• Journal of Advanced Marine Engineering and Technology
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• 제40권8호
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• pp.686-691
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• 2016

This paper employs numerical tools to obtain an optimal thermal design of a heat exchanger with plain-fins. This heat exchanger is located at the condensing section of a crevice-type heat pipe. The plain-fins in the heat exchanger are radically mounted to two tubes in the condensing section. To obtain the optimal design parameters, a computational fluid dynamics technique is introduced and applied to different placement configurations in a system module. Owing to its effects on the heat pipe performance, the temperature difference between the tube surfaces and ambient air is investigated in detail. A greater heat dissipation rate occurs when the plain-fin offsets change from 2 to 3 mm. When this temperature difference is ${\Delta}T=70^{\circ}C$, the upper part of the plain-fins undergoes an accumulation of heat. At below $70^{\circ}C$, the dissipation of heat is accepted. A rectangular plain-fin geometry with varying widths and heights does not have a significant impact on the heat dissipation through-out the overall system. In addition, the temperature distributions between different plain-fin pitches show an equal profile even with different fin pitches.

• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.8-13
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• 2009

Feasibilities of the application of a micro gas turbine cogeneration system to a large size hospital building are studied by estimating energy demands and supplies. The energy demand for electricity is estimated by surveying and sorting the consumption records for various equipment and devices. The cooling heating, and hot water demands are further refined with TRNSYS and ESP-r to generate load profiles for the subsequent operation simulations. The operation of the suggested cogeneration system in conjunction with the load data is simulated for a time span of a year to predict energy consumption and gain profile. The simulation revealed that the thermal efficiency of the gas turbine is about 30% and it supplies 60% of the electricity required by the building. The recovered heat can meet 56% of total heating load and 67% of cooling, and the combined efficiency reaches up to 70%.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.172-176
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• 2009

We developed a program, "CogenSim-$\mu$," to simulate the operation of micro-combined heat and power (${\mu}CHP$) system. The CogenSim-$\mu$ can reflect the variation of energy efficiency by handling the real-time loads (heat and power) fluctuation. The result obtained using this program was compared with the real operation of 30 kWe gas engine driven ${\mu}CHP$. It was found that the CogenSim-$\mu$ could predict the amount of generated-power, recovered-heat and consumed-fuel with the error less than 3%, and heat and power efficiency with the error less than 4%. The CogenSim-$\mu$ reconstructed the profile of on-off cycle, which represented the operation of a facility, with more than 93% accuracy. The CogenSim-$\mu$ can reflect the effects of various factors such as size of thermal storage tank, desired temperature of reservoir water, natural frequency of generator, etc. As a result, the CogenSim-$\mu$ can be used to optimize the ${\mu}CHP$ operation.

• 설비공학논문집
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• 제26권3호
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• pp.122-129
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• 2014

In order to extract shaft power from thermal energy in a R134a Rankine cycle as waste heat recovery system of a passenger car, a scroll expander has been designed. Algebraic spiral is adopted as the base curve for scroll wrap profile in the compact scroll design. About 19% reduction in scroll diameter is accomplished when compared to the conventional involute scroll. Performance analysis on the designed scroll expander shows that the expander efficiency is 85.5% at the vehicle speed of 120 km/hr and it decreases to 67.2% at 60 km/hr, provided that the scroll clearance is kept at 10 ${\mu}m$. The expander can produce shaft power equivalent to about 13~14% of the driving power within the speed range of 60~120 km/hr.

• 품질경영학회지
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• 제40권3호
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• pp.286-294
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• 2012

Purpose: In this study, we propose the ESS process model which, in order to improve reliability of electronic equipment, can be referenced in both development and production phases. Methods: ESS guidelines such as MIL handbooks or private sector ESS guidelines are used for devising the proposed ESS model. Especially, proposed model is customized by using those references in order to be optimized in the domestic development and production phases. Results: ESS-related-requirements which is specified in the Technical Data Package(TDP) for the area of guided missile systems are analyzed. Current status of the requirement and screening strength are analyzed for those systems to show what kind of weak points should be improved. Conclusion: A ESS guideline which is applicable to the domestic weapon acquisition environment is proposed. As such, the necessity and detail guidelines of the proposed model are explained.

