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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 18, Issue 12 - Dec 2006
Volume 18, Issue 11 - Nov 2006
Volume 18, Issue 10 - Oct 2006
Volume 18, Issue 9 - Sep 2006
Volume 18, Issue 8 - Aug 2006
Volume 18, Issue 7 - Jul 2006
Volume 18, Issue 6 - Jun 2006
Volume 18, Issue 5 - May 2006
Volume 18, Issue 4 - Apr 2006
Volume 18, Issue 3 - Mar 2006
Volume 18, Issue 2 - Feb 2006
Volume 18, Issue 1 - Jan 2006
Selecting the target year
Simulation and Verification Experiment of Cooling and Heating Load for a Test Space with Forced Ventilation
Kim, Dong-Hyuk ; Hong, Hi-Ki ; Yoo, Ho-Seon ; Kim, Ook-Joong ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 947~954
Building energy consumption according to the ventilation has been considered to be an important subject. The purpose of this study is to investigate the cooling and heating loads in a test space with a forced ventilating system. In the test space, on/off controlled air-conditioning and forced ventilating facility were operated between 8 : 30 to 21 : 00 during 4 days and some important data like temperatures and energy consumption were measured to obtain actual thermal loads. The simulation was carried out in a mode of temperature level control using a TRNSYS 15.3 with a precisely measured air change amount and performance data of air-conditioner. Heating load and cooling load including sensible and latent were compared between by experiment and by simulation. Both of thermal loads associated with ventilation show a close agreement within an engineering tolerance.
Pool Boiling Heat Transfer Coefficients of Mixtures Containing Propane, Isobutane and HFC134a on a Plain Tube
Park, Ki-Jung ; Baek, In-Cheol ; Jung, Dong-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 955~963
Nucleate pool boiling heat transfer coefficients (HTCs) were measured with one nonazeotropic mixture of Propane/Isobutane and two azeotropic mixtures of HFC134a/Isobutane and Propane/HFC134a. All data were taken at the liquid pool temperature of
on a horizontal plain tube with heat fluxes of
with an interval of
in the decreasing order of heat flux. The measurements were made through electrical heating by a cartridge heater. The nonazeotropic mixture of Propane/Isobutane showed a reduction of HTCs as much as 41% from the ideal values. The azeotropic mixtures of HFC134a/Isobutane and Propane/HFC134a showed a reduction of HTCs as much as 44% from the ideal values at compositions other than azeotropic compositions. At azeotropic compositions, however, the HTCs were even higher than the ideal values due to the increase in the vapor pressure. For all mixtures, the reduction in heat transfer was greater with a larger gliding temperature difference. Stephan and
and Jung et al's correlations predicted the HTCs of mixtures with a mean deviation of 11%. The largest mean deviation occurred at the azeotropic compositions of HFC134a/Isobutane and Propane/HFC134a.
A Study on Pump Down Operation Performance of Refrigerator
Kim, Chul-Soo ; Chung, Han-Shik ; Jeong, Hyo-Min ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 964~970
Vapor compression refrigerators have much critical variables such as the controls of temperature and pressure switches, control durations and operating hours of electronic valves. This study compares and analyzes the data which is obtained from system controlling of the evaporation temperatures which are generally used in automatic pump down operating systems. Through this study, the automatic evaporation control operation system will be more ideal for the system to keep the proper temperature distribution depending on the purpose of evaporation side. The automatic pump down control operation is more appropriate for the system to aim at the effective use of evaporation side without using the temperature difference. And this test will be proved that the changes at the low pressure side didn't have significant impacts on the high pressure side.
Experimental Study on Heat Transfer Characteristics of HFC134a for Enhanced Tubes Used in a Flooded Evaporator
Yang, Seung-Woo ; Lee, Young-Su ; Jeong, Jin-Hee ; Kang, Yong-Tae ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 971~976
The objectives of this paper are to study the characteristics of pool boiling heat transfer for enhanced tubes used in the evaporator of turbo chiller and to provide a guideline for optimum design of an evaporator using HFC134a. Three different enhanced tubes are tested at 4 different saturation temperatures. The wall super heated temperature difference ranges from
. The refrigerant, HFC134a evaporates on the outside of the tube while the chilled water flows inside the tube. This study provides experimental heat transfer coefficients for evaporation on the enhanced tubes. It is found that the turbo-II tube provides the highest heat transfer coefficient.
