LAMINAR DISSIPATIVE FLOW IN A POROUS CHANNELBOUNDED BY ISOTHERMAL PARALLEL PLATES

The effects of viscous dissipation on thermal entrance heat transfer in a parallel plate channel filled with a saturated porous medium,is investigated analytically on the basis of a Darcy model.The case of isothermal boundary is treated.The local and the bulk temperature distribution along with the Nusselt number in the thermal entrance region were found. The fully developed Nusselt number, independent of the Brinkman number, is found to be 6. It is observed that neglecting the effects of viscous dissipation would lead to the well-known case of internal flows,with Nusselt number equal to 4 93.A finite difference numerical solution is also utilized. It is seen that the results of these two methods, analytical and numerical, are in good agreement.

EFFECTS OF VISCOUS DISSIPATION ON THERMALLY DEVELOPING FORCED CONVECTION IN A POROUS SATURATED CIRCULAR TUBE WITH AN ISOFLUX WALL

The viscous dissipation effect on forced convection in a porous saturated circular tube with an isoflux wall is investigated on the basis of the Brinkman flow model. For the thermally developing region, a numerical study is reported while a perturbation analysis is presented to find expressions for the temperature profile and the Nusselt number for the fully developed region. The fully developed Nusselt number found by numerical solution for the developing region is compared with that of asymptotic analysis and a good degree of agreement is observed.

Computational fluid dynamics applied to high temperature hydrogen separation membranes

This work reviews the development of computational fluid dynamics （CFD） modeling for hydrogen separation, with a focus on high temperature membranes to address industrial requirements in terms of membrane systems as contactors, or in membrane reactor arrange- ments. CFD modeling of membrane,.s attracts interesting challenges as the membrane provides a discontinuity of flow, and therefore cannot be solved by the Navier-Stokes equations. To address this problem, tile concept of source has been introduced to understand gas flows on both sides or domains （feed and permeate） of the membrane. This is an important solution, as the gas flow and concentrations in the permeate domain are intrinsically affected by the gas flow and concentrations in the feed domain and vice-versa. In turn, the source term will depend on the membrane used, as different membrane materials comply with different transport mechanisms, in addition to varying gas selectiv- ity and fluxes. This work also addresses concentration polarization, a common effect in membrane systems, though its significance is dependent upon the performance of the membrane coupled with the operating conditions. Finally, CFD modeling is shifting from simplified single gas simulation to industrial gas mixtures, when the mathematical treatment becomes more complex.

Thermal characteristics of melting of a phase change material enhanced by a stainless-steel 304 periodic structure

In this work,melting of a high-temperature inorganic phase change material(PCM)eutectic(with a melting point of 569℃)within a vertical cylindrical tank has been experimentally investigated.To promote the heat transfer rate,a periodic structure that is constructed by a commercial SS-304 mesh screen has been considered and immersed into the PCM tank.Thermal characteristics of the PCM-periodic structure tank under different initial temperatures(450,490 and 546℃)and wall temperatures(620,640,660,680 and 700℃),are then investigated and reported.The presented experimental data can facilitate practical engineers to find the best operating condition of similar PCM tanks;meanwhile,it can also be employed for the investigation of thermal response of transient heat conduction before melting starts.