• Proceedings of the KSME Conference
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• 2003.04a
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• pp.585-590
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• 2003

The distributions of mass flow rate and pressure are major factors to deside the performance of a proton exchange membrane fuel cell (PEMFC). These factors are affected by channel configuration of air plate. In this paper. structural analysis is performed to investigate deformation of porous media. Two kind of models are suggest for flow analyses. Deformed porous media and undeformed porous media are considered for air plate model. The Numerical flow analysis results with deformed porous media and undeformed porous media had some discrepancy in pressure distribution. The pressure and velocity in a working condition are numerically calculated to predict the performance of the air plates. Distributions of the parameters in the PEMFC are analyzed numerically under steady-state conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3021-3031
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• 1994

Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

• Journal of the Korean Society of Visualization
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• v.20 no.2
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• pp.63-69
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• 2022

In this study, we numerically simulate the condensational growth of micron-sized particles traveling through a pipe filled with humidified air. Using the finite volume method and Lagrangian particle tracking technique, the mixture of particle-laden flow with moist air in a T-juction pipe is simulated. The condensational growth of particles is calculated by considering the mass transfer of vapor in the air onto the particle surface. The results indicate that the growth rate of the particles increases as the relative humidity of air is higher. Furthermore, the placement of a porous media with low permeability in the pipe could enhance the degree of condensational growth.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.165-172
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• 2005

Heat transfer enhancement of three types of brazed plate heat exchangers has been evaluated experimentally. The effects of flow resonance in a plate heat exchanger on the heat transfer rate and pressure drop have been investigated in a wide range of mass flow rates in detail. The problem is of particular interest in the innovative design of a plate heat exchanger by flow resonance. The results obtained indicate that both heat transfer coefficient and pressure drop are increased as mass flow rate is increased, as expected. It is also found that the heat transfer enhancement is increased with an increase in the plate pitch, while the heat transfer is decreased with a decrease in the chevron angle. Pressure drop also increased with an increase in the plate pitch and with a decrease in the chevron angle. Heat transfer enhancement in the plate heat exchangers is maximized by flow resonance and the resonance frequency of the present plate heat exchangers is found to be in the range of $10~15\;Hz$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.741-748
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• 2002

The present study investigated the two-phase flow characteristics of refrigerant R-22 in T-branch with horizontal and vertical inlet tube The key experimental parameters were the orientation of inlet and branch tubes (horizontal and vertical), diameter ratio of branch tube to inlet tube (1 and 0.61), inlet mass flux (200~500 kg/$m^2$s) and inlet quality (0.1~0.4). Predicted pressure profile agreed with the measured data within 25.4%. The flow distribution ratio decreased as the mass flux increased. The flow distribution ratio decreased by 12~25% as the tube diameter ratio decreased from 1 to 0.61, and decreased by 38~47% as the orientation of branch changed from horizontal to vertical upward for horizontal inlet tubes. As the orientation of inlet tube changed from horizontal to vertical upward for horizontal branch, the flow distribution ratio increased by 15~68%, but the quality in the branch tube decreased by 28~92% due to phase separation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.7
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• pp.386-393
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• 2009

The present study has been studied on a thermal and flow characteristic of the microchannel waterblock with flow distributions in each channels. Results of a numerical analysis using the CFX-11 are compared with results of an experiment. Numerical analysis and experiment are conducted under an input power of 150 W, inlet temperature of $20^{\circ}C$ and mass flow rates of $0.7{\sim}2.0$ kg/min. Base temperature and pressure drop are investigated with standard deviations of mass flow rates in each channels of samples. The flow distribution and j/f factor of the sample 4 is increased by about 65.7% and 42.6%, compared to that of the reference model sample 3.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.187-192
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• 2000

The textile which is rotated in the tumbler dryer is dried by the heated air. the energy consumption for drying textile depends on various parameters. The objective of this study is to save the energy and the drying time. One of the various methods for energy saving is EGR(exhaust gas recirculation). We set the drying equipment for this study and perform the experimental study with the changes of the recirculation rate, the input power, and the air mass flow rate. We found the optimal drying conditions.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1783-1788
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• 2004

In the present paper, a micro flow sensor, which can be used at bio-delivery systems and micro heat pumps, is developed. For this, the micro flow sensor is integrated on a quartz wafer ($SiO_2$) and is manufactured by simple and convenient microfabrication processes. The micro flow sensor aims for measuring mass flow rates in the low range of about $0{\sim}20$ SCCM. The micro flow sensor is composed of temperature sensors, a heater, and a flow microchannel. The temperature sensors and the heater are manufactured by the sputtering processes in this study. In the microfabrication processes, stainless steel masks with different patterns are used to deposit alumel and chromel for temperature sensors and nichrome for the heater on the quartz wafer. The microchannel is made of Polydimethylsiloxane(PDMS) easily. A deposited quartz wafer is bonded to the PDMS microchannel by using the air plasma. Finally, we confirmed the good operation of the present micro flow sensor by measuring flow rate.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.43-48
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• 2001

Combustor design technique is established by reverse engineering of existing combustor and applying heat & mass balance equations for the combustion process. The ratio of entrained air for each air slot is found to be almost proportional to the area ratio from the result of numerical simulation. The shape of the combustor is modified by the numerical analysis to get circumferentially uniform flow inside the combustion chamber required for the flame stability.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.6
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• pp.461-470
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• 2003

The purpose of this study is to investigate the performance of a transcritical cycle for hot water heating using $CO_2$ as a working fluid. Some of the main parameters that affect the practical performance of the $CO_2$ system are discussed; the performance on the variation of refrigerant charge, changes in flow conditions of secondary fluids, and that with or without internal heat exchanger, The experimental results show that the optimum charge is approximately the same for various mass flow rates of the secondary fluid at gas cooler. The experimental results on the effect of secondary fluids are in general agreement with the experimental results of transcritical cycle in the open literature and show similar trend for conventional subcritical vapor compression cycles. The heat exchanger effectiveness increases with an increase of the heat exchange area of the internal heat exchanger regardless of the mass flow rate at the gas cooler.