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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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 16, Issue 12 - Dec 2004
Volume 16, Issue 11 - Nov 2004
Volume 16, Issue 10 - Oct 2004
Volume 16, Issue 9 - Sep 2004
Volume 16, Issue 8 - Aug 2004
Volume 16, Issue 7 - Jul 2004
Volume 16, Issue 6 - Jun 2004
Volume 16, Issue 5 - May 2004
Volume 16, Issue 4 - Apr 2004
Volume 16, Issue 3 - Mar 2004
Volume 16, Issue 2 - Feb 2004
Volume 16, Issue 1 - Jan 2004
Selecting the target year
Off-Design Performance of a Plate Heat Exchanger : Analysis and Experiment
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 779~787
Design and off-design program is set up to analyze the performance of a plate heat exchanger. The program is verified by comparing the results with the experiment. The comparison shows that the predicted overall heat transfer coefficients are in good agreement with the measurements. Also the off-design performance according to the variations of inlet water temperature, flow rate, and the number of plates is analyzed to study the performance characteristic of a plate heat exchanger.
Experiment on the Cooling Characteristics of Protruding Heat Sources in a Channel
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 788~795
Cooling characteristics of protruding heat sources in a parallel channel with or without baffles are studied experimentally, The test section consists of two channels formed by two covers and one board made of polycarbonate which has three uniform heat source blocks. Five different cooling methods are considered to find out the most efficient cooling method in a given geometry and heat sources. The velocity and temperature of cooling medium, the temperature of the block surface are measured. The results are compared to examine the cooling characteristics of the different cooling methods.
Analysis of the Condenser Stack Effect in a High-Rise Apartment Building
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 796~803
The stack effect of a new type condenser installed in a high-rise apartment building was studied numerically A sirocco fan is introduced to the new type condenser instead of an axial flow In. The new type condenser intakes the cold air through the lower inlet and exhausts the hot air through the upper outlet. The effects of the building height and frontal wind on the performance of an air-conditioner were analyzed. The performance of an air-conditioner was evaluated by using COP (coefficient of performance) and CGPI (condenser group performance indicator). the hot air was exhausted by the new type condenser at an angle of 50
from the outer wall of the building. If there was no draft, the new type condenser installed in the high-rise apartment building had a good performance and its performance on each floor is not influenced by the stack effect. It is shown that the efficiency of the air-conditioner installed in several floors below the top floor decreased when the frontal wind velocity was greater than 8 m/s.
Numerical Study on the Turbulent Flow in the
Bends increasing Cross-sectional Aspect Ratio
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 804~810
This paper reports the characteristics of the three dimensional turbulent flow by numerical method in the 180 degree bends with increasing cross-sectional area. Calculated pressure and velocity, Reynolds stress distributions are compared to the experimental data. Turbulence model employed are low Reynolds number
model and algebraic stress model(ASM). The results show that the main vortex generated from the inlet part of the bend maintained to outlet of the bend and vortices are continually developed at the inner wall region. The distribution of turbulent kinetic energy along the bend are increase up to 120
because of increment of cross-sectional area. Secondary flow strength of the flow is lower about 60% than that of square duct flow.
Development of a Linearized Model and Verification of the Exact Solution for the Analysis of a Desiccant Dehumidifier
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 811~819
A silica gel desiccant dehumidifier is studied theoretically in this paper adopting several linearization assumptions. The governing equations are linearized with the assumptions, and the exact solutions to the temperature and the humidity ratio are obtained. In spite of the assumptions, the theoretical results are found to agree well with those from the numerical analysis without any assumption. In typical operation ranges of the desiccant dehumidifier, the time-averaged errors in the process air temperature and humidity ratio are less than 4% and 7%, respectively, and the corresponding root-mean-square values are less than 5% and 15%, respectively The analytical solutions are expected to contribute to the fundamental understanding of the dehumidification and regeneration processes and the correlation analysis of the numerous parameters influencing the dehumidifier operation.
Evaluation of a Propulsion Force Coefficients for Transportation of Wafers in an Air Levitation System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 820~827
The propulsion force acting on a wafer in an air levitation system was measured accurately and then, the corresponding force coefficient was determined. The theoretical propulsion force on the wafer bottom surface were obtained by CFD simulations and from these results the propulsion force coefficient was deduced. The transportation velocity of a wafer was estimated by using both experimental and numerical force coefficients, for various air velocity of nozzle injection. When the numerical results are compared to the experimental data, the numerical results agree well Quantitatively.
Two-Phase Flow Distribution, Phase Separation and Pressure Drop in Multi-Microchannel Tubes
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 828~837
The present study investigated two-phase flow distribution, phase separation and pressure drop in multi-microchannel tubes under adiabatic condition. The test section consisted of inlet and outlet headers with the inner diameter of 19.4㎜ and 15 parallel microchannel tubes. Each microchannel tube brazed to the inlet and outlet headers and had 8 rectangular ports with the hydraulic diameter of 1.32㎜. The key experimental parameters were orientation of header (horizontal and vertical), flow direction of refrigerant into the inlet header (in-line, parallel and cross flow) and inlet quality (0.1, 0.2 and 0.3). It was found that the orientation of the header had relatively large effect on the flow distribution and phase separation, while the inlet quality didn't affect much on them. The horizontal header showed the better flow distribution and phase separation characteristics than the vertical one. The parallel flow condition with the horizontal header showed the best performance for the flow distribution and phase separation characteristics under the test conditions. Two-phase pressure drops through the microchannel tubes with the horizontal header were higher than those of the microchennel tubes with the vertical header due to gravitational effect.
