• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.201-208
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• 2005

This study presents the experimental study on improvement of frost/defrost performance in an heat pump system with newly developed fin and multiple compressors. As multiple compressors system, the variable and single speed compressor combinations has been introduced and compared with single speed 1-compressor system in a view point of improvement of frost/defrost performance. Also, newly developed corrugate shaped fin has been compared with conventional louver shaped fin. The frost/defrost performance is defined and some parameters are compared to discuss the effect of each combination. From this experimental study, it is known that if the variable and single speed compressor combination system equipped with corrugate shaped fin, the system performance has greatly improved not only for heating capacity, but also for frost performance.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.204-204
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• 2004

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.165.2-165.2
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• 2010

The objective of this study is to analyze the energy saving rate by retrofitting multi air conditioner from conventional type to high efficient type using Energyplus 4.0 which was developed for simulating a building energy by D.O.E. Generally, Multi air conditioner system was installed for both the cooling and the heating in a building. However, it was difficult to estimate the energy saving rate in the case of retrofitting multi air conditioner from conventional type to high efficient type. In the present study, annual energy consumptions of them were evaluated for same building and climate condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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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 $50^{\circ}C$.

• Journal of Korea Multimedia Society
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• v.10 no.6
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• pp.786-798
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• 2007

As we go about our daily lives, people often collect surrounding information and adapt to the situation. Computer development trends show that one wants computers to work like human beings, i.e. computers can sense its context and adapt corresponding to context changes. To implement this expectation, a context aware service layer is needed. In this layer, sensors capture its environment and send this information to the service center. Considering received information as its context, the service center seeks the suitable operation according to the context. Tills paper presents a context aware service which is applied in controlling air-conditioner. The air-conditioner includes sensors which are installed at some special positions in a room. Each of these sensors gathers comfort-influenced information like temperature, humidity and sends them to air-conditioner. The air-conditioner adapts its operation to the environment according to the sensed information. To control the air-conditioner effectively, we use a genetic algorithm which is suitable in adaptation issues. The simulation shows that the room condition can be maintained at a comfortable level by using context-aware services in the operation of the air-conditioning system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.5
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• pp.44-51
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• 2009

In this paper, an air conditioner peak power control system using electric power line communication has been developed. The air conditioner power control system using RS-485 communication method is hard to install on the existing buildings due to difficulty in cabling, and the system using wireless communication methods has a weak point of not being able to be used in close space, while the developed system has its own advantages of overcoming the above mentioned obstacles. In addition, the system is extended to support not only single-phase electricity system but also three-phase four-wire electricity system, and therefore can be installed anywhere in the domestic environment. The system also has enhanced the ease of deployment, operational stability and economical efficiency by compact circuit design. Considering the current state requiring the energy sayings, the system would greatly contribute to the widespread use of the air conditioner power control system. The superiority in the performance and stability of the system has been proved by the design verification of each component such as remote air conditioner controller, electric power line gateway and so on, and the field test of the whole system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.6
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• pp.321-327
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• 2015

This study presents an HFC152a refrigerant air conditioner as an alternative to HFC134a, which is currently used in mobile air conditioning systems. Cool-down performance tests of an HFC152a air conditioning system were conducted and compared to a baseline HFC134a air conditioner. The experimental set-up consisted of a belt-driven compressor, a sub-cooled type condenser, an evaporator, and a block-type thermal expansion valve (TXV). A drop-in test was carried out on the mobile air conditioning system under various vehicle running speeds in a climate-controlled wind tunnel (CWT). Additionally, to optimize the HFC152a air conditioning system, the effects of the TXVs on the performance were studied. The results show that compared to the HFC134a air conditioning system, the refrigerant charge quantity was reduced by approximately 20%, the discharge pressure was reduced by about 350~430 kPa, and the air discharge temperature at vehicle running conditions was $0.5{\sim}1.5^{\circ}C$ lower. In addition, good compressor durability was expected due to the lower compression ratio.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.64-70
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• 2019

Wireless sensors have been developed in numerous ways for enhancing the convenience of installation, management and maintenance of sensors. Energy harvesting wireless sensors, which can collect energy from the external environment for permanent usage without the need of recharging and exchanging batteries, have been developed and employed used in Internet of Things and at various industrial sites. Energy harvesting wireless sensors are significantly affected by the sensor lifespan to sudden variation in the external environment. Furthermore, reduction in the sensor operating timespan can greatly affect the characteristics of the devices connected through a network. In this paper, a system performance index is proposed that can comprehensively evaluate the lifespan of a solar cell wireless sensor, determine the characteristics of devices connected to the associated network, and recommend dynamic power distribution control for improving the system performance index. Improvement in the system performance index was verified by applying the proposed dynamic power distribution control to an air conditioner network system using a solar cell wireless sensor. Obtained results corroborate that the dynamic power distribution control can extend the lifespan of the incorporated wireless sensor and reduce the air conditioner's power consumption.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.91-100
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• 2004

Energy efficiency evaluation method for a multi-type air conditioning system still has not been developed. In this study, analysis on capacity range and evaluating method of standards for air conditioners was conducted with world-wide Standards. It is not a proper approach to use the standards for residential air conditioner to multi type air conditioners. Some difficulties and problems are commented in this study with overview of the standards. Through the analytic research, an evaluating method for multi type air conditioner was suggested with Integrated Part Load Value (IPLV). The suggested concept for evaluating energy efficiency during part load condition considers building load pattern and operating hours of the system at different locations. Load was weighted in IPLV to consider not only the concept of occurrence of outdoor temperature such as bin method but also operation hours of the system. An experiment about the IPLV was conducted with variable air volume ducted type air conditioning system and multi-type system through modified code tester to give a glance at quantitative value of the IPLV.