JP6533097B2 - Gas heater and flow rate measuring method for gas heater - Google Patents

Description

  The present invention relates to, for example, a gas heater that raises the temperature of a gas to be heated by a heater and a flow rate measurement method thereof, and in particular to one that can accurately measure the flow rate of high temperature gas with a simple configuration.

For example, a gas heater is known which heats a gas to be heated such as water vapor with a heater to a high temperature, and can be used as a heat medium in food processing, manufacturing processes of industrial products, and the like.
For example, Patent Document 1 has an outer cylinder and an inner cylinder arranged concentrically, and a sheathed heater wound around the outer peripheral surface of the inner cylinder, and heats saturated steam to generate superheated steam. The device is described.

In the gas heater as described above, it may be required to measure the flow rate of the passing heated gas.
Heretofore, the flow rate measurement of the gas to be heated has been performed by separately providing a single flow meter such as a differential pressure type or a Karman vortex type outside the gas heater. However, in order to install such a flowmeter, it is necessary to install piping for bypassing the flow path, and the flowmeter itself is relatively large, which requires a large amount of space.
In addition, since the operating temperature of such a flowmeter is limited to a relatively low range in terms of heat resistance and corrosion resistance, for example, the flow rate measurement of superheated steam which may have an outlet temperature of about 500 ° C. Have difficulty.
Furthermore, such flow meters are usually expensive and thus disadvantageous in cost.

  As a prior art related to gas flow rate measurement, for example, Patent Document 2 discloses a thermal flow meter that measures the flow rate of liquid based on the temperature difference between the upstream side and the downstream side of the heater. It is described to provide a cooling mechanism.

Re-introduction 2009/047952 JP-A-5-79875

If the temperature of the gas to be heated is detected on the upstream side and the downstream side of the gas heater, and the flow rate can be measured based on the temperature difference based on the temperature difference, an external flow meter can be used. It is possible to measure the flow rate of the gas to be heated with a relatively simple configuration in which only a temperature sensor is added without the need for a flow path or a bypass.
However, unlike a thermal flow meter that heats with a relatively small amount of heat exclusively for flow measurement, in a gas heater whose main purpose is to heat a gas and which raises the temperature, for example, by several hundreds of degrees, with a relatively large amount of heat. Since the amount of heat radiation from the surface of the device to the outside is large and the amount of heat radiation itself also changes depending on the temperature (external temperature) of the atmosphere in which the device is installed, it is difficult to ensure measurement accuracy.
SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to provide a gas heater and a method of manufacturing the gas heater that can accurately measure the flow rate of high-temperature gas with a simple configuration.

The present invention solves the above-mentioned problems by the following solutions.
The invention according to claim 1 is a gas flow path through which the gas to be heated passes, a heater provided in the gas flow path, and the temperature of the gas to be heated on the upstream side and the downstream side of the heater in the gas flow path. The flow rate of the gas to be heated is determined based on the difference between the temperatures detected by the upstream temperature detecting means and the downstream temperature detecting means, the upstream temperature detecting means and the downstream temperature detecting means, and the output of the heater. A gas heater comprising a flow rate calculating means for calculating, comprising: an outside air temperature detecting means for detecting a temperature around the gas heater, the flow rate calculating means comprising the upstream side temperature detecting means, the downstream side temperature The gas heater according to the present invention is characterized in that the flow rate is corrected according to the heat release amount calculated based on the detection temperature of the detection means and the outside air temperature detection means.
According to this, even if the gas heater has a large amount of heat generated by the heater and the amount of heat released to the outside, the gas to be heated can be corrected by correcting the flow rate according to the amount of heat release obtained from the detected temperature of each temperature detecting means. Flow rate can be accurately measured.
In addition, by providing a temperature detection means and a calculation means to an existing gas heater, a flow rate measuring function can be added, and the structure of the prior art provided with a single flowmeter outside the gas heater. It is possible to simplify, compact the installation space, and reduce weight and cost.
In addition, it is easy to secure durability such as heat resistance and corrosion resistance.

