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《低温与超导》2021,49(7):84-90
有机朗肯循环(Organic Rankine cycle, ORC)系统是一种回收内燃机余热的有效方案之一,目前受到越来越多的关注。由于内燃机余热形式多样,温度梯度大且存在变温特性,基本有机朗肯循环用于回收内燃机余热有一定难度。本文对内燃机有机朗肯循环系统的相关研究进行了综述,以余热最佳匹配循环为基础,分别从工质和系统结构方面对比分析了超临界ORC,混合工质ORC,双回路ORC和添加额外回路ORC四种方案。采用温熵(T-S)图映射法,根据有机朗肯循环与理想循环的接近度,总结了多种有机朗肯循环系统用于内燃机余热回收的潜力。分析发现在相同的循环系统下,具有较高临界点的工质和有较大的温度滑移的混合工质更有优势,相同工质下,双回路ORC和添加额外回路的ORC是解决内燃机余热波动的合理方案之一。 相似文献
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基于传热窄点研究了固定气体冷却器进出口水温时,高低不同的进水温度、不同的出水温度、排气压力、蒸发温度、过热度以及换热面积对于系统性能的影响。结果表明:随着进出口水温的升高和换热面积的减小,系统COP逐渐减小,并且最优高压压力逐渐升高;随着蒸发温度的升高,系统COP逐渐增加,最优高压压力逐渐升高;增加过热度只会在排气压力较低时提高系统的COP。当处于部分负荷工况时,冷端温差随负荷率的增加而减小;对于气冷器进出口水温温差大的工况,当负荷率小于1时传热窄点会位于换热器中间位置。在负荷率到达1时,传热窄点恰好移动到冷端。当负荷率大于1时,传热窄点一直稳定在冷端;对于气冷器进出口水温温差小的工况,当负荷率小于1时,传热窄点就已经到达冷端,并随着负荷率的增大一直稳定在冷端;部分负荷下的COP总是小于设计负荷下的COP,实际负荷偏离设计负荷越远,系统的COP越小。 相似文献
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《工程热物理学报》2017,(9)
以亚临界有机朗肯简单循环为研究对象,理论分析得到影响系统性能的独立变量:膨胀机进口温度、进口压力、冷凝温度和热源出口温度。当给定冷凝温度且以蒸发器窄点温差为约束变量时,独立变量减少为膨胀机进口温度和进口压力。在此基础上,以耦合低温热源时的系统热效率作为评价指标,对8种常用有机工质的亚临界简单系统性能的变化规律进行分析,得到循环系统全局最优性能的运行参数。结果表明:系统热效率由循环热效率和热源效率共同决定,采用有机工质R236fa、R123和R236ea的循环热效率相对较高;由于热源的耦合作用,采用有机工质R236fa、RC318和R236ea的系统热效率相对较高。 相似文献
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We propose a model for a three-terminal quantum well heat engine with heat leakage. According to the Landauer formula, the expressions for the charge current, the heat current, the power output and the efficiency are derived in the linear-response regime. The curves of the power output and the efficiency versus the positions of energy levels and the bias voltage are plotted by numerical calculation. Moreover, we obtain the maximum power output and the corresponding efficiency, and analyze the influence of the heat leakage factor, the positions of energy levels and the bias voltage on these performance parameters. 相似文献
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Cooling technology is facing new challenges with the increase of electronic equipment power onboard aircraft. The traditional heat sink based on high-altitude bleed air does not satisfy this increase of cooling demands. In this article, an air/air-type skin heat exchanger is studied for cooling aircraft electronic equipment. It uses outside high-altitude cold air rather than bleed air as a heat sink. This cooling technology can effectively remove the heat load of high-power electronic devices without greatly increasing aircraft performance penalty. To assess its high-altitude heat transfer performance, an experimental prototype was designed and made. Some experiments were conducted on a ground experimental test. The heat transfer criteria formulas were obtained for both the side air in the skin heat exchanger and its convective heat transfer coefficients. Based on these experimental analyses, the heat transfer performances of the skin heat exchanger in a high-altitude cruise condition are deduced when it is assumed to be installed at an unfavorable position and a favorable position, separately. This work tries to provide a technical support for its future onboard application. 相似文献
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分离式热管换热器传热特性的实验研究 总被引:1,自引:0,他引:1
本文在自行设计分离式热管实验装置的基础上,对其传热特性进行了实验研究。其工作温度为170~250℃,热流密度为25~50 kW/m~2。蒸发段和冷凝段构成相同,均是由7根直径30 mm的无缝钢管短管束组成,管长为160 mm,带有紧套的钢帛环形肋片结构尺寸为:外径45 mm、厚1 mm、片间距4 mm。实验结果表明,在本实验条件下,分离式热管的最佳充液率按管束总容量计为18%~38%。根据实验结果拟合了最佳充液率(24%)下蒸发段内部平均沸腾换热系数和冷凝段内部凝结换热努塞尔数综合关系式。 相似文献
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Christian Maes Karel Netočný Michel Verschuere 《Journal of statistical physics》2003,111(5-6):1219-1244
We study networks of interacting oscillators, driven at the boundary by heat baths at possibly different temperatures. A set of first elementary questions are discussed concerning the uniqueness of a stationary possibly Gibbsian density and the nature of the entropy production and the local heat currents. We also derive a Carnot efficiency relation for the work that can be extracted from the heat engine. 相似文献
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Schrödinger operators on Sobolev spaces are considered as new solvable models with point interactions. A simple formula for the deficiency indices of a minimal Schrödinger operator with point interactions is given. Examples of point interactions on the space W21(
3) are constructed.Mathematical Subject Classification (2000). 37J10, 47A10 相似文献