Dryout and Post-Dryout Heat Transfer in Horizontal Evaporator Tubes

水平蒸发管中的干燥和干燥后传热

基本信息

批准号：
09450095
负责人：
YOSHIDA Suguru
金额：
$ 9.02万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Experiments were made on dryout quality and local heat transfer coefficient in the post-dryout region for the flow of boiling refrigerants HFC-134a and HCFC-22 inside horizontal smooth tubes and a horizontal micro-fin tube, and prediction methods were developed for the dryout quality and the heat transfer coefficient.1. Dryout proceeded over a certain quality range at given conditions and, therefore, two dryout qualities were discussed ; the dryout inception quality at which the heat transfer began to deteriorate and the dryout completion quality at which the heat transfer deterioration ended. The characteristics of the dryout inception and completion qualities were clarified, and each of the dryout qualities was classified into three characteristic regimes for the smooth tube and two regimes for the micro-fin tube. Dimensionless correlations of both the qualities were developed for the respective tubes, and they agreed with the measurements within ±0.03 in the absolute values for the smooth tube and within ±0.02 for the micro-fin tube.2. In the post-dryout region of the smooth tube, the two-phase flow pattern is a dispersed one, where the vapor-liquid mixture is not in a thermodynamic equilibrium. A correlation of the actual quality in the thermodynamic nonequilibrium was developed to predict the actual vapor mass flow rate. By the use of the actual vapor flow rate, the tube wall temperature is calculated from the Gnielinski equation assuming the single-phase flow of the vapor only, and then the heat transfer coefficient is determined. The calculated heat transfer coefficient agreed within ±10% with the measured one. The post-dryout heat transfer coefficient in the micro-fin tube can be calculated as a single-phase heat transfer from the Gnielinski equation with an equation of friction factor obtained from the measured pressure drop.

进行了对干燥质量和局部传热系数的实验，以使沸腾的制冷剂HFC-134A和HCFC-22在水平光滑管内部和HCFC-22流动，并开发了水平的微鳍管，并为干燥质量和热传递系数开发了预测方法。1。在给定条件下，干旱在一定质量范围内进行，因此讨论了两种干旱质量。热传递开始确定的干旱构成质量以及热传递结束的干燥完成质量。干旱启动和完成质量的特征得到了认证，并且每个干旱质量都被分为平滑管的三个特征制度，并为微鳍管的两个机制分类。两种质量的无量纲相关性是针对各自的管开发的，并且它们同意平滑管的绝对值±0.03以内的测量值，微纤维管的绝对值和±0.02以内。2。在光滑管的练习后区域中，两相流量模式是分散的，其中蒸气 - 液体混合物不在热力学平衡中。开发了热力学非平衡中实际质量的相关性，以预测实际的蒸气质量流速。通过使用实际蒸气流速，通过仅假定蒸气的单相流，从Gnielinski方程计算了管壁温度，然后确定热传递系数。计算出的传热系数在±10％之内与测量的传热系数一致。微鳍管中的练习后传热系数可以作为从Gnielinski方程的单相热传递来计算，并具有从测量的压降下降获得的摩擦因子方程。