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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Korean Journal of Air-Conditioning and Refrigeration Engineering
Journal Basic Information
Journal DOI :
The Society of Air-Conditioning and Refrigerating Engineers of Korea
Editor in Chief :
Volume & Issues
Volume 13, Issue 12 - Dec 2001
Volume 13, Issue 11 - Nov 2001
Volume 13, Issue 10 - Oct 2001
Volume 13, Issue 9 - Sep 2001
Volume 13, Issue 8 - Aug 2001
Volume 13, Issue 7 - Jul 2001
Volume 13, Issue 6 - Jun 2001
Volume 13, Issue 5 - May 2001
Volume 13, Issue 4 - Apr 2001
Volume 13, Issue 3 - Mar 2001
Volume 13, Issue 2 - Feb 2001
Volume 13, Issue 1 - Jan 2001
Selecting the target year
하이브리드 GAX 사이클 해석 : 성능향상 및 저온획득 응용
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 923~929
The objectives of this paper are to develop an advanced GAX cycle named HGAX (Hybrid Generator Absorber heat eXchange) cycle, and to study the effect of key pa-rameters on the cycle performance and the evaporating temperature. Two different HGAX cycles are developed-Type A (Performance improvement) and Type B (Low temperature applications). A compressor is placed between the evaporator and the absorber, and the evaporator pressure and the absorber pressure are controlled according to its application purpose. It was found that the COP could be improved by 24% compared with the conventional GAX cycle and the evaporating temperature as low as -8
could be obtained from the HGAX cycle.
판각형 열교환기 내의 R-22 증발 압력강하 특성에 관한 실험적 연구
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 930~938
In this study, evaporation pressure drop experiments were conducted with two types of plate and shell heat exchangers (P&SHE) using R-22. An experimental refrigerant loop has been established to measure the evaporation pressure drop of R-22 in a vertical P&SHE. The flow channels were formed by adding three plates having a corrugated channel of a chevron angle of
. The R-22 flows down in one channel exchanging heat with the hot water flowing up in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality were explored in detail. During the experiment, the quality change between the inlet and outlet of the refrigerant channel ranges from 0.03 to 0.15. The present data showed that two types of P&SHE have similar trends. The pressure drop increases with the vapor quality for both types of P&SHE. At a higher mass flux, the pressure drop is higher for the entire range of the vapor quality. Also, the increase in the average heat flux increases the pressure drop. Finally, at a higher system pressure, the pressure drop is found to be slightly lower.
광폭 전기집진기의 집전특성에 관한 연구 - I. 집진판 간격과 방전극의 영향 -
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 939~946
This study investigates the electrical and collection characteristics of a wide plate spacing electrostatic precipitator (ESP), using a pilot-scale one. Electrical operating characteristics and collection efficiency were measured for various shapes of discharge electrodes. The collection plate spacing ranged from 300 to 550 mm. Results of electrical characteristic and collection efficiency tests as a function of collection plate spacing, discharge electrode type, applied voltage, and particle diameter were obtained. Increasing the collection plate pitch and altering the corona electrode geometry was found to increase the collection efficiencies without increasing input power requirement. The best efficiency is achieved for the discharge electrode of twisted pin type.
가변 풍량 유닛에 의한 실내 공간의 온도제어를 위한 공간의 분할 모델과 상태궤환 제어기의 개발에 관한 연구
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 947~959
We propose a control scheme to control the indoor zone temperature via variable air volume (VAV) unit. To control the room temperature, state space model of the conditioned zone which is partitioned into nine artificial sectional regions is derived. The nonlinearity of the damper motion and actuator are considered for the practical use in the state space system description. The temperature control of the room temperature is performed by manipulating the degree of openness of the damper in relation to the local room temperature and the supplied air flow rate. In general, since a local temperature in the conditioned zone is measured, it is required to estimate the temperature values in each regions for the precise temperature control. We thus design a state observer to estimate the regional temperature, and use these values in the controller. The overall control system consists of the state observer based state feedback with the integral control. We compared the control results of the proposed scheme with those of cascade proportional and integral (PI) control, and showed that the scheme achieved precise control of the conditioned system.
액막류의 MHF점에 관한 실험적 연구
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 960~965
The minimum heat flux conditions are experimentally investigated for the subcooled liquid film flow on the horizontal plate. The experimental results show that the minimum heat flux point temperature becomes higher with the increase of the velocity and the subcooling of the liquid film flow. However, the effect of distance from the leading edge of the heat transfer plate on the minimum heat flux is almost negligible. Also, the experimental results show that the propagation velocity of wetting front increases with increasing the velocity and the subcooling of the liquid film flow.
클린룸과 실험실이 있는 사무용 건물의 에너지 소비 실태 측정 및 분석
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 966~973
In this study, measurement and analysis of energy consumption of an office building with cleanroom and laboratory have been conducted. Data acquisition system for collecting energy consumption data of the whole building including air-conditioning equipments has been installed in a building located in Seoul. Data are collected for a period of one year in 2000 and analyzed for studying the energy consumption pattern. The percentage of electrical energy used for air-conditioning system is measured to be 46.1%. The collected data will serve as valuable information for diagnosing and improving the energy system of the building.
Study on Minimum Heat Flux Point in Spray Cooling of Hot Plate
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 974~981
In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about
, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the velocity of wetting front increases with the increase of the droplet flow rate.
