• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.5
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• pp.14-20
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• 2020

In this study, the overall states of the airflow when a truck with or without side pairing is driven at a maximum speed of 90 km/h, regulated by domestic law, were investigated through computational fluid dynamics numerical analysis. All the tested models showed that the airflow went under the truck body; specifically, the air did not flow along the underside to the rear of the truck but through the sides of its underside. The drag with the drag coefficient at model 3 was clearly higher than those for the other two models. The results of this study could help to improve the truck performance by reducing its resistance against the air flown from it in driving itself.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.725-732
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• 1999

It is usual to use hydrophilic-coated aluminum foil for evaporator fin of air-conditioners to reduce air flow resistance caused by the water droplets condensed on the fin surface. The major effect of a hydrophilic coating is to reduce the contact angle of the condensate and prevent bridging of the condensate between the adjacent fins. The performance of hydrophilic coating generally tends to be degraded as it is used since the coating material is washed down by the condensate. In the present work, several types of hydrophilic coatings were evaluated in terms of durability of hydrophilicity, corrosion resistance and heat resistance. Results showed that an improved hydrophilic coating of resin type presented superb qualify in terms of durability and corrosion resistance while having almost the same level of qualify in heat resistance compared with the others.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.4
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• pp.303-315
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• 1990

Uniformity of velocity is quite important design points of a vertical laminar flow type clean room. In the present paper, flows in a room with a bottom pannel are numerically simulated by using a low-Reynolds number $k-{\epsilon}$ model, and a new flow model of the pannel are suggested. Resistance coefficient of the pannel and size of the exhaust channel show considerable effects on flow pattern and uniformity of flow on the bottom. Reflection coefficient also has important roles. A possibility to obtain the uniform and unidirectional flow is tested by adjusting the distribution of resistance coefficient of the pannel. Such a numerical simulation of the flow will be a good method to get optimun design parameters.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.11-17
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• 2020

The reduction of CO2 emissions has been a key target in the marine industry since the IMO's MEPC published its findings in 2009. Air lubrication method is one of the mature technologies for commercialization to reduce the frictional resistance and enhance fuel efficiency of ships. Since the air lubrication pattern varies according to the ship's standing position and injection flow rate, in order to effectively control the air lubrication system, it is necessary to be able to judge the air layer development state based on the information collected from the monitoring sensor. In this study, we performed the air lubrication ship simulation experiment to measure the void fraction and the frictional resistance. The void fraction was measured to confirm the behavior of the air. Through the measurement of the frictional resistance, the change in frictional resistance reduction rate from the injection point to the longitudinal direction of the ship was confirmed. Based on the measurement results, correlation analysis was performed on void fraction and frictional resistance reduction rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.47-53
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• 1997

The importance of intake system can not be overstressed in the recent heavy duty commercial vehicle design. The basic requirements of intake system are to have less flow resistance and better air cleaning performance which have direct effects on the performance and service life of engine. In order to improve the performance of engine intake system, the flow phenomena in the intake system should be fully understood. With readily availble CFD code, the numerical analysis becomes the more reliable tools for flow optimization in recent design work. In this research, flow field in the intake system was analyzed by STAR-CD, the 3-D computational fluid dynamics code. Especially, the flow inside of air cleaner was thoroughly analyzed. Pressure distribution and velocity profile in the air cleaner and intake duct was obtained. Having the dust seperated from incoming air at the expense of less pressure drop is the ultimate goal for the research.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.6
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• pp.1913-1920
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• 1996

The purpose of this study was to reduce the airborne noise emitted from the package air-conditioner(PAC) therefore, the optimim design melthods of the fans and the flow-paths were investigated experimentally through the anlaysis of the nose problems caused by the conventional PAC system, and the fan performance tests and the systme resistance measurements of the parts which belong to the flow-paths of the PACwere used to study these noise problems. As a results, through the optimized flow-paths of the new PAC system with the lowset system resistance, and by adjusting and matching the operating point of each fan to each PAC system, the airborne noise reductions from the new indoor PAC and the outdoor one were achieved upto 5.5 dBA and 6.6 dBA respectively in overall noise level as compared with the conventional PAC system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.36-42
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• 2020

In this study, flow analyses of a vehicle at driving were carried out after each installation of a tuning part, specifically the bonnet air ducts, the rear spoiler, and the rear diffuser. The study models were designed to comprise a total of eight cases in which each of the three parts were mounted individually or all together in vehicles. Assuming that the vehicle were driven with an average high speed of 100 km/h, the speed and pressure around the vehicle were obtained using CFD when driving. The rear diffuser that becomes the most effective among the three mounting parts has a major role in reducing air resistance.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.565-572
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• 2022

The white plume from the cooling tower can be generated by mixing between discharging hot and humid air and cold air outside. This causes various problems such as icing, traffic disturbances, and fire factors in the vicinity, moreover it can also damage the image of a company. Various methods can be used to prevent white plume, one of them is to install a heat exchanger at the outlet of the cooling tower so that the heat exchanger transfers as much heat as possible to lower the temperature. Therefore the air flow path in the cooling tower should be optimized. Installation of the filler can be used to make the air flow better, thus we investigate the effect of filler on the air flow using CFD method. The pressure and velocity profile in the cooling tower could be acquired by the calculations. The filler made the velocity of the air entering the heat exchanger uniform this was because high flow resistance of the filler suppresses the generation of eddy in the cooling tower. But the total air pressure drop increased about 2 times with filler because the pressure drop by the filler accounted for about 60% of the total pressure drop.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.378-383
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• 2013

A butterfly throttle valve has been used to control the brake power of an SI engine by controlling the mass flow-rate of intake air in the induction system. However, the valve has a serious effect on the volumetric efficiency of the engine due to the pressure resistance in the induction system. In this study, a new intake air controlling valve named "Variable Geometry Throttle Valve(VGTV)" is proposed to minimize the pressure resistance in the intake system of an SI engine. The design concept of VGTV is on the application of a venturi nozzle in the air flow path. Instead of change of the butterfly valve angle in the airflow field, the throat width of the VGTV valve is varied with the operating condition of an SI engine. In this numerical study, CFD(computational fluid dynamics) simulation technique was incorporated to have an aerodynamics performance analysis of the two air flow controlling systems; butterfly valve and VGTV and compared the results to know which system has lower pressure resistance in the air intake system. From the result, it was found that VGTV has lower pressure resistance than the butterfly valve. Especially VGTV is effective on the low and medium load operating condition of an SI engine. The averaged pressure resistance of VGTV is about 49.0% lower than the value of the conventional butterfly throttle valve.

• The KSFM Journal of Fluid Machinery
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• v.6 no.2 s.19
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• pp.15-22
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• 2003

Comprehensive study on a centrifugal blower for air-purifier involving a few physical filters for percolation process has been accomplished for an optimal design of the air handling system. The filtering media causes a flow resistance for induced flows by a rotating impeller. The present methodology is to adopt PIV system for velocity measurements and wind tunnel connected with an anechoic chamber for total performance test of the blower. Trial prototypes for the blades of a rotor and casing are presented for satisfaction of both flow rate and noise level set by design objectives. Tapered blades with a special casing for a fan show good performance data. The results of velocity fields also explain the reason of improvements of the blower performance.