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A STUDY OF FLASHING PHENOMENA UNDER RAPID DEORESSURIZATION

快速减压下闪蒸现象的研究

基本信息

批准号：
60460105
负责人：
HANAOKA Yutaka
金额：
$ 2.37万
依托单位：
MURORAN INSTOTUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

项目摘要

The purpose of this project is to clarify the thermodynamical criterion associeted with the inception of vaporization of liquid, so-called the flashing phenomena , and to predict the time history in pressure and temperature of vapor-liquid phase within a vessel under the rapid depressurization.Experiments have been performed with a R-113 by the quick openning of solenoid valve. Behaviors of boiling process of liquid have been made use of photographic observation , and each of their temperature and pressure transients have been recorded by quantative measuring systems using thermocouples and piezoelectric tranducer.The results are summarized as follows;(1) Most of vapor-liquid pressure transients after the rapid openning the valve has been characterized by the sudden exponential-like pressure drops, and the successive pressure rise caused by the explosive vaporization of liquid under the appropiriate undershoot,Hich correspods to the difference in pressure between the lower limit and initial saturated condition of superheated liquid.Although many of flashing process has been initiated from the upper region near a liquid surface to the bottom of reservoir, they have been observed there exists three type patterns of the pressure transients according to the effectiveness of the dependence of both vapor-liquid and solid-liquid interfaces on their thermophysical properties.(2) The heterogeneous nucleation theory that Alamgir and Lienhard have succesfully dealed with, is improved for the case of relatively reduced depressurization rate of this study. In the developed theory,that is, an initial depression process is approximated by an exponential function which is caracterized by non-equilibirium pressure relaxation time <gamma> . It has been found that this relaxation time affects strongly on the thermodynamical condition associeted with the inception of bubble generation, which is estimated Gb Number 34-40.

本项目的目的是澄清与液体汽化开始有关的热力学判据，即所谓的闪蒸现象，并预测在快速降压下容器内气液相的压力和温度的时程。用R-113型电磁阀进行了快速开启实验。用照相法观察了液体沸腾过程的行为，用热电偶和压电传感器定量测量系统记录了每一次沸腾过程的温度和压力瞬态。结果总结如下：(1)阀门快速开启后的汽液压力瞬态大部分表现为突然的指数型压降，在适当的欠冲下，由于液体的爆炸性汽化导致压力连续上升，high对应过热液体的下限与初始饱和状态之间的压力差。虽然许多闪蒸过程是从靠近液面上部区域到储层底部开始的，但根据气液界面和固液界面对其热物性的依赖性的有效性，观察到它们存在三种类型的压力瞬变模式。(2)针对本研究降压速率相对较低的情况，对Alamgir和Lienhard成功处理的非均相成核理论进行了改进。在已发展的理论中，即初始降压过程近似为一个指数函数，其特征是非平衡压力松弛时间<gamma>。研究发现，这种弛豫时间对气泡产生的热力学条件有强烈的影响，气泡产生的热力学条件估计为Gb数34-40。