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《工程热物理学报》2020,(6)
为了提高太阳能热发电站的发电效率,提出了耦合空气轮机、汽轮机及热力塔为一体的太阳能发电系统。在该系统中,吸热器吸收的太阳能加热压气机所压缩的高压空气,多余的热量被储存在储热装置中以在无阳光的时候维持电站正常运转。被加热后的高压空气驱动透平后排入余热锅炉产生蒸汽驱动汽轮机,余热锅炉的排气以及冷却汽轮机凝汽器的空气进入热力塔底部驱动风力涡轮。本文建立了该系统的热力学模型并对系统效率作了计算,计算中对水蒸汽动力循环的参数做了优化。计算结果表明,该系统相比传统的太阳能热电站发电效率明显提高,在环境温度为15℃、空气轮机组透平进口温度为700℃、热力塔高度400 m以上时,空气轮机工作在有回热热效率高的工作模式下,系统循环效率超过了50%,该太阳能电站总的能量转换效率将可达到33%。 相似文献
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《工程热物理学报》2015,(12)
本文提出一种基于太阳能驱动生物质气化的新型发电系统,利用塔式定日镜场聚光产生1000~1500 K高温太阳热能驱动生物质进行气化反应,并集成先进燃气-蒸汽联合循环发电系统高效利用气化合成气。对该系统进行了热力学性能分析,结果表明:与常规生物质气化方式相比,通过驱动生物质发生气化反应,不仅将间歇性的太阳能转化为稳定的合成气化学能,并增加了气化合成气的化学能,同时合成气中的H_2和CO的摩尔含量之比在气化温度为1000~1500 K时达到1.65~2.44,有利于直接合成甲醇等清洁液体燃料。在设计工况下,系统的太阳能热功转化效率将达到23.68%,随着气化反应温度的升高,系统的太阳能份额和输出的电功率增大,系统的总热效率和总效率均下降。研究成果将为高效利用我国西部丰富的太阳能与生物质能提供一条有效途径。 相似文献
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基于品位匹配和多能源综合梯级利用的原则,本文提出了低CO2排放的太阳能与化石能源互补发电系统LESOLCC,并对其进行了热力经济性能分析。所提系统以甲醇为燃料,中低温太阳能首先提供甲醇重整反应的反应热,从而转化为富氢合成气的化学能,实现品位提升;其次通过燃烧前对CO2的捕集,实现燃料的清洁燃烧,最终在高效联合循环中实现其热功转换。结果表明:基本工况下,系统当量效率达到55.1%,比投资为833$/kW,发电成本为0.124$/kWh,回收期17年;与相同化石燃料输入及CO2捕集水平的尾气捕集CO2的常规燃气-蒸汽联合循环(CC-Post)相比,发电成本下降了10.1%,充分显示其优越性。 相似文献
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本文提出了一种新型的太阳能与燃料热化学互补的发电系统,集成了太阳能热化学燃料转化过程与固体氧化物燃料电池(SOFC)单元。200~300℃中低温太阳能驱动甲醇热分解反应,将太阳能转化为富氢燃料(H2、CO)的化学能,产生的太阳能燃料用于驱动SOFC燃料电池进行发电,实现了太阳能及甲醇燃料的高效发电利用。同时,采用微型燃气轮机(MGT)对SOFC余热及未反应燃料进行回收,实现动力余热的高效梯级利用,进一步提升了系统的发电效率及能源利用率。设计工况下,系统发电效率达到58.24%,太阳能净发电效率为41.1%。该研究为太阳能和清洁燃料的高效利用提供了新途径。 相似文献
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Periodic orbit theory provides two important functions—the dynamical zeta function and the spectral determinant for the calculation
of dynamical averages in a nonlinear system. Their cycle expansions converge rapidly when the system is uniformly hyperbolic
but greatly slow down in the presence of non-hyperbolicity. We find that the slow convergence can be attributed to singularities
in the natural measure. A properly designed coordinate transformation may remove these singularities and results in a dynamically
conjugate system where fast convergence is restored. The technique is successfully demonstrated on several examples of one-dimensional
maps and some remaining challenges are discussed. 相似文献
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通过对热力学中的卡诺循环、三角形路径的循环以及半圆形路径的循环过程的讨论,探索吸热和放热的位置的转换点,从而正确地计算系统做功、效率等. 相似文献
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Fukuda Y Hayakawa T Inoue K Kasuga S Koshio Y Kumita T Matsumoto K Nakahata M Nakamura K Okumura K Sakai A Shiozawa M Suzuki J Suzuki Y Tomoeda T Totsuka Y Hirata KS Kihara K Oyama Y Koshiba M Nishijima K Horiuchi T Fujita K Hatakeyama S Koga M Maruyama T Suzuki A Mori M Kajimura T Suda T Suzuki AT Ishizuka T Miyano K Okazawa H Hara T Nagashima Y Takita M Yamaguchi T Hayato Y Kaneyuki K Suzuki T Takeuchi Y Tanimori T Tasaka S Ichihara E Miyamoto S Nishikawa K 《Physical review letters》1996,77(9):1683-1686
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Raphael Paul Abdellah Khodja Andreas Fischer Karl Heinz Hoffmann 《Entropy (Basel, Switzerland)》2021,23(12)
