Heat transfer characteristic in an external heat exchanger with horizontal tube bundle

Błaszczuk, Artur; Jagodzik, Szymon

doi:10.1016/j.ijheatmasstransfer.2019.119253

Cited by 29 publications

(11 citation statements)

References 21 publications

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“…Thus, the packed particles' contact time with the horizontal tubes is dependent on the particle motion adjacent to a submerged horizontal tube bundle, which is resulted from local fluctuations in the gas bubble fraction. To determine the bubble fraction, we can use the following formula [27]:…”

Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%

“…Due to the fact that the horizontal smooth tubes in the top section are operated under splash zone conditions (n splash = 4), from here, the average heat transfer coefficient h top is obtained from the following empirical correlation [15,27,34]:…”

Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%

“…It is assumed that the FBHE system operates under constant pressure during each test, and fluidizing medium (air) is treated as an ideal gas. In order to simplify the complex problem of heat transfer from fluidized beds to immersed horizontal objects, the authors have used the following assumptions: (i) the particle packets and gas phase behave as a continuous flow fluidized bed, (ii) the gas temperature equals the particle packets temperature for a given examined condition since both phases are highly intermixed, (iii) at any given time, the heat transfer surface is covered by emulsion phase (particle packets) or gas bubbles, (iv) particle packets are brought into contact with the immersed horizontal tube surface by the motion of rising gas bubbles in the bed, (v) the gas convection contributes to the process of heat transfer by convective mixing, which augments the heat transfer in the gas gaps between the bed particles and the heat transfer surface and between neighboring particles, (vi) the heat capacity of packets is assumed to be equal to the solid heat capacity [38], (vii) the bubble fraction in the fluidized bed is estimated in agreement with the classical two-phase theory for aggregative fluidization [35,36], (viii) in the emulsion phase, heat transfer is assumed to be composed of particle convection (whose motion is a direct result of gas bubble flow), gas convection due to the interstitial gas velocity and radiation [27] and (ix) the density of an emulsion packet is not taken to be equal to the density of a loosely packed static bed of particles [38].…”

Section: Input Data To Heat Transfer Modelingmentioning

confidence: 99%

“…A detailed description of the procedure employed in making the performance tests, the measurement of process data (i.e., bed temperature, static pressure inside FBHE, steam parameters, gas flow, etc.) and the description of data acquisition systems is given elsewhere [27,[48][49][50] and will not be described again. Relevant physical and thermal properties of the emulsion phase and gas phase used in the present investigation are reported in Table 3.…”

Section: Input Data To Heat Transfer Modelingmentioning

confidence: 99%

“…However, the selected experimental data deal with heat transfer characteristics for large-scale CFB units that are usually presented under different boiler loads only [4,8,12,14,26]. Only a few papers [15,27] discussed the heat transfer between the horizontal tube bundle and the fluidized bed in detail.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

Błaszczuk

Jagodzik

2021

Energies

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In the research work, energy transport between a dense fluidized bed and submerged horizontal tube bundle is analyzed in the commercial external heat exchanger (EHE). In order to investigate the heat transfer behavior, the authors carried out eight performance tests in a fluidized bed heat exchange chamber with a cross-section of 2.7 × 2.3 m in depth and width and a height of 1.3 m. The authors have been developing a mechanistic model for the prediction of the average heat transfer coefficient, which includes the effect of the geometric structure of the tube bundle and the location of the heat transfer surface on the heat transfer rate. The computational results depict that the average heat transfer coefficient is essentially affected by superficial gas velocity and suspension density rather than bed particle size. The empirical correlations have been proposed for predicting heat transfer data since the existing literature data is not sufficient for industrial fluidized bed heat exchangers. On the basis of the evaluated operating conditions of an external heat exchanger, the optimal conditions where heat transfer occurs could be deduced. The developed mechanistic heat transfer model is validated by experimental data under the examined conditions.

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Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%

Section: Formulation Of Mechanistic Heat Transfer Modelmentioning

confidence: 99%