• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.695-700
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• 2009

Maintaining an IAQ with fresh in school building is very important because the good IAQ can be possible to improve the academic performance. Since school buildings are very dense and require a lot of fresh air, the need for ERV(Energy Recovery Ventilator) has become obvious. While opening a window does provide ventilation, the building's heat and humidity will then be lost in the winter and gained in the summer, both of which are undesirable for the indoor climate and for energy efficiency. ERV technology offers an optimal solution: fresh air, better climate control and energy efficiency. However, when the outdoor air condition is favorable to control the indoor environment such as spring and autum in Korea, heat exchange in ERV would rather increase the cooling load than diminish. Economizer cycle control which using the outdoor air in controlling the indoor thermal environment has many benefit in terms of energy saving and IAQ control. In this study, the ERV with economizer cycle control will be suggested. And then the system control characteristics and energy saving effect will be analyzed through the TRSNSYS Simulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.1-6
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• 2017

In order to better save energy, many buildings have been constructed with high levels of insulation and airtightness in recent years. Additionally, having high quality indoor air has become more relevant, necessitating a ventilating system. This study is aimed at evaluating the performance of a humidity exchanger through computational fluid dynamics (CFD) analysis of elements for the purpose of providing comfortable indoor air and reduced energy consumption. The simulation was conducted with three different shapes (triangle, rectangular, and curve) of heat exchanger elements, in order to find the most effective element. A follow-up simulation then proved the efficiency of the chosen humidity exchanger, which was selected by analyzing the results of the preceding simulation, comparing study data with measurement data from the Korea Testing Laboratory (KTL). The resulting analysis revealed that the rectangular element showed the lowest level of efficiency in both heating and cooling, while the curved element showed the highest level of efficiency in both heating and cooling.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.37-42
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• 2006

In this study, $20Nm^3/hr$ scale compact hydrogen generator which can be apply to the hydrogen station was tested for hydrogen station application. $20Nm^3/hr$ scale compact hydrogen generator was developed by upgrading concept of stacking plate reactor from former $20Nm^3/hr$ scale plate hydrogen generator. concepts for improving system efficiency and performance include such as idea of heat recovery from the exhaust, exhaust duct which is especially design for plate type reactor reinforcement of insulation, enlargement of heat exchange area of reactor, introduction of desulphurizer reactor and PROX rector in a compact design, introduction of back fire protection structure of plate burner and so on, We can learn that final prototype of scale-up $20Nm^3/hr$ scale compact hydrogen generator can be operated steadily in 100% road at which over 94% of methane conversion(S/C=3.75) was obtained. In case of making up the weak point, we expect that it is possible to apply to hydrogen station by way of showing an example.

• Journal of Power System Engineering
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• v.17 no.6
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• pp.130-135
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• 2013

It is a research about the change in reduction efficiency and performance resulting from installation of the EGR cooler, which is the core technology reducing NOx in response to standards been tightened of exhaust controls for off-road vehicle. It can reduce NOx by altering combustion temperature and oxygen concentration by recycling high-temperature exhaust gas. The target engine was large diesel engine for construction machine through by which we were able to verify a rate of change in output and capabilities for a heat-exchange within cooler itself depending on the existence of EGR cooler system. We have acquired a emission reduction technology for a construction machine by testing the reduction performance and rate of change in output.

• Journal of Hydrogen and New Energy
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• v.32 no.4
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• pp.236-244
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• 2021

Fuel cell systems for medium duty truck require high power demands under driving. Since high power demands results in significant heat generation, thermal management is crucial for the performance and durability of medium duty truck. Therefore, various configurations of dual stacks with cooling systems are investigated to understand appropriate thermal management conditions. The simulation model consists of a dynamic fuel cell stack model, a cooling system model equipped with a controller, and the mounted controller applies a feedback controller to control the operating temperature. Also, In order to minimize parasitic power, the comparison of the cooling systems involved in the arrangement was divided into three case. As a result, this study compares the reaction of fuel cells to the placement of the cooling system under a variety of load conditions to find the best placement method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.489-498
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• 1998

