To address the effect of a ship’s rolling on the fluidization quality of fluidized beds, in this study, a simulation of a rolling fluidized bed with longitudinal internal members added (R-FBLIM) was carried out and compared with that of a rolling fluidized bed without internal members added (R-FBWIM). The transient motion, as well as the behavioral characteristics of the bubbles within the R-FBLIM, was analyzed; the variation patterns of the number of bubbles, as well as the equivalent diameter of the bubbles, were compared for different apparent gas velocities, oscillation periods, and amplitudes; and the mechanism of the action of the longitudinal internal members was investigated. The results show that the structural design of the longitudinal internal members can effectively improve the gas–solid fluidization quality of the rolling fluidized bed. The horizontal support plate and the cap hole structure can effectively break the air bubbles, the cap hole structure promotes the radial mixing of the gas–solid fluid, and the internal and outer rings of the curved surface plate roll in rows, which inhibit the aggregation behavior of the gas–solid fluid to the two sides of the oscillating planes, respectively, by cooperating with the cap hole structure. Compared with R-FBWIM, the gas–solid phase within R-FBLIM is more spatially distributed, with the number of bubbles increasing by about 2–4 times and the mean diameter decreasing by about 50–60%. The number of bubbles increases with the gas velocity but decreases with the rolling amplitude; the mean diameter decreases with the gas velocity but responds less to the rolling amplitude change.

In this study, the optimization of a gas–solid fluidized bed structure under oscillating conditions is carried out, and the traditional equal-diameter structure is improved to a variable-diameter structure. In this paper, a 300 mm diameter equal-diameter fluidized bed is taken as the benchmark model, and the research team uses numerical simulation to analyze the changing law of bubble size and the percentage of non-fluidized area. It is found that under the condition of the same gas volume, the “cone-contraction” fluidized bed with variable-diameter structure can reduce the bubble size by about 25% and the percentage of non-fluidized area by about 11%. The effects of the specific operating parameters are as follows: the operation of increasing the gas volume will lead to an increase in bubble size but will lead to a decrease in the percentage of non-fluidized area; the increase in the initial bed height will simultaneously increase the bubble size and the percentage of non-fluidized area; the increase in the amplitude of the oscillation will lead to an increase and then a decrease in the bubble size, and will lead to a continuous expansion of the percentage of non-fluidized area; and the change in the oscillation period will not have a significant effect on the two. A comparison of the experimental data shows that the overall performance of the variable-diameter fluidized bed is better than that of the equal-diameter fluidized bed, as shown in the following: the bubble size is reduced by 24~32%, and the percentage of non-fluidized area is reduced by 6~12%. This study provides an effective direction for the structural optimization of fluidized beds.

In an axial granular bed filter (GBF), a new mesoscale simulation approach is obtained by combining the macroscopic calculation models, i.e., the equations of the total pressure drop and dust-removal efficiency into the porous media model and the source term of the conservation equations. After grid-dependent tests and experimental validation, the effects of different conditions, i.e., granular bed height L, superficial gas velocity u_g, dust diameter d_p, dust concentration c_p, granular diameter d_g, initial bed voidage ε₀, and filtration time t, on the pressure drop and dust-removal efficiency are investigated. The results show that the pressure drop is related to the inertial and viscous resistance terms, which increase with increasing L, u_g, c_p and t and decreasing ε and d_g. The dust-removal efficiency is related to the Reynolds number, effective Stokes number, and equivalent granular diameter ratio. It increases with increasing L, u_g, d_p and t (small values), and decreasing c_p, ε, and d_g. Moreover, the influence of different conditions coincides well with dust-removal efficiency in relevant studies, which further demonstrates the accuracy of the mesoscale simulation approach. With the application of this method, the flow field can also be obtained easily and quickly, which is expected to provide a reference for the simulation study of GBF.

