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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
Performance of R290 and R1270 as Alternative Refrigerants of R22 According to Temperature Variations of Evaporator and Condenser
Baek In-Cheol ; Park Ki-Jung ; Shim Yun-Bo ; Jung Dong-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 761~767
In this study, performance of 2 pure hydrocarbons R290 and R1270 was measured in an attempt to substitute R22 under 3 different temperature conditions. They were tested in a refrigerating bench tester with a hermetic rotary compressor. The test bench provided about 3.5 kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions resulting in the average saturation temperatures of
in the evaporator and condenser, respectively. Test results show that the coefficient of performance (COP) of these refrigerants is up to 11.54% higher than that of R22 in all temperature conditions. Compressor discharge temperatures were reduced by
with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 58% as compared to R22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for residential air-conditioning and heat pumping application.
A Presumption of Water Supply Amount for Calculation of Equipment Capacity in High School Building
Park Yool ; Lee Hak-Soo ; Lee Sung ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 768~775
The water supply system has been designing by decision process such as calculation of water supply amount, capacity of water tanks and pumps, pipe size. Especially, when we estimate excessively water supply amount, the initial cost and running cost will increase according to enlargement of the water tank and pump capacity, and water quality of ground water tank can become worse. Therefore, calculation of water supply amount is basically most important factor. In order to calculate exactly water supply amount applying domestic real situation, we should set up basic data as well as study calculation methods. This research would consider calculation methods of water supply amount for school building through examine domestic and foreign basic data of water supply amount and characteristics of domestic school, and estimate daily water supply in high school.
A District Cooling System using Ice Slurry for the Uncertain Cooling Load of the Future and its Economic Evaluation
Lee Yoon-Pyo ; Ahn Young-Hwan ; Yoon Seok-Mann ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 776~782
A new district cooling system using ice slurry for the uncertain cooling load of the future is presented. The chilled water produced by the absorption chillers is used for the base cooling load. The temperature of the chilled water is reduced by mixing of ice slurry depending on increasing of the cooling load. Finally, IF of the ice slurry is increased up to 10% at the peak load. The transporting mass flow rate is decreased down to 44.7%, and the diameter of the main pipe is decreased down to 66.7%, but the diameter of the branched pipe is designed as the same size of the chilled water.
A Study on the Estimation of Soil Formation Thermal Conductivities and Borehole Resistances with One-Dimensional Numerical Model and In-Situ Field Tests
Lee Se-Kyoun ; Woo Joung-Son ; Ro Jeong-Geun ; Kim Dae-Ki ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 783~790
A one-dimensional numerical model coupled with parameter estimation is used to predict the effective thermal conductivities of soil formations and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time (IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. This method is used for single-U and double-U borehole system. The results of this method are compared and agreed well with those of existing software (GPM) in the analysis of single-U borehole data. In the analysis of double-U borehole data this method seems to be better in predicting soil and borehole properties.
Fault Diagnosis Algorithm of an Air-conditioning System by using a Neural No-fault Model and a Dual Fuzzy Logic
Han Do-Young ; Jung Nam-Chul ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 791~799
The fault diagnosis technologies may be applied in order to decrease the energy consumption and the maintenance cost of an air-conditioning system. In this paper, a fault diagnosis algorithm was developed by using a neural no-fault model and a dual fuzzy logic. Five different faults, such as the compressor valve leakage, the liquid line blockage, the condenser fouling, the evaporator fouling, and the refrigerant leakage of an air-conditioning system, were considered. The fault diagnosis algorithm was tested by using a fault simulation facility. Test results showed that the algorithm developed for this study was effective to detect and diagnose various faults. Therefore, this algorithm may be practically used for the fault diagnosis of an air-conditioning system.
