• Journal of Environmental Science International
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• v.20 no.7
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• pp.819-828
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• 2011

This research was done to clarify the cooling effect of water particles generated from a fountain. This effect is a one way to control the heat island effect of big cities. The result of this research was drawn by setting the jets of water in a certain height, and then studying the diffusion of water particles, which is affected by the size of the particles and the wind speed, and the cooling effect caused by the diffusion. 1) When a diameter of a water drop was 500 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 75 to 190m, and the water vapor spread over 175 to 440 m. As a result, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 130 to 330m around the water fountain. 2) When a diameter of a water drop was 750 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 65 to 150 m, and the water vapor spread over 160 to 405 m. Moreover, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 110 to 275 m around the water fountain. 3) After studying on the relationship between the diameter of water drop and the wind speed, and the diffusion of water particles and the range of the atmosphere that was cooled, a result could be drawn from the research that the smaller the diameter of the water vapor gets and the faster the wind speed becomes, the wider the water particles diffuse and the cooler the atmosphere around the fountain becomes. 4) This research further extrapolates that when the ordinary water(tap water, water from river and stream) is used in a fountain, the cooling effect of the air near the fountain can be approached similarly. If the seawater is used in a fountain, there is to be more to concern not only on cooling effect on the air, but also on other effects on surrounding environment generated by the salt in seawater.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.483-493
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• 2006

A model for a pressure drop of water vapor flow across tube banks in a horizontal tube absorber of an absorption chiller/heater using LiBr solution as a working fluid has been developed based on a commercial 20RT(70kW) absorption chiller/heater. The numerical results show that the characteristic of the pressure drop in the shell side of the horizontal tube absorber is completely different from that in a conventional shell and tube heat exchanger. Especially, solution film thickness has significant influence on the vapor pressure drop in the horizontal tube absorber. In addition, the effects by the tube diameters, the longitudinal pitch to diameter ratio, and Reynolds number of the vapor flow, on the vapor pressure drop have been studied to evaluate the compactness of tube absorber. It was found that the vapor pressure drop decreases as tube diameter increases, the longitudinal pitch to diameter ratio increases, and Reynolds number of the vapor flow decreases. A comparison of the present study results with well-established experimental and numerical results showed a good overall agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.538-546
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• 1989

Effect of liquid viscosity was studied experimentally on the drop size distributions of the liquid sprays from swirl atomizers. Glycerine-Water mixtures were used as test fluids for the experiments. Drop sizes of the liquid sprays were measured with the light scattering method. The concept of the standard deviation was introduced to represent the degree of uniformity of the drop size distributions. Experimental results show that the spray drops become coarser and less uniform with the liquid of higher viscosity. The effect of viscosity on the Sauter mean diameter and the standard deviation appeared to be more significant with the lower injection pressure. It was also confirmed that the Sauter mean diameter increases with the increase of the liquid viscosity and with the decrease of the injection pressure.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1225-1230
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• 2004

In this paper, the pressure drops were investigated according to the sintered porous wick structure in loop heat pipe(LHP) by theoretical analysis. LHP has the wick only in evaporator for the circulation of working fluid, so utilizes porous wick structure which pore diameter is very small for large capillary force. This paper investigates the effects of different parameters on the pressure drops of the LHP such as particle diameter of sintered porous wick, wick porosity, vapor line diameter, thickness of wick and heating capacity. Working fluid is water and the material of sintered porous wick is copper. According to the these different parameters, capillary pressure, pressure drop in wick were analized by theoretical design method of LHP.

• Journal of Fisheries and Marine Sciences Education
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• v.6 no.1
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• pp.58-76
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• 1994

Heat transfer and pressure drop measurements are made on low integral-fin tubes in turbulent water flow condition. The integral-fin tubes investigated in this paper are nominally 19mm in diameter. Eight tubes have been used with trapezoidally shaped integral-fins having fin density from 748 to 1654 fpm and 10, 30 grooves. Plain tube having same diameter as finned tube is also tested for comparison. Experiments are carried out using R-11 as working fluid. The refrigerant condensates at a saturation state of $30^{\circ}C$ on the outside tube surface cooled by coolant. The amount of noncondensable gases present in the test loop is reduced to a negligible value by repeated purging. For a given heat input to the boiler and given cooling water flow rate, all test data are taken on steady state. The heat transfer loop is used for testing single long tubes and cooling water is pumped from a storage tank through filters and flowmeters to the horizontal test section where it is heated by steam condensing on the outside of the tube. The pressure drop across the test section is measured by means of pressure gauge and manometer. Each tube tested is cleaned with sodium dichromate pickling solution and well rinsed with water prior to installation in the test section. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, heat transfer of finned tube is enhanced up to 4 times as that of a plain tube at constant Reynolds number and up to 2 times at constant pumping power. 2. Friction factors are up to 1.6~2.1 times those of plain tube. 3. At a given Reynolds number, Nusselt number decrease with increasing pitch to diameter. 4. The constant pumping power ratio for low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.295-305
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• 2010

