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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 16, Issue 12 - Dec 2004
Volume 16, Issue 11 - Nov 2004
Volume 16, Issue 10 - Oct 2004
Volume 16, Issue 9 - Sep 2004
Volume 16, Issue 8 - Aug 2004
Volume 16, Issue 7 - Jul 2004
Volume 16, Issue 6 - Jun 2004
Volume 16, Issue 5 - May 2004
Volume 16, Issue 4 - Apr 2004
Volume 16, Issue 3 - Mar 2004
Volume 16, Issue 2 - Feb 2004
Volume 16, Issue 1 - Jan 2004
Selecting the target year
Effects of Relative Humidity on the Evaporator Pressure Drop
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 397~407
It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7
and mass flux varied from 150 to 250 kg/
s. The condition of air was dry bulb temperature of 27
, air Velocity Varied from 0.38 to 1.6 m/s. Experiments Showed that air Velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5
, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.
Prediction of Oil Lifetime due to Overheating of Oil and Bearing Housing in a Pump
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 408~413
An experimental study has been carried out to investigate overheating of oil and bearing housing during pump operation. This problem is of particular interest in the pre diction of lifetime and failure of pump. Transient variation of oil temperature as well as bearing housing temperature is measured to study the effect of oil viscosity, oil amount, and discharge flow rate of pump. It is found that optimal oil quantity as well as proper viscosity of oil is required to keep the safe temperature level of oil and bearing housing in a pump. The oil temperature at steady state is almost not affected by discharge flow rate in the range of discharge flow rates considered in the present study.
An Experimental Study on Heat Transfer and Pressure Drop Characteristics during Supercritical Process of Carbon Dioxide in a Horizontal Tube
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 414~420
The heat transfer and pressure drop characteristics associated with the gas cooling of the supercritical carbon dioxide in a horizontal tube have been investigated experimentally. This problem is of particular interest in the design of a gas cooler of cooling systems using
refrigerant. The test section is consisted of 6 series of 455 mm in length, 4.15 mm ID copper tube, respectively. The effects of the inlet temperature, pressure and mass flow rate on the heat transfer and pressure drop of
in a horizontal tube is studied in detail. The heat transfer coefficient of
is varied by temperature, inlet pressure, and mass flow rate of
. This has maximum value at near the pseudocritical temperature. The pressure drop is changed by inlet pressure and mass flow rate of
. The results have been compared with those of previous work. The heat transfer correlation at the supercritical gas cooling process is also suggested.
A Study on the Individual Room Control of Radiant Floor Heating System in Apartment Buildings
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 421~429
In Korea, the radiant heating system has been widely used as a residential heating method, which has been modernized to use hot water running into the tubes embedded in the floor structure. According to the recent improvement of living standard of residential buildings, the requirement of the thermal comfort and energy saving in heating system has been raised. Until now, the radiant floor heating system has been controlled by room thermostat installed in the living room, but for better thermal comfort, an individual room control method is adopted as an alternative. Therefore, it is necessary to evaluate the control performance between the current control method and the individual room control method. In this study, the control performance between the two systems is evaluated through the field experiment. And the control performances of room air temperature and energy performances are analyzed through the simulation using TRNSYS. Firstly, the simulations are performed in the various outdoor conditions and the flow rates and the simulation results are analyzed for the control performances. Also, to evaluate the energy performance, the simulations are performed under the operating conditions in which the set-point of the room air temperature is fixed or changed according to the schedule of occupancy, and the simulation results are analyzed between the two methods.
A Study on the Thermal and Electrical Characteristics with Manufacture of the Heating Element by Using Carbon with Bar Type
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 430~437
This paper is intended as an investigation of study on the thermal and electrical characteristics of the carbon heating element. In this experimentation, the electric material used is the crystalline graphite a kind of natural graphite. The bentonite is used to solidify the heating element and the vacuum furnace is used for sintering it. It is noted that the natural drying time should be at least 58 hours. The plating of the electric pole with the electroless nickel showed the lowest contact resistance among others. The resistance shows linear variation with regard to length. For the insulation and resolution, the glaze coating is best with 80% of water content. The temperature rising characteristic of the heating element is better than sheath heater saving 43% of rising time. The correlation equation for temperature was obtained with the electric power.
Performance Analysis of a 5 RT Air-Cooled
Absorption Chiller with the Variations of Heat Input and Ambient Temperature
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 438~443
The objective of this paper is to study the effects of the input gas flow rate and the ambient temperature variation on the absorption cycle performance. An air-cooled NH
absorption chiller is tested in the present study. The nominal cooling capacity of the single effect maching is 17.6 ㎾ (5.0 USRT). The cooling capacity, coefficient of performance, burner efficiency, and each state point are measured with the variations of the heat input and the ambient temperature. It is found that the COP and cooling capacity increase with increasing the generator exit temperature up to a certain temperature and then decrease. It is also found that the COP and the cooling capacity decrease with increasing the ambient temperature. The maximum COP of 0.51 is obtained from the present experiment.
