• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.226-233
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• 1990

Fixed bed is known to be an effective heat transfer augmentation device which could be applied to heat exchangers. In this study, pressure drop in vertical cylindrical and annular fixed beds with air flowing through was experimentally investigated. Based on the experimental data and some analytical considerations, the demensionless correlation of pressure drop has been determined and shown in empirical forms. In particular, the experimental equation for the pressure drop was derived using the particle diameter and the bed diameter as variables, which would be more practical and useful in the design of heat transfer devices, instead of void fraction which had been used previously as the major variables by others. The present empirical equation obtained for the cylindrical fixed bed were found to be applicable also to an annular fixed bed when the concept of effective diameter was introduced.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.117-124
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• 1996

A fluidized bed combustion chamber is widely used to incinerate waste material. The most important factor designing the incinerator is the flow characteristics in a fluidized bed, because combustion efficiency is influenced by the flow characteristics. This paper has invesitigated the flow characteristics of bubbles in fluidized bed by means of meassuring a pressure fluctuation in the fluidized bed. A pressure probe system has used to measure the pressure. The data concerned with bubble rising velocity, bubble size, distribution of bubbles and frequency of bubble generation or decay are obtained to find the flow characteristics of bubbles in the fluidized bed. The result obtained from this experimental study can be used to design the fuel feeding system of fluidized bed combustion type incinerator. And it is possible to predict the mixing of waste material and fluidizing material.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.117-129
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• 2022

The downward discharge of the molten fuel to the lower structure of the fuel assembly could increase of the pressure drop and degrade of coolability of the assembly. To analyze the phenomena, experiments for the generation of the debris bed were conducted as LOF-DT series. Based on the debris bed in the LOF-DT, pressure drop experiment was conducted with intact and blocked component. Parametric study on the pressure drop was conducted by CFD. The LOF-DT experiments were conducted for the position and porosity of the debris bed. 85% of the debris were sedimented in the lower reflector, and 15% were in the nose piece, approximately. Porosity of the debris bed were about 0.7 and 0.85 in the lower reflector and nose piece, respectively. Pressure drop increased significantly with debris bed, especially in the lower reflector. More than 120 time of the pressure drop increased in the lower reflector, while only 10% increased in the nose piece. According to the parametric study, mass of the debris was the most important for pressure drop. The lower discharge phenomena could have a significant effect to the total pressure drop of the fuel assembly, approximately 10.8 times for the base case.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1535-1538
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• 2004

In this paper, an Intelligent Bed Robot System (IBRS) is proposed, that is a special bed equipped with robot manipulator. To assist a patient using IBRS, pose and motion estimation process is fundamental. It is designed to help the elderly and the disabled for their independent life in bed without other assistants. For this purpose, we use the pressure sensor distributed mattress for detecting the change of motion on the bed. Using that data, we control the robot arm to move to the appropriate position and serve to the user. In addition, we can estimate the user's intention based on the change of pressure and use those data to control the robot arm guide.

• Journal of environmental and Sanitary engineering
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• v.11 no.1
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• pp.39-44
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• 1996

The pressure fluctuations in a gas-solid fluidized bed has been analysed using s statistical method interpreting fluidized 냥d behavior. The performing statistical a analysis of the pressure fluctuations in a fluidized bed of 6.7cm-ID. using uniform p particle size of 115 to $1015{\mu}m$ in diameter. The fluidized gas used air(velocity 0.1~1.2m/sec) at settled bed height to diameter ratios which is LlD=l.O. Then, the pressure fluctuations measured by DPT(differantial pressure transducer). The measuring characteristic values of pressure fluctuation were the mean value and standard value, and also, it has been found that the standard deviation of the pressure fluctuations can be effectively used to predict minimum fluidizing velocity and to explain the fluidized phenomena.

