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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 23, Issue 12 - Dec 2011
Volume 23, Issue 11 - Nov 2011
Volume 23, Issue 10 - Oct 2011
Volume 23, Issue 9 - Sep 2011
Volume 23, Issue 8 - Aug 2011
Volume 23, Issue 7 - Jul 2011
Volume 23, Issue 6 - Jun 2011
Volume 23, Issue 5 - May 2011
Volume 23, Issue 4 - Apr 2011
Volume 23, Issue 3 - Mar 2011
Volume 23, Issue 2 - Feb 2011
Volume 23, Issue 1 - Jan 2011
Selecting the target year
The Effects of the Installation Conditions of Ground Loop Heat Exchanger to the Thermal Conductivity and Borehole Resistance
Lim, Hyo-Jae ; Kong, Hyoung-Jin ; Kang, Sung-Jae ; Choi, Jae-Ho ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 95~102
DOI : 10.6110/KJACR.2011.23.2.095
A ground loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. A proper design requires certain site specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U tube configurations on ground effective thermal conductivity and borehole thermal resistance. In this study, thermal response tests were conducted using a testing device to 9 different ground loop heat exchangers. From the experimental results, the length of ground loop heat exchanger affects to the effective thermal conductivity. The results of this experiment shows that higher thermal conductivity of grouting materials leads to the increase effective thermal conductivity from 22 to 32%. Also, mounting spacers have increased by 14%.
Study on Characteristics of a Droplet in Two-dimensional Channel with Moving Bottom Wall
Kim, Hyung-Rak ; Yoon, Hyun-Sik ; Jeong, Hae-Kwon ; Ha, Man-Yeong ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 103~110
DOI : 10.6110/KJACR.2011.23.2.103
A two-dimensional immiscible droplet deformation phenomena on moving wall in a channel has been investigated by using lattice Boltzmann method involving two-phase model. The dependence of the deformation of the droplet with different sizes on the contact angle and the velocity of bottom wall has studied. When the bottom wall starts to move, the deformation of the droplet occurs. For the largest bottom wall velocity, eventually, the deformation of the droplet is classified into the three patterns according to the contact angle.
Precise Temperature Control of Oil Coolers with Hot-gas Bypass Manner for Machine Tools Based on PI and Feedforward Control
Jeong, Seok-Kwon ; Byun, Jong-Yeong ; Kim, Sang-Ho ; Yoon, Jung-In ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 111~119
DOI : 10.6110/KJACR.2011.23.2.111
Recently, the performances of speed and accuracy are enhanced in machine tools. The high speed of the machine tools usually causes harmful thermal displacements on the objects. To reduce the thermal displacements, machine tools generally adopt oil coolers with precise temperature control function. This study aims at precise control of oil outlet temperature in the oil coolers with hot-gas bypass manner based on PI control logic. The control system was designed for obtaining steady state error within
and maximum overshoot with 0.8% even though abrupt disturbances are added to the system. We showed that the PI gains could be easily decided by numerical simulations using practical transfer function which got experiments. Also, transient characteristics could be improved significantly by reflecting the inlet temperature of an evaporator to the output of a controller feedforwardly considering periodic abrupt disturbances. Through some experiments, excellent control performances were established by the suggested control.
Numerical Simulation of a Fin-Tube Heat Exchanger for Waste Gas Heat Recovery
Nam, Myong-Hwan ; Maeng, Jae-Hun ; Koo, Byeong-Soo ; Jun, Yong-Du ; Lee, Kum-Bae ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 120~125
DOI : 10.6110/KJACR.2011.23.2.120
As an effort to secure economically viable heat recovery units, innovative fin shapes for industrial boilers are studied for better performance. In the present study a numerical modeling for the analysis of heat exchanger performance is conducted using a commercial software, ANSYS CFX and the results are compared with the experimental data. Out of several candidate fin shapes curved wavy fin is selected for the present study. Both numerical and experimental data are directly compared for heat transfer rate and pressure drop with the assumed constant surface temperature of
. Exhaust gas is obtained from a test apparatus which supplies variable flow rates. The numerical results show reasonable agreements with the experimental data within 10% in terms of both total heat transfer and pressure loss.
Optimal Design of Vacuum Cleaner with a Multi Cyclone
Ha, Gun-Ho ; Kim, Eung-Dal ; Yang, Byung-Sun ; Ahn, Young-Chull ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 126~131
DOI : 10.6110/KJACR.2011.23.2.126
Cyclone, a type of particle collector widely used in the field of ambient sampling and industrial particulate control, is the principal type of gas-solids separator that uses a centrifugal force. The goal of this study is to design and evaluate the cyclone that can be used for the household vacuum cleaners. A multi cyclone with a 1st cyclone and several 2nd cyclones is designed to improve dust collection efficiency. The dust collection efficiency and the suction power of 1st cyclone are evaluated. And the dust collection efficiency and the suction power of multi cyclone are evaluated according to various sizes of inlet and vortex finder. As a result, a cone shape porous filter has better dust collection efficiency than a cylinder shape porous filter. The dust collection efficiency of a multi cyclone is 3.5% greater than that of a single cyclone.
