Rolling Bed Research Articles

A novel microwave pretreated hot air drying (PMt-HD) process for improving drying efficiency and drying quality of Z. bungeanum

The traditional drying method of Fresh Z. bungeanum has the problems of long drying time and serious loss of nutrients, which seriously restricts its efficient and high-value utilization. This study utilized a self-developed penetrating microwave infrared hot air rolling bed dryer (PMIHRBD) to optimize the drying process and compare microwave hot air drying, microwave pretreated hot-air drying (PMt-HD), and freeze drying with hot air drying (HD). The results showed that the drying time of PM10-HD was 48% shorter than that of HD, and the contents of TFC, TPC and TAC were increased by 17.6%, 23.7% and 20.7%, the yield of essential oil was increased by 59.6%, and the antioxidant activity was significantly enhanced. According to the identification of VOCs, hydrocarbons, esters and alcohols played a major role in the formation of Z. bungeanum odor, and HD samples had similar characteristics to PM10-HD samples. For flavor, PM10-HD showed a higher five-flavor richness than other drying processes. In summary, PM10-HD provided a fast and efficient drying process for harvesting high quality Z. bungeanum.

CFD design and testing of an air flow distribution device for microwave infrared hot-air rolling-bed dryer

In this study, a new microwave infrared hot air rolling bed dryer (MIHRBD) was developed and computational fluid dynamics (CFD) techniques were introduced into the design process of the integrated drying system. The structure of the air distribution device was optimised to improve the airflow uniformity over the curved surface of the rolling bed in the microwave-hot air drying combined equipment. The research findings reveal that, across eleven models, the outlet airflow velocity stabilises once the number of mesh elements reaches 5 million, achieving significant computational accuracy at that point. Optimizing components like the uniform air distribution pipe, turbulence plates, and wind deflectors significantly enhanced airflow distribution uniformity by 52.1%. The best airflow and temperature distribution uniformity on the rolling bed surface was achieved when the inlet airflow velocity ranged from 1 to 3 m s−1, with minimum Vd, Uv and temperature non-uniformity coefficients of 0.007 m s−1, 7.2% and 0.2%, respectively. Validation tests on the MIHRBD pilot equipment showed that after optimizing the uniform air distribution device, the minimum temperature difference on the pleurotus eryngii surface was 3.1 °C. This confirmed the feasibility of the computational fluid dynamics method. Introducing hot air significantly enhanced pleurotus eryngii's drying uniformity, with the Page model effectively predicting the MIHRBD drying process. This study provides technical support for future developments in this field of equipment manufacturing and drying process analysis.

Hydrodynamic Insights on Floating Bubbling Fluidized Beds: Dynamic Solutions for Mitigating Gas Maldistribution

This study examined bubbling fluidized beds as an alternative to fixed-bed dry scrubbers on ships for reducing pollutants from marine fuels. It focused on overcoming the challenges of gas maldistribution/slug formation, especially under rough sea conditions. This research departed from traditional methods by introducing mobile internal elements into the bed emulsion phase and investigating their effectiveness in various settings, such as vertical, inclined, and rolling beds. A specialized hexapod-driven bubbling fluidized bed was developed to mimic marine operating conditions and to study the behavior of shipboard fluidized beds. Techniques such as digital image analysis (DIA) and particle image velocimetry (PIV) were used to observe bubble dynamics and granular phases, measuring local void fractions and particle velocities. A key finding is the effectiveness of moving internals in preventing bubble coalescence, which is critical for avoiding wall slugs, at different inclinations. Three types of packing were used as mobile internals: Super Raschig, Pall, and square rings. Super Raschig rings, which are characterized by high porosity, were the most efficient in reducing bubble coalescence, making them a preferred choice for offshore fluidized bed applications. This research contributes to the advancement of fluidized bed technology in marine applications and provides insight for future improvements.

