• Journal of Energy Engineering
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• v.25 no.4
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• pp.30-36
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• 2016

The battery pack which is a main component of E-scooter needs the cooling system because it is the matter of battery safety in spite of the incresing of charge efficiency due to decress the internal resistence in the condition of high temperature. The purpose of this study is to analyse the effects of cooling methods which is the control of air's inlet and outlet operating timing. When each battery had large temperature deviation in the battery pack, the difference of battery's performance and efficiency were appeared. In this study, the cooling performance of battery pack has been improved by changing the operation timing of inlet and outlet fan, it improved the performance and efficiency of battery. The numerical analysis using a commercial code ANSYS CFX version 17.0 were used for the study.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.133-139
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• 2009

An analysis has been performed on the specific impulse for a liquid rocket engine of gas generator cycle. The present analysis method has been validated through the comparison of the optimal specific impulse for the 300t thrust conceptual engine against the published data. The engine specific impulse can be increased by applying film coolant decreasing the fuel pump head for regenerative cooling despite the decrease of specific impulse of the combustion chamber when the film coolant participates combustion more than the critical amount. The improved condition shows that higher combustion chamber pressure is achieved with less fuel pump head rise by additional film cooling.

• KIEAE Journal
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• v.17 no.3
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• pp.69-74
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• 2017

Purpose: The apartment complex constructed recently is composed of very various types of building, plan, and orientation etc. However, it is difficult to remark conclusively that these various types of buildings are designed energy-effectively, since it is difficult for architects to find useful energy design guideline for decision making. By the preceding study, the present condition and problem about this subject was grasped, apartment building types were examined and representative types were extracted. Method: Large apartment building complex having 1940 households, located in haengbok-dosi, sejong city, Korea is used as an example to conduct this study. Representative building types are extracted first. Then, heating and cooling load of households is analyzed. Lastly, effect of outdoor air cooling is investigated by computer simulation. Result: Results of this research are summarized as follows: 1. Besides solar gain, household layout of building, orientation, and plan have compositive effects on heating and cooling load. 2. The effect of outdoor air cooling in apartment can be improved by arranging windows of households.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.197-204
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• 2004

A design of regenerative cooling system of 30 ton level thrust combustion chamber for ground test has been performed. The 1-D design code has been validated by comparing with the heat flux of the NAL calorimeter for high chamber pressure and water-cooling performance of the ECC engine of MOBIS. The present design code has been confirmed to predict accurately the heat flux and water-cooling performance for high chamber pressure condition. The maximum hot-gas-side wall temperature is predicted to be about 720 K without thermal barrier coating and the coolant-side wall temperature is less than the coking temperature of RP-1. The coolant temperature rises nearly 100 K with thermal barrier coating when Jet-A1 is used as coolant.

• Journal of the Korean Solar Energy Society
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• v.34 no.5
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• pp.81-87
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• 2014

According to the domestic construction business will continue stagnant, many domestic construction companies are expanding their business into foreign countries. As results, building design guidelines including HVAC design for foreign countries considering the regional climate conditions are needed. Also, green building design strategies to minimize the heating and cooling load are key issue to win a contract in construction business in the world. In this study, peak heating and cooling loads were calculated for the representative cities in the world : Seoul, St. Petersburg, Singapore and Mecca. The analyzed building was a typical high-rise office building and the building envelope properties, indoor heat gain, residence and operating schedules were same in all cases. Only the weather conditions were different by cases.

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.13-19
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• 2012

Thermal performance of an impinging cooling module for 150 W class high power LEDs have been investigated numerically and experimentally. Parametric studies were performed to compare the effect of several design parameters such as nozzle number, nozzle spacing, coolant flow rate, and impinging distance. The experiments were also carried out in order to validate the numerical results and the comparison between the experimental and numerical results showed good agreement. It is found that the overall thermal resistance of impinging cooling module strongly depends on the nozzle number, nozzle spacing, flow rate, and impinging distance. This results showed the optimized operating condition when number of nozzles is 25, nozzles spacing is 4mm, flow rate is 2.70 lpm, distance between nozzles and impinging surface is 2 mm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.673-680
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• 2009

In this study, die cooling system using the nitrogen gas has been applied to hot aluminum extrusion process for refining grains and reducing of grain growth. Computational fluid dynamics(CFD) has been carried out to evaluate die cooling effect by nitrogen gas, and the results of CFD have been used to FE-simulation for the prediction of the extrudate temperature in hot extrusion process. Experimental hot extrusion has been performed to observe microstructure and to measure temperature of extrudate. The results of FE-Simulation have been good agreement with those of experiment. Finally, process condition of hot extrusion can be established to reduce grain growth of Al6061 through the experiment.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.58-66
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• 2012

The work roll surface temperature rises and falls repetitively during hot slab rolling because the work roll surface is cooled continuously by water. This study focused on Std. No. 7 to determine a cooling method which significantly reduces the tangential tensile stresses on the work roll surface of the hot slab mill at Hyundai Steel Co. in Korea. A series of finite element analyses were performed to compute the temperature distribution and the tensile stresses in the circumferential direction of the work roll. The virtual slab model was used to reduce the run time considerably by assigning a high temperature to the virtual slab. Except for the heat generated by plastic deformation, this is equivalent to the hot rolling condition that a high temperature slab (material) would experience when in contact with the work rolls. Results showed that when the virtual slab model was coupled with FE analysis, the run time was found to be reduced from 2000 hours to 70 hours. When the work roll surface cooled with a certain on-off patter of water spray, the magnitude of the tangential stresses on the work rolls were decreased by 54.1%, in comparison with those cooled by continuous water spraying. Savings of up to 83.3% in water usage are possible if the proposed water cooling method is adopted.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.267-276
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• 2000

A numerical study has been carried out to find out the optimal design condition of a solar absorption cooling system. The system was composed of solar collectors and an absorption chiller with LiBr/water The System performance with commercial single effect(SE) cycle and a new single effect/double lift(SE/DL) cycle utilizing low temperature hot water was calculated and compared. It was found that the required solar collector area grew exponentially as the overall heat loss coefficient of solar collectors increased. For instance, the required area for cooling capacity of 1 USRT was $17m^2$ if heat loss coefficient was 4 W/$m^2\;cdot\;K$. If heat loss coefficient was doubled($8\;W/m^2\;cdot\;$K), the required collector area was increased by 6 times($100m^2$) .It was also found that the SE-cycle as the heat loss coefficient of solar collectors increased. Generally, a SE/DL-cycle seems to be more advantageous than a SE-cycle if loss coefficient of solar collector is greater than 4 W/$m^2\;cdot\;K$.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.693-700
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• 2020

Direct water quenching technique can be used in hot stamping process to obtain higher cooling rate compared to that of the normal die cooling method. In the direct water quenching process, setting proper water flow rate in consideration of material thickness and the size of the area directly cooled in the component is important to ensure uniform microstructure and mechanical properties. In this study, to derive proper water flow rate conditions that can achieve uniform microstructure and mechanical properties, microstructure and hardness distribution in various water flow rate conditions are measured for 3.2 mm thick boron steel sheet. Hardness distribution is uniform under the flow condition of 1.5 L/min or higher. However, due to the lower cooling rate in that area, the lower flow conditions result in a drastic decrease in hardness in some areas in the hot-stamped part, resulting in low martensite fraction. From these results, it is found that the selection of proper water flow rate is an important factor in hot stamping with direct water quenching process to ensure uniform mechanical properties.