyword(s):  
Heat Transfer ◽  
Fuzzy Logic ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Practical Significance ◽  
Overall Heat Transfer Coefficient ◽  
Bed Temperature ◽  
The Heat Transfer Coefficient

The heat transfer coefficient in the combustion chamber of industrial circulating flidized bed (CFB) boilers depends on many parameters as it is a result of multifactorial mechanisms proceeding in the furnace. Therefore, the development of an effective modeling tool, which allows for predicting the heat transfer coefficient is interesting as well as a timely subject, of high practical significance. The present paper deals with an innovative application of fuzzy logic-based (FL) method for the prediction of a heat transfer coefficient for superheaters of fluidized-bed boilers, especially circulating fluidized-bed combustors (CFBC). The approach deals with the modeling of heat transfer for the Omega Superheater, incorporated into the reaction chamber of an industrial 670 t/h CFBC. The height above the grid, bed temperature and voidage and temperature, gas velocity, and the boiler’s load constitute inputs. The developed Fuzzy Logic Heat (FLHeat) model predicts the local overall heat transfer coefficient of the Omega Superheater. The model is in good agreement with the measured data. The highest overall heat transfer coefficient is equal 220 W/(m2K) and can be achieved by the SH I superheater for the following inputs l = 20 m, tb = 900 °C, v = 0.95, u = 7 m/s, M-C-R = 100%. The proposed technique is an effective strategy and an option for other procedures of heat transfer coefficient evaluation.

scholarly journals Experimental study of the convective heat transfer coefficient in a packed bed at low Reynolds numbers

2014 ◽  
Vol 18 (2) ◽  
pp. 443-450 ◽  
Author(s):  
Souad Messai ◽  
Ganaoui El ◽  
Jalila Sghaier ◽  
Ali Belghith
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Packed Bed ◽  
Bed Temperature ◽  
Proposed Model

An experimental study to evaluate the convective heat transfer coefficient in a cylindrical packed bed of spherical porous alumina particles is investigated. The task consists in proposing a semi-empirical model to avoid excessive instrumentation and time consumption. The measurement of the bed temperature associated to a simple energy balances led to calculate the gas to particle heat transfer coefficient using a logarithmic mean temperature difference method. These experiments were performed at atmospheric pressure. The operating fluid is humid air. The gas velocity and temperature ranged from 1.7-3 m/s and 120-158?C, respectively. The data obtained was compared with the correlations reported in the literature. It is shown that the proposed model is in reasonable agreement with the correlation of Ranz and Marshall. Despite, many researches on experimental investigations of heat transfer coefficient in packed beds at low and average temperature are proposed, few studies presented calculation of convective heat transfer coefficient at high temperature (above 120?C). A possible application of the proposed model is drying and combustion.

Thermodynamic Considerations Regarding the Use of Exhaust Gas Recirculation for Conventional and High Efficiency Engines

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Thermal Efficiency ◽  
High Efficiency ◽  
Convective Heat Transfer Coefficient ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Gas Recirculation

During the last several decades, investigations of the operation of internal combustion engines utilizing exhaust gas recirculation (EGR) have increased. This increased interest has been driven by the advantages of the use of EGR with respect to emissions and, in some cases, thermal efficiency. The current study uses a thermodynamic engine cycle simulation to explore the fundamental reasons for the changes of thermal efficiency as functions of EGR. EGR with various levels of cooling is studied. Both a conventional (throttled) operating condition and a high efficiency (HE) operating condition are examined. With no EGR, the net indicated thermal efficiencies were 32.1% and 44.6% for the conventional and high efficiency engines, respectively. For the conditions examined, the cylinder heat transfer is a function of the gas temperatures and convective heat transfer coefficient. For increasing EGR, the gas temperatures generally decrease due to the lower combustion temperatures. For increasing EGR, however, the convective heat transfer coefficient generally increases due to increasing cylinder pressures and decreasing gas temperatures. Whether the cylinder heat transfer increases or decreases with increasing EGR is the net result of the gas temperature decreases and the heat transfer coefficient increases. For significantly cooled EGR, the efficiency increases partly due to decreases of the heat transfer. On the other hand, for less cooled EGR, the efficiency decreases due at least partly to the increasing heat transfer. Two other considerations to explain the efficiency changes include the changes of the pumping work and the specific heats during combustion.

Impact of the Anticorrosion Films on the Condensing Heat Transfer of Flue Gas in Fin-Tube Heat Exchangers

2010 ◽  
Author(s):  
Sui-lin Wang ◽  
Yuan-yuan Wu ◽  
Shu yuan Pan ◽  
Yong zheng Shi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Organic Compound ◽  
Transfer Coefficient ◽  
Flue Gas ◽  
Heat Exchangers ◽  
Convection Heat Transfer ◽  
Experimental Results ◽  
Convection Heat ◽  
Fin Tube

The forced convective heat transfer with condensing was experimentally investigated when wet flue gas was flowing in the fin-tube heat exchangers with three anticorrosion films respectively, including the nickel-phosphorus amorphous composite eletroless and organic compound (NPACE&OC) surface, the nickel-phosphorus amorphous composite eletroless (NPACE) surface, and the organic compound (OC) surface. The experimental results indicate the convection heat transfer characteristics as following: Among the three heat exchangers, the convection heat transfer for the heat exchanger with NPACE&OC surface is the best, the convection heat transfer coefficient is about 18%∼25% higher than that of the other two heat exchangers. It could be caused by the lower surface energy of the NPACE&OC surface that forms the drop condensate. The experimental results of heat transfer coefficient relative to Reynolds Number and Jakob Number were also presented in this paper. Based on the experimental results and the analysis, the correlation of the measurements was achieved.

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