• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.422-429
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• 1990

The experimental study investigates two aspects of counterflow sensible heat regenerator operation. First, it examines the regenerator performance in periodic steady state operation with spatially nonuniform inlet temperature in one of the fluid stream. Second, the study examines the transient response of a regenerator to a step change in the inlet temperature of one of the fluid streams. The effect of transient inlet temperatures is analyzed in terms of the response of the outlet fluid temperatures to a step change in temperature of one of the inlet fluid streams. The effect of temperature nonuniformities is analyzed in terms of the change of temperature nonuniformities is analyzed in terms of the change in steady state effectiveness due to a circumferential temperature distribution in one of the inlet fluid streams. an experimental analysis has been conducted using a counterflow, parallel passage, and rotary regenerator made from polyethylene film. Efficiencies follow similar trends with increasing matrix to fluid capacity rate ratio for the balanced and symmetric regenerator with nonuniform inlet temperature.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1049-1054
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• 2009

Sustainable housing design can contribute to dramatically reduced energy usage and can be applied to all new building projects. This paper explores the potential in Korea of applying available energy efficient building technologies. The objective was to determine the degree of energy reduction that can easily be achieved in new building design. The pilot project is providing some prototypes with display units which incorporate principles of sustainable design and performance utilizing the eco-design objectives. This building challenges ingrained preconceptions about system designs for four energy saving levels(40%, 60%, 80% and zero energy) and exposes barriers to low energy buildings posed by new standards and guidelines.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.3
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• pp.29-35
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• 2012

Geothermal heat pump system has been spotlighted as an efficient building energy system, because it has great potentials for reducing energy in building air conditioning and reducing $CO_2$ emissions. However, higher initial cost is a barrier to the promotion of its use. Energy-pile and energy-slab are known as low cost ground heat exchangers comparing with conventional ground heat exchangers, because they utilize building structures as ground heat exchangers. This paper presents the daily cooling performance of a geothermal heat pump system with energy-pile and energy-slab. The energy-piles and the energy-slabs are connected to heat pump units in parallel. The cooling capacity of the system was nearly constant due to the stability of the ground heat exchangers. The stability of the energy-pile was a little higher than that of the energy-stab as a heat sink.

• Journal of Drive and Control
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• v.15 no.4
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• pp.11-16
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• 2018

Pilot operated control valve for $CO_2$ refrigerant is a valve that can perform various functions according to the user's intention by replacing pilot units, widely used for flow rate, pressure, and temperature control of refrigeration and air conditioning systems. In addition, $CO_2$ refrigerant, that requires high pressure and low critical temperature, can be installed and used in all positions of the refrigeration system, regardless of high or low pressure. In this paper, response characteristics are modeled and analyzed based on behavior of the main piston of the pilot-operated control valve. Although various factors influence operation of the main piston, this paper analyzes the effect of equilibrium pressure depending on valve installation position and application, and inlet and outlet orifice size of the load pressure feedback chamber to determine feedback characteristics of the main piston. As a result, it was possible to quantitatively analyze the effect of change in equilibrium and load pressure feedback chamber flow path size on the change in main piston dynamic and static characteristics.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1830-1837
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• 2023

The thermal cutting of contaminated or activated metals during decommissioning nuclear power plants inevitably results in the release of radioactive aerosol. Since radioactive aerosols are pernicious particles that contribute to the internal dose of workers, air conditioning units with a HEPA filter are used to remove radioactive aerosols. However, a HEPA filter cannot be used permanently. This study evaluates the efficiency and lifetime of filters in actual metal cutting condition using a plasma arc cutter and a high-resolution aerosol detector. The number concentration and size distribution of aerosols from 6 nm to 10 ㎛ were measured on both the upstream and downstream sides of the filter. The total aerosol removal efficiency of HEPA filter satisfies the standard of removing at least 99.97% of 0.3 ㎛ airborne particles, even if the pressure drop increases due to dust feeding load. The pressure drop and particle size removal efficiency at 0.3 ㎛ of the HEPA filter were found to increase with repeated cutting experiments. By contrast, the efficiency of used HEPA filter reduced in removing nano-sized aerosols by up to 79.26%. Altogether, these results can be used to determine the performance guidance and replacement frequency of HEPA filters used in nuclear power plants.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1341-1346
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• 2008