In the second aspect of the present invention, the flow rate calculating means may calculate in advance the difference between the average value of temperatures detected by the upstream temperature detecting means and the downstream temperature detecting means and the detected temperature of the outside air detecting means. The gas heater according to claim 1, wherein the heat release amount is calculated by multiplying a set constant.
According to this, the above-described effect can be reliably obtained by a relatively light computational load.
The invention according to claim 3 is the gas heater according to claim 1 or 2, wherein the gas to be heated is steam, and the heater heats saturated steam to generate superheated steam. is there.
According to this, the outlet temperature becomes a high temperature of, for example, about 500 ° C., and the flow rate of the superheated steam which is difficult to measure by a single flowmeter can be appropriately measured.

The invention according to claim 4 is a temperature difference between the heated gas on the upstream side and the downstream side of the heater in a gas heater having a gas flow path through which the heated gas passes and in which a heater is provided; A method of measuring the flow rate of a gas heater, which calculates the flow rate of the gas to be heated from the output, wherein the temperature around the gas heater is detected, the temperature on the upstream side and the downstream side of the heater, and the temperature of the ambient And correcting the flow rate according to the amount of heat release calculated based on the flow rate measurement method of the gas heater.
The invention according to claim 5 is characterized in that the heat radiation amount is obtained by multiplying the difference between the average temperature of the gas to be heated upstream and downstream of the heater and the ambient temperature by a preset constant. It is a flow rate measuring method of a gas heater according to claim 4, characterized by calculating.
The invention according to claim 6 is the gas heater according to claim 4 or claim 5, wherein the gas to be heated is steam, and the heater heats saturated steam to generate superheated steam. It is a flow measurement method.
Also in each of these inventions, substantially the same effect as each invention of the gas heater described above can be obtained.

  As described above, according to the present invention, it is possible to provide a gas heater and a method of manufacturing the gas heater capable of accurately measuring the flow rate of high-temperature gas with a simple configuration.

It is a figure which shows the structure of Example 1 of the gas heater to which this invention is applied. It is a graph which shows an example of transition of the flow volume measured (calculated) by the gas heater of Example 1, and the flow volume measured using the flowmeter. It is a figure which shows the structure of Example 2 of the gas heater to which this invention is applied.

  The present invention provides a gas heater capable of accurately measuring the flow rate of a high-temperature gas with a simple configuration and a method for producing the gas heater, the heated gas on the upstream side and the downstream side of the heater in the gas heater The mass flow rate of the gas to be heated is calculated based on the temperature difference of the heater and the output of the heater (heat generation amount), and the average value of the temperature of the gas to be heated on the upstream side and downstream side of the heater The problem is solved by correcting the mass flow rate using the amount of heat release calculated by multiplying the difference of and the predetermined constant.

Hereinafter, a first embodiment of a gas heater and a flow rate measuring method of the gas heater to which the present invention is applied will be described.
FIG. 1 is a view showing the configuration of a gas heater according to a first embodiment.
The gas heater 1 includes an inner cylinder 10, a heater 20, an outer cylinder 30, a heat insulating material 40, an upstream temperature sensor 50, a downstream temperature sensor 60, an outside air temperature sensor 70, a calculation unit 100, and the like. .

The inner cylinder 10 is a cylindrical pipe (gas passage) through which the gas to be heated flows.
The inner cylinder 10 is formed of, for example, a stainless steel alloy in a tube shape, and is configured to ensure sufficient heat resistance and corrosion resistance even if the gas to be heated is, for example, superheated steam of about 500 ° C.
In the inner cylinder 10, for example, saturated steam at about 100 ° C. generated by a boiler not shown is introduced from the upstream end.
The saturated steam is heated by the heater 20 inside the inner cylinder 10, and becomes, for example, superheated steam of about 300 to 500 ° C. and flows out from the downstream end.

