JPH0254131A - Method for simultaneously measuring surface temperature and emissivity of body - Google Patents

Abstract

PURPOSE:To simultaneously measure the surface temp. and emissivity of a body to be measured by a simple constitution by providing contact type temp. sensors at a plurality of positions different in a form coefficient at different distances or in different directions from one point of the body to be measured. CONSTITUTION:The radiation heat transfer from a furnace wall to a steel plate 3 becomes dominant environment within an annealing furnace. The indicated temp. T of a thermocouple 1, the surface temp. Ts and emissivity epsilons of the steel plate 3 and the temp. Tw of the furnace wall are made unknown to detect the temps. at respective positions by three thermocouples 1, 5, 6 arranged at positions different in mutual form coefficients Fw, Fs. Formulae are calculated at every indicated temps. of the thermocouples 1, 5, 6 and these simultaneous equations are solved to simultaneously estimate the surface temp. Ts and emissivity epsilons of the steel plate 3 and the temp. Tw of the furnace wall 2.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a method for simultaneously measuring the surface temperature and emissivity of an object, and is particularly suitable for use in measuring the temperature of a heated steel plate in a heating furnace or a heat insulation cover. , relates to a method for simultaneously measuring the surface temperature and emissivity of an object to be measured in a non-contact manner in an environment dominated by radiant heat transfer. [Conventional Technique #r] In general, when measuring the surface temperature of an object without contact, the radiation law of the blank is often used as in the case of a radiation thermometer, that is, the heat radiated from the object is Since energy depends on the temperature of the object, the surface temperature of the object to be measured can be measured in a non-contact manner by detecting the thermal radiation energy of the object, like a radiation thermometer. On the other hand, when measuring the surface temperature of an object to be measured using a radiation thermometer, it is assumed that the emissivity of the object to be measured is known. Therefore, when the emissivity of the object to be measured is unknown or uncertain, an attempt is made to simultaneously measure the surface temperature and emissivity of the object to be measured. For this purpose, as disclosed in Japanese Patent Application Laid-Open No. 57-50627, two measuring instruments using the blank radiation law, such as radiation thermometers, are installed, and the radiation detected by each measuring instrument is It has been proposed to simultaneously measure the surface temperature and emissivity of the object to be measured by comparing the values of . That is,
In Japanese Patent Application Laid-Open No. 57-50627, two cavities each having a small hole at a position opposite to the opening are arranged adjacently so that the opening is located near the surface of the object to be measured. The temperature of the cavity is set near the lower limit of the measurement range, and the temperature of the other cavity is set near the upper limit of the measurement range, and two radiation thermometers placed near the small holes of each cavity measure the temperature of the small hole. The radiation of the object to be measured is measured through each hole, and the surface temperature and emissivity of the object to be measured are determined using the obtained readings from the two radiation thermometers and the two cavity set temperatures. Also, as disclosed in Japanese Patent Application Laid-Open No. 57-30916,
The use of auxiliary heat sources has also been proposed. That is, in Japanese Patent Application Laid-Open No. 57-30916, a radiation source (auxiliary heat source) is placed facing the object to be measured, and a rotating sector that intermittents the radiant energy from the radiation source and a rotating sector that intermittents the radiation energy from the object to be measured are arranged between them. A beam splitter is provided to guide the energy to the radiometer, and the temperature and emissivity of the object to be measured are calculated from each output of the radiometer when the rotating sector does not block the radiant energy and when the radiant energy passes through. There is. However, in the above conventional example, the radiation thermometer is
Since a stand or an auxiliary heat source such as a radiation source is used, the device becomes complicated and large, and there are problems in that the manufacturing cost is high and the product is expensive. In addition, when measuring the surface temperature of a steel plate in a heating furnace, for example, strict thermal constraints are imposed on the arrangement of sensors such as radiation thermometers and equipment such as radiation sources (auxiliary heat sources). Another problem was that it was extremely difficult to measure the surface temperature and emissivity of the steel plates inside.

[Problem to be solved by the invention]

The present invention has been made in view of the problems of the prior art as described above, and an object of the present invention is to provide a method that can simultaneously measure the surface temperature and emissivity of an object to be measured with a simple configuration.

[Means to achieve the task]

The present invention enables the measurement of view factors at different distances or in different directions from one point on the object to be measured when simultaneously measuring the surface temperature and emissivity of the object to be measured in a non-contact environment in an environment dominated by radiant heat transfer. Contact temperature sensors are installed at multiple different positions,
The above object is achieved by simultaneously estimating the surface temperature and emissivity of the object to be measured through predetermined calculations using temperature values detected by these temperature sensors.

