JPH02269923A - Constant temperature type heat flow flux sensor - Google Patents

Abstract

PURPOSE:To reduce the cost of the sensor and to make stable measurement with high accuracy by baking a resistor having a large coefft. of temp. resistance on a ceramics substrate having a low thermal conductivity. CONSTITUTION:The sensor is constituted by baking the resistor 2 consisting of the material having the large coefft. of temp. resistance onto the substrate consisting of the ceramics having the low thermal conductivity, connecting lead wires 3, 3' to both sides of the resistor 2 and coating the outside surface of the resistor 2 with a protective film 4. Since the heat conduction from a heat transmission tube mounted with the sensor cannot be disregarded with the substrate 1, the material having the lowest possible thermal conductivity is selected and the better result is obtd. with the smallest possible thickness of the substrate 1. For example, zirconia ceramics having the high strength to allow the working to a small thickness and having the low thermal conductivity is effectively usable. The material having the large coefft. of temp. resistance is preferable for the resistor 2 and a heating element part baked with, for example, nickel or the like on the substrate is formed. An inorg. thin film consisting of glass on the like is used for the protective film 4. The stable measurement is made in this way with the high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a constant temperature heat flux sensor. 1
This invention relates to a sensor used to elucidate the heat transfer mechanism in an II heat exchanger.

(Conventional technology and its problems) Flow zero layer heat exchangel! Because of its excellent heat transport properties within layers and between layers and heat transfer surfaces, the A device is effective as a high-performance heat transfer promotion method for heat exchangers that use gas as a heat medium.

On the other hand, fluidized beds inherently have unsteady characteristics due to the generation and passage of bubbles, the mixing of bubbles and particles, etc., and the phenomena are complex, so there is insufficient research into the essence of heat transfer characteristics. In order to investigate the heat transfer mechanism, it is important to elucidate the unsteady heat transfer characteristics. In other words, there are some precedents for the development of sensors for measurement when the fluidized bed is a gas or liquid, which causes almost no damage to senna, but when the fluidized bed is a solid-gas system, where particles are There is no precedent for developing a measurement sensor that can repeatedly collide with the sensor.

Furthermore, when a sensor for measurement of gas or liquid is used in a solid-gas fluidized bed, there is a problem that the collision between the fluidized bed and the sensor causes significant damage, making stable and highly accurate measurements impossible. have

(Object of the invention) In view of the above-mentioned conventional circumstances, the present invention has been developed in such a way that the fluidized bed is solid.
The object of the present invention is to provide a low-cost sensor that can perform stable and highly accurate measurements even in the case of gaseous systems, can be mass-produced, and is low-cost.

(-Structure of the Invention) In order to achieve the above object, the constant temperature heat flux sensor of the present invention has a ceramic substrate with low thermal conductivity.
Baked low resistance made of material with large temperature resistance coefficient,
Lead wires are connected to both sides of the resistor, and the outer surface of the resistor is coated with a protective film.

Since the heat conduction from the conduction tube to which the sensor is attached cannot be ignored for the above board, it is preferable to choose a material with as low thermal conductivity as possible, and for the board thickness to be as thin as possible in view of the speed of thermal response. Zirconia-based ceramics can be effectively used because they have high strength, can be processed even if they are thin (0,21Wi), and have low thermal conductivity.

The resistor fixed on the substrate is preferably made of a material with a large temperature resistance coefficient, such as nickel (NL>), platinum (Pt
), etc., and are baked onto the substrate to form a heating element.

The protective film covering the outer surface of the resistor prevents the resistor from being worn out due to collisions with particles in the fluidized bed, and is made of an inorganic thin film such as glass or ceramic.

(Function) According to the above configuration, since the resistor part of the sensor is covered with a protective film, the resistor part is completely protected even if solid particles of the fluidized bed collide with it, and the resistance value remains constant over a long period of time. This enables stable measurements.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. In the figure, 1 is a substrate made of zirconia ceramic with low thermal conductivity, and this substrate 1 has a thickness of 200 μm.
It is formed into a rectangular shape with a width of 2 m and a length of 14 m, and a resistor 2 is printed on the upper surface of the substrate 1. Lead wires 3 and 3' are connected to both the left and right sides of the resistor 2, and the outside of the resistor 2 is A protective film 4 is coated on the surface.

The above resistor 2 is made of nickel (NL), which has a large temperature resistance coefficient.
A base 1- containing 40% by weight of nickel boride (NLB) and 60% by weight of lead borosilicate glass is printed on the substrate 1 using a base 1 and fired.

Before baking the resistor 2, lead wires 3.3'' are baked on both left and right sides of the upper surface of the substrate 1, and the side portions are overlapped and connected to the lead wires 3 and 3', and the two resistors are baked.

The lead wire 3.3' is made of silver (All) 733 layers.

A paste containing 188% palladium (Pd) and 9% glass is printed on the upper surface of the substrate 1 and fired.

Cover the outer surface of resistor 2! lIl! 4 is to prevent wear of the resistor 2 due to particles in the fluidized bed, and a paste of titanium oxide TiQ230% by weight and glass 70% by weight is printed so as to cover the upper surface of the resistor 2, and this is baked to protect it. A membrane 4 is formed.

The material of the protection 14 is not limited to the above-mentioned materials, but may include non-IIR materials such as aluminum oxide (A#20s), aluminum nitride (A#N), titanium nitride (TiN), etc.
I membrane can be used.

The sensor completed as described above has a high TCR value
(TCR = 2x10'ppm/'C), and can accurately measure fluctuations in resistance value due to minute temperature changes.

Unsteady local heat transfer coefficient measurement using the sensor configured as described above is performed by keeping the sensor at a constant temperature (
The unsteady local heat transfer coefficient is measured under the condition that the tube wall temperature is constant. That is, the output voltage of the heating power supply corresponding to the voltage across the sensor is used as a time series signal, and approximately 3 x 10' pieces of data are input into a computer at a sampling frequency of 100112 to determine the unsteady heat flux. The unsteady heat transfer coefficient can be determined by using the value of a point several CM directly below.

(Efficiency of the Invention) As detailed above, the senna of the present invention is made by baking a resistor made of a material with a large temperature resistance coefficient onto a ceramic substrate with low thermal conductivity, and connecting lead wires on both sides of the resistor. At the same time, the outer surface of the resistor is coated with 111u, so the resistor is completely protected and will not be worn out even if particles in the fluidized bed collide with it, maintaining the specified resistance value over a long period of time. is maintained.

Therefore, even if the fluidized bed is a solid-gas system, stable and highly accurate measurements can be made, mass production is possible, and costs can be reduced.

Therefore, it is possible to provide a sensor useful for elucidating the heat transfer structure of a solid-gas flow Al single-layer heat exchanger.

[Brief explanation of drawings]

The drawings show an example of the actual pressure of the sensor according to the present invention, and FIG. 1 is a vertical sectional front view, FIG. 2 is a partially cutaway plan view of the same, and FIG. 3 is a block diagram showing sensor fabrication. In the figure, 1: Substrate 2: Resistor 3.3': Lead wire 4: Protective film

Claims (2)

[Claims] (1) A resistor made of a material with a high temperature resistance coefficient is baked onto a ceramic substrate with low thermal conductivity, and lead wires are connected to both sides of the resistor, and the outer surface of the resistor is covered with a protective film. A constant temperature heat flux sensor characterized by being coated. (2) the substrate is made of zirconia ceramic;
2. A constant temperature heat flux sensor according to claim 1, wherein a nickel-based resistor is baked onto the substrate, and the surface thereof is covered with a protective film made of an inorganic thin film such as glass or ceramic.