Among the heat/mass exchange units composing an absorption system, the absorber, where the refrigerant vapor is absorbed into the liquid solution is the one least understood. In the present study, the effects of non-absorbable gas on the absorption process of aqueous lithium bromide solution falling film inside a vertical tube were experimentally investigated. In the range of film Reynolds number of 30 ~ 195, heat and mass transfer characteristics were investigated as a function of non-absorbable gas volumetric concentration, 0.2 ~ 20%. An increase of non-absorbable gas volumetric concentration degraded the mass transfer rate dramatically in the absorption process. The reduction of mass transfer rate was significant for the addition of small amount of non-absorbable gas to the pure vapor. At film Reynolds number of 130, an increase of non-absorbable gas concentration from 0.2 to 6.0% resulted in the decrease of mass transfer rate by 36% and 20% of non-absorbable gas by 59%. However the decrease of film Nusselt number with the increase of volumetric concentration of non absorbable gas was relatively smaller than the decrease of Sherwood number. Critical film Reynolds number was identified to exist for the maximum heat and mass transfer regardless of the volumetric concentration of non-absorbable gases.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.659-664
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• 2016

Ash deposition of heat exchange boiler, caused mainly by accumulation of particulate matter, reduces heat transfer of the boiler system. Heat and mass transfer through porous media such as ash deposits mainly depend on the microstructure of deposited ash. Therefore, in this study, we investigated microstructural and thermal properties of the ash deposited on the boiler tube. Samples for this research were obtained from the fuel economizer tube in an industrial waste incinerator. To characterize microstructures of the ash deposit samples, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD) and BET analysis were employed. The results revealed that it had a porous structure with small particles mostly of less than a few micrometers; the contents of Ca and S were 19.3, 22.6% and 18.5, 18.7%, respectively. Also, the results showed that it consisted mainly of anhydrite ($CaSO_4$) crystals. - The thermal conductivities of the ash deposit sample obtained from the economizer tube in industrial waste incinerator were measured to be 0.63 and 0.54 W/mK at $200^{\circ}C$, which were about 100 times less than the thermal conductivity (61.32 W/mK) of the boiler tube itself, indicating that ash deposition on the boiler tube was closely related to a decrease in boiler heat transfer.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.89-94
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• 2011

The EGR system is one of important components in diesel engine. The regulation on NOx emission has been tightened up. Therefore, it is a significant issue to develop and commercialize the high efficient EGR cooler system that reduces NOx emission in DI diesel engine. Key performance factor of the EGR cooler system is how to properly design both wavy cooling fins and gas tubes. This paper proposes a high efficient EGR cooler that has been upgraded with both the optimized wavy cooling fins and the improved shape of structure. The evaluation of the heat exchange efficiency, outlet temperature, and gas pressure drop of the EGR cooler is performed with the prototype of the proposed EGR cooler. The result shows a good solution and will be implemented to the model of a clean diesel engine being developed for both domestic and overseas market.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.266-268
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• 2009

In this paper, authors deal with a power conditioning system (PCS) of high efficiency for a proton exchange membrane fuel cell (PEMFC) generation system. Fuel cells are a direct current (DC) power generators. They generate electricity through an electrochemical process that converts the energy stored in a fuel directly into electricity. Fuel cells have many benefits, which produce no particulate matter, nitrogen or sulfur oxides. And they have few moving parts and produce little or no noise. When fueled by hydrogen, they yield only heat and water as byproducts. Their wide application can reduce our dependence on fossil fuels and foreign sources of petroleum. This paper studies on a novel PCS circuit topology of high efficiency using in PEMFC generation system The controlling switches in the PCS is operated to soft switching. Some digital simulation results and experimental results for the proposed PCS is confirmed to the validity of the analytical results.

• Progress in Superconductivity and Cryogenics
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• v.21 no.2
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• pp.22-25
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• 2019

The superconducting magnetic separation system has been developing to separate the iron oxide scale from the feed water of the thermal power plant. The accumulation in the boiler lowers the heat exchange rate or in the worst case damages it. For this reason, in order to prevent scale generation, controlling pH and redox potential is employed. However, these methods are not sufficient and then the chemical cleaning is performed regularly. A superconducting magnetic separation system is investigated for removing iron oxide scale in a feed water system. Water supply conditions of the thermal power plant are as follows, flow rate 400 t / h, flow speed 0.2 m / s, pressure 2 MPa, temperature $160-200^{\circ}C$, amount of scale generation 50 - 120 t / 2 years. The main iron oxide scale is magnetite (ferromagnetic substance) and its particle size is several tens ${\mu}m$. As the first step we are considering to introduce the system to the chemical cleaning process of the thermal power plant instead of the thermal power plant itself. The current status of development will be reported.