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축류 팬의 공력 성능과 소음 성능을 향상시키기 위한 케이싱 펜스의 적용
박근태(Keuntae Park),최해천(Haecheon Choi),최석호(Seokho Choi),사용철(Yongcheol Sa) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
A casing fence is a newly proposed casing treatment to enhance the aerodynamic and aeroacoustic performances of the axial flow fan that exhausts air into the atmosphere for cooling and ventilation. In the present study, the fence is applied on the shroud near the trailing edge of an axial flow fan used in an outdoor unit of an air conditioner operating at the design condition. The Reynolds number of the fan is 547,000 based on the radius of the blade tip and the tip velocity. We simulate turbulent flows and acoustic fields in the fan using large eddy simulation (LES) coupled with Ffowcs-Williams Hawkings (FW-H) equations. From the numerical simulations with the casing fence, the efficiency of the fan is increased by about 9.5% and the propagating noise is reduced by 0.5dB (A) compared with those without the fence. The fence decreases backflows induced by the tip-leakage vortex near the casing, suppressing the circumferential development of the tip-leakage vortex from the previous blade to the next blade. Also, it reduces the double-leakage tipclearance flow generated at the trailing edge of the blade tip. As a result, the blockage effect by the leakage flow is reduced and the efficiency is increased, and pressure fluctuations on blade surfaces due to the tip-leakage vortex are reduced, resulting in a reduction of the propagating noise.
설계 조건에서 작동하는 축류 팬 주위 익단 누설 유동의 큰 에디 모사
박근태(Keuntae Park),최해천(Haecheon Choi),최석호(Seokho Choi),사용철(Yongcheol Sa) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
An axial fan with a shroud generates complicated vortical structures by the interaction of the axial flow with the fan blades and duct near the blade tips. Large eddy simulation (LES) is performed for flow through a forward-swept axial fan, operating at the design condition of Re = 547,000 based on the radius of blade tip and the tip velocity. The present study predicts the mean values of the flow and head coefficients quite well as compared with the experimental measurements. It is found that two unsteady vortical structures are formed near the blade tip: the tip leakage vortex (TLV) and vortex ropes. The TLV is initiated near the leading edge, develops downstream, and impinges on the pressure surface of the next blade, where the pressure fluctuations and turbulence intensity become high. Vortex ropes are initiated at the aft part of the blade and they merge with TLV.
VRF 시스템의 고효율 부하대응 열교환기 가변유로 기술에 관한 연구
장지영(JiYoung Jang),송치우(ChiWoo Song),윤필현(PhilHyun Yoon),사용철(YongCheol Sa) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
In this study, the latest heat exchanger technology to improve the performance of the VRF system is introduced. The heat exchanger is a key component in VRF system performance and in order to respond effectively to various loads, a technology has been developed that divides the heat exchanger into three passages through valve control and realizes optimal load-response operation by changing the flow passage. This technology enables bypass operation to respond to a small load under heating overload conditions, and prevents freezing of the lower end of the heat exchanger to supply continuous heating operation. In addition, it was possible to increase the operating efficiency by about 20% by changing the heat exchanger flow path during cooling and heating operation.
VRF 시스템의 고효율 부하대응 열교환기 가변유로 기술에 관한 연구
장지영(JiYoung Jang),송치우(ChiWoo Song),윤필현(PhilHyun Yoon),사용철(YongCheol Sa) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
In this study, the latest heat exchanger technology to improve the performance of the VRF system is introduced. The heat exchanger is a key component in VRF system performance and in order to respond effectively to various loads, a technology has been developed that divides the heat exchanger into three passages through valve control and realizes optimal load-response operation by changing the flow passage. This technology enables bypass operation to respond to a small load under heating overload conditions, and prevents freezing of the lower end of the heat exchanger to supply continuous heating operation. In addition, it was possible to increase the operating efficiency by about 20% by changing the heat exchanger flow path during cooling and heating operation.