Water Inlet Velocity Research Articles

Analysis of the thermal performance of a church window steam condenser for different operational conditions using three models

The results of the usual design model “Standards for Steam Surface Condensers (SSSC)” and those of a two-dimensional model (2D) and a three-dimensional model (3D) are presented. Both the 2D model and the 3D model allow the presence of non-condensable gases, the pressure drop across the tube bundle and the tube arrangement to be taken into account, while the SSSC model does not. In order to study the thermal performance of the models, the heat transfer rate and the condensate mass flow rate were analysed varying the circulating water inlet temperature and velocity, as well as the fouling inside the tubes. The 2D and 3D models behave similarly to the SSSC model, but present less dependence on temperature and velocity variations. Because of the low running time, both the SSSC and the 2D models are adequate for on-line fouling evaluation of the condenser, the latter affording a more detailed description of the condenser. The SSSC model and the 3D model can complement one another in the design stage, using the SSSC for the area estimation and improving the inner condenser geometry by means of the 3D model.

Examination of interfacial shape and onset of slugging of a stratified flow at a combining Y-junction

Abstract The interface profile and the pressure distribution of a stratified flow and the critical conditions for slug formation at a combining Y-junction are examined experimentally. Air flows through the nearly horizontal channel, and water is introduced into the airstream through the bottom slit. The water-layer thickness and the pressure distribution along the upper wall of the main channel are measured. The critical air velocities for the slug formation are also measured for a range of water-inlet velocity conditions. The effects of the air–water-inlet velocities, the channel inclination angle, and the water-injection angle are studied in this experiment. Basically, the water layer shows a peak near the merging point and then approaches to an equilibrium level far downstream. At the larger water-injection angle, another water-layer peak is observed slightly downstream of the primary peak. The pressure drops sharply near the merging point because of the acceleration of the air flow and then gradually rises up to a certain level at the downstream where the pressure rise by the air flow deceleration and the pressure drop by the friction are balanced. The slugging occurs when the air velocity exceeds an interfacial instability condition. The critical air velocity decreases with the increase of the water-injection angle or the water-inlet velocity. An empirical criterion for slugging at a combining Y-junction is also proposed.

118 流動励起自励スロッシングにおける噴流挙動の可視化

A self-induced sloshing caused by an upward plane jet was recently discovered in a rectangular test tank. The submerged jet entered the tank from an inlet at the bottom center and impinged vertically on a free surface. Under a certain water depth and inlet velocity condition, the first mode sloshing was observed. At the sloshing, the visualized jet streakline had a peculiar oscillatory behavior. Based on the observation, a relation-between the sloshing period and a time was noticed, which was required for the jet fluctuation to travel from the inlet to the surface. As a result, the sloshing was found to occur when the traveling time of the jet fluctuation was about discrete constant times as long as the sloshing period.

Experimental Study on Self-Excited Vibration Characteristics of a Flexible Weir due to Fluid Discharge.

This paper deals with the characteristics of unstable self-excited vibrations of a rectangular, flexible weir installed in a tank, over which water in the upstream tank discharges into the down-stream one. Experiments were carried out for measuring the vibrational strains of the weir, and the oscillation of the water surface in the up-stream tank with changing inlet velocity of water and discharge height. We examined the vibration characteristics of the weir with changing tank ratio (defined as the down stream tank length/the upstream tank length), and found that the occurrence of unstable vibration depends strongly on the tank ratio. The phase relations of the weir vibration to the upstream tank water oscillation were experimentally investigated.

Experimental Study of Self-Excited Vibrations of a Flexible Weir due to Fluid Discharge

This paper deals with the characteristics of unstable self-excited vibrations of a rectangular, flexible weir installed between two tanks, over which the water in the upper tank discharges into the lower one. Experiments were done for measuring vibrational strains of the weir, oscillation of the overflow water thickness, and the oscillations of the water surface in the upper and lower tanks with changing inlet velocity of water into the upper tank and water discharge height. Four unstable vibration modes were found in our experiments. The 1st unstable vibration mode was sloshing-dominated weir vibration and its vibration frequency was almost equal to the sloshing one for the lower tank. The 2nd one was a high frequency vibration of the weir unrelated to the sloshing oscillation and the 3rd one was a torsional one of the weir with a high frequency different from the 2nd one. The 4th mode was peculiar to the experimental system due mostly to the coupling between the inlet water jet and the weir The phase relations between the weir vibration and overflow water thickness were experimentally investigated.

Theoretical study of flow instability of a sodium-heated steam generator

A representation of a sodium-heated steam generator was formulated to study density-wave oscillation of the flow. The mathematical model, presented (designated SGEX code), facilitates prediction of flow instability by examining movements of unstable eigenvalues of the system matrix. It was defined from the trajectory of the system on the pressure loss and inlet water velocity plane when dynamic instability occurred during the flow instability test of the 1 MW (th) sodium-heated s steam generator in OHARAI. Inception of flow instability may be attributed to a large pressure loss in the superheated region, caused by increase in sodium flow rate and inlet temperature and decrease in feedwater flow rate.

Linear analytical model describing the frequency response and stability behavior of a boiling light water reactor

A linear, one-dimensional, one-channel model will be presented which gives an analytical description of the frequency response and stability behavior of a boiling light water reactor or loop (both under forced or natural circulation, pressure-controlled or pressure-varying conditions) with respect to pertubations in reactivity (or heating power), primary steam flow (or system pressure), water inlet velocity or subcooling. Based on this model the computer code ADYSMO could be established. In order to demonstrate the validity and efficiency of this model transfer functions being measured at different boiling water loops and reactors under different experimental conditions had been compared with corresponding ADYSMO calculations.

沸騰水型原子炉におけるボイド反応度の応答

In order to analyze void reactivity response caused by disturbances of inlet water velocity, inlet water temperature, system pressure and reactor power, the “Void Equation” is derived from the fundamental equations of mass and energy conservation and the assumption of “Slip Ratio”. This Void Equation is expressed as∂f/∂t+U∂f/∂z=qwhere f: void volume fraction, t: time, z: length along a channel, U: “void transmission velocity” and q: effective heat source including the effect of system pressure change.“Negative Void” is introduced to treat reactivity response caused by water temperature change in the subcooled region in the same manner as in the boiling region.This void equation is applied to analyze kinetic behavior of a typical power reactor and its numerical solution is obtained with HIPAC-101 (Hitachi Parametron Digital Computer) and IBM-650. The linearized void equation is also derived and the void reactivity response diagram is obtained instead of the ordinary one using the “void map”.

Steam Slip—Theoretical Prediction From Momentum Model

Theoretical equations governing slip effects in forced circulation of boiling water are derived. The equations indicate that steam slip is dependent upon channel geometry, inlet water velocity, and rate of heat addition. A simplified momentum model is postulated which leads to equal friction and head losses of two phases. The model gives good agreement with available experimental results in horizontal and vertical test sections with and without heat addition at pressures from 12 to 2000 psia. Discussion of the model in terms of nonquasi steady-state unbalances of friction and head losses of the two phases explains experimental deviations from the predictions and the previously noted effects of water inlet velocity. It also gives trends for the effects of channel geometry and rate of heat addition. Application of the simplified model to calculating two-phase pressure drops is included.