JPH042922A - Differential gas flow meter - Google Patents

Abstract

PURPOSE:To prevent moisture condensation within a pressure conduit thereby to improve the measuring accuracy by providing a dry pot filled with a drying agent. CONSTITUTION:A day pot 9 filled with a drying agent 8 such as silica gel or the like is provided in the middle of the path of pressure guide pipes 3, 4. A gas including humidities like water vapor and entering the pipes 3, 4 from a gas passage pipe 1 through a pressure detecting part 2 is absorbed by the drying agent 8 in the dry pot 9. The pipes 3, 4 are always filled with a dry gas, and therefore no condensation occurs in the pipes 3, 4 while a gas flow rate is measured. Even when the inner diameter of each pipe 3, 4 is as small as several mm or so, it is possible to positively prevent the defective instrumentation resulting from cloggings of the pipe due to the condensation or water drops.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential pressure type gas flowmeter that is applied to, for example, a gas supply line of fuel cell power generation equipment.

[Prior Art] First, FIG. 2 shows the configuration of a conventional differential pressure type gas flowmeter. In the figure, 1 is a gas flow pipe through which the gas to be measured flows, and 2 is an average value pitot tube installed inside the gas flow pipe 1 (the probe has multiple total pressure measurement holes and static pressure measurement holes). A Pitot tube type pressure detecting section 3.4 is a pressure guiding pipe that guides the total pressure and static pressure of the gas flow pipe 1 detected by the pressure detecting section 2 to the differential pressure/flow rate converter 5. Furthermore, impulse pipes 3 and 4
A drain pot 6 is connected to the lowest pipe position of the pipe line, and a drain pipe 8 is drawn out from the drain pot 6 via a stop valve 7.

The measurement principle of such a differential pressure type gas flowmeter is well known, and assuming that the gas to be measured is flowing in the direction of the arrow in the gas flow pipe 1 as shown in the figure, the pressure detection unit installed inside the gas flow pipe 1 is used. 2, the total pressure and static pressure are respectively guided to the differential pressure/flow rate converter 5 via the pressure guide line 3.4. Further, the differential pressure/flow rate converter 5 includes a semiconductor strain sensor or a capacitance type differential pressure sensor, and a circuit that converts the differential pressure between the total pressure and the static pressure into an electrical signal, The gas flow rate is calculated from the differential pressure between the total pressure and the static pressure applied via the impulse pipe 3.4, converted into an electrical signal, and outputted to an indicator, recorder, etc. It should be noted that as the pressure detection section 2, in addition to the pitot tube type, orifice and venturi tube types are also well known.

On the other hand, the drain pot 6 is a drain that collects water droplets (water vapor contained in gas condensed inside the impulse tubes) generated inside the impulse tubes 3 and 4 in the pot and drains them out of the system. It is fulfilling its role.

[Problem to be solved by the invention]

By the way, as mentioned above, the drain pot 6 is connected to the impulse pipes 3 and 4.
In the conventional structure provided with this, the following problems remain.

In other words, if the gas flowing through the gas flow pipe 1 contains a large amount of water vapor, the pressure impulse pipe 3
．． 4, dew condensation occurs in the pipe line due to ambient temperature conditions.

In this case, if the pressure impulse tube 3.4 is assembled with an inner diameter of about a few centimeters, water droplets condensed within the pressure impulse tube will remain attached to the tube wall due to surface tension and will be difficult to flow down to the drain pot 6. In such a state, the impulse line 3.4 may remain blocked by water droplets, or the water droplets may flow down the impulse line 3, 4 and drain into the drain pot 6.
During the discharge, the gas pressure transmission function to the differential pressure/flow rate converter 5 is inhibited. Note that this phenomenon of water droplet clogging of the impulse tube is caused especially when the gas to be measured contains a large amount of water vapor, and the gas flow rate flowing through the gas flow pipe 1 is small, resulting in a pressure difference between the impulse tubes 3 and 4. It has been confirmed that this phenomenon tends to occur when the gas flow rate is low.1, and this causes a decrease in the reliability and measurement accuracy of the gas flowmeter.

The present invention has been made in consideration of the above points, and is aimed at preventing the occurrence of dew condensation within the impulse pipe, preventing the occurrence of measurement errors due to dew condensation, and improving reliability and measurement accuracy. The purpose of the present invention is to provide a differential pressure type gas flow meter with

[Means to solve the problem]

In order to solve the above problems, the differential pressure type gas flowmeter of the present invention is constructed by interposing a dry pot filled with a desiccant in the middle of the impulse pipe instead of the conventional drain pot. .

[Effect]

With the above configuration, the gas entering the pressure conduit from the gas flow pipe is dehumidified as water vapor and the like contained in the gas are adsorbed by the desiccant of the dry pot. Therefore, there is no risk of dew condensation occurring within the pressure impulse pipe, and measurement failures due to dew condensation and water droplets can be prevented. Note that it is preferable to install the dry pond as close to the inlet side of the impulse pipe as possible, that is, near the branch point from the pressure detection section.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention, and the same members corresponding to FIG. 2 are given the same reference numerals.

That is, in FIG. 1, in place of the drain pot 6 in FIG. 2, a desiccant 7,
For example, a dry pot 8 filled with silica gel or the like is interposed.

With this configuration, the gas containing moisture such as water vapor that enters the pressure impulse pipes 3 and 4 from the gas flow pipe l side via the pressure detection unit 2 is dehumidified by the desiccant 7 of the dry pot 8. Therefore, the impulse tubes 3 and 4 are always filled with dry gas, and there is no condensation inside the impulse tube 3.4 during measurement of gas flow rate, and the impulse tube 3.4 is a thin tube with an inner diameter of several square meters. However, there is condensation.

It is possible to reliably prevent measurement errors such as clogged impulse pipes caused by water droplets. It is assumed that the dry pot 8 filled with the desiccant 7 is replaced with a new one during periodic inspection.

〔Effect of the invention〕

Since the differential pressure type gas flow meter of the present invention is configured as described above, it achieves the following effects.

(1) The impulse pipe connecting the pressure detection part and the differential pressure/flow rate converter is always kept dry because the water vapor contained in the gas is dehumidified by the desiccant in the dry pot, preventing dew condensation. It is possible to reliably prevent clogging of the impulse pipe caused by water droplets.

(2) This eliminates the risk of measurement failures due to dew condensation and water droplets, and improves the reliability and measurement accuracy of the gas flow meter.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional differential pressure type gas flow meter. In the figure,

Claims (1)

[Claims] 1) A differential pressure type gas flow meter that measures the gas flow rate in a gas flow pipe, in which the pressure detection section installed in the gas flow pipe and the differential pressure/flow rate converter are connected via a pressure impulse pipe. ,
A differential pressure type gas flow meter characterized in that a dry pot filled with a desiccant is connected in the middle of the pressure impulse pipe.