Large Eddy Simulation of Heat Transfer Performance Enhancement due to Unsteady Flow in Compound Channels
Hong, Seong-Ho ; Shin, Jong-Keun ; Choi, Young-Don ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 132~138
DOI : 10.6110/KJACR.2011.23.2.132
In the present article, we investigate numerically turbulent flow of air through compound rectangular channels. Large eddy simulation(LES) is employed for unsteady turbulence modeling. LES gives better predictions for the axial mean velocity distribution than those of other turbulent models. Strong large-scale quasi-periodic flow oscillations are observed in most of the geometries investigated. Such large-scale flow oscillations in compound rectangular channels are similar to the quasi-periodic flow pulsation through the gaps between fuel rod bundle in nuclear reactor. It exists in any longitudinal connecting gap between two flow channels. The frequency of this flow oscillation is determined by the geometry of the gap. The large scale cross motions through the rectangular compound channels induce significant heat transfer enhancement of the compound channel flow.
Ventilation Performance According to Outdoor and Operating Conditions of the Vertical Exhaust Duct System in High Riser Public Houses
Kim, Young-Bae ; Kim, Jae-Hong ; Sung, Jae-Yong ; Lee, Myeong-Ho ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 139~146
DOI : 10.6110/KJACR.2011.23.2.139
The ventilation performance of a vertical exhaust duct system in the high riser public house has been evaluated by a commercial software, Fluid Flow, which solves pressure losses through the duct system including bathroom fans and a hybrid roof fan. During the numerical simulations, outdoor wind condition and stack effects in summer and winter were considered as well as the operating conditions of a basement damper and the roof fan. The results show that the bathroom ventilation in summer is the most unsatisfactory. The opening of the basement damper has a problem that the polluted air in the lower floors is exhausted to the underground parking lot, not to the rooftop. If the basement damper is closed, the exhaust flow rate in the lower floors is not sufficient due to the strong flow resistance in the long vertical duct even though the roof fan is under operating.
Heat Transfer above Liquid Helium Surface in Cryostat
Choi, Yeon-Suk ; Kim, Dong-Lak ; Shin, Dong-Won ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 147~152
DOI : 10.6110/KJACR.2011.23.2.147
The cryogenic cooling load from the top plate of cryostat to liquid helium surface, including wall conduction, thermal radiation and current leads, is investigated in a closed cryostat system for superconducting magnet. In general methods of load estimation, individual load is calculated separately, however they are actually coupled each other because of natural convection of helium vapor. Using relevant heat transfer analysis, we calculate cryogenic load with taking into account the effect of natural convection. Cryogenic load is under-estimated approximately 1% when the natural convection is ignored. The difference between actual cooling load and cooling load by individual calculation increases with supplying current.
A Strategies to Improve the Natural Ventilation Performance at Underground Parking Lot in Multi-Residential Buildings
Seo, Jung-Min ; Lee, Joong-Hoon ; Song, Jong-Eui ; Jung, Jung-Hwa ; Song, Doo-Sam ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 153~163
DOI : 10.6110/KJACR.2011.23.2.153
Energy efficiency and indoor air quality have become main issue to develop healthy and sustainable building in these days. As an effort to reduce the energy consumption in multi-residential building, many attempts as like passive design strategies and renewable energy as well as active control method are tried. However, underground parking lot in multi-residential building seldom adopt the sustainable strategies and only mechanical system is installed as usual. Moreover, the mechanical system installed in underground parking lot is rarely operated due to the electric demand for operation after completion. In this study, as an energy efficient measure, natural ventilation system using stack effect as a driving force for underground parking lot will be proposed and the performance of the suggested system will be analyzed by simulation method.
Study on Pertinence for Environmental Energy Complex Town Construction
Kim, Young-Jun ; Lee, Jong-Yeon ; Kang, Yong-Tae ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 2, 2011, Pages 164~171
DOI : 10.6110/KJACR.2011.23.2.164
The objectives of this study are to propose a suitable treatment facility for waste energy recovery after analyzing the waste generation and disposal situation in Jejudo, to establish the plan to install the solar photovoltaics and wind power plant considering the site conditions and finally to establish the environmental energy town plan in conjunction with the existing facilities. The food waste biogas plant is selected as the treatment capacity of 200 ton/day. It is estimated that the biogas plant will produce the electricity of 7,594 MWh per year, which will reduce the greenhouse gas of 4,177
per year. The solar photovoltaics and wind power plant will produce the electricity of 13,410 MWh per year, which will reduce the greenhouse gas of 7,375
per year. Environmental energy town will give us the reduction of operating cost by centralized treatment of residues and byproducts, and by efficient utilization of produced energy.