Flow Condensation Heat Transfer Coefficients of R22 Alternative Refrigerants in Plain and Microfin Tubes of 6.0 mm Inside Diameter
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 444~451
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 6.0∼6.16 mm inside diameter and 1.0 m length. Refrigerants were cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of 4
with mass fluxes of 100, 200, and 300 kg/m2s. 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 4∼16% and 16∼42% 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 3∼9% for a microfin tube. Heat transfer enhancement factors of a microfin tube were 1.3∼1.9.
Effect of Outdoor Temperature on the Refrigerant Behavior in the Compressor of a Heat Pump Operating at Heating Mode
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 452~458
The major cause of compressor failure is the decrease of oil viscosity due to floodback. In most previous researches on the compressor reliability, the relationship between oil circulation rate and performance or oil viscosity has been studied. Another research topic is flow visualization by using a sight glass on the bottom of a compressor sump area and accumulator. Both oil film thickness and oil level through the sight glass should be assessed for compressor reliability if the oil content of the mixture is small and low viscosity raise poor lubrication of pump bearing. In this study, the compressor reliability was assessed by measuring the viscosity of the mixture and calculating oil film thickness. The analysis of the relationship between bottom shell super heat and oil film thickness at heating operation was peformed. It is concluded that bottom shell superheat does not perfectly stand for the mixture's behavior for a low ambient heating operation and oil film thickness can give more detailed and direct criteria for compressor reliability
Analysis of Heating Energy in a Korean-Style Apartment Building 2: The Difference according to Heating Type
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 459~466
In order to save the energy in apartment houses, it is essential that the energy amount consumed in heating per household should be surveyed and analyzed according to heating method, which can be classified into unit, central and district methods. As a basis, we selected the household with nominal area of 32 py. because it accounts for the most percentage in Korea. It is estimated that the gas amount for cooking is 90 ㎥ and the energy amount for hot water supply is 11.41 GJ for a year, which is necessary to calculate the heating energy. Through the survey of actual energy consumption in Seoul and Gyeonggi, the energy amount used in heating can be obtained according to the heating type: 26.02 GJ/year for the unit heating, 28.09 GJ/year for the central heating and 40.61 GJ/year for the district heating.
Effects of Surface Roughness on Evaporation Cooling of Single Water Droplet in Radiative Fields
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 467~474
This paper presents the results of an experimental investigation for the effect of radiant heat on the evaporation cooling of water droplet in the process of fire extinguishing. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter. The range of surface temperature is T
, surface roughness is R
and the droplet diameter is
=3.0 mm in the radiation. The results show that the evaporation time is shorter for the larger surface roughness and the volume of droplet increased when the surface roughness is 0.64
at the surface temperature 127
. When the surface roughness is 0.64
, the heat flux is larger than the surface roughness is 0.08
at the surface temperature 81
Wafer Motion Control of Clean Tube System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 475~481
This paper presents a force model of the clean tube system, which was developed as a means of transferring air-floated wafers inside a closed tube filled with super clean air. The recovering force from the holes for floating wafers is modeled as a linear spring and thus the wafers motion is modeled as a mass-spring-damper system. The propelling forces are modeled as linear along with the wafer location. The paper also proposes a control method to emit and stop a wafer at the center of a control unit. It reveals the minimum value of the propelling force to leave from the control unit. In order to stop the wafer, it utilizes the exact time when the wafer arrives at the position to activate the propelling force. Experiments with the clean tube system built for the 12 inch wafer shows the validity of the proposed model and the algorithm.
The Experimental Study on the Efficiency of Ventilation of Korean Paper (Hanji)
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 482~489
The purpose of this study is to reevaluate the performance of Hanji as a architectural material. Recent studies report that one of the causes of the Sick-HouseㆍSick-Building Syndrome is due to the contaminants from interior materials and the lack of ventilation. In this study, the properties of Hanji are investigated. The major focuses of this research are (1) how efficient the Hanji is for ventilation of the house and (2) whether the usage of Hanji brings required ventilation volume to the house. According to the test results, differential pressure in the air and the amount of ventilation showed linear relationship. Test results differ from various kinds of Hanji. Since houses usually have double window system, Hanji can be used to the windows system, especially for inner part of double window system. It is suggested that the combination of Hanji windows for the inner part and glass windows for outer part is very effective, and offers a solution to improvement of indoor air quality and the lack of ventilation with passive ventilation that has less energy consumption.
Study on the Experiment and Numerical Computation of Forced Convection Heat Transfer around Circular Cylinder in a Rectangular Duct
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 5, 2004, Pages 490~498
This paper measures the forced convective heat transfer from heated cylinder to air flow in a rectangular duct at Re
=2,337, 4,589, 6,621 and 7,944 through experiments. And the heat transfer is computed by 3-D numerical computation in which various turbulent models are applied. It is shown through the comparison of experimental and computed data that numerical computation with standard k-
model predicts the experimental data most accurately. Furthermore, the correlation from the computed heat transfer is almost similar to that from the experiment when Re
is greater than 4,589. In addition, the correlation of McAdams is the closest to that from experimental data among various correlations from literature in the range of Reynolds number.ber.