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李行男(Haeng-Nam Lee),河鈺男(OK-Nam Ha),全雲鶴(Un-Hack Chun) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.4
Flow patterns of fluid flow in dividing tube were visualized, and the energy losses due to dividing were measured in laminar dividing flow of the viscoelastic fluid and its solution in tube junctions with dividing angles of 90℃, 60℃, 45℃ and 15℃. Two separation zones were observed. swelling of the streamline to the main tube or to the lateral tube was observed. The sizes of the separation zones depend on the Reynolds number, the dividing angle and the dividing flow rate. The energy loss coefficients decrease with increasing Reynolds number, but their decreasing rate decreases with increasing Reynolds number as the sizes of the separation zone increase. The effect of dividing angle on the energy loss coefficients and separation is greater for the main tube than for the lateral tube.
암모니아와 프레온을 사용한 냉동장치의 성능에 관한 연구
이승재(Seung-Jae Lee),하옥남(Ok-Nam Ha),정송태(Song-Tae Jeong),하경수(Kyeong-Soo Ha) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Nowadays HCFCs refrigerant are restricted because it cause depletion of ozone layer. However, natural gases such as ammonia as an organic compound, propane and propylene as hydrocarbon are easy and cheap to obtain as well as environmental. Accordingly, this experiment apply the NH3 and R22 to study the performance characteristic from the superheat control and compare the energy efficiency of two refrigerants from the high performance. The condensing pressure of refrigeration system is increased from 15bar to 16bar and degree of superheat is increased from 0 to 10℃ at each condensing pressure. As the result of experiment, when comparing the each COP, we knew the NH3 is suitable as the alternative refrigerant of the R22.
[열유체부문] HFC-152a와 HFC-152a에 CF₃I를 혼합한 공비혼합냉매의 특성
이종인(Jong-In Lee),하옥남(Ok-Nam Ha),홍경한(Kyoung-Han Hong),최운수(Woon-Soo Choi),권일욱(Il-Wook Kwon),박찬수(Chan-Soo Park) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_1
These days, an attention of environment has been increasing allover the world. To prevent green house effect and destruction of an ozone layer, an ozone destruction potential(ODP) must be zero and a refrigerant for low global warming potential(GWP) is needed. HFC-134a. in which hydrogen is mixed instead of chlorine is a refrigerant used for automobile conditioners and its destruction potential is ecologically zero. However, it is not considered as a perfect substitutive refrigerant as its GWP is high. It is studied refrigerant mixtures in which HFC-152a, HFC-152a and CF31 with low GWP and zero ODP are mixed by experimentally and concluded as follows: 1) With the variation of speed of compressor outside temperature and flow rate, the heat of evaporator and compressor and coefficient of performance was varied. and influenced the air conditioner. 2) The pressure of evaporator was decreased with increasing the speed of compressor and the pressure of evaporator with the refrigerant HFC-152a was higher 24% than that of azotrope refrigerant. mixed with CF31<br/> <br/>