Go to the main menu
Skip to content
Go to bottom
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 13, Issue 12 - Dec 2001
Volume 13, Issue 11 - Nov 2001
Volume 13, Issue 10 - Oct 2001
Volume 13, Issue 9 - Sep 2001
Volume 13, Issue 8 - Aug 2001
Volume 13, Issue 7 - Jul 2001
Volume 13, Issue 6 - Jun 2001
Volume 13, Issue 5 - May 2001
Volume 13, Issue 4 - Apr 2001
Volume 13, Issue 3 - Mar 2001
Volume 13, Issue 2 - Feb 2001
Volume 13, Issue 1 - Jan 2001
Selecting the target year
Flow Characteristics of Refrigerant-oil Mixtures in a Dehumidifying Cycle
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 1~8
This paper deals with refrigerant-oil mixtures in a dehumidifying cycle. Two different oils such as Alkylbenzene(AB) and Polyol-esters(POE) lubricants are used for R134a to investigate the effect of miscibility on oil returnability. It was found that R134a/AB mixture had more unstable interface between oil and refrigerant than R134a/POE mixture. However, overall flow patterns of both refrigerant-oil mixtures were almost same. The minimum height of oil measured in the compressor was as high as twice of the least permissible height of oil in the compressor required to insure its reliability. Thus, it is considered that immiscible oil, i. e., AB for R134a can be used without causing oil returnability problem.
R-134a Flow Boiling on a Plain Tube Bundle
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 9~17
In this study, flow boiling experiments were performed using R-134a on a plain tube bundle. Tests were conducted for the following range of variables; quality from 0.1 to 0.9, mass flux from
and heat flux from
. The heat transfer coefficients were strongly dependent on the heat flux. However, they were almost independent on the mass flux or quality. The data are compared with the modified Chen model, which satisfactorily (
Analysis of Woven Wire Wick Structure for a Miniature Heat Pipe
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 18~24
Woven wire wick is very effective structure because of its easiness to insert inside of pipe for a miniature heat pipe. The present study was conducted to investigate the effect of the effective flow passage with respect to wire helix angle. Also effective thermal conductivity were examined by defining mean porosity considering effective liquid flow passages. Effective heat transfer area is varied with respect to wire helix angle, and in the range of
, heat transfer area is decreased about 15~20%. Permeability of woven wire wick shows similar value of 200 mesh screen wick. And comparison of experimental results on effective thermal conductivity shows a fairly good agreement with the analytical results.
A Study on the Effect of the Heat Transfer Surface Position to the Condensation heat Transfer
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 25~29
A study has been conducted to investigate the effect of the heat transfer surface position in the range of dropwise condensation, filmwise condensation, and glacial condensation. For dropwise condensation promoter, the heat transfer surface was evaporated by gold. As a result, heat transfer rate is almost same where the position of heat transfer surface is between 45 and 135 degree. It is found that heat transfer rate was reduced as subcooled degree was increased. And it is also found that if the subcooled degree becomes lower, the position of heat transfer surface is more effective. Adversely, if the subcooled degree becomes higher, the effectiveness of surface position is getting relatively lower. Regardless of the position, the transition temperatures from dropwise condensation to filmwise condensation is in the vicinity of 80K.
A Study on Determining the Optimal Stop Time of HVAC System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 30~37
The purpose of this study is to present the method to determine the optimal stop time of HVAC using Artificial Neural Network model, one of the learning methods. For this, the performance of determining the stop time of HVAC for unexperienced learning data was evaluated, and time interval for measurement of input data and permissible error needed for practical application of ANN model were presented using the results of daily simulation.
Analysis on the Thermal Characteristics of Variable Conductance Heat Pipe
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 38~47
The operation characteristics of variable conductance heat pipe(VCHP) were numerically investigated by using 1-dimensional diffuse-front model. For different boundary conditions, the amount of non-condensible gas charge and dimension of gas reservoir were obtained by iterative calculation. It is found that the amount of non-condensible gas charge and dimensions of gas reservoir have an effect on the temperature control of condenser for the given operating condition of VCHP. The numerical results show that VCHP has an excellent capability of temperature control when subjected to a change in the heat input.
Optimization Study of the Compression/Absorption Hybrid Heat Pump Cycle
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 48~58
For the past few decades the vapor compression cycle with a solution circuit (VCCSC) has been known to provide high efficiency and variable capacity. In this study performance of a VCCSC cycle is examined through computer simulation. In the simulation heat exchangers were modelled by specifying UA or effectiveness values while the compressor performance was specified by an isentropic efficiency. Aqua/ammonia solution was chosen as the working fluid which can be used in the high temperature range. The results show that there exists an optimum operation condition which is dependent upon the temperatures of the external heat transfer fluids(HTFs). Besides the HTF\`s temperature, the maximum system pressure and the size of the solution heat exchanger are shown to have an influence on the optimum operation condition. Finally, as compared to a simple vapor compression heat pump with HFC134a, the COP of the VCCSC is shown to be 2∼22% higher.
A PID Control of Electric Heater for PEM
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 59~65
The work presented here is an implementation of PID control to achieve a required supply air temperature in PEM(Personal environment module). In PEM, the air is heated to the required temperature while it flows through the supply duct, without any mixing chamber. This makes the control of air temperature in PEM difficult. Linear dynamic model of heat transfer in PEM is first obtained. Then P, PD and PID type control systems, to provide the rapid response without overshoot and saturation, are designed and implemented experimentally. Data obtained shows that the control system satisfied the design criteria and works properly in controlling the supply air temperature.
An Experimental Study on the Performance of an Inverter Heat Pump with a Variation of Frequency and Refrigerant Charging Amount
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 13, issue 1, 2001, Pages 66~71
In the air-conditioning industry, the refrigerant charging amount is one of the most important parameters affecting the energy efficiency ratio of heat pumps. An experimental study was performed on the characteristics of an inverter driven air-to-air heat pump system with a variation of compressor frequency and charging amount of refrigerant. The frequency was altered from 40Hz to 70Hz and the charging amount was changed from 1.6kg to 2.8kg in tests. The variation of performance was measured with switching of the expansion valve on each frequency and charging amount. All the tests were performed at the Korean Standard and test conditions of the air conditioners. As results, it was found that there existed the charging amount and the level of the suction gas superheat which provided the highest energy efficiency ratio at all the frequency bands.