JPS588732B2 - heat flow sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat flow sensor that measures heat flow density by detecting the temperature difference between the front and back surfaces of a thermal resistor using a group of differential thermocouples, and is easy and inexpensive to manufacture. Moreover, it is an object of the present invention to provide a heat flow sensor that can perform highly accurate measurements without being affected by thermal disturbances.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numerals 111 and 112 are thermal resistors made of materials with approximately the same thickness and different thermal conductivities, and these thermal resistors 111 and 112 are joined so that they are aligned on approximately the same plane. ing.

Further, 121 and 122 are differential thermocouple groups (hereinafter referred to as thermopiles), and these thermopiles 121 and 122 sequentially connect the thermocouple wire 13 on the positive side and the thermocouple wire 14 on the negative side.
The thermopiles 121 and 122 have a hot junction on one side of each of the corresponding thermal resistors 111 and 112. The group T1 is arranged so that the cold junction group T2 is located on the other side.

Further, reference numerals 151 and 152 are made of a heat insulating member, and hot junction groups T located on the front and back surfaces of the thermal resistors 111 and 112 are shown.
This is a covering material that is pressure-bonded with an adhesive or the like with the cold junction group T2 and the cold junction group T2 sandwiched therebetween.

In this way, a heat flow sensor is created by integrating the thermal resistors 111, 112, thermopiles 121, 122, and covering materials 151, 152.

Furthermore, since the sensitivity of the heat flow sensor is temperature dependent, a thermocouple 16 for determining the temperature of the heat flow sensor is provided in the heat flow sensor alongside the thermopile.

The heat flow sensor made in this way is attached to the surface of a measured object (not shown here), and the heat flow rate per unit area (heat flow density ψ) passing through the measured object is measured by the thermal resistors 11, 1.
It is detected from the temperature difference between the front and back surfaces of 12.

Therefore, in the case of this Fig. 1, each thermopile 12A
, 122 are taken out independently, and these outputs are input to an arithmetic circuit (not shown).

That is, the temperature difference between each of the thermal resistors 111 and 112 is measured independently, and the respective signal amounts are calculated according to a formula determined by the above-mentioned calculation circuit.

When calculated in this way, it can be seen from the results that a heat flow sensor that does not generate any thermal disturbance can be obtained.

This will be mathematically analyzed and shown below.

First, two different types of thermal resistors 111 as shown in FIG.
, 112, the basic measurement equation of the surface-attached heat flow sensor is as follows.

ψ0=(1+F(dis)×1/C1)1/lδt1・
...(1)ψE=(1+F(...)X1/C2
)2/lat2---(2) Here, ψ0 is the heat flow density to be determined, F(dis) is the thermal disturbance caused by attaching the heat flow sensor, and C1 and C2 are the respective thermal resistors. The total thermal conductance of the heat flow sensor on the 111 and 112 sides, λ1 and λ2 are the thermal conductivities of the thermal resistors 111 and 112, respectively, and l is the thickness of the thermal resistors 111 and 112 (in this case, 2
The thicknesses of the two thermal resistors 111 and 112 were made equal), δ
t1tδt2 is a temperature difference occurring between the front and back surfaces of the thermal resistors 111 and 112.

Next, each of the above equations (1) and (2) is transformed, and equation (4) is obtained by subtracting the sides of equations (2) and (3) and rearranging them with respect to 1/ψ0.

here And so.

If the temperature range is limited in the above equation (4), 1/λ
Since 1-λ2, 2/C2, and 1/C1 can each be regarded as constants, 1/λ1-λ2・2/c2 can be considered as one constant, 1/
Letting λ1-λ2・λ1/C1 be another constant, δ, 1, δ
, 2 is detected by the thermopiles 121 and 122, respectively, and the output is VF1.

If VF2 is used, equation (4) becomes.

Here, A and B are constants. Therefore, by expanding the equation as described above, the term of thermal disturbance F(dis) disappears, and the first
If the outputs of the thermopiles 121 and 122 are taken out independently as shown in the figure, the influence of thermal disturbance can be eliminated.

Note that if the constants A and H have temperature dependence, it goes without saying that temperature dependent equations may be used for each.

In the above embodiment, the output is taken out independently from each thermopile 121, 122, but the method shown in FIG. 2 can also be used effectively as a sensor, so a description will be given below.

In the case of FIG. 2, as in the case of FIG. 1, the basic measurement formula is as follows.

The relationship between ψ0 and (δ11 - δ12) is found from these two equations, and it becomes ψ0 - (δ11 - δt2). Therefore, ψo - (δt1 - δt2) (γ: contact thermal conductance, L: total thickness of the sensor, k
: Thermal conductivity of the coating material).

This equation (10) is the basic measurement equation shown in FIG. 2, but when the temperature of the surface to be measured is about room temperature to about 200° C. and the atmosphere is under natural convection, the following approximate equation can be used.

In other words, ψ0mi(A+BT)(δtl−δt2)””(
II).

Here, A and B are constants. T indicates the temperature of the sensor.

A measurement example using the heat flow sensor in the case of Fig. 2 is shown in Fig. 3.
As shown in the figure.

The heat flow sensors used here are thermal resistors iii, ii2
The thickness is 1! A magnetic rubber sheet with a thickness of 1 l and an artificial cork sheet with a thickness of 1 l were used, chromel and constantan were used as the thermocouple wires 13 and 14, and a CA thermocouple was used for the thermocouple 16 incorporated in order to find out the temperature dependence. This is the characteristic when a pair is used, and the horizontal axis shows the output (mv) of the CA thermocouple, and the vertical axis shows the reciprocal of the sensitivity (Kca1/m2h-mv).

In addition to the method shown in Figs. 1 and 2 above, a method of calculating the sum of the outputs of two thermopiles 121 and 122 as shown in Fig. 4 can also be used to perform measurements with the same characteristics as a normal heat flow sensor. Although it is possible, a measurement example thereof is only shown in FIG. 5 here, and its mathematical explanation will be omitted.

As described above, according to the present invention, a thermal resistor to which a main differential thermocouple group is attached is joined in a plane to another thermal resistor having approximately the same thickness and different thermal conductivity. However, since this thermal resistor is equipped with a compensating differential thermocouple group that compensates for the output of the main differential thermocouple group, it can be used with the same characteristics as the normally used heat flow sensor. Of course, by appropriately processing each output signal, it becomes possible to measure the heat flow density with high accuracy by eliminating the influence of thermal disturbance, and it is possible to provide a practically excellent heat flow sensor.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram for explaining one embodiment of the present invention, FIG. 2 is a schematic block diagram for explaining a modification of the above embodiment, and FIG. FIG. 4 is a schematic configuration diagram for explaining another modification of the above embodiment, and FIG. 5 is a diagram showing an example of measurement by the heat flow sensor of FIG. 4. . 111, 112...Thermal resistor, 121, 122
...Thermopile, 151,152...
・Covering material.

Claims (1)

[Claims] 1. At least two thermal resistors with different thermal resistances joined on 1,000 sides, and one of these thermal resistors is arranged such that a group of hot junctions and a group of cold junctions are located on the front and back surfaces of the thermal resistor. and a compensating differential thermocouple group arranged on another thermal resistor so that a hot junction group and a cold junction group are located on the front and back surfaces of the thermal resistor. A heat flow sensor characterized by: