• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.1
• /
• pp.59-65
• /
• 2002

The application of local air circulation models in the field of air pollution research has become more and more popular with increasing demands of detailed wind data for obtaining precise information on spatial and temporal variations. However the prediction of air circulation near the surface is generally not a simple task because of intricate interactions between surface and air. Particularly in Korea, many areas are mountainous with a complicated shoreline. Because considerable errors could be introduced into the model predictions, it is necessary to confirm their feasibility by comparing model predictions with observations. In this paper, the results from the evaluation of model predictions in selected publications in Korea as well as their procedures were reviewed. Various aspects of errors in the model predictions. such as possible sources, vulnerable conditions, and reduction methods, were discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.4
• /
• pp.253-262
• /
• 1992

A numerical procedure is introduced to calculate local ventilation effectiveness using the definitions of local decay rate and local mean age. A low Reynolds number $k-{\varepsilon}$ model is implemented to calculate steady state turbulent velocity distributions, and a step-down method is used to calculate transient concentration distributions. Simulations are carried out for several different values of air change rates and several different diffuser angles in a two-dimensional model of a half scale office room. The results show that the local ventilation effectiveness within a room could vary significantly from one location to another. The nominal air change rate based on the assumption of complete mixing of room air does not provide the local ventilation effectiveness information. It is numerically proved that the local mean age distribution obtained from the transient calculation is equivalent to the steady state concentration distribution with homogeneously distributed contaminant sources.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.4
• /
• pp.512-518
• /
• 2000

A wall fuel-film flow model is developed to predict the effect of a wall-fuel-film on air-fuel ratio in an SI engine in transient conditions. Fuel redistribution in the intake port resulting from charge backflow and a simple liquid fuel behavior in the cylinder are included in this model. Liquid fuel film flow is calculated of every crank angle degree using the instantaneous air flow rate. The model is validated by comparing the calculated results and corresponding engine experiment results of a commercial 4 cylinder DOHC engine. The predicted results match well with the experimental results. To maintain the constant air-fuel ratio during transient operation. the fuel injection rate control can be obtained from the simulation result.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.7
• /
• pp.688-696
• /
• 2000

A scheme for fault detection on the subsystem level is presented. The method uses analytical redundancy and consists in generating residuals by comparing each measurement with an estimate computed from the reference models. In this study regression neural network models are used as reference models. The regression neural network is memory-based feed forward network that provides estimates of continuous variables. The simulation result demonstrated that the proposed method can effectively detect faults in an air handling unit(AHU). The results show that the regression models are accurate and reliable estimators of the highly nonlinear and complex AHU.

• Journal of ILASS-Korea
• /
• v.8 no.4
• /
• pp.24-30
• /
• 2003

This paper presents the characteristics of lifted height and flame length from non-premixed jet flames in highly preheated air to investigate the detail combustion mechanism in the gas turbine or HCCI engine, etc. Special attention was paid to the effect of preheated air temperature, oxygen concentration and fuel injection flow rate on flame length and lifted hight. By using highly preheated air, stable flames were formed even in low oxygen concentration condition. The lifted height increased with decreasing preheated air temperature, where the flame length showed opposed phenomena. The flamelet model, which is thought to have very thin flamelet, is difficult to applicable to the present flame conditions which is formed In low oxygen concentration in highly preheated air.

• Proceedings of the SAREK Conference
• /
• 2005.11a
• /
• pp.480-485
• /
• 2005

In the respect of the environmental protection viewpoint, the $CO_2$ may be regarded as one of the most attractive alternative refrigerants for an automotive air-conditioning system. Control methods for a $CO_2$ system should be newly developed, because properties of $CO_2$ are different compared with those of classical refrigerants. Especially, high-side pressure of a $CO_2$ system should be controlled for the effective operation of the system. In this study, intelligent control algorithms for a $CO_2$ system were developed ‘ These are a high-side pressure control algorithm and an indoor air temperature control algorithm. These algorithms were analysised by using dynamic models of a $CO_2$ system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.2
• /
• pp.184-190
• /
• 2002

This study was undertaken to judge the quality of air-tightened exhibition cases. Exhibition cases for artifacts display provide a layer of protection between the interior conditions in the exhibition case and the exterior fluctuating conditions of temperature and relative humidity in the museum environment. An infiltration model of the exhibition case was developed through the experimental measurements to calculate the number of air change rate in the exhibition case undergoing in a day, which represents the airtightness of the exhibition case. The results indicate that tighter exhibition cases provide greater protection against the fluctuating conditions of temperature and humidity outside. When the temperature and humi- dity difference between the exhibition case in-and-out is larger, some absorption materials should be applied to control the environmental conditions in the exhibition case.

• Journal of Industrial Technology
• /
• v.14
• /
• pp.141-153
• /
• 1994

폴리이미드 분리막에 의한 $CCl_2F_2/Air$ 혼합물의 분리특성에 관하여 온도, 압력, stage cut(${\theta}$), 주입기체 조성등의 영향을 규명하였다. 본 연구의 실험범위 내에서 이상분리인자(ideal separation factor)는 600-200이었으며, glassy polymer인 폴리이미드 분리막에 대하여 투과도가 높은 air의 투과도는 $CCl_2F_2$ (dichlorodifluoromethane, CFC-12)에 의하여 상당히 감소함을 알 수 있었다. 그러나, 폴리이미드 분리막에 대한 투과도가 낮은 $CCl_2F_2$의 투과도는 air에 의하여 투과도가 증가하였다. 또한, 수학적 모델에 의한 예측치가 실험치와 잘 일치됨을 알 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.12
• /
• pp.1288-1296
• /
• 2001

A scheme for on-line fault detection and diagnosis of an air-handling unit is presented. The fault detection scheme uses residuals which are generated by comparing each measurement with analytical redundancies computed from the reference models. In this paper, artificial neural networks (ANNs) are used to estimate analytical redundancy and to classify faults. The Lebenburg-Marquardt algorithm is used to train feed forward ANNs that provide estimates of continuous states and diagnosis results. The simulation result demonstrated that the ANNs can effectively detect and diagnose faults in the highly non-linear and complex HVAC systems.

• Journal of Environmental Health Sciences
• /
• v.22 no.4
• /
• pp.122-128
• /
• 1996

Many computer programs have been developed for meteorological and air quality simulation. Many of the model the U.S. EPA recommends are available as. part of UNAMAP. HIWAY-II can be used to estimate the concentrations of nonreactive pollutants from highway traffic. As a result, It was found that distribution of concentration wind speed was 1 m/s to 5 m/s were diminished to about 1/2. In our study, we measured air pollutants(CO), temperature and humidity to evaluate. Meteorological parameter were influenced by not only wind direction but also vertical.