Conventional Bed Research Articles

On the conformity of floor heating systems with sleeping in the eastern-style beds; physiological responses and thermal comfort assessment

Radiant floor heating systems are usually designed in such a way that the sedentary persons feel thermal neutrality. On the other hand, in most of eastern countries, people traditionally tend to directly sit or sleep on the floor. This could arise some limitations in using of the floor heating systems in the countries with such eastern lifestyle. The main focus of this study is on evaluating the physiological responses and thermal comfort of sleeping persons in an eastern-style bed on a heated floor. For this purpose, thermal sensation of sleeping occupants on the heated floor was compared with that of sleeping persons on the conventional beds. The results reveal that under similar thermal conditions, the thermal sensation and skin wettedness of the sleeping persons are obviously higher on the eastern-style beds than on the conventional beds. Therefore, sleeping in an eastern-style bed causes the person to feel more thermal discomfort and also more unpleasantness due to skin wettedness. Furthermore, the results indicate that to get the same level of thermal and wettedness pleasantness on both aforementioned beds, the thermal insulation value of the blanket must be about 0.4 clo lower in the eastern-style bedding arrangement than in the conventional bed.

Static and Dynamic Performance Improvement of Conventional Computer Numerical Control Machine Tool Bed with Hybrid Welded Steel

Problem statement: The advancements in machine tools to maximize the production by increasing spindle speeds have caused vibration in machine tools. The two functional requirements of machine tool bed for machine tools are high structural stiffness and high damping, which cannot be satisfied simultaneously if conventional metallic materials such as cast iron are employed. Hence there is a need to replace cast iron with alternate materials. Approach: The objective of this study is to improve the stiffness, natural frequency and damping capability of machine tool bed using a composite material containing welded steel and polymer concrete. Welded steel material has high stiffness but low damping and polymer concrete has high damping but low stiffness. So in this study, a machine tool bed made of sandwich structures of welded steel and polymer concrete is designed and manufactured. Modal and static analyses were conducted numerically and experimentally to determine the modal frequencies, damping ratio, deformation and strain. Results: The results at first mode showed that the natural frequency improved by 24.7% and damping ratio was 2.7 times higher than cast iron. The comparison of strain and deformation also showed significant improvement. Conclusion: This study proposed a hybrid welded steel bed as a replacement for cast iron as a machine tool bed material and the results showed that the static and dynamic characteristics were superior to cast iron.

Stability of slot‐rectangular spouted beds: Effect of slot configuration

AbstractExperiments were carried out to determine the flow stability of slot‐rectangular spouted beds of 300 × 100 mm cross‐section with slots of different widths, lengths, and depths. The effects of slot expansion angle and diverging base were also investigated. Dependent variables included the minimum spouting velocity, bed pressure drop and standard deviation of pressure fluctuations. Based on the flow regimes and spout termination mechanisms, instability was found to be mainly due to the interaction of multiple spouts. Criteria were identified relating stable spouting to slot dimensions and particle size. Slots of limited cross‐sectional area can provide sustainable and symmetric spouting with little fluctuation, as long as the slot length‐to‐width ratio and depth are within certain limits, related to those for conventional spouted beds.

Particle–Gas Mass Transfer in a Spouted Bed with Adjustable Air Inlet

Spouted bed equipment has the potential of producing high-quality particulate materials with reduced energy consumption and environment impact. Particle-to-gas mass transfer was investigated in a spouted bed with a novel design of two rotating drums placed symmetrically in the apparatus to create air inlet openings of adjustable width, so that fluidization can be adapted to the requirements of each product and process. The mass transfer coefficients between particle surface and gas were derived from first-period drying experiments with porous, nonhygroscopic material by assuming perfect back-mixing or, alternatively, ideal plug flow of the gas. Respective Sherwood numbers were empirically correlated and found to be superior to the Sherwood numbers of conventional fluidized beds or conventional spouted beds.

