Heat and Mass Transfer for Liquid Film Evaporation along an Inclined Plate Covered with a Porous Layer

• Main Authors: Yin Chou, 鄒穎
• Other Authors: Jiin-Yuh Jang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/75404511181857311753

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 93 === Abstract 　Two main topics have been studied numerically in this thesis：First is to study the co-current liquid film evaporation along an inclined plate. The second is to evaluate the heat and mass enhancement of liquid film evaporation by covering a porous layer. The present investigations include： 　 　(1) For the liquid film evaporation along an inclined plate, the parametric analyses such as the inlet water flow rate, inlet air flow rate and the angle of inclination are examined in detail. For numerical analysis, the upstream scheme is used to model the convection term in flow direction (x direction), while the second-order central difference schemes are employed for the transverse convection and diffusion terms. The discretization equations are solved by the Box method. The numerical results show that the variations of liquid film thickness and liquid velocity are significant for lower inlet liquid mass flow rate and inclination angle. And the interfacial temperature and concentration are increased for such above situations. In addition, as the liquid mass flow rate is 0.3% of the air flow, the heat transfer enhancement is about to 8%~22%. Compared with the experimental results, the error of numerical results are within 20% 　(2) For the liquid film evaporation covered with a porous layer, the non-Darcy inertia and boundary effects are included. The corresponding parametric analyses on features such as gas inlet conditions (Reynolds number and ambient relative humidity f) and the structural properties of the porous material (porosity e and thickness of the porous layer d) on the performance of liquid film evaporation are examined in detail. The results show that both the average Nusselt and Sherwood numbers are increased with the decrease of e, d and f. In addition, as the Lewis number increases (Le>1), a larger heat transfer rate and mass flow rate are achieved.