• 한국지하수토양환경학회지:지하수토양환경
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• 제8권2호
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• pp.1-8
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• 2003

Chlorofluorocarbons(CFCs) 조사를 위한 지하수 시료 채취 방법 중 cold-welded copper tube method(구리관법)과 flame-sealed borosilicate glass ampule method(유리앰퓰법)의 두 방법을 비교하고 검토하였다. 구리관법에 의해 채취된 시료의 CFCs 농도는 중복시료간에 재현성이 불량한 반면, 유리앰퓰법은 상대표준오차가 5％ 이내로 좋은 재현성을 보여주었다. 이것은 구리관법을 적용할 때, 관정의 출수구와 구리관의 연결의 밀봉성이 좋지 않았기 때문인 것으로 추정된다. 또한 구리관법에 의한 CFCs 농도는 전체적으로 유리앰퓰에 의한 값보다 높았으며 이러한 특징은 CFC-11이 CFC-12보다 더 두드러졌다. 구리관법의 경우에 플라스틱 관이나 관정에 설치된 출수구에 포함된 고무 패킹 등이 시료를 CFCs로 오염시켰을 것으로 평가된다. 유리앰퓰법을 적용했을 때에는 이러한 가능성을 제거하기 위해 stainless steel과 nylon 재질만을 이용하고, 시료채취장비를 관정의 주배수관에 직접 연결하였다. 인위적인 공급원에 의한 CFCs가 없을 것으로 예상되는 시료에서 유리앰퓰법에 의해 매우 낮은 수준의 CFCs농도가 측정됨으로써 이 시료채취과정의 유효성이 검증되었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권3호
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• pp.138-146
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• 2002

The phenomena of energy separation in vortex tubes was investigated experimentally to see the subsidiary effect of the conductivity of tube material and cooling conditions around the outer surface of the tube. The experiment was carried out with pyrex, stainless steel and copper tubes, and the heat transfer conditions of the tubes were with insulation, without in-sulation and water cooling modes respectively The results were obtained that the hot exit fluid temperature was highly affected by a change of conductivity of a tube when the outer surface was cooled by the water, while the working fluid through the tubes was air. How-ever, the cold exit temperature was little affected by the heat transfer modes on the outer surface of the vortex tube.

• 한국산학기술학회논문지
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• 제10권1호
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• pp.46-51
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• 2009

본 논문은 세 개의 서로 다른 관수(9, 13 그리고 19)를 가지는 원통-판형 핀 관의 원통 측에서의 열전달 성능을 실험적 방법으로 평가하였다 관외를 흐르는 오일은 관내를 흐르는 냉각수에 의해 냉각된다. 오일 쿨러의 원통-다관형 열교환기는 단일 셀 통로와 두 개의 관 통로로 구성되며, 관 내경은 8.82mm, 관 길이는 575mm이다. 오일의 질량 유량은 $1.2{\sim}6.0m^3/h$이며, 냉각수의 질량 유량은 $0.6{\sim}3.0m^3/h$이다. 실험결과 9개의 관수를 가지는 열교환기의 총합 열전달계수는 13개와 19개의 관수의 열전달계수보다 각각 약 1.8배와 2.3배 높게 나타났다.

• PNF and Movement
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• 제9권1호
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• pp.65-73
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• 2011

Background : This study was to investigate effect of hot and cold water for the hand dexterity. Methods : A total of 37 subjects having hemiplegia(men=6, women=11) and normal(men=10, women=10) were participated in this study. After both hands was soaked in the small tube for 1 minute, we measured 'making dots in circles(BOTMP)', 'lifting small objects(JHFT)', 'disk turning(MMDT)' test. Results : In the case of normal's dominant hand, there were statistically significant differences in all tests after soaked in the hot water but there were statistically significant differences in 'disk turning' test after soaked in the cold water. In the case of hemiplegia's unaffected hand, there were statistically significant differences in 'disk turning' test after soaked in the hot water but there were statistically significant differences in 'making dots in circles', 'disk turning' test after soaked in the cold water. In the case of hemiplegia's affected hand, there were statistically significant differences in 'lifting small objects', 'disk turning' test after soaked in the hot water but there were statistically significant differences in 'making dots in circles', 'disk turning' test after soaked in the cold water. Conclusion : The hot and cold water were affected in the hand dexterity. Especially, in the case of both normal and hemiplegia, there were statistically significant differences in 'disk turning' test after soaked in the cold and hot water. Therefore, We were founded that affected in gross movement than fine movement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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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.

