• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.277-280
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• 2005

Air-breathing polymer electrolyte membrane fuel cells (PEMFC) are highly promising particularly for small-power applications up to tens watts class. A distinctive feature of the air-breathing PEMFC is its simple system configuration in which axial fans operate for dual purposes, supplying both oxidant and coolant in a single manner. In the present study, a nominal SOW air-breathing PEMFC system is developed and investigated to determine the optimal operating strategy through parametric studies (i.e., reactant humidity, and fan-blowing flow rate). The cell voltage distributions are examined as a function of time to evaluate the system performance under various operating conditions.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.477-482
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• 2011

In the present study, the diffusion process of hydrogen leaking from a FCV (Fuel Cell Vehicle) in an underground parking lot was analyzed by numerical simulations in order to assess the risk of a leakage accident. The temporal and spatial changes of the hydrogen concentration as well as the flammable region in the parking lot were predicted numerically. The effects of the leakage flow rate and an additional ventilation fan were investigated to evaluate the ventilation performance in the parking lot to relieve the accumulation of the leaked hydrogen gas. The present numerical analysis can provide useful information such as the distribution of the leaked hydrogen concentration for safety of various hydrogen applications.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.245-250
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• 2003

In order to control indoor air quality and save energy, it is needed to install a suitable ventilation system equipped with heat exchanger for heat recovery. The purpose of this research is to find the performance of paper heat exchanger for exhaust heat recovery, which exchanges latent heat as well as sensible heat. Experimental apparatus comprises heat exchanger model, constant temperature and humidity chamber, fan and measurement systems for temperature, pressure and flow rate. Thermal performance and pressure loss of the paper heat exchanger are measured and compared at various air velocities and outdoor conditions. Experimental results show that paper heat exchanger can recover $50{\sim}70%$ of the enthalpy difference between supply and exhaust air.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.71-77
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• 2003

To inject fresh air into a fire room, Positive Pressure Ventilation (PPV) can be used and the blower of PPV increases inside pressure of the room. It makes high flow rate of products of combustion, smoke and heat from the structure, and it is very helpful to fireman on the fire extinguishing work. The flame moves to the direction of airflow and the temperature of flame can be decreased rapidly. In this experiment, a water mist system is applied to PPV to increase the effectiveness, and various effective factors are studied. n-Heptane and pine wood stick were used as fuel. Temperatures at the above and behind the combustion pan were strongly reduced by the water mist system and by the convective cooling with airflow. The smoke density was also decreased by PPV with water mist system and it can be explained by the absorption of smoke particles on the water mist droplet and by the strong exhausting effects of mobile fan.

• Journal of Bio-Environment Control
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• v.26 no.3
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• pp.188-193
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• 2017

The purpose of this study was to investigate the changes of environmental conditions and the quality and yield of melon fruit by heat fan operation in greenhouses at winter season. The average daily temperature inside the tunnels during January 1 to 31, 2017 was $0.9^{\circ}C$ higher than that of the control $17.8^{\circ}C$. The air flow rate of heater fan treatment was 4.8 times higher than the control (untreated $0.05m{\cdot}s^{-1}$) at 20cm above the ground where the korean melon grew. The temperature of the heater pan was $5.6^{\circ}C$ higher than that of the untreated at $35.3^{\circ}C$ and the relative humidity was 8.1% lower than that of the untreated at 39.1%. The flowering rate of the heater fan treatment was 96%, 5% higher than the control. The number of first harvest days of heater fan treatment was shortened by 4 days than that of untreated treatment. Fruit quality and marketable fruit yield increased by 3.4% and 38% compared to untreated respectively, the heater fan treatment increased the temperature inside the greenhouse and air flow rete, which were beneficial for growing the korean melon in greenhouses at winter season.

• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.1001-1005
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• 2005

This paper evaluates the performance of ventilation for the removal of indoor pollutants as a function of ventilation rate and the number of occupants in a test room and school classroom. An experimental apparatus consists of a test room, a tracer gas supply system, a gas detector, and a fan for ventilation air supply with a controller. The ventilation performance is evaluated in a step-down method based on ASTM Standard E741-83 using $CO_{2}$ gas as a tracer gas in the test room of 35 $m^{3}.$ For the ventilation air flow rate of 1.0 ACH, a recommended ventilation flow rate of Korea school standard for acceptable indoor air quality in the case of one person, CO_{2}$ gas concentration decreases up to $55{\%}$ within 50 minutes without occupancy and increases up to $75{\%}$ in the case of one occupant. Also indoor air quality at the school classroom is investigated experimentally.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.216-222
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• 2016

Thus, this study aimed to develop a gear-type vane damper in order to replace the link-type vane damper. To achieve this goal, the torque generated in a gear-type vane damper was analyzed, and a structural analysis was conducted. In addition, the fluid flow was analyzed according to the changes in the vane's angle, and experimental tests such as a dry-heat test and cold test were conducted considering the operating conditions of the vessels. Moreover, an appropriate actuator was selected for the developed gear-type vane damper, and studies on the reduction in the backlash due to the facing-pressure adjustment length and flow rate and leakage test due to the vane's angle were conducted.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.334-339
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• 2008

An closed cooling tower is a device similar to a general cooling tower, but with cooling tower replaced by a heat exchanger. The purpose of this study is to evaluate thermal performance of heat exchanger at various conditions and to provide design datebase. The experimental study regarding heat exchanger for closed cooling tower was conducted. Experimental apparatus consists of constant temperature bath, water pump, spray nozzle, heat exchanger, fan, and date acquisition system. Heat transfer rates at various air velocitys, water flow rates, two different spray modes were measured and heat transfer coefficient were calculated to compare the thermal performances. This study provides that the heat transfer coefficient increases with increasing spray water flow rate and with increasing air velocity. The wet mode was more effective than dry mode for closed cooling tower to this study.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.895-910
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• 2013

The reflood test data from the rod bundle heat transfer (RBHT) test facility showed that the grids in the upper portion of the rod bundle could become wet well before the arrival of the quench front and that the sizes of liquid droplets downstream of a wet grid could not be predicted by the droplet breakup models for a dry grid. To investigate the water droplet generation from a wet grid spacer, a viscous linear temporal instability model of the water sheet issuing from the trailing edge of the grid with the surrounding steam up-flow is developed in this study. The Orr-Sommerfeld equations along with appropriate boundary conditions for the flow are solved using Chebyshev series expansions and the Tau-Galerkin projection method. The effects of several physical parameters on the water sheet oscillation are studied by determining the variation of the temporal growth rate with the wavenumber. It is found that a larger relative steam velocity to water velocity has a tendency to destabilize the water sheet with increased dynamic pressure. On the other hand, a larger ratio of steam boundary layer to the half water sheet thickness has a stabilizing effect on the water sheet oscillation. Droplet diameters downstream of the spacer grid predicted by the present model are found to compare reasonably well with the data obtained at the RBHT test facility as well as with other data recently reported in the literature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.11
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• pp.624-630
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• 2013

A truck refrigeration system using phase change material (PCM) is expected to have a lower noise level, reduced energy cost, and much lower local greenhouse gas emission. Recently, a forced convection type PCM refrigeration module has been developed. As the operation time increases, the PCM around the air inlet melts, because of a large temperature difference between the PCM and air. Therefore, the latent heat transfer area decreases and the heat transfer rate of the module decreases even though there is a lot of PCM which does not melt around the air outlet. A computational fluid dynamic modeling of the PCM refrigeration module was developed and validated by the experiment. Using the CFD, the design parameters, such as the mass flow rate of the air and roughness of the slab, were investigated to improve the heat transfer inhomogeneity. As a result, the adoption of partial roughness on the slabs improved the heat transfer inhomogeneity and reduced a fan power.