• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.421-427
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• 2016

The indoor temperature of a building increases during the day due to solar radiation. This behavior is significant in school buildings that are finished with high thermal capacity materials. Moreover, in school buildings, windows cannot be opened until the class has finished owing to the security policy of schools. Consequently, classrooms maintain a high temperature throughout the morning. It is thus important to remove the indoor heat before the commencement of classes in order to reduce the cooling energy needed. The Energy Recovery Ventilator (ERV) system is currently being installed in school buildings for ventilating the classrooms. Night-purge control using ERV can be a good strategy to cool the classroom in advance of the operation of the cooling system. However, the optimal operation method of the ERV for night-purge control has not yet been reported. In this study, the effect of night-purge control with ERV in school buildings is analyzed by simulation method. The results of this study showed that the energy saving effect of night-purge control with ERV is most effective in the case of 2 hours operation prior to the commencement of the first lass and when enthalpy based outdoor air cooling is used.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.129-136
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• 2006

Optimal design of an air-to-liquid finned plate heat exchanger is considered theoretically in this study. Based on existing correlations for the pressure loss and the heat transfer in channel flows, the optimal configuration of the plate heat exchanger including the optimal plate pitch and the optimal fin pitch is obtained to maximize the heat transfer within the limit of the pressure drop for a given flow depth of the plate heat exchanger. It is found that the optimal fin pitch is about one ninth of the optimal plate pitch. In the optimal configuration, the flow and thermal condition in the channels is just at the boundary between the laminar developing and laminar fully developed states. It is also found when reducing the flow depth of plate heat exchangers for compactness, the heat transfer performance can be maintained exactly the same if the geometric parameters such as the plate thickness, plate pitch, fin thickness, and fin pitch are reduced proportional to the square root of the flow depth as long as the flow keeps laminar within the heat exchangers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.3
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• pp.156-164
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• 2010

Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use not only the advantages of the transfer matrix method but also well established classic control theories. The approach is applied to a gas turbine combustion system, which shows the validity and effectiveness of the approach.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.973-978
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• 2009

In this study, the thermal environment characteristics of On-Off control and thermal difference proportional control method in floor radiant heating system were researched by computer simulation. For the analysis of unsteady heat transfer phenomena in household, the method of using electrical equivalent R-C circuit is applied, and radiation heat transfer between panel, ceiling and walls in household is calculated by enclosure analysis method. The parametric study on two control methods, conventional on-off control and temperature error based time control(T.E.B.T.C.) method, are performed to compare thermal heating control performances, respectively.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.523-528
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• 2008

The accurate distribution of flow rate has been a very important part to control the air change rate since introduction of house ventilation system. An inappropriate selection of fan due to incorrect prediction of pressure loss in duct brings energy loss. In the previous study the pressure loss of general spiral duct was measured and database was constructed for finding correct loss factors in fitting upper stream. The purpose of this study is to compare and investigate the error range of flow rate by applying T-Method to bilateral symmetry and asymmetry layout of duct. The results of this study are as following. It is demanded to decide accurate size under duct design for house ventilation system. Because the small amount of Flow rate was considered at that time. The error range was 3.17% on case1 and 3.52% on case2. The error range difference was 0.35%.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.87-90
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• 2005

The Intelligent Home provides convenient and comfortable living environment by performing automatic control, heating and air-conditioning, ventilation, home appliances control, home robot control, energy management, visitor management security management, internet, heath state monitoring, etc. through wired/ wireless network and device in the household. Along with the presentation of the features of economical broadband power line communication in the network configuration for new and old houses, its improvement method is proposed.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.494-501
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• 2000

Effectiveness of a 3-pass plate finned-tube heat exchanger is calculated using heat exchangelet method by changing the shape of fin and the arrangement of tubes. The alternative refrigerant R134a is taken in this study. Conduction between neighboring tubes along the fin is taken into account in addition to convection between the fin and the surrounding air. Governing equations are obtained by using energy balance in a small control volume containing a tube and fins. They are numerically solved following the tube. Effect of tube-to-tube conduction is investigated in single-phase and two-phase flows with various fin shapes and arrangements of tubes. Improvement of effectiveness by fin perforation is studied too. The results shows that perforating fins, increasing the number of tubes, and increasing the distance between neighboring tubes at the same fin area enhance the effectiveness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.153-163
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• 2011

Energy efficiency and indoor air quality have become main issue to develop healthy and sustainable building in these days. As an effort to reduce the energy consumption in multi-residential building, many attempts as like passive design strategies and renewable energy as well as active control method are tried. However, underground parking lot in multi-residential building seldom adopt the sustainable strategies and only mechanical system is installed as usual. Moreover, the mechanical system installed in underground parking lot is rarely operated due to the electric demand for operation after completion. In this study, as an energy efficient measure, natural ventilation system using stack effect as a driving force for underground parking lot will be proposed and the performance of the suggested system will be analyzed by simulation method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.9
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• pp.361-366
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• 2016

As an alternative of well-mixed storage tank with lower coil only, we have proposed a tank with lower and upper coils and verified a superior thermal stratification in a tank, which results in increased collector efficiency and solar fraction. But the phenomenon of temperature reversal was often experimentally observed in the tank, so a revised control was successfully applied which is to heat only lower coil using three way valve if temperature reversal occurs and to operate the collector with low flow rate when the condition of solar radiation is not good. In the present study, using TRNSYS we compared the existing lower heating and the proposed lower and upper heating with a control preventing temperature reversal. The results showed that the proposed method has an increase of collector efficiency by 5.1% and solar fraction by 3.2%.