• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.195-203
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• 2000

The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Fluid from the spent jets is constrained to flow out of the system in one direction. Therefore, the spent fluid makes a crossflow in the confined space. The present study investigates effects of jet-orifice-plate to impingement-surface spacing and jet Reynolds number. The spanwise- and overall-averaged heat/mass transfer coefficients are obtained by numerical integrating the local heat transfer coefficients. The local maximum heat/mass transfer coefficients move further in the downstream direction due to the increase of crossflow velocity. At the mid-way between adjacent jets, the heat/mass transfer coefficients have a small peak owing to the collision of the adjacent wall jets and are affected strongly by the crossflow. The effect of the crossflow occurs strongly at the small orifice-to-impingement surface distance.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.605-610
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• 2002

The absorption of benzene in nonpolar solution was studied in a laboratory-scale of bubble column varying of gas flow rates and gas-to-liquid ratios. A bubble column had a 0.8∼l$\times$10$\^$-3/ m$^3$ total volume (height 1500 mm, diameter 50 mm). Solution analysis was performed by GC-FID and GC-MSD. The objectives of this research were to select the best absorption fluid and to evaluate the mass transfer characteristics under specific conditions of each absorption. The results of this research were follow as: First, the heat transfer fluid is more efficient than the other nonpolar solution in removing VOC. Second, The benzene removal efficiency improved according to an increasing rate of gas flow. Also, volumetric mass transfer rate of column can be enhanced by increasing gas flow rate. Finally, the relation of gas flow rates, liquid amount, and volumetric mass transfer coefficient was obtained as follows. K$\_$y/a: 0.5906(V$\_$g//L)$\^$0.7611/ The following correlation of mass transfer coefficient and efficiency was proposed. v= 0.06078 K$\_$y/a$\^$0.2444/.

• International Journal of Highway Engineering
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• v.17 no.5
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• pp.1-10
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• 2015

PURPOSES : A finite difference model considering snow melting process on porous asphalt pavement was derived on the basis of heat transfer and mass transfer theories. The derived model can be applied to predict the region where black-ice develops, as well as to predict temperature profile of pavement systems where a de-icing system is installed. In addition, the model can be used to determined the minimum energy required to melt the ice formed on the pavement. METHODS : The snow on the porous asphalt pavement, whose porosity must be considered in thermal analysis, is divided into several layers such as dry snow layer, saturated snow layer, water+pavement surface, pavement surface, and sublayer. The mass balance and heat balance equations are derived to describe conductive, convective, radiative, and latent transfer of heat and mass in each layer. The finite differential method is used to implement the derived equations, boundary conditions, and the testing method to determine the thermal properties are suggested for each layer. RESULTS: The finite differential equations that describe the icing and deicing on pavements are derived, and we have presented them in our work. The framework to develop a temperature-forecasting model is successfully created. CONCLUSIONS : We conclude by successfully creating framework for the finite difference model based on the heat and mass transfer theories. To complete implementation, laboratory tests required to be performed.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.42-52
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• 2012

Direct Numerical Simulation(DNS) of turbulent mass transfer in fully developed turbulent pipe flow has been performed to study the effect of wall boundary conditions on the concentration fields at $Re_{\tau}$=180 based on friction velocity and pipe radius. Fully developed turbulent pipe flows for Sc=0.71 are studied with two different wall boundary conditions, namely, constant mass flux and constant wall concentration. The mean concentration profiles and turbulent mass fluxes obtained from the present DNS are in good agreement with the previous numerical results currently available. To investigate the effects of wall boundary condition on the turbulent mass transfer, the mean concentration profile, root-mean-square of concentration fluctuation, turbulent mass fluxes and higher-order statistics(Skewness and Flatness factor) are compared for the two cases. Furthermore, the budgets of turbulent mass fluxes and concentration variance were computed and analyzed to elucidate the effects of wall boundary conditions on the turbulent mass transfer.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.161-167
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• 2009

The liquid solar air conditioning system is introduced as an alternative solution to control air condition and to save electrical energy consumption. The heat and mass transfer performances of dehumidifier/regenerator in liquid solar air conditioning system are influenced by air and desiccant condition. The application of this system, the thermal energy from the sun and inlet air are unable to control, but operation parameter of other components such as pump, fan and sensible cooling unit are able to control. The equilibrium point of heat and mass transfer are the liquid desiccant and inlet air conditions, where, the heat and mass are not transferred between the liquid desiccant and vapor air. By knowing equilibrium point of heat and mass transfer, the suitable optimal desiccant conditions for certain air condition are funded. This present experiment study is investigated the equilibrium point heat and mass transfer in various air and desiccant temperature. The benefit of equilibrium point heat and mass transfer will be helpful in choose and design proper component to optimize electrical energy consumption.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.215-223
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• 1999