Effects of osmotic dehydration pretreatment on the drying and characteristics of pineapple slices after microwave hot air rolling bed drying

Abstract This study aimed to investigate the effects of osmotic dehydration (OD) pretreatment on the drying and quality of pineapple slices dehydrated using microwave hot air rolling bed drying method. The result suggested the OD pretreatment significantly reduced the moisture content of the food material before drying. It also slightly increased the moisture ratio decreasing rate in the early stage of drying based on the formation of microchannels during the pretreatment. The pretreatment also increased overall temperature and facilitated the transition of free water to bounded water during drying. Based on the pretreatment, the undesired browning of pineapple slices during drying was significantly inhibited. However, the OD pretreatment with 60 % (w/v) sucrose solution caused significant dehydration of the sample before drying, finally resulting in more dramatic browning. Compared with the sample without OD pretreatment, the dried pretreated pineapple slices exhibited an increased amount of collapsed cell structures and pores, due to the cell deformation and water diffusion during the pretreatment. These microstructure changes finally contributed to their increased hardness, springiness and chewiness. Although the pretreatment caused a slightly higher ascorbic acid loss in the final dried food materials, the product with an improved sugar-to-acid ratio was prepared, indicating its improved acceptability. Considering the overall characteristics profile of the dried pineapple slices, the OD pretreatment using 50 % sucrose solution for 24 h was the optimum condition to develop promising dried pineapple slices products.

Solids Mixing in Marinized Bubbling Fluidized Beds: Gas Distribution Study

Marinized bubbling fluidized beds hold promise for reducing CO2, NOX, and SOX in ship exhaust gases, but their use at sea is hampered by a limited understanding of the influence of sea waves on hydrodynamics, heat transfer, and efficiency. To address this gap, this study used direct visualization techniques to investigate the solids mixing and hydrodynamics of bubbling fluidized beds under different gas distribution patterns in pseudo-2D vertical, inclined, and rolling beds. Digital Image Analysis (DIA) was used to determine the Lacey mixing index and the local void fraction, while Particle Image Velocimetry (PIV) was used to capture the particle velocity fields. Additionally, the effects of tilt angles and oscillation parameters of the nonvertical beds were compared with the conventional straight bubbling fluidized bed unit. The uniform inlet distribution of the fluidizing agent was compared with a variety of convex feed distributions at the bed entrance to correct for the negative effects of static/dynamic deviations from bed verticality necessary for optimal operation of bubbling fluidized bed reactors in marine environments.

Numerical simulations of the spread of point‐source liquid spills in inclined and rolling rectangular packed beds

AbstractLiquid spreading in thin rectangular vertical/inclined and oscillating porous media was simulated using a two‐fluid dynamic model as a preliminary step in the design of fixed‐bed reactors dedicated to marine applications. The model assessed the influence of capillary pressure and mechanical dispersion forces arising from the spatial inhomogeneity of point‐source liquid injections in packed beds with different particle sizes, liquid and gas flow rates, liquid viscosity, static bed tilts, and rolling amplitudes and periods. In mildly static inclined beds, the lateral gravity force component and the capillary pressure force were the main factors affecting the liquid spreading. However, at considerable bed inclinations, the liquid phase accumulation in the lowermost regions of the packed bed tended to shrink the liquid spreading. Dynamic oscillatory evolutions of the liquid spills in the rolling bed enlarged the liquid spreading length as compared to the static vertical bed due to combined lateral liquid flow and increased liquid residence time.

