• Journal of Power System Engineering
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• v.12 no.3
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• pp.12-18
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• 2008

In the present study, the numerical simulation has been performed to investigate K-factor for temperature variation of working fluid in spray nozzle with orifice. The commercial CFD software, Fluent with the proper modeling was applied for analyzing the internal of the spray nozzle. Numerical result for K-factor at $20^{\circ}C$ agrees with the experimental result that it applied n=0.5 within about 7% error. The pressure drop inside nozzle is showed 20% passing swirler, 70% in the region between the outlet of swirler and the orifice and 10% at the outlet of orifice. As the operating pressure is increased, K-factor is decreased by effect of flow resistance at it's inlet before pass swirler. The temperature increase of working fluid reduced the flow rate according to reducing of density, and average 1.23% decrease is showed in the present research.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.134-139
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• 2003

오늘날 산업용 차량은 대부분 유압식 클러치를 채택하여 사용하고 있다 유압식 클러치는 운전자가 손쉽게 엔진으로부터 동력을 바퀴까지 전달 또는 차단하는 기능을 갖고 있기 때문이다. 차량속도에 대한 운전자의 다양한 요구는 다수의 변속 단수를 갖는 기어트레인이나 연속가변식 변속기(CVT) 원하고 있다. 그 중에 기어단을 단속하는 클러치는 엔진의 회전력과 차량 관성력을 효과적으로 연결 또는 차단을 위해 다수의 마찰판과 유체압력을 이용하여 작동된다. 유압식 클러치는 동작방식에 따라서 유체압력이 작동하면 동력을 전달하는 POSITIVE방식과 자체 탄성 스프링력에 의해서 동력을 전달하는 NEGATIVE방식이 있다. POSITIVE방식 유압식 클러치는 동력전달시 어큐뮬레이터를 이용하여 충격을 줄이고, 부하 변동시 승차감각을 향상할 수 있는 장점이 있다 TRX500 트랙터에 사용되는 유압식 클러치는 POSITIVE방식을 채택하고 있다. (중략)

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.7
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• pp.413-417
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• 2013

The organic Rankine Cycle (ORC) uses a kind of refrigerant as a working fluid that evaporates at relatively low temperature, as the Rankine Cycle uses superheated steam as the working fluid. A small scale ORC test bench was installed, and two different working fluids (R245fa and R134a) were injected into the test bench. The test bench was in operation with the two different working fluids under the same conditions. The effects against the system performance from the different working fluids were analysed, and root causes were identified. Other factors reflecting the power generation efficiency were also found. A conclusion was drawn, that R245fa makes the system perform better, than R134a.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.3
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• pp.17-23
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• 2016

A test unit for Organic Rankine Cycle (ORC) power generation system was developed and experimentally reviewed the performance of the ORC system. Two different organic fluids (R-245fa & Novec 649) were tested as working fluids for the system. System behavior was measured and analyzed along with the variables, such as temperature, pressure, rpm and shaft power. It is one of the findings that Novec 649 fluid is to be less pressurized than R-245fa in order to up to the heat source (boiler) capacity, that limits the experiment as high as 2 kW in shaft power.

• Journal of Power System Engineering
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• v.5 no.1
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• pp.27-34
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• 2001

관 외벽에 낮은 핀을 가진 수직 및 경사 열사이폰의 열전달 성능에 관한 실험적인 연구를 하였다. 관 외벽에 낮은 핀을 가진 이상밀폐 열사이폰의 열전달 성능을 비교 분석하기 위하여 동일한 규격의 평관에서도 실험적인 연구를 하였다. 작동유체는 증류수와 CFC-30을 사용하였다. 열사이폰의 경사각과 자동온도를 변화시키면서 실험한 결과 경사각의 변화에 따라 열사이폰의 열전달 성능은 큰 변화를 나타내었다. 그리고 평관으로 제작한 열사이폰보다 관 외벽에 낮은 핀관을 가진 동관으로 제작한 열사이폰의 열전달 성능이 높게 나타났다. 그리고 열사이폰의 경사각이 $20{\sim}50^{\circ}$ 범위에서 열전달 성능이 높게 나타났다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.796-802
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• 2001

The purpose of the present study is to examine the heat transfer characteristics of the U-shape heat pipe for the cooling of semiconductor in subway train. Perflouro-carbon(PFC) was used as working fluid. Temperature distribution on the surface and heat transfer coefficients were investigated according to the working fluid volume percent and heating rate. The results were as follows; Optimum volumetric percent of working fluid was from 80% to 90%, and hat transfer coefficients of evaporation and condensation were as follows, respectively. $\hbar_ie=0.37\times(\frac{P_i}{P_O})$l_c}^0.3$,$\hbar_ic-4.2(\frac{\kappa_l^3p_l^2gh_fg}{\mu_lq_c_l_c}^\frac{1}{3}

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.462-473
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• 2001

Due to the coupling between momentum and energy transport theoretical analysis of the loop performance is very complicate, therefore it is necessary that these problems be solved by experimental investigation before applying th loop thermosyphon to heat exchanger design. The evaporator and condenser of the loop thermosyphon were made of carbon-steel, and distilled water was used as working fluid in the experiments. From the experimental data correlations of heat transfer coefficient for evaporator and condenser sections were obtained. For heat fluxes in th range of 13~78kW/$m^2$, the correlation equations of heat transfer coefficients in evaporator and condenser predict the experimental behavior to within $\p$\pm$5% and\;\pm20$% respectively.

• Solar Energy
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• v.15 no.2
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• pp.39-46
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• 1995

Reported is a visual and quantitative experimental study on the two-phase flow and heat transfer characteristics of miniature two-phase closed thermosyphons with wire inserts. The visual study clearly demonstrated the two-phase flow involved in such thermosyphons. In the quantitative study, the effects on the heat transfer rate of the insert wire diameter, the ratio of heated-length to cooled length and the applied heat flux were investigated.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.3
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• pp.318-323
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• 2024

In this paper, computer modeling works have been performed for the power generation Rankine cycle using new working fluids and liquefied natural gas (LNG) cold heat. PRO/II with PROVISION released January 2023 from AVEVA company was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle. Optimal working fluid composition was determined to maximize LNG cold heat to increase power generation efficiency and net power production.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.31-32
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• 2007