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IMPROVED DESIGN METHOD FOR BOILING HEAT TRANSFER IN COMPACT PLATE-FIN HEAT EXCHANGERS.

机译：紧凑的板翅式换热器沸腾换热的改进设计方法。

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摘要

The design technique of interest here is the use of the local assumption, namely that the local heat transfer coefficient during flow boiling is uniquely fixed by the local metal-to-liquid temperature difference and the local fluid velocity. The offset fins of compact heat exchangers give excellent mixing of the boiling liquid, so homogeneous flow is assumed to prevail. A stepwise computation procedure is used to account for the quality change along the heated channel. The objects of this study are first to confirm the proposed design method by a comparison of prediction and data for Freon-113 in a commercial heat exchanger and, secondly, to show the performance of two new compact heat exchangers, specifically designed for boiling duty by this technique. These heat exchangers, from different manufacturers, were brazed aluminum, cross-flow devices having core sizes of about 3 x 3 x 3 in. The equivalent diameter of the flow passage on the boiling side, based on the wetted diameter, was about 1/15 in. Tests were made with Freon-113 at atmospheric pressure in these heat exchangers installed as thermosyphon reboilers. Heat was provided by condensing steam. The Freon measured mass velocity was from 3 to 150 lb/ft('2)s, the inlet velocity was 0.03 to 1.5 ft/s, and the calculated homogeneous exit velocity was 1.6 to 66 ft/s. The calculated metal-to-liquid temperature difference varied from 30 to 215(DEGREES)F, the total pressure drop across the exchanger core on the boiling side was from 0.4 to 2.0 psia, and the total heat duty was from 19,000 to 196,000 Btu/hr. For the two new designs, the agreement between predicted and measured duties was satisfactory as long as no dry-out occurred. When dry-out occurred, flow oscillations (density-wave oscillations) were observed, and the observed heat duty was as much as 30% below the predicted value.
机译：这里感兴趣的设计技术是使用局部假设，即流动沸腾过程中的局部传热系数由局部的金属-液体温度差和局部的流体速度唯一地固定。紧凑型换热器的偏置翅片可很好地混合沸腾的液体，因此，假设流量均匀。使用逐步计算程序来说明沿加热通道的质量变化。本研究的目的是首先通过比较商用换热器中氟利昂113的预测值和数据来确认所提出的设计方法，其次，以展示两种专门为沸腾负荷设计的新型紧凑型换热器的性能。这种技术。这些来自不同制造商的热交换器为铝制铜铝横流装置，其芯尺寸约为3 x 3 x 3英寸。基于湿润直径，沸腾侧流动通道的当量直径约为1 /在装有热虹吸再沸器的这些热交换器中，在大气压下用氟利昂113进行了15英寸的测试。通过冷凝蒸汽提供热量。氟利昂测量的质量速度为3至150 lb / ft（'2）s，入口速度为0.03至1.5 ft / s，计算出的均匀出口速度为1.6至66 ft / s。计算出的金属与液体之间的温差为30至215（度）F，沸腾侧交换器芯上的总压降为0.4至2.0 psia，总热负荷为19,000至196,000 Btu / hr。对于这两种新设计，只要不发生干dry，预计职责与实务之间的协议就令人满意。当发生变干时，观察到流动振荡（密度波振荡），并且观察到的热负荷比预测值低多达30％。

著录项

  • 作者

    CHEN, CHENG-CHUNG.;

  • 作者单位

    University of Illinois at Urbana-Champaign.;

  • 授予单位 University of Illinois at Urbana-Champaign.;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 1983
  • 页码 191 p.
  • 总页数 191
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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