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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 14, Issue 12 - Dec 2002
Volume 14, Issue 11 - Nov 2002
Volume 14, Issue 10 - Oct 2002
Volume 14, Issue 9 - Sep 2002
Volume 14, Issue 8 - Aug 2002
Volume 14, Issue 7 - Jul 2002
Volume 14, Issue 6 - Jun 2002
Volume 14, Issue 5 - May 2002
Volume 14, Issue 4 - Apr 2002
Volume 14, Issue 3 - Mar 2002
Volume 14, Issue 2 - Feb 2002
Volume 14, Issue 1 - Jan 2002
Selecting the target year
Effects of Refrigerant and Oil Charges on the Performance of an Refrigeration System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 617~625
In this study, effects of refrigerant and oil charges on the performance of a refrigeration system simulating an automobile air conditioner have been experimentally investigated using R134a and PAG oil. Measurements were taken in a breadboard type refrigeration test unit with a compressor used for a commercial automobile air-conditioner under a set of condition imposed upon normally to automobile air conditioners. Both the COP and capacity decreased rapidly as the oil charge increased because of the decrease in vapor pressure of the circulating refrigerant/oil mixture. The excess oil left in the evaporator also caused heat transfer degradation resulting in a decrease in capacity and in turn COP. It was found that there is an optimum refrigerant charge at which the COP becomes the maximum. Below this optimum charge, both the capacity and COP increased as the refrigerant charge increased and above the optimum charge, both of them remained almost constant. Hence, the COP seems to be the most important factor in determining the optimum refrigerant charge. When the system was undercharged, the refrigerant at the condenser exit lost subcooling and showed a sign of poor miscibility.
The Study on Cooling Load Forecast using Neural Networks
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 626~633
The electric power load during the peak time in summer is strongly affected by cooling load, which decreases the preparation ratio of electricity and brings about the failure in the supply of electricity in the electric power system. The ice-storage system and heat pump system etc. are used to settle this problem. In this study, the method of estimating temperature and humidity to forecast the cooling load of ice storage system is suggested. And also the method of forecasting the cooling load using neural network is suggested. For the simulation, the cooling load is calculated using actual temperature and humidity, The forecast of the temperature, humidity and cooling load are simulated. As a result of the simulation, the forecasted data is approached to the actual data.
The Study on Cooling Characterics of TMA Clathrate with Ethanol
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 634~640
The purpose of this study is to investigate the propriety of TMA clathrate as a cold storage medium. Particularly, this is to examine the extent of subcooling improvement when the additives is added to the TMA clathrate, because water used for cold storage ma terial has low phase change temperature and subcooling. This study has been analyzed and compared pure water with TMA 30 wt% clathrate how phase change temperature, subcooling and specific heat in the various concentrations are changed. This results prove low phase change temperature and subcooling control effect when the ethanol is added to the TMA 30 wt% clathrate than the TMA 30 wt% clathrate. In addition, it results low specific heat when there is added to the TMA 30 wt% clathrate over 0.5 wt% ethanol in the cold heat source temperature under
. The other side, it results high specific heat when the ethanol is added in it at the cold heat source temperature under
. Therefore, it is found that the additive must be controlled by available solution limit and study for new additive must be lasted to know its effect.
Characteristics of Absorption Heat Transfer on Micro-Scale Hatched Tubes with Different Surface Roughness
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 641~647
Objectives of this paper are to investigate the effect of roughness of micro-hatching tubes on the absorption performance and to develop on experimental correlation of Nusselt as a function of the roughness. Three different micro-scale hatched tubes and a bare tube were tested in the present experiment.
solution is used as working fluid. It was found that absorption performance of micro-scale hatched tubes were improved upto 2 times with an error band of
compared with the bare tube. An experimental correlation of Nusselt was developed as a function of the roughness.
A Study on the Gas Pulsation in a Rotary Compressor
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 648~655
For a discharge system of rotary compressor, analytical investigation on the discharge gas pulsation has been carried out. With the aid of four pole theory, acoustic impedance of the discharge system composed of muffler and cavities on both sides of motor with gas passages between them can be calculated using discrete acoustic elements described by transfer matrices, yielding the relationship between discharge mass flow rate and gas pulsation at the discharge port. This method of predicting the gas pulsation was validated by measurement data. Effects of change in discharge muffler geometries on the gas pulsation also were investigated, demonstrating that this method can be used for muffler design.
Flow Condensation Heat Transfer of R22, R134a, R407C, and R410A in Plain and Microfin Tubes
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 656~663
Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured on horizontal plain and microfin tubes. The experimental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water/glycol loop. The test section in the refrigerant loop was made of both a plain and a microfin copper tube of 9.52 mm outside diameter and 1.0 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of
with mass fluxes of 100, 200, and 300 kg/
. Test results showed that at similar mass flux the flow condensation HTCs of R134a were similar to those of R22 for both plain and microfin tubes. On the other hand, HTCs of R407C were lower than those of R22 by 11~l5% and 23~53% for plain and microfin tubes respectively. And HTCs of R410A were similar to those of R22 for a plain tube but lower than those of R22 by 10~21% for a microfin tube. In general, HTCs of a microfin tube were 2.0~3.0 times higher than those of a plain tube.
Heat Pipe Heat Sink Development for Electronics Cooling
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 664~670
A heat sink (HS) system using heat pipes for electronics systems was studied. The experimental results indicate that a cooling capacity of up to 150w 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. To do so, however, the interior temperature distribution had to be verified by experimental results. 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.
The Effect on Gas Adsoption Efficiency for Various Surface Characteristics
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 671~675
The gas adsorption efficiency for various surfaces with three different characteristics has been reviewed. The dimethyl disulfide gas has been used to investigate characteristics of gas adsorption for different surface characteristics such as plasma treated, lacquer coated and untreated. Three different surfaces were evaluated in dry conditions initially and tested at wet surface conditions with spraying water to evaluate the gas adsorption efficiency which usually occurred at defrost cycles. The results show that the gas adsorption of the plasma treated sample has better performance than others. The lacquer coated and untreated samples showed the similar result, but the lacquer coated sample showed a slightly better performance.
An Experimental Study on the Thermal Resistance Characteristics for Various Types of Heat Sinks
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 676~682
This paper has been made to investigate the thermal performance characteristics for the several types of heat sinks such as extruded heat sink, aluminum foam heat sink, layered heat sink. The various types heat sinks are prepared and tested for natural convection as well as forced convection. The experimental results for natural convection are compared to those for three types of heat sink so that the appropriate heat sink can be designed or chosen according to the heating conditions. The overall heat transfer performances for layered heat sink, extruded heat sink and aluminum foam heat sink are almost comparable to those under natural convection and forced convection. The forced convection of layered heat sink become 1.2 times as high as those of extruded heat sink, and the forced convection of extruded heat sink become 1.2 times as high as those of aluminum foam heat sink. This study shows that bar height, bar distance and number of bar for layered heat sink are important parameters, which have a serious influence on thermal performance for layered heat sinks.
Experimental Studies on Heat Transfer in the Annuli with Corrugated Tubes
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 8, 2002, Pages 683~689
This paper is to present the results of a comprehensive study on heat transfer in annuli with spirally corrugated inner tubes in the turbulent regime. Tube surface-temperature measurements were used to explain the enhancement phenomena in the annuli with several different corrugated tubes. Nusselt numbers were between 1.1 and 2 times the smooth annulus values. These enhancement values can be used to determine the appropriate range of applicability for spirally corrugated annuli.