An analytical model to predict the thermal performance of a novel parallel flow packed bed solar air heater

A design of a parallel flow solar air heater with packed material in its upper channel and capable of providing a higher heat flux compared to the conventional non-porous bed double flow systems is presented. An analytical model describing the various temperatures and heat transfer characteristics of such a parallel flow packed bed solar air heater (PFPBSAH) has been developed and employed to study the effects of the mass flow rate and varying porosities of the packed material on its thermal performance. The model employs an iterative solution procedure to solve the governing energy balance equations describing the complex heat and mass exchanges involved. To validate the proposed analytical model, comparisons between theoretical and experimental results showed that good agreement is achieved with reasonable accuracy. Also, PFPBSAH is found to perform more efficiently than the conventional non-porous double flow solar air heaters with 10–20% increase in its thermal efficiency. Furthermore, the effect of the fraction of mass flow rate in the upper or lower flow channel of PFPBSAH device on its performance, has also investigated theoretically. The fraction of the mass flow rate in the respective channels of the PFPBSAH is shown to be dominant parameter in determining the effective thermal efficiency of the heater.

Respiration and body movement analysis during sleep in bed using hetero-core fiber optic pressure sensors without constraint to human activity

We describe respiration monitoring in sleep using hetero-core fiber optic pressure sensors. The proposed hetero-core fiber optic sensor is highly sensitive to macrobending as a result of the core diameter difference due to stable single-mode transmission. Pressure sensors based on hetero-core fiber optics were fabricated to have a high sensitivity to small pressure changes resulting from minute body motions, such as respiration, during sleep and large pressure changes, such as those caused by a rollover. The sensors are installed in a conventional bed. The pressure characteristic performance of all the fabricated hetero-core fiber optic pressure sensors is found to show a monotonic response with weight changes. A respiration monitoring test in seven subjects efficiently demonstrates the effective use of eight hetero-core pressure sensors installed in a bed. Additionally, even in the case of different body postures, such as lying on one's side, a slight body movement due to respiration is detected by the hetero-core pressure sensors.

Influence of Oxygen Supply in an Iron Ore Sintering Process

The current issues of sintering technology in the iron and steel making industry are how to increase productivity of sintering process and to maintain proper quality of sintered ore. In the conventional sintering bed, combustion of solid fuel supplies heat required for sintering while it generates imbalance of heat concentration in the bed. The unevenly distributed heat is considered to be problematic on the quality aspect of sintered ore. Therefore, in order to maximize the production rate and quality of the products, an investigation for improved operational mode is indispensable. In this study, the effect of additional oxygen supply with an adjustment of injection location is discussed. Scale downed pot tests in addition to computation by previously developed unsteady 1-dimensional sintering bed model are employed for the examination. Also, quantitative parameters are applied to evaluate the changes of sintering process and the combustion characteristics are systemically analyzed among designed cases. The reactivity of coke combustion tends to increase with the enrichment of oxygen in the induced air. However, the degree of change in the sintering time as well as effective heat supply varies according to the locations of oxygen injection.

Soil management and traffic effects on infiltration of irrigation water applied using sprinklers

Zero tillage and controlled traffic have been proposed as means for more productive and sustainable irrigated farming. Both practices affect soil infiltration characteristics and, therefore, should have effects on sprinkler irrigation performance. This study compared water infiltration and runoff in three sprinkler irrigation tests performed on an alluvial loam soil at different times during a maize (Zea mays L.)–cotton (Gossypium hirstium L.) rotation under two soil managements: permanent beds with crop residue retention (PB: planting beds maintained unaltered from year to year) and conventional beds with residues incorporated with tillage (CB: disc and chisel ploughing followed by rotavator pass and bed forming every year). Traffic was controlled and two types of furrows were distinguished in both tillage systems: with (+T) and without (−T) wheel traffic. The irrigation tests were performed on maize at full cover, on bare soil just before cotton sowing and on cotton with 50% ground cover. Infiltration and runoff were affected notably by both traffic and soil management. The soil under PB infiltrated more water than under CB, and −T furrows more than +T furrows. Considering the combined treatments, −T furrows in the CB system infiltrated more water than +T furrows in the PB system. A sprinkler irrigation model for simulating water application and soil infiltration and runoff was formulated. The model was used to analyse irrigation performance under infiltration characteristic of the CB and PB systems in trafficked and non-trafficked furrows. Five irrigation performance indicators were used to assess the various combinations of tillage and traffic: Wilkox–Swailes coefficient of uniformity; application efficiency; deep percolation ratio; tail water ratio; and adequacy. The model was used to develop operation diagrams and provided guidelines for making irrigation decisions in the new controlled traffic/permanent bed system and in a standard conventional system.

