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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 17, Issue 12 - Dec 2005
Volume 17, Issue 11 - Nov 2005
Volume 17, Issue 10 - Oct 2005
Volume 17, Issue 9 - Sep 2005
Volume 17, Issue 8 - Aug 2005
Volume 17, Issue 7 - Jul 2005
Volume 17, Issue 6 - Jun 2005
Volume 17, Issue 5 - May 2005
Volume 17, Issue 4 - Apr 2005
Volume 17, Issue 3 - Mar 2005
Volume 17, Issue 2 - Feb 2005
Volume 17, Issue 1 - Jan 2005
Selecting the target year
Analysis of Frosting Performance of a Fin-Tube Heat Exchanger
Yang Dong-Keun ; Lee Kwan-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 965~973
This paper proposes a mathematical model for predicting the frosting performance on a fin-tube heat exchanger. The model consists of empirical correlations of average heat transfer coefficients for the plate and tube surfaces and a diffusion equation inside the frost layer. The numerical results are compared with experimental data for the frost thickness, the frosting rate and the heat transfer rate to validate the proposed model. The results are in good agreement with the experimental data, and show that this model can be applied to predict frosting performance of common fin-tube heat exchanger.
Optimization of Frosting Performance of a Fin-Tube Heat Exchanger
Yang Dong-Keun ; Lee Kwan-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 974~980
The optimization of design factors on the frosting performance of a fin-tube heat exchanger is carried out using Taguchi method. The fin spacings of the heat exchanger are selected as design factors. Optimum values of the design factors under operating conditions of a household refrigerator/freezer are proposed. The average heat transfer rate and operating time of the optimum models, compared to those of a reference model, are increased at most by
External Condensation Heat Transfer Coefficients of R22 Alternative Refrigerants and R134a According to the Saturated Vapor Temperature Change on an Enhanced Tube
Yoo Gil-Sang ; Hwang Ji-Hwan ; Park Ki-Jung ; Jung Dongsoo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 981~989
In this study, external condensation heat transfer coefficients (HTCs) are measured on a low fin tube and Turbo-C tubes at the saturated vapor temperature of
for R22, R410A, R407C and R134a with the wall subcooled at
. The HTCs of all refrigerants decreased as increasing the saturation temperature from
. This trend is due to better thermodynamic properties of the liquid phase at low temperature Beatty and Katz's prediction yielded a
deviation for the low fin tube data. The heat transfer enhancement factors for the 26 fpi low fin tube and Turbo-C tubes are 4.0
5.5 and 3.0
8.1 respectively for the refrigerants tested. Finally the performance of Turbo-C tube is better than that of the low fin tube.
Effect on Stratification due to Diffuser Shape in a Thermal Storage Tank
Lee Young-Soo ; Lee Sang-Nam ; Kim Jong-Ryul ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 990~997
The stratified effect was investigated with three different types of diffuser shape in a thermal storage tank with variation of diffuser diameter, velocity, Froude number etc. Its effect was estimated by the degree of stratification. No matter of diffuser diameter and shape, the degree of stratification was the best as the Froude number gets closer to 1. In the case of a curved diffuser, when its diameter is a quarter of tank diameter and ejection velocity in a diffuser is approximately 0.2 m/s, the Froude number was almost 1. In the case of a flatted diffuser, when ejection velocity was 0.05 m/s, the Froude number was 1.5. Both cases which Froude number were nearer 1, showed the good degree of stratification.
Sensitivity Analysis on KS and JIS Standard for Heat Recovery Ventilator
Yee Jurng-Jae ; Ihm Pyeong-Chan ; Kim Hwan-Yong ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 998~1004
Recently natural ventilation rate is decreased due to the airtightness of apartment building. Therefore the use of heat recovery ventilator (HRV) has been greatly increased as an alternative method to supply fresh air and save energy in the building. In this research the experiment standard of HRV is compared between KS and JIS and the sensitivity analyses are experimented by both standards. Under cooling experiment condition indoor and outdoor wet-bulb temperature difference of JIS is 2 to 3 times higher than that of KS. It shows that the efficiency measurement of HRV by KS is expected to have greater sensitivity than by JIS and thus accurate measurement of web-bulb temperature is required. The experimental results provide that the efficiency of thermal exchange is resemblance to each others between KS and JIS. Under cooling experiment condition the efficiency of humidity exchange by KS presents higher than by JIS, however, under heating experiment condition the efficiency by KS shows lower than by JIS, reversely.
