• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.88-94
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• 1998

The thermal performance of cooling towers is affected mainly by the velocity, temperature and humidity of the entering air, In this paper, the effects of these variables are experimentally investigated for both counter-flow and cross-flow cooling towers. The cooling performance is reduced by up to 50% as the relative humidity of the entering air is increased from 40% to 80%. The higher air velocity and lower coolant flow show better cooling performance. The coolant loss rates in the present experimental conditions are in the range of 0.4 to 1.7%

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.92-97
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• 2009

The performance of cooling fan is affected by many peripheral parts, such as radiator, condenser, engine block and etc. Higher power has been requested in more confined automobile engine room. Thus, cooling performance becomes very important to remove the heat generated from the automobile engine more efficiently. In this paper, the performance of cooling fan including effects of engine block is investigated by using a fan tester based on the ASHRAE and the AMCA standards. A flow rate - gap distance curves and a flow rate - engine block constant curves are obtained from this study.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.3
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• pp.19-30
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• 2022

In this study, comparative analysis of energy performance in Taebaek city, a test area, by applying hydrothermal, geothermal source and hybrid heat pump system to office, school and smart farms with different internal heat loads. The conclusion is as follows. In the load characteristics by use of buildings, it was found that office had a large cooling load compared to heating load, school had a large heating load compared to cooling load, and smart farm had only cooling load year-round. Performance analysis of the heat pump system in office shows that the cooling COP of the hydrothermal source is 5.12% and the heating COP is 3.22% lower based on the geothermal source, the cooling COP of the hybrid is 0.41% higher, and the heating COP is the difference in performance appeared sparsely. The performance analysis of the heat pump system in school showed that the cooling COP of the hydrothermal source was 10.44% and the heating COP 3.22% lower based on the geothermal source, and the performance difference between the hybrid cooling and heating COP was insignificant. Heat pump system performance analysis in smart farm only occurred with cooling load. Based on geothermal sources, the cooling COP of the hydrothermal source was 46% and the cooling COP of the hybrid was 19.65%, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.2
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• pp.64-69
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• 2008

Electronic and telecommunication industries are constantly striving towards miniaturization of electronic devices. Miniaturization of chips creates extra space on PCBs that can be populated with additional components, which decreases the heat transfer surface area and generates very high heat flux. Even though an air-cooling technology for telecommunication equipment has been developed in accordance with rapid growth in electrical industry, it is confronted with the limitation of cooling capacity due to the rapid increase of heat density. In this study, liquid-cooling heat exchangers were designed and tested by varying geometry and operating conditions. In addition, air-cooling heat exchangers were tested to provide performance data for the comparison with the liquid-cooling heat exchangers. The liquid-cooling heat exchangers had twelve rectangular channels with different flow paths of 1, 2, and 12. Silicon rubber heaters were used to control the heat load to the heat exchangers. Heat input ranged from 293 to 800W, and inlet temperatures of working fluid varied from 15 to $27^{\circ}C$. The heat transfer coefficients were strongly affected by flow conditions. All liquid-cooling heat exchangers showed higher cooling performance than the air-cooling heat exchanger. The heat exchanger with 2-paths could provide more controllability on the maximum temperature than the others.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2438-2443
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• 2007

In order to guarantee the performance of electronic products. It is needed to improve the cooling performance of heat sink. So this paper has been made to investigate the cooling performance for the aluminum heat sink using pulsating heat pipe(PHP). The pulsating heat pipe was used as a heat spreader. Working fluid was R-22. Heater (50 mm ${\times}$ 50 mm ${\times}$ 3mm) was attached to heat sink and it generated 30W, 60W, 80W, 100W. Heat sink was tested for forced convection with 1${\sim}$4m/s of inlet air velocity. And both type heat sinks were carried out by using CFD simulation. This study showed that pulsating heat pipe can be a good tool to improve cooling performance of heat sink.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.714-721
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• 2006