Distribution of Air-Water Two-Phase Flow in a Flat Tube Heat Exchanger
Kim Nae-Hyun ; Park Tae-Gyun ; Han Sung-Pil ; Lee Eung-Ryul ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 800~810
The R-134a flow distribution is experimentally studied for a heat exchanger composed of round headers and 10 flat tubes. The effects of tube protrusion depth as well as mass flux, and quality are investigated, and the results are compared with the previous air-water results. The flow at the header inlet is stratified. For the downward flow configuration, the liquid distribution improves as the protrusion depth or the mass flux increases, or the quality decreases. For the upward configuration, the liquid distribution improves as the mass flux or quality decreases. The protrusion depth has minimal effect. For the downward configuration. the effect of quality on liquid distribution is significantly affected by the flow regime at the header inlet. For the stratified inlet flow, the liquid is forced to rear part of the header as the quality decreases. However, for the annular inlet flow, the liquid was forced to the frontal part of the header as the quality decreased. For the upward flow, the effect of the mass flux or quality on liquid distribution of the stratified inlet flow is opposite to that of the annular inlet flow. The high gas velocity of the annular flow may be responsible for the trend. Generally, the liquid distribution of the stratified inlet flow is better than that of the annular inlet flow. Possible explanation is provided from the flow visualization results.
A Study of Turbulence Generation Characteristics of Large Scale Vortex Flow Mixing Vane of Nuclear Fuel Rod Bundle
An Jeong-Soo ; Choi Yong-Don ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 811~818
Mixing vanes have been installed in the space grid of nuclear fuel rod bundle to improve turbulent heat transfer. Split mixing vanes induce the vortex flow in the cooling water to swirl in sub-channel of fuel assembly. But, The swirling flow decays rapidly so that the heat transfer enhancing effect limited to short length after the mixing vane. In the present study, the large scale vortex flow (LSVF) is generated by rearranging the mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about
after the spacer grid. The streamwise vorticity generated by LSVF sustain two times more than that split mixing vane.
Effect of Vanes on Flow Distribution in a Diffuser Type Recuperator Header
Jeong Young-Jun ; Kim Seo-Young ; Kim Kwang-Ho ; Kwak Jae-Su ; Kang Byung-Ha ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 819~825
In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about
than without using horizontal vanes.
Development of Nanofluidic Thermosyphon Heat Sink
Rhi Seok-Ho ; Shin Dong-Ryun ; Lim Taek-Kyu ; Lee Chung-Gu ; Park Gi-Ho ; Lee Wook-Hyun ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 826~834
A heat sink system using nanofluidic thermosyphon for electronics systems was studied. The experimental results indicate that a cooling capacity of up to 150 W at an overall temperature difference of
can be attainable. The heat sink design program also showed that a computer simulation can predict the most of the parameters involved. In the experimental study, the volume concentration of nano particles affect the system performance. Nanofluidic thermosyphon with 0.5% volume concentration showed the best performance. Nanofluid can increase CHF of the system compared with water as a working fluid. The current simulation results were close to the experimental results in acceptable range. The simulation study showed that the design program can be a good tool to predict the effects of various parameters involved in the optimum design of the heat sink.
Experimental Study on the Cooling Performance Improvement of a Two-stage Compression
Cho Hong-Hyun ; Lee Ho-Seong ; Kim Yong-Chan ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 835~841
system using the two-stage compression cycle was tested by varying
compressor frequencies in the cooling mode. To improve the cooling performance of the two-stage compression
cycle, the following cycle options were applied: a basic cycle, a cycle with an intercooler, a cycle with an IHX (internal heat exchanger), and a cycle with an intercooler and IHX. The cycle with the intercooler-IHX showed the highest cooling capacity improvement among the cycle options at all compressor frequencies. The cycle with the intercooler, the cycle with the IHX, and the cycle with the intercooler-IHX improved the cooling COP by 7, 12, and 15%, respectively, over the basic
cycle when the compressor frequencies for the first and second compressors were 50 Hz and 30 Hz, respectively. In addition, the applications of the selected cycle options enhanced system reliability.
Enhancement of Pool Boiling Heat Transfer Coefficients with the Use of Carbon Nanotubes
Park Ki-Jung ; Jung Dong-Soo ;
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 18, issue 10, 2006, Pages 842~849
In this study, the effect of carbon nanotubes (CNTs) on boiling heat transfer is investigated. Three refrigerants of R22, R123, R134a, and water are used as base working fluids and 1% of CNTs by volume is added to the base fluids to study the effect of CNTs. All data are obtained at the pool temperature of
for all refrigerants and
for water in the heat flux range of
. Test results show that CNTs increase the boiling heat transfer coefficients for all fluids. Especially, large enhancement was observed at low heat flutes. With increasing heat flux, however, the enhancement was suppressed due to vigorous bubble generations. Fouling was not observed during the course of this study. Optimum quantity and type of CNTs and their dispersion should be examined for their application in pool boiling heat transfer.