非定常熱源인 펄즈狀加熱法에 의한 强誘電體 Ceramic의 熱物性 測定

車京玉 明知大學校 産業技術硏究所 1992 産業技術硏究所論文集 Vol.11 No.-

The square wave pulse heating method of measuring thermophysical properties has been developed. The cylindrical of a specimen in the ferroelectricity ceramincs are heated square wave for a few second by a film heater which is placed between the plates. The resulting temperature history of the opposite surface is attached to make it hove high thermal and conductivites, is measured by pressing seperated C-A thermocouple wires against the surface. From a compassion between the measured and theoretical temperature histories, the thermal diffusivity, the specific heat and t conductivity of the specimen can be deformined automatically in a few minuted by a computer. The values of thermophysical properties were measured as a function of temperature ranging from room temperature to 1000℃ Thus, the effects of dielectricity upon themophysical properties were analyzied in detail.

有限動要素에 依한 矩形斷面 最適要素에 關한 硏究

車京玉 단국대학교 대학원 1982 學術論叢 Vol.6 No.-

This paper is studied an efficient temperature distribution and efficiency of two dimentional retctangular cross-section by finite Dynamic element and finite difference. This is achieved by employing a discretization technique based on recently devoloped concept of finite dynamics element^1)2). The result of this paper show that FEM3 is more accurate of heat transfer than FDM, and less of temperature distribution.

非定常熱源인 方形波펄즈 加熱法에 의한 세라믹 高誘電體의 熱物性値測定에 關한 硏究

車京玉,李興周,張熙碩 明知大學校 産業技術硏究所 1993 産業技術硏究所論文集 Vol.12 No.-

본 연구에서는 비정상열원인 방형과 펄즈 가열법에 의하여 고주파 특성이 우수하고 내열성이 양호하며 산업용 전자기에 필수적인 세라믹 고유전체의 MT-2, CT, SN, PZT-20, TLT-13의 열물성치를 측정하였다. 여기서 측정의 이론을 설정하고 측정의 자동화를 시도하므로 매우 짧은 시간내 시료의 열확산계수, 비열 및 열전도율을 얻을 수 있었다. 또한 시료는 실온으로부터 약 1300K 온도 범위까지 측정하였으며 높은 유전율이 열물성에 미치는 영향에 대해서 검토 및 분석을 하였다. In this paper, thermophysical properties of the ceramic high-dielectric materials such as MT-2, CT, SL, PZT-20, TLT-13 were measured by a single rectangular pulse heating method. The values of Thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature ranging from room temperature to 13--K. Thus, the effects of dielectricity upon thermophysical properties were analysed in detail.

非定常熱源加熱法에 依한 迅速熱物性値測定에 關한 硏究

車京玉,李眞 明知大學校 産業技術硏究所 1985 産業技術硏究所論文集 Vol.4 No.-

Theoretical and experimental studies were made on unsteady heat source heating method of measuring thermal properties of a small solid disk. The disk is placed in three point support and heated on the front face by thermal radiation whose intensity is varied in exponential heat pulse by a mechanical shutter. The temperature of the rear face in measured by thermocouples and recorded on oscillograph. On the basis of its data thermal diffusivity is calculated by taking the thermal ration in different times. In the present work thermophysical properties of alloy tool steels and structual carbon steels were measured in temperature 293K by this method. The thermal diffusivity and thermal conductivity in thermophysical properties of the sample material is then determined using a data reduction excursion method by computer from the recorded transient temperature versus time curve. For the improvement of accuracy in determing the thermophysical properties of sample by unsteady heat source heating method, the solution of governing heat transfer equation with the finite pulse time effect and with the heat loss on sample surface is obtained through an integral transform method. In order to computer the thermal conductivity of the standard pieces, their specific heat are measured by a differential scanning calorimeter. The thermal conductivity are calculated from the data such as specific heat, density, thermal capacity and thermal diffusivity. In the measurements it was made clear that this method can be successfully adopted to measure thermophysical properties of solid in considerabley short time and with high accuracy up to higher temperature or very lower temperature.

