• 설비공학논문집
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• 제15권7호
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• pp.586-594
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• 2003

The performance of the condenser installed in the air-conditioning plant room of a high-rise building was studied numerically. The effect of the draft direction on the performance of an air-conditioner was analyzed. The on-coil temperature of the condenser was investigated by varying the arrangement and location o( the condenser in the air-conditioning plant room. The performance of an air-conditioner was also evaluated by using COP (coefficient of performance) and CGPI (condenser group performance indicator). The condenser in an air-conditioning plant room should be arranged in such a manner that the fan of the condenser is facing the outside of the building to exhaust the hot air directly, The model by which the condenser is located at the lower-left end of an air-conditioning plant room can prevent the hot air from reentering, and allow indrafting of fresh air. When the direction of draft is to the frontal face of the building, the performance of the condenser above 30th floor is degraded.

• 설비공학논문집
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• 제11권4호
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• pp.537-541
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• 1999

The system performance of a room air conditioner using R410A was experimentally evaluated and compared with that of R22 system. The results indicated that the cooling EER(energy efficiency ratio) of R410A was 1% higher than that of R22 at the outdoor temperature of $35^{\circ}C$. As outdoor temperature increases above $35^{\circ}C$ ambient, EER of the R410A system decreased more substantially compared with R22 system. R410A showed higher compressor discharge temperature than that of R22 system at the outdoor temperature of higher than $50^{\circ}C$.

• 설비공학논문집
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• 제19권10호
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• pp.703-709
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• 2007

Much energy is used in occupying stage of the Building Life Cycle. Electric charge is one of the various factors that influence on energy use of residents. This study focused on electric charge and searched that whether electric charge affects residents' behavior of operating air conditioner and their controlled indoor climate. We surveyed three groups for field study ; A group is residents who live in a studio apartment, B group is residents who live in a university dormitory and C group is residents who live in a apartment with their family. The A and C groups are charged for electric as energy consumption they used. And the B group is students who live in a university dormitory and they are not charged for their energy consumption. We measured the time to use the air conditioner for cooling, on/off temperature of air conditioner, and room air temperature for these three groups. The result shows that consideration for electric charge affects to the residents' behavior of operating air conditioner and their acceptable thermal range.

• KIEAE Journal
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• 제7권5호
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• pp.59-64
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• 2007

Using air conditioner has been increased in home or office buildings in summer. Also various problems related to air conditioning such as disease induction happened by using air conditioner excessively and operating long. Active operation control is needed for occupant's health when air conditioner operates long. We should think ahead to acquire thermal comfort of occupants which represents psychological and physiological reaction for this operation. Research has been progressed to observe activity of autonomic nervous system by trying to quantitate change of thermal comfort. In this study, questions of the subject and change of body's autonomic nervous system were chosen to evaluate thermal comfort during operation of air conditioner for a long time. Electrocardiogram and questions of the subject which is the progress of changing TSV and CSV by occupants indoor were measured when room air conditioner is operated for a long time, and an air-conditioned adaptability of human body was evaluated by acquiring the change rate of autonomic nervous system through analyzing HRV. As a result of the evaluation, change rate of body's autonomic nervous system corresponded to votes of the subject's question generally, but was distinguished from analysis result of warm-cold sensation in a low temperature area.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.526-529
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• 2008

Air Conditioner has become a popular comfort providing device since two decades, whether in an office or home especially for warm and wet climate countries. The RAC (Room Air Conditioner) is widely used in various working spaces and residences. It composed of heat exchager, cross-flow fan, stabilizer, rearguider and blade of diffuser region, etc. In this study, numerical analyses based on the prediction of transient phenomena were carried out to investigate the flow characteristics in the RAC, including the impeller, the rearguider, the stabilizer and the blade of the diffuser region. Using a commercial code, FLUENT, the velocity, pressure and streamlines were obtained with unsteady, turbulent flow and no-slip condition. The angular velocities of impeller are located in the 900 rpm. Turbulent closure was achieved using a standard k-${\varepsilon}$ model. A moving reference frame (MRF) approach was adopted to simulate the flow field generated by impeller in the RAC. Results were graphically depicted with various geometrical configurations and operating conditions.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.853-856
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• 2009

