• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.695-700
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• 2006

For the precise superheat temperature control of an air conditioner, an electronic expansion valve may be used instead of a thermal expansion valve. In this paper, technical and economical aspects of expansion valves were studied in order to find out the possibility to use an electronic expansion valve to replace a thermal expansion valve.

• 동력기계공학회지
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• 제2권3호
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• pp.34-40
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• 1998

Performance characteristics of a refrigeration systems with various expansion valves and superheat changes were investigated experimentally. Experimental data have been taken utilizing three different devices; a thermostatic expansion valve, a linear type electronic expansion valve and a solenoid type electronic expansion valve. The data taken from tile three types of expansion valves were discussed with the temperature distribution of each zone in the evaporator and the superheat changes of the evaporator outlet In each zone temperature distribution fluctuated larger with the thermostatic expansion valve than with the electronic expansion valves. The optimum superheat ranged from $5^{\circ}C\;to\;15^{\circ}C$, and the superheat with the thermostatic expansion valve showed hunting phenomenon, which affected the evaporating and condensing temperature.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1083-1084
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• 2010

• 설비공학논문집
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• 제6권4호
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• pp.380-387
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• 1994

An experimental study was performed to investigate the characteristics of refrigerant flow rate control and superheat in an evaporator with an electronic expansion valve(EEV). The EEV used in this study was devised using a needle valve coupled with a stepping motor controlled by a personal computer. A Pill control equation was used to control the superheat of the evaporator and to set the superheat to $5^{\circ}C$. In order to determine an optimum running condition for the system, Pill parameters were varied for the wide range of values. The running condition of an air conditioning system with a PI control was reasonably stable compared with that of the Pill control. Experimental results for the PI control using parameter values, $K_p=1.5$, $T_i=400(sec)$ and $T_s=6(sec)$ show that the superheat reached its target value. When external disturbances were introduced to the system, the superheat target value was reached within about 3 minutes. When the EEV was applied to the air conditioning system driven by an inverter, room temperature control was excellent.

• 에너지공학
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• 제10권3호
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• pp.253-265
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• 2001

본 논문은 멀티형 공조/냉동시스템의 증발기의 과열도(증발기 2상영역과 출구영역의 냉매기 온도차)제어를 위한 모델링과 PI제어에 관한 연구이다. 먼저, 제어기 설계를 목적으로 하여 압축기, 응축기, 증발기 그리고 전자식 팽창밸브의 동특성이 수학적으로 모델링된다. 증발기에서의 일정한 크기의 과열도 발생을 제어목적으로 한정한 후 전자식 팽창밸브의 전류입력으로부터 증발기의 2상영역과 과열영역에서의 관벽의 온도로의 전달함수들이 유도된다. 비례적분 제어기의 폐루프시스템의 안정성과 제어성능은 Nyquist 안정성 판별법에 의해 분석된다. 시뮬레이션 결과가 제시된다.

• 대한기계학회논문집
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• 제19권8호
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• pp.2012-2021
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• 1995

An experimental study was performed for the analysis of dynamic characteristics of refrigeration system by controlling the evaporator superheat. Experimental data have been taken utilizing two different devices, thermostatic expansion valve(T.E.V.) and electronic expansion valve(E.E.V.), for the control of the evaporator superheat. The ranges of parameters, such as superheat, mass flow rate of refrigerant and inlet temperature of evaporator were 5-30.deg. C 90-170 kg/h and 10-25.deg. C, respectively. The data taken from the T.E.v.and E.E.v.were discussed with the control of the superheat, pressure drop, refrigerating capacity, compression work, evaporating temperature, condensing temperature and COP affecting performance characteristics of refrigeration system. In case of the refrigerant flow control with T.E..V., the superheat and pressure drop of the evaporator varied periodically, but the control with E.E.V., the parameters were very stable. In E.E.v.control, refrigerating capacity, compression work and evaporating temperature were decreased with increasing superheat, and the highest COP was obtained in the range of superheat from 5.deg. C to 15.deg. C.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.387-388
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• 2011

• 설비공학논문집
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• 제18권11호
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• pp.881-887
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• 2006

The objective of this study are to analyze the flow characteristics of R22 flowing through EEVs and to develop an empirical correlation to predict the refrigerant flow rate. The mass flow rates of EEVs with different geometries were measured at various condensing temperatures, subcoolings, and EEV openings. Based on the experimental data, an empirical correlation for mass flow predictions in EEVs was developed by modifying the orifice equation. The correlation showed good agreement with the measured data for R22 with average and standard deviations of 1.4% and 6.1%, respectively. Approximately 90% of the measured data were within ${\pm}10%$ of the predictions.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1285-1292
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• 2011

본 연구에서는 전자식 팽창밸브를 적용한 반도체 공정용 칠러에 관한 실험적 연구를 통해 시스템 특성을 파악하였다. 또한 온도 변화에 따른 신속한 대응을 할 수 있도록 온도상승 및 하강실험, 부하변화에 따른 온도영역별 제어정밀도 실험을 함으로써 각 제어 방식에 따른 운전 특성을 파악하였다. 온도상승 시 소비전력은 8.9 kW로 측정되었으며 CH1이 37.5분, CH2가 39.5분이 소요되었으며, 온도하강에는 총 26.5분이 소요되었다. 부분부하가 적용되는 경우 전부하가 적용되는 경우에 비해 제어정밀도의 변화폭이 큰 것으로 나타났으며 스텝모터 구동방식을 적용한 CH2의 제어정밀도가 상대적으로 우수한 것으로 나타났다. 냉각수를 이용한 냉각사이클 영역에서 소비전력은 1.8 kW로 냉동사이클을 적용한 방식에 비해 절반가량으로 감소된 것으로 나타났다. 본 연구는 실험결과를 바탕으로 반도체 공정용 칠러의 최적제어방안을 제시하였다.

• 한국지열·수열에너지학회논문집
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• 제14권4호
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• pp.27-34
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• 2018

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.