行政院國家科學委員會專題研究計畫 成果報告
子計畫五：重組器微流道催化層熱流設計(數值模擬)(II)
計畫類別： 整合型計畫 計畫編號： NSC92-2212-E-110-019- 執行期間： 92 年 08 月 01 日至 93 年 07 月 31 日 執行單位： 國立中山大學機械與機電工程學系(所) 計畫主持人： 楊儒 計畫參與人員： 蕭志豪、林松逸、姜彥竹、林鉍研、丁筱佩 報告類型： 精簡報告 處理方式： 本計畫可公開查詢 中 華 民 國 93 年 11 月 1 日The purpose of this project is to develop a numerical simulation ability by using the Lattice-Boltzmann-method (LBM) for modeling fuel cell reformer with micro- channel catalytic reforming process. The study provides data for reformer design.
The achievement of this project including: (a) the computer program for heat and mass transfer simulation of fuel cell reformer by using the LBM has been established; (b) many model problem cases have been studied to provide design reference.
The model problem studied in this simulation project is the methanol fuel catalytic reformer with 5 wt% copper on aluminum as catalyst and with micro channels. Considering the auto-thermal reforming process,
CH3OH+a(O2+3.76N2)+(1-2a)H2O
→ (1-a)CH3OH+aCO+H2O+3.76aN2
The product of partially burned methanol fuel with unburned methanol fuel are feed into micro reformer channel where reforming process takes place. The variation of channel length is from 200µm to 1000µm, channel height from 100µm to 500µm, inlet flow velocity from 0.05m/s to 1 m/s, and inlet temperature from 250℃ to 350℃. References [1] to [5] provide chemical reaction information for methanol fuel reform, and LBM technique in treating chemical reaction problems.
Figure 1 is the schematic of the model geometry. Fig 2 is a typical result for the variation of mass concentration of all species along the channel.
A typical result of channel length effect is shown in Fig. 3. Longer channel length provides more complete reforming results since the reaction time is longer. It is shown that 500µm in channel length is sufficient for most cases studied in this project.
A typical result of inlet velocity effect is shown in Fig 4. The rate of hydrogen product increases with the inlet velocity until a maximum value has reached.
After that inlet velocity, the product rate decreases due to that the shorter reaction time causes more incomplete reaction.
Fig. 5 indicates the inlet temperature effect on reforming performance. Higher Tin gives higher reaction rate and better performance. However, higher Tin
means more fuel burned for heating up the fuel before entering the reforming channel. The overall performance must be considered for reformer design. Fig 6 illustrates the effect of the channel height. Lower channel height corresponds to larger reaction surface for catalytic reformer.
In conclusion, this project has successfully developed a LMB simulation program for modeling fuel cell reformer with micro catalytic channel. The next project will extend the range of the parameters, and develop simulation program with other numerical technique (such as DFMC) for simulating micro channel reformer.
References
[1] A.V. Pattekar, M.V. Kothare, S.V. Karnik, and M.K. Hatalis, ”A microreactor for in-situ hydrogen production by catalytic methanol reforming”, Int.Conference on Microreaction Technology (IMRET5), Strasbourg France, pp.27-30, 2001
[2] H. Yu, Li-Shi Luo, S. S. Girimaji, ”Scalar Mixing and Chemical Reaction Simulations Using Lattice Boltzmann Method”, Int. J. Computational Engineering Science, Vol.3, NO.1, pp73-87,2002
[3] X. He and Li-Shi Luo, ”Theory of the lattice Boltzmann method：From the Boltzmann equation to the lattice Boltzmann equation”, Physical Review E, Vol.56, No.6, pp.6811-6817, 1997
[4] K. Yamamoto, X. He, and G. D Doolen, ” Simulation of Combustion Field with Lattice Boltzmann Method ”, J. Statistical Physics, Vol.107, Nos.112, pp.367-383, 2002
[5] P. Mizsey, E. Newson, T-b Truong, and P. Hottinger, “The kinetics of methanol decomposition: a part of autothermal partial oxidation to produce hydrogen for fuel cells”, Applied Catalysis A: General, Vol.231, pp233-237, 2001
catalyst layer
Fig. 1 The schematic of the micro-channel reformer.
Fig. 2 Variation of mass concentration of all species along the channel. (inlet velocity Uin
=1m/s, inlet temperature Tin =300℃, channel height H=200µm)
Fig. 3 Effect of channel length on reforming performance.(Tin=300℃, Uin=1 m/s,
Fig. 4 Effect of Uin on reforming performance.(Tin=300℃, H=200 µm, L=500 µm)
Fig. 5 Effect of Tin on reforming performance.(Uin =1 m/s, H=200 µm, L=500 µm)
