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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 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
Cooling Enhancement Potential of an Air-Cooled Condenser by Evaporative Cooling
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 203~210
This paper describes the potential advantages in applying evaporative cooling to air-cooled condensers. The cooling characteristics of an air-cooled condenser with its surface fully covered with thin water film are investigated and compared with that of an air-cooled condenser with usual dry surface. By applying the evaporative cooling, the cooling performance of the condenser is shown to improve enormously. When the outdoor air is 35
and 40% in relative humidity, the condensing temperature of the refrigerant is decreased by 2
. Even when the incoming air is fully saturated with water vapor, the evaporation from the wet surface occurs to cause a decrease in the condensing temperature by 1
. The main reason for this improvement is assessed as the addition of an efficient cooling mechanism which is the water evaporation resulting in latent heat absorption.
Effect of a Solid Insert on Thermal Stratification in a Side-Heated Natural Convection Enclosure
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 211~217
Effect of a solid insert on thermal stratification in the natural convection enclosure is numerically investigated. The enclosure consists of two differently heated vertical walls and two adiabatic horizontal walls. A solid insert is located in the middle of the enclosure. The non-dimensional governing equations are solved by using the SIMPLER algorithm. The computations are carried out with the variations of thermal conductivity, width and height of the solid insert. The Prandtl number of the fluid in an enclosure is fixed at Pr=0.71, Two cases of Rayleigh number are considered in the present study, i.e., Ra:10
. The thermal stratification attenuates as thermal conductivity, width, and height of the solid insert are increased. As the thermal conductivity ratio of a solid insert to fluid increases beyond (equation omitted)10
, the thermal stratification ratio shows an asymptotic value.
Heat Transfer and Pressure Drop Characteristics of Heat Exchangers Having Plain Fins Under Dry and Wet Conditions
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 218~229
In this study, dry and wet surface pressure drop and heat transfer characteristics of heat exchangers having plain fins were investigated. Nine samples having different fin pitches and rows were tested. The wet surface heat transfer coefficient was reduced from experimental data using enthalpy-potential method. The wet surface heat transfer coefficients were approximately equal to the dry surface values except for one row configuration. For one row configuration, the wet surface heat transfer coefficients were approximately 30% lower than the dry surface values. For the pressure drop, the wet surface yielded approximately 30% higher values compared with the dry surface counterpart. Data were compared with existing correlations.
Effects on Refrigerant Maldistribution on the Performance of Evaporator
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 230~240
An experimental investigation was conducted to study two-phase flow distribution in a T-type distributor of slit fin-and-tube heat exchanger using R22. A comparison was made between the predictions by previously proposed tube-by-tube method and experimental data for the heat transfer rate of evaporator. Experiments were carried out under the conditions of saturation temperature of 5
and mass flow rate varying from 0.6 to 1.2kg/min. The inlet air has dry bulb temperature of 27
, relative humidity of 50% and air velocity varying from 0.63 to 1.71㎧. Experiment show that air velocity increased by 85.2% is need for T-type distributor with four outlet branches than that of two outlet branches under the superheat of 5
, which resulted in air-side pressure drop increase of 130% for T-type distributor with four outlet branches as compared to two outlet branches.
Optimum Design of
Scroll Compressor for Heat Pump Water Heater
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 241~249
A parametric study on the scroll wrap configuration factors of a
scroll compressor for heat pump water heater has been carried out. Since there are 7 scroll wrap design parameters and 5 equations relating them, two of the design parameters can be selected as independent parameters. In this study, the wrap thickness and orbiting radius are chosen as independent ones. Computer simulation program has been used to estimate the compressor performance at various combinations of the scroll wrap design parameters. It has been found that there exists optimum combination of the wrap parameters for the highest compressor performance over analyzed ranges of the design parameters.
Experimental Study on the Irradiation and Surface Sterilization Effect of Ultra Violet Ray in Air Conditioning System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 250~257
Recently, the use of UVC lamps inside building air-conditioning system has been increasing in both medical and nonmedical buildings for the control of environmental microorganisms. In the present study, irradiance performance test of UVC lamp was carried out and surface sterilization effect of UV ray was investigated by using UV ray irradiation experimental chamber and pilot system. Experimental results show that the effective irradiance of UVC lamp is strongly dependent on air velocity and temperature with exception of relative huminity in air-conditioning system. An individual microbiological kill effectiveness experiment also shows that the fractional kill of two microbiological samples such as E. Coli and Legionella is roughly the same as the estimated fractional kill in the case of chamber test and pilot system test.
The Effects of Additives on the Thermal Properties of a Clathrate Compound(I) -The Case of Ethanol-
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 258~264
The ice thermal storage system is to use consolation latent heat of water. But, supercooling phenomenon of water during phase change is to increase the cooling capacity and to decrease COP of the refrigerator. Furthermore, this causes the operation cost of system to increase and the efficiency of energy to decrease. Therefore, the better thermal storage material than the water is required. The purpose of this study is to improve supercooling characteristics and thermal properties of TMA 30wt% clathrate by using Ethanol.
