JPH075036U - Fluid temperature measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] To measure the temperature of high-pressure fluid such as high-pressure steam in a boiler with good followability. [Structure] A thermometer (thermocouple 6) is welded to the outer surface of the thin branch pipe 2 through which a part of the fluid in the mother pipe 1 is guided so as to eliminate contact resistance and measure the fluid temperature with good followability. did.
In addition, the orifice 5 is provided upstream and downstream of the thermometer in the branch pipe 2.
By providing a and 5b, the heat transfer coefficient of the inner surface of the branch pipe immediately downstream of the orifice is increased and the followability of the thermometer to changes in fluid temperature is improved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fluid temperature measuring device which is used for measuring the steam temperature of a high-pressure boiler in an unsteady state and is particularly suitable for measuring the temperature of a high-pressure fluid.

[0002]

[Prior art]

 Conventionally, to measure the temperature of a high-pressure fluid such as a boiler flowing in a thick tube, as shown in FIG. 3, a well 8 is attached to a mother tube 1 in which the high-pressure fluid flows in the direction of an arrow, and a thermocouple is installed in the well 8. A device for inserting the eggplant thermometer 9 and fixing it with a nipple 10 is used.

[0003]

[Problems to be solved by the device]

 When controlling when the load on the boiler changes, the fluid temperature in the boiler is measured and the control is performed based on the measured value. Recently, the rate of change in boiler load has increased, and the time constant of the response delay of the fluid thermometer must be about 10 seconds or less. However, since the time constant of a thermometer such as the conventional well-type temperature measuring device has a large time constant of about 30 seconds, there is a problem that the boiler, which changes at high speed, cannot be stably controlled. According to the study by the present applicant, it was found that the cause of the delay of the thermometer was the contact resistance between the thermocouple and the well.

The present invention is intended to provide a fluid temperature measuring device capable of solving the above problems.

[0005]

[Means for Solving the Problems]

 The fluid temperature measuring device of the present invention takes the following means.

(1) A branch pipe through which a part of the fluid in the mother pipe is guided, and a thermometer welded to the outer surface of the branch pipe.

(2) In the fluid temperature measuring device according to (1), orifices are provided in the branch pipe upstream and downstream of the thermometer welded to the branch pipe.

[0008]

[Action]

 In the present invention (1), since a part of the fluid in the mother pipe is guided to the narrow branch pipe, the change in the fluid temperature in the mother pipe immediately changes in the fluid temperature in the branch pipe. Since the branch pipe is thin and has a small wall thickness, it has a small heat capacity and good followability to changes in fluid temperature. Further, since the thermometer is welded to the outer surface of the branch pipe, there is no contact resistance, so the temperature is almost the same as the pipe wall of the branch pipe, and the followability to changes in fluid temperature is good.

In the present invention (2), in addition to the above, by inserting the orifices upstream and downstream of the thermometer in the branch pipe, the heat transfer coefficient of the pipe inner surface immediately downstream of the orifice increases, The tube wall temperature, and hence the followability and response of the thermometer to changes in the fluid temperature, are further improved.

[0010]

【Example】

 An embodiment of a steam temperature measuring device of a supercritical pressure boiler according to the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 1 is a mother tube through which high-pressure steam flows in the direction of the arrow, and the mother tube 1 has a thick wall thickness of about 70 mm. There is provided a thin, substantially U-shaped branch pipe 2 that exits from the inside of the mother pipe 1 and returns to the inside of the mother pipe 1 again. As the branch pipe 2, an 8A-Sch160 inner diameter of 5.8 mm and a wall thickness of 4.0 mm is used, and its length is about 150 mm in order to avoid the influence of heat conduction from the mother pipe 1. A suction nozzle 3 is provided on the inlet side of the branch pipe 2 and opens toward the upstream side of the flow in the mother pipe 1, and the outlet side of the branch pipe 2 is located on the downstream side of the flow in the mother pipe 1. A discharge nozzle 4 that is open toward the side is provided.

