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권형정 동의공업대학 2001 論文集 Vol.27 No.1
Spray cooling makes high temperature surface cooled rapidly by means of liquid heat or latent heat which created by spray. The spray cooling is of interest to many applicants in the industries such as continuous casting of ironworks, quenching of metal, heat sinker of space shutter, cooling of high ability electronic device, partial cooling of internal combustion emgine and grass manufacture. In order to study heat transfer characteristics of spray cooling for the purpose of uniform and soft cooling of high temperature surface, a series of experiments for a hot, horizontal copper flat plate was performed by downflow spray using flat spray nozzle. Cooling curves were measured under the various experimental conditions of flow rates and temperatures of cooling water.
빙축열을 이용한 대형빌딩 공기조화시스템 개발과 설계전산화에 관한 연구
권형정,김원영,김용모,김경근 한국마린엔지니어링학회 1991 한국마린엔지니어링학회지 Vol.15 No.5
In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air-conditioning systems are being operated during daytime in summer season. Therefore, it is necessary to construct an additional electric power plant and to develop the new air-conditioning system for relieving the peak load. This paper analysed the performance characteristics of this experimental regenerative ice energy system by means of a bundle of the heat-pipes. And the result of this analysis was applied to the simulation of an air-conditioning system model. Also, an operation program of moisture air was made according to air load and in order to computerize the air-conditioning system a CAD program was developed by the properties of moisture air.
히이트파이프 다발을 이용한 냉축열시스템에서의 대류열전달에 관한 연구
권형정,김경석,김경근 한국마린엔지니어링학회 1990 한국마린엔지니어링학회지 Vol.14 No.4
In the design of an electric power plant, the capacity to meet the peak load demand is one of the important factors to be considered. This peak load usually occurs when the most of the cooling air conditioning systems are being operated during daytime in summer season, which inevitably entails the construction of an additional electric power plant. This study is aimed to carry out a basic experiment for the development of a cooling air conditioning system using the ice energy by the surplus electric power during the night-time. The experimental apparatus consists of four major parts; (1) the heating section consisting of the air duct and I.D. fan, (2) the cold section with the ice chamber, (3) the bundle of heat pipes made in a form of the staggered arrangement with ${C_y}/{d_o}$=2.0 and ${C_x}/{d_o}$=1.73, (4) the refrigerator system to cool down the ice chamber. This study involves an intensive experiment concerning the convective heat transfer of the air flow surrounding the bundle of heat pipes. This major experimental parameters are the amount of working fluid, the velocity of air and the working temperature. The major findings of the present study are as follows; (1) The optimum amount of the working fluid necessary for the horizontal heat pipes is much more than that for the vertical type. (2) The convective heat transfer coefficients of the air are coincided with the empirical equations of Grimson and ${\breve{Z}ukauskas}$. (3) The equation of the mean heat transfer coefficient obtained in the present study is ${N_um}=0.32 {Re_max^{0.63}}$.
김태한,권형정 동의공업대학 2001 論文集 Vol.27 No.1
Compute simulations for closed type centrifugal pump is carried out using the commercial code CFX Tascflow. Computed results, which are pressure, velocity between impeller and other impeller, required power and performance etc, was compared with actual experimental data. We found that there are hard loads due to velocity and pressure at in/outlet impeller, and pump head is within 10% error limit when volute head loss is considered to 20% loss of total head. Accordingly it is possible to get optimal impeller shape through the iteration improvement works. But, as this study was done for only impeller in order to confirm the validity of Tascflow program, computation including the volute is required for actual comparison. For this, volute data treatment process for grid generation remains with future projects.
속도추정기를 이용한 3상유도전동기의 센서리스 속도제어에 관한 연구
정주윤,권형정 동의공업대학 2000 論文集 Vol.26 No.1
Several methods of induction motor drives, which use speed estimators instead of shaft encoders, have been reported. However, the characteristics of the vector control employing stator voltages and currents usually deteriorate as the speed gets lower because it is difficult to calculate rotor flux due to de-offset and saturation of integrators. In this paper, to make it possible to calculate rotor flux at standstill, the new rotor flux estimator which replace integrators with two lag circuits is proposed. Simulation and experiment results confirm the validity of this control scheme.
가열된 열가소성 재료의 금형내부에서의 온도분포에 관한 연구
리우환,권형정,양희찬 한국마린엔지니어링학회 1989 한국마린엔지니어링학회지 Vol.13 No.3
A calcuation method of the temperature distribution for various shape due to the constant heat input is studied in this paper. So far, the method of try and error is carring out on the mould design. The reason of adopting this method is due to hardly estimate the cooling system in the mould base. As above description, the most part of the mould is supposed as a rectangular, cylinderical and triangular shape and made a governing equation of heat transfer and solved it to numerical analysis by finite-difference method(central- difference). After that in order to confirm that the temperatures are measured on different shape specimens from the part of frequent usage of which are carbon, crome-molybden, tool and stainless steel those were compared with the results of calculations presented in this paper.