Role of the perforated pipe is to drain the water with equal pressure and velocity through the holes of perforated pipe. The perforated pipe is being used in many processes of water treatment system, however, the design parameter of perforated pipe is not standardized in korea. In this study, we have found the design parameter of perforated pipe in the water treatment system using the Computational Fluid Dynamics (CFD). The uniformity of outflow from the perforated pipe is directly affected according to area ratio(gross area of holes/surface area of the perforated pipe). In other words, the uniformity of outflow is improved as area ratio is smaller. Also, at the same area ratio, the uniformity of outflow is improved as number of holes is increase. Specially, in case of the two holes per length of pipe diameter(2/D) shows the most uniformity of outflow and the best hydraulic with the smaller pressure drop. The uniformity of outflow is aggravated and the pressure drop of pipe is decrease as length of pipe is longer. In case of that pipe length is 10m and above, the pressure drop decreased about 30% when diameter ratio is 40% with 0.2% of area ratio by comparison with 0.1% of area ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1293-1300
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• 2011

The configurations of the evaporator and condenser of a water chiller can be determined from the trade-off between the heat transfer area, which is related to the capital cost and the pressure drop, which is associated with the operational cost. In this study, the design of the water chiller focused on minimizing the water pressure drop of both condenser and evaporator for given cooling capacity and requirements. Commercial enhanced tubes were employed to simulate real-life conditions. The results of the present analysis were compared with those obtained by HTRI software for verifying them. The results indicated that a reduction in the water pressure drop, which is associated with the short length of a tube, can be effected by decreasing the number of tube passes and increasing the number of tubes and the tube diameter. However, using a large number of tubes with smaller diameters can reduce the capital cost because the tubes are short. The reduction of the capital cost is due to the fact that a small-diameter tube has low internal thermal resistance and hence contributes to a decrease in the overall thermal resistance per unit length.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.546-552
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• 2006

In this paper we report fluid flow characteristics of $Al_2O_3$ nanoparicles suspended in water. Especially, the effects of volume fraction with the range of 0.01% to 0.3% and tube diameter with $310{\mu}m$ to 1.735mm on the pressure drop and the effective viscosity of $Al_2O_3$ nanoparicles suspended in water are experimentally investigated. It is shown that the effective viscosity of water-based $Al_2O_3$ nanofluids with 0.1 Vol.% through a circular tube of 1.024mm diameter is increased to about 6%. The effective viscosity from experimental results is compared with that from Einstein model. With the comparison, we show that Einstein model for determining the effective viscosity of nanofluids is not applicable to water-based $Al_2O_3$ nanofluids.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.463-473
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• 2006

The effect of tube diameter on heat and mass transfer characteristics of absorber in absorption chiller/heater using LiBr solution as a working fluid has been investigated by both of numerical and experimental study to develop a high performance and compact absorber. The diameter of the heat exchanger tube inside absorber was changed from 15.88mm to 12.70mm and 9.52mm. In numerical study a model of vapor pressure drop inside tube absorber based on a commercial 20RT absorption chiller/heater was performed. The effect of tube diameter, longitudinal pitch, vapor Reynolds number, longitudinal pitch to diameter ratio on vapor pressure drop across the heat exchanger tube banks inside absorber have been investigated and found that vapor pressure drop decreases as tube diameter increases, longitudinal pitch increases, vapor Reynolds number decreases and longitudinal pitch to diameter ratio increases. In experimental study, a system includes a tube absorber, a generator, solution distribution system and cooling water system was set up. The experimental results shown that the overall heat transfer coefficient, mass transfer coefficient. Nusselt number and Sherwood number increase as solution flow rate increases. In both of study cases, the heat and mass transfer performance increases as tube diameter decreases. Among three different tube diameters the smallest tube diameter 9.52mm has highest heat and mass transfer performance.

• Journal of information and communication convergence engineering
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• v.4 no.1
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• pp.46-52
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• 2006

Precipitation measurement with ground-based radar needs an information of the raindrop size distribution (RSD) characteristics. A 10-month dataset was collected in tropical Atlantic coastal zone of northeastern Brazil where the weather radar was installed. The number of drop was mainly recorded in 300 - 500 drop $mm^{-3}$, of which the maximum was registered around 1.1 mm drop diameter.