• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.537-543
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• 2015

Air-source heat pumps are widely used in winter as heating units due to their higher efficiency compared to electronic heaters or gas fired equipment. However, the air-source heat pump can cause discomfort during periodic defrosting operations. In this study, a PCM unit for continuous heating was adopted to solve this problem. The PCM unit consisted of a PCM, a heat exchanger, and control valves. It was installed between the outdoor and indoor units. The performance of the proposed system was measured during both defrosting and heating operations. The indoor unit showed an average leaving temperature of $26^{\circ}C$ after adopting the PCM unit for continuous heating during the defrosting operation.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.453-458
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• 2009

This paper presents a numerical evaluation of the flow rate of air conditioner outdoor unit as function of shroud design parameters. To determine the optimal design parameters, we investigated the flow rate by changing bell mouth height, fan height, fan guide height, fan width. The evaluation of the relative priority of the design parameters was performed to choose three important parameters in order to use a response surface method. The flow rate of the optimum model, compared to that of the base model, was increased by about 6.25%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.780-786
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• 2001

For the compressor speed control of a multi-type air conditioning system, a fuzzy control algorithm was developed. The sum of zone temperature errors and its derivative were used as input variables, and the compressor speed was selected as the output variable. To test the effectiveness of the control algorithm, one outdoor environmental chamber and four indoor environmental chambers were used. In the chambers the zone temperature step change test and the indoor unit change over test were performed. Test results showed that, for the control of compressor speed, the fuzzy control algorithm was more effective than the conventional proportional control algorithm for the energy conservation.

• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.11-18
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• 2014

Chilled Beam system is the kind of water-air system which reduces the conveyance energy for air conditioning as well as allows efficient installation and comfortable indoor environment, and has been increasingly popular mainly in Europe. To effectively install such Chilled Beam system domestically, it is necessary to develop the product considering domestic climatic condition and the requirements for air conditioning system, and particularly the way to deal with condensation during operation of cooling system in summer shall be provided. In this study, the optimal design on induction structure of Chilled Beam unit was carried out through a numerical method, and the performance test for the prototype of unit was conducted in a real-scale experiment facilities of Chilled Beam unit. While the flowrate of 1st air is 101.3 CMH, the pressure in pressure chamber is 158.7 Pa and the cooling capacities of 1st air side and 2nd air side are 498.1 W and 709.5 W respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.1
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• pp.44-54
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• 1993

This is an experimental study to identify the performance of air-to-air rotary heat exchanger with polyurethane foam matrix. The experimental apparatus including heating AHU(Air Handling Unit), cooling AHU, sensor chamber, and heat exchanger testing unit was designed and manufactured in this study. The performance of heat exchanger with porous polyurethane foam matrix was tested with variations of the density and the thickness of matrix, regulating the wind velocity and the rotational speed of matrix. The actual heat recovery effectiveness, air leakage rate, and pressure drop of heat exchanger were measured and analyzed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.75-80
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.158-163
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• 2001

Performance of the water direct contact air conditioning system, in which heat and mass are transferred directly between air and water droplet, is simulated by semi-empirical method. This system improves transport efficiency compared to conventional indirect contact system and cooling, heating, dehumidification and humidification are attained with one unit. In this study, temperature and flowrate for air and water are measured in the various cooling and heating conditions, and correlations for $h_{c}A/c_{pm}$ are derived from these data. Cooling and heating characteristics of the water direct contact air conditioning system are investigated using correlations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.6
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• pp.518-523
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• 2003

The purpose of this study was to reduce the noise emitted from the package air-conditioner. The optimum design methods of the fans ware investigated experimentally through the analysis of noise problem caused by the conventional PAC system. New PAC system had decreased 6 dBA in overall noise level as compared with the conventional system by various technology.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.462-471
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• 1997

The water-to-air heat pump system requires relatively lower energy consumption and less installation space. The heat exchangers used for this system are the finned-tube type for the indoor unit and the double-tube type for the outdoor unit. Mathematical models for this system are developed and programmed in computer. Experimental data from various conditions are obtained and compared with calculated values from the computer simulation program. Differences of cooling capacity and COP are 1.25% and 0.47%, and those of heating capacity and COP are 0.51% and 0.13%, respectively. Simulation results are in good agreement with test results. Therefore, the developed program is effectively used for the design and the performance prediction of water-to-air heat pump system.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.2
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• pp.37-44
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• 2009

It is well known that a refrigerant-induced noise is caused by two-phase flow in the indoor unit of a heat pump air-conditioner. Especially when the flow pattern in a pipe is intermittent flow, the irregular noise occurs frequently. But it is very difficult to avoid this kind of the noise for the application of air-conditioner. Therefore, in this research, the flow patterns at two-phase flow state in a pipe of the indoor unit for the air-conditioner are researched using cycle simulator at typical cycle conditions. In order to find the relationship between refrigerant-induced noise and flow pattern, the noise patterns are investigated with respect to the estimated flow pattern from the various flow pattern maps. Base on the estimations of the flow patterns by those maps, the refrigerant-induced noise is evaluated as decreasing tube diameter, which can transit the flow pattern from slug to annular flow.