An upstream first orifice 5 a and a downstream second orifice 5 b are provided inside the portion of the branch pipe 2 outside the mother pipe 1 at intervals of 6.5 mm. The area reduction rate of each orifice 5a, 5b is set to about 65%, and the pressure loss coefficient ζ is set to 0.27. A thermocouple 6 as a thermometer is attached to the outer surface of the branch pipe at a position approximately 4.5 mm downstream from the first orifice 5a between the orifices 5a and 5b of the branch pipe 2. As shown in FIG. 2, a groove having an inclination of about 45 ° is formed on the outer surface of the branch pipe 2, and a thermocouple 6 having a diameter of 1.6 mmφ is put in the groove and silver brazing 7 is applied thereto. The thermocouple 6 is welded to the outer surface of the branch pipe 2.

In this embodiment, the dynamic pressure of the steam flow in the mother tube 1 collides with the suction nozzle 3, and the static pressure decrease of about half of the dynamic pressure occurs in the discharge nozzle 4 on the downstream side of the flow. Due to the differential pressure, steam flows in the branch pipe 2 as shown by the arrow.

The pressure coefficient ζ in the branch pipe 2 is approximately 1.1 of the sum of the three right angle bends, the two orifices and the pipe friction pressure loss coefficient, and the differential pressure between the inlet side and the outlet side of the branch pipe 2 is As described above, since the dynamic pressure of the flow in the mother pipe 1 is about 1.5 times, the flow velocity in the branch pipe 2 is √1.5 / 1.1 = 1. When the flow velocity in the mother tube 1 is 10 m / s, it becomes about 12 m / s.

As described above, since the branch pipe 2 is thin and thin, and the steam having a large flow velocity flows inside the branch pipe 2, the temperature of the outer surface of the branch pipe 2 follows the temperature change of the steam well. . Further, since the thermocouple 6 is welded to the outer surface of the branch pipe 2, there is almost no contact resistance. Moreover, since the thermocouple 6 is located between the orifices 5a and 5b, the thermocouple 6 has a good followability with respect to the temperature change of steam as described below. Therefore, in the present embodiment, it is possible to measure the temperature of the steam in the mother tube 1 with good response and to reduce the time delay in response.

The improvement of responsiveness due to the orifice in this embodiment will be described below. The heat transfer coefficient α of the wall surface immediately downstream of the orifice is higher than the heat transfer coefficient α∞ of the smooth portion, and α / α∞ = 3.0 (D_N/ D_i). D here_i: Tube inner diameter, D_N: It is the inner diameter of the orifice. In this embodiment, D_i= 5.8 mm, D_N= 4.7 mm, α / α∞ = 2.4, and the heat transfer coefficient immediately downstream of the orifice is the heat transfer coefficient of the smooth part α∞ = 2000 Kcal / m ² About 2.4 times of h ℃, α = 4800 kcal / m²It becomes h ° C. Time constant t of the wall temperature at this time_cIs the following Equation 1 from the theoretical formula.

[0016]

[Equation 1]

In the present embodiment, b = 0.0068 m, λ = 7.5 × 10 ⁻³ kcal / ms ° C., K = 9.4 × 10 ⁻⁶ m ² / s, α = 1.33 kcal / m ² Since it is s ° C., B _i = 1. 2, t _c = 6.0 (s). This value sufficiently satisfies the time constant of 10 (s) or less required for boiler control with a high rate of change.

[0018]

[Effect of device]

 As described above, according to the present invention, the thermometer is welded to the outer surface of the thin branch pipe through which a part of the fluid in the mother pipe is guided, and further, the orifices are provided in the branch pipes upstream and downstream of the thermometer. Therefore, the temperature of the fluid in the mother tube can be measured with good followability and responsiveness.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 (a) is a sectional view thereof, and FIG. 1 (b) is a sectional view taken along line XX of FIG. 1 (a).

FIG. 2 is a detailed view of a portion A of FIG.

FIG. 3 is a sectional view showing a conventional high-pressure fluid temperature measuring device.

[Explanation of symbols]

 1 Mother Pipe 2 Branch Pipe 3 Suction Nozzle 4 Discharge Nozzle 5a First Orifice 5b Second Orifice 6 Thermocouple 7 With Silver Solder

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[Procedure amendment]

[Submission date] October 13, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (2)

[Scope of utility model registration request] 1. A temperature measuring device for a fluid, comprising: a thin branch pipe through which a part of the fluid in the mother pipe is guided; and a thermometer welded to an outer surface of the branch pipe. 2. The fluid temperature measuring device according to claim 1, wherein orifices are provided in the branch pipe upstream and downstream of the thermometer welded to the branch pipe, respectively.