[Effect]

The present invention provides that, in an environment where radiation heat transfer is dominant, in the heat balance equation for the temperature measuring part of a contact temperature sensor such as a thermocouple, compared to radiation from the wall or radiation from the object to be measured,
The heat conduction of the temperature sensor and the heat transfer from the gas temperature are extremely small and are ignored, focusing on scales and the like. FIG. 1 is a diagram for explaining the present invention in detail. In the figure, 1 is a thermocouple that is an example of a contact temperature sensor, 2 is a furnace wall of a heating furnace, etc., 3 is an object to be measured, and 4 is a diagram for explaining the present invention in detail. is the temperature measuring part of thermocouple 1. In this figure, when the length of the temperature measuring section 4 of the thermocouple 1 is dx and considering the heat balance regarding the temperature measuring section 4 of the thermocouple 1, the following formula (1) holds true. (Dλ/4) ・(d'T/d×' ) 10a (T
cL-T) 1 Fwεy, +σ(TW'-T')-F
+3εBσ(T"rs')=o-(1) where D is the diameter of thermocouple 1, λ is the thermal conductivity of thermocouple 1, and T is thermocouple 1.
indicated temperature, × is the insertion position of thermocouple 1 (distance between temperature measuring part 4 of thermocouple and furnace wall 2), α is heat transfer coefficient, TQ is gas temperature, FW, FS are view factors, εW is furnace Emissivity of wall 2, εS
is the emissivity of the object to be measured 3, σ is the blackbody radiation coefficient, Ts is the surface temperature of the object to be measured 3, and Tw is the temperature of the furnace wall 2. In the above equation (1), the first term (Dλ/4)(d' T
/d×') represents the heat conduction of thermocouple 1, and the second term α(
TQ T) represents the heat conduction from the gas temperature, the third term F'wEW(j (Tw'T') represents the radiation from the furnace wall 2, and the fourth term F9εSσ(T4, Ts4) represents the radiation from the measured object. 3. In an environment where radiation heat transfer is dominant, the values of the first and second terms are much smaller than the values of the third and fourth terms. Therefore, under such an environment, the first term and the second term can be ignored, and the following formula (2) is obtained from the above formula (1). Fwεwσ(Tw'T')FBcBσ(T' − Ts')=t)" (2)
Therefore, in FIG. 1, the surface temperature Ts of the object to be measured 3
If the surface temperature Ts (unit: K) is unknown, the surface temperature Ts (unit: K) can be calculated using the following formula (3) using the indicated temperature T (unit: K) of thermocouple 1.
It can be estimated as follows. Ts=(T'-(Fw・εw/Fs・εs)X (Tw
'-T'))'/' =-(3) Furthermore, when the surface temperature T9 and emissivity εS of the object to be measured 3 are unknown, the view factors differ from each other, as shown by the solid line in Fig. 2, for example. Two thermocouples 1.5 are installed at each position, and the above (3
) and by solving these simultaneous equations,
The surface temperature Ts and emissivity εS of the object to be measured 3 can be estimated at the same time. Furthermore, if the surface temperature Ts, the emissivity εS, and the temperature Tw of the furnace wall 2 of the object to be measured 3 are unknown, for example, as shown by the solid line and the broken line in FIG. Thermocouples 1.5.6 are provided, the above equation (3) is obtained for each thermocouple 1.5.6, and by solving these simultaneous equations, the surface temperature Ts and emissivity εS of the object to be measured 3 can be calculated. ,
and the temperature Tw of the furnace wall 2 can be estimated at the same time. Hereinafter, as shown in FIG. 3, the surface temperature Ts of the object to be measured 3
, emissivity εS, and temperature Tw of the furnace wall 2 are unknown, and an example of the arithmetic processing of the present invention will be described by taking as an example a case where actually measured values are used for Tw. The arithmetic processing in this case is performed as shown in FIG. That is, first, the view factors FW and F9 are determined (step 100), and then, for example, the value of the furnace wall temperature Tw actually measured by the compensation conductor 9 and the temperature measurement giT detected by the thermocouple 1.5 are determined.
+, Tz, and the known wall emissivity εW (usually about 1.0
) is used to calculate the emissivity εS of the object to be measured 3 (
Step 102) Then, using this emissivity εS and the like, the surface temperature T9 of the object to be measured 3 is calculated from the above equation (3) (Step 104). Figure 5 shows the estimated ITs' of the surface temperature Ts obtained as described above and the measured temperature fia actually detected by the radiation thermometer.
It is a diagram comparing and showing the relationship with Ts, and the higher the measured temperature value Ts, the higher the surface temperature estimation [
It can be seen that the accuracy of Ts' is high.