분배계통에 따른 지하주차장 환기설비 성능의 예측
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 982~992
In this paper, the performance of ventilation equipments in enclosed parking garages were investigated for several air distribution systems by numerical method. Air change effectiveness of the non-mixing system was 0.42. It meant that more supply air as much as the design supply air was needed to maintain good indoor air quality. In the high speed nozzle ventilating system which is most expensive one, air change effectiveness was 0.54. Therefore this system satisfied to ventilation design. In the jet fan ventilating systems, air change effectiveness for jet fan ventilating system-A with 18 jet fans and jet fan ventilating system-B with 6 jet fans in circulation mixing arrangement were 0.565 and 0.42 respectively. Jet fan ventilating system-C with 6 jet fans in transport mixing arrangement was 0.535. Jet fan ventilating system-A and jet fan ventilating system-C met the ventilation design. But velocity in jet fan ventilating system-A was over 2.0m/s which is inappropriate in human comfort. Therefore this system is not proper to ventilation. Jet fan ventilating system-C was the optimum one for enclosed parking garages among 5 systems examined in this paper.
이젝터가 부착된 냉동시스템의 성능실험
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 993~1001
Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were performed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one evaporator) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flaw rate ratio of suction fluid to motive fluid increases. The COP of dual-evaporator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.
20kw급 해양온도차 파이롯 플랜트 성능실험
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1002~1008
The energy is the basis for almost all industrial activities and domestic needs. But recently there are increasing concerns internationally over environmental problems and consequent climate changes caused by the excessive use of fossil fuels. Furthermore the price of crude oil is increasing steadily with unstable supplies. In order to solve these national energy problems, the utilization of Ocean Energy is introduced as one of the best alterative technologies for the future. OTEC Power Plant has been installed at the West Inchon Power Plant Site. Temperature differences of
been utilized for plant operations, where R22 is used as a working fluid. The system is composed of low pressure turbine, plate type heat exchanger, and pumps. In the present investigation the experimental results, such as gross power, net power and objective function, are analysed when temperature differences change from the reference design point.
삼각형상 그루브 채널에서 맥동유동에 의한 열전달 향상에 관한 실험적 연구
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1009~1016
The heat transfer enhancement by pulsatile flow in a triangular grooved channel has been experimentally investigated in this study The experiment was performed in the ranges of the Reynolds number from 270 to 910, the pulsatile fraction from 0.125 to 0.75, and the Strouhal number from 0.084 to 0.665. It was measured that the heat transfer improves up to 350% compared with the steady flow case at Re=270,
, and St=0.335. The heat transfer enhancement was found to increase as the pulsatile fraction increases and the Reynolds number decreases. It was also found that the heat transfer enhancement is maximized at a specific pulsatile frequency satisfying the resonant condition. The nondimensional frequency, i.e., the Strouhal number at the resonant condition was found to increase as the Reynolds number decreases. The flow visualization revealed that the heat transfer enhancement results from the strong mixing caused by the repeating sequence of vortex formation, rotation and subsequent ejection from the grooves by the pulsatile flow.
평행류 열교환기의 헤더부 형상 최적화
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1017~1024
The optimum shape of header part in a PFHE (parallel-flow heat exchanger) is studied. The optimal values of each geometric parameter are proposed according to their order of influence with varying the four important parameters (the injection angle of working fluid (
), the shape of inlet(S), the location of inlet (
) and the height of the protruding flat tube (
)). The optimal geometric parameters are as follows:
/=0. The heat transfer rate of the optimum model, compared to that of the reference model, is increased by about 55%. The optimal geometric parameters ran be applicable to the Reynolds number ranging from 5,000 to 20,000.0.
경사진 고체 표면 위를 내려가는 액적의 미글림 유동
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1025~1033
A scaling analysis is provided which predicts the sliding velocity of a liquid drop down an inclined surface. The analysis is based on the balance of the gravitational work rate that drives the drop sliding and the resistances by capillary and viscous forces. The capillary resistance is accounted for via the contact angle hysteresis, which is quantified by measuring the critical inclination causing the drop to start sliding. The sliding of the drop is governed by the rate of the viscous dissipation of the Stokes flow. The analysis result in its limit form for small contact angles is consistent with previous results. In the experiments to verify the analysis results, the measured sliding velocity of various liquid drops are shown to obey the predictions made in this study.
암모니아/물 흡수식 냉동기의 대향류 판형 재생기의 수치모델
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1034~1041
A numerical model which simulates the flow boiling process of the ammonia/water solution within a plate type generator for ammonia/water absorption refrigerators was developed. The ammonia/water solution flows downward under gravity and the ammonia/water vapor generated by flow boiling flows upward. The heating medium flows counter to the ammonia/water solution. The flow pattern within the generator was assumed to be a bubbly flow, and the liquid and vapor phases were assumed to be saturated. It was shown that the boiling of ammonia occurred mainly in the upper part of the generator. The effects of the heating medium inlet temperature, the mass flow rate of the heating medium and the mass flow rate of ammonia/water solution into the generator on the generation of ammonia/water vapor were investigated.
A Study of Rivulet Flow on an Inclined Solid Surface
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 10, 2001, Pages 1042~1048
When a liquid is supplied through a nozzle onto a relatively non-wetting inclined solid surface, a narrow rivulet forms. This work provides novel physical insights into the following phenomena in the rivulet flow that have not been well understood to date. Firstly, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the axial velocity of a liquid is slower than the retraction velocity of its thread, the bifurcation of the liquid thread occurs, and this argument is experimentally verified. Secondly, a discussion on the curled motion of a meandering rivulet is given. This study proposes the contact angle hysteresis as a primary origin of the centripetal force that enables the rivulet\`s curved motion. A simple scaling analysis based on this assumption predicts a radius of curvature which agrees with the experimental observation.