• 설비공학논문집
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• 제11권5호
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• pp.579-587
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• 1999

The flow distribution characteristics in a complex duct system have been investigated in this paper by three means, namely experimental measurement, numerical simulation and the Extended T-method analysis. While the exit flow rates predicted by the three-dimensional CFD calculation and those given by the experiment show a close agreement, the results from the one-dimensional Extended T-method are found to differ from the experiment by -22.2% to 26.3% for the various exits. These discrepancies may be attributed to the underlying limitation concerning the fitting loss coefficients, which assume that the flow in front of the fittings is fully developed. It is proposed that, in order to analyse the three-dimensional flow distributions in a complex duct system by one-dimensional analysis such as the Extended T-method, further Improvements to the fitting loss coefficients should be made.

• 설비공학논문집
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• 제15권10호
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• pp.809-820
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• 2003

The present study investigates effects of flow velocity on the convective heat/mass transfer characteristics in wavy ducts of a primary surface heat exchanger application. Local heat/mass transfer coefficients on the wavy duct sidewall are determined by using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The aspect ratio and corrugation angle of the wavy duct is fixed at 7.3 and 145$^{\circ}$ respectively, and the Reynolds numbers, based on the duct hydraulic diameter, vary from 100 to 5,000. The results show that there exist complex secondary flows and transfer processes resulting in non-uniform distributions of the heat/mass transfer coefficients on the duct side walls. At low Re (Re<1000), relatively high heat/mass transfer regions like cell shape appear on both pressure and suction side wall due to the secondary vortex flows called Taylor-Gortler vortices perpendicular to the main flow direction. However, at high Re (Re>1000), these secondary flow cells disappear and boundary layer type flow characteristics are observed on pressure side wall and high heat/mass transfer region by the flow reattachment appears on the suction side wall. The average heat/mass transfer coefficients are higher than those of the smooth circular duct due to the secondary flows inside wavy duct. And also friction factors are about two times greater than those of the smooth circular duct.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.375-380
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• 2006

Embedded Duct Ventilation System in Ondol is embedded supply duct in Ondol. This system allows heat up outside air to inside temperature with out using heat exchanger and electric heating coiling in winter season. In this research, we measured temperature of inside and surface of Ondol, supply duct, and supply air temperature incorporate embedded duct ventilation system in Ondol in model house($110m^2$) & one room($23m^2$)

• 설비공학논문집
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• 제15권11호
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• pp.910-917
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• 2003

Fluid flow in a rectangular duct for 90$^{\circ}$ bend elbow with the ratio of 1.5 between its curvature radius and width is measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between measured and computed velocity profiles in the duct. Reynolds numbers for the comparison are 11,643, 19,746 and 24,260. From the comparison, computation of principal velocity components in the duct predicts the experimental data somewhat satisfactorily even though those of minor velocity components and turbulent kinetic energy do not match with the experimental data quite well. K-factor for the bend elbow is computed to be average 0.086 while the equivalent ASHRAE data is 0.07.

• 설비공학논문집
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• 제12권11호
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• pp.994-1003
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• 2000

Control algorithms for the absorption air conditioning system may be developed by suing dynamic models of the system. The simplified effective dynamic models, which can predict the dynamic behaviors of the system, may help the development of effective control algorithms for the system. In this study, a dynamic simulation program for the absorption air conditioning system was developed. Dynamic models for an absorption chiller, a cooling tower, an air handling unit, a boiler, a three way valve, a controller, and a duct were developed and programed. Control algorithms for the absorption chiller, the cooling tower, and the air handling unit were selected, and analyzed to show the effectiveness of dynamic models. From the simulation results, it may be concluded that this simulation program may be effectively used for the development of optimal control algorithms of the absorption air conditioning system.

• 설비공학논문집
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• 제1권3호
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• pp.252-263
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• 1989

A system of conservation equations for steady, oscillatory and pulsating duct flows are solved analytically by linearizing non-linear convective terms. Analytical solutions of velocity profiles for these flows are obtained in the form of infinite series. The experimental study for the air flow in a square duct ($40mm{\times}40mm$ and 400 mm long) is carried out to measure velocity profiles and other parameters by using a hot-wire anemometer with data acquisition and processing system. Major characteristics of the flows such as the classification of flow patterns, determination of critical Reynolds number and velocity profiles is accomplished from the experismental results.

• 설비공학논문집
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• 제23권2호
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• pp.139-146
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• 2011

The ventilation performance of a vertical exhaust duct system in the high riser public house has been evaluated by a commercial software, Fluid Flow, which solves pressure losses through the duct system including bathroom fans and a hybrid roof fan. During the numerical simulations, outdoor wind condition and stack effects in summer and winter were considered as well as the operating conditions of a basement damper and the roof fan. The results show that the bathroom ventilation in summer is the most unsatisfactory. The opening of the basement damper has a problem that the polluted air in the lower floors is exhausted to the underground parking lot, not to the rooftop. If the basement damper is closed, the exhaust flow rate in the lower floors is not sufficient due to the strong flow resistance in the long vertical duct even though the roof fan is under operating.

• 한국식품저장유통학회지
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• 제9권2호
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• pp.137-143
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• 2002

Temperature and humidity are the most important factors and should be effectively controlled for the cold storage of graius. Fuzzy logic can be easily implemented to the MIMO(Multi-Input Multi-Output) control systems. For the cold storage in grain bin, fuzzy logic was applied to an air conditioning system. The capacities of the grain bin and the air conditioner are 80 tons and 30㎾, respectively. Also, the target values of temperature and relative humidity in outlet duct of the air conditioner were 8$\^{C}$ and 75%, respectively. In order to control temperature and relative humidity of air, a damper in inlet duct was manipulated for temperature control and a heater was used for humidity control. Temperature deviation and change of temperature deviation were used as input parameters for the fuzzy system. Humidity was only considered as a load. The experimental results showed that the controlled temperature of exhausted air was maintained at 8$\pm$2$\^{C}$. Relative humidity of the air was also controlled at the target relative humidity of 50∼80%.

• 설비공학논문집
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• 제19권11호
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• pp.770-775
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• 2007

Although these days application of heat recovery ventilation and improved kitchen ventilation system came into wide use in mixed-use residential buildings and exclusive residences, there are not enough ventilation systems except the local ventilation of kitchens and rest rooms. It is very important part to regulate and distribute correct air flow rate for controlling air change rate. The purpose of this study is to investigate the application of distributor at house ventilation system by comparing a duct system with out distributor and with distributor. The results of this study are as follows. (1) When using distributor though the size of duct diameter is reduced rapidly, the pressure loss doesn't rise largely. The pressure loss without distributor is 4.08 mmAq, the pressure loss with distributor 4.10 mmAq. (2) To use distributor can reduce materials of duct and secure enough ceiling space by reducing duct diameter. (3) Diameters and air flow paths of distributor on the design stage are important part for accurate air flow rate.

• 설비공학논문집
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• 제21권10호
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• pp.545-552
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• 2009

It is common to design the duct branches where to supply the required air flow for individual room in residential apartment house. And TAB process is applied to control the designed air volume with adjusting volume dampers and/or supply diffusers after fully installing the ventilation system. This process has been resulted increasing the initial cost for the residential ventilation system because of man-hour and accessories such as volume control damper or diffuser. However it is difficult to adjust the air volume adequately in small air duct branches in residential ventilation system. The purpose of this study is to figure out the performance of Multidrop chamber coupling system for the residential ventilation system.