• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.5
• /
• pp.359-364
• /
• 2002

A popular type of residential air conditioner is the split system which has two separate units: indoor and outdoor units During field installation of the split system, the potential exists for not setting the charge exactly to the manufacturer´s specifications. The objective of this study is to investigate the effects of the refrigerant charge on the performance of the air conditioner. An air conditioner with capillary tube expansions was tested for various refrigerant charges. The results indicated that the more charge resulted in the more flowrate of the refrigerant. The flowrate of the refrigerant was one of the most important factors to understand the e(sects of the charge on the performance of the air conditioner with capillary tube expansions. Under-charge results in wide region of superheated vapor of the refrigerant in the evaporator, while over-charge results in high temperature of the liquid refrigerant in the evaporator.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.10
• /
• pp.1489-1497
• /
• 2003

Aerosol charge neutralizers with various radioactive sources have been used to apply an equilibrium charge distribution to aerosols of unknown charge distribution. However, the performance of aerosol charge neutralizers is not well known, especially for highly charged particles. Measurements of highly charged particles are needed in air cleaning devices, e.g. electrostatic precipitator, bag filter with a pre-charger, and electrical cyclone. In this study, the particle charging characteristics of two different aerosol charge neutralizers were experimentally investigated for singly charged monodisperse particles and highly charged polydisperse particles. One has radioactive source of $^{85}$ Kr (beta source, 2 mCi) and the other has $^{210}$ Po (alpha source, 0,5 mCi). The air flow rate passing through each aerosol charge neutralizer was changed from 0.2 to 2.5 L/min. The results show that the charge distribution of singly charged monodisperse particles passing through the $^{85}$ Kr aerosol charge neutralizer is well agreed with the Boltzmann equilibrium charge distribution at an air flow rate of 0.3 L/min, However, it deviates from the equilibrium charge distribution when the air flow rates are 0.6, 1,0, and 1,5 L/min, On the other hands, the effect of air flow rate is insignificant for the $^{210}$ Po aerosol charge neutralizer. The non-equilibrium character in charge distribution of highly charged polydisperse particles passing through the $^{85}$ Kr aerosol charge neutralizer greatly depends on the air flow rate, however it is insensitive to the air flow rate for the $^{210}$ Po aerosol charge neutralizer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.5
• /
• pp.486-493
• /
• 2000

A theoretical model for the transient performance of vapor-compression air-conditioning system has been developed to evaluate the influence of the refrigerant charge on the system performance. A set of mass and energy equations for the simulation of the heat exchangers and the capillary tube and a polytropic compression model for the compressor are used. The present model successfully predicts the transient behavior of the vapor-compression air-conditioner from the startup. As the refrigerant charge is increased, both the evaporating and condensing pressures increase gradually, and the cooling rate and the COP show a maximum in the range of 0.75-0.8 kg of refrigerant charge. This amount of refrigerant mass is determined to be the optimum charge of the model system. Also, the effect of outdoor air temperature on the optimum refrigerant charge is discussed.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.26 no.3
• /
• pp.9-22
• /
• 2018

Korea meteorological administration(KMA) has started to levy air meteorological service charge on both national and foreign carriers since 2005. The charge has grown on 2010 and 2014 twice. However, KMA has still kept asking airlines to agree with another increase in the charge due to the low cost of goods recovery ratio of 7%. The air meteorological charge has changed from 2,210 KRW at the beginning to 11,400 KRW as of June 2018. According to ARIMA intervention time series analysis, it was proven national carriers would make a payment of 831 million KRW 2018 and 1,024 million KRW 2019, showing 186.2% and 123.2% increase compared to last year respectively. The total amount of charge for both national LCC and foreign airlines was aggregated up to 1,952 million KRW 2019, 227% bigger than the charge paid at 2017. Considering the 50% increase of consumer price index last decade, the increased charge would impair the global competitiveness of national carriers. It could be suggested that current air meteorological charge scheme be improved to apply overseas trend and for national carriers to have a competitive advantage in global aviation market.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.11a
• /
• pp.15-16
• /
• 2005

In this study, the characteristics of NOx reduction by using charge air moisturizer system were evaluated by engine performance simulation in medium speed diesel engines. The results of performance simulation were verified by experimental results of single cylinder medium speed diesel engine equipped with charge air moisturizer system. Performance simulation was carried out to evaluate charge air moisturizer system of turbocharged diesel engine, HYUNDAI HiMSEN 9H25/33 engine. Those results show 50% NOx reduction at dew point $80^{\circ}C$ and charge air pressure 4bar.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.10
• /
• pp.710-718
• /
• 2010

A numerical study was performed to predict refrigerant charge amount in a mini-channel condenser for a R410A residential air-conditioning system. Multi-channel flat tubes with 12 mini-channels of 1.17 mm average hydraulic diameter for each tube were applied to the condenser. The condenser consisted of 3 passes, and the first, second, and third pass had 44, 19, and 11 tubes, respectively. Each pass was connected by a vertical header. In this study, the condenser was divided into 410 finite volumes, and analyzed by an $\varepsilon$-NTU method. With thermophysical properties and void fraction models for each volume element, the R410A amount distribution and a total charge amount in the condenser were calculated. The predicted total charge amount was compared with the experimentally measured charge amount under a standard ARI A condition. The developed model could predict the charge amount in the mini-channel condenser within prediction errors from -23.9% to -3.0%. Air velocity distribution at the condenser face was considered as non-uniform and uniform by the simulation model, and its results showed that the air velocity distribution could significantly influence the charge amount and vapor phase distribution in the condenser.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.8
• /
• pp.617-625
• /
• 2002

In this study, effects of refrigerant and oil charges on the performance of a refrigeration system simulating an automobile air conditioner have been experimentally investigated using R134a and PAG oil. Measurements were taken in a breadboard type refrigeration test unit with a compressor used for a commercial automobile air-conditioner under a set of condition imposed upon normally to automobile air conditioners. Both the COP and capacity decreased rapidly as the oil charge increased because of the decrease in vapor pressure of the circulating refrigerant/oil mixture. The excess oil left in the evaporator also caused heat transfer degradation resulting in a decrease in capacity and in turn COP. It was found that there is an optimum refrigerant charge at which the COP becomes the maximum. Below this optimum charge, both the capacity and COP increased as the refrigerant charge increased and above the optimum charge, both of them remained almost constant. Hence, the COP seems to be the most important factor in determining the optimum refrigerant charge. When the system was undercharged, the refrigerant at the condenser exit lost subcooling and showed a sign of poor miscibility.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.10
• /
• pp.703-709
• /
• 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.

• Journal of Korean Society for Atmospheric Environment
• /
• v.28 no.6
• /
• pp.644-655
• /
• 2012

As soon as a new air filter is applied to an air purification process, the filter gets loaded with dust particles. Thus, the study on the particle loading characteristics of air filter is very essential in order to understand the real filtration phenomena during filter use. In this study, we investigated the effect of particle and filter charge on the particle loading property of air filter. Charged filter and uncharged filter prepared by discharging the charged filter by isopropyl alcohol were used as test samples, and three types of particle having different charge states were supplied to filters tested. For neutralized particles there was a big difference in areal mass loading rates between charged and uncharged filters due to the very small amount of particle charge, on the other hand the difference was diminished for atomized particle and finally almost vanished for corona charged particles. The pressure drop of filter loaded with corona charged particles was only half of those for neutralized and atomized particles at the same areal mass loading because of the porous structure of particle deposit formed on filter fibers, caused by the space charge effect between particles.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.2
• /
• pp.1-8
• /
• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.