A New Clean Hydrogen-Catalytic-Thermoelectric Power Generator: Manufacture, Measurement and Simulation

• Main Authors: Ray-wen Chang, 張瑞文
• Other Authors: Shenqyang (Steven) Shy
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/57180256290905868127

碩士 === 國立中央大學 === 機械工程研究所 === 96 === This thesis uses hydrogen as a fuel and combines three clean energy-saving technologies, including heat-recirculating, catalytic reaction, and thermoelectric conversion techniques, to innovate and devise a portable thermoelectric generator (TEG) with zero CO2, CO and NOx emissions. The TEG has three key components: (1) the Swiss-roll catalytic heat source (SRCHS), (2) the thermoelectric module (TEM), (3) and heat sink (HSi), which are sequentially sandwiched. Three SRCHSs of the same size (50 × 50 × 10 mm) but using different materials including copper (Cu), stainless steel (S304), and ceramic (B85) with corresponding thermal conductivities 385, 26, and 0.38 Wm-2K-1 are manufactured by the CNC machine. All three SRCHSs have 1.5-turn Swiss-roll reactant and product channels having 4×4 mm2 cross-sectional areas. A 5-mm long platinum honeycomb catalyst is placed on the entrance reactant channel to produce heat via surface reaction when H2/air premixtures are flowing through the Pt honeycomb catalyst even at room temperature. Because SRCHS has heat-recirculating characteristics, it can provide uniform heat source to TEM together with different heat exchange designs of HSi and thus the wanted temperature gradient across the TEM can be stably controlled. The TEM material is Bismuth Telluride (Bi2Te3) and its maximum operation temperature is 400oC. In addition, the effect of different loading pressure to the power density output of the TEG system is measured and discussed. For experimental measurements, we use 10 K-type thermocouples along the SRCHS channel and in front of the Pt honeycomb catalyst and behind to measure temperature distributions as a function of time in the SRCHS. Three cement-on thermocouples are used to measure surface temperatures on the top area of the SRCHS. The hydrogen concentration in volume percentage varying from [H2] = 6% to [H2] = 13% is applied with a wide range of the flow Reynolds number (Re = VfDv-1) varying from 500 to 3000, where Vf is the reactant velocity, D is the width of the channel, and v is the kinematics viscosity of the reactant. Moreover, emission of [H2], [O2], [NOx] and more are measured by the gas analyzer. For numerical Simulations, a 3D model is established using CFD-RC package combined with 13 platinum surface reaction mechanisms with the consideration of heat losses to predict chemical reacting flows in the SRCHS. Numerical predications are in consistent with experimental measurements. It is found that the B85 SRCHS with very small thermal conductivity has the maximum heat recirculation among three SRCHSs, using [H2] = 12% and Re = 2,000 in the SRCHS, applying the water-cooling HSi, and adding a pressure load of 200 psi to the TEG system, the temperature difference across the TEM can be controlled at 200 oC, yielding the best power performance with a power density as high as 540 mW/cm2. This novel portable TEG is free of CO2 and NOx, which is a new clean energy technology and can used for many small electrical devices.