In evaporative cooling applications, the evaporation water is supplied usually sufficiently larger than the amount evaporated to enlarge contact surface between the water and the air. Especially in indirect evaporative coolers, however, if the evaporation water flow rate is excessively large, the evaporative cooling effect is not used for heat absorption from the hot fluid but spent to the sensible cooling of the evaporation water itself. This would result in a decrease in the cooling performance of the indirect evaporative cooler. In this study, the effects of the evaporation water flow rate on the cooling performance are investigated theoretically. The cooling process in an indirect evaporative cooler is modeled into a set of linear differential equations and solved to obtain the exact solutions to the temperatures of the hot fluid, the moist air, and the evaporation water. Based on the exact solutions, it is analyzed how much the cooling performance is affected by the evaporation water flow rate. The results show that the decrease in the cooling effectiveness is substantial even for a small flow rate of the evaporation water and the relative decrease is more serious for a high-performance evaporative cooler.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.1
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• pp.7-16
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• 2016

This paper presents the measurement and analysis results for the cooling performance of ground-coupled heat pump (GCHP) system using a cooling tower as a supplemental heat rejector. In order to demonstrate the performance of the hybrid approach, we installed the monitoring equipments including sensors for measuring temperature and power consumption, and measured operation parameters from May 1 to October 30, 2014. The results showed that the entering source temperature of brine returning from the ground heat exchanger was in a range of design target temperature. Leaving load temperatures to building showed an average value of $11.4^{\circ}C$ for cooling season. From the analysis, the daily performance factor (PF) of geothermal heat pumps ranged from 4.4 to 5.2, while the daily PF of hybrid GCHP system varied from 3.0 to 4.0 over the entire cooling season.

• International Journal of Fluid Machinery and Systems
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• v.6 no.1
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• pp.25-32
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• 2013

Data centers have been built with spread of cloud computing. Further, electric power consumption of it is growing rapidly. High power cooling small-sized fans; high pressure and large flow rate small-sized fan, are used for servers in the data centers and there is a strong demand to increase power of it because of increase of quantity of heat from the servers. Contra-rotating rotors have been adopted for some of high power cooling fans to meet the demand for high power. There is a limitation of space for servers and geometrical restriction for cooling fans because spokes to support fan motors, electrical power cables and so on should be installed in the cooling fans. It is important to clarify complicated internal flow condition and influence of a geometric shape of the cooling fans on performance to achieve high performance of the cooling fans. In the present paper, the performance and the flow condition of the high power contra-rotating small-sized axial fan with a 40mm square casing are shown by experimental and numerical results. Furthermore, influence of the geometrical shape of the small-sized cooling fan on the internal flow condition is clarified and design guideline to improve the performance is discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.6
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• pp.454-462
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• 2008

Since operating conditions are significantly different for heating and cooling mode operations in a $CO_2$ heat pump system, it is difficult to optimize the performance of the $CO_2$ cycle. In addition, the performance of a $CO_2$ heat pump is very sensitive to outdoor temperature and gascooler pressure. In this study, the cooling and heating performances of a variable speed $CO_2$ heat pump with a twin-rotary compressor were measured and analyzed with the variations of EEV opening and compressor frequency. As a result, the cooling and heating COPs were 2.3 and 3.0, respectively, when the EEV opening was 22%. When the optimal EEV openings for heating and cooling were 28% and 16%, the cooling and heating COPs increased by 3.3% and 3.9%, respectively, over the COPs at the EEV opening of 22%. Beside, the heating performance was more sensitive to EEV opening than the cooling performance. As the compressor speed decreased by 5 Hz, the cooling COP increased by 2%, while the heating COP decreased by 8%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.6
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• pp.44-49
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• 2022

The improvement in the battery performance and life using a battery thermal management system directly affects the improvement in the performance, life, and energy efficiency of electric vehicles. Therefore, this study numerically analyzed the heat exchange processes between the coolant inside the cooling plate channel and the heat generated by the battery. The cooling performance was analyzed based on the average temperature, temperature uniformity, and the maximum and minimum temperature differences of the battery. A performance difference existed depending on the coolant inlet temperature but showed the same tendency of cooling performance according to the shape of each plate's channel. Type 1 showed the best results in terms of battery temperature uniformity, which is the most important measure of battery performance; Type 2 showed the best results in terms of the average temperature of the battery; and Type 3 showed the best results in terms of the maximum and minimum temperature differences of the battery compared with that of the other cooling plates.