• Agricultural and Biosystems Engineering
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• v.4 no.2
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• pp.58-65
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• 2003

An understanding of the cooling requirements of horticultural commodities begins with adequate knowledge of their biological responses. All fresh horticultural products are living organisms, carrying on the many biological processes that are essential to the maintenance of life. The pre-cooling is essential technique for the construction of cold chain system, which is necessary to maintain marketing quality of fresh produces during the transportation and distribution. The purpose of this study is to develop the pressure cooling tunnel using conveyer for the reduction of labor and improvement of pre-cooling efficiency. Performance of developed facility was tested for the strawberries, tomatoes and Chinese cabbages. Cooling ratio as a result of pre-cooling efficiency was 1.57, 1.56 and 1.32 for strawberries, tomatoes, and Chinese cabbages respectively. Cooling ratio decreased with increasing the distance of heat conduction from surface to center. The cooling ratio of Chinese cabbages was lower than that of fruit because of its head and leaf. In aspect of cooling uniformity, there was no significant difference of final temperature among inlet, outlet and middle layers of cold air in fresh produces. After pre-cooling treatment, quality changes were measured for the weight loss, Vit. C content, and titratable acidity. The quality of pre-cooling treatment was better than that of non-treatment and was kept on well during long-term storage.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2017-2022
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• 2008

The crude oil pump system is the equipment for transporting crude oil and it consists of 3 major components, a motor and an impeller which discharge underground crude oil, a pipestack that transmits the cooling oil and power, and a cooling oil unit & junction box that provides cooling oil and electric power. When considering the system characteristics that it has to be installed at a depth of deeper than 100 m, a design technology for the efficient control of the heat occurring at a conductor and motor is necessary and it is the essential factor for ensuring system durability. In this paper, therefore, cooling oil flow has been calculated to satisfy the limit value of the system temperature by analyzing heat flow considering the related losses such as loss of conductor, contact resistor loss at the conductor connection, and operation loss of motor. And the operation temperature has been set up based on the temperature of crude oil and the heat of motor and conductor. Also, a design for cooling of crude oil pump system has been proposed by calculating the operation pressure loss and selecting the capacity of a cooling oil pump and a heat exchanger.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.71-78
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• 2002

All modem, aerospace gas turbines must operate with hot stage gas temperature several hundreds of degrees hotter than the melting temperatures of the materials used in their construction. Complicated cooling schemes need to be employed in the combustor walls and In the high pressure turbine stages. Internal passages are cast or machined into the hot sections of aero-gas turbine engines and air from the compressor is used for cooling. In many cases, the cooling system is engineered to utilize jets of high velocity air, which impinge on the internal surfaces of the components. They are divided by Impinging cooling method and Vortex cooling method. Specially, Research of new cooling system(Vortex cooling method) that overcome inefficiency of film cooling and limitation of space. The focus of new cooling system that improve greatly cooling efficiency using quantity's cooling air which is less is set in surface heat transfer elevation. Therefore, In this study, the numerical analysis have been performed for characteristic of flow and thermal in the swirl chamber and compared with the flow field measurement by LDV. especially, for understanding of high heat transfer efficiency in vicinity of wall. we considered flow structure and mechanism of vortex and heat transfer characteristic in variation of Reynolds number.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.119-124
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• 2000

The 3-stage centrifugal compressor is used in order to measure the noise spectra of compressor, and analyze the results. Two cases are investigated for compressor noise components. Case I includes total system such as compressor, inter-cooler, motor, and Case II excludes cooling system. BPF tonal noise is important in compressor, and cooling system including inter-cooler contributes to broadband noise. Also, motor, gear box, and motor cooling fan are the second contributions to total compressor noise. Centrifugal compressor flow-field is calculated using two-dimensional grid and Navier-Stokes equations. Static pressure increases, and total pressure decreases, as air passes through the compressor components.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.476-485
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• 1999

In order to evaluate the gravity-injection capability to maintain core cooling after a loss-of-shutdown-cooling event during shutdown operation, the plant conditions of the Yong Gwang Units 3&4 were reviewed. The six cases of possible gravity-injection paths from the refueling water tank (RWT) were identified and the thermal-hydraulic analyses were performed using the RELAP5/MOD3.2 code. The core cooling capability was significantly dependent on the gravity-injection path, the RCS opening, and the injection rate. In the cases with the pressurizer manway opening higher than the RWT water level, the coolant was held up in the pressurizer and the system pressure continued increasing after gravity-injection. The gravity injection eventually stopped due to the high system pressure and the core was uncovered. In the cases with the injection path and opening on the same leg side, the core cooling was dependent on whether the water injected from the RWT passed the core region or not. However, in the cases with the injection path and opening on the different leg side, the system was well depressurized after gravity-injection and the core boiling was successfully prevented for a long-term transient. In addition, from the sensitivity study on the gravity-injection flow rate, it was found that about 54 kg/s of injection rate was required to maintain the core cooling and the core cooling could be provided for about 10.6 hours after event with that injection rate from the RWT. Those analysis results would provide useful information to operators coping with the event.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.70-76
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• 2003

