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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
Influence of Charging Amounts on the Cooling Performance of
Mixtures and Concentration Shift Behavior
Kim, Ju-Hyok ; Hwang, Yun-Wook ; Kim, Min-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 851~858
] and propane mixtures, which are environmentally benign, nontoxic, low in price, and compatible with materials and lubricants, were considered as promising alternative refrigerants. A fully instrumented air-conditioning system was developed for a precise performance evaluation of pure
mixtures. In this paper, the effect of the charging amount and circulation concentration on the cooling performance of the system using
and propane mixtures was tested and discussed. Pure
and 85/15, 75/25 and 60/40 binary blends by the charged mass percentage of
were selected as working fluids. An optimum charging amount was proposed as a parameter instead of the degree of subcooling, which can not be well defined in the transcritical cycle, to properly compare the performance between the transcritical and subcritical cycles.
Vapor-Liquid Equilibria of Carbon Dioxide and Propane Mixtures
Kim, Ju-Hyok ; Kim, Min-Soo ; Kim, Man-Hoe ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 859~866
This paper presents the vapor-liquid equilibrium (VLE) data measured for carbon dioxide and propane mixtures. Their mixtures were considered as promising alternative refrigerants due to good thermophysical properties and negligible environmental impact. The isothermal VLE data were measured at eight temperatures ranging from 253.15 to 323.15 K in the circulation type equipment with a view cell. The binary system was found to be a zeotropic mixture in the tested temperature range and could be correlated with sufficient accuracy by using the Peng-Robinson equation of state (PR EoS) with the van der Waals one fluid mixing rule. A comparison with published experimental VLE data has been carried out by means of the PR equation of state. In addition, the phase behaviors of carbon dioxide and propane mixtures were analyzed based on the measured VLE data.
An Experimental Study on the Effects of Contact Angle on a Falling Liquid Film
Kim, Kyung-Hee ; Kang, Byung-Ha ; Lee, Dae-Young ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 867~873
Vertical falling liquid film is extensively used in heat and mass transfer processes of many applications, such as evaporative coolers, cooling towers, and absorption chillers. In such cases, it is required that the falling film spreads widely in the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film or hydrophilic surface treatment affects the fluid physical properties of the film. Surfactant addition not only decreases contact angle between the liquid and solid surface but also changes the surface from hydrophobicity to hydrophilicity. In this study, the effects of contact angle on falling film characteristics over a vertical surface have been investigated experimentally. The contact angle is varied either by an addition of surfactant to the liquid or by hydrophilic surface treatment. It is found that the wetted area is increased and film thickness is decreased by the hydrophilic treatment as compared with those of other surfaces. With this hydrophilic treatment, the falling liquid film spreads out widely in the surface. As surfactant concentration is increased, wetted area is also increased and the film thickness is substantially decreased.
Performance Characteristics of a Hybrid Air-Conditioner for Telecommunication Equipment Rooms
Kim, Yong-Chan ; Choi, Jong-Min ; Kang, Hoon ; Yoon, Joon-Sang ; Kim, Young-Bae ; Choi, Kwang-Min ; Lee, Ho-Seong ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 874~880
The power density and heat dissipation rate per unit area of the telecommunication equipment have been increased with the technology development in the footprint of telecommunication hardware. A proper heat dissipation method from the PCB module is very important to allow reliable operation of its electronic component. In this study, a hybrid air-conditioner for the telecommunication equipment room was designed to save energy and obtain system reliability. For high outdoor temperatures, the hybrid system operates in the vapor compression cycle, while, for low outdoor temperatures, the hybrid system works in the secondary fluid cooling cycle with no operation of the compressor. The performance of the hybrid air-conditioner was measured by varying outdoor and indoor temperatures. The hybrid air-conditioner yielded 50% energy saving compared with the conventional refrigeration system when the mode switch temperature was
Mass Flow Characteristics and Empirical Modeling of R22 Flowing through Electronic Expansion Valves
Park, Cha-Sik ; Lee, Sun-Il ; Kim, Yong-Chan ; Lee, Young-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 881~887
The objective of this study are to analyze the flow characteristics of R22 flowing through EEVs and to develop an empirical correlation to predict the refrigerant flow rate. The mass flow rates of EEVs with different geometries were measured at various condensing temperatures, subcoolings, and EEV openings. Based on the experimental data, an empirical correlation for mass flow predictions in EEVs was developed by modifying the orifice equation. The correlation showed good agreement with the measured data for R22 with average and standard deviations of 1.4% and 6.1%, respectively. Approximately 90% of the measured data were within
of the predictions.
Experimental Study of Reynolds Number Effects on Heat/Mass Transfer and Pressure Drop Characteristics in a Rotating Smooth Duct
Kim, Kyung-Min ; Park, Suk-Hwan ; Lee, Dong-Hyun ; Cho, Hyung-Hee ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 888~895
The present study has been conducted to investigate the effects of Reynolds number on heat/mass transfer and pressure drop characteristics in a rotating smooth two-pass duct. For stationary cases, the heat/mass transfer and pressure drop Is decreased on turning region of both leading and trailing surfaces as Reynolds number increases. For rotating cases, increment of Reynolds number affects differently the heat/mass transfer and pressure drop on the leading and trailing surfaces. In the first pass, for example, the heat/mass transfer on the leading surface is greatly increased, though the heat/mass transfer on the trailing surface is almost the same. The reason is that effect of the main flow is more dominant than effect of secondary flow. In particular, it gave decrement of the heat/mass transfer and the pressure drop at turning region and upstream region of second pass for both non-rotating and rotating cases.
