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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
A Comparative Study on the Effect of THF and Oxidized Carbon Nanotubes for Methane Hydrate Formation
Park, Sung-Seek ; An, Eoung-Jin ; Kim, Nam-Jin ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 769~775
DOI : 10.6110/KJACR.2011.23.12.769
Methane hydrate is formed by physical binding between water molecules and methane gas, which is captured in the cavities of water molecules under the specific temperature and pressure.
hydrate of pure methane can be decomposed to the methane gas of
and water of
at standard condition. Therefore, there are a lot of practical applications such as separation processes, natural gas storage transportation and carbon dioxide sequestration. For the industrial utilization of hydrate, it is very important to rapidly manufacture hydrate. So in this study, hydrate formation was experimented by adding THF and oxidized carbon nanotubes in distilled water, respectively. The results show that when the oxidized carbon nanofluids of 0.03 wt% was, the amount of gas consumed during the formation of methane hydrate was higher than that in the THF aqueous solution. Also, the oxidized carbon nanofluids decreased the hydrate formation time to a greater extent than the THF aqueous solution at the same subcooling temperature.
Operating Characteristics of a Scroll Expander Used in Organic Rankine Cycle
Shin, Dong-Gil ; Kim, Young-Min ; Kim, Chang-Gi ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 776~781
DOI : 10.6110/KJACR.2011.23.12.776
The rapid increases in global energy demand and global warming need renewable energy sources such as solar thermal energy, biomass energy and waste heat. A ORC-based micro-CHP system(< 10 kWe) is one of the effective means to use renewable energy and solve energy problems because of its compactness, flexibilities and lower cost compared to other systems. The most important core components of the ORC is the expander which has a strong effect on the cycle efficiency. In the range of power output from 1 to 10 kW, the scroll expander is a good choice due to its performance and reliability. In this study, we have carried out an experimental study on an ORC equipped with oil-free scroll expander working with refrigerant R134a. We have measured power output and thermal efficiencies of the ORC and analyzed correlation between volumetric efficiencies of the expander and thermal efficiencies of the ORC.
Optimum Controller Design of a Water Cooler for Machine Tools Based on the State Space Model
Jeong, Seok-Kwon ; Kim, Sang-Ho ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 782~790
DOI : 10.6110/KJACR.2011.23.12.782
Typical temperature control methods of a cooler for machine tools are hot-gas bypass and compressor variable speed control. The hot-gas bypass system has been widely used to control the cooler temperature in many general industrial fields. On the contrary, the compressor variable speed control is focused on special fields such as aerospace and high precision machine tools which need high precision control. The variable speed control system usually has two control variables such as target temperature and superheat. In other words, the variable speed control system is basically multi-input multi-output(MIMO) system. In spite of MIMO system, the proportional integral derivative(PID) feedback control methodology that based on single-input single-output (SISO) system is generally used for designing the variable speed control system. Therefore, it is inevitable to describe transfer functions for dynamic behaviors of every controlled variables and decide the PID gains with tremendous iteration process. Moreover, the designed PID gains do not provide optimum system performances. To solve these problems, high performance controller design method based on a state space model is suggested in this paper. An optimum controller is designed to minimize both control errors and energy inputs. This method was more simple to describe dynamic behaviors and easier to design the cooler controller which is MIMO system.
Performance of HFC32/HFC125 Mixtures for Heat Pumps
Kim, Wook-Jin ; Kang, Dong-Gyu ; Lee, Yo-Han ; Jung, Dong-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 791~798
DOI : 10.6110/KJACR.2011.23.12.791
In this study, performance of R410A(50%R32/50%R125) and HFC32/HFC125 mixture is measured to examine the effect of composition shift of R410A used for various air-conditioners and heat pumps. The composition of HFC32/HFC125 mixture varies from the reference composition of R410A
with 5% interval. Tests carried out in a heat pump bench tester at the evaporation and condensation temperatures of
for summer and winter conditions, respectively. Test results show that both the coefficient of performance (COP) and compressor power of the HFC32/HFC125 mixture have the maximum difference of 2.0% as compared to those of R410A. Compressor discharge temperatures of HFC32/HFC125 mixture are increased up to
as compared to that of R410A. The amount of charge for HFC32/HFC125 mixture vary within 5.6% as compared to that of R410A. Overall, performance of R410A is not appreciably affected by the composition shift of
of R32 under both air-conditioning and heat pumping conditions.
Performance of the Exhaust Filtration System of Hot Cell at PIEF
Hwang, Yong-Hwa ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 799~804
DOI : 10.6110/KJACR.2011.23.12.799
Radioactivity of high concentrations have existed in the handling nuclear materials in hot cell of PIEF(Post Irradiation Examination Facility). The exhaust filtration system was enabled to process cylindrical filters by using a manipulator in the hot cell. By establishing a double filtration system with two filters, backup protection against leakage or failure of the first is provided by the second filter. Additionally, this a arrangement is arrange intended to increase the total filtration efficiency. The result of the pressure drop changing in the air flow of the cylindrical and HEPA filters is observed by a curved line. A filtering efficiency of more than 99.99% to
particle appears in the upstream and downstream during the efficiency test on the HEPA filters. The V-pleats type had a lower pressure drop than the separator type. There was no damage during usage and was found to be suitable with high capacity of air volume. Therefore, by carrying out performance tests of the exhaust filtration system, efficiency and safety can be achieved.