  At the upstream end and the downstream end of the inner cylinder 10, attachments 11 and 12 used for connection with an external pipe are respectively provided.

The heater 20 is a heating element that heats the gas to be heated inside the inner cylinder 10 by heating the inner cylinder 10 from the outside.
The heater 20 is, for example, a sheathed heater wound so as to be pressure-bonded to the outer peripheral surface portion in the middle portion of the inner cylinder 10.
The heater 20 generates heat when power is supplied from the heater power supply 21 to the built-in resistance wire.
The heater 20 has an output of, for example, about 3000 to 4000 W, and has a capability of converting, for example, saturated steam of about 100 to 110 ° C. of about 10 kg / h into superheated steam of 500 ° C. or more. In addition, it has the ability to convert saturated water vapor at about 100 to 110 ° C. at about 20 kg / h into superheated water vapor at 300 ° C. or more.
The heater power supply 21 is a voltage variable power supply, and is configured to transmit the power supplied to the heater 20 to the arithmetic device 100.

The outer cylinder 30 is a cylindrical member provided on the outer diameter side of the area around which the heater 20 is wound in the longitudinal direction (axial direction) of the inner cylinder 10.
The outer cylinder 30 is disposed substantially concentrically with the inner cylinder 10.
The inner circumferential surface of the outer cylinder 30 is disposed to face the heater 20 at a distance.

The upstream and downstream ends of the outer cylinder 30 are substantially closed by the end faces 31 and 32.
The end faces 31 and 32 are flat disk-like members formed along a plane orthogonal to the central axis of the outer cylinder 30, and an opening into which the inner cylinder 10 is inserted is formed at the central portion.
The outer cylinder 30 and the end faces 31 and 32 are made of, for example, a stainless-based alloy.

  The heat insulating material 40 is filled on the inner diameter side of the outer cylinder 30 and suppresses the amount of heat transfer from the inner cylinder 10 and the heater 20 to the outer cylinder 30.

The upstream temperature sensor 50 detects the temperature (the temperature before heating by the heater 20) of the gas to be heated which passes through the inner cylinder 10 between the attachment 11 on the upstream side (inlet side) and the end face 31. is there.
The downstream temperature sensor 60 detects the temperature (the temperature after heating by the heater 20) of the gas to be heated passing through the inner cylinder 10 between the attachment 12 on the downstream side (outlet side) and the end surface 32. is there.
The outside air temperature sensor 70 detects the temperature of the surrounding atmosphere (outside air temperature) in the vicinity of the outer peripheral surface of the outer cylinder 30.
For example, a sheath thermocouple sensor can be used as the upstream temperature sensor 50, the downstream temperature sensor 60, and the outside air temperature sensor 70.

Arithmetic device 100 passes the inside of inner cylinder 10 based on the output of heater power supply 21 and the detected temperatures of upstream temperature sensor 50, downstream temperature sensor 60, and outside air temperature sensor 70 (e.g., steam) To calculate the mass flow rate of
The arithmetic unit 100 is configured to have, for example, an information processing unit such as a CPU, a storage unit such as a RAM, a ROM, and an HDD, an input / output interface, a bus connecting these, and the like.

ここで、
Ｑ：ヒータ２０の発熱量（ｋｃａｌ／ｈ）
Ｑ_ｌｏｓｓ：外筒３０等から外部への放熱量（ｋｃａｌ／ｈ）
Ｃ_ｐ：被加熱気体の定圧比熱（ｋｃａｌ／ｋｇ・℃）
Ｔ１：上流側温度センサ５０の検出温度（℃）
Ｔ２：下流側温度センサ６０の検出温度（℃） In the gas heater 1 of the first embodiment, the computing device 100 can calculate the mass flow rate G (kg / h) according to the following equation 1.

here,
Q: Heating value of the heater 20 (kcal / h)
Q _loss : Heat dissipation from the outer cylinder 30 to the outside (kcal / h)
C _p : Constant pressure specific heat of the gas to be heated (kcal / kg · ° C)
T1: Detection temperature of upstream temperature sensor 50 (° C.)
T2: Detection temperature of downstream temperature sensor 60 (° C.)

