共查询到20条相似文献,搜索用时 125 毫秒
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推导了双压无再热联合循环余热锅炉的出力与参数的关系 ,阐述了双压无再热联合循环余热锅炉参数优化的目的、方法及步骤。 相似文献
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本文在考虑工质与热源间热阻损失的内可逆卡诺热泵模型基础上,用一常数项表示热源间的热漏,用一带系数项表示循环中除热阻和热漏外的其余所有不可逆性(如摩擦,涡流,非平衡等),建立了一个不可逆定常态能量转换卡诺热泵模型,并对此不可逆热泵模型进行有限时间热力学分析,导出了供热率和供热系数之间的优化关系。由此模型可准确描述各种不可逆性对热泵性能的影响,能对实际热泵的工作性能起到精确的指导作用. 相似文献
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Hanfei Tuo 《国际能源研究杂志》2013,37(8):857-867
A thermal‐economic analysis of a transcritical Rankine power cycle with reheat enhancement using a low‐grade industrial waste heat is presented. Under the identical operating conditions, the reheat cycle is compared to the non‐reheat baseline cycle with respect to the specific net power output, the thermal efficiency, the heat exchanger area, and the total capital costs of the systems. Detailed parametric effects are investigated in order to maximize the cycle performance and minimize the system unit cost per net work output. The main results show that the value of the optimum reheat pressure maximizing the specific net work output is approximately equal to the one that causes the same expansion ratio across each stage turbine. Relative performance improvement by reheat process over the baseline is augmented with an increase of the high pressure but a decrease of the turbine inlet temperature. Enhancement for the specific net work output is more significant than that for the thermal efficiency under each condition, because total heat input is increased in the reheat cycle for the reheat process. The economic analysis reveals that the respective optimal high pressures minimizing the unit heat exchanger area and system cost are much lower than that maximizing the energy performance. The comparative analysis identifies the range of operating conditions when the proposed reheat cycle is more cost effective than the baseline. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The influence of both the quantum degeneracy and the finite rate heat transfer between the working substance and the cylinder wall on the optimal performance of an Otto engine cycle is investigated. Expressions for several important parameters such as the power output and efficiency are derived. By using numerical solutions, the curves of the power output and efficiency varying with the compression ratio of two isochoric processes are presented. It is found that there are optimal values of the compression ratio at which the power output and efficiency attain their maximum. In particular, the optimal performance of the cycle in strong and weak gas degeneracy and the high temperature limit are discussed in detail. The distinctions and connections between the quantum Otto engine and the classical are revealed. Moreover, the maximum power output and efficiency and the corresponding relevant parameters are calculated, and consequently, the optimization criteria of some important parameters such as the power output, efficiency and compression ratio of the working substance are obtained. 相似文献
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《Applied Thermal Engineering》2007,27(11-12):2051-2058
An irreversible cycle model of the Miller heat engine is established, in which the multi-irreversibilities coming from the adiabatic compression and expansion processes, finite time processes and heat leak loss through the cylinder wall are taken into account. The power output and efficiency of the cycle are optimized with respect to the pressure ratio of the working substance. The optimum criteria of some important parameters such as the power output, efficiency and pressure ratio are given. The influence of some relevant design parameters is discussed. Moreover, it is expounded that the Otto and the Atkinson heat engines may be taken as two special cases of the Miller heat engine and that the optimal performance of the two heat engines may be directly derived from that of the Miller heat engine. 相似文献
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A cyclic model of an irreversible Diesel heat engine is presented, in which the heat loss between the working fluid and the
ambient during combustion, the irreversibility inside the cyclic working fluid resulting from friction, eddies flow, and other
irreversible effects are taken into account. By using the thermodynamic analysis and optimal control theory methods, the analytical
expressions of power output and efficiency of the Diesel heat engine are derived. Variations of the main performance parameters
with the pressure ratio of the cycle are analyzed and calculated. The optimum operating region of the heat engine is determined.