閃光法에 依한 特殊鋼의 熱擴散係數 側定에 關한 硏究

車京玉 明知大學校 産業技術硏究所 1984 産業技術硏究所論文集 Vol.3 No.-

A study was undertaken for developing a procedure for measuring by transient methods the thermal diffusivity of a small solid disk whose diameter is not very large compared with its thickness. Therefor, thermal diffusivity of special steels is experimentally determined by flash thermal diffusivity measurement method. In the flash diffusivity experiment, a high intensity radiative heat pulse is irradiated to the front face of a thin disk shaped sample, and the transient-temperature rise of the rear face of sample is recorded. The thermal diffusivity in thermophysical properties of the sample material is then determined using a data reduction excursion method by computer from the recorded transient temperature versus time curve. For the improvement of accuracy in determining thermal diffusivity of samples by flash technique, the solution of governing heat transfer equation with the finite pulse time effect and with the heat loss on sample surface is obtained through a Green function. The data-reduction Computer program for flash technique is then made from the solution and presented for convenience.

直線핀에 대한 過渡熱傳達에 關한 硏究

車京玉 명지대학교 1983 明大論文集 Vol.14 No.-

The analysis of unsteady state heat transfer in the straight fin of rectangular cross section has been made by making use of the theory of finite difference method and variational method. The heat transfer coefficient in the fin is given as a function of position(x), ie h=(r+1)(x/L)^r(h_a), which was suggested by L.S Han and S.G Lefkowitz. And the results are compared with the analytical solution which was obtained by assuming the heat transfer coefficient to be constant. These results show good agreement between the solution of finite difference method and analytical solution in all dimensionless time(e=αE/L^2)domain. But the solution of variational method has been found to have discrepancies with analytical solution in the some region of dimensionless time domain. When the dimensionless number N(=[√(h_a,P)/(kA)]·L) is 0.5 and 1.0, the larger the dimensionless time(e), the larger the effect of an exponential (r) to the temperature distribution. On the other hand, in the range of small N(N≤0.01), the effect of exponential (r) to the temperature distribution has been found to be negligible. The efficiency of the fin having large number of N(N≥0.5), ie heat conductivity (k) is small and length(L) is long, is decreased as the exponential (r) is increased. And the fin having small number of N, ie heat conductivity (k) is large an length(L) is short, shows that the efficiency of fin is almost constant regardless the value of exponential (r). Nomenclature A; area of cross-section of fin a; dimensionless semithickness of fin(=(b)/(l)) B; Biot number(=hl/k) b; semithickness of fin C; specific heat of fin E; time (sec) e; dimensionless time(=(αE)/(L^2)) h; convective heat transfer coefficient h_a; average heat transfer coefficient k; thermal conductivity of material of fin L; length of fin N=√[(h_a·p)/(kA)]·L P; perimeter of fin Q; heat transfer rate T; temperature of fin T_o; fin base temperatures T_∞; convection fluid temperature x; distance from base of fin X; dimensionless distance from base of fin(=(x)/(L)) α; thermal diffusivity(=k/ρ·c) θ; dimensionless temperature(=(T-T_∞)/(T_o-T_∞)) ρ; density of fin [ ] ; square matrix

가정용 가스보일러 열교환기 유형에 따른 속도분포특성에 관한 연구

최경석,차경옥 明知大學校 産業技術硏究所 2002 産業技術硏究所論文集 Vol.21 No.-

Heat transfer and velocity distribution for heat exchanger type of domestic gas boiler are different from shape, pitch, thickness of fin and array of pipe respectively. In order to measure the velocity distribution across the heat exchanger, a suction type wind tunnel was constructed and velocity distribution was measured for pitot tube(4 point) of rack type. The experiments were performed for 5 different air flow mass, rpm=3,6,9,12,15 and transverse axis of heat exchanger(x-length) is 5cm respectively. Results showed that above 9.5 nuts, velocity distribution dispersion for wet type of heat exchange is on the increase and above 5.5m/s, velocity distribution dispersion for dry type of heat exchange is on the increase. Also, velocity distribution by comparing two different type heat exchanger, dry type of heat exchange showed a higher augmentation than wet type of heat exchange.

