• Proceedings of the KSR Conference
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• 1999.11a
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• pp.479-486
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• 1999

The noises generated from the air-conditioning duct are known to strongly affect the indoor-noises of high speed trains. The acoustic characteristics of an air-conditioning duct should depend on the geometry and shape of the duct. The structural material for Korean high speed train is supposed to be changed from Steel, which was used for TGV, to Aluminum in order to reduce the total train weight. Accordingly, the shape and layout of the air-conditioning duct of Korean high speed train will be different from that of TGV. Thus, this paper introduces a analytical method to predict the noise attenuation through the air-conditioning duct, based on the ISO 7235. In this method, the whole duct is divided into several pieces and the noise attenuations predicted for each duct piece are integrated to get the noise attenuation for the whole duct system. The validity of the method introduced herein is discussed through some numerical tests.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.2
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• pp.106-114
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• 2001

The office environment of the building has been significantly changed and the office automation(OA) for productivity improvement and efficiency has proceeded. According to thee trends, the concept of office environment was transferred from conventional \"working space\" to \"living space\" or \"creative space\". Thus, occupants in office building have demanded more comfortable and advanced task environment. The objective of this paper is to evaluate the indoor environment of working space with personal air conditioning system using the measurements of environmental comfort parameters and the questionnaire survey of occupants、 thermal sensation response to the environment.n response to the environment.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.3
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• pp.100-106
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• 2009

As an effort to prevent environmental problems caused by ozone depletion and global warming, alternative refrigerants are being developed, and one of the candidates is carbon dioxide. To overcome slightly low efficiency of $CO_2$ refrigeration system, air-conditioning cycle using an ejector was suggested. Ejector compensates throttling loss in an expansion device by reducing compression work. In this study, the ejector refrigeration cycle using $CO_2$ as a refrigerant is investigated to understand the effect of the mixing section diameter and refrigerant charge amount on the performance. If mixing section diameter is too large or too small, either cases show low performance. The optimum refrigerant charge amount which gives the best performance is found for standard operating conditions. The air-conditioning cycle was analyzed for several operating conditions.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.1002-1009
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• 2004

Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature, water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister, heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary, the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase and as the air velocity decreases.

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

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.11
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• pp.1020-1030
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• 2000

A crossflow finned tube evaporator has been investigated using tube-by-tube method. The refrigerant flows inside tubes while the air passes outside the finned tue. R134a for a refrigerant and wet air were used in this analysis. Three refrigerant circuitries, complex or simple, were compared. The effects of refrigerant circuitry and airside condensation on thermal performance such as heat transfer rate, enthalpy of refrigerant, temperature of refrigerant and air, pressure of refrigerant and average condensate layer thickness were investigated. It was found that this method could be applied to the analysis of finned tube evaporator for dehumidification and air conditioning.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.681-686
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• 2006

In order to protect the environment from the refrigerant pollution, the $CO_2$ may be regarded as one of the most attractive alternative refrigerants for an automotive air-conditioning system. Control methods for a $CO_2$ system should be different because of $CO_2's$ unique propel-ties as a refrigerant. Especially, the high-side pressure of a $CO_2$ system should be controlled for the effective operation of the system. In this study, dynamic models of a $CO_2$ air-conditioning system were developed by using experimental data. Control algorithms for a high-side pressure control and an indoor air temperature control were developed and analysed by using the dynamic simulation program of a $CO_2$ system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.681-687
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• 2005

Experimental results for heat transfer characteristic and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The test sections which has one tube diameter of 12.70 m with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local evaporating heat transfer coefficients of hydrocarbon refrigerants were higher than that of R-22. The average evaporating heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7 mm and 9.52 mm. This results form the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air- conditioning systems.

• Environmental and Resource Economics Review
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• v.16 no.4
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• pp.901-922
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• 2007

To see how the electricity demand for air-conditioning responds to weather condition and what kind of weather condition works better in forecasting maximum daily electricity demand, four different regression models, which are linear, exponential, power and S-curve, are adopted. The regression outcome turns out that the electricity demand for air-conditioning is inclined to rely on the exponential model. Another major discovery of this study is that the electricity demand for air-conditioning responds more sensitively to the weather condition year after year along with the higher non-air-conditioning electricity demand. In addition, it has also been found that the discomfort index explains the electricity demand for air-conditioning better than the highest temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.467-474
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• 2001

The mathematical model of a air-conditioning system is generally very complex and difficult to apply to controller design. In this paper, simple models applicable to the controller design are obtained by modeling the air-conditioning system by single-input single-output between compressor speed and indoor temperature, and by multi-input single-output between compressor speed, indoor fan speed and indoor temperature. Using these empirical models, model predictive control(MPC) technique was implemented for indoor temperature control of the air-conditioning system. It has been shown from various experiments that the indoor temperature control based on the MPC scheme yields reasonably good tracking performance with smooth changes in plant inputs. this multi-input multi-output MPC approach can be extended to multi air- conditioning systems where the conventional PID control scheme is very difficult to apply.