• Solar Energy
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• v.18 no.3
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• pp.107-112
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• 1998

Basic design of a solar driven absorption cooling machine(SDACM) with a cooling capacity of 5 USRT was carried out. The SDACM is a single effect cycle driven by low temperature hot water from solar collectors. The SDACM design data were calculated by the steady state simulation program which was developed in this study The variation of COP and cooling capacity of the SDACM were investigated at different off-design conditions. Both the cooling capacity and the system COP were improved with decreasing cooling water temperature. If hot water temperature was increased, the cooling capacity was improved but the system COP was found to be decreased. The decrease of the system COP were basically caused by increased thermal loads in the system components.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.266-271
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• 2001

In this study, the performance of the simultaneous heating & cooling water making system using R134a was investigated by simulation. The most important effect upon heating COP was intermediate pressure depending on input water temperature. With the input water temperature of $10^{\circ}C\;and\;20^{\circ}C$, optimum intermediate pressure were 923 and 1040kPa, respectively. At that optimum intermediate pressure, the maximum heating COP of the system operated between $0^{\circ}C$ evaporating temperature and $70^{\circ}C$ condensing temperature were 4.15 and 3.83. With installation of the subcoolers in high or low pressure section, the system COP was increased by reducing the refrigerant mass flow rate. Under the optimum pressure and $10^{\circ}C$ input water temperature, it was found that heating COP was maximized when the low-subcooler and high-subcooler capacity rate were taken by 14% and 13%, respectively.

• International journal of advanced smart convergence
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• v.12 no.2
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• pp.182-186
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• 2023

In this study, we measured the power and temperature of the floating horizontal solar cell in a coastal lagoon and compared with those of ground solar cell and water platform solar cell. Because the bottom surface of the floating horizontal solar cell was contacting the water, cooling effect was expected stronger than other cells. As a result of the measurement, the power of floating horizontal cell was 11.7% higher than that of the ground cell and 15% higher than that of the water platform cell. During the measurement, it was observed that water waves were continuously flowed on the top surface of floating horizontal cell by the wind, and it could be assumed that the cooling effect occurred not only on the bottom surface of the cell but also on the top surface. In order to analyze the cooling effect and power increasing of the horizontal cell in the wave situation, we measured power and temperature of the cell while generating artificial waves in a laboratory equipped with Zenon lamp as a solar simulator. At the height of thewater surface, the power of the cell with waves was 3.7% higherthan without waves and temperature was 4.6℃ lower. At 1 cm and 2 cm below the watersurface, power of the cell with waves was decreased by 14% and 11% than without waves while temperature was same . At 3 cm below the water surface, there was no effect of waves.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.194.2-194.2
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• 2011

Heating and cooling performance has been analyzed for the water-source heat pump system using raw water from Daechung reservoir. During heating operation from March to May, water temperature is not good condition for a heat source due to the higher atmospheric temperature. Avearged heating load ratio is only 14.3%, and the averaged unit COP and system COP are estimated to be 2.46 and 2.15 respectively. The COP is affected considerably by the water temperature, and the unit COP is increased from 2.16 at $5^{\circ}C$ to 2.95 at $11^{\circ}C$. Cooling performance is analyzed with the measured data from June to August. During cooling operation, raw water has lower temperature by 4. $5^{\circ}C{\sim}4.7^{\circ}C$ than the atmosphere. The load ratio is 39.2%, and the averaged unit COP and system COP are estimated to be 7.25 and 6.13 respectively. The heating COP is affected by the load ratio rather than water temperature. The COP is increased for 20%~40% load ratio, while is decreased for 40%~60% load ratio. It is estimated that the compressor operation combination for 3 (two constant speed and one inverter) compressors is changed for the load ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1051-1056
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• 2014

After hot rolling, a high-temperature steel plate with a temperature higher than $800^{\circ}C$ is rapidly cooled by multiple circular water jets. In this cooling process, because the temperature of the steel plate is much higher than the boiling point of the cooling water, film-boiling heat transfer occurs and a very thin steam layer forms between the plate surface and the cooling water. The steam layer acts as a thermal resistance that prevents heat transfer between the cooling water and the steel plate. In addition to the film-boiling heat transfer, complex physical phenomena such as the free-surface flow of residual water that accumulated on the material and the material's high-speed motion also occur in the cooling process. In this study, the simultaneous cooling process of the upper and lower sides of a running hot steel strip is investigated using a three-dimensional numerical model and the cooling performances and characteristics of the upper-side cooling and lower-side cooling are compared.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.193-197
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• 2010