Moreover, the optimum criterion of some important parameters, such as the power output, efficiency, pressure ratio, and temperatures
of the working fluid at the related state points are illustrated and discussed. The conclusions obtained in the present paper
may provide some theoretical guidance for the optimal parameter design of a class of internal-combustion engines. 相似文献
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《International Journal of Thermal Sciences》2007,46(6):605-613
An irreversible Dual heat engine model, which can include the Otto and Diesel cycles, is established and used to investigate the influence of the multi-irreversibilities mainly resulting from the adiabatic processes, finite time processes and heat leak loss through the cylinder wall on the performance of the cycle. The power output and efficiency of the cycle are derived and optimized with respect to the pressure ratio of the working substance. The maximum power output and efficiency are calculated. The influence of the various design parameters on the performance of the cycle is analyzed. The optimum criteria of some important parameters such as the power output, efficiency and pressure ratio are given. Several special interesting cases are discussed. The results obtained are general, so that the optimal performance of irreversible Otto and Diesel cycles are included in two special cases of the Dual cycle and may be directly derived from that of the Dual heat engine. Moreover, the performance characteristic curves of the three heat engines are presented by using numerical examples. 相似文献
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《能源学会志》2014,87(1):69-80
By using quantum master equation, semi-group approach and finite time thermodynamics (FTT), this paper derives the expressions of cycle period, power and efficiency of an irreversible quantum Carnot heat engine with irreversibilities of heat resistance, internal friction and bypass heat leakage, and provides detailed numerical examples. The irreversible quantum Carnot heat engine uses working medium consisting of many non-interacting spin-1/2 systems and its cycle is composed of two isothermal processes and two irreversible adiabatic processes. The optimal performance of the quantum heat engine at high temperature limit is deduced and analyzed by numerical examples. Effects of internal friction and bypass heat leakage on the optimal performance are discussed. The endoreversible case, frictionless case and the case without bypass heat leakage are also briefly discussed. 相似文献
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The performance of an irreversible Carnot heat engine cycle is analysed and optimized by using the theory of finite time thermodynamics based on Agrawal's [2009. A finite speed Curzon-Ahlborn engine. European Journal of Physics, 30 (3), 587–592] model of finite piston speed on the four branches and Petrescu et al.’s [2002b. Optimization of the irreversible Carnot cycle engine for maximum efficiency and maximum power through use of finite speed thermodynamic analysis. In: Proceedings of ECOS’2002, 3–5 July, Berlin, Germany, Vol. II, 1361–1368] model of a Carnot cycle engine with the finite rate of heat transfer, heat leakage from heat source to heat sink and irreversibilities caused by finite speed, friction and throttling through the valves. The finite piston speeds on the four branches are further assumed to be different, which is different from the model of constant speed of the piston on the four branches. Expressions of power output and thermal efficiency of the cycle are derived for a fixed cycle period and internal entropy generation rate. Numerical examples show that the curve of power output versus thermal efficiency is loop shaped, and there exist optimal finite piston speeds on the four branches which lead to the maximum power output and maximum thermal efficiency, respectively. The effects of the heat leakage coefficient and internal entropy generation rate on the optimal finite piston speed ratios are discussed. 相似文献
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An optimal performance analysis for an equivalent Carnot-like cycle heat engine of a parabolic-trough direct-steam-generation solar driven Rankine cycle power plant at maximum power and maximum power density conditions is performed. Simultaneous radiation-convection and only radiation heat transfer mechanisms from solar concentrating collector, which is the high temperature thermal reservoir, are considered separately. Heat rejection to the low temperature thermal reservoir is assumed to be convection dominated. Irreversibilities are taken into account through the finite-rate heat transfer between the fixed temperature thermal reservoirs and the internally reversible heat engine. Comparisons proved that the performance of a solar driven Carnot-like heat engine at maximum power density conditions, which receives thermal energy by either radiation-convection or only radiation heat transfer mechanism and rejects its unavailable portion to surroundings by convective heat transfer through heat exchangers, has the characteristics of (1) a solar driven Carnot heat engine at maximum power conditions, having radiation heat transfer at high and convective heat transfer at low temperature heat exchangers respectively, as the allocation parameter takes small values, and of (2) a Carnot heat engine at maximum power density conditions, having convective heat transfer at both heat exchangers, as the allocation parameter takes large values. Comprehensive discussions on the effect of heat transfer mechanisms are provided. 相似文献