• 사물인터넷융복합논문지
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• 제7권3호
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• pp.63-68
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• 2021

국내의 전기히터 제조업체에서는 기존 제품의 효율을 향상시키는 기술 개발에 집중하고 있다. 선박 연료용 전기히터는 그 크기가 크고 소형화/고효율화에 대한 난이도가 높아 아직까지 기술개발을 시도하는 기업은 많지 않은 실정이다. 기존의 전기히터는 선박 엔진 연료의 유동경로가 단조롭기 때문에 가열매체의 열교환 튜브와의 접촉시간이 매우 짧아 가열 효율이 낮은 구조이며, 관형으로 제작되어 있기 때문에 가열효율과 무관하게 부피가 매우 크게 제작되므로 가열장치의 설치공간을 확보해야 한다. 이로인해 해외 선진사에서 적용하고 있는 관형 전기히터 장치는 내부의 특정부분이 손상되었을때 관형 가열기를 모두 분해하여야 하고, 열교환 튜브가 손상된 경우에는 열교환 튜브를 모두 분해해야 하므로 유지와 보수에 어려움이 있다. 본 연구에서는 250kW 용량급 판형 전기히터 가열기를 통해 시간당 10ton의 선박 엔진 연료를 가열할 수 있고, 최대온도를 150℃까지 설정할 수 있는 판형 전기히터에 대한 기초연구를 수행하였다.

• Korean Journal of Acupuncture
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• 제38권4호
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• pp.282-289
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• 2021

Objectives : The purpose of this study is to construct a model of the possible thermal runaway of electronic moxibustion and to implement an appropriate risk management method. Methods : To reproduce the system error situation of the electronic moxibustion circuit equipped with microcontroller unit, temperature sensor and heater, a code was set to disable the signal input to temperature sensor and maintain "high" heating signal to heater. The temperature change of electronic moxibustion was compared between 3 types of heater module; module 1 consisting of a combination of heater+0 ohm+0 ohm resistance, module 2 consisting of a combination of heater+Polymeric Positive Temperature Coefficient (PPTC)+0 ohm resistance, and module 3 consisting of a combination of heater+PPTC+10 ohm resistance. The temperature change was measured using a polydimethylsiloxane (PDMS) silicone phantom. After maintaining surface temperature of the phantom at 31~32℃ for 20 seconds, electronic moxibustion was applied. After operating electronic moxibustion, the temperature change was measured for 660 seconds on the surface and 900 seconds at 2 mm depth. Results : Regardless of the module type, the time-dependent change in temperature showed a rapid rise followed by a gentle curve, and a sharp drop in temperature after reaching the maximum temperature about 10 minutes after the switching the moxibustion on. Temperature measured at the depth of 2 mm below the surface increased slower and to a lesser extent. Module 1 reached highest peak temperature with largest change of temperature at both depths followed by module 2, and 3. Conclusions : Through the combination of PPTC+resistance with the heater of electronic moxibustion, it is possible to limit the rise in temperature even with the software error. Thus, this setting can be used as an independent safety measure for the electronic moxibustion control unit.

• 대한기계학회논문집B
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• 제24권9호
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• pp.1239-1246
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• 2000

The objective of this work is to measure space and time resolved wall heat fluxes during nucleate pool boiling of R113/R11 mixtures using a microscale heater array in conjunction with a high speed CCD. The microscale heater array is constructed using VLSI techniques, and consists of 96 serpentine platinum resistance heaters on a transparent quartz substrate. Electronic feedback circuits are used to keep the temperature of each heater at a specified temperature and the variation in heating power required to keep the temperature constant is measured. Heat flux data around an isolated bubble are obtained with triggered CCD images. CCD images are obtained at a rate of 1000frames/second. The heat transfer variation vs. time on the heaters directly around the nucleation site is plotted and correlated with images of the bubble obtainedby using the high speed CCD. For both of the mixture(R11/R113) and pure system(pure R11, pure R113), the wall heat fluxes are presented and compared to find out the qualitative difference between pure and binary mixture nucleate boiling.

• 동력기계공학회지
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• 제21권3호
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• pp.30-36
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• 2017

Carbon fiber shows excellent heat generation value and thermal efficiency comparing with the metallic materials because of its far infrared-rays and radiant heat. So, high performance and economic steam boiler system for the industry can be manufactured by using the carbon fiber heater. The far infrared ray radiation rate was more than 90 % of carbon fiber. Steam boiler system with carbon fiber heater in this study is made up of heating section. In the proof test of steam boiler, the aimed temperature and dwelling time were at $500^{\circ}C$ for 8,000 hours, $600^{\circ}C$-3,000 hours, and $700^{\circ}C$-1,000 hours. The temperature rise rate of steam boiler with carbon fiber heater was about 40% faster than that of the conventional boiler.