Analysis of Air Flow Rate Distribution for the Bathroom Exhaust System in High-rise Buildings Using T-method
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 265~272
Based on the T-method, a new scheme for predicting air flow rate distribution in a bathroom exhaust system is developed. Introduction of individual duct route enables us to disintegrate a complicated multi-fan ductwork into a set of simultaneous single-fan subsystems. The scheme is validated via the analysis of a well-posed test problem, showing physical consistency. In order to demonstrate the utility and capability of our method, the bathroom ventilation system in a 20-story residential building is selected as an example. Under the typical design condition, the air flow rate of each exhaust fan at the balancing point is successfully predicted, and such information can lead to an engineering estimation for the overall system performance. While some deficiencies in ventilation are found at bathrooms at lower floors with 6mmAq-rated exhaust fans, they disappear over the whole building by using fans of enhanced static pressures, 7 and 8mmAq. Finally the present scheme seems to be useful for practical design of multi-branched, multi-fan ventilation systems.
Performance Test of a Multi-riser Fluidized Bed Heat Exchanger for Flue Gas Heat Recovery
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 273~279
A lab-scale fluidized bed heat exchanger for waste gas heat recovery is devised and tested. Compared to our previous works on fluidized bed type system with a single riser, the present heat exchanger system is featured by its multiple (four) risers to handle increased amount of exhaust gas. Particles are introduced to the main hot gas stream alongside the pipe circumference near riser inlets. The heat exchanger performance and pressure drop are evaluated through experiments for the present gas-to-water heat exchanger system.
Heat Transfer Performance of Individual Rows in Fin-Tube Heat Exchangers
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 280~286
An experimental study is peformed to examine the heat transfer performance of individual rows of fin-tube heat exchangers. The heat transfer performance is measured using an air-enthalpy type calorimeter. The examined heat exchangers consist of 7mm tube and fin patterns of them are slit and louver types. Equivalent fin spacings are 18 fins per inch(fpi) for all samples, and the number of tube rows are two. In order to confirm that thermal boundary condition on fins of each row are the same, physically separated between two rows as well as connected heat exchangers are used. The frontal air velocity is varied from 0.7 to 2.5㎧. Heat transfer performance for each row is measured. It is observed that the heat transfer coefficient of the second row is smaller than that of the first row at low Reynolds number while larger at high Reynolds number.
Experimental Performance Study of the Bubble Pump for the Diffusion Absorption Refrigerating System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 287~292
An experimental investigation was carried out to study the performance of a bubble pump for the diffusion absorption refrigerating system. Ammonia was used as the refrigerant and the helium was charged in order to balance the pressure between the low and high pressure side. As experimental variables, the concentration of ammonia charged into system, heat input, and the pressure of helium were selected. Experimental results show that the generation rate of ammonia vapor and the circulation rate of diluted ammonia solution were increased as the heat input increases, but the ratio of the solution to vapor flow rate was decreased. The generation rate of refrigerant vapor and the circulation rate of diluted ammonia solution increased as the system pressure decreased. Finally under the condition of 25 bars, the concentration of rich ammonia solution was not affected by the generation rate of ammonia vapor and the circulation of diluted ammonia solution.
Numerical Shape Optimization for Plate-Fin Type Heat Sink
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 293~302
In this study the optimization of plate-fin type heat sink for the thermal stability is peformed numerically. The optimum design variables are obtained when the temperature rise and the pressure drop are minimized simultaneously. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by using the sequential quadratic programming (SQP) method which is widely used in the constrained non-linear optimization problem. The results show that when the temperature rise is less than 34.6K, the optimal design variables are as follows; B
=1.365mm, and t=10.962mm. The Pareto optimal solutions are also presented for the pressure drop and the temperature rise.
Evaluation on Thermal Environment Installed Ventilating Fans in the Rotunda at New National Museum of Korea
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 3, 2004, Pages 303~309
In order to improve thermal comfort in the Rotunda, which is high and wide visiting space of the new national museum of Korea, eight ventilating fans were installed near the ceiling of Rotunda. It has been analyzed thermal comfort of Rotunda with/without ventilating fans by numerical simulation. To evaluate thermal comfort of the Rotunda, well-known indices, PMV and PPD were introduced. The results of present investigation show that temperature distribution of the case with fans is closer to target temperature than the case with-out fans at the breathing zone. In the case without fans, thermal stratification with 16
of temperature difference occurs along the height of the Rotunda which makes the thermal environment worse and the PPD values reach up to 50% in the 6th floor connection passage. In the case with fans, however, the vertical temperature difference were reduced to 9
and the PPD values were lower below 20%. Consequently, the ventilating fans adopted on this study are effectively used for improving the thermal comfort in large space structure with thermal stratification.