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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 15, Issue 12 - Dec 2003
Volume 15, Issue 11 - Nov 2003
Volume 15, Issue 10 - Oct 2003
Volume 15, Issue 9 - Sep 2003
Volume 15, Issue 8 - Aug 2003
Volume 15, Issue 7 - Jul 2003
Volume 15, Issue 6 - Jun 2003
Volume 15, Issue 5 - May 2003
Volume 15, Issue 4 - Apr 2003
Volume 15, Issue 3 - Mar 2003
Volume 15, Issue 2 - Feb 2003
Volume 15, Issue 1 - Jan 2003
Selecting the target year
A Numerical Study on the Design of a Grease Filter for Kitchen Ventilation
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 619~629
A grease filter is used to remove grease generated from a cooking appliance in a kitchen. Since the inertial impaction is a dominant particle removal mechanism of the grease filter, the performance of the filter is greatly affected by the geometry. This numerical study has been conducted to investigate the effect of geometry on the performance of grease filters for four models having nominal flowrate of 100 m
/h. Four models were designed by changing the shape of impaction surface, the length of eyelid, and the number of eyelids of the grease filter. The flow field and particle trajectories in the grease filter with a flow chamber were simulated using the commercial code of STAR-CD. The difference of air velocity and pressure distributions among four models was discussed in detail. The collection efficiency curves and the pressure drops of four models were also compared. It was found that the grease filter model with flat top surfaces shows highest performance among four models, having high particle collection efficiency and relatively low pressure drop. The cutoff diameter of this model representing 50-% collection efficiency is about 7.1
for water droplets at 100 m
The Jet-fan Model Test for a Road Tunnel Ventilation
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 630~640
As tunnel ventilation has recently been playing a major role in the tunnel construction and maintenance, longitudinal ventilation systems with jet fans have been utilized a great deal because they are economical and effective. However, due to the length of tunnels and heavy traffic, it is hard to take the field measurements. In this study, therefore, the computer simulation and the model experiment of producing a wind tunnel were carried out simultaneously and the results were compared. The ultimate objective of this research was to interpret the air flow pattern inside the tunnel with a jet-fan was set up, and to offer the useful data for jet-fan installation and operation. The experiment was carried out with varying the jet-fan diameters, location of installation, the discharge velocity. Result showed that as the initial static pressure came up with the negative pressure, the tunnel air flowed into the inside of tunnel from outside due to the entrainment-effect and the backflow-phenomenon by separation-effect was observed in the lower half part of the tunnel. As the jet-fan was getting closer to the tunnel wall, the entrainment-effect caused by the interaction with the wall was increased; however, the mixing distance and irregular flow section became longer, and also the air pressure loss generated by wall friction was large.
Verification Experiment and Calculation of Cooling Load for a Test Space
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 641~651
In order to assess the reliability of a building energy simulation program (TRNSYS) from the standpoint of user, a set of verification experiment and calculation of cooling load for a test space is carried out. This work is a complement of the previous study that dealt with heating load for the same space. The test space is kept airtight to eliminate the source of uncertainties in modeling. A window-mounted, on/off controlled air-conditioner is used for cooling, whose performance has been established a priori. The calculation encompasses two models for evaluating cooling load in TRNSYS: energy rate control and temperature level control. Comparison of the total cooling loads obtained from different sets of experimental data enables to validate the measurements. The experimental result shows that the latent load is fairly large even in the absence of apparent air change in the space, which needs to be clarified. Each of hourly and daily accumulated sensible loads is compared between the experiment and two calculation models. Despite an inconsistency associated with solar irradiation, both of the models agree favorably with the experiment within a tolerance, illustrating their capability of properly predicting space thermal loads.
Accuracy Improvement for Measurement of Heat of Fusion by T-history Method
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 652~660
T-history method, measuring heat-of-fusion of phase change material (PCM) in sealed tubes, has the advantages of a simple experimental device and no requirements in sampling process. However, a degree of supercooling used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion in the original method, which has been improved in order to predict better results by us. In the present study, the modified method was applied to a variety of PCM such as paraffin and lauric acid having very small or no supercooling with a satisfactory precision. Also the selection of inflection point and temperature measurement position was fumed out not to affect the accuracy of heat-of-fusion significantly. As a result, the method can provide an appropriate means to assess a new developed PCM by cycle test even if a very accurate value cannot be obtained.
The Performance of a Heat Pump with a Variation of Expansion Valve at Various Charging Conditions
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 661~666
Constant area expansion devices such as capillary tubes, short tube orifices are being gradually replaced with electronic expansion valves (EEVs) because of increasing focus on comfort and energy conservation. In this study, the performance of a water-to-water heat pump as a function of refrigerant charge is investigated in steady state, cooling mode operation with expansion devices of a capillary tube and an EEV. The performance of the capillary tube system varies drastically according to the change of refrigerant charge amount and inlet temperature of the secondary fluid in the condenser. Cooling capacity and COP of the EEV system show little dependence on the refrigerant charge, while those are strongly dependent on the secondary fluid temperature at the condenser inlet. In general, for a wide range of operating conditions the EEV system shows much higher performance as compared with the capillary tube system. The performance of the EEV system can be optimized by adjusting EEV opening to maintain a constant superheat at all test conditions.