Circulating turbulent fluidization—A new fluidization regime or just a transitional phenomenon

While circulating fluidized bed (CFB) reactor has many advantages over the more conventional turbulent fluidized bed (TFB) reactor, it does at least have one significant shortcoming—the rather dilute solids volume concentration in CFB reactor gives rise to less ideal reaction intensity. On the other hand, while having higher reaction intensity, TFB reactor has one fatal drawback of particle back-mixing, making it not suitable for certain reactions such as catalytic reaction where the catalyst requires frequent regeneration. This paper describes some key issues in the development of a circulating turbulent fluidized bed (CTFB) reactor that combines the advantages of both TFB and CFB, that is, to have the high reaction intensity as in TFB but and also to have a suppressed solids back-mixing as in CFB due to a continuous net upflow of solids flux through the bed. Experimental results show enough evidence to suggest that a new fluidization regime is formed, the characteristics of which appears to be distinct from those observed in a regular TFB and from those in either the bottom or the upper sections of regular CFB and/or high-density CFB (HDCFB). Fundamentally, the difference is that particle–particle interaction (collision) dominates the motion of particles in CTFB and TFB, while gas–particle interaction (drag force) is the key element that determines the two phase flow in CFB including HDCFB.

Mathematical modeling of a biofiltration process in a trickle-bed reactor

A conventional trickle bed reactor and its modified type both packed with Ca/Al composite oxide-based alkaline catalysts were studied for biodiesel production by transesterification of rapeseed oil and methanol. The effects of the methanol usage and oil flow rate on the FAME yield were investigated under the normal pressure and methanol boiling state. The oil flow rate had a significant effect on the FAME yield for the both reactors. The modified trickle bed reactor kept over 94.5% FAME yield under 0.6 mL/min oil flow rate and 91 mL catalyst bed volume, showing a much higher conversion and operational stability than the conventional type. With the modified trickle bed reactor, both transesterification and methanol separation could be performed simultaneously, and glycerin and methyl esters were separated additionally by gravity separation.

Hydrogen recovery from the electrocoagulation treatment of dye-containing wastewater

In this paper, a technique of hydrogen recovery from an electrocoagulation process treating dye-containing wastewater is presented. The electrocoagulation system used consists of a continuous-mode electrocoagulator connected with a gas separation tank and two sedimenters. It is shown that a significant amount of hydrogen can be harvested using the gas separation tank whose configuration follows that of a conventional upflow anaerobic sludge bed. The experimental hydrogen yields obtained were comparable with those calculated from theory. The electrical energy demand of the electrocoagulation process for treating Reactive Blue 140 and Direct Red 23 was 1.42 and 0.69 kWh e m −3, respectively, while the energy yield of harvested hydrogen was 0.2 kWh m −3. The quality of water treated by the electrocoagulation system was satisfactory, i.e., the color, COD and TS removal were 99%, 93% and 89%, respectively.

Experimental studies and empirical models for the prediction of bed expansion in gas–solid tapered fluidized beds

Studies in the expansion behaviour of tapered fluidized bed systems are important for specifying the height of the bed. Data have been obtained on the expanded heights of tapered fluidized beds and bed expansion ratios for spherical and non-spherical particles have been calculated. Based on dimensional analysis, models have been developed as a function of geometry of tapered bed, static bed height, particle diameter, density of solid and gas and superficial velocity of the fluidizing medium. The data used to derive the models cover a wide range of operating conditions, with varying fluidization velocities. Effects of static bed height, particle diameter, density, tapered angle and superficial gas velocity over minimum fluidization velocity on bed expansion ratios have been investigated experimentally. A comparison has been made between the calculated values of bed expansion ratios using proposed models and the experimental data. It has been seen that calculated values by models agree well with the experimental values. Models have also been compared with literature data of conventional bed and found its applicability at higher gas velocities with good accuracy.