A Study on the Optimal Control Strategy of Air-Conditioning System with Slab Thermal Storage - Results Influenced by the Choice of a Criterion Function -
Jung, Jae-Hoon ; Shin, Young-Gy ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 896~905
An optimal control of an air-conditioning system with slab thermal storage is investigated by making use of the Maximum Principle. An optimal heat input to a plenum chamber and an air-conditioned room is determined by minimizing a criterion function which is given as integral sum of two terms. The first term is the square of the deviation in the room air temperature from the set-point value, and the second is the absolute value of the heat input. The result indicates that it tries to keep a room air temperature in set-point value by heating as much as possible at the time of a setup of a room air temperature or just before that, in order to avoid a heat loss arising at the time of the non-air conditioning. The result is compared with that of the case when the square of the heat input is used as a criterion.
Boiling Heat Transfer Characteristics of R-290 in Horizontal Smooth Minichannel
Choi, Kwang-Il ; Pamitran, A.S. ; Oh, Jong-Taek ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 906~914
The present paper dealt with an experimental study of boiling heat transfer characteristics of R-290. Pressure gradient and heat transfer coefficient of the refrigerant flow inside horizontal smooth minichannel were obtained with inner tube diameter of 3.0 mm and length of 2,000 mm. The direct electric heating method was applied for supplying a heat to the refrigerant uniformly. The experiments were conducted with R-290 purity of 99.99%, at saturation temperature of 0 to
, a mass flux range of
, and a heat flux range of
. The heat transfer coefficients of R-290 increased with increasing mass flux and saturation temperature, wherein the effect of mass flux was higher than that of the saturation temperature. Heat flux has a low effect on the increasing of heat transfer coefficient. The heat transfer coefficient was compared with six existing heat transfer coefficient correlations. The Zhang et al.'s correlation (2004) gave the best prediction of heat transfer coefficient. A new correlation to predict the two-phase flow heat transfer coefficient was developed based on the Chen correlation. The new correlation predicted the experimental data well with a mean deviation of 11.78% and average deviation of -0.07%.
A Study on the Chilling Start-up Characteristics and Performance of a Gas Loaded Heat Pipe
Hong, Sung-Eun ; Kang, Hwan-Kook ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 915~922
Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around
, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with
gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around
. It was observed that the gas loaded one had succeeded in chilling start-up operation.
Prediction of Reentering Ratio of Individual Cooling Towers Scattered on a Building Roof
Lee, Tae-Gu ; Moon, Sun-Ae ; Yoo, Ho-Seon ; Lee, Jae-Heon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 923~932
In this paper, reentering ratio and cooling capacity of individual cooling towers arrayed on a building roof were studied by a numerical method. The number of 16 cooling towers were divided into 4 banks. It was considered the summer prevailing wind characteristics as west wind and south wind of 5 m/s. It was also considered the roofwall types as the curtainwall and the louverwall that had the outdoor air intake louver in the curtainwall. In this case, the louver was suggested as the solution that could prevent reentering phenomenon due to recirculation and interference of the discharge air. In the case of the curtainwall, the averaged reentering ratio are predicted 13.3% and 24.4% for the west and south wind of 5 m/s, respectively. In the case of the louverwall, the averaged reentering ratio are predicted 2.5% and 9.7% for the west and south wind of 5 m/s, respectively. Therefore, the louverwall is a appropriate solution for reducing the reentering phenomenon.
A Study on the Multizone Modeling for Preventing Transmission of Air Borne Contagion
Choi, Sang-Gon ; Lee, Hyun-Woo ; Hong, Jin-Kwan ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 933~940
In this study multi-zone modeling program CONTAM 2.4 developed by NIST is used for estimating the air disinfection rate of the interior of a room which is set up the indoor air disinfection system with filter and ultra violet germicidal irradiation (UVGI). Developed models those enable to predict the transmission of air home contagion such as bacteria and fungus generated in our daily life are useful model for designning air cleaning & ventilation system of building. Also, results indicate that these models are enable to compute the real situation that is almost impossible of carrying out experiment in an actual condition due to biohazard problems and suggest that engineers will use these models as a design tool for the future immune building system.
A Study on Performance Characteristics due to the Degree of Superheat in Freon Refrigerating System - The Comparison of Heat Exchanger Types -
Hong, Suck-Joo ; Ha, Ok-Nam ; Kwon, Il-Wook ; Yun, Kab-Sig ; Hong, Sung-In ; Kim, Jin-Hyun ; Kim, Yang-Hyun ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 11, 2006, Pages 941~946
Nowadays heat exchangers that have been applied for freon refrigerating systems, a shell and tube type condenser, but because of their large size, large space for installation and more amount of refrigerants are needed. Therefore, in this study, we will find the most suitable operating condition through the comparison of performance between the shell & tube type and shell & disk type heat exchanger with R22. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for the degree of superheat from 0 to
at each condensing pressure. As a result of experiment, if the shell & disk type heat exchanger is applied for R22 refrigerating systems, minimized input of refrigerants and space required for installation will be secured, which will have a great contribute to financial improvement for industry.