Here, the heat _release amount Q _loss is obtained by the following equation 2.

Q _loss = K (Tm-Ta) (Equation 2)

K is generally expressed by the product of the surface area to dissipate heat and the heat passing rate, and differs depending on the adiabatic condition of the gas heater 1 (heat conductivity of each member through which heat passes, thickness, etc.) and the type of gas to be heated .
If the configuration of the gas heater 1 and the type of the gas to be heated are the same, it is possible to use an approximate value experimentally obtained as K.
In general, K changes according to the change of G depending on the type of gas and the adiabatic state.
In this case, assuming that K = aG + b (a, b: constant), Q _loss in Expression 2 is expressed by Expression 3 below. K obtained here is obtained by approximating a and b experimentally, and equation 3 is an example of the approximate equation.

Q _loss = (aG + b) (Tm-Ta) (Equation 3)

Substituting the equation 3 into the equation 1 and rearranging, the following equation 4 is obtained.

Further, Tm is the average temperature of the gas to be heated determined by the following equation 5.

Tm = (T1-T2) / 2 (Equation 5)

Hereinafter, the result of flow rate measurement (calculation) by the gas heater 1 of the first embodiment using the above-mentioned formula is compared with the result of flow rate measurement by a single flow meter provided outside.
FIG. 2 is a graph showing an example of transition of the flow rate measured (calculated) by the gas heater 1 of the first embodiment and the flow rate measured using a flow meter.
The horizontal axis shows time, and the vertical axis shows the flow rate and the temperature difference between the upstream side and the downstream side.
In FIG. 2, the flow rate measured by the single flowmeter is indicated by a solid line, the flow rate calculated by the arithmetic unit 100 is indicated by a broken line, and the temperature difference between the detection temperature of the upstream temperature sensor 50 and the detection temperature of the downstream temperature sensor 60 is indicated by It is illustrated.
As shown in FIG. 2, the calculation result of the first embodiment substantially matches the measurement result of the single flow meter.

Also, Table 1 shows the results of measurement by shaking the flow rate to a plurality of levels.
As shown in Table 1, the error between the measured value of the flow meter and the calculation result of Example 1 is at most about 12% or less, and even if a single flow meter is not provided, sufficient measurement accuracy may be obtained depending on the application. It can be seen that it can be secured.
The error shown in Table 1 indicates the maximum error that may occur between the measured flow rate and the calculation result of Example 1 from the measurement result.

As described above, according to the first embodiment, the following effects can be obtained.
(1) The heating purpose of the gas is mainly used for the purpose such as heating of the gas to the thing giving a minute calorific value exclusively for measurement like the existing thermal type flow meter, for example, and the calorific value of the heater 20 and the heat radiation to the outside Even with the extremely large gas heater 1, the flow rate of the vapor which is the gas to be heated can be accurately measured by reflecting the influence of heat radiation to the outside.
Further, by providing each temperature sensor 50, 60, 70 and the arithmetic unit 100 to an existing gas heater, the flow rate measuring function can be easily added, and a single flowmeter is provided outside the gas heater. Compared to the prior art, the structure can be simplified, the installation space can be compact, and the weight and the cost can be reduced.
(2) The arithmetic unit 100 uses the heat _release amount Q _loss calculated by multiplying the difference between the average value of the temperatures detected by the upstream temperature sensor 50 and the downstream temperature sensor 60 and the temperature detected by the outside air temperature sensor 70 by a constant. By correcting the flow rate G, the above-described effect can be reliably obtained by a light computational load.
(3) It is easy to ensure heat resistance, corrosion resistance, etc. compared to the prior art in which a single flow meter is provided, for example, even superheated steam having a high temperature of about 500 ° C and difficult to measure with a single flow meter The flow rate can be measured.

