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Liu A.,Key Laboratory for Power Machinery and Engineering | Weng Y.,Key Laboratory for Power Machinery and Engineering
Journal of Power Sources | Year: 2010

This paper presents the work on the design and part-load operations of a hybrid power system composed of a pressurized molten carbonate fuel cell (MCFC) and a micro-gas turbine (MGT). The gas turbine is an existing one and the MCFC is assumed to be newly designed for the hybrid system. Firstly, the MCFC power and total system power are determined based on the existing micro-gas turbine according to the appropriate MCFC operating temperature. The characteristics of hybrid system on design point are shown. And then different control methods are applied to the hybrid system for the part-load operation. The effect of different control methods is analyzed and compared in order to find the optimal control strategy for the system. The results show that the performance of hybrid system during part-load operation varies significantly with different control methods. The system has the best efficiency when using variable rotational speed control for the part-load operation. At this time both the turbine inlet temperature and cell operating temperature are close to the design value, but the compressor would cross the surge line when the shaft speed is less than 70% of the design shaft speed. For the gas turbine it is difficult to obtain the original power due to the higher pressure loss between compressor and turbine. © 2009 Elsevier B.V. All rights reserved. Source


Chen G.,Key Laboratory for Power Machinery and Engineering | Quan X.,Key Laboratory for Power Machinery and Engineering | Cheng P.,Key Laboratory for Power Machinery and Engineering
International Journal of Heat and Mass Transfer | Year: 2010

An experimental investigation has been carried out to study effects of surfactant additive on microscale boiling under pulse heating over a Pt microheater (140 × 100 μm2) fabricated in a trapezoidal microchannel (600 μm in width and 150 μm in depth). Experiments are carried out for six different surfactant concentrations of Triton X-100 ranging from 47 ppm to 2103 ppm, for mass flux in the range from 45 kg/m2 s to 225 kg/m2 s, pulse width in the range from 50 μs to 2 ms, and heat flux in the range from 3 MW/m2 to 65 MW/m2. As in existing work on pool boiling under steady heating, it is found that nucleate boiling becomes more vigorous and heat transfer is enhanced greatly with the addition of surfactant with maximum boiling heat transfer occurs at the critical micelle concentration (cmc). Furthermore, these maximum values of boiling heat transfer coefficient increase with decreasing pulse width. When concentration is below cmc, the heat flux needed for nucleation increases with increasing concentration and the nucleation temperature is reduced. When concentration is higher than cmc, the boiling heat transfer coefficient decreases and nucleation temperature is higher than that of pure water. © 2009 Elsevier Ltd. All rights reserved. Source


Qu J.,Key Laboratory for Power Machinery and Engineering | Wu H.-y.,Key Laboratory for Power Machinery and Engineering | Cheng P.,Key Laboratory for Power Machinery and Engineering
International Communications in Heat and Mass Transfer | Year: 2010

An experimental investigation was performed on the thermal performance of an oscillating heat pipe (OHP) charged with base water and spherical Al2O3 particles of 56 nm in diameter. The effects of filling ratios, mass fractions of alumina particles, and power inputs on the total thermal resistance of the OHP were investigated. Experimental results showed that the alumina nanofluids significantly improved the thermal performance of the OHP, with an optimal mass fraction of 0.9 wt.% for maximal heat transfer enhancement. Compared with pure water, the maximal thermal resistance was decreased by 0.14 °C/W (or 32.5%) when the power input was 58.8 W at 70% filling ratio and 0.9% mass fraction. By examining the inner wall samples, it was found that the nanoparticle settlement mainly took place at the evaporator. The change of surface condition at the evaporator due to nanoparticle settlement was found to be the major reason for the enhanced thermal performance of the alumina nanofluid-charged OHP. © 2009 Elsevier Ltd. All rights reserved. Source

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