Permanent raised bed planting of the pigeonpea–wheat system on a Typic Ustochrept: Effects on soil fertility, yield, and water and nutrient use efficiencies

In the Indo-Gangetic Plain region, a major deterrent to large scale adoption of the otherwise advantageous pigeonpea–wheat cropping system is the poor crop stand of pigeonpea due to temporary water logging during the rainy (monsoon) season, leading to its low productivity and a smaller residual effect on the succeeding wheat crop. The permanent raised bed (PRB) system of planting, as widely used particularly for wheat in different countries, has seldom been studied in the pigeonpea–wheat system. We, therefore, conducted a field experiment at Modipuram (29°4′N, 77°46′E, 237 m asl), India, for 3 consecutive years (2001–02 to 2003–04) to evaluate the PRB vis-à-vis the conventional flat bed (FB) system of planting at varying fertilizer NP rates in the pigeonpea–wheat system, in terms of changes in soil organic carbon, nutrient and water use efficiencies, annual productivity and economic returns. Pigeonpea grown on PRB had lower plant mortality (4–7%) and higher yield (1.6–2.1 t ha −1) as compared to FB with 26–36% mortality and yield of 1.3–1.8 t ha −1. Pigeonpea on PRB had greater N and P recycling (11–23% N and 8–14% P) through its residue comprising root, stubble and leaf litter. Although wheat yield following pigeonpea under PRB was lower ( p < 0.05) compared with that under FB, the system productivity in terms of wheat equivalent yield was 8.44% higher under PRB. The economic optimum doses of fertilizer N and P for wheat in the pigeonpea–wheat system were smaller (128 kg N and 28 kg P ha −1) under PRB as compared to FB (152 kg N and 30 kg P ha −1) owing to increased N and P supply, greater P use efficiency and a better crop growth environment under PRB planting. The N use efficiency indices were significantly greater ( p < 0.05) in wheat under FB compared to those under PRB. By contrast, P use efficiency was greater under PRB, particularly in treatments that received both N and P fertilizers. Compared with FB, the root mass density (20–46%) of wheat was also greater under PRB in surface and sub-surface soil layers. PRB favored saving of irrigation water by 9.5–13.4 ha cm and improved the irrigation application efficiency by 9.5–13.4% and the irrigation use efficiency by 19–28 kg ha cm −1 over FB. The post-wheat harvest nitrate N (NO 3-N) at 20–40 cm soil depth in plots fertilized with 120 or 180 kg N ha −1 was greater under FB planting (10.25–13.81 mg kg −1) compared to PRB (7.33–8.42 mg kg −1), suggesting that PRB planting might reduce NO 3-N leaching to deeper soil layers. Similarly, in the treatments that received both N and P, NO 3-N in soil below 20 cm depth was lower compared to those receiving N or P alone. After three crop cycles, soil OC and the Olsen-P content in the 0–20 cm depth were increased compared to the initial content under both planting techniques but the magnitude of increase was greater under PRB. Compared with FB, the annual net returns of the pigeonpea–wheat system were greater by US$ 210 ha −1 under PRB, and the crop also required less specific energy (1.99 MJ kg −1) compared with the FB planting (3.18 MJ kg −1).

Identification of defluidization region in a gas-solid fluidized bed using a method based on pressure fluctuation measurements

Industrial applications that involve fluidized bed operations must prevent the undesirable phenomenon of partial or complete bed defluidization. Defluidization can be avoided by increasing the gas velocity and/or, in some cases, changing the solid feed conditions in the system, provided that the changes in the hydrodynamics of the flow are detected early enough. The use of a technique that can perform an early detection of the defluidization condition in industrial applications is important, in order to avoid the loss of efficiency or even an undesirable shutting down of the process. The objective of this work is to show the application of a method for early detection of the condition where the bed is tending to the defluidization, in a gas-solid fluidized bed flow. The method is based on pressure fluctuation measurements. Experimental tests are carried out using two solid particles: microcrystalline cellulose and sand. Results show that the proposed method is efficient in detecting the fluidization condition in a conventional bubbling bed regime. The potential of application of the technique is also shown for the control of the defluidization phenomenon in industry.