Dynamic analysis of moisture, dielectric property and microstructure of ginger slices during microwave hot-air flow rolling drying

This study investigates the drying process of ginger slices using the microwave hot air rolling bed drying (MHARD) method, in terms of measuring drying kinetic change, moisture state and migration, dielectric characteristics, and color changes. The low-field nuclear magnetic resonance (LF-NMR) signal of free, immobilized, and bound water analysis indicates that during the drying of the sample, the drying rate followed a typical “rapid rise-steady-decline” trend in the “preliminary-constant rate-falling rate” stages, respectively. The LF-NMR result shows the content of free water ( A 23 ) in the ginger slices decreased gradually during the drying. Meanwhile, bound water ( A 21 ) content and immobilized water ( A 22 ) content firstly increased and subsequently decreased, because of the microwave and hot air, the movement of water molecules accelerated and the binding force weakened, and then bound water ( A 21 ) and immobilized water ( A 22 ) decreased. On the other hand, both dielectric constant ( ε ′ ) and loss factor ( ε ″ ) of the sample decreased gradually with the decrease in moisture content and logarithmic models were established to describe this correlation. In the preliminary drying stage, although increased microwave power led to a higher drying rate, it resulted in significant damage to the microstructure and compromised the color profile of the final dehydrated ginger slices. This research aims to discuss the mechanism of ginger slides dehydration using the MHARD technique to produce a final product with high quality. • Microwave hot air rolling drying (MHARD) can improve ginger drying uniformity. • Microwave and hot air can accelerate drying rate and optimize the drying process. • Microstructure and color can be damaged by microwave power and hot air temperature. • Inner moisture migrated outwards and gradually distributed evenly during MHARD. • Dielectric properties are affected by moisture content, especially free water.

An experimental study on the startup velocity and motion characteristics of sand beds in air–water pipelines

AbstractSand deposition in the wellbore is one of the most common problems in oil–gas and hydrate exploitation work. A detailed understanding of the migration characteristics of the sand bed and accurate prediction of the starting velocity of the sand bed are key aspects of effective sand carrying. Therefore, this study conducted a large‐scale outdoor gas–water–sand three‐phase flow experiment. The effects of critical factors such as flow pattern, sand size, sand bed height, and pipe inclination angle on sand bed startup velocity and migration were studied experimentally. The experimental results indicated that during the startup process of the sand bed, sand particles exhibited three states: rolling, jumping, and suspension. During the experiment, the sand bed morphology included a static bed, rolling bed, jumping bed, and suspension bed. Compared to a stratified flow, intermittent flow and agitated flow were more beneficial for the startup velocity of sand beds. An increase in pipe inclination also reduced the starting velocity of the sand bed. With an increase in sand size, the startup velocity of the sand bed increased correspondingly. However, there was no significant influence on the migration morphology of the sand bed. Additionally, the greater the thickness of the sand bed, the lower the starting velocity of the sand bed. Based on the stress states of sand grains, in combination with experimental data, this study used least‐squares estimation to establish a prediction model for the startup velocity of sand beds. The model prediction results were in good agreement with the experimental data. This study will provide a basis for predicting the startup velocity of sand beds during the gas–liquid two‐phase sand‐carrying process.

Tracer dispersion in trickle beds under tilts and roll motions – CFD study and experimental validation

A wire-mesh sensor was used to measure the liquid residence time distribution (RTD) and tracer dispersion in trickle beds subjected to stationary tilts and roll motions. The measured tracer characteristics were confronted to three-dimensional transient Euler-Euler CFD simulations to expose the role of inclined and oscillating porous media. The simulation results satisfactorily reproduced the widening tracer signals with increased bed inclination reflecting in asymmetric RTDs prompted by permanent gravity-driven stratified flow zone through the packing. Similarly, tracer dispersion was predicted to increase for rolling beds by increasing tilt angle and motion period. While an increase of tilt angle shortened RTD breakthrough time due to the faster tracer stream evolving in the liquid-rich lower-most zones, tracer elution tended to slow-down with increasing the rolling period. In addition, it was revealed that with altering the column angular position during roll motions the fluid flow structures inevitably varied inside the packing leading to different mixing behaviors and residence time distributions.