An experimental study was performed to understand the heat transfer and fluid dynamic characteristics of Sub-Cooled Hybrid Condenser (SCHC), which conventional condenser and receiver dryer are integrated into. SCHC also employs a sub-cooled refrigerant passages at the end of the condenser in order to supply perfect liquid refrigerant to the expansion unit. Throughout the present study, it was found that the developed SCHC increases in the degree of sub-cooling by 10~100% compared to conventional condenser. The excessive sub-cooling has improved the cooling performance by 10%, and that leads reduction in evaporator outlet air temperature by $1.5^{\circ}C$. Also found through the study is that the refrigerant pressure drop across SCHC is fairly increased due to insertion of the desiccant cartridge in the receiver tank which is composed of zeolite, filter and supporter plate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.111-117
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• 2004

An analytical study was carried out to evaluate the regenerative cooling characteristics in the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel. As a supplementary cooling method, a radiative cooling was applied to the nozzle extension. It was found out from this work that the cooling system with the regenerative and radiation cooling only is not adaptable for the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel for the $2^{nd}$ stage of the space launch vehicle, with the viewpoint of the thermal and thermo-structural instability and the excessive pressure drop in the cooling channel.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.749-754
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• 2006

This study performed of a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water in aquafarm by about $5^{\circ}C$ from $25^{\circ}C$ or higher in this research, to replace the present water cooling system, Ive focused on a water cooling system operated by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are dependent on the vacuum pressure in the enclosed tank, and the cooling water is generated by evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8mmHg$ using a steam driven ejector with jet condenser in experiments. The obtained results are respectively ${\Delta}T=7^{\circ}C$, ${\Delta}T=5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4L/M. The obtained results are respectively ${\Delta}T=5.5^{\circ}C$, ${\Delta}T=5.5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4.5L/M.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.95-103
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• 2007

This paper presents a liquid cooling concept for heat rejection of high power electronic devices existing in notebook computers etc. The design, fabrication, and performance of the planar ECF pump and farced-liquid cooling system are summarized. The electro-conjugate fluid (ECF) is a kind of dielectric and functional fluids, which generates jet flows (ECF-jets) by applying static electric field through a pair of rod-like electrodes. The ECF-jet directly acts on the working fluid, so the proposed planar ECF pump needs no moving part, produces no vibration and noise. The planar ECF pump, consists of a pump housing and electrode substrate, achieves maximum flow rate and output pressure of $5.5\;cm^3/s$ and 7.2 kPa, respectively, at an applied voltage of 2.0 kV. The farced-liquid cooling system, constructed with the planar ECF pump, liquid-cooled heat sink and thermal test chip, removes input power up to 80 W keeping the chip surface temperature below $70\;^{\circ}C$. The experimental results demonstrate that the feasibility of forced-liquid cooling system using ECF is confirmed as an advanced cooling solution on the next-generation high power electronic devices.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.163-172
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• 2024

In this study, two different scenarios for ammonia liquefaction in the green ammonia manufacturing process were proposed, and the economic-feasibility and environmental impact of each scenario were analyzed. The two liquefaction processes involved gas-liquid separation before cooling at high pressure (high pressure cooling process) or after decompression without the gas-liquid separation (low pressure cooling process). The high-pressure cooling process requires higher capital costs due to the required installation of separation units and heat exchangers, but it offers relatively lower total utility costs of 91.03 $/hr and a reduced duty of 2.81 Gcal/hr. In contrast, although the low-pressure cooling process is simpler and cost-effective, it may encounter operational instability due to rapid pressure drops in the system. Environmental impact assessment revealed that the high-pressure cooling process is more environmentally friendly than the low-pressure cooling process, with an emission factor of 0.83 tCO₂eq less than the low-pressure cooling process, calculated based on power usage. Consequently, the outcomes of this study provide relevant scenario and a database for green ammonia synthesis process adaptable to various process conditions.