Analysis of pressure fluctuations during water evaporation in spouted bed

AbstractThe aim of this work was to study the behaviour of conventional spouted beds during water evaporation and to analyze the pressure fluctuations at the maximum water evaporative capacity for different bed heights and air flow rates. The results showed that spout pressure drop could not indicate the proximity of maximum evaporative capacity; however this condition is denoted by a minimum in fountain height. The standard deviation and amplitude of the pressure fluctuations also showed a minimum point at the maximum water evaporation capacity. The frequency domain analysis of pressure fluctuations revealed that the dry bed has a dominant frequency varying from 6 to 8.2 Hz and that the peak of dominant frequency tends to disappear with the increase in water feed rate.

Flow-dependent entrapment of large bioparticles in porous process media.

The need for purification of biomolecules extends to larger bioparticles as well. For example, virus purification is required for production of many vaccines and gene delivery vectors, and understanding virus removal in porous media is also important in downstream processing of therapeutic proteins and in purification of water in soils. A convective entrapment mechanism for retention of large bioparticles is discussed here based on retention of such bioparticles in pore constrictions at high enough flow rates, even under non-binding conditions. A simple equation to predict whether such entrapment is expected to occur in a given system is derived based on a Péclet number that is proportional to the flow rate and to the cube of the bioparticle diameter. To test the theory, adenovirus was spiked onto chromatographic beds. As expected from the theory, under non-interacting conditions a progressively larger amount of virus becomes trapped with increasing flow rate. The entrapment is reversible upon flow rate reduction, which, within the proposed model, is based on the possibility of diffusive escape from pore constrictions. This mechanism can be exploited for virus purification or removal, and the theory is also consistent with the anecdotal evidence that monoliths and membranes are more difficult to clean than conventional chromatographic beds, especially at high flow rates.

Hybrid sediment gravity flow deposits – Classification, origin and significance

The deposits of subaqueous sediment gravity flows can show evidence for abrupt and/or progressive changes in flow behaviour making them hard to ascribe to a single flow type (e.g. turbidity currents, debris flows). Those showing evidence for transformation from poorly cohesive and essentially turbulent flows to increasingly cohesive deposition with suppressed turbulence ‘at a point’ are particularly common. They are here grouped as hybrid sediment gravity flow deposits and are recognised as key components in the lateral and distal reaches of many deep-water fan and basin plain sheet systems. Hybrid event beds contain up to five internal divisions: argillaceous and commonly mud clast-bearing sandstones (linked debrite, H3) overlie either banded sandstones (transitional flow deposits, H2) and/or structureless sandstones (high-density turbidity currents, H1), recording longitudinal and/or lateral heterogeneity in flow structure and the development of turbulent, transitional and laminar flow behaviour in different parts of the same flow. Many hybrid event beds are capped by a relatively thin, well-structured and graded sand–mud couplet (trailing low-density turbulent cloud H4 and mud suspension fallout H5). Progressive bed aggradation results in the deposits of the different flow components stacked vertically in the final bed. Variable vertical bed character is related to the style of up-dip flow transformations, the distance over which the flows can evolve and partition into rheological distinct sections, the extent to which different flow components mutually interact, and the rate at which the flows decelerate, reflecting position (lateral versus distal) and gradient changes. Hybrid beds may inherit their structure from the original failure, with turbidity currents outpacing debris flows from which they formed via partial flow transformation. Alternatively, they may form where sand-bearing turbidity currents erode sufficient substrate to force transformation of a section of the current to form a linked debris flow. The incorporation of mud clasts, their segregation in near-bed layers and their disintegration to produce clays that can dampen turbulence are inferred to be key steps in the generation of many hybrid flow deposits. The occurrence of such beds may therefore identify the presence of non-equilibrium slopes up-dip that were steep enough to promote significant flow incision. Where hybrid event beds dominate the entire distal fan stratigraphy, this implies either the system was continually out of grade in order to freight the flows with mud clasts and clays, or the failure mechanism and transport path repeatedly allowed transmission of components of the initial slumps distally. Where hybrid beds are restricted to sections representing fan initiation, or occur more sporadically within the fan deposits, this could indicate shorter episodes of disequilibrium, due to an initial phase of slope re-adjustment, or intermittent tectonically or gravity-driven surface deformation or supply variations. Alternatively, changes between conventional and hybrid event beds may record changes in the flow generation mechanism through time. Thus the vertical distribution of hybrid event beds may be diagnostic of the wider evolution of the fan systems that host them.

