An Experimental and Theoretical Investigation Into Thermally Governed Transient Flow Surges in Two-Phase Condensing Flow

1977 ◽  
Vol 99 (4) ◽  
pp. 561-567 ◽  
Author(s):  
G. L. Wedekind ◽  
B. L. Bhatt
Keyword(s):  
Experimental Data ◽  
Transient Flow ◽  
Vapor Flow ◽  
Transient Phenomenon ◽  
Two Phase ◽  
Subcooled Liquid ◽  
Measured Flow ◽  
Tube Type ◽  
Complete Condensation ◽  
Small Change

The specific transient phenomenon under consideration is the outlet flowrate of subcooled liquid from a tube-type condenser where complete condensation takes place. Experimental data are presented which indicates that a small change in the inlet vapor flow-rate will momentarily cause a very large transient surge in the outlet flowrate of subcooled liquid. These experimentally measured flow transients are predicted quite accurately using a system mean void fraction model. Also, some preliminary results are presented which indicate the influence of throttling at the condenser outlet as a means of attenuating the transient overshoot characteristics.

An Investigation Into the Effect of Subcooled Liquid Inertia on Flowrate Induced Transient Flow Surges in Horizontal Condensing Flow Systems

2003 ◽  
Author(s):  
Chris J. Kobus
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Transient Flow ◽  
Salient Feature ◽  
Analytical Tool ◽  
Predictive Capability ◽  
Subcooled Liquid ◽  
Flow Systems ◽  
Tube Type ◽  
Complete Condensation

The objective of this research is to investigate large-scale transient flow surges of condensate leaving horizontal in-tube condensing flow systems, due to perturbations in the inlet vapor flowrate, and the influence of the subcooled condensate inertia on these surges. In a tube-type condenser involving complete condensation, it has been seen that small changes in the inlet vapor flowrate momentarily cause large transient flow surges in the outlet liquid flowrate. A System Mean Void Fraction (SMVF) Model is developed for predicting these flow surge characteristics. Experimental data are also presented, showing both the influence of subcooled liquid inertia, and the very good predictive capability of the SMVF Model. The salient feature of the SMVF Model is its simplicity that, with an experimentally verified predictive capability, enhances the models’ utility as an analytical tool as well as a tool for educational purposes.

An Investigation Into the Effect of Subcooled Liquid Inertia on Flow-Change-Induced Transient Flow Surges in Horizontal Condensing Flow Systems

2005 ◽  
Vol 127 (11) ◽  
pp. 1280-1284 ◽  
Author(s):  
C. J. Kobus
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Transient Flow ◽  
Phase Region ◽  
Complex Nature ◽  
Vapor Flow ◽  
Two Phase ◽  
Subcooled Liquid ◽  
Flow Systems ◽  
Final Steady State

The objective of this research is to investigate large-scale transient flow surges of the condensate leaving in-tube condensing flow systems because of perturbations in the inlet vapor flow rate, and the influence of the subcooled liquid inertia of the condensate on these transient responses. Small changes in the inlet vapor flow rate momentarily cause large transient flow surges in the outlet liquid flow rate. Condensate inertia is seen to destabilize the system into an underdamped behavior where the flow rate can overshoot the final steady-state position several times. A one-dimensional, two-fluid, distributed parameter system mean void fraction (SMVF) model of the time-dependent distribution of liquid and vapor within the two-phase region is developed for predicting these transient characteristics, which it is seen to do quite well, especially when consideration is given to the complex nature of the problem.

Modeling the Thermally Governed Transient Flow Surges in Multitube Condensing Flow Systems With Thermal and Flow Distribution Asymmetry

1989 ◽  
Vol 111 (3) ◽  
pp. 786-791 ◽  
Author(s):  
G. L. Wedekind ◽  
B. L. Bhatt
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Liquid Flow Rate ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Tube Model ◽  
Condenser Tube ◽  
Tube System ◽  
Tube Type ◽  
Complete Condensation

In a tube-type condenser involving complete condensation, small changes in the inlet vapor flow rate momentarily cause very large transient surges in the outlet liquid flow rate. An equivalent single-tube model is proposed that predicts these transient flow surges for a multitube system. The model, based upon a system mean void fraction model developed earlier, includes the effects of thermal and flow distribution asymmetry associated with each individual condenser tube in the multitube system. Theoretical and experimental verification for a two-tube system is presented.

