Thermosyphon의 가열량 증가시의 온도특성에 관한 연구

하옥남,박찬수,남동현 조선대학교 에너지.자원신기술연구소 2003 에너지·자원신기술연구소 논문지 Vol.25 No.1

The research is focused on the stability in which the incoming heat to the evaporator is in creased and transfer capability which is required in designing of a system. First, in case the incoming heat to the thermosyphon evaporator is increased and the quantity of operational fluid is less than the requirement, the surface temperature of evaporator increases, which can make the system abnormal and cause damage to the system to be out of order. Therefore, the aim of this research is to study the characteristics in which the heating amount of the thermosyphon is increased.

NH3 냉동장치의 과열도 변화에 의한 성능 특성 연구 II

하옥남,권일욱,전상신,이승재,정송태,하경수,윤갑식,이종인,홍경한 대한설비공학회 2005 설비공학 논문집 Vol.17 No.4

Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the NH3 gas to study the performance characteristics of NH3 refrigeration system by the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for degree of superheat from 0℃ to 10℃ at each condensing pressure. As a result of experiment, when the degree of superheat is 0℃ at each condensing pressure, the refrigeration system has the highest performance.

NH3와 R22를 사용한 냉동장치의 성능특성 비교

하옥남,이규태,하경수,정송태,김진현,홍성인,윤갑식,김양현,권일욱,이종인 대한설비공학회 2006 설비공학 논문집 Vol.18 No.5

Recently, production and use of Freon substances are restrained due to destruction of ozone layer and grobal warming. In this aspect of environmental problems, the best solution is to use the natural refrigerant such as ammonia. Thus, this study 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 1,500kPa to 1,600kPa 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.

R-134a와 R-407C를 이용한 자동차 에어컨 성능평가에 관한 연구

하옥남,윤갑식 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.1

HFC-134a is currently used as the refrigerant in motor vehicle air-conditioner, replacing the ozone depleting refrigerant CFC-12. Although HFC-134a has no ozone depletion potential, it has a relatively large global warming potential, approximately 1300 times that of CO_2 over a 100 year time horizon. Therefore, HFC-134a does not seem to be a perfect alternative refrigerant due to high GWP. For this reason, non-azeotropic refrigerant mixtures are expected to propose as a long-term and drop-in alternative to HFC-134a in the automobile air-conditioning system which has a variable operating conditions as a changes of RPM and pressure ratio. In this study, HFC-407C of which thermodynamic properties are similar to those of HFC-134a is selected among the non-azeotropic refrigerant mixtures. HFC-134a and HFC-407C were examined experimently by the performance test in the same automobile air-conditioning system.

열교환기 구조 변화에 따른 NH₃와 R22의 성능특성연구

하옥남,하경수,이승재,정송태 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-

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.

NH₃와 R22를 작동유체로 사용한 냉동장치의 성능특성 비교에 관한 연구

하옥남(Ok-Nam Ha),정송태(Song-Tae Jeong),이승재(Seung-Jae Lee),하경수(Kyeong-Soo Ha) 대한설비공학회 2005 대한설비공학회 학술발표대회논문집 Vol.2005 No.6

分岐管內 글리세린 수용액의 流動 特性

하옥남,이행남,이종인,윤치한 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

본 연구에서는 글리세린 수용액(45%)을 사용하여 2차원 분기관 유로의 정상 층류에서의 분기부의 유동 상태를 알아보기 위하여 레이놀즈 수, 분기 각도, 유량 분배비등이 손실 계수에 미치는 영향을 실험으로 구하고, 다음과 같은 결론을 얻었다. 레이놀즈 수 100을 기준으로 하여 100 이하에서 T형과 Y형의 값은 직선적으로 감소하고, 유량 분배비의 영향은 적으며, 100 이상에서는 유량 분배비에 따라 거의 일정한 값, 즉 본관에서는 0.3∼1.3 지관에서는 1.70∼2.45의 수치에 접근한다. 그러나, 분기각의 영향은 레이놀즈 수 100 이하에서는 크지만, 100 이상에서는 매우 적어서 일정한 값, 즉 본관에서 액 0.9, 지관에서 약 1.8의 값을 갖는다. The purpose of this research is to study the characteristics of the dividing flow in the laminar flow region. Using glycerine-water solution(45%) for Newtonian fluid, this research investigates the flow state of the dividing tube in steady laminar flow region of the two dimensional dividing tube by measuring the effect of Reynolds number, dividing angle, and the flow distribution ratio on the loss coefficient. The results of the research is as follows. In T-type and Y-type tube, the loss coefficient of the glycerine-water solution decreases in constant rate when the Reynolds number is below 100. The effect of the flow distribution rate is negligible. But when the Reynolds number is over 100. the loss coefficient as to the flow distribution rate converges to a constant value. In the main tube the value lies in the range of 0.30-1.30. In the lateral tube the value lies in the range of 1.7-2.45. The effect of the dividing angle is considerable when the Reynolds number is below 100. But it is very small and converges to a constant value when the number is over 100: in the main tube approximately 0.9, and 1.8 in the lateral tube.

