• Korean Chemical Engineering Research
• /
• v.49 no.5
• /
• pp.644-651
• /
• 2011

Storing hydrogen in solid state hydride is one of the best promising methods for the future hydrogen economy. The total performance of such systems depends on the rate at which the amount of mass and heat migration is supplied to solid hydride. Therefore, an accurate modeling of the heat and mass transfer is of prime importance in optimizing the design of such systems. In this work, Hydrogen storage in Pt-CNTs hydrogen reactor has been intensively investigated by solving 2 dimensional mathematical models. Using a CFD computer software, systematic studies have been performed to elucidate the effect of heat and mass transfer during hydrogen charging periods. It was revealed that the optimized design of hydrogen storage vessel can prevent the increase of system temperature and the charging time due to the convective cooling effects inside the vessels at even high charging pressure. Because none has reported the critical issues of heat and mass transfer for CNT based hydrogen storage system, this work can support the first insight of the optimal design for solid state hydrogen storage system based on CNT in the near future.

• Journal of Power System Engineering
• /
• v.17 no.3
• /
• pp.28-34
• /
• 2013

This study is experimentally performed for using the oyster shell as a desiccant in the fluidized bed with bundle of heating pipe. The test material is oyster shell from fishery wastes which can use without costs. The main parameters of experiment are inlet air temperature, velocity of inlet air and heat flux of heating pipes. Also the geometry of heating pipe is treated as important parameter. From this study, the effect of inlet air temperature and input heat flux have much affect to increase the heat and mass transfer. On the other hand, the effect of inlet air velocity has less affect to increase the heat and mass transfer. And it is clarified that the oyster shell has sufficient probability for using as a desiccant in air-conditioning system.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.9
• /
• pp.1325-1331
• /
• 2002

This study presents a numerical model to predict the behavior of frost layer growth. The characteristics of the heat and mass transfer inside the frost layer are analyzed by coupling the air flow with the frost layer. The present model is validated by comparing with the several other analytical models. It has been known that most of the previous models cause considerable errors depending on the working conditions or correlations used in predicting the frost thickness growth, whereas the model in this work estimates the thickness of the frost layer more accurately within an error of 10% in comparison with the experimental data. Simulation results are presented for variations of heat and mass transfer during the frost formation and for the behavior of frost layer growth along the direction of air flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.249-258
• /
• 1997

In this study, a numerical model for analyzing frost formation phenomena on a cold flat plate has been developed. Both regions of air flow and frost layer have been coupled to calculate the amount of the heat and mass transfer between air flow and frost layer. Experiments have been also conducted to validate the numerical model. The present numerical results show a good agreement with the experimental data. The present numerical model also provides some useful data such as the temperature distribution inside the frost layer which could not be obtained through the experiments.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.8
• /
• pp.1114-1121
• /
• 2003

A mathematical model considering the air side and the frost layer is presented to predict the frost layer growth. The standard k-$\varepsilon$ model for the air flow and the diffusion and energy equations for the frost layer are employed. The numerical results are compared with experimental data to validate the present model, and agree well with experimental data within a maximum error of 10%. The present model predicts well the frost properties and heat and mass transfer with respect to the frosting time. The variation of total heat transfer strongly depends on the operating condition, and has a similar trend to that of the sensible heat transfer. The frost properties along the flow direction are also investigated.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.6
• /
• pp.665-671
• /
• 2004

A mathematical model is presented to predict the frost properties and heat and mass transfer within the frost layer formed on a cold plate. The model consists of the laminar flow equations for air-side and the empirical correlation of local frost density. The correlation of local frost density used in this study is obtained from various experimental conditions by considering frosting parameters. The numerical results are compared with experimental data to validate the model, and agree well with experimental data within a maximum error of 9%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.4
• /
• pp.466-474
• /
• 1998

In the present study, the improvement of absorption characteristics by installing insert devices, such as spring and wire screen, inside the vertical tube absorber were studied experimentally. Momentum, heat and mass transfer rate in the absolution process of smooth bare tube, smooth tube with spring-insert, and with wire screen-insert were compared and analysed in range of film Reynolds number of 40∼200. The improvement of heat transfer rate by spring-insert and screen-insert were remarkable especially in the low Reynolds number region. As the mesh number increased in screen-insert and as the pitch decreased in spring-insert, Nusselt and Sherwood number increased. Degradation of mass transfer by non-absorbable gas showed similar qualitative trends regardless of the insert type.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.6
• /
• pp.981-992
• /
• 2004

Freeze drying under vacuum condition is a complex process that involves simultaneous heat and mass transfer, sublimation of ice, and motion of sublimation front. Proper treatment of the motion of sublimation interface is crucial for an accurate prediction of the freeze drying process. Based on the enthalpy formulation that has been successfully used in liquid/solid phase change problems. a fixed grid method. streamlined for the freeze drying analysis. was developed in this study. The accuracy of the fixed grid method was checked by solving a one-dimensional tray freeze drying and a two-dimensional vial freeze drying problem and then comparing the results with those by the moving grid method. Finally. the freeze drying characteristics of two-dimensional slab and axis-symmetric cylinder was investigated using the fixed grid method.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.11a
• /
• pp.340-343
• /
• 2006

In this paper, heat and mass transfer characteristics through experimental and numerical study are extensively investigated in steam reform ins reactor under given operating conditions. In order to get simulated data at outlet of the reformer, heterogeneous reactor model is incorporated. As the reaction also takes place in porous media, two medium approach is used to take into account thermally non-equilibrium phenomena between catalyst and bulk gas. In steam reforming reaction, heat transfer issue is so significant that geometrical configuration study is also conducted.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.3
• /
• pp.261-267
• /
• 2002

The integral boundary layer equation for the air side and the diffusion equation for the frost layer are numerically analyzed in order to predict the behavior of frost layer growth. The thickness and density of the frost layer obtained from the present study agree well with those of previous numerical results and experimental data with a maximum error of 13%. The characteristics of heat and mass transfer within the frost layer and the frost layer growth along the flow direction are investigated by performing numerical analysis. The effects of operating conditions on the frost layer growth are also examined.