• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.243-249
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• 2005

The present study has been conducted to simulate dynamics of a gas engine-driven heat pump(GHP) for design of control algorithm. The dynamic modeling of a GHP was based on conservation laws of mass and energy. For automatic control of refrigerant pressures, actuators such as engine speed, outdoor fan, coolant three-way valves and liquid injection valve were PI or P controlled. The simulation results showed physical behavior that is realistic enough to apply for control algorithm design.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.60-68
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• 1993

Flows inside a passenger compartment of a 1/5 scale model vehicle have been simulated by using a general purpose FVM code, TURBO-3D. Three HVAC modes of heating, air-conditioning, and defrosting are simulated by defining three different inlets. Comparisons are made with the published experimental and computational results, giving a good agreement. A method of predicting the defrosting contours on the wind shield is also proposed in the present study, which enables design modifications in design stages.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2165-2170
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• 2008

The cooling load in winter season is significant in many commercial buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Therefore, the development of a multi-heat pump which can cover heating and cooling simultaneously for each indoor unit is required. In this study, the characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-only and cooling-main operating mode was investigated experimentally with a variation of indoor air dry bulb temperature which is from $21^{\circ}C$ to $35^{\circ}C$. EEV opening was adjusted from 20% to 24% during the tests. When the indoor air temperature varied, the performance in the cooling-only mode was more sensitive to the temperature than in the cooling-main mode. The total capacity and COP were increased by 53.8% and 48.1%, respectively, in the cooling-main, while those were increased by 19.6% and 19.3% in the cooling-only mode. The performance differences between the two operating modes became larger at lower temperatures, especially for the COP.

• Fire Science and Engineering
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• v.20 no.3 s.63
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• pp.9-14
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• 2006

In this study boundary velocity which is one of the important boundary conditions for numerical simulation for subway station on fire are experimentally obtained. The tests were conducted according to its operating mode of the ventilation systems in the platform: smoke extraction ventilation mode in occurrence of fire and normal ventilation mode for air conditioning. Velocities are measured at various points on the platform. To examine smoke extraction and air supply capacity in the platform level, air velocities were checked on opening vents. Numerical analysis under normal ventilation mode without fire is conducted by using measured boundary conditions, and the numerical results are compared with the measured velocities on the platform.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.52-57
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• 2009

This paper describes the multi-heat pumps applied in an ground source heat pump system for an actual building. The performance of a ground source multi-heat pump installed in the field was investigated at heating season. The average COP of the systems with single U-tube and double tube type GLHXs were 4.8 and 5.0, respectively. It is needed to investigate the long term performance of double tube type GLHX, because the reduction of inlet temperature of OD HX for this GLHX was larger than it for U-tube GLHX.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.57-65
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• 2013

The temperatures with the ground depth, the positions of circulation water in ground heat exchanger were measured and thermal diffusion characteristics with the distances of the direction normal to the borehole was analysed. The deeper the depth of ground, the less the influences of outdoor temperature, but below 10m of ground, there was no influences of ground temperature. When the depth of trench pipe was below the depth of 2m, there was no influence. In the ground of 10m when the distances between the pipe and the other places were above 0.5m, the variations of temperature were less than $1.6^{\circ}C$ and above 2.5m they were less than $0.1^{\circ}C$. When the distances of bore hole were above 5m, there were no. influences of the nearest ground heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.314-320
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• 2008

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the improved wall insulation. Hence, a multi~heat pump is required to cover heating and cooling simultaneously for each indoor unit. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the cooling-main operating mode were investigated experimentally. The system adopted a variable speed compressor using R410A with four indoor units and one outdoor unit. In the cooling-main mode, the heating capacity decreased due to reduction of flow rate to the indoor unit under heating mode operation. The EEV opening was adjusted to increase flow rate to the indoor unit under heating mode operation. The total capacity and COP in the cooling-main mode increased by 20.5% and 29.2%, respectively, compared with those in the cooling-only mode.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2393-2400
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• 2013

This research presents an experimental study of heat exchange rate of U, W, 2U and coil type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). The four types of GHEs were installed in a partially saturated dredged soil deposit of Incheon International Airport area. Thermal response tests (TRTs) were conducted for U, W and 2U type GHEs to deduce the ground thermal conductivity. Besides, TPTs were also conducted for U, W, 2U and coil type GHEs to evaluate heat exchanger rates under 100-hr continuous and 8-hr intermittent operation conditions for five days. Coil shaped GHE showed about twice higher thermal performance than the others GHEs. Furthermore, intermittent operation condition showed 30~40% higher heat exchange rates than continuous operation condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.5
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• pp.297-304
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• 2009

The aim of this study is to investigate the cooling performance of ground source multi-heat pump systems with a vertical single U-tube GLHX(U-tube system) and a vertical double tube GLHX(double tube system), which were installed in a school building located in Cheonan. All systems were operated in a part load conditions for all day, and the maximum COP of the single U-tube system and the double tube system were 6.2 and 5.2 at cooling mode, respectively. The double tube GLHX designed by the GLHEPRO, commercial program, was estimated to have the same performance as the U-tube GLHX, because the inlet temperatures of each outdoor unit heat exchanger for the former was similar to the latter. However, it is needed to prove the long tenn performance. It is suggested that the new algorithms to control the flow rate of secondary fluid for GLHX according to load variation have to be developed in order to enhance the performance of the system.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.21-26
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• 2008

Recently, small and medium-sized buildings have employed a multi-heat pump. The major benefits of the multi-heat pump over a conventional system are that it is easier system to maintain along with a diversification of facility use, and high comfortability. The performance of multi-heat pump systems can be enhanced by using geothermal energy instead of air source energy. This paper describes the multi-heat pumps applied in an ground source heat pump system for an actual building. The performance of a ground source multi-heat pump installed in the field was investigated in cooling mode. The maximum COP of the systems with single U-tube and double tube ground loop heat exchangers were 6.6 and 6.0, respectively. It is suggested that the new algorithms to control the flow rate of secondary fluid for ground loop heat exchanger have to be developed in order to enhance the performance of the system.