Characteristics of Condensing Heat Transfer and Pressure Drop of Hydrocarbon Refrigerants
Lee Ho-Saeng ; Seong Gwang-Hoon ; Tong Phan Thanh ; Yoon Jung-In ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 977~983
Experimental results for heat transfer characteristic and pressure gradient of hydrocarbon refrigerants (R-290, R-600a, R-1270) and HCFC refrigerant (R-22) during condensation inside horizontal double pipe heat exchangers are presented. The test sections which have one tube diameter of 12.70 mm with 0.89 mm, 9.52 mm with 0.76 mm, 6.35 mm with 0.13 mm wall thickness are used for this investigation, respectively. The local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 10.92 mm, 8 mm and 6.1 mm inner diameters. These results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.
Performance Characteristics of Accumulator Heat Exchangers with Operating Conditions of a Refrigeration System
Kang, Hoon ; Park, Cha-Sik ; Jeon, Jong-Ug ; Kim, Yong-Chan ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 984~991
The applications of multi air-conditioners into multiplex and high-rise buildings have been increased by replacing central air-conditioning systems. The pipe length and altitude difference between the indoor and outdoor units can be increased based on installation conditions, which may increase the possibility of flash gas generation at the expansion device inlet. The flash gas generation causes rapid reduction of refrigerant flow rate passing through the expansion device, yielding lower system efficiency. Accumulator heat exchangers have been widely used in multi air-conditioners in order to minimize flash gas generation and obtain system reliability. However, the studies on the heat transfer characteristics and pressure drops of accumulator heat exchangers are very limited in open literature. In this study, the heat transfer rates and pressure drops of accumulator heat exchangers were measured with refrigerant flow rate and operating conditions by using R-22. The heat transfer rate increased with the increase of refrigerant flow rate, while subcooling decreased. The heat transfer rate enhanced with the reduction of inlet superheat and subcooling due to the increased temperature difference between the accumulator and inner heat exchanger.
Optimum Design of Waste Heat Boiler with Water Tube and Three Drum
Lee, Kwan-Jong ; Han, Jin-Ho ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 992~998
This study is to optimize design parameters for waste heat recovery boiler with water tube and three drum. The design optimization considered here is to find the most economic dimension of the boiler considered which results in a minimum cost in producing a unit amount of steam per given period of operation. For this purpose, optimize design have to determine what are the main parameters of affecting the total cost of producing a unit amount of steam which is comprised of manufacturing cost of the boiler, operating cost of the fan etc.
An Experimental Study of Temperature Profiles in Mixing Zone of AHU with an Air Mixer
Pak, Kwon-Jong ; Lee, Sek-Jun ; Jang, Young-Keun ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 999~1006
A study of temperature profiles in mixing zone of AHU (air handling unit) can contribute greatly to enhance performance of AHU system, so the study on the temperature distribution between RA (return air) and OA (outdoor air) is important to analyze the mixing characteristics in a mixing zone of AHU. Accordingly, the temperature profiles during RA (return air) and OA (outdoor air) supply process into mixing zone of AHU with an air mixer are studied experimentally. The effect of air mixer, OA temperature and RA/OA flow rate are studied in detail. In this study, the results show that the mixing efficiency is all high for installed the air mixer. The more OA temperature increase and OA flow rate decrease, the more mixing efficiency is high.