Numerical Study on Flow and Heat Transfer Enhancement in a Cooling Passage with Protrusion-In-Dimples
Kim, Jeong-Eun ; Ha, Man-Yeong ; Yoon, Hyun-Sik ; Doo, Jeong-Hoon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 805~814
DOI : 10.6110/KJACR.2011.23.12.805
In the present study, the detailed flow structure and heat transfer characteristics in the newly-designed heat transfer surface geometry were investigated. The surface geometry proposed in the present study is a traditional dimple structure combining with a protrusion inside the dimple, which is named a protrusion-in-dimple in this study. The basic idea underlying the present surface geometry is to enhance the flow mixing and the corresponding heat transfer in the flow re-circulating region generated by a conventional dimple cavity. The present study was performed by the direct numerical simulation at a Reynolds number of 2800 based on mean velocity and channel height and Prandtl number of 0.71. Three different protrusion heights for protrusion-in-dimples were considered as the main design parameter of the present study. The calculated pressure drop and heat transfer capacity were assessed in terms of the Fanning friction factor and Colburn j factor. The overall performances estimated in terms of the volume and area goodness factor for protrusion-in-dimple cases were higher than the conventional dimple case.
Design of a Scroll Expander for Waste Heat Recovery from Engine Coolant
Yu, Je-Seung ; Kim, Hyun-Jae ; Kim, Hyun-Jin ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 815~820
DOI : 10.6110/KJACR.2011.23.12.815
A scroll expander was designed for an energy converter from waste heat of IC engine coolant to useful shaft work. The scroll expander is to run in a Rankine cycle which receives heat energy transferred from engine coolant circulation cycle. The working fluid was Ethanol. For axial compliance, a back pressure chamber was provided on the rear side of the orbiting scroll. Lubrication oil was delivered by a positive displacement type oil pump driven by the shaft rotation. Performance analysis on the scroll expander showed that the expander efficiency was 63.4%. It extracts shaft power of 0.6 kW out of engine coolant waste heat of 17.5 kW, resulting in the Rankine cycle efficiency of 3.43%.
Development of a Simple Analytical Model for Desiccant Wheels-I. Approximate Solution of the Governing Equations
Kim, Dong-Seon ; Choi, Young-Don ; Lee, Dae-Young ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 821~827
DOI : 10.6110/KJACR.2011.23.12.821
A simple analytical model has been developed from the approximate solution of the governing equations for desiccant wheels. The model has been compared with a numerical twodimensional transient model and found capable of making realistic prediction. The analytical model will be further developed to provide simple effectiveness correlations which can be useful for the rough design or long-term simulation of the desiccant wheels in DEC systems.
A Numerical Analysis on the Indoor Air Ventilation by Stack Effect and Outdoor Wind in a High-rise Residential Building
Kim, Chi-Wan ; Lim, Tae-Kun ; Ahn, Young-Chull ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 828~835
DOI : 10.6110/KJACR.2011.23.12.828
The purpose of this study is to analyze and evaluate the 3 types of indoor ventilation methods such as natural, mechanical, and hybrid ventilation in high-rise building which is affected by stack effect and outdoor air pressure. For the evaluation of the ventilation capacity, CFD simulation was performed in a typical high-rise residential building. The results of the simulations are as follows: 1) Natural ventilation method is not enough to the regulation. 2) In case of mechanical ventilation, congested area is occurred but meets the regulation. 3) In case of hybrid ventilation with stack effect, all the areas of indoor meet the regulation and congested area is reduced. 4) In case of high-rise building, the differences of ventilation rate among houses in the building are not large because the mechanical ventilation is main factor.
Modeling of Stochastic Properties of Internal Heat Generation of an Office Building for Slab Cooling Storage
Jung, Jae-Hoon ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 836~842
DOI : 10.6110/KJACR.2011.23.12.836
It has been shown that the air-conditioning system with slab cooling storage is effective in cutting peak load and utilizing nighttime electric power. The stochastic properties of internal heat generation which has great influence on the cooling load are examined in this paper. Based on the measured cooling load and electric power consumption in an office building with slab cooling storage, stochastic time series models to simulate these random processes are investigated. Furthermore, a calculated result by an optimal control method of thermal analysis taking into account the internal heat is compared with the measured cooling load.
Study on a Shape Deformation of Water Meniscus for the Rectangular and Circular Tips Moving Horizontally
Kim, Sang-Sun ; Son, Sung-Wan ; Ha, Man-Yeong ; Yoon, Hyun-Sik ; Kim, Hyung-Rak ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 23, issue 12, 2011, Pages 843~851
DOI : 10.6110/KJACR.2011.23.12.843
A two-dimensional immiscible water meniscus deformation phenomena on a moving tip in a channel has been investigated by using lattice Boltzmann method involving two-phase model. We studied the behavior of a water meniscus between the tip and a solid surface. The contact angles of the tip and a solid surface considered are in the range from
. The velocity of the tip used in the study are 0.01, 0.001, and 0.0001. The shapes of tip considered are rectangular and circular. The behavior of water confined between the tip and a solid surface depends on the contact angles of the tip and a solid surface, and the tip velocity. When the tip is moving, we can observe the various behaviors of shear deformation of a water meniscus. As time goes on, the behavior of a water meniscus can be classified into three different patterns which are separated from the tip or adhered to the tip or sticked to a solid surface according to the contact angles and the tip velocity.