축냉재 포접화합물의 열물성에 관한 실험적 연구(Ⅱ) : 충전량 변화 Variations of Charging Conditions

김진흥,정낙규,고강옥,임재경,하옥남 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

본 연구에서는 에너지의 합리적 이용을 위한 건물공조용 축냉시스템에 적용 가능한 축냉재로서 TMA-물계 포접화합물의 농도와 충전량의 변화에 따른 상변화온도, 비열 및 과냉도 실험을 통하여 다음과 같은 결론을 얻었다. 1. 충전량이 많을수록 전 실헐과정에서 열물성의 안정성이 높게 나타났다. 2. TMA-물계 포접화합물의 비열은 순수한 물에 대하여 86% ∼ 96% 정도를 나타내었다. 위의 실험결과로부터 TMA-포접화합물은 건물공조용 축냉재로서의 열물성을 갖는다고 판단된다 The objective of this Paper is to investigate the thermal properties of TMA-clathrate compound applicable to cold storage system for residential air-conditioning in order to use energy reasonably. Especially, the test tube experiments are performed to compare and analyze the concentration of TMA-clathrate compound, the temperature of heat source, and the phase change temperature, specific heat and subcooling characteristics according to the variation of charge capacity. The result is summarized as follows: the phase change temperature appears higher as the charge capacity is larger. Thus, it appears that TMA-clathrate compound has thermal properties as the cold storage medium for residential air-conditioning.

R22/R114 혼합냉매의 수평증발관내 강제대류 전열특성에 관한 연구

하옥남,윤치한,이종인 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.1

It was studied on the heat transfer characteristic of forced convection in horizontal tube using the pure refrigerant and non-azeotropic refrigerant mixture, and compared the heat transfer coefficient. The inside wall temperatures and the heat transfer coefficients of horizontal evaporation tube were obtained from the experiments using the pure refrigerant, R22 and R114, and the non-azeotropic refrigerant mixture, R22/Rl14. In case of the pure refrigerant R114, with increasing the quality, the local heat transfer coefficient of bottom of the tube was the highest value without being influenced by flow rate. In case of the pure refrigerant R22, in the low flow rate region the local heat transfer coefficient of bottom of the tube were the highest, and these were decreased as quality was increased, and in the high flow rate region the reverse results were obtained. In case of the refrigerant mixture, the local heat transfer coefficient of the bottom of tube were the highest regardless of flow rate. Two phase convection heat transfer coefficients of 76mol%R22-24mol%R114 refrigerant mixture were lower about 20% than these of Chen's.

低壓에서 均一過熱 水中에 있어서 氣泡發生에 關한 考察

河鈺男,洪明錫,吳栗權 조선대학교 동력자원연구소 1984 動力資源硏究所誌 Vol.6 No.2

Fer liquid temperature range from 40℃ to 80℃ which is related to flash evaporation, the experimentals were conducted the bubble occurences of superheated water in The conditions of constant circumference pressures by changing the degrees of superheat and liquid temperatures schematically and compared with numerical methods. (1) The ratios of radius, R_1/R_2 were not related to the degrees of superheat, but effected by water column pressures. (2) In the liquid temperature range from 55℃ to 75℃, the values of experimental and those of numerical were well agreed but for the liquid ranges from T=40℃ and the values of experimental were the lower than those of numerical with the lowering the liquid temperatures.