[Examples] Examples of the present invention will be described below with reference to the drawings. FIG. 6 is a longitudinal cross-sectional view of a main part of a continuous annealing furnace in which the present invention is implemented, and FIG. 7 is a cross-sectional view taken along the line ■-■ in FIG. 6. In Section 6 and FIG. 7, the same symbols as in FIG. 1 and FIG. 2 are used with the same meaning, and repeated explanations here will be omitted. Further, 7 is a roll that runs (moves) the object to be measured (f!I4 board) 3 in the direction of the arrow. Note that the object to be measured 3 is placed in the direction of the arrow in FIG.
In FIG. 7, the vehicle is traveling in a direction perpendicular to the paper surface. The inside of the annealing furnace is an environment in which radiation heat transfer from the furnace wall 2 to the steel plate, which is the object to be measured 3, is dominant, and is therefore suitable for carrying out the present invention. In an embodiment with such a configuration, the surface temperature Ts of the steel plate 3, the emissivity εS, and the furnace wall temperature Tw are unknown,
The temperature at each position is detected by three thermocouples 1.5.6 arranged at positions having different view factors. In addition, for each indicated temperature of each thermocouple 1.5.6, the above (3)
Equations are obtained, and by solving these simultaneous equations, the surface temperature Ts of the object to be measured 3, the emissivity εS, and the temperature Tw of the furnace wall are estimated at the same time. FIG. 8 is a vertical cross-sectional view of the main part of hot rolling inside the heat insulation cover in which the present invention is implemented, and FIG.
FIG. In FIGS. 8 and 9, the same symbols as those in FIGS. 6 and 7 are used with the same meaning, and repeated explanation will be omitted here. Further, 8 is a heat insulating cover, and 9 is a compensating conductor buried in a predetermined portion of the heat insulating cover 8, for example. In an embodiment having such a configuration, the surface temperature Ts of the steel plate 3 and the temperature TW of the furnace wall of the heat insulation cover 8 are unknown,
On the other hand, since the thermal cover 8 has good heat conduction within the wall,
The temperature Tw of the furnace wall is efficiently detected by the compensation conductor 9. Furthermore, using the indicated temperature T of the thermocouple 1, the surface temperature Ts of the object to be measured 3 can be estimated from the above equation (3). Note that the present invention is not limited to the above-described embodiments, and can be modified in various ways. For example, other contact thermometers may be used instead of thermocouples. Effects of the Invention As explained in detail above, according to the present invention, in an environment where radiation is dominant, a contact thermometer can be used to easily measure the surface temperature and emissivity of the object e1 to be measured. can be measured simultaneously. Moreover, since the structure is simple, the manufacturing cost of the apparatus for performing such measurements is also low.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a diagram showing one example of the configuration of the present invention, and FIG. 3 is a diagram showing another example of the configuration of the present invention. FIG. 4 is a flowchart showing the arithmetic processing procedure in the column of FIG. 3, FIG. 5 is a diagram comparing actual values measured by a radiation thermometer and estimated values according to the present invention, and FIG. , FIG. 7 is a longitudinal cross-sectional view showing the first embodiment of the present invention, FIG. 7 is a cross-sectional view taken along the line ■-■ in FIG. 6, and FIG. 8 is a longitudinal cross-sectional view showing the second embodiment of the present invention. , FIG. 9 shows r in FIG.
FIG. 3 is a cross-sectional view taken along the X-rX line. 1.5.6... Thermocouple, 2... Furnace wall, 3... Object to be measured (steel plate), 4... Temperature measuring part of thermocouple, 7... Roll, 8... Heat insulation cover 9...Compensation lead wire.

Claims (1)

[Claims] (1) In a method of simultaneously measuring the surface temperature and emissivity of an object to be measured in a non-contact manner in an environment where radiant heat transfer is dominant, view factors that differ at different distances or in different directions from one point on the object to be measured are used. A method of measuring an object characterized in that contact type temperature sensors are provided at a plurality of positions, and the surface temperature and emissivity of the object to be measured are simultaneously estimated by predetermined calculations using the temperature values detected by these temperature sensors. Method for simultaneous measurement of surface temperature and emissivity.