This paper presents the heating performance of a water-to-refrigerant type ground source heat pump system (GSHP) installed in a school building. The evaluation of the heating performance has been conducted under the actual operating conditions of GSHP system in the winter. Ten units with the capacity of 10 HP each were installed in the building. Also, a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth was constructed for the GSHP system. For analyzing the heating performance of the GSHP system, we monitored various operating conditions, including the outdoor temperature, the ground temperature, and the water temperature of inlet and outlet of the ground heat exchanger. Simultaneously, the heating capacity and the input power were evaluated for determining the heating performance of the GSHP system. The average heating coefficient of performance (COP) of the heat pump was found to be 5.1 at partial load of 46.9%, while the overall system COP was found to be 4.2.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.788-793
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• 2008

This paper presents the heating performance of a water-to-refrigerant type ground source heat pump system (GSHP) installed in a school building. The evaluation of the heating performance has been conducted under the actual operating conditions of GSHP system in the winter. Ten units with the capacity of 10 HP each were installed in the building. Also, a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth was constructed for the GSHP system. For analyzing the heating performance of the GSHP system, we monitored various operating conditions, including the outdoor temperature, the ground temperature, and the water temperature of inlet and outlet of the ground heat exchanger. Simultaneously, the heating capacity and the input power were evaluated for determining the heating performance of the GSHP system. The average heating coefficient of performance (COP) of the heat pump was found to be 5.1 at partial load of 46.9%, while the overall system COP was found to be 4.2.

• Journal of The Korea Institute of Healthcare Architecture
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• v.29 no.1
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• pp.43-51
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• 2023

Purpose: To accommodate the increasing number of patients during the COVID-19 pandemic, numerous portable HEPA filter units (PHUs) were installed in the general wards of existing medical facilities(EMFs) to convert them into emergency conversion facilities (ECFs). The purpose of this study was to build a dataset in preparation for emerging infectious diseases in the post-COVID-19 era by analyzing the construction and operation of ECFs. Methods: Field investigations were conducted during ECF operation periods based on the analysis of heating, ventilation, and air conditioning (HAVC) system design documents for six ECFs across Korea. Interviews were conducted with facility managers during the field investigations. Results: When constructing an ECF within an EMF, the installation status and characteristics of the existing system should be considered. Field investigations and verifications of the operation of HAVC systems must be conducted beforehand for smooth ECF operations. If heating and cooling are required with indoor air circulation type equipment in an ECF zone, the implementation of a heating and cooling method that can satisfy the comfort requirements of the occupants while minimizing cross-contamination is essential. When using PHUs that do not meet the performance standards required by medical equipment, the noise level resulting from such equipment operation must be evaluated and improved. Implications: For EMFs, various guidelines that can be referred to for the construction and operation of ECFs must be developed to prepare for emerging infectious diseases in the future.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.553-562
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• 2012

Computational Fluid Dynamics (CFD) analysis has been performed to estimate the air temperature inside an Auxiliary Feed Water (AFW) Motor-Driven (MD) pump room for the case where there is loss of Heating, Ventilation, and Air-Conditioning (HVAC). A transient calculation for the closed pump room without cooling by any HVAC system shows that the volume-averaged air temperature reaches around $60^{\circ}C$ for a transient period of 8.0 h. From previous studies, the external air and surface boundary temperatures are assumed to increase slowly starting from an initial temperature of $35^{\circ}C$. For the cases where the door is opened at 2, 4, and 6 h after the initiation of HVAC failure, the average air temperature promptly drops by about $4^{\circ}C$ when the door is opened and then slowly increases. The current calculations based on the CFD technique predict the rate of increase of air temperature to be lower than that determined by previous conservative calculations on the basis of a lumped model.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.288-293
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• 2008

The cooling load in winter is significant in many commercial buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. The development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the performance of a multi-heat pump with 3-piping system was investigated as a function of refrigerant charge and its performance was analyzed in cooling mode, heating mode, and heat recovery mode. COP in the heating or cooling mode showed little dependence on refrigerant charge at overcharge conditions, while those were strongly dependent on refrigerant charge at undercharge conditions and outdoor inlet temperature. In the heat recovery mode, the performance of the system was very sensitive to charge amount at all conditions. Optimum charge amount in the heat recovery mode was 14% lower than that in the cooling mode at the standard condition because the refrigerant only passed the indoor units. It is required to store the excessive refrigerant charge in a storage tank to optimize the system performance at operating modes.