04_HEM_web - ENU 4134 Homogeneous Equilibrium Model D....

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ENU 4134 Homogeneous Equilibrium Model D. Schubring Fall 2011 Learning Objectives I 1-c-i Identify the assumptions used in the homogeneous equilibrium model (HEM) and analyze the appropriateness of these assumptions for a two-phase flow of interest (feeds into 5-d ) I 1-c-ii Use the HEM for an estimate of pressure drop (feeds into 5-b ) Homogeneous Equilibrium Model The HEM consists of making the following modeling assumptions: I The average phase velocities, { v k } k and { v k } k are the same (call these v k and v k ). Further, the velocities are assumed uniform within the channel. I The two phases are in thermodynamic equilibrium temperature and pressure. The accuracy of a model is often linked to the accuracy of its assumptions. The second assumption is reasonable for many situations, particularly those with no or fairly low heat transfer. HEM Velocity Assumption The assumption in the HEM regarding velocities is much weaker. The second component uniform velocities in the channel is highly inaccurate. In the development of the HEM pressure drop model, however, single-phase turbulent friction factors are used that limit this effect. The first component of the assumption equal average velocities is a good approximation in certain systems: I Air-particulate transport (dilute pollutants) I Certain types of sprays It is an assumption that can lead to reasonable global results (such as pressure drop) for high pressure, high mass flux ( G m ) flow. For example, at BWR/PWR conditions and a mass flux of 2000 kg m- 2 s- 1 , the HEM can provide as good an estimate of pressure drop as many more complex models. Dynamic Density ( + m ) Under the restrictions of the HEM and constant fluid properties, the brackets arent necessary in the definition of...
View Full Document

This note was uploaded on 10/22/2011 for the course ENU 4134 taught by Professor Schubring during the Fall '11 term at University of Florida.

Page1 / 18

04_HEM_web - ENU 4134 Homogeneous Equilibrium Model D....

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online