Augmentation of heat transfer by deflectors on circulating fluidized bed membrane walls

Golriz, Mohammad R.; Grace, John R.

doi:10.1016/s0017-9310(01)00218-6

Cited by 11 publications

(3 citation statements)

References 17 publications

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“…Their model can select the additives for particular working fluid. Golriz and Grace [90] experimentally show that the addition of an angled deflector to the fin region of circular membrane waterwall heat exchanger surfaces in circulating fluidized beds can lead to a significant increase in the local heat transfer. Karwa et al [91] studied experimentally the flow of air in rectangular ducts of various aspect ratios with repeated transverse rib roughness.…”

Section: Other Techniquesmentioning

confidence: 99%

Review of passive heat transfer augmentation techniques

Dewan

Mahanta

Raju

et al. 2004

Proceedings of the Institution of Mechanical Engineers, Part A:

325

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Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition (both flow and heat transfer conditions). In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. The present paper is a review on progress with the passive augmentation techniques in the recent past and will be useful to designers implementing passive augmentation techniques in heat exchange. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, emphasis is given to works dealing with twisted tapes and wire coils because, according to recent studies, these are known to be economic heat transfer augmentation tools. The former insert is found to be suitable in a laminar flow regime and the latter is suitable for turbulent flow. The thermohydraulic behaviour of an insert mainly depends on the flow conditions (laminar or turbulent) apart from the insert configurations. The present review is organized in five different sections: twisted tape in laminar flow; twisted tape in turbulent flow; wire coil in laminar flow; wire coil in turbulent flow; other inserts such as ribs, fins, dimples, etc.

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Section: Other Techniquesmentioning

confidence: 99%

Review of passive heat transfer augmentation techniques

Dewan

Mahanta

Raju

et al. 2004

Proceedings of the Institution of Mechanical Engineers, Part A:

325

View full text Add to dashboard Cite

show abstract

“…Each structural element in particular the feed supplying device to the reactor contributes to the apparatus efficiency. Changes in the character of the movement and concentration of particles along the wall with deflectors are shown in [6]. In works [7,8] by numerical simulation the effect of ring baffles located on the walls of the cylindrical apparatus on the hydrodynamics of the fluidized bed was analyzed.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Heat and Mass Transfer Processes in Large-Scale Fluidized Bed Complex Structure Apparatus as an Example of the Reactor of Isoparaffins Dehydrogenation

Соловьев¹,

Egorova²,

Ламберов³

et al. 2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

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In the chemical industry are widely used fluidized bed apparatus. The advantage of them is the high speed of heat and mass transfer between components of the reaction, which are in different aggregation states. Studies of large-scale apparatus are hindered big sizes and plurality of structural elements. Often such apparatus operate at high temperatures (500-900 C), which further complicates the study. In this paper we consider a fluidized bed reactor block intended for the dehydrogenation of isobutane. In numerical simulation of fluidization was extended Eulerian-Eulerian approach. Differential equations that describe the hydrodynamic and thermal processes in the field of computational model of the reactor were solved in ANSYS Fluent CFD for axisymmetric unsteady flow scheme. At full simulation of the unit of the reactor in differential equations for the mass fraction of components of the gas mixture is necessary to consider changes related with chemical reactions. In the model used for this purpose it is necessary to add terms to the equations of mass transfer and absorption of heat depending primarily on the gas temperature and catalyst concentration. In this paper we'll restrict considering the minimum number of components of the reaction (raw materials-isobutane, product-isobutylene). For a given chemical reaction is written User Defined Functions (UDF). The influence of the ambient gas, the catalyst and the time step on the progress of chemical reaction in the volume element is studied. Numerical calculations were carried out, due to them circulating streams in the apparatus, the temperature field distribution of the catalyst and the conversion of the feeding gas-raw were analyzed.

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“…The clusters do not usually remain attached close to the wall through the entire height of the riser. After falling 1-3 m [28,29], they either lose their identity due to shear force of the gas or the impact of other particles, and they may also simply detach themselves from the wall and enter the core region again. Dense clusters functions as a thicker radiation shield, and a high fraction of wall coverage by clusters can therefore decrease the radiation flux.…”

Section: Introductionmentioning

confidence: 99%