• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.135-139
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• 2002

In this study, the experimental open-tube and close-tube thermoacoustic apparatuses were built. In order to determine the optimum length of resonant tube and the optimum length of stack, the resonant characteristics of thermoacoustic apparatuses were investigated, The length of resonant tube varies from 400mm to 850mm. The experimental frequency varies from 100Hz to 1000Hz. In case of the second and third harmonics, the maximum temperature difference of open-tube thermoacoustic apparatus is 53$^{\circ}C$ (resonator length: 400mm) and the maximum temperature difference of closed-tube thermoacoustic apparatus is 51$^{\circ}C$ (resonator length: 500mm). In the open-tube thermoacoustic apparatus, the peak efficiency point is about 2%, 55%, 69% in the resonant tube and in the closed-tube thermoacoustic apparatus, the peak efficiency point is about 2%, 41%, 50% in the resonant tube.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.28-32
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• 2003

Miniature inertance pulse tube refrigerator was designed and fabricated to provide optimal performance with 10W compressor. An adiabatic model was used to design an inertance pulse tube refrigerator. Among the various design parameters which should be optimized, pulse tube length and inertance tube length were considered. PdV work and various losses were calculated for various pulse tube and inertance tube length. Experiments were carried out for different pulse tube length and inertance tube length. It was shown that the experimental results were similar to the calculated results. The reason why the quantitative optimal point exists is explained.

• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.646-652
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• 2009

Experimental results for performance characteristics of HCs refrigerant R-1270 and HCFC refrigerant R-22 during refrigeration system using capillary tube are presented. The system consists of compressor, condenser, capillary tube, evaporator and peripheral devices. Length and diameter of capillary tube are varied for this investigation. The refrigerant mass flow increased as the diameter of capillary tube increased and the length of capillary tube decreased. A refrigeration capacity and compressor work of R-1270 in same length and diameter of capillary tube showed the higher values than those of R-22. A coefficient of performance showed the highest value when the length and diameter of capillary tube are 105 cm and 1.8 mm in this experimental conditions.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.129-134
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• 2002

In this study, the experimental open-tube and close-tube thermoacoustic apparatuses were constructed. In order to determine the optimum length of resonant tube, frequency and the optimum length of stack, the resonant characteristics of thermoacoustic apparatuses were investigated, The length of resonant tube varies from 400mm to 850 mm. The experimental frequency varies from 100 Hz to 1000 Hz. In case of first harmonic, the maximum temperature difference of the open-tube thermoacoustic apparatus is 41$^{\circ}C$)resonator length: 500 mm), and the maximum temperature difference of the close-tube thermoacoustic apparatus is 42$^{\circ}C$ (resonator length : 850 mm).

• 대한기계학회논문집B
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• 제30권8호
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• pp.749-755
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• 2006

To improve pool boiling heat transfer in an vertical annulus with closed bottoms, the length of an outer tube has been changed from 0.2m to 0.6m. For the test, a heated tube of 19.1mm diameter and water at atmospheric pressure have been used. Annular conditions are made using glass tubes fabricated around the heated tube. The gap size of the annulus is 3.65mm. To elucidate effects of the outer tube length on heat transfer results of the annulus are compared with the data of a single unrestricted tube and the annulus with wider gap size of 6.35mm. Throughout the tests much higher heat transfer coefficients are observed for the annulus of 3.65mm gap size comparing to the other two cases. The change in the outer tube length results in much variation in heat transfer coefficients. Moreover, with shortening the length of outer tube the possibility of the CHF occurrence can be removed.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.53-58
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• 2004

A Miniature inertance pulse tube refrigerator was designed and tested with a 10 W compressor. Erperiments were carried out for different pulse tube length and inertance tube length. An adiabatic model which considered the pressure drop in the regenerator was used to analyze the performance of the pulse tube refrigerator. Among various design parameters which should be optimized, the pulse tube length and the inertance tube length were optimized. PdV work and several different loss mechanism were included in the analysis to simulate more accurately the physical phenomena in the pulse tube refrigerator. Nevertheless, the simulation program could not completely predict the porformance of the refrigerator. The possible reason for the difference of the optimal point between the simulation and the experiment was explained.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.189-192
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• 2002

In this study, The experimental open-tube-type and close-tube-type thermoacoustic refrigerator were constructed. The resonant characteristics of a thermoacoustic refrigerator were investigated. In order to determine the optimum resonant tube length and frequency, We changed the length of resonant tube from 400mm to 850mm and the frequency from 100Hz to 1000Hz. In case of first harmonic, the temperature difference of open-tube-type (1/4 wave) refrigerator was $41^{\circ}C$(resonator length :500mm). The temperature difference of close-tube-type (1/2 wave) refrigerator was $43^{\circ}C$(resonator length :850mm). In this experiments, the experimental 1/2 wave refrigerator is slightly cooler than the experimental l/4 wave refrigerator.

• 대한기계학회논문집B
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• 제36권8호
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• pp.775-782
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• 2012

수직으로 설치된 하부폐쇄 환상공간 내부의 풀비등 열전달 메카니즘을 알기 위하여 환상공간의 튜브 길이를 0.3m와 0.6m 사이에서 변경하였다. 실험을 위해 0.2m의 가열 길이를 갖는 직경 19.1mm인 스테인리스강 튜브와 대기압 상태 하에 있는 물을 사용하였다. 외부 튜브 길이가 열전달에 미치는 영향을 분명하게 살펴보기 위해 환상공간에 대한 결과를 환상공간이 없는 단일튜브에 대한 결과와 서로 비교하였다. 동일 열유속에서 외부튜브 길이의 증가는 틈새간격이 3.5mm인 경우에는 열전달계수의 증가하지만 틈새간격이 15.5mm인 경우에는 열전달계수가 감소하였다. 이러한 경향의 주된 원인은 액체교란의 차이로서 설명된다.

• 한국태양에너지학회 논문집
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• 제23권2호
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• pp.43-49
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• 2003

The thermal performance of the glass evacuated tube solar collector is numerically investigated. The glass evacuated tube solar collector consists of a two-layed glass tube, a copper tube, and the working fluid. The length and the diameter of the glass tube are 1,200mm and 38mm, respectively. The diameter, thickness, and length of the copper tube and the flow rate of air are considered as the important design and operating parameters of the collector. The effect of these parameters on the thermal performance of the collector are investigated. The results show that as the diameter, the thickness, and the length of the copper tube increase and the flow rate of the air decreases, the thermal performance and the outlet mean temperature increase.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1888-1891
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• 2003

In this paper, we proposed a new method to control the length of carbon nano tube in the single CNT probe. A single CNT probe was composed of a tungsten tip made by the electrochemical etching and carbon nano tube which was grown by CVD and prepared through the sonication. The two components were attached with the carbon tape. Since the length of CNT can not be controlled during the manufacturing, the post process is needed to shorten the CNT. In this paper, we proposed the method of electrochemical process. The process was done under the optical microscope and the results were checked by SEM. The diameter of the carbon nano tube used in this paper was about 130nm because the above process had to be done with the optical microscope. Using the method proposed in this paper, we can control the length of the nano tube tip.