• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7138-7145
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• 2015

In this study, experiments were conducted to investigate the correspondence between the output voltage of the photoelectric sensor and the frost height under heating and defrosting capacity test condition (dry bulb temperature $2^{\circ}C$, wet bulb temperature $1^{\circ}C$) described at KS C 9306, where a real heat exchanger was used as a test rig instead of a large-scale model. A digital microscope and a photoelectric sensor unit consisting of an emitter and a transistor (receiver) were installed in the front of it. A linear correlation is proposed to predict the frost height based on 150 experimental data, approximately 54% of the measured data are consistent with the predicted frost heights within a relative deviation of ${\pm}10%$, it yields good agreement with 90% of the measured data when the frost height larger than 0.3mm with in a relative deviation of ${\pm}10%$. Compared with Xiao's correlation, the slope namely, the change of frost height in accordance with the change of output voltage is consistent within the error of 2.3%. But vertical intercept shows big difference with Xiao's correlation, because it was developed with a large scale model instead of a real heat exchanger.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.3
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• pp.262-269
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• 2019

Purpose: As the importance of breastfeeding has been reinforced, human milk is often stored for practical reasons. Therefore, we evaluated optimal storage and processing methods for human milk from a nutritional standpoint. Methods: Human milk samples were collected between June 2017 and February 2018. Also, data about maternal information were collected. Human milk was analyzed for macronutrients and caloric content. The samples were subdivided into groups for nutrient analysis. The control group (fresh milk) was not stored or processed. The other groups (9 groups) consisted of samples analyzed based on different storage temperatures (room temperature, refrigerated, frozen), defrosting methods (bottle warmer, room temperature thawing, microwave oven), and storage period (1 week, 1 month, 2 months) and compared with the control group. Results: There was no statistically significant difference in the nutrient content of human milk among the collected samples. A significant change in the content of macronutrients in milk samples was observed under storage condition at different temperatures for 1 week with subsequent thawing with bottle warmer compared to fresh milk. Under storage at $-20^{\circ}C$ for 1 week with subsequent thawing with different defrosting methods, a significant change in the content of macronutrients in milk samples was observed compared to fresh milk. After storage at $-20^{\circ}C$ for different periods and thawing with a bottle warmer, a significant change in macronutrient content in milk samples was observed compared to fresh milk regardless of the storage period. Conclusion: Unlike previous guidelines, changes in macronutrient content in milk samples were observed regardless of the method of storing and thawing. Apparently, it is proposed that mothers should feed fresh human milk to their babies without storing.

• Archives of Plastic Surgery
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• v.43 no.6
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• pp.595-598
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• 2016

The use of human vessels at the beginning of microsurgery training is highly recommended. But vessels with the appropriate length for training are not often obtained. Whether these vessels may be reused for training has not been reported. Accordingly, we harvested vessels from discarded tissues in lymph node dissection and demonstrated that vascular anastomosis training using the same human vessels several times is possible by placing the vessels in a freezer and defrosting them with hot water. Vascular walls can be stored for microsurgical training until about 4 years after harvest, as shown in the gross appearance and histologic findings of our preserved vessels. We recommend the technique presented here for the long-term reuse of human vessels for microsurgery training that closely resembles real procedures.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.234-235
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• 2005

In this experiment study, to acquire elementary data for explaining to generate frost layer in the fin - tube evaporator. the experiment condition is to supply air on 0.3m/s, 0.6m/s, 0.9m/s and inlet air temperature is 15$^{circ}C$, 20$^{circ}C$, 25$^{circ}C$ , supplied air relative humidity is 70%, 80, 90%. And brine temperature in the copper tube was kept -15$^{circ}C$ because, generally cooling temperature range is constantly -15$^{circ}C$ in the heat exchanger for air conditioning system. in conclusion, through this experiment, we did compare with frost layer and frost thickness in each condition and examine these data

• International Journal of Automotive Technology
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• v.7 no.2
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• pp.139-143
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• 2006

As an automobile tends to be high grade, the needs for more luxurious interior and comfortable HVAC system are emerged. The defrosting ability is another major factor of the performances of HVAC system. The present work is to simulate the flow and the temperature field of cabin interior during the defrost mode. The three-dimensional incompressible Navier-Stokes equations and energy equation were solved on the multi blocked grid system by the iterative time marching method and AF scheme, respectively. The present computations were validated by the comparison of the temperature field of a driven cavity and velocity field of 1/5 model scale of an automobile. Generally good agreements were obtained. By the present computation, the complicated features of flow and temperature within the automotive cabin interior could be well understood.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.1
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• pp.38-47
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• 1999

An improved one-dimensional modeling of snow melting was obtained by considering both the effect of heat capacity and the decreasing influence of porosity. Using the improved model, the effects of initial snow temperature, initial snow density and the heat flux on the snow melting were investigated. It is found that the drainage starting time is delayed and the drainage rate becomes smaller with lower initial snow temperature. ResuIts also show that the drainage starts at the same time when an initial snow density is over a certain value. Melting efficiency increases linearly with an increasing initial snow temperature. With increasing the initial density of the snow and the amount of heat supplied, the melting efficiency increases, then converges to a constant value.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.665-670
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• 2004

This paper reviews the latest studies of the expander cycle Air Turbo Ramjet engine (ATREX) conducted in JAXA. First, a system analysis including the vehicle and trajectory was conducted to optimize the engine cycle and turbo-machine configuration. We selected the precooled turbo-jet cycle for a prototype engine using the near term technologies. Second, a system ground-firing test was conducted to verify a defrosting system for the precooler. Methanol injection with its particles atomization could compensate 80 % of pressure loss caused by the frost. Thirdly, a feasibility of carbon/carbon composites for the engine components was investigated by making complex shapes such as a heat exchanger and a plug nozzle. Basic technologies on the gas leakage, the junction and bonding were also studied. The end of the paper, some basic studies such as wind tunnel tests of a new type air inlet and a plug nozzle are described.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.11a
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• pp.211-216
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• 1999

One of the problems in a refrigerator operation is the frost formation on a cold surface of the evaporator. The frost layer is formed by the sublimation of water vapor when the surface temperature is below the freezing point. This frost layer is usually porous and formed on the cold surface of the evaporator. The frost layer on the surface of a evaporator will make side effect such as thermal resistance. However, these important factors have not been used in determining the defrosting period. In this report, a prediction taking into account the change of the fin efficiency due to the growth of the frost layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.368-371
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• 2003

The humidity sensors with a stable characteristics and gas sensors operating at room temperature have been fabricated, and a multi-functional sensor system which has gas sensor, humidity sensor, temperature sensor and control circuit has been applied to the microwave oven system. For a suitable cooking state, the humidity sensors was more applicable to heating and defrosting condition than gas sensors, however, the dynamic characteristics of gas sensors were obtained in the easy burning food such as pop corn.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.113-118
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• 2011

To analyze and verify the effect of replacing thermal storage heater by a cascade cycle heat pump using midnight electricity was installed and tested at a customer's house in Wonju, Korea. The electric night storage heater is consist of 30kW electric heater and 2,700 liters of thermal storage water tank to supply hot water for warming house floor. The power for electric heater was cut off and hot water was only generated by cascade cycle heat pump. Current thermal storage water tank was not eliminated and electric heater wiring was modified. Some operation logic of the heat pump was also modified for proper operation. The required capacity of the heat pump and hot water temperature for given warming condition were estimated. The estimated capacity of heat pump was about 19kW and estimated hot water temperature for proper heating was at least $75^{\circ}C$.