• Journal of Korean Society of Forest Science
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• v.85 no.2
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• pp.210-224
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• 1996

The SLODSVAT consists of interrelated submodels that simulate : the transfer of radiation, water vapour, sensible heat, carbon dioxide and momentum in two canopy layers determined by environmental conditions and ecophysiological properties of the vegetation ; uptake and storage of water in the "root-stem-leaf" system of plants ; interception of rainfall by the canopy layers and infiltration and storage of rain water in the four soil layers. A comparison of the results of modeling experiments and field micro-climatic observations in a spruce forest(Picea abies [L].Karst) in the Soiling hills(Germany) shows, that the SLODSVAT can describe and simulate the short-term(diurnal) as well as the long-term(seasonal) variability of water vapour and sensible heat fluxes adequately to natural processes under different environmental conditions. It proves that it is possible to estimate and predict the transpiration and evapotranspiration rates for spruce forest ecosystems on the patch and landscape scales for one vegetation period, if certain meteorological, botanical and hydrological information for the structure of the atmospheric boundary layer, the canopy and the soil are available.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2261-2266
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• 2007

In this study, the numerical analysis to estimate condensation heat and mass transfer of the condenser was carried out using the PMA (porous medium approach). In the PMA, the details of tube bundle in the condenser are replaced by the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the large condenser. The pressure loss through tube bundle can be compensated by viscous and inertial momentum sink terms, which was validated numerically. Value of the pressure drop was compared to that of Butterworth correlation. Three dimensional analysis of condensation for McAllister condenser with the PMA was conducted using Fluent 6.2 and UDFs (use-defined functions). The result of condensation rate was analogous to previous results (experimental and numerical data).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.9-15
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• 2012

An effectiveness model has been developed from the approximate analytical solution of a rotary desiccant wheel. The resulting equations clearly show that the maximum air temperature and humidity differences are two independent driving forces commonly acting in the heat and mass transfer processes. Comparison with the numerical model from the preceeding study revealed that the effectiveness model could make realistic predictions roughly with 10% uncertainty. The model may be useful for the rough design and analysis of desiccant evaporative cooling systems.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.566-569
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• 2001

Researchers have invectigated nasal flow both numerically and experimentally for centuries. Experimental studies most have suffered from various limitations necessary to allow the measurements to be obtained with available equipment. Nasal airflow can be subdivided into two interrelated categories; nasal airflow resistance and heat and mass transfer between the air stream and the walls of the nasal cavity. In this study, thanks to a new method for model casting by a combination of Rapid prototyping and Solidification of clear silicone, a transparent rectangular box containing the complex nasal cavity is made for PIV experiments. The CBC PIV algorithm is used for analysis.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2004.04a
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• pp.127-139
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• 2004

The process of papermaking involves water removal on the paper machine wire, in the press section and in the dryer section. In the dryer section, liquid water in the wet web is removed mainly by evaporation. In conventional machine this is achieved by passing the web over a number of steam heated dryer rolls. A drying process of paper on a heated cylinder roll calculated based on a 1-dimensional model which concerns unsteady heat and mass transfer in the direction of paper thickness. In this study, Prediction of moisture contents average paper sheet temperature and volume fraction along a series of cylinder. Independently, developed models is compared using the same reference data. The model is implemented in CFD code, FLUENT, using user-define-function(UDFs).

• Journal of Korean Society for Atmospheric Environment
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• v.1 no.1
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• pp.43-51
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• 1985

This study is concerned with the oxidation of carbon monoxide on platinum and platinum-palladium catalysts. Catalysts were made by the impregnation method and flow reactor was used in the catalytic reaction. As for the mixed gases, carbon monoxide concentration varied from 1 to 4% and that of oxygen from 1 to 4%. $N_2$ was used as carrier gas and GHSV varied from 24, 000 $h^{-1} to 60, h^{-1}$. The temperature range was from 200 to $600^\circ$C. It was also taken into consideration that the heat and mass transfer resistance of our catalysts was negligible in the study. Experimental results showed that platinum-palladium catalyst was about 1.5-3.9% superior to platinum catalyst in conversion yield. When we used platinum-palladium catalyst, we observed that carbon monoxide oxidation was found to be 1 st order with respect to carbon monoxide concentration. Activation energy of the catalyst was 23.5 kcal/mol.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.259-267
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• 2001

The flow field in a cylinder of a 4-valve pentroof engine is studied using the KIVA-3V code. Turbulence is generated from the jet flow through valves and broken down to the small scale eddies in the compression process. It is known that the tumble effectively keeps turbulence during the compression process. In the combustion process, turbulence is known to enhance flame speed by increasing mass, momentum and heat transfer rates. The effects of the intake port angles on the flow and combustion characteristics are studied in this study. To study the effect of turbulence on the combustion process, Cantore combustion model is applied in this study.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.7-13
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• 2015

In this study, the behavior of water or nanofluid droplets impacting upon a hot surface was investigated by visualization of impacting phenomena with time-delayed photographic technique. Changing the mass ratio of nanofluid and the temperature of the heated surface, the characteristics of the spreading behavior and the diameter of spreading liquid film was compared between water and nanofluid droplets. The impacting droplet spreaded as a liquid film after impact and nanofluid droplets spreaded more widely than water droplets. After reaching the maximum diameter, water droplets shrinked more than nanofluid droplets. Based on this, the heat transfer area from a hot surface to impacting nanofluid droplets would be wider than that of impacting water droplets. Considering individual impacting droplet only, spray cooling using nanofluid would be better than using water.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.351-357
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• 2003

In absorption system, the performance of the absorber is critical the overall system performance, size, and first-cost. The objective of this paper is to provide a comprehensive review of the significant effects that researchers have made to numerically analysis model the coupled heat and mass transfer process that occur during falling-film absorption and experimental researches. This study includes experimental work in the enhancement of absorption performance, the effect of the geometry of a vertical absorber, and the effect of configuration of absorption system. This paper is used to highlight key areas which need attention such as film ans vapor hydrodynamics, especially the non-periodicity, instability, and recirculatory motion of waves in the vertical absorber case.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.335-340
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• 2005

Nonlinear and forced oscillations of supported viscous droplet were focused in the present study. The droplet has a free contact line with solid plate and inviscid fluid. Natural frequencies of a pendant droplet have been investigated experimentally by imposing the acoustic wave while the frequency is being increased at a fixed amplitude. The evaporation was observed at atmosphere pressure. The droplet was recorded throughout the entire evaporation process and transient variations of the volume was measured. The evaporation process of oscillating droplet with thermofoil has been also observed to investigate analyzing the resonance effect on the thermal characteristics of droplet. It is found that a pendant droplet shows the resonant behaviors at each mode similar to the theoretical analysis. During imposing the acoustic wave, the pendant droplet makes a rotating motion in its longitudinal axis which is a new shape oscillation mode. The evaporation rate of a pendant droplet at resonant frequency is significantly enhanced.