When transplanting the gas–solid fluidized bed technology to the offshore floating platform, the gas–solid flow characteristics in the bed will be affected by the rolling of the platform. In this paper, the flow field, especially the dynamic variation characteristics of the particles, in a two-dimensional rolling fluidized bed, is investigated using the numerical simulation method. The results show that when the bed is in an inclined position, the gas/particle phases gather in the upper/lower wall region of the inclined bed. During the rolling process of the bed, this behavior results in a periodic change in the gas–solid flow state near the wall region, forming an overall particle internal circulation flow mode of ‘upward flow rate in the upper wall region and downward flow rate in the lower wall region’. The solid holdup in the lower wall region fluctuates at a low amplitude around high values, with a corresponding downward solid flow rate. Meanwhile, the upper wall region has a high frequency and amplitude of solid holdup fluctuations and a corresponding upward solid flow rate. In addition, affected by the Coriolis force, a ‘lag phenomenon’ appears when the inclination angle decreases, compared with the instantaneous inclination angle increase stage. It is anticipated that this paper will provide theoretical guidance for the engineering application of the fluidized bed on the offshore floating platform.

The calculation equations of pressure drop and solid flow rate are given in an intermittent countercurrent moving bed with multiple optimized structures. The flow fields are investigated by experimental methods under different conditions, e.g., ratio of position of the gas distributor to the bed width (r_p = 0.5~1.5), gas superficial velocity (u_g = 0~0.1591 m/s), solid outlet diameter (D_o = 5~25 mm) and cone angle (α = 0~60°). It is found that when r_p ≥ 1.0, the flow field in the bed is little affected by r_p. Flow patterns are divided into three modes: continuous discharging, intermittent discharging (synchronous, asynchronous) and particle bridging. During continuous discharging, the calculation formula of the solid flow rate, which is closely related to D_o and gas–solid slip velocity v_slip, is established by referring to the modified De Jong and Beverloo formulas, and its error ≤ ±12.5%. The pressure drop of the total bed consists of the pressure drops of the granular bed and the solid outlets, which are affected by D_o, v_slip and α; it is built by referring to the Ergun formula, and its error ≤ ±17.0%. As the solid flow rate and pressure drop influence each other through v_slip, an iterative algorithm is proposed to enhance the computation accuracy.

To clarify the thermo-hydraulic performance and thermodynamic characteristics of rotational–perforated static mixer (RPSM) for laminar heat transfer enhancement in circular tubes, a three-dimensional steady laminar flow model was developed for inlet Reynolds numbers from 200 to 1000. The heat transfer enhancement, resistance increase, and irreversible losses of RPSM with two installation modes and Kenics were comparatively analyzed. The results show that RPSM (forward) exhibits the strongest practical heat transfer performance. Its convective heat transfer coefficient is on average 39.8% higher than that of Kenics, while its thermal effectiveness and number of transfer units are increased by 21.3% and 32.8%, respectively. However, the heat transfer enhancement of RPSM is accompanied by a significant increase in flow resistance. The Z-factors of RPSM (forward) and RPSM (backward) are approximately 3.4 and 6.2 times that of Kenics, respectively. Second law analysis shows that the Bejan numbers of all configurations are close to unity, indicating that total entropy generation is mainly dominated by heat transfer entropy generation. Although RPSM (forward) has a higher exergy destruction rate, its second law efficiency is on average 20.1% higher than that of Kenics. Flow–heat transfer coupling visualization shows that RPSM (forward) can maintain relatively continuous swirling and secondary flow structures, thereby promoting radial energy transport and temperature field uniformity. In contrast, RPSM (backward) induces stronger local recirculation and pressure loss, resulting in higher pumping power demand. Overall, for the specific RPSM geometry and Reynolds number range investigated in this study, RPSM (forward) shows advantages in heat transfer capacity and thermal exergy utilization, but these advantages are accompanied by a substantial flow resistance penalty. Therefore, further structural optimization should focus on retaining radial transport while reducing local pressure loss.