Water cooling ducts are installed in the exhaust diffuser for high altitude tests of rocket engine to protect diffuser from high-temperature combustion gas. The mass flow rate and pressure of cooling water is designed to prevent boiling of cooling water in the ducts. Therefore, the estimation of maximum temperature of duct wall is important parameter in design of cooling system, especially pressure of cooling water. The method for predicting maximum temperatures of duct walls with variation of coolant flow rates was derived theoretically.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.269-274
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• 1999

Various method have been developed for mass concrete structures to reduce the temperature increase of concrete mass due to exothermic hydration reactions of concrete compounds and thereby to avoid thermal cracks. One of the methods widely acceptable for practical use is pipe cooling, in which cooling is achieved by circulating cold water through thin-wall steel pipes embedded in the concrete. A numerical simulation was performed to investigate the effectiveness of pipe cooling. A three-dimensional finite element method was proposed to analyse the transient three-dimensional heat transfer between the hardening concrete and the cooling water in pipe and to predict the stress development during the curing process. The effects of the cement type and content and the environment were taken into consideration by the heat generation rate and the boundary conditions, respectively. In order to test the validity of the numerical simulation, a model RC structure with pipe cooling was constructed and the time-dependent temperature and stress distributions within the structure as well as the variation of the temperature of cooling water along the pipe were measured. The results of the simulation agreed well the experimental measurements. The results of this study have important implications for the optimal design of the cooling pipe layout and for the estimation of thermal stress in order to eliminate thermal cracks.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.164-169
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• 2001

There is a chilled ceiling panel which carries out the air conditioning by radiation and convection between the room and cold ceiling panel surface. In order to verify heat transfer characteristics between them in cooling system with radiant chilled ceiling panel, analytical and experimental studies were performed for various design and operating parameters such as tube space and diameter, inlet water temperature, mass flow rate, cooling load, and so on. In this study, we found that the tube space and inlet water temperature were more important elements than the tube diameter and water flow rate for the performance of radiant chilled ceiling panel. The cooling capacity of the radiant chilled ceiling panel had the maximum value of $65W/m^{2}$ because the highest cooling capacity was limited by the condensation on the panel surface. The results of comparison between numerical analysis and experiment showed a resonable agreement qualitatively, especially for low cooling capacity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.203-210
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• 2004

This paper describes the potential advantages in applying evaporative cooling to air-cooled condensers. The cooling characteristics of an air-cooled condenser with its surface fully covered with thin water film are investigated and compared with that of an air-cooled condenser with usual dry surface. By applying the evaporative cooling, the cooling performance of the condenser is shown to improve enormously. When the outdoor air is 35$^{\circ}C$ and 40% in relative humidity, the condensing temperature of the refrigerant is decreased by 2$0^{\circ}C$. Even when the incoming air is fully saturated with water vapor, the evaporation from the wet surface occurs to cause a decrease in the condensing temperature by 1$0^{\circ}C$. The main reason for this improvement is assessed as the addition of an efficient cooling mechanism which is the water evaporation resulting in latent heat absorption.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.974-981
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• 2007

Seoul Metro has operated the air cooling equipment established in a machine room of a station building to improve our services focused on our customers who use Seoul Metro during the summer season. However, a new set of problems has arisen with the cooling tower to support a heat exchange of cooling water. One of them is loss of efficiency in the air conditioner. The leading cause of this problem is that we use an underground type of the cooling tower. As the machine room of a station building is located in the underground of inner city because of the nature of the subway, it is difficult to establish the cooling tower on the ground. The underground structure of the No. $1{\sim}4$ subway line is unsuitable for the location requirements of the underground type of the one because it has a limited space to set up the air cooling equipment, for example, the cooling tower and a ventilating opening. As a result of such an unfavorable condition, the cooling tower doesn't work efficiently and the warmth of cooling water because of insufficiency of a heat exchange and a refrigerator's technical obstacle such as a high-temperature and a high-pressure has arisen. Accordingly, the efficiency of the air conditioning is getting lower and lower. Another problem is too wasteful with water. Each station uses the water over 30 tons every day with waterworks to replenish the cooling tower such as a evaporation, a scattering and a distribution of water. Nevertheless, the more an air conditioner increase, the more the use of water supply increase. For this reason, we can't help wasting an enormous amount of water and discharging the congelation of a low temperature(about $15^{\circ}C$) occurred in a heat exchanger inside an air conditioner. The purpose of this study is to analyze the utility of congealing water to improve efficiency of the air cooling equipment and save energy as a supplementary water for the cooling tower.