Simulation on the Heating Performance of a 2-Stage Compression Heat Pump System Using River Water
Park Chasik ; Kim Bohyun ; Kim Yongchan ; Lee Young Soo ; Bang Ki-young ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1005~1013
The use of river water as a heat source of a heat pump has the advantage in the performance compared to the use of atmospheric air because the temperature variation of river water over the year is relatively small. In this study, the performance of the heat pump system using river water as a heat source was numerically investigated. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion devices. The peformance of the heat pump system using river water was improved by
compared to that using atmospheric air in winter conditions.
Analysis of Geometrical Effects on Heat Transfer Characteristics in a Modular Flat Tube-Bundle Heat Exchanger
Park, Byung-Kyu ; Lee, Joon-Sik ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1014~1021
Flow channels with non-circular cross-sections are encountered in a wide variety of heat exchangers. Accurate friction factor and Colburn j factor data are essential for the design and viable applications of such heat exchangers. In this study, an analysis is con ducted on heat transfer and pressure drop characteristics for tube-bundle heat exchanger with various arrangements of tubes, of which their geometry could easily be modified from a circular one in a harsh environment. The parameters investigated are aspect ratio, pitch, and inclined angle of tubes. The results obtained are: (1) Aspect ratio has larger influence on the j and f factor than pitch; (2) As aspect ratio increases, both j and f factors decrease; (3) The high performance is achieved when the pitch and aspect ratio are in the range of 1.5
2.5 and 1.25
2.0, respectively; and (4) the inclined arrangements of tubes show unfavorable results for both heat transfer and pressure drop characteristics in spite of the positive possibility of condensate removals in a latent heat recovery system.
Characteristic of the Ion Wind Using Corona Discharge and Enhancement of Heat Transfer
Lee Jae-Il ; Hwang Yu-Jin ; Joo Ho-Young ; Ahn Young-Chull ; Shin Hee-Soo ; Lee Jae-Keun ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1022~1027
An experimental study is conducted to investigate the characteristics of the ion wind generated by the electric field between a needle electrode and the parallel plate electrodes. The ion wind enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement makes no noise or vibration. This study is conducted to develop the electronic cooling device. The measured gas velocities and heat transfer coefficients are proportional to the applied voltage. The heat transfer coefficient can be increased as compared with a natural convection. The maximum enhancement of heat transfer obtained in this system is
for 3 W in heat transfer rate.
Simulation and Experimental Study on an Air-Cooled
Oh Min Kyu ; Kim Hyun Jun ; Kim Sung Soo ; Kang Yong Tae ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1028~1034
The objective of this paper is to study the effects of the cooling air mass flow rate and the heat input variation by the simulation and the experiment. An air-cooled
absorption chiller is tested in the present study. The nominal cooling capacity of the single effect machine is 17.6 kW (5.0 USRT). The overall conductance (UA) of each component, the cooling capacity, coefficient of performance and each state point are measured with the variation of the cooling air mass flow rate and the heat input. It is found that the COP and cooling capacity increase and then decreases with increasing the heat input. It is also found that the COP and the cooling capacity increase and keep constant with increasing the cooling air mass flow rate. The maximum COP is estimated as 0.51 and the optimum cooling air mass flow rate is
from the present experiment.
Flow Characteristics of a Laminar Rivulet Down an Inclined Surface
Kim, Byong-Joo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1035~1042
In the present study, the principle of minimum energy is employed to configure the shape of rivulet flowing down an inclined surface. The profile of laminar rivulet is determined by numerical integration. The maximum center thickness, which corresponds to the minimum thickness of falling film, is found to exist regardless of liquid flow rate and is compared with the analytical and experimental data. At small liquid flow rate the center thickness of rivulet and its width increase almost linearly with flow rate. Once the center thickness of rivulet becomes very close to its maximum value, its growth rate retards abruptly. However the width of rivulet increases proportionally to the liquid flow rate and most part of its free surface is as flat as that of stable film. The growth rate of rivulet thickness with respect to liquid flow rate becomes larger at bigger contact angle. The width of rivulet increases rapidly with its flow rate especially at small contact angle, As the liquid-vapor interfacial shear stress increases, the center thickness of rivulet decreases with its flow rate, which is remarkable at small contact angle. However the effect of interfacial shear stress on the width of rivulet is almost negligible.