Analysis on the Cooling Characteristics of a Channel with Pin-Fin Structure
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 667~673
Recent trends in the electronic equipment indicate that the power consumption and heat generation in a chip increase as the components are miniaturized and the computing speed becomes faster. Suitable heat dissipation is required to ensure the guaranteed performance and reliable operation of the electronic devices. The aim of the present study is to investigate the forced-convective thermal-hydraulic characteristics of a pin-fin heat exchanger as a candidate for cooling system of the electronic devices. The influence of the structure of the pin-fin assembly on heat transfer is investigated by porous medium model. The results are compared with the experimental data or correlations of several researchers for the heat transfer coefficients for the channel flow with pin-fin arrays. Finally, the effects of design parameters such as the pin-fin diameter and the spacing are examined.
A Comparative Experiment on the Hydrate Structures I and II for the Solid Transportation of Natural Gas
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 674~682
Natural gas hydrate typically contains 85 wt.% water and 15 wt.% natural gas, and commonly belongs to cubic structure I and II. Also, 1m
hydrate of natural gas can be decomposed to 200 m
natural gas at standard condition. If this characteristic of hydrate is reversely utilized, natural gas is fixed into water and produced to hydrate. Therefore the hydrate is great as a means to transport and store natural gas. So, the tests were performed on the formation of natural gas hydrate is governed by the pressure, temperature, gas composition etc. The results show that the equilibrium pressure of structure II is approximately 65% lower and the solubility is about 3 times higher than structure I. Also if the subcoolings of structure I and structure II are more than 9 K and 11 K respectively, the hydrates are rapidly formed.
A Study of Thermal, Air-flow and Humidity Conditions in an Indoor Swimming Pool
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 683~689
The thermal comfort of an indoor swimming pool is different from that of general indoor space because of the characteristics of large space and the wear conditions of swimmers. Dew condensation by humid air not only makes mold on the floor, wall and roof but also decreases the durability of buildings by penetrating into their structures. In this study, the characteristics of the flow field, the temperature field and the humidity distribution in an indoor swimming pool have been examined by the numerical method to estimate the level of thermal comfort and the generation rate of dew condensation. The results showed that the dew condensation regions were spread widely at the eastern parts of the swimming pool due to the insufficient air flow rate with low velocity and temperature. To prevent the generation of dew condensation in a region, a sufficient warm air flow rate should be supplied to make an air mixing. The values of PMV at horizontal plane of 1.5 m height have the range of -1.0∼1.2, which means the suitable level for swimmers.
A Study on the Heat Recovery Performance of Water Fludized-Bed Heat Exchanger
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 690~696
This paper presents the heat recovery performance of water fluidized-bed heat exchanger. Temperature and humidity ratio of waste gas are considered as important parameters in this study. Therefore, the heat recovery rate through water fluidized-bed heat exchanger for exhaust gases with various temperatures and humidity ratios can be estimated from the results of this study. Mass flow ratio (the ratio of mass flow rate of water to that of gas) and temperature of inlet water are also considered as important operating variables. Increase of heat recovery rate can be obtained through either high mass flow ratio or low temperature of inlet water with resultant low recovered temperature. The heat recovery performance with the mass flow ratio of about up to 10 has been investigated. The effect of number of stages of water fluidized-bed on the heat recovery performance has been also examined in this study.
Performance Characteristics of a 10 kW Gas Engine for Generation Package
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 697~703
Cogeneration is the simultaneous generation of heat and electricity in a single unit, and is a highly energy-efficient technology compared to the independent generation of both products. Therefore, cogeneration has been widely introduced in many countries for use in industrial, commercial and residential applications. However, there have been few models with an output of less than 100 kilowatt. In the present study, a spark ignited gas engine with electric generation output of 10 kilowatts was developed for micro cogeneration package. The gas engine shows 26.7% of electric generation efficiency, NOx emission less than 10 ppm at 13% oxygen, 82 dB of Noise level, and about 3 seconds of switching time from idling to nominal power.
Comparative Study on the Performance of Correlations of the Enthalpy of Vaporization for Pure Substance Refrigerants
Korean Journal of Air-Conditioning and Refrigeration Engineering, volume 15, issue 8, 2003, Pages 704~709
A few commonly used correlation equations of the enthalpy of vaporization are reviewed and a new three-parameter correlation equation is proposed. Performance of the proposed equation is examined using the data listed in the ASHRAE table for 22 pure substance refrigerants. The new equation yields an average absolute deviation of 0.14% for 22 refrigerants, which is better than those of other equations, such as Xiang (0.18%), Major-Svoboda-Pick (0.18%), and Somayajulu equation (0.23%).