• Title/Summary/Keyword: Electric water heater

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Thermal Performance of the Bubble Jet Loop Heat Pipe Using Eccentric Heater in Evaporating Section (증발부에 편심 가열부를 사용한 버블젯 루프 히트파이프의 열성능)

  • Kim, Jong-Soo;Kim, Sung-Bok
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.12
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    • pp.652-658
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    • 2015
  • The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

Defrosting Behavior of Fin-Tube Heat Exchanger with PTC Heating Sheet

  • Jhee, Sung;Lee, Kwan-Soo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.9 no.1
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    • pp.29-38
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    • 2001
  • In this paper, the defrosting characteristics of a PTC heating sheet is investigated by means of a defrosting heat source for the fin-tube heat exchanger in a refrigerator The defrosting characteristics of the PTC heating sheet are examined and compared with those of a conventional electric heater experimentally. It is found that the characteristics of the water draining rate with the defrosting time show a smoothly oscillating pattern when the PTC heating sheet Is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is found to be about 75%, which is about 25% higher than that of the electric heater. Also, the reduction of the defrosting time and the increment of the defrosting efficiency may be obtained by improving the arrangement of the heating elements of the healing sheet. It is shown that the defrosting time of the PTC heating sheet increases linearly with the amount of frost, whereas the defrosting efficiency is nearly constant. When applying the PTC heating sheet to the refrigerating system, one should notice the fact that the defrosting performance of the PTC heating sheet may be degraded due to the repetitive operations.

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An experimental study of defrosting behaviors on the fin-tube heat exchanger with PTC heating sheet (PTC 전열시트를 사용한 핀-관 열교환기의 제상 특성에 관한 실험적 연구)

  • Jhee, S.;Lee, K.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.1
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    • pp.147-155
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    • 1999
  • In this work, the defrosting characteristics of PTC heating sheet used as a defrosting heat source of fin-tube heat exchanger in a refrigerator have been experimentally compared with those of conventional electric heater. It is found that the characteristics of water draining rate with defrosting time show smoothly oscillating pattern when PTC heating sheet is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is about 75%, which represents about 25% higher than that of the electric heater. A reduction of defrosting time and an increase of defrosting efficiency may be obtained by improving the arrangement of heating elements of the heating sheet. It is shown that the defrosting time of PTC heating sheet increases linearly with the amount of frost, however the defrosting efficiency is nearly constant. In the application to the refrigerating system, one should notice the fact that the defrosting performance of PTC heating sheet may be defraded due to the repeated operations.

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A study on the solar assisted heating system with refrigerant as working fluid (냉매를 작동유체로 사용하는 태양열 난방시스템에 관한 연구)

  • Kim, Ji-Young;Ko, Gawng-Soo;Park, Youn-Cheol
    • Journal of the Korean Solar Energy Society
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    • v.25 no.4
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    • pp.37-44
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    • 2005
  • An experimental study was conducted to analyze performance of a heating system with variation of control logic of the system. The system uses a solar as heat source and composed with heat pump that uses R-22 as working fluid. The difference between the developed system and the commercially available heating system is working fluid. The solar assisted heating system which was widely distributed in the market uses water as a working fluid. It could be freezing in case of the temperature drops down under freezing point. The anti-freezing fluids such as methyl-alcohol or ethylene-glycol are mixed with the water to protect the freezing phenomena. However, the system developed in this study uses a refrigerant as a working fluid. It makes the system to run under zero degree temperature conditions. Another difference of the developed system compare with commercial available one is auxiliary heating method. The developed system has removed an auxiliary electric heater that has been used in conventional solar assisted heating system. Instead of the auxiliary electric heater, an air source heat exchanger which generally used as an evaporator of a heat pump was adapted as a backup heating device of the developed system. As results, an efficiency of the developed system is higher than a solar assisted heat pump with auxiliary electric heater. The merit of the developed system is on the performance increment when the system operates at a lower solar energy climate conditions. In case of the developed system operates at a normal condition, COP of the solar collector driven heat pump is higher than the air source heat exchanger driven heat pump's.

Study on the Heat Performance of CNT/carbon Fiber Plane Heater (탄소계 면상발열체 발열 특성 연구)

  • Ko, Yeongung;Kang, Yeongsik;Chung, Yongsik
    • Textile Coloration and Finishing
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    • v.32 no.1
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    • pp.65-71
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    • 2020
  • Electrical energy is used for heating and cooling because electric cars do not have engines and cooling water. The downside is that when the heating and cooling system is applied to electric vehicles, about 40 percent of the energy is spent on heating and cooling, which is less efficient in winter. This has increased demand for electric vehicle battery efficiency. In this study, the condensation and dispersion of carbon nanotubes were controlled, and carbon fibers and composite slurry were manufactured without binders to manufacture paper. Manufactured by content showed the highest heat generation characteristic at 143℃ with a carbon fiber content ratio of 20wt% and confirmed that the heat temperature rises with increasing pressure. The plane heaters made through this study can be applied to a variety of products other than electric vehicles because they can be simplified by process and high temperature.

