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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
The Effects of Additives on the Thermal Properties of a Clathrate Compound (II) -The Case of Ethylene Glycol-
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 499~505
The objective of this study is to investigate the effect of supercooling repression on the TMA clathrate by adding ethylene glycol. For this purpose, phase change temperature, supercooling, specific heat, latent heat and rate of volume change were measured and evaluated experimentally for heat source temperatures of -6
. The results show that supercooling was decreased. Thus the experimental results are expected to be used for the increase of coefficient of performance of low temperature thermal storage system in the building.
Life-Cycle Cost Analysis of Solution Transportation Absorption System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 506~513
The objective of this paper is to evaluate the economic performance of latent and sensible energy transportation systems. LCC (Life-Cycle Cost) analysis is a practical method and a guideline for evaluating the economic performance of considered systems during the Life-Cycle Period. By comparing the LCC of alternatives, The most ideal alternative is determined which has the lowest LCC. It is concluded that the cost of STA (Solution Transportation Absorption system) can be reduced by 67% to that of sensible energy transportation for study period with 10 km transportation distance.
Study on Heat Recovery System using Waste Biomass
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 514~521
Waste heat recovery system was studied numerically and experimentally. Heat exchanger system was designed specially to obtain the optimum heat exchanging performance. Brushwood biomass was used for the present experimental study. Two biomass heat recovery systems were designed and developed. Polyethylene helical pipe line of 0.03 m (inner diameter) was installed to recover the heat of biomass dump. The fermentation process of biomass dump was maintained for 12 weeks. The inner average temperature of biomass was about 51
for both hot exchanger systems. The current heat recovery system could recover up to 6 ㎉/kg of energy.
A Study of External Condensation Heat Transfer of Flammable Refrigerants
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 522~529
In this study, external condensation heat transfer coefficients (HTCs) of flammable refrigerants of propylene, propane, isobutane, butane, DME, and HFC32 were measured on a horizontal plain tube, 26 fpi low fin tube, and Turbo-C tube. All data were taken at the temperature of 39
with a wall subcooling of 3∼8
. Test results showed a typical trend that condensation HTCs of flammable refrigerants decrease with increasing wall subcooling. HFC32 had the highest HTCs among the tested refrigerants showing 44% higher HTCs than those of HCFC22 while DME showed 28% higher HTCs than those of HCFC22. HTCs of propylene and butane were similar to those of HCFC22 while those of propane and isobutane were similar to those of HFC134a. Based upon the tested data, Nusselt's equation is modified to predict the plain tube data within a deviation of 3%. For 26 fpi low fin tube, Beatty and Katz equation predicted the data within a deviation of 7.3% for all flammable refrigerants tested. The heat transfer enhancement factors for the 26 fpi low fin and Turbo-C tubes were 4.6∼5.7 and 4.7∼6.9 respectively for the refrigerants tested indicating that the performance of Turbo-C tube is the best among the tubes tested.
Characteristics of Evaporative Heat Transfer and Pressure Drop of Carbon Dioxide and Correlation Development near the Critical Point
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 530~537
In recent years, carbon dioxide among natural refrigerants has gained consider-able attention as an alternative refrigerant due to its excellent thermophysical properties. However, few investigations have been performed to develop useful correlations of heat trans-fer coefficients and pressure drop during evaporation of carbon dioxide. This study is aiming at providing the characteristics of heat transfer and pressure drop during the evaporation process of carbon dioxide. Heat is provided by a direct heating method to the test section, which was made of a seamless stainless steel tube with an inner diameter of 7.53 mm, and a length of 5.0 m. Experiments were conducted at saturation temperatures of -4 to 2
, heat fluxes of 12 to 20 ㎾/
and mass fluxes of 200 to 530 kg/
s. A comparison of different heat transfer correlations applicable to evaporation of carbon dioxide has been made. Based on the experiments for evaporation heat transfer and pressure drop, new correlations were developed. The newly developed empirical correlations for the heat transfer and pressure drop show average absolute deviations of 15.3% and 16.2%, respectively.
Experimental Studies on Heat Transfer and Pressure Drop Characteristics during Gas Cooling Process of Carbon Dioxide in the Supercritical Region
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 538~545
This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tube in which carbon dioxide flows is made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg/
s and inlet pressures are adjust-ed from 7.5 to 8.8 ㎫. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by the Blasius' equation. Based on the experimental data, a new empirical correlation to estimate the near-critical heat transfer coefficients has been developed.
Investigation of Local Convective Heat Transfer around a Circular Tube in Cross Flow of Air
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 546~555
With circular tube heated directly or indirectly placed in a cross flow, heat flows circumferentially by conduction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube. The circumferential heat flow affects the wall temperature distribution to such an extent that in some cases. The effects of circumferential wall heat conduction on local convective heat transfer is investigated. The wall heat conduction parameter which can be deduced from the governing energy equation should be used to express the effect of circumferential heat conduction. Two-dimensional temperature distribution is presented through the numerical analysis. The comparison of one-dimensional and two-dimensional solutions is demonstrated on graph of local Nusselt numbers.
