Vapor Quality Sensor (2P)

Measure vapor fraction in two-phase fluids

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Libraries:
Simscape / Foundation Library / Two-Phase Fluid / Sensors

Description

The Vapor Quality Sensor (2P) block measures the fraction of vapor in a two-phase fluid. That fraction can be expressed on a mass basis (the vapor quality of the fluid) or on a volume basis (the vapor void fraction). Use the Vapor fraction specification block parameter to specify the basis.

The block measures the vapor quality at port A and reports it as a physical signal at port X. The physical signal value can range from 0 in pure liquid to 1 in pure vapor. Intermediate values correspond to two-phase mixtures. The sensor is ideal, that is, neither mass nor energy exchanges take place.

If the pressure rises above the critical point for the fluid, vapor and liquid cease to exist, and the measurement becomes undefined. The block then outputs -1, a value that serves to indicate a critical or supercritical state.

Examples

Fluid Vaporization in Pipe

Model the vaporization of water to generate steam. Liquid water enters the pipe at 370 K at a rate of 1 kg/s. The pipe is heated to 1000 K, causing the water flowing inside pipe to saturate.

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Two-Phase Fluid Refrigeration

Models a vapor-compression refrigeration cycle using two-phase fluid components. The compressor drives the R-134a refrigerant through a condenser, an expansion valve, and an evaporator. The hot gas leaving the compressor condenses in the condenser via heat transfer to the environment. The pressure drops as the refrigerant passes through the expansion valve. The drop in pressure lowers the saturation temperature of the refrigerant. This enables it to boil in the evaporator as it absorbs heat from the refrigerator compartment. The refrigerant then returns to the compressor to repeat the cycle. The controller turns the compressor on and off to maintain the refrigerator compartment temperature within a band around the desired temperature.

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Ports

Output

X — Vapor quality, unitless

physical signal

Physical signal output port for measuring the fraction of vapor in a two-phase fluid. Use the Vapor fraction specification parameter to select the type of measurement.

Conserving

A — Sensor inlet

two-phase fluid

Two-phase fluid conserving port. Connect this port to the node in the two-phase fluid network where you want to measure the vapor quality.

Parameters

Vapor fraction specification — Whether to express vapor fraction on a mass basis or on a volume basis

Vapor quality (default) | Vapor void fraction

Type of measurement to report at port X. Select Vapor quality for the mass fraction of vapor in a two-phase fluid. Select Vapor void fraction for the volume fraction instead. The measurement can range from 0 to 1 in both cases. For critical and supercritical fluids, the output is -1.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018b