• 동력기계공학회지
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• 제15권3호
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• pp.25-30
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• 2011

A shell-and-tube oil cooler with plate fins was suggested to improve the defect of the conventional shell-and-tube oil cooler. Experiments were conducted to evaluate the heat transfer performance on the shell side of shell-and-plate finned tube oil cooler with three different tube numbers(9, 13 and 19). Oil flowing on the shell side was cooled by cold water flowing inside the tubes. A shell-and-tube heat exchanger of an oil cooler consisted of one shell pass and two tube passes with the inner tube diameter of 8.82 mm and the tube length of 575 mm. From the experiment of shell-and-tube oil cooler, it was found that the heat transfer coefficient of oil cooler with 9 tubes, as oil flow rate was increased, was approximately 140% and 250% higher than that of 13 and 19 tubes, respectively. The heat transfer coefficient at the water flow rate of $3m^3/h$, also was 120% and 140% higher than that of 2.4 and $1.8m^3/h$, respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1270-1275
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• 2004

Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.49-55
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• 2004

This paper addresses a numerical simulation of the flow and heat transfer in a simplified model of helically coiled tube steam generator using a general purpose computational fluid dynamic analysis computer code. The steam generator model is comprised of a cylindrical shell and helically coiled tubes. A cold feed water entered the tubes is heated up, evaporates. and finally become a superheated steam with a large amount of heat transferred continuously from the hot compressed water at higher pressure flowing counter-currently through the shell side. For the calculation of tube side two-phase flow field formed by boiling, inhomogeneous two-fluid model is used. Both the internal and external turbulent flows are simulated using the standard k-e model. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. The numerical calculations are peformed for helically coiled tubes of steam generator at an integral type pressurized water reactor under normal operation. The effects of tube-side inlet flow velocity are discussed in details. The results of present numerical simulation are considered to be physically plausible based on the data and knowledge from previous experimental and numerical studies where available.

• 설비공학논문집
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• 제16권5호
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• pp.444-451
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• 2004

Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured on horizontal plain and microfin tubes. The experimental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water/glycol loop. The test section in the refrigerant loop was made of both a plain and a microfin copper tube of 6.0∼6.16 mm inside diameter and 1.0 m length. Refrigerants were cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of 4$0^{\circ}C$ with mass fluxes of 100, 200, and 300 kg/m2s. Test results showed that at similar mass flux the flow condensation HTCs of R134a were similar to those of R22 for both plain and microfin tubes. On the other hand, HTCs of R407C were lower than those of R22 by 4∼16% and 16∼42% for plain and microfin tubes respectively. And HTCs of R410A were similar to those of R22 for a plain tube but lower than those of R22 by 3∼9% for a microfin tube. Heat transfer enhancement factors of a microfin tube were 1.3∼1.9.

• 한국태양에너지학회 논문집
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• 제21권1호
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• pp.71-82
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• 2001

The heat transfer experiment in a latent heat storage tank as a solar energy storage system for the hot water supply was carried out. The latent heat storage tank was consisted of triple - tube type ; Outer shell for hot water from solar collector, PCM storage vessel in the middle of the tank and inside tube for hot water recovery. The heat storage tank has the dimension of 60 cm long and 34 cm outside diameter. Paraffin wax(m.p = 55.4C) and sodium acetate trihydrate(m.p = 58 C) were employed as the PCM this study. Experimental variables were inlet temperature and flow rate of the hot water for heat storage stage and cold water for heat recovery stage. Temperature profiles, heat transfer coefficient and the efficiency of heat storage$(Q/Q_{max})$ and heat recovery $(Q/Q_{max})$ were determined for the paraffin wax and inorganic salt respectively.