Drying characteristics and water dynamics during microwave hot-air flow rolling drying of Pleurotus eryngii

The aim of this study was to improve the drying uniformity and quality of Pleurotus eryngii by using the combination of microwave drying and hot-air flow rolling drying. The moisture content, drying uniformity, and water migration of P. eryngii during microwave hot-air flow rolling drying (MARD) were analyzed in detail. The temperature distribution images were obtained via infrared thermal imaging techniques and the relationship between relaxation time and signal amplitude were obtained via low-field nuclear magnetic resonance analysis and imaging (LF-NMR/MRI). The curves of signal amplitude with moisture content changes were fitted by a linear model with good linearity correlation. It was found that the hot-air and rolling bed could improve the drying uniformity of microwave drying. And the free water was found to transform into immobilized water and bound water during the drying process. Only a small amount of water was left in the dried P. eryngii in the final stage. The results could provide supportive information for improving the uniformity and quality of the drying processes of the edible fungi.

Evaluation of combined screening and drying steps for the improvement of the fuel quality of forest residue wood chips—results from six case studies

Wood chip quality is essential for failure-free and low-emission combustion in automatically stoked small-scale biomass boilers (< 100 kW). Screening and drying of wood chips might be suitable to reduce fuel heterogeneity and to guarantee defined qualities according to ISO 17225-4. Six case studies on screening and drying of forest residue wood chips were performed at German biomass terminals. Screening was done using drum, star, or jigger screens. Drying was done in storage piles and in rolling bed, walking floor, belt, and batch container dryer. Throughput rate was assessed on-site. Fuel properties were analyzed according to international standards. Moisture content of fresh wood chips was too high for small-scale biomass boilers (up to 51 w-%). Raw materials did not comply with specifications of ISO 17225-4 (i.e., ash content, particle size) while fuel indices (Fe/Mn, Al/200) implied contamination with soil material. Technical drying provided moisture contents ≤ 15 w-% while natural drying in piles resulted in values often exceeding 35 w-%. Screening reduced ash content, fines, oversized particles, and the share of N, S, Cl, K, and Si. Screening of pre-dried fuels seems to be beneficial compared to screening of fresh wood chips. After processing, chips could usually be classified as specification A2 to B1 according to ISO 17225-4.

Noise in the recovery area of a large hospital

A noise study was made in a very large government hospital which includes eight surgery rooms and a very large recovery area where patients are placed from as little as half an hour, either before or after a surgery, to about ten hours after some given surgery. In this area, physicians, nurses and bed moving personnel activity is almost continuous, and it has plenty of “Life Equipment” monitoring each and every patient. The noise measurements were concentrated in the recovery area, which is a very large room with very hard boundaries, that includes over 25 beds and aisle areas with no more than curtains separating them in order to allow for easy movement of rolling beds in and out from the surgery area and to the different specialty floors of the hospital. Results of these measurements are presented and commented.

Mixing large and small particles in a pilot scale rotary kiln

The mixing of solid alternative fuel particles in cement raw materials was studied experimentally by visual observation in a pilot scale rotary kiln. Fuel particles were placed on top of the raw material bed prior to the experiment. The percentage of particles visible above the bed as a function of time was evaluated with the bed predominantly in the rolling bed mode. Experiments were conducted to investigate the effects of fuel particle size and shape, fuel particle density, rotary kiln fill degree and rotational speed. Large fuel particles and low-density fuel particles appeared more on top of the bed than smaller particles and high-density fuel particles. Fuel particle dimensions and sphericity were important parameters for the percentage of visible particles. Increasing bed fill degree and/or increasing rotational speed decreased the percentage of particles visible on top of the bed. Results can be up-scaled to industrial conditions in cement rotary kilns and show that even relatively large fuel particles will predominantly be covered by raw material after less than 30 s in the rotary kiln. This affects the heating and combustion mechanisms for the fuel particles.