Dynamic Model of the Road Tunnel Pollution by Neural Networks
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 838~844
In a long road tunnel, a tunnel ventilation system may be used in order to reduce the pollution below the required level. To develop control algorithms for a tunnel ventilation system, a dynamic simulation program may be used to predict the pollution level in a tunnel. Research was carried out to develop better pollution models for a tunnel ventilation control system. A neural network structure was adopted and compared by using actual poilution data. Simulation results showed that the dynamic model developed by a neural network may be effective for the development of tunnel ventilation control algorithms.
Study on Evaporation Heat Transfer of R-l34a, R-407C, and R-410A in the Oblong Shell and Plate Heat Exchanger
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 845~854
The evaporation heat transfer coefficient for R-l34a, R-407C (a mixture of 23wt% R-32, 25 wt% R-125, and 52 wt% R-l34a) and R-410A (a mixture of 50 wt% R-32 and 50 wt% R-125) flowing in the oblong shell and plate heat exchanger were investigated experimentally in this study. Four vertical counterflow channels were formed in the exchanger by four plates of commercial geometry with a corrugated sinusoid shape of a chevron angle of 45 degree. The effects of the mean vapor quality, mass flux, heat flux, and saturation temperature of different refrigerants on the evaporation heat transfer were explored in detail. Similar to the case of a Plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. It is found that the evaporation heat transfer coefficient in the plates is much higher than that in circular pipes. The present data show that the evaporation heat transfer coefficients of all refrigerants increase with the vapor quality. At a higher mass flux h, is higher than for the entire range of the vapor quality. Raising the imposed wall heat flux was found to slightly improve h
, while h
is found to be lower at a higher refrigerant saturation temperature. A comparison of the performance of the various refrigerants reveals that R-410A has the highest heat transfer performance followed by R-l34a, and R-407C had the lowest performance of the refrigerants tested. Based on the present data, empirical correlations of the evaporation heat transfer coefficient were proposed.sed.
Study on Evaporation Pressure Drop of R- l34a, R-407C, and R-410A in the Oblong Shell and Plate Heat Exchanger
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 855~862
This study reports pressure drops during evaporation for R-l34a, R-407C (a mixture of 23 wt% R-32, 25 wt% R-125, and 52 wt% R-l34A) and R-410A (a mixture of 50 wt% R-32 and 50 wt% R-125) in the oblong shell and Plate heat exchanger. The effects of the mass fluxes, heat fluxes, refrigerant saturation temperatures and vapor quality of refrigerants on the measured data were explored in detail. The present data showed that pressure drops of all refrigerants increase with the vapor quality. At a higher mass flux, pressure drops are higher for the entire range of the vapor quality A rise in the heat flux doesn't show significant effects on the pressure drops. Finally, at a higher saturation temperature the pressure drops are found to be lower. The pressure drops for R-407C were approximately 20% lower than those of R-l34a. R-410A had 33% lower pressure drops than R-l34a. Correlation is also provided for the measured pressure drops in terms of the friction factor
Study on the Dissolution Characteristics of Liquid
Released by Fixed Pipeline
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 863~871
The use of fossil fuels like coal, oil and natural gases around the world causes an increase of the carbon dioxide content in the atmosphere. In order to reduce the concentration of the greenhouse gas, the idea of carbon dioxide sequestration in the ocean is proposed to be an effective mitigation strategy to counteract potential global warming due to the greenhouse effect. Therefore, in the present study, calculations of the dissolution behavior of carbon dioxide when liquid carbon dioxide is released at 1,000m and 1,500m in depth by fixed pipeline are performed. The results show that carbon dioxide droplets change to carbon dioxide bubbles in gas phase around 500m in depth, and the droplets are completely dissolved below 500 m in depth if the liquide carbon dioxide is released both at 1,000 m in depth with the initial diameter of 0.007m or less and at 1,500m in depth with the diameter of 0.011m or less.
An Experimental Study on the Rule Based Fault Detection and Diagnosis System for a Constant Air Volume Air Handling Unit
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 872~880
The fault detection and diagnosis technology may be applied in order to decrease the energy consumption and the maintenance cost of the air-conditioning system. In this study, an air handling unit fault test apparatus was built and fault diagnosis algorithms were applied to diagnose various faults of an air handling unit. Test results showed the good diagnosis for applied faults. Therefore, these algorithms may be effectively used to develope the real time fault detection and diagnosis system for the air handling unit.
Optimal Control Algorithm for the Dual Source Chiller Air Conditioning System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 9, 2004, Pages 881~888
Control algorithms for a dual source chiller air conditioning system were developed. These are control algorithms for the supply air temperature control, the supply header chilled water temperature control, the chiller chilled water temperature control, and the cooling tower water temperature control. These algorithms were analyzed by using a dynamic simulation program. Simulation results showed the energy savings and the satisfactory controls of an absorption and centrifugal chiller air conditioning system. Therefore, control algorithms developed for this study may effectively be used for the improved controls of the dual source chiller air conditioning system.