Transient and Frequency Response Characteristics of Two-Phase Condensing Flows: With and without Compressibility

1980 ◽  
Vol 102 (3) ◽  
pp. 495-500 ◽  
Author(s):  
B. L. Bhatt ◽  
G. L. Wedekind
Keyword(s):  
Experimental Data ◽  
Two Phase ◽  
Response Characteristics ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Condensing Flows ◽  
Flux Model ◽  
Tube Type ◽  
Complete Condensation ◽  
Compressibility Effects

In a tube-type condenser, involving complete condensation, small changes in the inlet vapor flowrate momentarily cause very large transient surges in the outlet liquid flowrate. Experimental data are presented which indicate that compressibility effects tend to attenuate the amplitude of these flow surges. The system mean void fraction model was extended to include compressibility effects and its predictions are shown to agree well with experimental data. The model is further extended to predict the response characteristics to an oscillatory inlet flowrate and compared with predictions based upon the drift-flux model.

Modeling the Characteristics of Thermally Governed Transient Flow Surges in Multitube Two-Phase Condensing Flow Systems With Compressibility and Thermal and Flow Distribution Asymmetry

1997 ◽  
Vol 119 (3) ◽  
pp. 534-543 ◽  
Author(s):  
G. L. Wedekind ◽  
C. J. Kobus ◽  
B. L Bhatt
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Physical Mechanisms ◽  
Tube Type ◽  
Design Perspective ◽  
Spreadsheet Software

In a tube-type condenser involving complete condensation, small changes in the inlet vapor flow rate momentarily cause very large transient surges in the outlet mass flow rate. An Equivalent Single-Tube Model (ESTM), based on the System Mean Void Fraction Model, is developed that predicts these transient flow surges for a multitube system; including the effects of compressibility as well as thermal and flow distribution asymmetry. The model is verified theoretical and experimentally. From a design perspective, the significant value of the ESTM is that it includes the primary physical mechanisms involved in such complex flow transients, yet is simple enough to be solved on typical “spreadsheet” software.

Complete Transient Two-Dimensional Analysis of Two-Phase Closed Thermosyphons Including the Falling Condensate Film

1994 ◽  
Vol 116 (2) ◽  
pp. 418-426 ◽  
Author(s):  
C. Harley ◽  
A. Faghri
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Conjugate Heat Transfer ◽  
Pipe Wall ◽  
Vapor Flow ◽  
Two Dimensional ◽  
Type Solution ◽  
Two Phase ◽  
Condensate Film ◽  
Good Agreement

A transient two-dimensional thermosyphon model is presented that accounts for conjugate heat transfer through the wall and the falling condensate film. The complete transient two-dimensional conservation equations are solved for the vapor flow and pipe wall, and the liquid film is modeled using a quasi-steady Nusselt-type solution. The model is verified by comparison with existing experimental data for a low-temperature thermosyphon with good agreement. A typical high-temperature thermosyphon was then simulated to examine the effects of vapor compressibility and conjugate heat transfer.

Validation of a Hybrid Surface Renewal Theory Based HTC Model for the Simulation of Condensation Induced Water Hammer

2013 ◽  
Author(s):  
Sabin Cristian Ceuca ◽  
Rafael Macián-Juan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Hybrid Approach ◽  
Phase Interface ◽  
Renewal Theory ◽  
Two Phase ◽  
Surface Renewal ◽  
Subcooled Liquid ◽  
The Individual ◽  
Renewal Period

A hybrid Heat Transfer Coefficient (HTC) model has been developed based on the Surface Renewal Theory and implemented into a system code. The model accounts for both large and small eddies for the removal of heat from the two-phase interface towards the subcooled liquid bulk. The hybrid approach for the calculation of the Surface Renewal Period will increase the applicability region of the individual Surface Renewal Theory (SRT) based HTC for various flow regimes. Validation of the new Hybrid HTC model is performed against experimental data.

Complete Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

1999 ◽  
Vol 121 (4) ◽  
pp. 904-915 ◽  
Author(s):  
E. Begg ◽  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Two Phase Flow ◽  
Film Condensation ◽  
Vapor Flow ◽  
Pressure Jump ◽  
Phase Flow ◽  
Two Phase ◽  
Vapor Interface ◽  
Complete Condensation ◽  
Annular Film ◽  
Liquid Vapor

A physical and mathematical model of annular film condensation in a miniature tube has been developed. In the model the liquid flow has been coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and the length of the two-phase flow region. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads. Observations from a flow visualization experiment of water vapor condensing in a horizontal glass tube confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in small diameter (d < 3.5 mm) circular tubes.

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