• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.160-166
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• 1996

Objective of this study was to investigate the effects of all current speed on the microclimates above and inside the plug stand under artificial light. Maximum air temperature appeared near the top of the plug stand. Difference in air temperature inside the plug stand increased with the decreasing air current speed. Difference in relative humidity(DRH) to the relative humidity at the Inlet of the main air flow conditioner Inside and above the plug stand decreased with the increasing air current speed. Relative humidity inside the plug stand was 10-15% higher than that above the plug stand. DRH inside a stand of plug at air current speed of 0.3m s$^{-1}$ was about two times as many as that at air current speed of 0.9 m s$^{-1}$ . DRH inside the plug stand was 2.8-6.5% higher at LAI of 2.6 than that at LAI of 0.5. Gradient for the vapour pressure deficit was distinctly appeared at the low air current speed. Direction of vapour pressure flux is from the medium surface upwards. Difference in vapour pressure(DVPD) to the vapour pressure deficit at the inlet of the main air flow conditioner inside and above the plug stand decreased with the increasing height above the medium surface. DVPD inside the plug stand was 0.3-0.4㎪ higher at air current speed of 0.9m s$^{-1}$ than that at air current speed of 0.3m s$^{-1}$ . Results for the effects of air current speed on the relative humidity and vapour pressure deficit indicated that the microclimates above and inside the plug stand at the rear region in plug trays were slightly unfavorable compared to those at middle region.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.213-220
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• 2000

Grafting of fruit-bearing vegetables has been widely used to increase the resistance to soil-borne diseases, to increase the tolerance to low temperature or to soil salinity, to increase the plant vigor, and to extend the duration of economic harvest time. After grafting, it is important to control the environment around grafted seedlings for the robust joining of a scion and rootstock. Usually the shading materials and plastic films are used to keep the high relative humidity and low light intensity in greenhouse or tunnel. It is quite difficult to optimally control the environment for healing and acclimation of grafted seedlings under natural light. So the farmers or growers rely on their experience for the production of grafted seedling with high quality. If artificial light is used as a lighting source for graft-taking of grafted seedlings, the light intensity and photoperiod can be easily controlled. The purpose of this study was to develop a prototype system for the graft-taking enhancement of grafted seedlings using artificial lighting and to investigate the effect of air current speed on the distribution of air temperature and relative humidity in a graft-taking enhancement system. A prototype graft-taking system was consisted by polyurethane panels, air-conditioning unit, system controller and lighting unit. Three band fluorescent lamps (FL20SEX-D/18, Kumho Electric, Inc.) were used as a lighting source. Anemometer (Climomaster 6521, KANOMAX), T-type thermocouples and humidity sensors (CHS-UPS, TDK) were used to measure the air current speed, air temperature and relative humidity in a graft-taking system. In this system, air flow acted as a driving force for the diffusion of heat and water vapor. Air current speed, air temperature and relative humidity controlled by a programmable logic controller (UP750, Yokogawa Electric Co) and an inverter (MOSCON-G3, SAMSUNG) had an even distribution. Distribution of air temperature and relative humidity in a graft-taking enhancement system was fairly affected by air current speed. Air current speed higher than 0.1m/s was required to obtain the even distribution of environmental factors in this system. At low air current speed of 0.1m/s, the evapotranspiration rate of grafted seedlings would be suppressed and thus graft-taking would be enhanced. This system could be used to investigate the effects of air temperature, relative humidity, air current speed and light intensity on the evaportranspiration rate of grafted seedlings.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.152-159
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• 1996