Next, a second embodiment of the gas heater to which the present invention is applied will be described.
About the part which is substantially common with Example 1 mentioned above, the same numerals are attached, explanation is omitted, and difference is mainly explained.
FIG. 3 is a diagram showing the configuration of the gas heater of the second embodiment.
As shown in FIG. 3, in the second embodiment, a heater 20 in which a heating wire such as a nichrome wire is wound in a coil shape and exposed is used.
The coil-shaped heat generating portion in the heater 20 is disposed on the inner diameter side of the inner cylinder 10 so as to be substantially concentric with the inner cylinder 10, for example.
In the second embodiment described above, in addition to the effects substantially similar to the effects of the first embodiment described above, the heating performance is improved by direct contact of the heater 20 with the gas to be heated, and to the outside of the apparatus It is possible to improve the flow rate measurement accuracy by suppressing the heat radiation of

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, which are also within the technical scope of the present invention.
(1) The shape, structure, material, manufacturing method, arrangement, and the like of each member constituting the gas heater are not limited to the above-described embodiment, and can be appropriately changed.
For example, the heater may be disposed outside the inner cylinder, and the gas to be heated may be in contact with the inner cylinder heated by the heater.
Also, for example, the heat insulation structure of the gas heater is not limited to the one filled with the heat insulating material as in the embodiment, but may be provided with a vacuum layer or the like.
(2) Each equation described in the embodiment is an example and can be changed as appropriate. For example, other correction terms may be added.
(3) In the embodiment, the gas to be heated is water vapor as an example, but other vapors and various other gases can be used as the gas to be heated.

Reference Signs List 1 gas heater 10 inner cylinder 11, 12 attachment 20 sheathed heater 21 heater power source 30 outer cylinder 31, 32 end surface 40 heat insulator 50 upstream temperature sensor 60 downstream temperature sensor 70 outside air temperature sensor 100 calculation means

Claims (6)

A gas passage through which the gas to be heated passes;
A heater provided in the gas flow path;
Upstream temperature detection means and downstream temperature detection means for respectively measuring the temperature of the gas to be heated on the upstream side and downstream side of the heater in the gas flow path;
A flow rate calculating means for calculating the flow rate of the gas to be heated based on the difference between the temperatures detected by the upstream temperature detecting means and the downstream temperature detecting means and the output of the heater;
An outside air temperature detection means for detecting the temperature around the gas heater,
The flow rate calculating means corrects the flow rate according to the amount of heat release calculated based on the temperatures detected by the upstream temperature detecting means, the downstream temperature detecting means, and the outside air temperature detecting means. Heater. The flow rate calculating unit multiplies a difference between an average value of temperatures detected by the upstream temperature detecting unit and the downstream temperature detecting unit and a temperature detected by the outside air detecting unit by a preset constant. The gas heater according to claim 1, wherein the heat release amount is calculated. The gas heater according to claim 1 or 2, wherein the gas to be heated is steam, and the heater heats saturated steam to generate superheated steam. The flow rate of the to-be-heated gas from the temperature difference between the to-be-heated gas on the upstream side and the downstream side of the heater in a gas heater having a gas flow path in which the to-be-heated gas passes and the heater is provided A flow rate measurement method of a gas heater for calculating
The temperature around the gas heater is detected, and the flow rate is corrected according to the amount of heat release calculated based on the temperatures on the upstream and downstream sides of the heater and the temperature around the heater. How to measure the flow rate of a gas heater. The heat dissipation amount is calculated by multiplying a difference between an average value of the temperatures of the gas to be heated upstream and downstream of the heater and the ambient temperature by a preset constant. The flow rate measuring method of the gas heater according to item 4. The flow rate measurement method of a gas heater according to claim 4 or 5, wherein the gas to be heated is steam, and the heater heats saturated steam to generate superheated steam.

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