JPH0227220A - Differential pressure type steam flowmeter - Google Patents

Abstract

PURPOSE:To enable measurement of a correct steam flow rate with a dryness correction by detecting a steam dryness on the primary side of a throttle mechanism to measure a steam flow rate from a primary side pressure, a differential pressure and the dryness. CONSTITUTION:A throttle mechanism 2 is provided in the course of a steam piping 1. A primary side 3 and a secondary side 4 of the throttle mechanism 2 are connected to a flowmeter 7 respectively through lead piping 5 and 6. A pressure sensor 8 is mounted to detect a pressure on the primary side 3 and a dryness sensor 9 to detect a dryness of a steam on the primary side 3. Detection signals from both the sensors 8 and 9 are inputted into the flowmeter 7 through signal lines 10 and 11. The dryness sensor 9 injects a wet steam into a measuring container 14 equipped with a temperature sensor 15 and a pressure sensor 16 through an orifice 12 to make it overheat by an adiabatic expansion thereof and signals from the temperature sensor 15 and the pressure sensor 16 are inputted into an arithmetic device 17 to measure the dryness from mollier diagram, saturated steam chart or a overheating steam chart stored previously. A steam flow rate is computed with a correction by the dryness thus obtained, thereby enabling accurate measurement of the steam flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a differential pressure system in which a restriction mechanism such as a nozzle, venturi, orifice is provided in a steam pipe, and the flow rate is measured from the differential pressure generated between the upstream and downstream parts. This invention relates to a flow rate measuring device.

Measuring the flow rate of steam flowing through steam piping is useful because it determines the amount of steam consumed by steam-using equipment and provides data for improving the heating efficiency of steam-using equipment.

2. Description of the Related Art A common differential pressure type steam flowmeter will be explained with reference to FIG.

A throttle mechanism 22 is provided in the middle of the steam pipe 21.

The primary side 23 and secondary side 24 of the throttle mechanism 22 are connected to a flow meter 27 via pressure piping 25, 26, respectively. A pressure sensor 28 is attached to detect the pressure on the primary side and inputted to the flow meter 27 via a signal line 30. A flow meter 27 displays the steam flow rate based on the primary side pressure and the differential pressure between the primary side and the secondary side.

Problems to be Solved by the Invention When the steam flowing through the steam pipe is wet steam, its specific weight changes depending on the wetness (dryness). Therefore, in the above method, the flow rate is simply calculated from the primary side pressure and the differential pressure without considering the degree of steam flow, so there is a problem that the measurement accuracy of the steam flow rate is poor.

Therefore, the technical problem of the present invention is to perform dryness correction so as to be able to accurately measure the steam flow rate.

Means for Solving the Problems The technical means of the present invention taken to solve the above-mentioned technical problems is to provide a throttling mechanism in the steam piping, and to reduce the pressure on the primary side of the throttling mechanism and the pressure on the primary side of the throttling mechanism. In a differential pressure steam flowmeter that measures the flow rate by detecting the pressure difference between the primary side and the secondary side, a dryness detection means is provided to detect the dryness of the steam on the primary side of the throttle mechanism. It measures steam flow rate from differential pressure and dryness.

action The operation of the above technical means is as follows.

The differential pressure between the upstream and downstream parts of the throttle mechanism is input to the flowmeter. Steam pressure on the primary side of the throttle mechanism is detected by the pressure detection means and input to the flow meter. Further, the dryness of the steam on the primary side of the throttle mechanism is detected by the dryness detection means and inputted to the flow meter. The mass flow rate of fluid through the restriction mechanism is proportional to the square root of the specific weight.

Therefore, the flow rate of dry saturated steam is the differential pressure bo and the specific weight 1/v
``, w=kJΣ■−〒FheF.

The specific volume V of wet steam is v=vx0v (1-x), where the degree of dryness is X, and the ratio of the specific volume of wet steam to that of dry saturated steam is v/v"=x10v (1-x)/v".

Since v”/v’ is a very large value, V/V=X It can be done.

Therefore, the flow rate of wet steam is It can be calculated as

Effect of the invention The present invention produces the following unique effects.

As described above, in the present invention, since the steam flow rate is calculated by correcting the steam flow rate, it is possible to accurately measure the steam flow rate. It is also possible to calculate and display the flow rate of dry saturated steam in wet steam or the flow rate of water.

Embodiment An embodiment illustrating a specific example of the above technical means will be described (see FIG. 1).

A throttle mechanism 2 is provided in the middle of a steam pipe 1. The primary side 3 and secondary side 4 of the throttling mechanism 2 are each connected to a flow meter 7 via a pressure piping 5.6. A pressure sensor 8 for detecting the pressure on the primary side 3 and a dryness sensor 19 for detecting the dryness of the steam on the primary side 3 are attached. The detection signals from both sensors are
It is input to the flow meter 7 via the signal line 10.11. The dryness sensor 9 passes wet steam through an orifice 12 to a measurement container 14 equipped with a temperature sensor 15 and a pressure sensor 16.
The signals from the temperature sensor 15 and the pressure sensor 16 are input to the calculator 17, and a pre-stored Molière diagram or saturated steam table is used.
The dryness is measured based on the superheated steam table.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a differential pressure steam flow meter according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional differential pressure steam flow meter. 1: Steam piping 2: Throttle mechanism 3 primary side 4: Secondary side 7: Flow meter 8: Pressure sensor 9: Dryness sensor

Claims (1)

[Claims] 1. Provide a throttle mechanism in the steam piping, detect the pressure on the primary side of the throttle mechanism and the differential pressure between the primary side and the secondary side of the throttle mechanism,
In a differential pressure steam flow meter that measures flow rate, a dryness detection means is provided to detect the dryness of the steam on the primary side of the throttle mechanism,
A differential pressure steam flowmeter that measures the steam flow rate from the primary pressure, differential pressure, and dryness.