• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.32-32
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• 2006

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.15-21
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• 2008

Air-cooled split-type air conditioners (AC) are very popular in high-rise residential and commercial buildings in Korea. The performance of such AC systems varies significantly with system characteristics and environmental conditions. Particularly, the outdoor condensing unit of the system, if poorly cooled due to high density of AC distribution and restricted outdoor space, will result in large decrease of cooling efficiency and increase of electrical energy consumption and may further jeopardize the system reliability. This paper presents a numerical analysis on the thermal and energy performance of a group of air-cooled air conditioners installed at a courtyard of a high-rise building. The study introduces a series of new energy performance indices to assess the group performance of the AC condensers with different outdoor unit layouts. The results not only indicate the COP of the systems, but also quantify the system capacity and energy consumption. The evaluation method and indices developed are useful for guiding the design of the distribution plan of the AC units at building re-entrants.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.5
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• pp.178-185
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• 2016

This study describes the analysis of a 20 MW chilled water plant used for the IT cooling of a recently constructed data center in Korea. The CFD model was developed with the aim of evaluating the impact of problems such as chiller failure on the water and air temperatures in the cooling system. The numerical model includes the chilled water hydraulic network and individual water-to-air CRAC units. The coupling between the IT server room air temperature levels and the cooling plant has enabled a full assessment of the cooling system design in response to system fault conditions to be performed. The paper examines an emergency situation involving the failure of the cooling plant, and shows how the inherent thermal inertia of the system along with additional inertia achieved through buffer systems allowed a suitable design to be achieved.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.446-475
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• 2000

Performance of a water-to-water multi-type heat pump system using R22 has been experimentally investigated. Total refrigerant flow rate was adjusted with a variable speed compressor and the refrigerant flow rate for two indoor units were controlled by electronic expansion valves. Evaporator outlet pressure of refrigerant and indoor unit outlet temperatures of secondary fluid were selected as controlled variables. Experiments were carried out for both cooling and heating modes using PID control method. Results show that the multi-type heat pump system can be adequately controlled by keeping control gains at certain levels for various operating conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.6
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• pp.375-382
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• 2010

Ondol heating, a kind of radiant floor heating, is a main method used in housing units in Korea. Building energy simulation including ondol and relevant facilities has not been performed due to its complexity. For evaluating energy consumption and indoor temperature variation, a new method should be proposed. At the present work, a dynamic simulation on ondol heating was tried by combining TRNSYS and EES. Characteristic functions for a pump, hot water coils and a gas boiler were simultaneously solved by EES, and calculated flow rates and supply temperature of hot water were provided as inputs of the active layer of TYPE 56 in TRNSYS. The results by the simulation on a typical housing unit in Korea shows a good trend in a viewpoint of actual behavior of ondol heating.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.757-761
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• 2009

Axial-flow cyclone separator cluster can be used for a dust removal device inside a heating, ventilation, and air conditioning(HVAC) system of subway station. In this study, 3-dimensional computational fluid dynamics(CFD) analysis was performed to compare single unit axial-flow cyclone with couple unit axial-flow cyclone cluster. It is shown that the performance of cyclone separator is not influenced by number of single units but influenced by ability of single unit.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.7
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• pp.460-467
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• 2010

In housing units constructed recently in Korea, the length of ondol coil is different in each room, so the flow rate of hot water is adjusted by setting valve opening. If the flow rate is not appropriate for heating load, the room temperature seriously deviates from the set temperature range for comfort. In particular, too small valve opening can induce a noise by cavitation. In order to adjust the valve opening, two methods by zone area and a new method by return temperature rise were modelled and simulated using TRNSYS and EES. As a result, heating energy consumption during one week was the same on three methods, but the room temperature of the new method minimally deviated from the range of set temperature with a low possibility of noise.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.3
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• pp.295-304
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• 1987

The purpose of this study is to develop a computer model for simulating the water-lit hium bromide absorption heat transformer (AHT) Including all major components and to find the flexibility in operation. The effect of source hot water temperature, cooling water temperature, useful hot water flow rate, cooling water flow rate and evaporator circulation flow rate were investigated. The coefficient of performance (COP), temperature boost $({\Delta}T\;=\;T_A\;-\;Ti)$ and concentration variations can be predicted. The performance study indicates that the performance of AHT increases for the waste hot water temperature increasing and with a decrease of the cooling water temperature. The effect on performances of useful hot water flow rape is significant except on temperature boost. Also the effects on performance of cooling water flow rate and evaporator circulation flow rate are small. It is shown that the computer program is valuable to predict the performance of absorp-tion heat transformer units at various working corditions.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.5
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• pp.540-551
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• 2005

In this research, We'll focus on warm environment and ventilation characteristics when utilizing intake ports, exhaust port and 4-way cassettes for removing heat and polluted air. Four way cassettes have been typical air conditioning units for offices since the multi air-conditioner was introduced. The following installation cases will also be discussed: 1) 4-way cassette's operation without intake ports and exhaust port. 2) Effect of the position of intake port and exhaust ports. 3) cooling air flow, temperature. distribution and local supply index according to the air flow rate from 4-way cassettes.

• Journal of the Korean housing association
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• v.20 no.4
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• pp.19-29
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• 2009

The purpose of this study is to evaluate the air diffusion performance of a range of indoor units for room airconditioners; the wall-mounted type, floor-standing type, and ceiling-mounted type. These types of units, which have been widely used in housing spaces, will be studied with respect to thermal comfort and the energy performance using CFD analysis. In this study, current air conditioning status and related problems in housing spaces are examined, and a CFD analysis is performed in order to compare and analyze the thermal comfort and energy efficiency across each type of indoor-unit using the PMV, ADPI, EUC and FCEI indexes. The analysis results collectively considering thermal comfort and energy performance indicated that the ceiling-mounted type 4-way indoor unit showed the best diffusion performance in terms of thermal comfort, and had the second best diffusion performance in terms of energy performance after the wall-mounted type under certain conditions.