운전조건에 따른 멀티-히트 펌프의 신뢰도에 관한 연구

이상재,전용호,박종운,김영재,장근선,권영철 선문대학교 2001 공학계열 논총 Vol.4 No.-

본 연구의 목적은 두 실내공간을 가변적으로 냉난방하기 위해 모세관을 이용한 2실 히트펌프를 개발하는 것이다. 멀티형 히트펌프의 다양한 부하변동을 극복할 수 있는 새로운 냉매 회로를 구성하기 위해 전자팽창 밸브와 여러 개의 모세관을 조합한 냉매 제어회로를 설계하였다. 모세관을 이용한 냉매 제어회로를 구성하여 한 대의 압축기로 각기 다른 용량대의 두 공간을 제어할 수 있는 2실 멀티형 히트펌프의 성능 및 신뢰도를 평가하고자 고성능 멀티 칼로리미터를 사용하였다. 정격시험을 통해 얻어진 멀티형 히트펌프의 냉난방능력은 설계기준의 약 93% 정도를 그리고 냉방시험에서는 단독시험이 설계기준의 약 13%정도, 난방시험에서는 동시시험 시 설계기준의 약 5%정도가 향상되었다. In order to develop the multi-heat pump system for two zones with different capacity, the optimum refrigerant control circuit using capillary tubes was designed. The system characteristics of multi-heat pump was investigated from the rating test and the reliability test, by using the multi-calorimeter with a high performance. The results of the rating test showed that the capacity of the multi-heat pump system satisfied about 93% of the design value. In particular, the capacity of cooling single mode increased about 13% and the capacity of heating multi mode increased about 5%, compared to the design value. And the rating refrigerant, the compressor capacity and the accumulator capacity for the multi-heat pump were obtained.

전열촉진관 내부 비등열 전달에 미치는 전기장의 효과

이윤수,김대훈,박종운,김영재,장근선,권영철 선문대학교 2001 공학계열 논총 Vol.4 No.-

본 연구는 전기장에 의한 전열촉진관내 유동비등 열전달 현상을 이해하기 위해 수행되었다. 이를 위해 전기장이 인가되지 않았을 때와 전기장이 인가되었을 때의 R-22를 작동유체로 하는 마이크로핀관 내의 비등 열전달계수 및 압력강하들 조사하였다. 실험변수들로 시험부 입구건도, 질량유속, 열유속, DC 고전압을 선정하였고, 시험부내 증발온도는 5℃로 고정시키고 실험을 수행하였다. 본 실험을 통하여. 저건도 영역에서 유동비등의 열전달촉진에 대한 전 기장의 효과로 비등 열전달계수가 전기장이 인가되지 않은 경우에 비해 뚜렷이 증가함을 알 수 있었다. 관내의 압력강하는 거의 선형적으로 증가하였으며, 관내 압력강하 효과는 전기장 하에서 더 크게 관찰되었다. An experimental study on boiling heat transfer characteristics in a micro-fin tube has been performed. The micro-fin tube with outer diameter of 9.56 mm were used as test section, and it was heated by applying hot liquid to the test tube. The working fluid was R-22 and the tube-circular electrode system was used. The DC voltage was applied to the circular electrode, while the tube was grounded. The present study shows the enhancement of the boiling heat transfer coefficient of the tube is largely increased under the high voltage, compared with that of the normal condition(zero voltage). It is found at low inlet quality condition that the mechanisms of EHD in-tube boiling are closely connected with the dynamic behavior of bubbles. With increasing the mass flux and inlet quality, the pressure drop in a micro-fin tube increases linearly.

Study on Laminar Heat Transfer Enhancement by Twisted - Inserts

Young-Chel Kweon,Keun-Sun Chang,Ji-Hwan Jeong 대한설비공학회 2001 International Journal Of Air-Conditioning and Refr Vol.9 No.2

In order to understand the laminar heat transfer enhancement by swirl flow, the effects of heat transfer in a circular pipe with twisted inserts are investigated experimentally. In the present study, a uniform heat flux condition is considered. Laminar heat transfer correlations are developed using least square fit method from surface temperature distributions of an electrically-heated pipe and flow properties. Average Nusselt number correlations with twisted inserts are expressed as a function of swirl parameter, Reynolds number and Prandtl number. When the twisted ratio is 6.05, mean Nusselt number and friction factor increase by approximately 500% and 300%, respectively, compared with the values for a pipe without inserts.

핵비등에서 기포의 동특성에 대한 전기장의 효과

권영철(Young Chel Kweon),장근선(Keun Sun Chang),권정태(Jeong-Tae Kwon),김무환(Moo Hwan Kim) 대한설비공학회 2000 설비공학 논문집 Vol.12 No.11

In order to investigate the effects of an electric field on EHD (Electro-hydrodynamic) nucleate boiling heat transfer characteristics in a nonuniform electric field under saturated pool boiling, the basic study has been performed experimentally. In the present study, the working fluid is R-113 and the plate-wire electrode system is used to generate a steep electric field gradient. Boiling parameters are investigated by using a high speed camera. The electric field distribution around a wire is obtained to understand the effect of an electric field on bubble departure/movement. The experimental results show EHD effects are much more considerable when the applied voltage increases. Bubbles depart away from the heated wire in radial direction. It is confirmed that the mechanisms of EHD nucleate boiling are closely connected with the dynamic behavior of bubbles. The boiling parameters are significantly changed by the electric field strength. With increasing applied voltages, the bubble size decreases and the nucleation site density, bubble velocity and bubble frequency increase.

