• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.1
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• pp.62-72
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• 2008

In this study, an analytical model has been developed to predict the build-up of heat field due to a point heat source in the presence of sharp cross-flow depth change. The model has been applied to investigate the effect of the depth change and flow pattern on the heat field. Model results show that, when there is a sharp depth change in cross-flow direction, the heat transport across the boundary of the depth change is enhanced or diminished according to the increasing or decreasing of the horizontal diffusion flux. Including residual components as well as tidal currents give rise to reduce the effect of the horizontal diffusion on the heat transport because of increasing the advection of heat.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.213-218
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• 1999

The $LiBr-H_{2}O$ absorption process on a horizontal tube has been analyzed using the numerical method which incorporates the fully elliptic Navier-Stokes equations for the momentum equations, the energy and mass-diffusion equations. On a staggered grid, the SIMPLER algorithm with the QUICK scheme is used to solve these equations along with the MAC method for the free surface tracking. With the assumption that the absorbent is linear, calculations have been made for various inlet temperature and flow-rate conditions. The detailed results of the parametric study, such as the temperature, concentration, absorption mass flux and wall heat flux distributions are presented. The self-sustained feature of the absorption process is clearly elaborated. The analyses have also been carried out for multiple tube arrangement and the results show that the absorption rate converges after a few tube rows.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.22 no.1
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• pp.1.1-15
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• 1994

The transports of the seasonal freshwater and salt from surface to 500 m depth in the tropical Atlantic Ocean are derived from the equations of the continuity and saltconservation, respectively. The freshwater transport is obtained by southward integration of the divergence of surface freshwater flux, using climatological freshwater(i. e. precipitation, evaporation, and river discharge) data. The annual freshwater transport is northward, ranging from 0 Sv near the equator to 0.3 Sv at $12^{\circ}{\;}N{\;}and{\;}20^{\circ}{\;}S$. The seasonal meridional transport amounts of freshwater range from 1.35 Sv to-0.45 Sv. The strong northward freshwater transports prevail for the intraseasonal period summer to fall. This seasonal cycle is caused by the shifts of the ITCZ as well as the changes in the local freshwater storage. Annual and seasonal salt transports are calculated from objectively analyzed historical (1900-86) salinity observations. The annual salt flux in the ocean zero, showing that the salt flux by horizontal advection balances the flux by horizontal diffusion. The salt flux due to the diffusion is northward, and has a maximum of $5{\;}{\times}{\;}10^6kg/s$ at 15oN. Seasonal transport amounts of salt range from $30{\;}{\times}{\;}10^6kg/s{\;}to{\;}-35{\;}{\times}10^6kg/s$. The direction of the seasonal salt transports is northward except for the intraseasonal period summer to fall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.670-679
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• 1996

A numerical study for vapor absorption into LiBr-H$_{2}$O solution film flowing over horizontal circular tubes has been carried out. The momentum, energy and diffusion equations, which are parabolized by the boundary- layer approximation, are solved simultaneously for various mass-flow rates and inlet conditions. The results for the velocity, temperature and concentration fields, as well as the heat and mass flux at the free surface are presented. The effects of inlet conditions, i.e., flow rate, temperature and concentration, on the absorption process are also examined and discussed.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.289-300
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• 2019

We have conducted a preliminary numerical analysis to understand the effects of double-diffusive convection on the molar flux at the crystal region during the growth of mercurous bromide ($Hg_2Br_2$) crystals in 1 g and microgravity (${\mu}g$) conditions. It was found that the total molar fluxes decay first-order exponentially with the aspect ratio (AR, transport length-to-width), $1{\leq}AR{\leq}10$. With increasing the aspect ratio of the horizontal enclosure from AR = 1 up to Ar = 10, the convection flow field shifts to the advective-diffusion mode and the flow structures become stable. Therefore, altering the aspect ratio of the enclosure allows one to control the effect of the double diffusive natural convection. Moreover, microgravity environments less than $10^{-2}g$ make the effect of double-diffusive natural convection much reduced so that the convection mode could be switched over the advective-diffusion mode.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.357-371
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• 2016

Buildings in the city acts as a cause of distorted wind direction, wind speed, causing the stagnation of the air flow. In the recent trend of climate change can not but consider the temperature rise of the urbanization. This study was aimed to analyze the thermal comfort of planetary boundary layer in different artificial constructions areas which has a direct impact on urban climate, and estimating the warming phenomena. Envi-met model was used to consider the urban structure associated with urban growth in order to precisely determine the impact of the building on the city weather condition. The analyzed values of thermal comfort index were temperature, wind speed, horizontal and vertical turbulent diffusivity. In particular, analysis of the PPD(Predicted Percentage of Dissatisfied) represents the human thermal comfort. In this study, by adjusting the arrangement and proportion of the top floor building in the urban it was found that the inflow of the fresh air and cooling can be derived low PPD. Vertical heat flux amount of the city caused by climate change was a factor to form a high potential temperature in the city and the accumulation of cold air does not appear near the surface. Based on this, to make the city effectively respond to climate change may require a long-term restructuring of urban spatial structure and density management.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.65-70
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• 2006

Transient heat transfer caused by an impulsive heating in subcooled liquid nitrogen is investigated experimentally. This study is part of out ongoing efforts directed to a stable cryogenic cooling system lot superconducting fault current limiters (SFCL). A thin heater attached by epoxy on one surface of a GFRP plate is immersed in liquid-nitrogen bath at temperatures between 77 K and 55 K. A strong heat flux up to $150W/cm^2$ is generated lot 100 ms, and the temperature of the heater sulfate is measured as a function of time. The behavior of bubbles on the heating surface can be explained by comparing the measured temperature history for vertical and two horizontal (up and down) orientations. It is concluded that the subcooling of liquid nitrogen below 70 K is very effective in suppressing bubbles, resulting in better thermal protection and faster recovery from an impulsive heat.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.347-353
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• 2017

In this study, numerical experiments were conducted to identify distribution of rising flow and flux in the East Sea of Korea, where the coastal upwelling occurs. Temperature and salinity data from CTD observations and NIFS during summer 2013 were applied to the model. Numerical experiments were carried out with different wind speed (3, 6 m/s and 9 m/s) and direction (southerly and southwesterly), which represent the most frequent in summer conditions. As a result of calculation, upwelling flow rate was found to be highest in Pohang between five coasts(Hupo, Youngduk, Pohang, Ulsan and Busan). Comparing with southerly wind conditions, the rising flow rate is about 1.5 times greater when southwesterly wind was applied. Horizontal diffusion of the upwelling area is expected to have a speed of 17~22 km/day when a 9 m/s southwesterly wind is applied. If this wind continues over one week, a cold pool will be generated by upwelling that may reach to the Ulleung area.