• International Journal of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.146-157
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• 2024

Despite numerous air mattresses marketed to prevent Pressure Ulcers (PU), none have fully succeeded due to residual pressure surpassing critical levels. We introduces an innovative medical bed system aiming at complete PU prevention. This system employs a unique 4-bar link mechanism, moving keys up and down to manage body pressure. Each of the 17 keys integrates a sensor controller, reading pressure from 10 sensors. By regulating motor input, we maintain body pressure below critical levels. Keys are equipped with a servo drive and sensor controller, linked to the main controller via two CAN series. Using fuzzy or PI/IP controllers, we adjust keys to minimize total error, dispersing body pressure and ensuring comfort. In case of controller failure, keys alternate swiftly, preventing ulcer development. Through experimental tests under varied conditions, the fuzzy controller with tailored membership functions demonstrated swift performance. PI control showed rapid convergence, while IP control exhibited slower convergence and oscillations near zero error. Our specialized medical robot bed, incorporating 4-bar links and pressure sensors, underwent testing with three controllers-fuzzy, PI, and IP-showcasing their effectiveness in keeping body pressure below critical ulcer levels. Experimental results validate the proposed approach's efficacy, indicating potential for complete PU prevention.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.886-895
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• 1993

Experimental were conducted to obtain information on the effect of airflow rates and bed depths on the resistance of coffee cherries and coffee beans available locally (Coffea Liberica). The airflow used were in the range of 0.06 to 0.6 cu. m/s-sq.m. The moisture content of the coffee cherries ranged from 10 % to 50% (wet basis) and that of coffee beans ranged from 12% to 30% )wet basis). Two methods of filling were used i.e. loose fill and packed fill. Pressure drops across the material bed in a vertical column were measured at several depths using inclined manometer. The pressure drop increased directly with air flow rate as well as bed depths. The effects of air flowrates and moisture contents on the resistance in terms of pressure drip per unit bed depth were analysed. The pressure drop per unit depth across the material bed varied slightly due to different depth. The resistance to airflow decreased with the increase in moisture content for loose fill. However, the effect of moisture content is not apparent for packed fill.

• Particle and aerosol research
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• v.19 no.4
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• pp.145-154
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• 2023

Granular bed filters are widely used to remove particulate matter in flue gas and are filled with various shapes of packing material. The packing material plays an important role in determining the overall collection performance, such as pressure drop and collection efficiency. The pressure drop of a granular bed filter has been calculated using the Ergun equation, while the collection efficiency has been predicted using the log-penetration equation based on the single sphere theory. However, a prediction equation of collection efficiency for a granular bed filter filled with non-spherical packing materials has not been suggested yet. Therefore, in this study, three different shapes of packing materials (sphere, cylinder, and irregular) were prepared to propose a prediction equation. The pressure drop and collection efficiency in a granular bed filter filled with each shape of packing material were measured experimentally and compared with theoretically predicted values. We found that experimentally measured pressure drops matched well with values theoretically predicted using the Ergun equation considering the shape factor. However, experimental collection efficiencies were higher than theoretical ones predicted by the log-penetration equation using the single sphere theory. We modified the log-penetration equation by employing a shape factor and found a good relationship between experimental and theoretical collection efficiencies.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.5
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• pp.24-28
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• 1994

In the present paper, the behavior of bubbles in a fluidized bed has been investigated experimentally. The bubble size, distribution of bubble, bubble rising velocity and pressure fluctuation in the fluidized bed are obtained at different air velocity. The results are discussed and compared study the effect of air velocity on the behavior of a bubbles in fluidized bed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1126-1133
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• 2004

This paper presents an experimental measurement of effective thermal conductivity in an adsorbent packed bed with silica gel A type. The effective thermal conductivity was measured under different conditions of the adsorbent bed temperature, pressure, particle size and water content by using the transient hot wire method. The measured effective thermal conductivity showed to become bigger with decreasing particle size or increasing water content, but it was a little affected with increasing bed temperature and pressure. The bed temperature was varied in the range of 1$0^{\circ}C$ (equation omitted) T (equation omitted) 5$0^{\circ}C$ and the pressure in the range of 10 kPa (equation omitted) P (equation omitted) 190 kPa. The results show that 0.10～0.18 W/mㆍK of effective thermal conductivity measured for the zero water content.