Application of Differential Transformation Method to Study on Mixed Convection Heat Transfer and Entropy Generation with Nanofluids

• Main Authors: Bo-ShiuanChen, 陳柏軒
• Other Authors: Cha’o-Kuang Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/19486603694521187952

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 101 === This thesis applies the differential transformation method (D.T.M) to simulate the flow and heat transfer features of 47 nm- Al2O3/water nanofluids using single-phase approach. Besides, it probes into the irreversibility of the thermodynamic system based on the second-law analysis, also using the concept of Entropy Generation Minimization (EGM) to investigate the energy efficiency of the designs of devices with nanofluids. This study mainly analyzes mixed convection flow in a parallel-plate vertical channel with viscous dissipation effects; moreover, investigates the influence of flow with magnetic fields. For the thermal performance and entropy generation of nanofluids within a mixed convection flow with viscous dissipation effects in a vertical channel, the simulations are conducted at different mixed-convection dimensionless parameter (100≦Ξ≦500) and Brinkman number (0.005≦Br≦0.08). The results which are presented for various values of dimensionless parameters show the local Nusselt number at the hot wall with the use of nanofluids is higher than the use of water and increases with the raise of particle volume concentration. However, the local Nusselt number at the cool wall with the use of nanofluids is lower than the use of water when the Brinkman number is higher. When it comes to entropy generation, the average entropy generation number of nanofluids is lower than the average entropy generation number of water. Furthermore, using different models associated with the physical properties of a nanofluid reveals great deviations of computed results. Further the influence on the thermal performance and entropy generation of nanofluids by the effect of magnetic fields is investigated. In the study of the magnetohydrodynamic (MHD) flow, the transverse momentum balance equation has to take into account the Lorentz force and the energy balance equation has to take into account Joule heating. Simulations are conducted at low Hartmann number(Hm=2). After the simulation, the results show that under the influence of magnetic fields, the local Nusselt number at the hot wall of nanofluids is higher and increases with the raise of particle volume concentration. However, the local Nusselt number at the cool wall of nanofluids is lower and decreases with the raise of particle volume concentration when Brinkman number is higher. When it comes to entropy generation, the average entropy generation number of nanofluids is lower with magnetic fields.