• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.5
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• pp.313-320
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• 2001

In the present study, various experiments were performed to investigate capacity modulation and refrigerant flow distribution of a multi-heat pump using a variable speed compressor and electronic expansion valves(EEVs) in the cooling mode. Based on the experimental results, it was possible to understand the interrelation of dual indoor units which provides some difficulties in capacity control of each indoor unit. The characteristics of capacity modulation of two indoor units were measured by controlling two EEVs with a cooling load of each indoor unit.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.1-13
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• 1997

This paper reports the dynamic analysis of energy consumption for an office building by heat resistance-capacitance method. If a building is divided into several wall components and the wall components is replaced by one thermal capacitance and several thermal resistances, the building becomes an electric circuit. By solving the simultaneous equations of the circuit, the dynamic heat transfer characteristics and the energy consumption rate of the building were predicted. Accuracy of modified BIN method was evaluated by the present resistance-capacitance method. The result shows that modified BIN method overpredicts the heating load of the office building 15%. Annual energy consumptions of equipments(fan, boiler, chiller) for various ventilating control system(CAV, VAV, FCU+VAV, FCU+CAV) were compared. FCU+CAV shows the minimum annual energy consumption.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.4
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• pp.178-187
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• 2003

In this study, ventilation flow rate and pressure rise through a tunnel are simulated numerically using computational fluid dynamics (CFD) for various conditions such as roughness height of the surface of tunnel, swirl angle and hub/tip ratio of jet fan, and entrance and exit effects. By using a modified wall function, friction factor can be predicted with respect to the Moody chart within 10% of error for the circular pipe flow and 15% for the present tunnel. For more accurate design, the effect of the swirl angle and hub/tip ratio of jet fan, which is not included in the theoretical equation of pressure rise by jet fan needs to be considered.

• 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.4 no.4
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• pp.306-315
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• 1992

This paper addresses performance analysis of a reciprocating compressor. A computer simulation model has been developed to predict and estimate the compressor performance. Instead of using ideal gas equations, real gas equations are used in describing the state of gas. The compressor simulation model consists of a cylinder control volume, suction system and discharge system. Conservation laws of mass and energy are applied to the cylinder section only, The suction and discharge system are described by the Helmholtz resonator modeling. Some of input data required for the simulation have been obtained from experiments. These experimentally obtained input data are effective flow area, effective force area and dynamic characteristics of valves. Simulation results of real gas equations have been compared with those of ideal gas equations. It has been found that the simulation with real gas equations yields lower cylinder temperature and heat transfer compared with those of ideal gas equations. Differences in pressure, mass flowrates, valve motions and gas pulsations are found quite small.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.60-68
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• 2000

An experimental study was peformed to investigate characteristics of an inverter driven heat pump system with a variation of compressor frequency and expansion device. The compressor frequency varied from 30Hz to 75Hz, and the performance of the system ap-plying three different expansion devices such as capillary tube, thermostatic expansion valve(TXV), and electronic expansion valve (EEV) was measured. The load conditions were altered by varying the temperatures of the secondary fluid entering condenser and evaporator with a constant flow rate. When the test condition was deviated from the standard value(rated value), TXV and EEV showed better performance than capillary tube due to optimal control of mass flow rate and superheat. In the present study, it was observed that the variable area expansion device had better performance than constant area expansion device in the inverter heat pump system due to active control of flow area with a change of com-pressor frequency and load conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.1
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• pp.14-23
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• 2015

Although research and technology developments have recently increased to save lighting energy within buildings, such research and technology development are judged to be unsuitable for energy savings since they are limited in the sense that the application of the technology is fragmented. This study proposes a user and location awareness technology applied to dimming lighting control system and verified the effectiveness of energy savings by building a test bed. The results were as follows : 1) This study suggested a user and location awareness technology applied to dimming lighting control system. 2) The system shows 96.6% and 82.8% energy saving rates, respectively, on the basis of one user, compared to an on/off lighting control and the user and location awareness technology applied to on/off lighting control system. 3) The energy consumption of the user and location awareness technology applied to on/off lighting control system and the user and location awareness technology applied to dimming lighting control system increased to 96.6%, 88.3%, and 59.6% and 82.8%, 85.0%, 51.5%, respectively, on the basis of one, two, and three users, compared to the on/off lighting control system. This study confirmed the energy saving performance of the user and location awareness technology applied to the dimming lighting control system through performance evaluation. In this regard, further study needs to be undertaken to evaluate the performance at night time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.714-720
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• 1998

The differential pressure venturi-cone flowmeter is an advanced flowmeter which has many advantages such as wide range of measurement, high accuracy, excellent flow turn-down ratio, low headless, short installation pipe length requirement, and etc. Like other differential pressure flowmeters, the venturi-cone flowmeter uses the law of energy conservation, but its shape and position make it perform better than others. The cone acts as its own flow conditioner and mixer, fully conditioning and mixing the flow prior to measurement. For the analysis, we used Reynolds-averaged Wavier-Stokes equations and k-$\omega$ turbulence model. The equations were fully transformed into the computational domain, the pressure-velocity coupling was made through SIMPLER algorithm, and the equations were discretized using finite analytic solutions of the liberalized equations(Finite Analytic Method). To control the separation phenomenon on the cone surface, we proposed a new shape of cone, and analyzed the flowfield in the new flowmeter system, and found the improvement on the performance of the new cone flowmeter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.527-536
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• 2015

Studies for the reduction of lighting energy have been done using technologies such as user and location awareness. However, the focus of current research on location-based lighting control has been on energy reduction, which can lead to other issues including an imbalance in indoor illumination. This study proposes a lighting control system applying general illumination and technology for user and location awareness. The proposed lighting control system reduced lighting energy by 72.1%, 66.5% and 62.3% for 1, 2 and 3 users, respectively, compared to the On/Off lighting control system. This lighting control system causes an increase in lighting energy of 35.8% and 10.9% for 1 and 2 users compared to the lighting control system with user and location awareness, while a reduction of 9.4% was seen for 3 users. This means that the proposed system provides more effective energy reduction for a room with multiple occupants as it is based on the general lighting control scheme. The lighting control system applying general illumination and technology of user and location awareness improved the uniformity factor by 32.0%, 39.4% and 33.4% for 1, 2 and 3 users, respectively.

• Journal of Power System Engineering
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• v.17 no.5
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• pp.86-93
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• 2013

This paper proposes the used of genetic algorithm for optimizing PI controller and describes the dynamic modeling simulation for the permanent magnet synchronous motor driven by simplified vector control with the aid of MATLAB-Simulink environment. Furthermore, three kinds of error criterion minimization, integral absolute error, integral square error, and integral time absolute error, are used as objective function in the genetic algorithm. The modeling procedures and simulation results are described and presented in this paper. Computer simulation results indicate that the genetic algorithm was able to optimize the PI controller and gives good control performance of the system. Moreover, simplified vector control on permanent magnet synchronous motor does not need to regulate the direct axis component current. This makes simplified vector control of the permanent magnet synchronous motor very useful for some special applications that need simple control structure and low cost performance.