• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.91-98
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• 1999

This paper describes the air flow characteristics inside the throttle valve. Tow-dimensional steady incompressible Navier-Strokes equation are solved numerically with embedding the conceopt of the artificial compressibility and adopting the Baldwin-Lomax turbulence model. With varying the valve opening angles(the Reynolds number )such as 15$^{\circ}$(5000) , 45$^{\circ}$(3000) , 75$^{\circ}$(7000) and 90$^{\circ}$(10000), respectively. tow cases, with a valve shaft and without one, are analysed. The pressure loss between the entrance and exit is severe at 15$^{\circ}$, 100 times as larger as that of 90$^{\circ}$ case, which also depends much on the existece of the valve shaft. The counter rotating vortices are formed over the valve plate with the shaft at only 75$^{\circ}$. They are smally and very large scale in front and back of the valve shaft , respectively. The velocity profiles of 15$^{\circ}$ and 90$^{\circ}$ at the exit are almost symmetric to the horizontal center line, however, the symmetricity is no longer maintained at 45$^{\circ}$ and 75$^{\circ}$ , and in addition, the flow at 75$^{\circ}$ is enforced a lot below center line. The pressure distribution on the walls is largely changed near the valve shaft, and its magnitude becomes great as the valve angle decreases.

• Journal of the Korean Society of Food Culture
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• v.10 no.1
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• pp.35-44
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• 1995

A hazard analysis which included watching operations, measuring temperatures of foods throughout preparation and display, and sampling and testing for microorganisms of total plate counts and coliform bacteria was conducted in various phases of product flow of Korean soups (Galbitang, Sullungtang, Jangkuk) prepared at Korean restaurants. Cooked foods were sometimes held at room temperature long enough to permit multiplication of bacteria that might have been present. This was confirmed by the finding of large numbers of aerobic mesophilic colonies ($10^6$) in samples of such foods after handling and holding for several hours before served. These bacteria decreased down to $10^1{\sim}10^2$ while the contaminated Tang were served. And internal temperature of Tang served was approximately $70^{\circ}C$. Critical control points identified were, pre-preparation, handling after cooking and holding on display. Guidelines were suggested for effective quality control of Tang (Korean soups) production. Handlers of these foods need to be informed of the hazards and appropriate preventive measures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.386-398
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• 1998

The present experiment is conducted to investigate heat transfer characteristics on the impinging surface with secondary flows around circular nozzle jets. The changed vortex pattern around jet affects significantly the flow characteristics and heat transfer coefficients on the impinging surface. The effects of the jet vortex control are also considered with jet nozzle-to-plate distances and main jet velocities. The vortex pattern around a jet is changed from a convective instability to an absolute instability with a velocity suction ratio of the main jet and the secondary counterflow. With the absolute instability condition, the jet potential core length increases and the heat transfer on the impinging surface is increased by small scale eddies. The region of high heat transfer coefficients is enlarged with the high Reynolds number due to increasing secondary peak values. The effect of suction flows is influenced largely with collars attached the exit of the jet nozzle because the attached collar guides well the counterflow around the main jet.

• Wind and Structures
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• v.28 no.6
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• pp.355-367
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• 2019

Control of horseshoe vortex in the circular cylinder-plate juncture using vortex generator (VG) was studied at $Re_D$(where D is the diameter of the cylinder) = $2.05{\times}10^5$. Impact of a number of parameters e.g., the shape of the VG's, number of VG pairs (n), spacing between the VG and the cylinder leading edge (L), lateral gap between the trailing edges of a VG pair (g), streamwise gap between two VG pairs ($S_{VG}$) and the spacing between the two VG's in parallel arrangement ($Z_{VG}$) etc. were investigated on the horseshoe vortex control. The study is conducted using surface oil flow visualization and surface pressure measurements in low speed wind tunnel. It is observed that all the parameters studied have significant control effect, either by reduction in separation region or by lowering the adverse pressure along the symmetric axis upstream of the juncture.

• Journal of computational fluids engineering
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• v.12 no.2
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• pp.37-45
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• 2007

The hybrid Cartesian/immersed boundary method is applied to simulate fluid-structure interaction of a two-dimensional orbiting flexible foil. The elastic deformation of the flexible foil is modelled based on the dynamic equation of a thin-plate. At each time step, the locations and velocities of the Lagrangian control points on the flexible foil are used to reconstruct the boundary conditions for the flow solver based on the hybrid staggered/non-staggered grid. To test the developed code, the flow fields around a flapping elliptical wing are calculated. The time history of the vertical force component and the evolution of the vorticity fields are compared with recent other computations and good agreement is achieved. For the orbiting flexible foil, the vorticity fields are compared with those of the case without the deformation. The combined effects of the angle of attack and the orbit on the deformation are investigated. The grid independency study is carried out for the computed time history of the deformation at the tip.

