Abstract

Understanding the thermodynamic properties of steam at critical flow conditions is important to the design, operation and management of steam distribution network and hence the cost of production in steam-enhanced recovery projects. Using the homogeneous equilibrium model, the properties of steam at critical flow properties of steam at critical flow conditions are presented. These properties include critical velocity, critical pressure, critical temperature, critical pressure, critical temperature, critical steam quality, critical specific volume, critical steam flux and Napier's parameter. The critical velocity, Napier's parameter and the dimensionless form of other properties are shown to be functions of the properties are shown to be functions of the stagnation steam quality. The steam pressure is shown to have a slight effect on pressure is shown to have a slight effect on some of the properties. Empirical correlations for these properties are established for selected operating ranges and experimental results are presented to verify the model's predictions.

Introduction

In steam-enhanced oil recovery operations, the flow rate of steam is usually controlled by a flow-rate controlling device. Flow restrictions, such as nozzles, venturi, chokes and valves can be used to maintain a constant flow rate when the flow through such restrictions is under critical flow conditions. Critical flow refers to a situation where any change in the downstream pressure of the flow fails to induce a pressure of the flow fails to induce a corresponding change to accelerate the mass flow rate. In other words, critical flow is a phenomenon whereby the flow rate has an upper limit for a given set of upstream or stagnation conditions.

Where steam exists as a two-phase fluid, it consists of a saturated liquid and a saturated vapor. In this state, it behaves differently from a single-phase fluid. various models have been proposed to describe the critical flow behaviors of steam. The homogeneous equilibrium model is a simple model that gives a good representation of the critical flow of steam. Results of this model are used in this study. These properties include critical velocity, critical pressure, critical temperature, critical specific volume, critical steam quality and critical steam mass flux.

The critical pressure, critical temperature, critical specific volume, critical steam quality are made dimensionless by dividing each with the corresponding property at the stagnation condition. The critical steam flux is made dimensionless using dimensionless critical steam flux and a new parameter, Napier's parameter, is introduced parameter, Napier's parameter, is introduced as a correlation parameter for the critical flow of steam.

These properties are plotted as a function of the stagnation steam quality using the steam pressure as a parameter. Their results are discussed and empirical correlations of these properties are established for selected operating ranges. Experimental results are presented to compare the critical pressure ratio, the dimensionless critical steam flux and Napier's parameter with the predictions of the homogenous equilibrium model.

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