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세척이 가능한 원통 코일형 열교환기의 파울링 특성에 관한 연구
황준현(Jun Hyeon Hwang),나병철(Byung Chul Na),오세기(Sai Kee Oh),구경민(Kyoung Min Koo),이재근(Jae Keun Lee),안영철(Young Chull Ahn) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.2
In this work, we studied the shell and helically coiled tube heat exchangers. Shell and coil heat exchangers with different rate of water flow and plate heat exchanger with same capacity were tested for condensing conditions. We proposed design guide using modified Wilson plot method. We compared fouling characteristics between shell and coil heat exchanger and plate heat exchanger, when they were washed and were not washed. The shell and coil heat exchanger showed 120% of higher saturated fouling resistance value and 4% of better heat transfer ratio than the plate heat exchanger.
수평원관 내 CO<sub>2</sub> R-22 및 R-134a의 증발열전달 특성에 관한 실험적 연구
윤린,황준현,최영돈,김용찬,Yun, Rin,Hwang, Jun-Hyeon,Choi, Young-Don,Kim, Yong-Chan 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7
Evaporation heat transfer coefficients of carbon dioxide($CO_2$), R-22, and R-134a in a horizontal smooth tube were measured and analyzed as a function of heat flux, mass flux, and evaporating temperature. The experiments were carried out by varying heat flux from 10 to 20 $kW/m^2$, mass flux from 170 to 340 $kg/m^2s$, and saturation temperatures of 5 and $10^{\circ}C$. It was found that the heat transfer coefficient of $CO_2$ decreased with a rise of quality due to an earlier liquid-film dryout as compared to R-22 and R-134a. Averaged heat transfer coefficients of $CO_2$ were 22-63% higher than those of R-22 and R-134a at all test conditions. The effects of mass flux and heat flux on averaged heat transfer coefficients were much greater in $CO_2$ than in R-22 and R-134a. When comparing $CO_2$ test results with the correlations in the literature, the existing models yielded large deviations at medium and high qualities. Therefore, a generalized correlation for $CO_2$evaporation heat transfer needs to be developed by including the effects of dryout phenomenon.
Heuristic Algorithm for Performance Improvement of Non-Communication Inverter Type Refrigerator
민선규(Seon Gyu Min),김형준(Hyung Jun Kim),이주경(Ju Kyoung Lee),황준현(Jun Hyeon Hwang),이석(Suk Lee) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.2
Inverter-Type refrigerators are known to consume less energy by varying the inverter frequency according to indoor temperatures and refrigerant pressure through indoor-outdoor communication. However, many commercial operators cannot afford to replace indoor units with ones capable of communication. In a non-communication configuration, indoor units are connected with an inverter-type outdoor unit without intercommunication abilities. The research goal is finding appropriate operating parameters to achieve energy efficiency. Thus, an operation algorithm with two modes is proposed, i.e., one to search the best operating parameters and one for normal operation with the best parameters. The experimental evaluation showed 11.27% reduction in energy consumption, indicating a good applicability of the algorithm.
진병주(Byoung-Ju Jin),오승택(Seung-Taek Oh),윤정인(Jung-In Yoon),황준현(Jun-Hyeon Hwang),진심원(Sim-Won Jin),경익수(Ick-Soo Kyung),Donald C Erickson 대한설비공학회 2008 대한설비공학회 학술발표대회논문집 Vol.2008 No.2
Refrigeration plants using absorption principles have been around for many years with initial development taking place over 100 years ago. Although the majority of absorption cycles are based on water-LiBr cycle, many applications exist where ammoniawater can be used, especially where lower temperatures are desirable. In both systems water is used as working fluid, but in quite different ways: as a solvent for the ammonia system, and as refrigerant for the lithium bromide system. This explains that the lithium bromide absorption system is strictly limited to evaporation temperatures above 0℃. The main industrial applications for refrigeration are in the temperature range below 0℃, the field for the binary system ammonia-water.
이호생(Ho-Saeng Lee),진병주(Byoung-Ju Jin),윤정인(Jung-In Yoon),황준현(Jun-Hyeon Hwang),진심원(Sim-Won Jin),경익수(Ick-Soo Kyung),Donald C Erickson 대한설비공학회 2009 설비공학 논문집 Vol.21 No.8
Experimental results for performance characteristics of small H₃ absorption chiller/heater are presented. The apparatus consists of 7RT water-cooled absorption system, solution pump, boiler, cooling tower and peripheral devices. The effect of experimental parameters, such as refrigerant mass flow rate, solution mass flow rate and cooling water temperature have been investigated in view of the system performance. The capacity of each heat exchanger increased as refrigerant mass flow rate increased in cooling mode. Also, a cooling capacity increased as a strong solution mass flow rate increased. The cooling and heating COP show 0.5, 1.5 regardless of refrigerant mass flow rate, respectively. The results focus on the evaluation for performance characteristics of system with respect to variation of refrigerant mass flow rate under standard design conditions.
임효준(Hyo Joon Lim),이주경(Ju Kyoung Lee),황준현(Jun Hyeon Hwang),이경창(Kyung Chang Lee),이석(Suk Lee) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.6
Unlike household refrigerators, commercial refrigerators are composed of separate indoor and outdoor units. The outdoor unit of most commercial refrigerators is designed to run at a fixed speed, which results in low energy efficiency and loud fan noise. Moreover, it cannot respond flexibly to changing thermal load in the indoor unit. Inverter type outdoor units can address such problems through speed changes based on information obtained from the indoor unit. However, using two units from different manufacturers is often not a viable solution. If condition changes in the indoor unit can be detected without communication between the two units, it is possible to adjust the speed of the outdoor unit. This paper attempts to analyze the signal from the outdoor unit when the condition of the indoor unit changes by varying the thermal load.