Conventional and modified fluidized bed: Comparison of the fluid dynamics and application in particle granulation

The goal of this study was to evaluate the fluid dynamic behavior of both conventional and draft tube fluidized beds, with and without injection of compressed air (at 68.95, 103.42 and 137.89 kPa) to assess their suitability for granulation. A 35% maltodextrin solution was sprayed on microcrystalline cellulose particles by a double-fluid nozzle. The tube heights tested indicate an 8 cm maximum height from the distribution plate. Beyond this value, fluidization is similar to that of a conventional bed. The growth occurred by nucleation and consolidation of particles and the post-granulation parameters analyzed were growth, angle of repose and granule circularity.

Control of Fruit Rots of Processing Tomato Using Cover Crop Mulch and Tom-Cast

The effects of three bed systems [conventional (bare soil), chemically killed, or mechanically killed winter rye (Secale cereale) + hairy vetch (Vicia villosa) cover crop mulch] and five fungicide programs (no fungicide, 7-day fungicide application program, and Tom-Cast-timed fungicide applications at 15, 18, or 25 disease severity values) on marketable yield and soil-borne fungal fruit rot development in processing tomato (Solanum lycopersicum) production were studied. In 1997, marketable yield was higher in both cover crop systems compared with the conventional bed system. In 1997, percentage of anthracnose- (Colletotrichum coccodes) and ground rot-infected fruit (caused by Pythium spp. or Phytophthora spp.) were lower in both cover crop mulch systems compared with the conventional bed system. In 1998, marketable fruit yields were lower in both cover crop mulch systems compared with the conventional bed system. Percentage of anthracnose-infected fruit was lower in 1998 in the chemically killed cover crop mulch system compared with mechanically killed bed system. There were no differences in ground rot-infected fruit between bed systems in 1998. In 1998, percentage of total molded fruit in the chemically killed cover crop mulch system was reduced compared with the mechanically killed cover crop mulch system.

Control of Fruit Rots of Processing Tomato Using Cover Crop Mulch and Tom-Cast

The effects of three bed systems [conventional (bare soil), chemically killed, or mechanically killed winter rye (Secale cereale) + hairy vetch (Vicia villosa) cover crop mulch] and five fungicide programs (no fungicide, 7-day fungicide application program, and Tom-Cast-timed fungicide applications at 15, 18, or 25 disease severity values) on marketable yield and soil-borne fungal fruit rot development in processing tomato (Solanum lycopersicum) production were studied. In 1997, marketable yield was higher in both cover crop systems compared with the conventional bed system. In 1997, percentage of anthracnose- (Colletotrichum coccodes) and ground rot-infected fruit (caused by Pythium spp. or Phytophthora spp.) were lower in both cover crop mulch systems compared with the conventional bed system. In 1998, marketable fruit yields were lower in both cover crop mulch systems compared with the conventional bed system. Percentage of anthracnose-infected fruit was lower in 1998 in the chemically killed cover crop mulch system compared with mechanically killed bed system. There were no differences in ground rot-infected fruit between bed systems in 1998. In 1998, percentage of total molded fruit in the chemically killed cover crop mulch system was reduced compared with the mechanically killed cover crop mulch system.