• Journal of the Korean Society of Safety
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• v.21 no.5 s.77
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• pp.12-16
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• 2006

This paper deals with the noise evaluation and noise reduction of a reciprocating air-compressor. The reciprocating air-compressor is widely used in the small and medium sized industrial firms, many employees exposed and irritated by their noise in the workplace. Thus, appropriate noise control actions should be taken to prevent hearing loss due to the its noise exposure. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known to be motor, belts, suction valves, discharge valves, moving parts, and flow-induced noise caused by edges or discontinuities along the flow path including expansions, contractions, junctions and bends. As a result, the main noise sources of the air-compressor are categorized by the suction and discharge noise, valve noise, and compressed air tank noise. Based on the investigations, mufflers are designed to reduce both the suction and discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, polyethylene resin is used the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings. As a result of the countermeasure plans, a noise reduction up to 10dB(A) could be achieved for the air-compressor.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.718-725
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• 2003

The present study addresses the distortion of the compression wave reflected from an open end of a shock tube. An experiment is carried out using the simple shock tube with an open end Computational work is also performed to represent the experimented flows. The second-order Total Variation Diminishing scheme is employed to numerically solve the unsteady, axisy-mmetric, inviscid, compressible governing equations. Both the experimented and predicted results are in good agreement. The generation and development mechanisms of the compression wave, which Is reflected from the open end of the shock tube, are obtained in detail from the present computations. The effect of size of the baffle plate at the open-end that causes the reflection of the incident expansion wave is found negligible. A good correlation is obtained for transition of the reflected compression wave to a shock wave inside the tube. The present data show that for a given wave length of the incident expansion wave the transition of the reflected compression wave to a shock wave can be predicted with good accuracy.

• Korean journal of food and cookery science
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• v.4 no.2
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• pp.71-79
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• 1988

This study is written to look into microbiological quality by passage of time and holding methods after making foods, by means of evaluating time, temperature and microbiological quality during various phases in product flow of cold soybean noodles serviced by an industry feeding operation for 500 persons a day, measuring pH & Aw and analyzing factors affecting microbiological growth conditions. The results were as follows: 1. According to phases in product flow of cold soybean noodles, it showed 15.6 hours of mean of needed time, $24.2^{\circ}C$ of room temperature, 5.1~7.6 of pH value & 0.95~0.98 of Aw except dry noodles. These conditions were good for multipling of microbe, and the phases with potential sanitary danger were ingredient, pre-preparation, holding before assembly and service and assembly & service. 2. As for holding methods and passage of time, holding at cold table was more effective than holding at room temperature as time past. 3. As for equipments using for making food, dipper, basket, kitchen board & kitchen towel showed high microbiological value in total aerobic plate counts and kitchen towel and stainless-steel were showed high microbioloical value in coliform counts. 4. E. coli, food poisoning bacteria was detected from barrel filled with soybean soup and also soybean itself.

• Journal of the Korean Home Economics Association
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• v.43 no.2
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• pp.19-31
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• 2005

The purpose of this study was to evaluate the microbiological quality and assure the hygienic safety of the Bibimbap production in elementary school foodservice in accordance with the HACCP(Hazzard Analysis Critical Control Point) program. The time-temperature relationship and the microbiological quality(total plate count and coliform bacteria count) were assessed to find the critical control point(CCP) during each of the production phase. In the pre-preparation phase, the risk factors of the raw ingredients exceeded the standard level suggested by Solberg et al. Mungbean starch jelly, egg and Kochujang were satisfactory in that no coliform groups were observed over the standard TPC level. In particular, there was a high the risk of beef from the early stages in terms of the coliform level. In the pre-preparation phase, green pumpkin had more coliform groups than the standard level even after washed, which calls for special attention to washing, sterilization, secondary infection of the handler, and the required time for pre-preparation of raw vegetables. In the cooking phase, the temperature of the soybean sprout and mungbean starch jelly decreased to 42$^{\circ}C$ and 26$^{\circ}C$, respectively, which was within the risk zone. In particular, mungbean starch jelly had a great risk factor even after boiling in hot water. During the storage stage before serving, a lot of ingredients were exposed to poor management of temperature and time and thus exceeded the standard level in the total plate counts. In particular, the microbiological count of beef was five times the standard level. Green pumpkins and soybean sprouts were left at 15-38$^{\circ}C$ that is within the risk zone for a long period of time after they were cooked. It is highly recommended that the time of the storage stage before consumption should be shortened and that proper devices should be used to prevent proliferation of bacteria. The number of TPC of the utensils was satisfactory enough, but the knife used exceeded the standard level and thus was a risk factor of bacteria proliferation.

• Korean journal of food and cookery science
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• v.24 no.5
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• pp.713-721
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• 2008

The principal objective of this study was to evaluate the microbiological quality of Glazed Spanish Mackerel in Teriyaki sauce by adding Lemon juice, using a Sous vide Cook-chill method. The control was prepared by mixing 100 g of cut Spanish Mackerel and 15 mL of Teriyaki sauce. 1.5 mL lemon juice was added to 15 mL of Teriyaki sauce. The product was stored at below $3^{\circ}C$, and its microbiological quality was assessed over varying storage periods (0, 5, 10, 15 days). Total Plate Counts at product flow showed no significant difference between the control and the lemon juice-added sample. However, the coliform counts at the end of mixing each sauce were detected at low levels of 1.65 Log CFU/g in the lemon juice-added sample, as opposed to 2.63 Log CFU/g in the controls (p<0.05). The microbiological quality by storage day was relatively high in the lemon juice-added samples. After reheating, the Total Plate Counts and Coliform counts of the lemon juice-added samples satisfied the standard applied in the processed food (5.0 and 2.0 Log CFU/g, respectively). It can be concluded that the addition of Lemon juice was more effective in ensuring the safety and extending the shelf life of Sous vide Glazed Spanish Mackerel in Teriyaki sauce.