빈발재발성 미세변화 신증후군환아에서 발생한 다발성 뇌경색증

조성옥,한헌석,차상훈,이경희,박범수,하태선,채수안 충북대학교 의과대학 충북대학교 의학연구소 1995 忠北醫大學術誌 Vol.5 No.2

신증후군에서는 동맥 및 정맥의 혈전에 의한 혈전색전증의 위험이 높다. 이는 혈 중 응고인자 Ⅰ, Ⅱ, Ⅶ, Ⅷ, Ⅹ등의 증가와 뇨소실로 인한 antithrombin Ⅲ의 감소, 섬유소 용해계의 변화, 혈소판 응집력의 증가에 기인하며 그 외 스테로이드 투여, 이뇨제 투여, 저체액 상태도 관여한다고 생각하나 이런 과응고현상에 대한 정확한 병태생리는 규명되고 있지 않다. 저자들은 내원 21개원 전 처음 신증후군 증상을 보였고 신장 조직 검사상 미세변화 신증후군으로 진단을 받고 스테로이드와 면역 억제제를 사용하였으나 6개월에 3-4회의 재발을 보이던 중 내원 1달 전 보호자 자의로 모든 약물 복용을 중단한 채로 지내다가 고열과 반혼수 상태를 보여 내원한 7세 남아에서 다발성 뇌경객증을 발견하였기에 문헌 고찰과 함께 보고하는 바이다. The risk of thromboembolism by arterial or venous thrombosis is high in the nephrotic syndrome. This may be due to the increased serum concentrations of the factor Ⅰ, Ⅱ, Ⅶ, Ⅷ, Ⅹ etc, decrease of antithrombin Ⅲ due to urinary loss, the change of thrombolytic system, increase in the platelet aggregation capacity, the use of steroid, diuretics, and hypovolemic state. But, the pathophysiology of this hypercoagulable state has not been clear. A 7-year- old boy had been diagnosed as having frequently relapsing minimal change nephrotic syndrome, 21 months ago. In spite of the administration of prednisolone and cytoxan, he had presented recurrent proteinuria in the frequency of 3-4 times per 6 months. From 1 month prior to visiting emergency room, his parents discontinued his medications, therefore, he showed fever and semicomatous mental status. In brain MRI study, multiple cerebral infarcts were noted. So, the authors report a case of multiple cerebral infarcts in a patient with frequently relapsing minimal change nephrotic syndrome with a brief review of related literature.

2유체 노즐형상에 따른 분무특성에 관한 실험적 연구

김재호,차경옥 明知大學校 産業技術硏究所 2002 産業技術硏究所論文集 Vol.21 No.-

In order to promote combustive efficiency on heat engines, an experimental study was conducted. This experiment examines the spray characteristics for the Twin-Fluid with nozzle aspect, inside the mixing chamber un the atomization. The nozzle aspect has two external type nozzles and one interval type nozzle. The mixing chamber has a cylindrical(duct) section which is made of a transparent acrylic cylindrical(duct) for flow visualization. The parameters were considered with the velocity ratio and the diameter of nozzle orifice in two different nozzle types. The wide variations of air per liquid ratio are conducted to predict the influences of the spray width.

GHP용 엔진의 개발 연구 (Ⅰ) : 저속·고출력 천연가스 엔진의 개발 The Development of Low speed·High Power Natural Gas Engine

이민호,차경옥 明知大學校 産業技術硏究所 2003 産業技術硏究所論文集 Vol.22 No.-

GHP, operated by gas instead of electrical motor, has there is better energy saving 20% comparing with EHP(electrical motor-driven heat pump) by using the exhaust heat from the engine effectively. This means that GHP has an advantage in the reduction of CO_2 which causes main greenhouse effects. Natural gas is one of the most promising alternative fuels for automotive vehicles, because it has lower exhaust emissions and better fuel economy characteristics than gasoline, diesel, LPG and can be used in conventional engine with a little modifications. Natural gas engine for GHP should be mostly based on 4 stroke water-cooled diesel engine which has high power in low speed, but sometimes could be based on automotive LPG engines because of easy modification. In this paper, a conventional LPG engine was modified to a NG dedicated engine, which can be operated with NG only, and a engine bench test was performed at various experimental condition. As a result, it was revealed that the prototype NG engine can be operated with lower exhaust emissions, better fuel economy and better thermal efficiency, but with a slightly reduced brake horse power, compared to the conventional LPG engine.