• Title/Summary/Keyword: Pre-cooling

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Dynamic Simulation of a Dedicated Outdoor Air-conditioning System (외기 전용 공조기의 동특성 시뮬레이션)

  • Kim, Jung-Min;Kim, Young-Il;Chung, Kwang-Seop;Park, Seung-Tae
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.322-327
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    • 2007
  • Dedicated outdoor air-conditioning(DOA) system that utilizes pre-cooling and desiccant dehumidification can be superior to conventional cooling and reheating system with respect to energy consumption and indoor thermal comfort. In this work, simulation has been conducted to study various factors that affect the performance of DOA. Dynamic simulation shows the transient variation of temperature and humidity as the on/off control logic is imposed. Exit humidity of process air and flow rate are varied to study the effect on exit temperature of process air, dehumidification quantity, required regeneration temperature and exit humidity of regeneration air. For an outdoor air condition of $28.5^{\circ}C$ temperature, 16 g/kg humidity ratio and 2000 cmh flow rate, the dehumidification efficiency is increased by 4.6% as the flow rate is doubled.

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Evaluation on the Characteristics of Liquefied Natural Gas as a Fuel of Liquid Rocket Engine

  • Namkoung, Hyuck-joon;Han, Poong-Gyoo;Kim, Kyoung-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.148-154
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    • 2004
  • As a rocket propellent of hydrocarbon fuels, the characteristics of liquefied natural gas was evaluated with the viewpoint of the constituents and content, the cooling performance as a coolant, and characteristic velocity and specific impulse as parameters of the engine performance. Content of methane was a principal factor to determine the characteristics as a rocket propellant and more than 90 % of it was needed as a fuel and coolant in the regenerative cooled liquid rocket engine. Some constituents of the liquefied natural gas can be frozen by the pre-cooling of the pipe lines, therefore they can be a factor disturbing the normal working of engine. In case the content of methane is around 90% in the liquefied natural gas, a normalized stoichiometric O/F mixture ratio of 0.75 is suggested for a nominal operation condition to get the maximum specific impulse and characteristic velocity.

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A Study on the Integrated Prefab Building Materials Depending on the Cooling Type of PV Module Backside (태양전지모듈 후면의 냉각조건에 따른 조립식 건축자재와 일체화에 관한 연구)

  • Yi, So-Mi;Lee, Yong-Ho
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.06a
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    • pp.138-141
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    • 2006
  • The application of photovoltaics into building as integrated building components has been paid more attention worldwide. Photovoltaics or solar electric modules are solid state devices, directly converting solar radiation into electricity; the process does not require fuel and any moving parts, and produce no pollutants. And the prefab building method is very effective because the pre-manufactured building components is simply assembled to making up buildings in the construction fields especially the sandwich panel. So, the purpose of this research is to integrated prefab building materials depending on the cooling type of PV modules. It is concluded that the prediction of BIPV system's performance should be based on the more accurate PV module temperature. From the basis of these results on the correlation of temperature and irradiation were obtained.

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Development of a Plate-type Megasonic with Cooling Pins for Sliced Ingot Cleaning

  • Hyunse Kim;Euisu Lim
    • Journal of the Semiconductor & Display Technology
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    • v.22 no.3
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    • pp.21-27
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    • 2023
  • In this article, a plate-type megasonic cleaning system with cooling pins is proposed for the sliced ingot, which is a raw material of silicon (Si) wafers. The megasonic system is operated with a lead zirconate titanate (PZT) actuator, which has high electric resistance, thus when it is being operated, it dissipates much heat. So this article proposes a megasonic system with cooling pins. In the design process, finite element analysis was performed and the results were used for the design of the waveguide. The frequency with the maximum impedance value was 998 kHz, which agreed well with the measured value of 997 kHz with 0.1 % error. Based on the results, the 1 MHz waveguide was fabricated. Acoustic pressures were measured, and analyzed. Finally, cleaning tests were performed, and 90 % particle removal efficiency (PRE) was achieved over 10 W power. These results imply that the developed 1 MHz megasonic will effectively clean sliced ingot wafer surfaces.

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Pre-swirl Nozzle Geometry Optimization to Increase Discharge Coefficient Using CFD Analysis (Pre-swirl system의 유량계수 향상을 위한 Pre-swirl nozzle의 형상 최적화 전산해석 연구)

  • Lee, Hyungyu;Lee, Jungsoo;Kim, Donghwa;Cho, Jinsoo
    • The KSFM Journal of Fluid Machinery
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    • v.20 no.1
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    • pp.21-28
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    • 2017
  • Optimization process of pre-swirl nozzle geometry was conducted to improve the discharge coefficient of pre-swirl system by using CFD. The optimization of pre-swirl nozzle shape covered the converging angle and the location of the converging nozzle. Optimization process included Optimal Latin Hyper-cube Design method to get the experimental points and the Kriging method to create the response surface which gives candidate points. The process was finished when the difference between the predicted value and CFD value of candidate point was less than 0.1 %. This paper compared the Reference model, Initial model which is the first model of optimization and Optimized model to study flow characteristics. Finally, the discharge coefficient of Optimized model is improved about 17 % to the Reference model.