A Study on the Calculation of Ventilation Rate for the Improvement of Indoor Air Quality on the Barracks
Choi Jeong-Min ; Yu Jin-Sang ; Jeong Young-Il ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1043~1049
The purpose of this study is to improve indoor air quality of the barracks which have been changed from floor-type living barracks to bed-type living barracks since 2003. Therefore, the ventilation rates of newly constructed two type barracks were simulated with the various building materials including VOCs and HCHO components. And indoor air quality of two type living barracks was measured by the field experiments. With these steps, the measures for upgrading indoor air quality depending on building material types and ventilation rate are suggested.
A Study on the Pollutant Dispersion over a Mountain Valley Region (I) : Wind Tunnel Experiments
Yoo Seong-Yeon ; Shim Woo-Sup ; Kim Seogcheol ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1050~1059
gas dispersions over a complex terrain were investigated using wind tunnel. The wind speed, temperature and concentration profiles were measured for the 1/1000 scale complicated terrain model in an Eiffel type boundary layer wind tunnel with test section of 2.5m in height and 4.5m in width. The scale model was mounted on the top of a plate which can rotate with respect to the approaching wind. Dispersion processes from a continuous emission source driven by various wind direction were investigated, including plume climbing over the steep up-slope of the mountain and down-spreading toward the lower level of the valley. Extensive dispersion experiment data (wind speeds and concentration profiles) were provided for verification and validation of dispersion models. Under the identical flow and emission conditions, the independently measured profiles of the temperature and
concentration showed an excellent agreement which ensured the credibility of the results.
A Study on the Pollutant Dispersion over a Mountain Valley Region (II) : Numerical Simulation
Shim Woo-Sup ; Kim Seogcheol ; Yoo Seong-Yeon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1060~1071
Passive gas dispersions over a 1/1000 scale terrain model at Eiffel type wind tunnel were reproduced by numerical simulation. Large eddy simulation was used to treat the sub-grid scale turbulences. The terrain features were represented by millions of point forces densely distributed over the solid surface using the virtual boundary method. The model simulations agreed very well with the experiments in a consistent fashion for all wind directions. The measured profiles of the wind speeds as well as the tracer gas concentrations were nicely simulated by the CFD model at most locations scattered over the model terrain. With scale factor adjusted and the thermal stratification effects incorporated, the CFD model was expected to provide reliable information on pollutant dispersions over the real complex terrains.
A Study on PID Tuning Technique of a Thermal Environment Chamber
Shin Younggy ; Yang Hooncheul ; Tae Choon-Seob ; Jang Cheol-Yong ; Cho Soo ; Kim Youngil ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1072~1078
The present study has been conducted to tune a PID controller for large thermal systems such as a thermal environment chamber. In spite of large thermal mass of the thermal chamber under test, its response delay time was found to be negligible mainly due to high air recirculation rate. In general, heating and cooling capacities tend to be small compared the size of a thermal environment chamber, which leads to long transient periods of one hour or so. In the study, a PI tuning method is suggested which makes system responses faster while reducing overshoots and hunting by utilizing efficiently proportional band of actuators.
Evaluation of Thermal Comfort and Ventilation Performance in the Lecture Room with Ventilation System and Two Different Air-conditioning Systems: System Air-conditioner or Fan Coil Unit
Han Chang-Woo ; Noh Kwang-Chul ; Oh Myung-Do ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1079~1087
In this paper, thermal comfort and ventilation performance characteristics in the lecture room with the ventilation system and two different air-conditioning systems, system air-conditioner or fan coil unit, were evaluated by experimental and numerical methods. We compared the measured data with the computational results of the predicted mean vote and carbon dioxide concentration. Additionally the ventilation effectiveness was calculated numerically. From a viewpoint of the uniformity of PMVs in the lecture room, the thermal distribution performance of the system air-conditioner was more effective than the fan coil unit. Carbon dioxide concentration and ventilation effectiveness were barely affected by the type of the air-conditioning system.
Measurement of the Ice Packing Factor of an Aqueous Solution Using the Index of Refraction
Peck Jong-Hyeon ; Chung Dong-Yeol ; Kang Chaedong ; Hong Hiki ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 17, issue 11, 2005, Pages 1088~1094
In the present paper, a new method is proposed for the measurement of the ice packing factor (IPF) of an ice slurry using the index of refraction. The purpose of the new method is to improve the resolution of the measurement and to increase its resistance to electric noise as compared to the standard IPF measurement technique that relies on measurement of the freezing temperature. These two methods are similar in that they both obtain a concentration of aqueous solution from measured physical quantities and calculate the IPF using a relation between concentration and IPF. We experimented and compared the two methods, whose results were also compared with results from the calorimeter method obtaining the IPF directly They are in good agreement (within
), which demonstrates the validity of the newly proposed method.