It's All About Healing

Imagine walking into a hospital to the sound of soft music, seeing beautiful images on the wall, looking out of the window into a lovely garden, reading about an artist in residence who is a painter or a violinist, glancing up to see a kinetic installation swaying gently. Now imagine that space slowly fi lling up with beeping monitors, wheelchairs, rolling beds, portable IVs, and people-busy nurses, doctors, worried family members, and patients, so many patients. Imagine yourself as one of these patients-the pain, the stress, the anxiety. And then imagine yourself focusing on that one image, that one note, that one view, those few words, that one thought that you can hold onto and tune everything else out. Th at is art.Th e power of art to heal is not a new idea. Every culture has a history of the arts and a belief that they lift the spirits. It is also an ancient belief across cultures that the mind and the body are connected, and so what lifts the spirits can arguably heal the body. Th is belief has been put to the test in healthcare today. Art therapy is an established alternative therapy based in the therapeutic impact of creating art. Drama, music, and dance movement therapy are also recognized as treatment forms with compelling support in the medical literature. On the heels of art therapy, which requires a trained art therapist, are other art initiatives where an artist might share his or her art or facilitate patient participation in the arts to improve patient mood and perceptions. Artist-in-residence programs are common in hospitals and involve the community, patients, and staff to make living in the hospital, or living with an illness, more bearable.Unfortunately, an artist or an art therapist can spend only a few hours with a patient (or a stressed family member or staff ). Although the impact of an art intervention can be powerful during this time and have a lingering eff ect afterward, there remains a large body of time that patients and care providers are left to their own means, and their only companion is their environment. Th e art that becomes part of this environment-regardless of the modality-can off er an opportunity to escape from the circumstances of hospitalization (via distraction), as well as to cope with it (via immersion).Th ere is no dearth of distractions in the healthcare environment: televisions, magazines, Internet kiosks, the incessant intercom, a constant stream of patients and staff . But only a few of these are positive distractions, which can take a person's mind away from stress, anxiety, and pain, however briefl y. Th ere is some compelling literature on the impact of positive distractions on short-term stress and pain perception (also discussed in one of the articles in this issue). Interestingly, despite a growing literature on its detrimental eff ects, the television remains popular in health environments. Perhaps this is because it is associated with the one remote that patients control in the hospital.In an age of connectivity, with a growing number of distractions available, we also have to ask the question, is a deluge of distractions really appropriate in healthcare environments? Being in a hospital should arguably be a time of peace, of refl ection, because every person in the hospital (patients as well as staff ) needs to garner the emotional resources to tackle tough times. Perhaps this is where art and carefully selected positive distractions can play a role. Th ey can help create environments that are experiential and immersive, which can go beyond mindless distractions to creating mindful, intentional, and experiences. Unfortunately, the moment we use the term art we meet a hurdle early on; there is no real consensus on what constitutes what is art, and whether good art is really healing art.So let's leave the discussion about labels aside. Let's keep it simple and say that any element of the environment that appeals to one or more of the senses and provides a portal for a person to escape into or draw strength from during a stressful condition falls under the umbrella of art and positive distractions. …

Gas flow in rotary kilns

This paper describes an experimental investigation on the flow characteristics within a rotating cylinder containing a rolling bed of sand. The axis of the cylinder was horizontal and there was no axial bulk flow of particles. The velocity field of the gas flowing through the cylinder was measured by hot-wire anemometry. The measurements indicate that the velocity field is asymmetric with respect to a diameter perpendicular to the granular bed. CFD calculations confirm this finding. The gas velocity profiles are crucial in determining heat transfer from gas to solid.

Predicting the fraction of the mixing zone of a rolling bed in rotary kilns

Abstract The thermal efficiency of a rotary kiln is predominantly influenced by the amount of lateral mixing of the material bed. In this paper, the fraction of the mixing zone in the material bed is predicted for the rolling motion. For a given material, the fraction is found to depend only on three dimensionless variables—the ratio of the particle diameter to the kiln diameter, the Froude number and the filling degree. Experiments were carried out on a rotating cylinder with beans as testing material. The predicted results are in good agreement with the measurements with a maximal error of 12%. The fraction of the mixing zone is then analyzed for industrial rotary kilns. Its value is found to increase approximately linearly with increasing Froude number and the dynamic angle of repose of the material. For all investigated cases, the fraction of the mixing zone lies in the range of 20–45%. Results of this study can provide orientating values of the mixing zone fraction, which are needed to calculate the thermal efficiency of the rotary kiln.