Study on Single-Phase Thermal and Hydrodynamic Characteristics in the Entry Region of a Mini-Channel Heat Sink
Jang, Yong-Hee ; Kim, Yong-Chan ; Lee, Kyu-Jeong ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 1007~1016
Although the advance in electronic technology enables a large number of circuity to be packed in a small volume, it is simultaneously required to remove the high heat load produced by them. In this study, the heat transfer and pressure drop characteristics of a mini-channel heat exchanger, which is designed for liquid cooling of electronic components, are investigated by varying operating conditions. Water and FC-72 were used as working fluids. The mini-channel heat exchanger was made with circular shape channels having din-meters of 2, 3, and 4 mm in regular intervals, and the channel length was 100 mm. The header and inlet guide pathway to provide uniform inflow were attached at the inlet of the test section. Copper block including the heaters was attached at the sidewall of the test section as a heat source, which provided the heat flux from 5 to
. The entrance effects enhanced the heat transfer coefficient in the mini-channel significantly. In addition, the single-phase pressure drop in the mini-channel was very similar to that predicted by the laminar flow correlation except that the transition Re decreased due to flow instability in the entrance region.
Pool Boiling Heat Transfer Coefficients of Hydrocarbon Refrigerants on Various Enhanced Tubes
Park, Ki-Jung ; Jung, Dong-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 1017~1024
In this work, pool boiling heat transfer coefficients (HTCs) of five hydrocarbon refrigerants of propylene, propane, isobutane, butane and dimethylether (DME) were measured at the liquid temperature of
on a 26 fpi low fin tube, Turbo-B, and Thermoexcel-E tubes. All data were taken from 80 to
in the decreasing order of heat flux. The data of hydrocarbon refrigerants showed a typical trend that nucleate boiling HTCs obtained on enhanced tubes also increase with the vapor pressure. Fluids with lower reduced pressure such as DME, isobutane, and butane took more advantage of the heat transfer enhancement mechanism of enhanced tubes than those enhancement ratios of
among the tubes tested due to its sub-channels and re-entrant cavities.
Drag Reduction Phenomena of Surfactant Turbulent Pipe Flows
Yoon, Hyung-Kee ; Shin, Kwang-Ho ; Chang, Ki-Chang ; Ra, Ho-Sang ; Yoo, Seong-Yeon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 1025~1032
This is to characterize the fluid mechanics of surfactant water solutions, which exhibit drag reduction in the turbulent flow as compared to pure water. The emphasis is placed on those fluid characteristic aspects of drag reducing solutions which are relevant for application in closed circulation loops for the purpose of pumping power savings, like hydronic cooling and heating systems in buildings. The experiments are carried out with the solutions of the surfactant Beraid DR-IW 616 in concentration of
. The following key parameters are focused in this study: surfactant concentration, solution temperature and pipe diameter.
Characteristics of Particle Deposition onto the Cleanroom Wall Panel with Electrostatic Voltages
Noh, Kwang-Chul ; Son, Young-Tae ; Kim, Jong-Jun ; Oh, Myung-Do ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 1033~1038
We carried out the experiments on particle deposition onto the cleanroom wall panels. And then we investigated the particle deposition characteristic coefficients for electrostatic voltages and particle size. It was found that there is little difference in characteristics of the particle deposition between the steel panel and the anti-static coating panel. In case of that the particle size is under
, the particle deposition characteristic coefficient becomes larger as the electrostatic voltage induced to the cleanroom wall panel is increasing. Where in case of that the particle size is over
, the particle deposition characteristic coefficients do not show any differences with the electrostatic voltages. It is due to that the electrostatic force is the major particle transport mechanism for submicron particles, while the gravitational settling is the major particle transport mechanism for overmicron particles when the electro-static voltages are induced to the cleanroom wall panel.
A Numerical Study on the Compression Wave Generated by the Train Entering a Tunnel - Effects of the Start Method of a Train -
Kim, Sa-Ryang ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 12, 2006, Pages 1039~1046
The numerical simulations on the train entering a tunnel are performed by solving unsteady axi-symmetric problems. To reduce the effects of the pressure wave generated by the train starting abruptly, several starting methods of the train are examined. The high order velocity increase gives better results than those for the linear velocity increase. The high order velocity increase gives good results for the pressure rise by the train entering a tunnel, too. The distance to the train reaches the highest running velocity from the start should be more than 60 m when the train speed is 350 km/h.