3-D LDV 시스템을 이용한 3차원 난류구조 해석

권영철(Young-Chel Kweon),이상준(Sang-Joon Lee) 한국항공우주학회 1991 韓國航空宇宙學會誌 Vol.19 No.2

Effects of an electric field on the dynamic characteristics of bubbles in nucleate boiling

권영철,장근선,권정태,김무환 대한설비공학회 2000 설비공학 논문집 Vol.12 No.11

In order to investigate the effects of an electric field on EHD (Electro-hydro-dynamic) nucleate boiling heat transfer characteristics in a nonuniform electric field under saturated pool boiling, the basic study has been performed experimentally. In the present study, the working fluid is R-113 and the plate-wire electrode system is used to generate a steep electric field gradient. Boiling parameters are investigated by using a high speed camera. The electric field distribution around a wire is obtained to understand the effect of an electric field on bubble departure/movement. The experimental results show EHD effects are much more considerable when the applied voltage increases. Bubbles depart away from the heated wire in radial direction. It is confirmed that the mechanisms of EHD nucleate boiling are closely connected with the dynamic behavior of bubbles. The boiling parameters are significantly changed by the electric field strength. With increasing applied voltages, the bubble size decreases and the nucleation site density, bubble velocity and bubble frequency increase.

디지털 스크롤 압축기를 적용한 시스템 에어컨의 냉난방특성에 대한 실험적 연구

전용호(Young Ho Jun),김대훈(Dae Hun Kim),권영철(Young Chel Kweon),장근선(Keun Sun Chang),이윤수(Yun Su Lee),문제명(Je Myung Moon),윤백(Youn Baek),홍주태(Ju Tae Hong) 대한설비공학회 2003 설비공학 논문집 Vol.15 No.6

In order to investigate the cooling and heating characteristics of a variable-capacity system A/C applying a digital scroll compressor, the cooling and heating capacities and COP are measured by the psychrometric calorimeter. The capacity of the system is controlled by the digital scroll compressor, which is operated by controling PWM valve and the loading vs. unloading time. In the case of unloading compared that of loading, the consumption power of the compressor is about 11% and the capacity variation of the system A/C is within about 1%. When the system A/C is operated under the cooling and heating standard conditions, COP is nearly uniform but cooling capacity and heating capacity increase at minimum, rated and maximum modes. The system A/C applying the digital scroll compressor is effective for the range with high load or the width of large load variation. When the auxiliary heater is on, at the cold region, the system A/C produces the excellent heating capacity.

디지털 스크롤 압축기를 이용한 시스템 에어컨의 냉난방특성

전용호(Young Ho Jun),김대훈(Dae Hun Kim),권영철(Young Chel Kweon),이윤수(Yun Su Lee),문제명(Je Myung Moon),홍주태(Ju Tae Hong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

In order to investigate the cooling and heating characteristics of a variable-capacity system A/C using<br/> a digital scroll compressor, the cooling and heating capacities and EER are measured by the<br/> psychrometric calorimeter. The capacity of the system is controlled by the digital scroll compressor,<br/> which is operated by controling PWM valve and the loading vs. unloading time. When the system A/C<br/> is operated under the cooling and heating standard conditions, EER is nearly uniform but cooling<br/> capacity and heating capacity increase at minimum, rated and maximum modes. When the auxiliary<br/> heater is on, at the cold region, the system A/C produces the excellent heating capacity.

A Numerical Analysis on the Transient Heat Transfer in a Heat Exchanger Pipe Flow

Chang, Keun-Sun,Kweon, Young-Chel,Jin, Seong-Ryung Korean Nuclear Society 2000 Nuclear Engineering and Technology Vol.32 No.1

Numerical results are presented for the 2-dimensional turbulent transient heat transfer of the shell/tube heat exchanger with a step change of the inlet temperature in the primary side. Heat transfer boundary conditions outside the pipe are given partially by the convection heat transfer conditions and partially by insulated conditions. Calculation results were obtained by solving the unsteady two-dimensional elliptic forms for the Reynolds-averaged governing equations for the mass, momentum and energy. Finite-difference method was used to obtain discretization equations, and the SIMPLER solution algorithm was employed for the calculation procedure. Turbulent model used is the algebraic model proposed by Cebeci-Smith. Results presented include the time variant Nusselt number distribution, average temperature distribution and outlet temperatures for the various inlet temperatures and flow rates.

Variations in the Thermal Performance of R22 and R410A Refrigeration Systems Depending on Operation Conditions

Jeong, Ji-Hwan,Kweon, Young-Chel,Chang, Keun-Sun The Society of Air-Conditioning and Refrigerating 2004 International Journal Of Air-Conditioning and Refr Vol.12 No.1

Experiments have been conducted in order to make comparisons of characteristics of a R410a cycle with a R22 cycle in terms of cooling capacity and coefficient of performance (COP). The parameters examined in the present work include air flow rate, indoor and outdoor air temperatures, and indoor relative humidity. These two refrigeration cycles constructed for this study share all components except compressor, accumulator, oil separator, and piping. The measurements were made using a psychrometric calorimeter. The experimental results show that the R410A cycle has several advantages for indoor units while the R22 cycle yields better performance for outdoor units.