A Study on the Performance Characteristics of a Heat Pump System using Stack Wast Heat in Fuel Cell Vehicles (스택 폐열을 이용한 연료전지 자동차용 열펌프 시스템의 성능 특성에 관한 연구)

  • Jeon, Byungyong;Ko, Wonbin;Park, Youn Cheol
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.8
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    • pp.325-330
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    • 2016
  • This study was conducted to develop a heating system for a fuel cell-driven electric vehicle. The system consists of a compressor, an expansion device and three heat exchangers. A conventional air source heat exchanger is used as primary heat exchanger of the system, and an additional water source heat exchanger is used as a pre-heater to supply heat to the upstream air of the primary heat exchanger. On the other hand, the third heat exchanger consists of a water-to-refrigerant heat exchanger. The heat source of the pre-heater and the water-refrigerant heat exchanger is the waste heat from the fuel cell's stack. In the experiment, the indoor and the outdoor air temperature were fixed, and the compressor speed, EEV opening and waste heat temperature were varied. The results indicate that the $COP_h$ of the proposed system is 3.01 when the system is operating at a 1,200 rpm compressor speed, 50% EEV opening, and $50^{\circ}C$ waste heat source temperature in air pre-heater operation. However, when the system uses a water-refrigerant heat exchanger, the $COP_h$ increases to up to 9.42 at the same compressor speed and waste heat source temperature with 75% EEV openings.

A study on the versatility of railway vehicles. saving electric heater (철도 차량용 객실 전기 난방기의 다목적 활용에 대한연구)

  • An, Jong-Kon;Chai, Jin-Woo
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.116-123
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    • 2010
  • The Study of the Railway-saving electric water heaters to replace electric heaters when combined, Separate bathroom with hot water in winter, as coaches, without the need to warm up with hot water may be.To improve passenger service can tell. High-efficiency energy saving energy from furnace. Due to fuel cost savings and business improvements come true. Can prevent pollution.Heating the room next to railway vehicle utilization is expected to nopeulgeot.Is expected to expand gradually.

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An experimental study of behavior of defrosting on the fin-tube heat exchanger (핀-관 열교환기에 대한 제상 거동에 관한 실험적 연구)

  • Lee, Kwan-Soo;Kim, Kyu-Woo;Ji, Sung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.6
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    • pp.649-657
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    • 1998
  • In this study, the effects of the various conditions of frosting and defrosting on the behavior of defrosting in a fin-tube heat exchanger have been examined experimentally. The electric heater is used for defrosting in a fin-tube heat exchanger It is shown that there are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after the completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering the degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of the frost irrespective of the frosting condition. The defrosting behavior is affected by the frosting density as well as the frost accumulation, which vary with the experimental operating conditions during the frosting period. The heat loss to the surrounding air decreases, and the melting and defrosting efficiencies show high values with decreasing heat input.

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Optimal Scheduling of Electric Water Heater Considering User Comfort For HEMS (편의성을 고려한 HEMS 전기온수기 최적스케줄링에 관한 연구)

  • Lee, Hyun-Seung;Shin, Je-Seok;Oh, Do-Eun;Lee, Jung-Il;Kim, Jin-O
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.501-502
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    • 2015
  • 매년 증가되는 전력소비량에 대응하여 스마트그리드 기술을 기반으로 수용가 측의 에너지관리 중요성이 부각되고 있으며, 홈 에너지관리시스템(HEMS, Home Energy Management System)은 전기요금 절감과 효율적인 전력소비의 중요한 체계로써 기대되고 있다. 일반적으로, 가정에서 높은 전력소비를 가진 가전제품은 계절성 부하로 전기온수기, 냉/난방기를 일컫는다. 즉, 계절성 부하에 적절한 에너지관리, '최적부하 스케줄링'은 전기요금 절감과 직결되는 것을 의미한다. 본 논문은 Modified Branch-and-Bound 기법을 사용하여 사용자의 편의성을 고려한 전기온수기(EWH, Electric Water Heater)의 스케줄링을 실시하겠다. 여기서 사용자의 편의성이란, 외부의 온도변화 또는 습관에 따라 그 부하를 사용하는 것을 의미한다. 온수사용량, 수온 설정온도 변화의 편의성 제약조건을 고려하여 온수기를 효과적으로 운영하는 스케줄링을 실시한다. 이러한 편의성 내에서 온수기를 운영하며, 작동모드는 3가지(정지, 일반/급속가열) 모드가 존재하며, 다양한 요금제도에서의 스케줄링 결과를 절감된 전기요금으로 비교하겠다.

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