Vuilleumier refrigerators are a special type of heat-driven cooling machines. Essentially, they operate by using heat from a hot bath to pump heat from a cold bath to an environment at intermediate temperatures. In addition, some external energy in the form of electricity can be used as an auxiliary driving mechanism. Such refrigerators are, for example, advantageous in situations where waste heat is available and cooling power is needed. Here, the question of how the performance of Vuilleumier refrigerators can be improved is addressed with a particular focus on the piston motion and thus the thermodynamic cycle of the refrigerator. In order to obtain a quantitative estimate of the possible cooling power gain, a special class of piston movements (the AS motion class explained below) is used, which was already used successfully in the context of Stirling engines. We find improvements of the cooling power of more than 15%. 相似文献
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Average Cycle Period in Asymmetrical Flashing Ratchet 总被引:1,自引:0,他引:1
The directed motion of a Brownian particle in a flashing potential
with various transition probabilities and waiting times in one of
two states is studied. An expression for the average cycle period
is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period
τm, which takes the maximum of J, is shifted to a small value when the transition probability λ
from the potential on to the potential off decreases, the maximal
current appears in the case of the average waiting time in the
potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states. 相似文献
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David Sands 《Entropy (Basel, Switzerland)》2021,23(7)
The Carnot cycle and the attendant notions of reversibility and entropy are examined. It is shown how the modern view of these concepts still corresponds to the ideas Clausius laid down in the nineteenth century. As such, they reflect the outmoded idea, current at the time, that heat is motion. It is shown how this view of heat led Clausius to develop the entropy of a body based on the work that could be performed in a reversible process rather than the work that is actually performed in an irreversible process. In consequence, Clausius built into entropy a conflict with energy conservation, which is concerned with actual changes in energy. In this paper, reversibility and irreversibility are investigated by means of a macroscopic formulation of internal mechanisms of damping based on rate equations for the distribution of energy within a gas. It is shown that work processes involving a step change in external pressure, however small, are intrinsically irreversible. However, under idealised conditions of zero damping the gas inside a piston expands and traces out a trajectory through the space of equilibrium states. Therefore, the entropy change due to heat flow from the reservoir matches the entropy change of the equilibrium states. This trajectory can be traced out in reverse as the piston reverses direction, but if the external conditions are adjusted appropriately, the gas can be made to trace out a Carnot cycle in P-V space. The cycle is dynamic as opposed to quasi-static as the piston has kinetic energy equal in difference to the work performed internally and externally. 相似文献
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