Verification Experiment and Analysis for 6 kW Solar Water Heating System(Part 2 : Modelling and Simulation)
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 556~565
We have experimented an actual solar water heating system acquiring real data for one year period. On the basis of the operation data, it is necessary to predict the system performance such as collector efficiency and solar fraction, and to analyze the economical efficiency for system optimal design. To estimate the performance of actual systems through simulation, valid modelling for components consisting of the system should be accompanied. The present study is focused on the modelling for load patterns and operating control conditions. We proposed two load models: concentration model which gathers real loads as a meaningful group and distribution model which disperses real loads with time. If grouping of the load distribution is suitable, the predicted values by the concentration model approaches to those by the distribution model close to actual load pattern apparently. As a result, both of them are in good agreement with those by experiment.
Cycle Simulation of a Desiccant Cooling System with a Regenerative Evaporative Cooler
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 566~573
Comparison of the cooling performance is provided between the desiccant cool-ing systems incorporating a direct evaporative cooler and a regenerative evaporative cooler, respectively. Cycle simulation is conducted, and the cooling capacity and COP are evaluated at various temperature and humidity conditions. The COP of the system with a regenerative evaporative cooler and the regeneration temperature of 6
is evaluated 0.65 at the outdoor air condition of 35
and 40% RH. This value is found about 3.4 times larger than that of the system with a direct evaporative cooler. Furthermore, incorporating a regenerative evaporative cooler eliminates the need for deep dehumidification in a desiccant dehumidifier that is necessary to achieve low air temperature in the system with a direct evaporative cooler. Subsequently, the regenerative evaporative cooler enables the use of low temperature heat source to regenerate the dehumidifier permitting the desiccant cooling system more beneficial compared with other thermal driven air conditioners.
A Study on the Operation Strategy of Radiant Floor Cooling in Apartment Buildings
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 574~583
In this study, the operation strategy of the radiant floor cooling is evaluated in terms of indoor environmental conditions and energy consumption through simulations using the TRNSYS comparing the existing cooling operation. The operation strategy during continuously operated for cooling is proposed that a representative room had additional equipments and other rooms were operated with only a radiant floor cooling system and that system and control method for cooling are varied with period while intermittently operated for cooling. Specifically, when there are no people in the room, rooms were operated by only radiant floor cooling system using cooling storage and when people are occupied, rooms were operated by dehumidification and supplementary cooling device with radiant floor cooling system. The results of this study show that proposed operation strategy can stably maintain the set room air temperature and can reduce the energy consumption compared to the existing cooling method during continuously operated for cooling. While intermittently operated for cooling, the difference of set room air temperature by proposed operation strategy does not happen, satisfying comfort standards and the radiant floor cooling can expect to supply stable electric power because of decreasing demand for peak electric power of energy consumption.
Forced Convection Correlation for Single Circular Fin-tube Heat Exchanger
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 584~588
This work was performed to investigate the heat transfer characteristics of the circular fin-tube heat exchanger. This paper contains the experimental data for the seven kinds of fin geometries. The correlation of Stasiulevicius agreed with the experimental data at high Reynolds number, however not well at low Reynolds number. The Nusselt number was well correlated with Graetz number, and showed a transition near Gz=10. An empirical correlation proposed in the present work agreed well with the experimental data.
A Comparison of Flow Condensation HTCs of R22 Alternatives in the Multi-Channel Tube
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 589~598
Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/
s and heat flux of 7.3∼7.7 ㎾/
at the saturation temperature of 4
. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.
The Experimental Study on a Effect of Korean Paper (Hanji) on Indoor Humidity Control
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 599~607
The purpose of this study is to reevaluate the performance of Hanji as an architectural material. Hanji has good things in controlling indoor space comfortably. Particularly, ability of controlling humidity of Hanji affects indoor space comfort and human health. The major focuses of this experimental research are (1) how much of water vapor passes through Hanji, (2) how much of water vapor is absorbed into Hanji. In the first case, indoor humidity is higher than outdoor humidity. In this case, approximately 38 g of water vapor passes through Hanji 1, genarally utilized in window paper (Changhoji), per square meter in one hour. And approximately 4 g of water vapor is absorbed into Hanji 2, genarally utilized in wallpaper, per square meter. In the second case, outdoor humidity is higher than indoor humidity. In this case, Hanji passes water vapor to inner space at first, but when indoor relative humidity reach approximately 66%, although outdoor humidity is higher than indoor humidity, water vapor doesn't pass through Hanji. If Hanji is utilized in window material and wallpaper, indoor space is maintained comfortably without mechanical devices in humidity control.
Artificial Lighting Energy Saving by Daylighting in Office Building
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 16, issue 6, 2004, Pages 608~613
Artificial lighting accounts for a significant portion of the energy use in office buildings. Therefore, daylighting is considered one of the fundamental design features of energy-efficient buildings. However, complex daylighting simulation tools are not suitable for most designers to help in the decision-making process. This paper provides the results of a simulation analysis to determine the potential energy savings of daylighting effects reducing electrical energy consumption for office building. A whole building simulation tool is used to determine the effects of daylighting on lighting electricity use as well as total electricity use for typical office buildings. It was determined that daylighting does not provide significant additional lighting energy savings when glass transmittance is increased over 0.7 A simplified method is developed based on the analysis results to estimate the annual electrical energy savings attributed to daylighting.