Journal of the Korean Society for Geothermal and Hydrothermal Energy (한국지열·수열에너지학회논문집)

Korean Society for Geothermal and Hydrothermal Energy (한국지열·수열에너지학회)
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Precision Control of Water Bath Temperature using Air Cooled Variable Refrigerant Flow Chiller

공랭식 변유량 냉매 냉동기를 적용한 수조 온도의 정밀 제어

  • Jeong, Kwang-Ju (Graduate Seoul of Energy and Environment, Seoul National University of Science & Technology) ;
  • Kim, Young Il (School of Architecture, Seoul National University of Science & Technology)
  • 정광주 (서울과학기술대학교 에너지환경대학원) ;
  • 김영일 (서울과학기술대학교 건축학부)
  • Received : 2018.09.28
  • Accepted : 2018.11.02
  • Published : 2018.12.01
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Abstract

This study compared constant water bath performances of conventional water-cooled refrigerator and electric heater with an air-cooled VRF chiller and electric heater equipped with optimal control algorithm. In heating mode, the air cooled VRF chiller and electric heater combination reduced the set temperature arrival time by an average of 42 minutes, and energy was also reduced by 18%. In cooling mode, the two systems took 70 minutes to reach the set temperature and showed no difference. Energy was reduced by 33.5% with the new system. For constant temperature maintaining experiment, after reaching the set temperature of $15^{\circ}C$, $20^{\circ}C$ and $22^{\circ}C$, temperature deviations were all in the range of $-0.2^{\circ}C$ to $+0.1^{\circ}C$. Energy was reduced by an average of 84.9%. Through this study, possibility of precise temperature control by an air cooled VRF chiller system was confirmed.

Keywords

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Fig. 1. Diagram of a refrigerator and VRF system.

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Fig. 2. Temperature and load characteristics of conven-tional water bath.

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Fig. 3. Temperature and electric heater power characteristics of refrigerator and electric heater system for various set temperature conditions.

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Fig. 4. Load characteristics of conventional refrigerator and electric heater system.

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Fig. 5. algorithm of VRF.

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Fig. 6. Diagram of the VRF and electric heater system.

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Fig. 7. Temperature and electric heater power characteristics of VRF and electric heater system for various set temperature conditions.

Table 1. Refrigerator and VRF system

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Table 2. Load and device power for constant temperature condition (15℃)

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Table 3. Control algorithm of VRF and electric heater system

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Table 4. Comparison of time and power consumption for change of set temperature

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Table 5. Comparison of temperature deviation and power consumption for constant temperature condition

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