Evaporation heat transfer coefficient and pressure loss were measured for three different micro-fin tubes and a smooth tube. The experiments were carried out with R-22 over a wide range of vapor Quality, mass velocity and heat flux. Heat transfer coefficient of the tube with slightly modified fin shape was found to be higher than that of the commercial reference tube by 60%. The improvement of heat transfer has been achieved without noticeable increase of pressure loss. Heat transfer coefficient was increased with increasing quality, refrigerant mass flux, and heat flux. However, the effect of refrigerant mass flux and heat flux was not great. Heat transfer coefficient at bottom was lower than that at top of the tube in low quality region, which suggested the existence of stratification in the micro-fin tube. Pressure drop was linearly increased with increasing refrigerant quality and was proportional to about square of mass flux.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.47-49
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• 2012

Massive binary stars lose mass by two mechanisms: jet-driven mass loss during periods of active mass transfer and by wind-driven mass loss. Beta Lyrae is an eclipsing, semi-detached binary whose state of active mass transfer provides a unique opportunity to study how the evolution of binary systems is affected by jet-driven mass loss. Roche lobe overflow from the primary star feeds the thick accretion disk which almost completely obscures the mass-gaining star. A hot spot predicted to be on the edge of the accretion disk may be the source of beta Lyrae's bipolar outflows. I present results from spectropolarimetric data taken with the University of Wisconsin's Half-Wave Spectropolarimeter and the Flower and Cook Observatory's photoelastic modulating polarimeter instrument which have implications for our current understanding of the system's disk geometry. Using broadband polarimetric analysis, I derive new information about the structure of the disk and the presence and location of a hot spot. These results place constraints on the geometrical distribution of material in beta Lyrae and can help quantify the amount of mass lost from massive interacting binary systems during phases of mass transfer and jet-driven mass loss.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.382-389
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• 2001

In the present study, local heat transfer rates for co-rotating disks with two modified hubs having ventilation holes are investigated for Rossby number of 0.04, 0.1 and 0.35 to evaluate the influence of incoming flows through hub holes. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients on the rotating disks using the heat and mass transfer analogy. Flow field measurements are conducted using Laser Doppler Anemometry (LDA) and numerical calculations are performed simultaneously to analyze the flow patterns induced by the disk rotation. The basic flow structure in a cavity between co-rotating disks consists of three regions; the solid-body rotating inner region, the outer region with turbulence vortices and the shroud boundary layer region. The heat/mass transfer. rates on the co-rotating disks are very low near the hub due to the solid-body rotation and those increase rapidly in the outer region due to turbulence mixing. The modified hubs with ventilation holes enhances significantly the heat/mass transfer rates on the region near the hub. The results also show that the heat transfer of Hub-2 is superior to that of Hub-1, but Hub-1 is more profitable for destructing the solid-body rotating inner region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.910-920
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• 2004

The heat/mass transfer characteristics in a rotating two-pass duct with and without rib turbulators are investigated in the present study. The square duct has a hydraulic diameter ($D_h$) of 26.7 mm, and $1.5\;mm{\times}1.5\;mm$ square $90^{\circ}$-rib turbulators are attached on the leading and trailing walls. The pitch-to-rib height ratio (p/e) is 10. The Reynolds number based on the hydraulic diameter is kept constant at 10,000 to exclude the Reynolds effect, and the rotation number is varied from 0.0 to 0.20. In the smooth duct, the curvature of the $180^{\circ}$-turn produces Dean vortices that enhance heat/mass transfer in the post-turn region. When rib turbulators are installed, heat/mass transfer is augmented 2.5 times higher than that of the smooth duct since the main flow is turbulated by reattaching and separating in the vicinity of the duct surfaces. The duct rotation results in heat/mass transfer discrepancy so that Sherwood number ratios are higher on the trailing surface in the first-pass and on the leading surface in the second-pass. In the turning region, Dean vortices shown in the stationary case transform into one large asymmetric vortex cell, and subsequent heat/mass transfer characteristics also change. As the rotation number increases, the heat/mass transfer discrepancy enlarges.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.150-158
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• 2002

Local heat/mass transfer and friction loss in a square duct roughened with various types of continuous and discrete rib turbulators are investigated. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the reduction of thermally weak regions and the promotion of the uniformity of heat/mass transfer distributions as well as the ;augmentation of average heat/mass transfer. The rib-to-rib pitch to the rib height ratio (p/e) of 8 and the rib angles of 90° and 60° are selected with e/D$\_$h/=0.08. The vortical structure of the secondary flows induced by the parallel angled arrays are quite distinct from that induced by the cross angled arrays. This distinction influences on heat/mass transfer and friction loss in all the tested cases. The gap flows of the discrete ribs reduce the strength of the secondary flows but promote local turbulence and flow mixing. Consequently, the angled discrete ribs with the small gaps provide a more uniform heat/mass transfer distribution sustaining high average heat/mass transfer.