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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
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Flow and Heat Transfer Characteristics due to Staggered Arrangement of Heat Pipes in Channels with Heat Pipes and Fins
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 871~879
The characteristics of flow and heat transfer in the heat exchanger of heat pipes with fins have been studied numerically for cooling enhancement of electronic components of KTX (Korea Train eXpress). Numerical analysis and methodology have been conformed by comparing the experimental results for inlined array of heat pipes. The staggered arrangement of heat pipes has been proposed in order to achieve heat transfer enhancement. As results, the geometry change to the staggered array is conformed to increase the heat transfer of the system accompanied by an increase of pressure drop. The current results of friction factor and Colburn j factor are presented in terms of Reynolds number and staggered distance, and are expected to use for design and manufacture of such a system.
Theoretical Analysis of Factors Affecting to Heat Transfer Limitation in Screen Mesh Wick Heat Pipe
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 880~889
The purpose of the present study is to examine the factors affecting the heat transfer limitations of screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6 mm, and mesh numbers are 50, 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, capillary limitation, entrainment limitation, sonic limitation and boiling limitation we analyzed by theoretical design method of a heat pipe. As some results, the capillary limitation in small diameter of heat pipe is largely affected by mesh number and wick layer.
Evaluation of Thermal Comfort on Temperature Differences between Outdoor and Indoor Thermal Conditions in Summer
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 890~896
Purpose of this study is to clarify the evaluation of thermal comfort based on temperature differences between outdoor and indoor thermal conditions in summer. The experiments were performed to evaluate temperature difference between indoor and outdoor thermal conditions (29, 31,
) by physiological and psychological responses of human. According to physiological responses, TSV (thermal sensation vote) and CSV (comfort sensation vote) and psychological responses, ECG (electrocardiogram), MST (mean skin temperature) of human, it was clear that the optimum temperature difference is about
Standard Weather Data of Seoul for Energy Simulation
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 897~906
Standard temperature and absolute humidity weather correlations of Seoul for dynamic energy simulation have been developed regressing the measured data compiled by the Korea Meteorological Adminstration during a 10-year period from 1991 to 2000. The mathematical equations can generate the daily and yearly variations of outdoor weather data with consistency unlike the measured data which may show abnormal behavior, Considering that each hour of the day follows a certain yearly pattern, the correlations are developed for each hour. The derived 24 simple mathematical equations can be used for estimating outdoor temperature and humidity conditions for any arbitrary time of the year.
A Study on Energy Distributions Produced by Dish Solar Concentrating System
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 907~913
An experimental study on energy density distributions produced by dish solar concentrating system was performed to optimally design and rightly position a cavity receiver. This deemed also very useful to find and correct various errors associated with a concentrator. It is observed that the actual focal length is 2.17 m with a maximum energy density of 1.89 MW/
. By evaluating the position of flux centroid, it was found that there are errors within 2 cm from the target center. As a result of the percent power within radius, approximately 90% of the incident radiation is intercepted by about 0.06 m radius. The area concentration ratio normalized to 800 W/
insolation and 90% mirror reflectivity was 347 suns. The total integrated power of 2467 W was measured under focal flux distributions, which corresponds to the intercept rate of 85.8%.
A Numerical Study on the Transmission of Thermo-Acoustic Wave Induced by Step Pulsed Heating in an Enclosure
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 914~922
Thermo-acoustic waves can be thermally generated in a compressible flow field by rapid heating and cooling, and chemical reaction near the boundary walls. This mechanism is very important in the space environment in which natural convection does not exist. Also this may be a significant factor for heat transfer when the fluids are close to the thermodynamic critical point. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air-filled confined domain with two-step pulsed heating are studied numerically. The governing equations are discretized using control volume method, and are solved using PISO algorithm and second-order upwind scheme. For the purpose of stable solution, time step was set to the order of
. Results show that temperature and pressure distributions of fluid near the boundary wall subjected to a rapid heating are increased abruptly, and the induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. Pressure waves have sharp front shape and decay with a long tail in the case of step heating, but these waves have sharp pin shape in the case of pulsed heating.
Cooling Characteristics of a Parallel Channel with Protruding Heat Sources Using Convection and Conduction Heat Transfer
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 923~930
Cooling characteristics of a parallel channel with protruding heat sources using convection and conduction heat transfer are studied numerically. A two-dimensional model has been developed for numerical prediction of transient, compressible, viscous, laminar flow, and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve the problem. The assembly consists of two channels formed by two covers and one printed circuit board which has three uniform heat source blocks. Six different cooling methods are considered to find out the most efficient cooling method in a given geometry and heat sources. The velocity and temperature fields of cooling medium, the temperature distribution along the block surface, and the maximum temperature in each block are obtained. The results are compared to examine the cooling characteristics of the different cooling methods.
Development of a Software System for Measurements of Combustion Dynamics of a Dry Low NOx Gas Turbine
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 931~938
Combustion dynamics of a dry low NOx gas turbine have been measured by utilizing a dynamic pressure measurement system. The software part of the measurement system, implemented with a commercial general-purpose DASYLab version 5.6 code, basically acquires combustion dynamics signals, performs the FFT analysis, and displays the results. The gas turbine often experiences momentary combustion instability, especially when its combustion mode changes. It is found that the measurement system developed in the study may outperform the other commercial dynamic pressure measurement system. The developed system currently serves to monitor the combustion dynamics of the gas turbine.
