Heat transfer in gas fluidized beds part 2. Dependence of heat transfer on gas velocity

Molerus, O.

doi:10.1016/0032-5910(92)85049-2

Cited by 19 publications

(6 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In each case, as with the earlier simulation with a particle size of 500 μm, an inlet gas velocity that was twice the minimum fluidization velocity of the bed was applied to induce bubbling fluidization. Based on the studies of Molerus, , the hydrodynamic contribution to heat transfer rates in bubbling fluidized beds was predominantly the excess gas velocity. In this part of the current study, this hydrodynamic contribution was deemed to be maintained constant via a fixed ratio of inlet gas velocity to minimum fluidization velocity so as to investigate the effect of a material property, particle size, on heat transfer behaviors.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Molerus defined a two-phase Prandtl number for prediction of maximum heat transfer coefficients in bubbling fluidized beds which takes into consideration the thermal and hydrodynamic properties of particles and fluid. He subsequently developed six correlations for calculating maximum heat transfer rate based on excess gas velocity . The hydrodynamics of bubbling fluidized beds has been investigated using the Eulerian–Eulerian approach, providing predictions on instantaneous solid volume fraction as well as particle velocity profiles.…”

Section: Introductionmentioning

confidence: 99%

“…He subsequently developed six correlations for calculating maximum heat transfer rate based on excess gas velocity. 2 The hydrodynamics of bubbling fluidized beds has been investigated using the Eulerian−Eulerian approach, providing predictions on instantaneous solid volume fraction as well as particle velocity profiles. Schmidt and Renz 3 applied the Eulerian approach for numerical simulations of two-phase flow in a fluidized bed with an immersed tube.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Heat Transfer from an Immersed Tube in a Bubbling Fluidized Bed

Hau

Lim

2016

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

An Eulerian−Eulerian approach was used to investigate the effects of particle size and immersed tube temperature on bubbling and heat transfer behaviors in a gas fluidized bed. Large gas bubbles were observed to split into smaller bubbles that flowed around the immersed tube during the fluidization process. The formation of pockets of gas around the immersed tube led to a lower heat transfer coefficient. Heat transfer between the immersed tube and particles was facilitated by a phenomenon of particle renewal. Larger gas bubbles formed in the gas fluidized bed containing larger particles and this resulted in lower heat transfer coefficients due to the formation of more gas pockets around the immersed tube. When the temperature of the immersed tube was increased, the sensitivity of the heat transfer process toward formation of gas pockets around the immersed tube was observed to increase.

show abstract

Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Heat Transfer from an Immersed Tube in a Bubbling Fluidized Bed

Hau

Lim

2016

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

show abstract

“…This analysis is based on the two-phase theory of fluidization, with the emulsion phase at minimum fluidization conditions . Other empirical equations, such as the one introduced by Zabrodsky, are helpful for practical purposes, given that it yields an upper value for the heat-transfer coefficient and has been cited as the one giving the best predictions. , Another alternative equation to evaluate the regenerator-side film transfer coefficient is the one proposed by Gelperin and Einstein . This equation is reported as being valuable, for bundles of spaced vertical tubes, immersed in a fluidized bed.…”

Section: Modeling Heat-transfer Phenomena: Regenerator Sidementioning

confidence: 99%

Heat-Transfer Prediction in the Riser of a Novel Fluidized Catalytic Cracking Unit

Blasetti

Lasa

2001

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

The present study considers a "Multicrackex" unit constituted by a riser reactor with an upflow catalyst suspension exchanging heat with a surrounding fluidized-bed regenerator. A statisticalbased analysis is developed to establish a semiempirical correlation able to describe the heat transport phenomena between a bundle of riser reactor tubes and a fluidized-bed regenerator. The proposed correlation is tested and developed under reaction and realistic conditions for fluidized catalytic cracking (FCC) units, and this adds special value to the study developed. In this respect, the present study provides data that may be of particular interest for the design of novel FCC processes.

show abstract

“…They also pointed out that mechanistic models are no better than the hydrodynamic models on which they are based [ 7 , 16 ]. Molerus developed predictive equations for heat transfer in fluidized beds [ 24 , 25 , 26 ]. The applied dimensional analysis to identify seven relevant groups was based on the physical properties of the solids and gas.…”

Section: Introductionmentioning

confidence: 99%

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

Krzywański

2019

Entropy

View full text Add to dashboard Cite

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.

show abstract

Heat transfer in gas fluidized beds part 2. Dependence of heat transfer on gas velocity

Cited by 19 publications

References 2 publications

Heat Transfer from an Immersed Tube in a Bubbling Fluidized Bed

Heat Transfer from an Immersed Tube in a Bubbling Fluidized Bed

Heat-Transfer Prediction in the Riser of a Novel Fluidized Catalytic Cracking Unit

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

Contact Info

Product

Resources

About