Analytical solution for the rolling-mode granular motion in rotary kilns

An analytical expression is derived to calculate the profile of the active layer thickness of a rolling granular bed in rotary kilns. It is based on the previous numerical model described in AIChE Journal [J. Mellmann, E. Specht, X.Y. Liu, Prediction of rolling bed motion in rotating cylinders, AIChE J. 50 (11) (2004) 2783–2793]. With the analytical expression, the maximal thickness and the mass flow in the active layer can be calculated conveniently in dependence on the rotation speed, the filling degree, the kiln diameter and the material properties. The influence of the material can be described only by the particle diameter and the dynamic angle of repose. No fitting parameter is necessary. It is shown that the deviation of the analytical from the numerical results is negligibly small under practical operating conditions. With the analytical model, measured results from own experiments can be predicted well, and measurements given in the literature can be now compared with one another. Results of this work are of direct utility for engineering design of large-scale technical rotary kilns.

Prediction of rolling bed motion in rotating cylinders

AbstractA mathematical model for the range of rolling bed motion has been developed to calculate the transverse solids motion in rotating cylinders. It is based on mass and momentum balances with physically specified and hence known initial conditions. The behavior of the bed material need only be described by two measurable parameters, the dynamic angle of repose and the angle of slope at the start of the boundary line (interface between the cascading layer and the plug flow region). The shape of the boundary line, the thickness of the cascading layer, the mass flow rate, and the velocity at the surface can be predicted as a function of rotation speed, filling degree, and cylinder diameter. No fitting parameter is needed for the calculation. To verify the model, experiments were carried out for many bed materials and rotating cylinder conditions. A correlation for the angle of slope at the start of the boundary line is given. The calculated results of the model are then compared to our own measurements and those reported in the literature. It is shown that the model agrees relatively well with the experiments. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2783–2793, 2004

Granular motion in rotating drums: bed turnover time and slumping–rolling transition

Theoretical models are presented for calculation of the bed turnover time in both the slumping and rolling modes and the slumping-to-rolling transition in rotating drums with less than 50% volumetric fill of free-flowing granular materials. It is suggested that the transition from slumping to rolling occurs when the two turnover times are equal. The model for the bed turnover time in rolling beds is compared with the data reported in the literature. Very good agreement has been obtained. The bed turnover time is also employed to define a new Froude number for constructing the bed behaviour diagram. It is shown that the bed behaviour diagram based on the new Froude number brings the data points for sand and limestone into single curves. The implications of the bed turnover time for solid mixing and heat transfer within particle beds are also discussed.

Experimental Investigation of Natural Convection in a Core of a Marine Reactor in Rolling Motion

A series of single-phase natural circulation experiments in a simulated marine reactor mounted on a rolling bed was performed and the average Nusselt number in the core was evaluated in order to investigate effects of the rolling motion on the heat transfer in the core. Heat transfer with an upright attitude is well correlated with the Rayleigh number and is slightly lower than El-Genk's correlation. Heat transfer in the core is not affected by the inclination angle because the inclination of the present experiment is not large enough to cause any remarkable changes in the flow pattern of the core. Heat transfer in the core is enhanced by the rolling motion which is thought to cause internal flow in the core. Heat transfer during the rolling motion is correlated with the Richardson number for rolling motion, R iR , and is classified into three regimes: (1) region A (0.05<R iR ≤0.3) where heat transfer is dominated by the inertial force due to the rolling motion; (2) region B (0.3<R iR ≤2) where heat transfer is affected by the combined effect of the inertial force and natural convection; and (3) region C (R iR >2) where heat transfer is affected only by the natural convection.