• 대한기계학회논문집B
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• 제33권10호
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• pp.729-736
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• 2009

Pool boiling heat transfer and critical heat flux (CHF) of water-based nanofluids with alumina and titania nanoparticles of 0.01% by volume were investigated on a disk heater at saturated and atmospheric conditions. The experimental results showed that the boiling in nanofluids caused the considerable increase in CHF on the flat surface heater. It was revealed by visualization of the heater surface subsequent to the boiling experiments that a major amount of nanoparticles deposited on the surface during the boiling process. Pool boiling of pure water on the surface modified by such nanoparticle deposition resulted in the same CHF increases as what boiling nanofluids, thus suggesting the CHF enhancement in nanofluids was an effect of the surface modification through the nanoparticle deposition during nanofluid boiling. Possible reasons for CHF enhancement in pool boiling of nanofluids are discussed with surface property changes caused by the nanoparticle deposition.

• 한국정밀공학회지
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• 제17권3호
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• pp.58-67
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• 2000

Electron gun heaters are used to heat a cathode in video(TV) monitors. Major defects of the electron gun heaters include dimensional inaccuracy and pollution with dirty materials. In this paper, to save the labor and time being taken to inspect the heaters, a machine vision system is considered. For the system, a new algorithm is developed to measure the 9 different dimensions of each heater and to detect polluted defects. The algorithm consists of three stages. In the first stage, the center of the heater image is obtained and then its boundary detection is performed. For the efficient boundary detection, a mask called the sum mask is used. In the second stage of the algorithm, a set of fiducial points are determined on the boundary image. Finally, using the fiducial points specified dimensions are measured and the amount of polluted area is computed in the third stage. The performance of the algorithm is evaluated for a set of real specimens. The results indicate that measurements obtained by the algorithm satisfy the tolerance limits fur most of the dimensions and the algorithm detects the polluted defects successfully.

• 한국대기환경학회지
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• 제3권1호
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• pp.65-73
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• 1987

Indoor air pollution problems, in fact, have been neglected due to the unawareness of its seriousness and the lack of accumulated data. Recently, some movement of research and regulations, however, have been made for several indoor air pollutants. In this study, one of the carcinogenic polynuclear aromatic hyrocarbon, Benzo(a) pyrene in indoor airborne particulate, was measured and analyzed to estimate emission strength of BaP from an unvented kerosene heater and to know its level in indoor environment with use of a kerosene heater and a wood-burning fireplace. By the measurement of BaP level in a dark room with air exchange rate of app. 3.0, BaP emission strength of a kerosene heater (11,000Btu/hr) was estimated to be 326.6ng/hr (or 29.7 ng/$10^3$ Btu). With 4-hr operation a day of the kerosene heater in an apartment, the BaP level became 2.97ng/m$^3$ from 0.27ng/m$^3$ of background level. The operation of a wood-burning fireplace app. 2hr a day, on the other hand, increased the BaP level from 0.16ng/m$^3$ of background to 3.53ng/m$^3$. So proper ventilation must be considered seriously when unvented heating facilities are used in indoor environment.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.321-326
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• 2006

초음속 유도무기에 사용되고 있는 공기흡입 추진기관의 지상 연소시험에서 요구되는 700K-6바의 공기를 공급하기 위한 Vitiated형 공기 가열기에 대한 개념설계를 수행하였다. 본 가열기는 여분의 기체 산소와 공기를 혼합하는 예혼합기, 예혼합 기체와 연료를 혼합시키는 혼합기, 점화기를 포함하는 연소실과 수축팽창 노즐, 그리고 디퓨저로 구성하였다. 가열기에 사용된 연료는 천연가스이며, 유동해석을 통해 가열기의 각 구성요소의 성능을 파악하였으며, 점화 후 화염유지가 이루지는 것을 해석적으로 확인하였다.

• 한국분무공학회지
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• 제15권2호
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• pp.83-93
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• 2010

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• 대한기계학회논문집A
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• 제32권9호
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• pp.720-727
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• 2008

Microfluidic single chip integrating thermopneumatic micropump and micro check valve are developed. The micropump and micorvalve are made of biocompatible materials, glass and PDMS, so as to be applicable to the biochip. By using the passive-type check valve, backward flow and fluid leakage are blocked and flow control is stable and precise. The chip is composed of three PDMS layers and a glass substrate. In the chip, flow channel and pump chamber were made on the PDMS layers by the replica molding technique and pump heater was made on the glass substrate by Cr/Au deposition. Diameter of the pump chamber is 7 mm and the width and depth of the channel are 200 and $180{\mu}m$, respectively. The PDMS layers chip and the heater deposited glass chip are combined by a jig and a clamp for pumping operation, and they are separable so that PDMS chip is used as a disposable but the heater chip is able to be used repeatedly. Pumping performance was simulated by CFD software and investigated experimentally. The performance was the best when the duty ratio of the applied voltage to the heater was 33%.