A Framework for the Analysis of Thermal Losses in Reciprocating Compressors and Expanders
A Framework for the Analysis of Thermal Losses in Reciprocating Compressors and Expanders
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DOI：
10.1080/01457632.2014.889460
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发表时间：
2014-02
影响因子：
2.3
通讯作者：
R. Mathie;C. Markides;Alexander J. White
中科院分区：
文献类型：
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作者：
R. Mathie;C. Markides;Alexander J. White
本文提出了一个框架，正式描述了基本的不稳定和共轭的热传递过程中发生的热力学系统，沿着从其应用程序的热力学损失的表征，由于不可逆的热传递在往复压缩和膨胀过程中的气体弹簧的结果。具体而言，提出了一种传热模型，解决了一维不稳定的热传导方程在固体中的同时，在气相中的第一定律，与施加的传热系数采取适当的实验中的气体弹簧。即使在低体积压缩比（2.5）下，也显示出向固体壁的不稳定热传递的显著影响，在中间Péclet数（即，归一化频率），并且对于更常见的材料选择更接近10-12%。通过归因于圆柱壁厚度的共轭变化，固体对这些值的贡献分别约为8%和2%，在中间厚度处显示出最大值。在较高的压缩比（6）下，普通材料的最坏情况损失为19%。这些结果强烈表明，在设计高效率的往复式机器的充分共轭和非定常问题必须考虑和固体的作用，在确定性能不能被忽视，在一般情况下。
This article presents a framework that describes formally the underlying unsteady and conjugate heat transfer processes that are undergone in thermodynamic systems, along with results from its application to the characterization of thermodynamic losses due to irreversible heat transfer during reciprocating compression and expansion processes in a gas spring. Specifically, a heat transfer model is proposed that solves the one-dimensional unsteady heat conduction equation in the solid simultaneously with the first law in the gas phase, with an imposed heat transfer coefficient taken from suitable experiments in gas springs. Even at low volumetric compression ratios (of 2.5), notable effects of unsteady heat transfer to the solid walls are revealed, with thermally induced thermodynamic cycle (work) losses of up to 14% (relative to the work input/output in equivalent adiabatic and reversible compression/expansion processes) at intermediate Péclet numbers (i.e., normalized frequencies) when unfavorable solid and gas materials are selected, and closer to 10–12% for more common material choices. The contribution of the solid toward these values, through the conjugate variations attributed to the thickness of the cylinder wall, is about 8% and 2% points, respectively, showing a maximum at intermediate thicknesses. At higher compression ratios (of 6) a 19% worst-case loss is reported for common materials. These results suggest strongly that in designing high-efficiency reciprocating machines the full conjugate and unsteady problem must be considered and that the role of the solid in determining performance cannot, in general, be neglected.