Experiment was performed in a newly developed wind tunnel with light system to determine the aerodynamic resistance and eddy diffusivity above the plug stand under artificial light. Maximum air temperature appeared near the top of the plug stand under artificial light. Since Richardson number was ranged from -0.07 to +0.01, the atmosphere above the plug stand in wind tunnel was in an unstable or near- neutral stability state. The average aerodynamic resistance at rear region of plug stand was 25 % higher than that at middle region. Eddy diffusivity($K_{M}$) linearly increased with the increasing air current speed. $K_{M}$ at air current speed of 0.9 m.$s^{-1}$ was about two times as many as that at air current speed of 0.3 m.$s^{-1}$. And average $K_{M}$ at the rear region was 15% lower than that at the middle region. These results indicated that the diffusion of heat and mass along the direction of air current inside the plug stand was different. It might cause the lack of uniformity in the growth and quality of plug seedlings. The wind tunnel developed in this study would be useful to investigate the effects of air current speed on microclimates and the growth of plug seedlings under artificial light in a semi- closed ecosystem.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.9-14
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• 1998

Air current speeds were controlled of 0.3, 0.5, 0.7 and 0.9 m.s$^{-1}$ to investigate the effects of air current speeds on the growth of eggplant plug seedlings (Solanum melongena L.) in a wind tunnel under artificial lighting. Growth of plug seedlings was influenced by the magnitude of air current speed and the traveling distance of regulated air flow. Stem length. ratio of length to diameter in stem, plant height .and number of leaves of plug seedlings decreased with the increasing air current speed and were significantly different at 5% level. Net photosynthetic rates of plug stand increased with the increasing air current speed and took a maximum value at the air current speed of 0.7~09 m.s$^{-1}$ . Stem diameter decreased and leaf area increased with the traveling distance of regulated air flow. Fresh weight and T/R ratio of dried weight were not influenced by the air current speed. Optimum control for microclimates inside the plug stand is needed to produce the uniform growth and high quality of plug seedlings in a semi-closed plant Production system under artificial lighting.

• Journal of Biosystems Engineering
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• v.21 no.4
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• pp.429-435
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• 1996

A wind tunnel consisting of two air flow conditioners with polycarbonate pipes, a plant growth room, a suction fan and fan controller, and fluorescent lamps, was designed to investigate the interactions between the growth of plug seedlings under artificial light and their Physical environments. Light transmissivities in the plant growth room based on the photosynthetic photon flux density and photosynthetically active radiation was appeared to be 96.3% and 96.8%, respectively. Measurement showed a uniformity in the vertical profiles of air current speed at the middle and rear regions of plug trays in wind tunnel. This result indicated that the development of a wind tunnel based on the design criteria of the American Society of Mechanical Engineers was adequate. Air current speed inside the plug stand was significantly decreased due to the resistance by the leaves of plug seedlings and boundary layer developed over and below the plug stand. Driving force to facilitate the diffusion of gas inside the plug stand might be regarded as extremely low. Aerodynamic characteristics above the plug stand under artificial light were investigated. As the air current speed increased, zero plane displacement decreased but roughness length and frictional velocity increased. Zero plane displacement linearly increased with the average height of plug seedlings. The wind tunnel developed in this study would be useful to investigate the effects of air current speed on the microclimate over and inside the plug stand and to collect basic data for a large-scale plug production under artificial light in a semi-closed ecosystem.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.8-14
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• 2020

In the air current pulverizing type grinding method, the blade wings fitted inside a casing are rotated at a high speed to generate a cornering air current, which facilitates the collision of materials with one another, leading to the pulverizing phenomenon. In contrast to mechanical grinding, grit pulverizing leads to fine grinding and less acid waste and degeneration of the material. Moreover, this approach prevents the loss of nutritional value, while allowing the milling grain to have an excellent texture. However, the existing air current pulverizing type machines consist of prefabricated blades, which cannot be rotated at a speed higher than 5,000 rpm. Consequently, the grinding process becomes time consuming with a low productivity. To overcome these problems, in this study, the shape and structure of the air current pulverizing type wings were optimized to allow rapid grinding at more than 8,000 rpm. Moreover, the optimal design for the ripening parts for the air current pulverizing type device was determined by performing a computational fluid dynamics analysis based on airflow analyses to produce machinery that can grinding materials to the order of micrometers.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.4
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• pp.137-144
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• 2008

This study deals with on-line fault detection and diagnosis(FDD) for heat exchangers of a variable speed refrigeration system(VSRS) based on current information. The current residual which is the difference between real detected current from current sensors and estimated current from no fault model was utilized to diagnose faults of the heat exchangers. Comparing to the conventional FDD of constant refrigeration system based on temperature and pressure information, the suggested FDD method shows better robustness to the VSRS which has a feedback control loop. Moreover the suggested method can be expected more precise and faster diagnosis of faults about heat exchangers. Throughout some experiments, the validity of the method was verified.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.310-317
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• 2014

Purpose: This study was conducted to analyze the air flow characteristics in a plant factory with different inlet and outlet locations using computational fluid dynamics (CFD). Methods: In this study, the flow was assumed to be a steady-state, incompressible, and three-dimensional turbulent flow. A realizable k-${\varepsilon}$ turbulent model was applied to show more reasonable results than the standard model. A CFD software was used to perform the numerical simulation. For validation of the simulation model, a prototype plant factory ($5,900mm{\times}2,800mm{\times}2,400mm$) was constructed with two inlets (${\Phi}250mm$) and one outlet ($710mm{\times}290mm$), located on the top side wall. For the simulation model, the average air current speed at the inlet was $5.11m{\cdot}s^{-1}$. Five cases were simulated to predict the airflow pattern in the plant factory with different inlet and outlet locations. Results: The root mean square error of measured and simulated air current speeds was 13%. The error was attributed to the assumptions applied to mathematical modelling and to the magnitude of the air current speed measured at the inlet. However, the measured and predicted airflow distributions of the plant factory exhibited similar patterns. When the inlets were located at the center of the side wall, the average air current speed in the plant factory was increased but the spatial uniformity was lowered. In contrast, if the inlets were located on the ceiling, the average air current speed was lowered but the uniformity was improved. Conclusions: Based on the results of this study, it was concluded that the airflow pattern in the plant factory with multilayer cultivation shelves was greatly affected by the locations of the inlet and the outlet.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.88-94
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• 2007

This study deals with on-line fault detection and diagnosis for heat exchanger of variable speed refrigeration system. Conventional studies about fault of heat exchanger in refrigeration system have used temperature and pressure information. The temperature and pressure are able to be used valuably for faults detection of constant speed refrigeration system. However in case of variable speed refrigeration system, the temperature and pressure are no longer useful information for fault detection due to compensation effect of feedback controller. While current information is possible to detect faults of variable speed refrigeration system. The current information was detected in an inverter, it was used after transforming rms value. The faults of variable speed refrigeration system are divided into electrical faults and mechanical faults. We performed fault detection and diagnosis about heat exchanger among mechanical faults such as condenser fouling and evaporator fan fouling through some experiments.

• Journal of Biosystems Engineering
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• v.22 no.3
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• pp.311-316
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• 1997

Two methods were used to detrermine the net photosynthetic rate(NPR) in the plug stand using a wind tunnel for plug seedlings Production. One is called as the integration method in which NPR calculated by the use of air current speed and $CO^2$ concentration measured at any heights above the medium surface in a wind tunnel were summed. It was assumed that the air flow at any layer did not mix with the lower or upper air layer. The other is called as the diffusion method in which eddy diffusivities above the plug stand were used to determine the NPR in the plug stand. In this method, $CO^2$ above or inside the plug stand was assumed to be absorbed vertically. NPR determined by the diffusion method was 28~45% of the NPR calculated by the integration method. Considering the magnitude of NPR and the effects of the air current speed on NPR, the integration method would be adequate for the calculation of NPR in the plug stand. Maximum NPR determined using the integration method appeared at the air current speed of 0.7m $s^{-1}$. It was ascribed to the decreased diffusion resistances of $CO^2$ with the increasing air current speed. NPR at the rear region in plug stand was 20~34% lower than that at the front region. NPR sharply decreased with the increase of an elapsed time after the beginning of photoperiod. Therefore $CO^2$ enrichment would be effective to force the growth of plug seedlings in a semi-closed ecological system under artificial lighting.