An Experimental Study on the Local and Overall Heat Transfer Characteristics of a Fin-Flat Tube Heat Exchanger
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 939~947
Local and overall heat transfer characteristics of fin-flat tube heat exchangers with and without vortex generators are investigated. Local heat transfer coefficients are measured with the heat exchanger model using naphthalene sublimation technique. In case of a fin-flat tube heat exchanger without vortex generators, only the horseshoe vortices formed around tubes augment the heat transfer. On the other hand, longitudinal vortices created artificially by vortex generators enhance heat transfer dramatically in case of a fin-flat tube heat exchanger with vortex generators. Overall heat transfer coefficients are measured with the prototype of the fin-flat tube heat exchanger with and without vortex generators in a wind tunnel and results are compared with those of a fin-circular tube heat exchanger with wavy fin. Friction losses for heat exchangers are also measured and compared. The fin-flat tube heat exchanger with vortex generators is found to be more effective than the fin-circular tube heat exchanger with wavy fin.
EEV Superheat Control of a Multi-type Heat Pump by Using Dither Signal
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 948~953
The electronic expansion valve (EEV) may be used to control the refrigerant flow rate for the multi-type heat pump. Stepping motor driven EEV may precisely control the refrigerant flow rate to meet each internal load requirement. To control the EEV, PI algorithm may be used. But the hysteresis of EEV deteriorates the performance of superheat control. To reduce the performance degradation, the PI algorithm along with the dither signal may be used. The dither signal, with about 10 times higher frequency than the system crossover frequency and about 10 times larger magnitude than the deadband of hysteresis, was selected for the superheat control of EEV. Experimental results showed the improvement of EEV control by adding the dither signal to the PI algorithm.
An Experimental Study on Performance and Flow Characteristics of Automotive Sirocco Fan
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 954~963
For the optimal design of an automotive blower system, effects of the scroll cut-off starting angle, the clearance between blade tip and bellmouth, and the scroll expansion angle on the performance of sirocco fan are investigated experimentally. Best performance is achieved at fan exposure ratio $\Deltae/r_c$,/TEX> =1.0, and clearance ratio $\DeltaeC/C=0.62. Flow characteristics inside sirocco fan are also studied by using LDV. Flow patterns in the inside of fan can be classified into three regions. Velocity vector has the same direction as rotational direction of fan at 0~
, toward the fan blades at 150～
, and opposite direction at 210~
. Turbulent intensity is relatively high near the cut-off edge in the scroll housing.
Effect of Capsule Shape on Heat Storage
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 964~971
A numerical investigation of the constrained melting of phase change materials within spherical-like capsule is presented. A single-domain enthalpy formulation is used for simulation of the phase change phenomenon. The solution methodology is verified with the melting process inside an isothermal spherical capsule. Especially, the effect of capsule shape on the heat storage is emphasized. Two shape parameters are considered from the real capsule shape showing good characteristics of heat storage and the effect of these parameters is examined. Early during the melting process, the conduction mode of heat transfer is dominant. Thus the capsule shape with large surface area is desirable. However, the capsule shape with large surface area plays negative role on the strength of buoyancy-driven convection that becomes more important as melting continues.
Effects of Various Factors on the Energy Consumption of Korean-Style Apartment Houses
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 972~980
This work is aimed at estimating the effects of various factors on the energy consumption of Korean-style apartment houses using TRNSYS. The factors considered here include the nominal size of floor area, type of remodeling, azimuth, sidewall insulation, and window type. Based on some assumptions, an actual apartment house is simplified into a model that is used for thermal load calculations. The simplified model is validated by showing a good agreement with the actual one in the predicted result. Remodeling balconies into unconditioned buffer spaces yields a favorable thermal performance in comparison with the original type regardless of the nominal size. Incorporating balconies into a conditioned indoor space leads to sharp increases in thermal loads, which must be avoided in view of energy conservation as well as structural problem. A quantitative assessment on the azimuthal effect indicates that the heating energy can be saved up to 16％ by taking the south or southeast direction. Reduction in the heating load with enhancing the sidewall insulation is gradual, so that a cost-effectiveness analysis may be needed when amending the regulations concerned. Glazing appears to significantly affect the heat transfer through window. A typical case illustrates that the heating load is decreased about 25％ by simply adopting triple glazing instead of double glazing.
Life Cycle Costing through Operating Number Control of Air Conditioning Systems in Office Buildings
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 14, issue 11, 2002, Pages 981~988
Generally, the term "energy saving is economical" is appropriate for the national view point and for design and assessment of one system, but not appropriate when choosing the system by comparing alternative systems in the early design step. Sometimes, non-energy saving system is more economical than energy saving system because of the price of electricity, gas or oil, which are used for operating the air conditioning system. Therefore, when designing the system, we should consider the efficient alternatives through economic assessment of energy saving method. However, research on non-operating number control of the system is not sufficient because it is more common to use operating number control of the system for most economic assessment of air conditioning system. For this reason, this research can provide the economics through operating number control as basic design data. The data obtained through assesment of Life Cycle Cost based on amount of yearly energy use, were produced by system simulation of HASP/ACLD/8501 and HASP/ACSS/8502 for six alternative heating/cooling systems based on constant air volume conditioning system, which is widely used for medium and large office buildings in Busan.