Test models which have geometrical similarities with a real room air conditioner (RAC) have been manufactured including visualization windows so that a laser beam can pass through a cross flow fan. Then, flow distributions of the RAC have been investigated using a visualization technique such as a Particle Image Velocimetry (PIV) to analyze an efficiency and noise of the RAC. Pitot tubes have also been used to measure the flow velocity inside the RAC with various positions to confirm the measurement accuracy of the PIV technique. The measured flow velocities have been analyzed and new designs of the RAC have been proposed to improve the efficiency and to reduce the noise for the RAC in this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2713-2717
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• 2008

Whole flow fields of a room air conditioner (RAC) have been visualized by a Particle Image Velocimetry (PIV) technique to analyze the flow structure with various inlet and outlet angles, and to control an eccentric vortex which affects an efficiency and noise of the RAC. A test model with 5 stages of a cross flow fan has been manufactured and a transparent acryl has been installed at the side of the test model for the PIV experiment. The inlet and outlet flows and the flow inside the cross flow fan have been analyzed by varying the inlet grill angles and outlet blade angles. The movement of the eccentric vortex has been investigated experimentally by developing the measurement technique for the inner flow field of the cross flow fan. From the visualization of the inner flows, the origins of the noise inside the RAC and the condensation points around the outlet parts of the cold air have been observed and the solution of the problems can be proposed in this study.

• 대한기계학회논문집B
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• 제29권7호
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• pp.868-877
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• 2005

We performed the experimental and the numerical study on the comparison of thermal comfort performance indices for cooling loads in the lecture room for 4 cases: Fan coil unit(FCU) or 4-way cassette air-conditioner is respectively operated with the ventilation system or without. We measured the velocity, the temperature distribution and predicted mean vote(PMV) value in the lecture room for 4 different air-conditioning methods. Effective draft temperature(EDT) and PMV were investigated to analyze the characteristics of two thermal comfort indices in the lecture room and to compare their values each other. From the results we knew that there is the similarity between PMV values and EDTs when the room is air-conditioned for cooling loads. It turned out that definition of the control temperature is very important when the EDT is calculated. Finally EDT should not be used to predict the accurate thermal comfort in case that the temperature and humidity are suddenly varied and the zone affected by the solar and inner wall radiation.

• 설비공학논문집
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• 제17권2호
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• pp.95-100
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• 2005

Numerical simulations and experiments were conducted to analyze the design parameters for a slim room air-conditioner. These design parameters included a fan shape, a front panel, a scroll shape, a bell mouth, a distance between a fan and a heat exchanger, etc. Each design parameter was analyzed numerically and/or experimentally in terms of the flow rate and the sound pressure level, which should be the most influential factors for developing the slim room air-conditioner. The fan with a uniform height showed a better performance than that with a linearly varying height. It is recommended to use a front grill rather than a front panel according to sound pressure levels since the front panel itself is a huge resistance to the inlet flow. A redesigned scroll shape by changing the rotational direction of a fan also contributed a lot to lowering the sound pressure level. There existed a distance between a fan and a heat exchanger, where flow rates increased effectively.

• 설비공학논문집
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• 제17권8호
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• pp.736-745
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• 2005

This study is undertaken to evaluate the relationship between the indoor $CO_2$ concentration and the local mean air-age in the lecture room with the occupants. We conducted the experiments to examine the indoor $CO_2$ concentration and the local mean air-age with respect to the supply airflow of the ventilation system and the discharge angle and air-flow of the system air conditioner. Through the experiments, we found out that indoor $CO_2$ concentrations calculated by the prediction equation of Seidel are about 350 ppm lower than those measured by the experiments. The indoor $CO_2$ concentration is not related with the air-flow and the discharge angle of the system air-conditioner, but with the ventilation airflow. From the numerical calculation, the indoor $CO_2$ concentration is not related with the ventilation effectiveness, but strongly with the local mean air-age. In case of our model, the indoor $CO_2$ concentration is likely to fall within the acceptable air quality when the local mean air-age is averagely predicted under 400 seconds.