Construction Method and Control System of the Heat of Hydration for Inchon International Airport Elevated Road Way (인천국제공항 여객터미널 전면 고가 교량 공사 시공방법 및 수화열 대책)

  • 임채만;박명웅;조용기;조선규;김은겸
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.869-881
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    • 1999
  • Inchon International Airport Elevated Road Way is located between the Passenger Terminal Building and Transportaion Center which are Inchon International Airport core construction projects. The deck of the bridge is consists of 5-span or 6-span continuous pre-stressed concrete slab. Steel form has been used to enhance the quality of texture on concrete slab. Steel form has been used to enhance the quality of texture on concrete surface, lower surface of deck slab with the two way arch has been manufactured by highly professional manner in order to get an beautiful exterior architectural looks. The prestressed concrete deck slab is mass concrete structures with a high-specified concrete strength and a varying section in the range of 0.95-2.8m thickness. Therefore high risks of thermal cracking occurrence by heat of hydration highly are expected. To resolve such problem, we adopted type 1 cement and pipe cooking method at construction site through mass concrete specimen test and 3-dimensional analysis. For Pipe cooling we used 25mm diameter stainless pipes with wrinkles. Cooling pipe with spacing 50-60cm has been installed. And continuous pipe cooling with cooling water of 15$^{\circ}C$ was conducted for 2days. In present 8 span of all 29 spans construction has been completed. No thermal cracking heat hydration has been observed yet.

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Cooling Heat Transfer Characteristics of Carbon Dioxide in a Horizontal and Helically Coiled Tube (수평관과 헬리컬 코일관내 이산화탄소의 냉각 열전달 특성)

  • Son, Chang-Hyo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.1
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    • pp.121-126
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    • 2008
  • The cooling heat transfer coefficient of $CO_2$ (R-744) in a horizontal and helically coiled tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, evaporator and gas cooler (test section). The test section consists of a horizontal stainless steel tube and hellically coiled copper tube of 4.57 and 7.75 mm. The experiments were conducted at saturation temperature of 100 to $20^{\circ}C$, and mass flux of 200 to $500kg/m^2s$. The test results showed the variation of the heat transfer coefficient tended to decrease as cooling pressure of $CO_2$ increased. The heat transfer coefficient with respect to mass flux increased as mass flux increased. The experimental results were also compared with the existing correlations for the supercritical heat transfer coefficient, which generally underpredicted the measured data. However, the experimental data showed a relatively good agreement with the correlations of Pitla et al. except for the pseudo critical temperature.

The crystalline characteristics of ZnO deposited on various cooling rates by RF sputter (RF 스퍼터링 법에 의한 ZnO 박막의 결정성과 기판의 냉각속도)

  • Park, Sung-Hyun;Lee, Neung-Hun;Ji, Seung-Han;Jeon, Seok-Hwan;Lee, Sang-Hoon;Chu, Soon-Nam
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.11a
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    • pp.257-258
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    • 2006
  • ZnO thin films were prepared by RF magnetron sputter deposition on p-Si(100) wafer with various cooling rates of substrate temperature such as the substrates were pre-heated to $400^{\circ}C$ before the deposition and then cooled down naturally or slowly to $300^{\circ}C$, $200^{\circ}C$, $100^{\circ}C$, and R.T., by the temperature controller during the deposition. The crystall me and micro-structural characteristics of the films were investigated by XRD and SEM ZnO films which cooled down naturally or slowly by temperature controller during deposition, especially the film were deposited with cooling down from $400^{\circ}C$ to $200^{\circ}C$ slowly, showed the most outstanding c-axis preferred orientation.

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Numerical Study of the Cooling Channel of the Preburner for a Small Liquid Rocket Engine (소형 액체로켓엔진용 예연소기 냉각채널 유동해석)

  • Moon, In-Sang;Shin, Kang-Chang
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.21-24
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    • 2010
  • The cooling channel of the preburner for staged combustion engines was studied. The combustion pressure of the researched preburner is about 210 bar which is very high compared with the engines of the Korean Launch Vechicle and 30 ton class liquid rocket engines developed as a pre-research program. Also, the combustion is an oxygen rich process unlike the gas generators of open cycle kerosene engines. Thus the cooling process is very important to make the preburner stable. Many configurations for the preburner were developed and numerically analyzed. As a result, the pressure loss could be reached below the target.

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