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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 15, Issue 12 - Dec 2003
Volume 15, Issue 11 - Nov 2003
Volume 15, Issue 10 - Oct 2003
Volume 15, Issue 9 - Sep 2003
Volume 15, Issue 8 - Aug 2003
Volume 15, Issue 7 - Jul 2003
Volume 15, Issue 6 - Jun 2003
Volume 15, Issue 5 - May 2003
Volume 15, Issue 4 - Apr 2003
Volume 15, Issue 3 - Mar 2003
Volume 15, Issue 2 - Feb 2003
Volume 15, Issue 1 - Jan 2003
Selecting the target year
Performance Evaluation of a Parallel Flow Condenser for Automotive Air Conditioners
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 247~253
The new shape of louver-fin has been applied to a parallel flow condenser to enhance air-side heat transfer rate lot an automotive air-conditioner R- l34a is employed as a refrigerant inside the flat tube of the condenser, This problem is of particular interest in reducing the geometric size of the automotive air conditioner The effect of air flow rate on pressure drop as well as heat transfer in air side are studied in detail. Comparison of the performance is also made with that of a conventional parallel flow condenser, which is available in the market. The results obtained indicate that the total pressure drop through the pre sent condenser is not changed, while the heat transfer rate is increased by 24% at high veto city of air flow, compared with those of the conventional condenser. The parallel flow condenser with a new shape of louver-fin could be reduced in size by 20% for the equivalent condenser capacity, compared with the conventional parallel flow condenser.
Hysteresis on Boiling Heat Transfer at Low Temperature on Enhanced Tubes in a Flooded Evaporator
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 254~260
The boiling characteristics for R134a are studied to clarify the hysteresis at low temperature on enhanced tubes of a flooded evaporator. Initial boiling conditions, refrigerant temperature, and inlet temperature of the chilled water are considered as the key parameters of the experiments. Unlike previous studies of the boiling heat transfer with uniform heat flux and uniform wall temperature, the wall temperature was varied along the tube. In, this study, it was found that the hysteresis of the temperature overshoot (705) at the onset of nucleate boiling initially at the inlet section of the tube. It is also concluded that the abnormal operation can be avoided during the low temperature boiling if the refrigeration system is started with LMTD larger than
at initial stage and larger than
at normal stage.
A Study on the Fire Suppression Characteristics Using a Water Mist
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 261~267
The present study investigates the fire suppression characteristics using a water mist fire suppression system. Numerical simulations of fire suppression with water mist are performed with considering the interaction of fire plume and water droplet, droplet evaporation, and combustion of pool fire. The predicted temperature fields of smoke layer are compared with that of measured data. Numerical results agree with the experimental results within 5
in the case without water mist In the case of fire suppression with water mist, numerical results dose not predict well lot temperature field in the gradual cooling region after water mist injection. But the predicted results of initial fire suppression are in good agreement with that of measured data. The reason of the discrepancy between predicted and measured data is due to the variation of turning rate during the injection of water mist. The effect of burning rate on the fire suppression is left as future study.
A Study on the Characteristics of Two-Phase Flow by Driven Bubbles
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 268~273
In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas is concentrated at the near nozzle, the flow parameters are high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (P.I..V) and a thermo-vision camera were used in the present study. The experimental results show that heat transfer from bubble surface to water is largely completed within z=10mm from the nozzle, and then the temperature of bubble surface reaches that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.
Development of a New Correlation for the Heat Transfer Coefficient of Turbulent Supercritical Carbon Dioxide Flow
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 274~286
Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.
Effect of Measuring Period on Predicting the Annual Heating Energy Consumption for Building
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 287~293
This study examined the temperature-dependent regression model of energy consumption based on various measuring period. The methodology employed was to construct temperature-dependent linear regression model of daily energy consumption from one day to three months data-sets and to compare the annual heating energy consumption predicted by these models with actual annual heating energy consumption. Heating energy consumption from a building in Daejon was examined experimentally. From the results, predicted value based on one day experimental data can have error over 100%. But predicted value based on one week experimental data showed error over 30%. And predicted value based on over three months experimental data provides accurate prediction within 6% but it will be required very expensive.
Effect of Blade Loading on the Structure of Tip Leakage Flow in a Forward-Swept Axial-Flow Fan
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 294~304
An experimental analysis using three-dimensional laser Doppler velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition (
=0.25) and two off-design conditions (
=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at
=0.30, but it is not observed at
=0.21 and 0.25.
An Experiment on the Particle Collection Characteristics in a Packed Wet Scrubber
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 305~311
DOP aerosol particles with geometric mean diameter of 0.5-3.0
, geometric standard deviation of 1.1-1.3 and total number concentration of 1,500-8,000 Particles/㎤ were used to determine collection efficiencies of a packed wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. Meanwhile, as for the particle size variation, all of the collection efficiency curves increased rapidly between 0.57-1.41
for the range of water injection rate above 30 L/min. It was also seen that the collection efficiency of a packed wet scrubber is mainly governed by the mechanism of inertial impaction.
Experimental Investigation on Small-scale Sorption Refrigerator
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 312~317
This paper describes an experimental study on small-scale sorption refrigerator. Silica gel (type A) as an adsorbent, HFC-l34a as a refrigerant were selected for a sorption refrigerator The focus of the design was to reduce the cycle time of the sorption refrigerator. Through the experiment, pressure and temperature variations in the adsorber were measured and the performance of refrigerator was predicted. In this paper, the small-scale sorption refrigerator operates with the cycle time of 4805. Its predicted cooling capacity is 25 W at -15
and COP is 0.23.
Numerical Analysis of Thermal Environments and Comfort for Local Air Conditioning System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 318~328
Numerical simulation using computational fluid dynamics (CFD) is performed to calculate the velocities and temperature profiles of air in adjacent to a worker within the individual local air conditioning system. The calculation domain is the space of ㄴ between walls and a worker in the climate room. The fresh air is supplied from the three different inlets located on the right, left and center wall in the climate room. In this study, the calculated data of velocities and temperature profiles of air in the nearest the skin of a worker are used to calculate the PMV (Predicted Mean Vote) for evaluation of thermal comfort of a worker in the local air conditioning system. Because the data of veto-cities temperature profiles of air in adjacent to a worker and the PMV of a worker are the design parameters of the local air conditioning system. The results of calculation show that the fresh air velocity and injection position are closely related to the PMV value. In individual air condition system of ㄴ, the appropriate PMV are obtained when the fresh air velocity and position are 1.0 m/s, throat of a worker and are 1.5 m/s, head of a worker, respectively. The method of numerical calculation is effective to obtain the optimum velocity and position of the fresh air for optimum the PMV and energy saving in individual local air conditioning system.
A Study on the Period of Optimum Defrost of Auto Defrost Unit by the Forced Fan Evaporator
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 4, 2003, Pages 329~335
This study is on a experiment which shows to defrost automatically on the optimum time regardless of defrosting method. The result shows that the more defrost layers increase in fin tubes of evaporation, the less the section of the circulating air reduce. Thickness of the frost formation increases, so a pressure difference of ventilation increase, as a result automatic defrosting system sets the time COP drops suddenly up optimum time. Automatical defrosting system can find out the initial related current of evaporator fan motor and the value of load current in the optimum time. And it sets defrosting time, evaporating temperature, and temperature in refrigerator up system requiring value. Consequence of this experiment is that energy consumption with defrost load gets effect of reduction of eleven percent per 25.4 hours compared with common defrosting.