• 한국전산유체공학회지
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• 제22권1호
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• pp.67-80
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• 2017

The high-speed bypass effect on the heat exchanger performance has been investigated numerically. The plate-fin type heat exchanger was modeled using two-dimensional porous approximation for the fin region. Governing equations of mass, momentum, and energy equations for compressible turbulent flow were solved using ideal-gas assumption for the air flow. Various bypass-channel height were considered for Mach numbers ranging 0.25-0.65. Due to the existence of the fin in the bypass channel, the main flow tends to turn into the core region of the channel, which results in the distorted velocity profile downstream of the fin region. The boundary layer thickness, displacement thickness, and the momentum thickness showed the variation of mass flow through the fin region. The mass flow variation along the fin region was also shown for various bypass heights and Mach numbers. The volumetric entropy generation was used to assess the loss mechanism inside the bypass duct and the fin region. Finally, the correlations of the friction factor and the Colburn j-factor are summarized.

• 대한기계학회논문집B
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• 제21권4호
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• pp.518-524
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• 1997

Experimental studies on combustion phenomena within a porous ceramic burner are reported. Main interest of the present work is to investigate fundamental flame behaviors and their effects on the burner operation. Due to high thermal capacity of the porous ceramic materials, the response of flame to burning condition changes is slow and thus to have a stabilized flame is quite difficult and takes much time. It is found that the temperature profile obtained at downstream of the flame zone is not much sensitive to the movement of flame and the speed of flame movement is less than 0.1 mm/sec for the conditions tested. With the premixed LPG/air flame imbedded within the porous ceramic burner, stable combustion regions and unstable combustion regions leading to blowoff or flashback phenomena are observed and mapped on flow velocity versus equivalence ratio diagram. For the development of burner operation technique which is more practical and safe, intermittent burning technique, where the fuel or/and air is supplied to the burner intermittently, is proposed as one of the flame control methods for the porous ceramic burner and tested in this study. Through the experiment, it is realized that the proposed method is acceptable in respect to burner performance and give much flexibility in the operation of porous ceramic burner.

• Asian-Australasian Journal of Animal Sciences
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• 제17권1호
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• pp.131-136
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• 2004

The effects of salt concentration and heating conditions on the thermal gelation properties of surimi produced from mechanically deboned chicken meat (MDCM) were investigated. Chicken surimi was manufactured by washing (MDCM: 0.5% NaCl=1:4), standing, straining and centrifuging. The fat, water-soluble protein and heme pigment in the MDCM were removed by increasing washing cycles. The compressive force of the chicken surimi increased as the concentration of salt was increased from 0% to 5%. Total gel strength of the surimi measured by texture profile analysis showed a maximum in the range 3-5% NaCl. Microstructural analysis showed that the unfolding network structure of the surimi gel began to appear at NaCl concentrations>2%. The optimum heating condition for gelation was $90^{\circ}C$ for 40 min as this resulted in maximum values for measures of gel strength including compressive force, hardness, fracturability, adhesiveness, springiness, gumminess, chewiness and resilience. Chicken surimi gel formed by cooking at a heating rate of $1^{\circ}C/min$ to $90^{\circ}C$ showed better a texture than gels produced at $1.85^{\circ}C/min$. Our result show that a lower rate of heating improves chicken surimi gelation.

• 한국전산유체공학회지
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• 제18권1호
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• pp.77-82
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• 2013

The error in measuring temperature profiles by thermocouple inside boundary layer mostly comes from the conduction heat transfer of the thermocouple. The error is not negligible when the conductivity of the thermocouple is very high. In this study, the effect of conduction heat transfer of the thermocouple on the temperature profile inside boundary layer was examined by considering both free-stream velocity and a thermocouple position. The conduction error of an E-type thermocouple was investigated by numerical analysis of three-dimensional conjugate heat transfer for various velocity profiles of boundary layer and thermocouple positions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.154-161
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• 2000

As a mass flow controller is widely used in many manufacturing processes for controlling a mass flow rate of gas with accuracy of 1%, several investigators have tried to describe the heat transfer phenomena in a sensor tube of an MFC. They suggested a few analytic solutions and numerical models based on simple assumptions, which are physically unrealistic. In the present work, the heat transfer phenomena in the sensor tube of the MFC are studied by using both experimental and numerical methods. The numerical model is introduced to estimate the temperature profile in the sensor tube as well as in the gas stream. In the numerical model, the conjugate heat transfer problem comprising the tube wall and the gas stream is analyzed to fully understand the heat transfer interaction between the sensor tube and the fluid stream using a single domain approach. This numerical model is further verified by experimental investigation. In order to describe the transport of heat energy in both the flow region and the sensor tube, the Nusselt number at the interface between the tube wall and the gas stream as well as heatlines is presented from the numerical solution.